Exam #2

Question 1

the peripheral nervous system is comprised of both the ______ division and the ____ division

Answer 1

afferent, efferent

Question 2

the afferent division of the peripheral nervous system contains ___ stimuli and ____ stimuli

Answer 2

sensory, visceral

Question 3

the efferent division of the peripheral nervous system is comprised of the _____ nervous system and the ____ nervous system

Answer 3

somatic, autonomic

Question 4

the somatic nervous system controls _____ neurons, which controls ______

Answer 4

motor, skeletal

Question 5

the autonomic nervous system has 2 branches, what are they?

Answer 5

sympathetic and parasympathetic

Question 6

both the sympathetic and the parasympathetic nervous systems control _____ muscle, _____ muscle, and ____

Answer 6

smooth, cardiac, glands

Question 7

the autonomic nervous system innervates organs whose functions are not usually what?

Answer 7

under voluntary control

Question 8

why are reflexes important for autonomic control

Answer 8

• may involve sensory info causing changes in autonomic output, in order to return to a setpoint (negative feedback)
• may elicit feedforward responses

Question 9

sensory information from the autonomic nervous system may be processed within which 3 structures

Answer 9

• hypothalamus
• limbic system
• spinal cord

Question 10

what are the 2 effectors of the autonomic nervous system

Answer 10

visceral organs and blood vessels (also glands)

Question 11

the actions of the autonomic nervous system require conscious control

True or False?

Answer 11

false, its actions are usually involuntary (without conscious intent or awareness)
-although, using biofeedback techniques it may be possible to learn to exert control over the ANS

Question 12

are there some cases where the autonomic nervous system are activated by conscious control?

Answer 12

yes

• ex: micturation (peeing)
• the ability to not pee is an activation of the sympathetic branch

Question 13

most visceral effectors need the ANS to function

True or False?

Answer 13

false, most visceral effectors do not need the ANS to function, only adjust their activity to match to body’s needs to maintain homeostasis (heart rate for example)

Question 14

general autonomic nerve pathwat

Answer 14

-extends from CNS to an innervated organ

• 2-neuron chain
• preganglionic fiber (synapses with the cell body of second neuron)
• postganglionic fiber (innervated the effector organ or tissue)

Question 15

in a general autonomic nerve pathway, the preganglionic fiber has a cell body ______ the CNS, whereas the postganglionic fiber has a cell body ____ the CNS

Answer 15

within, outside

Question 16

what is a ganglion

Answer 16

a mass or a group of neuronal cell bodies that form a knot-like mass of tissue

Question 17

in the sympathetic branch of the autonomic nervous system, cell bodies of the preganglionic fibers originate from where?

Answer 17

originate in thoracic and lumbar regions of the spinal cord

Question 18

in the sympathetic branch of the autonomic nervous system, the preganglionic fibers are ______ relative to the postganglionic fibers which are ____

Answer 18

short, long

Question 19

what are the 3 possible things that axons from the sympathetic branch of the autonomic nervous system do after they exit the spinal cord?

Answer 19

1) make a synapse in a sympathetic chain ganglion
2) pass through sympathetic chain ganglia (SCG) and synapse in the adrenal medulla
3) pass through the SCG and synapse in a collateral ganglion

Question 20

in the sympathetic division of the autonomic nervous system, preganglionic fibers release _____ whereas most postganglionic fibers release _____

Answer 20

acetylcholine (ACh), norepinephrine (NE)

Question 21

it is said that the adrenal medulla is a modified sympathetic ganglion. Why is this?

Answer 21

in early development, groups of neurons leave the spinal cord to form postganglionic cells, small group of these instead of becoming postganglionic cells, migrate into and within the adrenal tissue

Question 22

sympathetic neurons secrete ___% epinephrine and ___% norepinephrine

Answer 22

85, 15

Question 23

in the parasympathetic division of the autonomic nervous system, fibers originate from the _____

Answer 23

cranial and sacral areas of the CNS

Question 24

in the parasympathetic division of the autonomic nervous system, preganglionic fibers are relatively _____ compared to the postganglionic fibers which are ____

Answer 24

long, very short

Question 25

in the parasympathetic division of the autonomic nervous system, the preganglionic fibers release ____ whereas the postganglionic fibers release ____

Answer 25

both acetylcholine (ACh)

Question 26

both in the sympathetic and parasympathetic nervous systems does each postganglionic neuron receive synapses from many preganglionic cells (convergence)

True or False?

Answer 26

true

Question 27

both in sympathetic and parasympathetic divisions of the autonomic nervous system does each preganglionic neuron branch many times to synapse on many different postganglioning neurons at a rate of 1:10 -
1:30 (divergence)

true or false?

Answer 27

false, this only happens in the SNS, the rate of the PNS is 1:4 (lower than SNS)

Question 28

the sympathetic nervous system tends to respond as a unit

True or False?

Answer 28

true

Question 29

the parasympathetic nervous system tends to respond as a unit

true or false?

Answer 29

false, in the parasympathetic nervous system, things like heart rate can be regulated independently of gut or liver, there’s enough individual control

Question 30

4 of the cranial nerves have parasympathetic function, which are they?

Answer 30

• oculomotor nerve: control the lens and the pupil of the eye
• fascial nerve: tear glands, salivary glands, nasal glands
• glossopharyngeal nerve: salivary glands
• vagus nerve: 70-90% of all parasympathetic fibres, innervates the viscera

Question 31

what are some characteristics of the vagus nerve?

Answer 31

• it’s the 10th cranial nerve
• vagus = “wandering”, called this because it innervates basically all viscera
• has many branches
• innervates all organs except the adrenal medulla and some parts of the colon

Question 32

the ____ nerve carries sensory information from most of the viscera

Answer 32

vagus

Question 33

what is the reflex arc of the vagus nerve?

Answer 33

1) the vagus nerve carries sensory info from most of the viscera. many of these sensory afferents project topographically to the nucleus of the solitary tract (abbreviated to NST or NTS), to the brainstem
2) the sensory info is processed within the NTS.
- the NTS may also project axons to higher parts of the brain, hypothalamus and cortex
3) vagus nerve carries efferent information to regulate organ function

Question 34

the receptors between the pre and the post ganglionic cells are usually ______ receptors, whereas the receptors between the postganglionic cell and the target cell are usually _____ receptors

Answer 34

nicotinic, muscarinic

*in the parasympathetic division, sometimes the receptors between the postganglionic cell and target cell are nicotinic

Question 35

which tends to have longer lasting effects: the sympathetic branch of the autonomic nervous system or the parasympathetic branch

Answer 35

sympathetic branch

Question 36

why does the sympathetic nervous system tend to have a longer lasting effect than the parasympathetic nervous system?

Answer 36

1) achetylcholin is quickly broken down by acetycholinesterase
2) norepinephrine is more persistent than ACh. breakdown mechanisms are slower
- NE is transported back into the neuron
- NE is degraded by COMT or MAO
- NE picked up by the blood (where there are no degradative enzymes)

Question 37

which receptors can we find on the target organs of the sympathetic nervous system (NE)?
(hint: “p-dibi”)

Answer 37

• a1 receptors (phospholipase c)
• a2 (decreae cAMP)
• B1 (increase cAMP)
• B2 (both increase and decrease cAMP)
• B3 (increase cAMP)

Question 38

which receptors can we find on target organs in the parasympathetic nervous system (ACh)?

Answer 38

-nicotinic AChR (ligand gated ion channel)

• muscarinic AChR (GPCR):
• M1 (phospholipase c)
• M2 (decrease cAMP)
• M3 (phospholipase c)

Question 39

the sympathetic nervous system activates the ______ to release massive amounts of _____. This second messenger signalling often affects what?

Answer 39

adrenal medulla, epinephrine, ion channels

Question 40

what are the effects of the sympathetic nervous system stimulation on the heart?

Answer 40

increased rate, increased force of contraction (of whole heart)

Question 41

what are the effects of the parasympathetic nervous system stimulation on the heart?

Answer 41

decreased rate, decreased force of contraction (of atria only)

Question 42

what are the effects of the sympathetic nervous system stimulation on the eye?

Answer 42

dilation of pupil

Question 43

what are the effects of the parasympathetic nervous system stimulation on the eye?

Answer 43

constriction of pupil

Question 44

what are the effects of the sympathetic nervous system stimulation on the exocrine pancreas?

Answer 44

inhibition of pancreatic exocrine secretion

Question 45

what are the effects of the parasympathetic nervous system stimulation on the exocrine pancreas?

Answer 45

stimulation of pancreatic exocrine secretion (important for digestion)

Question 46

what are the effects of the sympathetic nervous system stimulation on the salivary glands?

Answer 46

stimulation of small volume of thick saliva rich in mucus

Question 47

what are the effects of the parasympathetic nervous system activation on the salivary glands?

Answer 47

stimulation of large volume of watery saliva rich in enzymes

Question 48

the exocrine pancreas produces which enzymes?

Answer 48

trypsin, pancreatic lipase, and pancreatic amylase

Question 49

what is dual innervation?

Answer 49

most of your internal organs have dual innervation (input from SNS and PNS)
-this is not always balanced (ex: digestive has much more PNS than SNS)

Question 50

the effects of dual innervation are usually antagonistic

True or False?

Answer 50

false, the effects can be antagonistic or complimentary

Question 51

what are some examples of the antagonistic functions of dual innervation?

Answer 51

the heart is innervated by both SNS and PNS

• SNS increases heart rate and force of contraction
• PNS decreases

The iris innervated by both

• SNS innervated the pupillary dilator
• PNS innervates the pupillary constrictor

Question 52

give examples of the complimentary functions of dual innervation

Answer 52

activation of SNS and PNS produce similar results

Salivary glands are innervated by both
-both increase saliva production, but different kinds of saliva (SNS stimulated mucus production; PNS stimulates water, enzyme rich saliva)

Male sexual response, PNS responsible for erection, SNS responsible for ejaculation (point and shoot, memory trick)

Question 53

not all target organs are subject to dual innervation. Which target organs are only innervated by the sympathetic branch?

Answer 53

adrenal medulla, sweat glands, smooth muscle of most blood vessels

Question 54

what are the central nervous system centres that contribute to autonomic regulation?

Answer 54

• limbic system (integration of sensory and emotional response with autonomic output)
• hypothalamus (major control centre for autonomic output; hunger, thirst, thermoregulation, emotions, and sexuality)
• brain stem (gives ride to nuclei of cranial nerves that mediate several autonomic responses)
• spinal cord (autonomic responses as the defecation and micturation reflexes are integrated in the spinal cord)

Question 55

look at figs. 12.3, 12.4, 12.5, 12.8, 12.9, 12.10

Answer 55

page #?

-somewhere between 371-394 or 378-398

Question 56

what are the 3 types of muscle?

Answer 56

• skeletal muscle (make up muscular system; also diaphragm)
• cardiac muscle (found only in the heart)
• smooth muscle (classified in two different ways (striated or unstriated; voluntary or involuntary)

Question 57

which of the 3 types of muscle is multinucleated?

Answer 57

skeletal muscle

Question 58

which of the 3 muscle types is not striated?

Answer 58

smooth muscle

Question 59

which of the 3 types of muscle is stacked end to end?

Answer 59

cardiac muscle

Question 60

which of the 3 types of muscle is compared to an intercalated disc?

Answer 60

cardiac muscle

Question 61

controlled muscle contraction allows for 3 things, what are these things?

Answer 61

• skeletal muscle allows for the movements of joints, limbs and whole body
• smooth muscle and cardiac muscle control propulsion of contents through various hollow organs
• emptying of contents of certain organs to external environment

Question 62

skeletal muscle is controlled by which division of the nervous system? (central or peripheral)

Answer 62

CNS

Question 63

the neurons in skeletal muscle have a cell body in the motor cortex synapse on motor neurons in the _____

Answer 63

spinal cord

Question 64

skeletal muscle: motor neurons with cell bodies in the spinal cord send axons to synapse onto _____

Answer 64

muscle cells (nerve muscle synapse is called a neuromuscular junction (NMJ)

Question 65

the group of muscle cells controlled by a motor neuron is a _____

Answer 65

motor unit

Question 66

___% of axons cross through the medullary pyramids

Answer 66

95

Question 67

in mammals, each muscle cell receives how many synapses?

Answer 67

only one

Question 68

muscles that require fine control have very ______ convergence
ex: muscles of the eye

Answer 68

little

Question 69

muscles that don’t require fine control can have very _____ convergence
ex: rectus femoris

Answer 69

high

Question 70

in mammals, inhibitory synapses on muscle cells are quite frequent

true or false?

Answer 70

false, in mammals, inhibitory synapses on muscle cells do not exist

Question 71

what is the size comparison of an neuromuscular junction synapse (NMJ) compared to a central synapse?

Answer 71

NMJ = 1000 um (squared)

central synapse = 0.05 um (squared)

Question 72

why is the NMJ such a huge synapse?

Answer 72

because the postsynaptic membrane is folded and has a high density of nAChR (niconitic achetylcholine receptors) (hundreds of thousands)
-a.k.a. high density of ligand gated ion channels directly underneath presynaptic terminals

-this causes a massive release of ACh, causes a huge EPSP in the muscle fiber, depolarization will ALWAYS be enough to trigger an action potential (no summation)

Question 73

what is the structure of a skeletal muscle?

Answer 73

muscle consists of a number of muscle fibers lying parallel by connective tissue

one single skeletal muscle is known as a muscle fiber

• multinucleated
• large, elongated, and cylindrically shaped
• fibers usually extend entire length of muscle

Question 74

what is the fluid inside the T-tubules of a skeletal muscle cell?

Answer 74

ECF

Question 75

the T-tubules are a continuation of what?

Answer 75

the cell membrane has holes that lead to the T-tubules

Question 76

the sarcoplasmic reticulum is full of what?

Answer 76

Ca++

Question 77

what determines the length of one sarcomere

Answer 77

from z disc to z disc

Question 78

what is the name of the line in the center of the sarcomere

Answer 78

m-line

Question 79

what is the a-band in a sarcomere

Answer 79

sits between the z discs

Question 80

what is a z disk in a sarcomere

Answer 80

sits between a-bands

Question 81

the thick filaments are in the _____ of a sarcomere and the thin filaments are _____

Answer 81

middle, towards the edges

Question 82

what are the 3 components of the myofibril

Answer 82

actin, myosin, and titin

Question 83

what is the major component of a thick filament?

Answer 83

myosin

Question 84

myosin

Answer 84

protein molecule consisting of two identical subunits shaped like a golf club

• tail ends are intertwined around each other
• globular heads project out at one end

Question 85

what is the orientation of the heads and tails of a myosin molecule?

Answer 85

tails are oriented towards the center of the filament and globular heads protrude outward at regular intervals

Question 86

which part of the myosin filament forms cross bridges between thick and thin filaments?

Answer 86

myosin heads

Question 87

myosin has two important sites that are critical to contractile process, what are they?

Answer 87

• an actin binding site

- a myosin ATPase

Question 88

what is a cross bridge in muscle fiber contractile unit

Answer 88

cross bridge refers to the interaction between myosin and actin molecules (the interaction itself is called a cross bridge)

Question 89

the thick filaments of a muscle contractile unit are made of _____, whereas the thin filaments are made of ____

Answer 89

myosin; actin, tropomyosin, troponin, nebulin, titin

Question 90

primary structural component of thin filaments

Answer 90

actin

Question 91

what are the spherical monomers that assemble into long chains in the actin chain

Answer 91

g-actin monomers

Question 92

each actin molecule has a special binding site for attachment with the _____

Answer 92

myosin head

Question 93

the binding of a myosin head to an actin monomer results in what?

Answer 93

contraction of the muscle fiber

-this interaction is key to produce movement

Question 94

topomyosin

Answer 94

• regulatory protein
• thread-like molecules alongside the groove of the actin spiral
• tropomyosin covers the myosin binding sites

Question 95

which regulatory protein covers the myosin binding sites on the actin molecules?

Answer 95

tropomyosin

Question 96

troponin is made of 3 polypeptide units, what do they bind to?

Answer 96

• one binds to tropomyosin
• one binds to actin
• one binds with Ca++

Question 97

what effects do Ca++ levels have on the effects of troponin on tropomyosin?

Answer 97

• when there’s a low level of Ca++, troponin stabilizes the action of tropomyosin
• when there’s lots of Ca++, troponin pulls tropomyosin out of the way so that the myosin binding site is open

Question 98

describe the action of troponin on muscle contraction

Answer 98

• when not bound to Ca++, troponin stabilizes tropomyosin in blocking position over actin’s cross-bridge binding sites
• when Ca++ binds to toponin, tropomyosin moves away from blocking position
• with tropomyosin out of the way, actin and myosin bind, interact at cross-bridges
• muscle contraction occurs

Question 99

titin

Answer 99

• structural protein
• giant elastic protein (one of the biggest in mammalian genome)
• joins m-lines to z-lines at opposite ends of the sarcomere

Question 100

what are the 2 important roles of titin?

Answer 100

• help stabilize position of thick filaments in relation to thin filaments
• improves muscle’s elasticity

Question 101

nebulin

Answer 101

aligns actin filaments

Question 102

the muscle ______ when actin and myosin slide past each other

Answer 102

shortens

Question 103

when a muscle contracts, the A-band gets smaller along with the length of the filaments

true or false?

Answer 103

false,
the size of the A-band never changes length and neither does the length of the thin filaments
-what changes is the amount of overlap between the two

Question 104

what structures shorten when a muscle contracts?

Answer 104

the H-zone and the I-band both shorten

Question 105

what is the role of Ca++ in a muscle cell to be able to generate tension?

Answer 105

1) Ca++ levels increase in the cytosol
2) Ca++ binds to troponin (TN)
3) TN-Ca++ complex pulls tropomyosin away from actin’s myosin-binding site
4) myosin binds strongly to actin and completes power stroke
5) actin filament moves

Question 106

what initiates the contraction of a muscle cell?

Answer 106

Ca++

Question 107

in its relaxed state, the myosin head is ______, and ______ partially blocks the binding site on actin, myosin is weakly bound to actin

Answer 107

cocked, tropomyosin

Question 108

power stroke

Answer 108

cross bridge bends, pulling thin myofilament inward

Question 109

the phase of muscle cell contraction where the cross bridge detaches at the end of the power stroke and returns to its original conformation

Answer 109

detachment

Question 110

but these in order from first to last (phases of muscle cell contraction)

a) detachment: cross bridge detaches at the end of power stroke and returns to original position
b) binding: cross bridge binds to more distal actin molecule
c) binding: myosin cross bridge binds to actin molecule
d) power stroke: cross bridge bends, pulling thin myofilament inward

Answer 110

c, d, a, b

Question 111

actin and myosin contract along with the contraction of a muscle cell

true or false?

Answer 111

false, actin and myosin do not contract

-myosin is properly called a motor protein: a protein that hydrolyzes ATP to convert chemical energy to carry out mechanical work

Question 112

what is a motor protein?

Answer 112

a protein that hydrolyzes ATP to convert chemical energy to carry out mechanical work

ex: myosin

Question 113

look at fig 12.9 and remember cycle

Answer 113

p.?

Question 114

explain the 4 steps of the contraction cycle of a muscle cell

Answer 114

1) ATP binds to myosin. myosin releases actin
2) myosin hydrolyzes ATP. energy from ATP rotates the myosin head to the cocked position. myosin binds weakly to actin
3) power stroke begins when tropomyosin moves off the binding site (there is a rapid increase of intracellular Ca++ at this point)
4) myosin releases ADP at the end of the power stroke

Question 115

the sarcoplasmic reticulum is closely related to the T-tubules and has a high [ ] of Ca++

true or false?

Answer 115

true

Question 116

how does the sarcoplasmic reticulum have such a high [ ] of Ca++?

Answer 116

SR has powerful Ca++ATPase transporter
-uses ATP to pump Ca++ from cytoplasm into SR

SR also has Ca++ binding protein called calquestrin
-help maintain high [Ca++]

Question 117

T-tubules run ______ from the surface of the muscle cell membrane into central portions of the muscle fiber

Answer 117

perpendicular

Question 118

T-tubules are aligned on the edges of the ____-band

Answer 118

A

thick filaments, myosin

Question 119

an action potential on the surface of a membrane also invade T-tubules

true or false?

Answer 119

true

Question 120

what is the effect of the spread of an action potential down a T-tubule on the sarcoplasmic reticulum?

Answer 120

• the spread of action potential down a T-tubule triggers the release of Ca++ from the sarcoplamic reticulum into the cytosol
• this rapid increase is what’s responsible for binding of actin and myosin

Question 121

an action potential in a t-tubule opens the voltage-gated Ca++ channels (dihydropyridine receptor) _____ and opens the ryanodine receptors on the sarcoplasmic reticulum _____. This is because the ____ of the ryanodine receptor is physically attached to the voltage gated Ca++ channel of the t-tubule

Answer 121

directly, indirectly, foot

Question 122

the opening of the ryanodine receptor on the sarcoplasmic reticulum allows a massive flood of Ca++ into the cytoplasm via _____

Answer 122

because of the [ ] gradient

Question 123

what are the two purposes of the voltage gated Ca++ channel (dihydropyridine receptor) in the T-tubules?

Answer 123

1) to act as a voltage sensor that can open the ryanodine receptor
2) lets in small amount of Ca++, contributes to the opening of RyR (ryanodine receptor)

Question 124

thinking about what we’ve learned in the whole semester, explain the process of initiation of muscle action potential and excitation contraction coupling

Answer 124

1) an AP invades the presynaptic terminal and causes release of ACh
2) ACh binds to the receptor, allows entry of Na+, causes EPSP large enough to trigger AP
3) the AP invades the T-tubule system
4) the AP causes the DHP (receptors of t-tubules) to open, and in turn, open the RyR channel. this causes a massive release of Ca++, and increase in intercellular Ca++ [ ]
5) Ca++ binds troponin. troponin pulls tropomyosin away from myosin binding site on actin protein
6) power stroke
7) actin filaments slide towards centre of the sarcomere
8) free Ca++ pumped back into SR

Question 125

rigor mortis

Answer 125

• 3-4 hours after death, peak at 12 hours
• after deatch, intracellular Ca++ rises (leaks out of SR)
• Ca++ allows troponin-tropomyosin complex to move aside and allow myosin cross bridges to bind actin
• but ATP is required to separate myosin from actin, dead cells can’t produce ATP, so once bound, the cross bridge can’t detach
• rigor mortis subsides when enzymes start to break down myosin heads

Question 126

explain the process that leads to the relaxation of a muscle

Answer 126

• AP stop ariving at NMJ
• ACh dissociates from AChR, gets degraded
• Ca++ ATPase pumps free Ca++ back into SR
• Ca++ dissociates from troponin, pumped bacj into SR
• tropomyosin moves back into position, blocking cross bridge binding sites
• muscle ceases to maintain tension
• actin and myosin slip past each other (pulled by titin, pulled by antagonistic muscle)

Question 127

what is myasthenia gravis

Answer 127

• autoimmune disorder
• antibodies block ACh binding sites on skeletal muscle
• binding causes damage to tissue of muscle cell
• not enough ACh is bound to create action potentials anymore

Question 128

what are common symptoms of myasthenia gravis?

Answer 128

• a drooping eyelid
• blurred or double vision
• slurred speech
• difficulty chewing and swallowing
• weakness in the arms and legs
• chronic muscle fatigue
• difficulty breathing

i.e. muscle weakness

Question 129

what are some treatments for myasthenia gravis?

Answer 129

• anticholenesterase treatment (drugs that inhibit ACh-esterase within the NMJ)
• these allow ACh to remain in the NMJ longer
• ex: pyridostigmine (degraded over 3-6 hours)
• neostigmine (degrades over 1 hour)

other treatments:

• immunosuppression
• surgery (Ex: 10-15% of people with this have tumors, if the tumour is removed, can help symptoms)

Question 130

what are the contraction-relaxation steps that require ATP

Answer 130

• splitting of ATP by myosin ATPase for power stroke
• active transport of Ca++ back into SR
• fuel Na+/K+ ATPase

-so, constant source of energy is needed

Question 131

what are the 3 energy sources for muscle contraction?

Answer 131

1) creatine phosphate: first energy storehouse tapped at onset of contractile activity
2) oxidative phosphorylation: takes place within muscle mitochondria if sufficient O2 is present
3) glycolysis: support anaerobic or high-intensity exercise (last resort)

Question 132

creatine phosphate

Answer 132

• during times of rest when ATP demand is low, muscle stores energy in the form of creatine phosphate
• first store of energy tapped to fuel muscle contraction
• provides 4-5 times the energy of stored ATP
• limited supply (only a few minutes)

Question 133

how does creatine phosphate work?

Answer 133

at rest, there’s lots of ATP around, creatine takes ATP and phosphate to create creatine phosphate
-good storage place for this high energy bonds

Question 134

oxidative phosphorylation

Answer 134

The process that provides energy during light to moderate exercise

• uses stores of glycogen in muscle (30 min)
• good yield of ATP
• aerobic exercise
• adequate supply of oxygen

To maintain adequate oxygen

• increase ventilation
• increase heart rate and force of contraction
• dilate skeletal blood vessels

Question 135

glycolysis

Answer 135

• primary source of ATP when oxygen supply is limited (during intense exercise)
• rapid supply of ATP (only a few enzymes involved)
• very low ATP yield (only 2 per glucose molecule; lactic acid, acidifies muscle and contributes to fatigue)
• duration of anaerobic glycolysis is limited

Question 136

what causes muscle fatigue?

Answer 136

Central fatigue

• CNS (above psychological aspects; could be decreased output of motor neurons from cortex)
• psychological

Peripheral fatigue

• decrease in ACh
• receptor desensitization
• changes in RMP (because of extracellular K+)
• impaired Ca++ release
• pH
• others…

the lack of ATP is not thought to be a factor***

Question 137

the action potential and the contraction of a skeletal muscle happen almost simultaneously

true or false?

Answer 137

false, there is a latency period from when the action potential is generated to the time the muscle contracts (approx. 2 ms to generate action potential in motor neuron and skeletal muscle, 10-100 ms to contract muscle)

Question 138

the total amount of tension generate by s skeletal muscle is dependent on the _____ of the motor neuron

Answer 138

firing frequency

-can be single twitch or summation

Question 139

what is the difference between unfused tetanus and complete tetanus in a skeletal muscle?

Answer 139

complete tetanus is not able to generate the peak amount of tension that the unfused tetanus can reach

Question 140

in _____ tetanus, fatigue causes the muscle to lose tension despite continuing stimuli

Answer 140

complete

Question 141

what are 2 different views on what leads a muscle to reach its peak amount of tension?

Answer 141

• some people think intracellular Ca++ reaches its maximum (saturates) after first action potential (summation and tetanus develop because of sustained elevation of increased Ca++ allows greater exposure of actin bindings sites and therefore maximizes interaction with myosin (effect is time dependent)
• other people think it takes several APs to increase intracellular Ca++ enough to saturate actin’s myosin binding sites

Question 142

takes several AP to cause generation of maximal tension

true or false

Answer 142

true

Question 143

if there is less overlap between the thick and thin filaments, what effects does this have on a muscle’s ability to generate tension?

Answer 143

this reduces the number of possible interaction sites, lessening tension

Question 144

by providing more overlap between the thick and thin filaments, what effects does this have on a muscle’s ability to generate tension?

Answer 144

• the muscle fiber is pushed together so much that the myosin is interacting with the z-discs, and actin molecules are overlapping
• crowding molecules leads to insufficient interaction between binding sites and myosin heads = less tension

Question 145

what are the 3 types of motor units found in most mammals

Answer 145

• slow twitch oxidative (red muscle)
• fast twitch oxidative-glycolytic (red muscle)
• fast twitch glycolytic (white muscle)

Question 146

in turkey, muscle fiber groups are ____, whereas in mammals, muscle fiber groups are _____

Answer 146

together, interspersed

Question 147

slow twitch oxidative motor unit (slow fatigue resistant)

Answer 147

• small amounts of tension (compared to other two muscle types), slowly
• capable of generating tension for long periods of time without running down energy stores
• large number of mitochondria
• small fibres
• well vascularized, myoglobin (to facilitate oxygen transfer from blood (presence of myoglobin is what makes the muscle dark

Question 148

fast twitch oxidative-glycolytic (fast fatigue resistant)

Answer 148

• generate a lot of tension, moderately fast
• somewhat resistant to fatigue
• moderate number of mitochondria
• fibres are larger than slow twitch muscles

Question 149

fast twitch glycolytic (fast fatiguable)

Answer 149

• white muscle
• generate the most tension
• fatigue rapidly
• few mitochondria (anaerobic catabolism)
• fibres are larger than slow twitch

Question 150

both fast twitch muscles are able to generate their maximum amount of tension within ___ ms, while slow twitch muscle are able to generate their max amount of tension within ___ ms

Answer 150

25, 50

Question 151

one muscle may have many motor units of different fiber types

true or false?

Answer 151

true

Question 152

what are the first motor units recruited?

Answer 152

• slow twitch fatigue resistant (red oxidative) (weakest are recruited first)
• each motor unit has only a few fibres
• small motor neuron
• takes much less synaptic input to put these motor neurons to threshold

Question 153

what are the 2nd motor units recruited?

Answer 153

• motor units that include fast fatigue resistant fibres

- these motor neurons are slightly larger

Question 154

what are the 3rd and last motor units recruited?

Answer 154

• fast fatiguable (=fast twitch glycolytic, white muscle)

- the largest motor unit, includes most fibres

Question 155

what is the size principle in the recruitment of motor units?

Answer 155

slow twitch is activated first (smallest), then fast fatigue resistant, then fast fatigable (largest)

Question 156

one motor neuron can innervate more than one type of muscle

true or false?

Answer 156

false

Question 157

general characteristics of cardiac muscle cells

Answer 157

• interconnected by intercalated discs and form functional syncytia
• within intercalated discs there are two kinds of membrane junctions (desmosomes and gap junctions)

Question 158

what are the 3 types of cardiac muscle cells

Answer 158

1) myocardial autorhythmic cells
2) myocardial contractile cells (working cells)
3) conducting cells

Question 159

cardiac muscle: myocardial autorhythmic cells

Answer 159

• initiate and maintain electrical activity in the heart (generate their own action potentials without electrical stimulus)
• do not contract
• have gap junctions

Question 160

cardiac muscle: myocardial contractile cells (working cells)

Answer 160

• 99% of cardiac muscle cells
• contractile, MUSCLE part of the heart, do mechanical work of pumping (either in the ventricle or the atrium)
• joined electrically by gap junctions

Question 161

cardiac muscle: conducting cells

Answer 161

• carry electrical signals from the pacemakers to the contractile cells
• gap junctions

Question 162

where does the cardiac impulse originate?

Answer 162

at the SA node (sinal atrial node)

Question 163

explain the process of electrical conduction in the heart

Answer 163

• cardiac impluse originates at SA node
• action potential spreads throughout right and left atria
• impulse passes from atria into ventricles through AV node (only point of electrical contact between the chambers)
• action potential briefly delayed at AV node (ensures atrial contraction precedes ventricular contraction to allow complete ventricular filing)
• impulse travels rapidly down interventricular septum by means of bundle of His
• impulse rapidly disperses throughout the myocardium by means of Purkinje fibers
• rest of ventricular cells activated by cell to cell spread of impulse through gap junctions

Question 164

what kind of cells initiate action potentials in cardiac cells?

Answer 164

autorhythmic cells

Question 165

what is the resting membrane potential of a cardiac muscle cell?

Answer 165

there is no real resting membrane potential, it is rather a spontaneous conduction of action potentials by the autorhythmic cells

Question 166

what is the pacemaker potential

Answer 166

membrane slowly depolarizes “drifts” to threshold, initiate action potential, membrane repolarizes to -60 mV (cardiac cell)

Question 167

autorhythmic cells: I(f)

Answer 167

a Na+ current

Question 168

autorhythmic cells: ICa(T)

Answer 168

fast calcium current

Question 169

autorhythmic cells: ICa(L)

Answer 169

slow Ca++ current

Question 170

in a skeletal muscle cell, ____ flows inside the cell during an action potential, in a cardiac muscle cell, ____ is used instead

Answer 170

Na+, Ca++

Question 171

explain the steps of an action potential in contractile cells of a cardiac muscle

Answer 171

0) Na+ channels open slowly
1) Na+ channels inactivate once AP reaches its peak
- rapid depolarization

2) Ca++ channels open; fast K+ channels close
3) Ca++ channels close; slow K+ channels open
- rapid partially early repolarization, prolonged period of slow repolarization (plateau phase)

4) cell goes back to resting membrane potential
- rapid final repolarization phase

**there is no hyperpolarization afterwards

** also, membrane potential is more negative (-80mV)

Question 172

why is the repolarization phase of cardiac contraction cells so long?

Answer 172

• plateau is primarily due to the activation of slow L-type Ca++ channels
• this long action potential ensures adequate ejection of blood

Question 173

how does the long action potential of contractile cells avoid tetanus?

Answer 173

long AP causes long refractory period and long contraction

-this refractory period overlaps the tension curve

Question 174

refractory period of skeletal vs cardiac muscle cell

Answer 174

1) skeletal muscle fast twitch fiber: the refractory period is very short compared with the amount of time required for the development of tension
- skeletal muscles that are stimulated repeatedly will exhibit summation and tetanus (unlike cardiac muscle)

2) cardiac muscle fiber: the refractory period lasts almost as long as the entire muscle twitch
- long refractory period in a cardiac muscle prevents tetanus

Question 175

excitation-contraction coupling in cardiac contractile cells

Answer 175

-Ca++ entry through Ca++ channels in T-tubules triggers massive release of Ca++ from SR to RyR (not connected to RyR receptors,
opening of these channels caused by entry of Ca++)
(compared to RyR in skeletal muscle)

• Ca++ induced Ca++ release leads to cross-bridge cycling and contraction
• key role for secondary active transport

Question 176

smooth muscle

Answer 176

• smooth muscle is highly variable
• must operate over a range of lengths
• layers may run in several directions (intestine for example, circular and longitudinal smooth muscle)
• small, spindle shaped cells with one nucleus

Question 177

what is the speed of contraction of smooth muscle relative to other muscle types?

Answer 177

contracts and relaxes much more slowly

Question 178

what is the energy expenditure of a smooth muscle relative to other muscles?

Answer 178

uses less energy skeletal or cardiac muscle

Question 179

_____ muscle sustains contraction for extended periods of time

Answer 179

smooth

Question 180

_____ muscles are the slowest to contract and to relax

Answer 180

smooth (and then skeletal and then cardiac)

Question 181

what are the 3 ways we can classify smooth muscle?

Answer 181

• by location (vascular, gastrointestinal, urinary, respiratory, reproductive, ocular (this is the most specific classification))
• by contraction pattern (phasic smooth muscles = contract then relax; tonic smooth muscles = active all the time, gets signals to relax, then contract when signal is gone)
• by communication with neighbouring cells (single-unit smooth muscle, or visceral smooth muscle = all smooth muscle in that tissue behaves as one; multi unit smooth muscle = each individual smooth muscle cell is innervated and behaves independently from its neighbours)

Question 182

phasic smooth muscles can either be ______ (ex: esophagus) or can work in cycles between _____ and ______ (ex: intestine)

Answer 182

relaxed, contraction, relaxation

Question 183

tonic smooth muscles can either be contracted and release when needed (ex: sphincter) , or can ________ as needed (vascular smooth muscle)

Answer 183

vary as needed, but contraction is always happening

Question 184

smooth muscle classification: communication with neighbouring cells

Answer 184

1) single unit smooth muscle cells are connected by gap junctions, and the cells contract a single unit (not all the muscle cells are directly innervated)
b) multi-unit smooth muscle cells are not electrically linked, and each cell must be stimulated independently (they could behave independently but they probably won’t)

Question 185

smooth muscle is arranged in sarcomeres

true or false?

Answer 185

false

Question 186

what kind of signal is needed to initiate contraction of a smooth muscle cell?

Answer 186

electrical, chemical, or both

Question 187

smooth muscle cells are controlled by the ____ nervou system

Answer 187

autonomic

Question 188

smooth muscle cells have very specialized receptor regions on their post-synaptic membranes

true or false?

Answer 188

false, smooth muscle cells lack specialized receptor regions, they have neurotransmitter receptors dispersed all over the cell membrane

Question 189

in smooth muscle ____ is from the extracellular fluid and sarcoplasmic reticulum

Answer 189

Ca++

Question 190

in smooth muscle, ____ initiates a cascade ending with phosphorylation of myosin light chain and activation of myosin ATPase

Answer 190

Ca++

this is different from the role Ca++ plays in generating tension in skeletal and cardiac muscle

Question 191

in smooth muscle, _______ filaments and protein ______ form a cytoskeleton

Answer 191

intermediate, dense bodies

Question 192

in smooth muscle, what attaches to the dense bodies of the muscle cell?

Answer 192

actin

Question 193

in smooth muscle cells, each myosin molecule is surrounded by ______

Answer 193

actin filaments

Question 194

how do T-tubules differ in smooth muscle?

Answer 194

-there are no T-tubules, but there are caveolae (small invaginations in the cell)

Question 195

in smooth muscle, sarcoplasmic reticulum is more organized

true or false?

Answer 195

false, SR varies and is less organized

Question 196

actin is more plentiful in which type of muscle?

Answer 196

muscle that is not striated (smooth muscle)

Question 197

troponin is found in all types of muscle cells

true or false?

Answer 197

false, there is no troponin in smooth muscle

Question 198

is there more or less myosin found in smooth muscle?

Answer 198

less myosin

• myosin filaments are longer
• entire surface of filament is covered with myosin heads

Question 199

there is _____ cytoskeleton in smooth muscle

Answer 199

additional (intermediate filaments and dense bodies)

Question 200

myosin pulls actin molecules in opposite directions to generate tension in which type of muscle cell?

Answer 200

smooth muscle

Question 201

what is the biggest difference in the myosin of smooth muscle comapred to the myosin in other muscle?

Answer 201

myosin light chains: play a key role in regulating activity of myosin and its ability to bind with actin

Question 202

smooth muscle contraction

Answer 202

1) intracellular Ca++ [ ] increase when Ca++ enters cell and is released from SR
2) Ca++ binds to calmodulin (CaM)
3) Ca++-calmodulin activates myosin light chain kinase (MLCK)
4) MLCK phosphorylates light chains in myosin heads and increases myosin ATPase activity (that hydrolyzes ATP and contribute to power stroke)
5) active myosin crossbridges slide along actin and create muscle tension

Question 203

smooth muscle relaxation

Answer 203

1) free Ca++ in cytosol decreases when Ca++ is pumped out of the cell or back into the SR
2) Ca++ unbinds from calmodulin, MLCK activity decreases
3) myosin phosphatase removes phosphate from myosin light chains, which decreases myosin ATPase activity
4) less myosin ATPase activity results in decreases muscle tension

Question 204

if you ______ phosphatase, you improve the ability of that muscle cell to generate tension. If you ______ phosphatase activity, even if you have the same amount of Ca++, you can’t generate as much tension

Answer 204

decrease, increase

Question 205

changes in phosphatase activity alter ______ responses to Ca++

Answer 205

myosin’s

Question 206

smooth muscle contraction: store-operated Ca++ channels

Answer 206

• decreased Ca++ stores in smooth muscle cells can activate these channels
• these open to allow Ca++ to enter smooth muscle cell, increased Ca++ leads to muscle contraction

Question 207

smooth muscle contraction: membrane channels

Answer 207

• activated by depolarization or stretch
• causes an increase in intracellular Ca++
• leads to muscle contraction

Question 208

smooth muscle contraction: membrane receptors

Answer 208

• activated by signal ligands
• either increases IP3 or activates modulatory pathwats

modulatory pathways:
-alter MLCK or myosin phosphate which leads to muscle contraction (or inhibition of muscle contraction)

Increased IP3:

• there are IP3 receptors on the SR
• activates channels on SR
• Ca++ release which leads to muscle contraction

Question 209

what are the 3 different channels (smooth muscle) that can be activated in sarcoplasmic Ca++ release

Answer 209

1) ryanodine receptor (RyR) calcium release channel
- Ca++-induced calcium release (CICR)
2) IP3-receptor channel (DAG or IP3 binding)
3) store operated Ca++ channels (still don’t know exactly how these works, jus that they function physiologically)

Question 210

what are the 3 types of channels on smooth muscle that allow calcium entry into the cells

Answer 210

1) voltage gated Ca++ channels (activated by membrane depolarization)
2) ligand gated Ca++ channels, or receptor operated calcium channels (ROCC)
- this channel is selectively permeable to Ca++
3) stretch-activated calcium channel
- open when pressure or other force distorts cell membrane
- known as myogenic contraction (arteries)

Question 211

many ______ muscles are controlled by both sympathetic and parasympathetic neurons

Answer 211

smooth

Question 212

hormones and paracrines can cause ______ muscle contraction

Answer 212

smooth

Question 213

_____ constricts smooth muscle of airways (asthma)

Answer 213

histamine

Question 214

_____ relaxes smooth muscle of blood vessels (male sexual response, exploited by viagra, cialis)

Answer 214

nitric oxide

Question 215

smooth muscle contraction: electromechanical coupling

Answer 215

• contraction caused by electrical signaling or mechanical signaling
• contraction dependent on changes in membrane potential

Question 216

smooth muscle contraction: pharmacomechanical coupling

Answer 216

• contraction caused by chemical signaling

- no changes in membrane potnetial required

Question 217

______ potentials fire actoin potnetials whent hey reach threshold (smooth muscle) (in the GI tract)

Answer 217

slow wave

Question 218

_____ potentials always depolarize to threshold (smooth muscle) (in the GI tract)

Answer 218

pacemaker

Question 219

_______ occurs when chemical signals change muscle tension through signal transduction pathways with little or no change in membrane potential

Answer 219

pharmacomechanical coupling

Question 220

comapare the internal muscle structure of all three types of muscles

Answer 220

• skeletal: t-tubules and sarcoplasmic reticulum
• smooth muscle: no t-tubules; sarcoplasmic reticulum
• cardiac: t-tubules and sarcoplasmic reticulum

Question 221

compare the structures that control movement of each type os muscles

Answer 221

• skeletal: Ca++ and troponin, fibers independent of one another
• smooth: Ca++ and calmodulin; some fibers electrically linked via gap junctions, others independent
• cardiac: Ca++ and troponin; fibers electrically linked via gap junctions

Question 222

compare the initiation of contraction of each muscle type

Answer 222

• skeletal: requires ACh from motor neuron
• smooth: stretch, chemical signals. can be autorhythmic
• cardiac: autorhythmic

Question 223

poison

Answer 223

a substance that can cause illness or death when introduced into an organism

Question 224

toxin

Answer 224

a substance produced in an organism that can cause illness or death when introduced into an organism

Question 225

venom

Answer 225

toxin which is typically injected into an animal by another

Question 226

which deadly substance is found in puffer fish? what organ does it affect?

Answer 226

• TTX

- gonads, liver (by affecting voltage gated Na+ channels)

Question 227

what was the role of TTX in the movie Serpent and the Rainbow?

Answer 227

-a witch doctor could create and maintain zombies using TTX and extract from Datura plant (contains hallucinogens like scopolamine and other alkaloids

Question 228

curare in 1596

Answer 228

• “blowgun poison”
• in 1596 Sir Walter Raleigh talked about poisoned arrows in his book (he was talking about curare)
• paralytic poison used by natives of South America on arrows and blowgun darts

Question 229

what are the medical uses for TTX?

Answer 229

• blocks voltage-gated Na++ channels, so it does make an effective anaesthetic
• not membrane permeant, so it cannot be topically applied
• stable chemical, high affinity, so takes a long time to wash out

-Na+ channel blockers like benzocaine, lidocaine, and cocaine are much more effective and safe anaesthetics

Question 230

what is curare? what does it do?

Answer 230

• blowgun poison is amix of toxic molecules, d-tubocurare is a purified component = curare
• mechanism of action was discovered in 1934
• it binds to the AChR at the same position occupied by ACh (competitive antagonist)
• prevents ACh from causing an EPSP and eliminates subsequent muscle contractions
• death results from paralysis of diaphragm

Question 231

how do we use curare in modern medicine?

Answer 231

• in 1942 a Canadian Harold Griffith was the first to systematically use curare during surgery
• several other had experimented with using curare to lower amount of anaesthetic use during surgery (this causes flaccid muscle paralysis, makes wound closure much easier, without it, muscles tense up even if the person is under anaesthetic)
• today, pancuronium (a safer synthetic analogue of d-tubocurare) us used instead of curare for surgery (and lethal injection)

-even if you give someone a proper dose, you still haven’t knocked them out, they can still feel everything that’s going on

Question 232

what is the active ingredient in pot? what is its role in plants?

Answer 232

• tetrahydrocannabinol (THC)

- assumed to be a protective chemical in plants

Question 233

is THC hydrophilic or hydrophobic?

Answer 233

THC is very lipid soluble, so very hydrophobic or lipophilic

-this is what makes THC so available to your nervous system

Question 234

the endocannabanoid system

Answer 234

• THC is an agonist for the endocannabanoid receptors CB1 and CB2
• CB1 receptors located in cells throughout the CNS, but on presynaptic terminals (this is the most strongly expressed g-protein coupled receptor in the nervous system- it decreases the synthesis of cyclic AMP)
• CB2 receptors located in cells of the immune system, skeletal muscle
• the natural ligand is called an endocannabanoid
• there may be more cannabanoid receptors

Question 235

explain the physiological process of the effects of THC on the nervous system

Answer 235

• glutamate acts via NMDA receptors to increase intracellular Ca++
• rise in Ca++ causes synthesis and release of endocannabanoids
• endocannabanoids decrease cAMP, and decrease release of neurotransmitter (usually GABA)
• THC saturates the system, causes alteration of neurotransmission in many areas of the cortex (there aren’t specific pathways that are being altered, every pathway that uses GABA will be altered)

Question 236

why is THC associated with the munchies?

Answer 236

-one of the specific effects of THC is to allow an increase in neuronal activity in hypothalamic areas that regulate appetite

Question 237

how was the exploration of cannabanoids related to weight loss remedies?

Answer 237

• the french pharma company created a marketed Rimonibant: a drug to block the CB1 receptor
• idea is to use it to inhibit appetite and cause weight loss
• some people had the opposite effect while using the drug and drugs was not effective enough

Question 238

what is botox

Answer 238

• botox is a purified bacterial toxin: from the bacterium Clostridium botulinum
• called “sausage poison” because it was often found in improperly handled meat
• one of the most toxic substances known to mankind (1 gram of the toxin can kill 1-10 million people)
• in the late 1980’s, doctors used botulinum toxin to treat patients suffering from eye muscle disorders and headaches (by paralyzing muscles in the neck)

Question 239

how does botox work?

Answer 239

• the toxin is taken into nerve terminals by endocytosis (very stable protein, does not get destroyed)
• once inside the nerve terminal the toxin degrades the proteins that are responsible for releasing synaptic vesicles
• the protein has a very long half life in the nerve terminals (weeks)
• stops release of neurotransmitter from synaptic terminals (ACh)
• causes long-lasting muscle paralysis

Question 240

cone snail toxin

Answer 240

• cone snail toxin is a mixture of hundreds of toxins
• physiologists and toxicologists have isolated various components (block numerous ion channels and membrane receptors; one specific component blocks specific type of voltage gated Ca++ channels)

Question 241

explain the physiological process of cone snail toxin on the nervous system

Answer 241

1) action potential travels down axon, depolarization opens voltage gated Ca++ channels, this allows Ca++ to enter presynaptic terminals
2) Ca++ entry causes some synaptic vesicles to fuse with presynaptic membrane and release their neurotransmitter contents into the synaptic cleft

**BUT, when cone snail toxin is present these Ca++ channels are blocked and Ca++ is no longer released; instant paralysis

Question 242

what are some medical uses for cone snail toxin?

Answer 242

• in particualr, one component binds to a Ca++ channel variant within the spinal cord
• team discovered that conotoxin is very effective at blocking chronic pain
• name of drug is ziconotide (annual sales of 15-20 million)

Question 243

what is the main difference in TTX, botox, curare, and cone snail toxin?

Answer 243

-they all cause paralysis but by blocking different receptors

• TTX = Na+ receptors
• curare = ACh receptors
• botox= degrading proteins
• cone snail toxin = Ca++ receptors

Question 244

endocrinology as a science

Answer 244

homeostatic control mechanisms -physiological systems need communication and coordination
-ex: metabolism, salt and water balance, temperature, reproduction, growth

began in the early 20th century with two researchers William Bayliss and Ernest Starling
-interested in was the secretion of alkaline juive in the duodenum under nervous or chemical control

Question 245

what did Ernest Starling deduct in regard to endocrinology and its relationship with pharmacology?

Answer 245

• endocrinology is the basis of pharmacology

- cannot design drugs without understanding how natural substances work

Question 246

more than one hormone can be produced in one endocrine gland

true or false

Answer 246

true

Question 247

one hormone can only be secreted by one tissue

true or false?

Answer 247

false, more than one tissue secretes the same hormone

Question 248

there is usually just one single target cell type for a single hormone

true or false?

Answer 248

false, more than one target cell type for a single hormone

Question 249

a single target cell can be influenced by more than one hormone

true or false?

Answer 249

true

Question 250

hormones are blood borne

true or false

Answer 250

true, but they are also neuronally derived (so false)

Question 251

some hormones are excreted from tissues that have other _____

Answer 251

functions

Question 252

chemical classification: structure, solubility, secretion, transport, and source of peptides

Answer 252

• structure: chains of amino acids (3-500+)
• solubility: hydrophilic
• secretion: exocytosis
• transport: free active peptide or precursor
• source: pituitary, pancreas, GI tract, etc

Question 253

chemical classification: structure, solubility, secretion, transport, and source of amino acid derivatives

Answer 253

• structure: a) catecholamines; b) thyroid hormone; c) melatonin
• solubility: a) hydrophilic; b) hydrophobic; c) hydrophilic
• secretion: a) exocytosis; b) endo and exocytosis; c) exocytosis
• transport: a) 50% to carrier protein; b) most bound to carrier protein; c) 50% bound to carrier protein
• source: a) adrenal medulla; b) thyroid gland;; c) pineal gland

Question 254

chemical classification: structure, solubility, secretion, transport, and source of steroids

Answer 254

• structure: cholesterol derivative
• solubility: hydrophobic
• secretion: diffusion
• transport: most bound to carrier proteins
• source: adrenal and sex steroids

Question 255

_____ compounds are typically bound to carrier proteins to facilitate delivery

Answer 255

hydrophobic

Question 256

______ compounds are not always bound to carrier proteins but they can be. Why?

Answer 256

hydrophilic

• small molecules may be subject to rapid degradation
• half life can be very short, may not be effective by the time it reaches target organ
• half life can be extended with carrier protein

Question 257

hormone processing

Answer 257

1) secretion, constituitive = hormone is constantly being released into circulation - regulated = only release when receiving appropriate signal (ex: pancreas and glucose)
2) binding of hormone to carrier protein (free hormones)

3) activation - can be metabolized and activated, or metabolized and inactivated
- execretion

4) inactivation - includes things like conjugation (chemical group is attached to hormone that inactivates or tag it for secretion (ex: sulfation, sulfate group is attached to steroid - this inactivated steroid makes it more water soluble)

Question 258

what are the 7 post-translational modifications of peptide hormones

Answer 258

1) peptide cleavage
2) glycosylation
3) phosphorylation
4) sulfation
5) amidation
6) acetylation
7) subunit aggregation

Question 259

examples of peptide cleavage

Answer 259

1) prepro TRH has six copies of the 3-amino acid hormone TRH

2) prohormones, such as oplomelanocortin, the prohormones for ACTH, may contain several peptide sequences with biological activity
- this hormone is cleaved into ACTH, lipotropin, endorphin

Question 260

feedback control

Answer 260

this is predominantly negative, i.e. output counteracts input, and is frequently seen in the trophic hormones
-feedback can also be positive

Question 261

thyroid stimulating hormone release from the anterior pituitary is an example of what type of feedback?

Answer 261

negative

Question 262

neuroendocrine reflexes

Answer 262

combination of neural and hormonal processes, not the same as neuromodulation
-ex: knee jerk

Question 263

neuromodulation

Answer 263

suite of neurons that regulate a variety of different behaviours

• sleep wake cycle
• arousal
• reward centers

Question 264

hormone release: rhythyms

Answer 264

release of hormones is entrained to environmental cycles which vary in interval length and duration

ex: melatonin secretion peaks at night - triggered by darkness - this can adapt when changing time zones
- cortisol secretion has two prominent peaks (%pm and 11am)

Question 265

hormone delivery to the target site: carrier proteins

give examples of specific carreirs

Answer 265

can be general or specific to the hormone in question, dictating by binding affinity

ex: corticosteroid binding globulin - corticosteroids; thyroiod hormone binding globulin and transthyretin - thyroid hormones

general carrier: albumin

Question 266

how do carrier proteins help facilitate delivery of hormones to the target site?

Answer 266

• can bind to the surface receptor
• most of the time they bind to nuclear receptors - cause transcriptional changes, causes a genomic response at the target site (non-genomic response when binding at cell membrane, these are fast)

Question 267

which is faster, genomic or non-genomic responses?

Answer 267

genomic is much faster, these bind to nuclear receptors and cause transcriptional changes

Question 268

hormone activation

Answer 268

metabolism of the precursor or release from the carrier protein will activate the hormone that will then have a half life in the blood

Question 269

the length of time for hormone half life follows the general pattern:

Answer 269

1) single amino acid derivatives: minutes (norepinephrine, serotonin, eponephrine)
2) peptide hormones: minutes-hours (depends on the size of the hormone)
3) steroid hormones: hours (these are lipophilic, harder to destroy - it’s very expensive energy wise to make these hormones which is why they are made to last)

Question 270

3 methods of hormone inactivation

Answer 270

1) enzyme degradation: tripsin, pepsin, etc.
- these rapidly degrade hormones
- non specific, meaning they don’t have specific targets

2) hormone receptor complex endocytosis: as long as the hormone is bound to the receptor, the cell continually responds, until the endocytotic process draws the hormone into the cell, the cell no longer responds

3) conjugation: steroids are often conjugated
- sulfation
- attaching chemical groups to the steroid that makes them more water soluble, more prone to be filtered at the kidney and peed out; or tied for further degradation by other enzymes

Question 271

endocrine dysfunction: hyposecretion

Answer 271

primary or secondary, usually result in atrophy of the endocrine gland and normally treated through replacement therapy

Question 272

endocrine dysfunction: hypersecretion

Answer 272

primary or secondary, usually the result of a benign tumour (adenoma), normally treated through inhibition

Question 273

what is atrophy?

Answer 273

when the gland has shrunk, not capable of producing sufficient amounts of the hormone

Question 274

what is primary dysfunction? (endocrine dysfunction)

Answer 274

site of synthesis of the active component

• ex: adrenal cortex not making enough cortisol
• ex: either the anterior pituitary or hypothalamus, insufficient stimulus to stimulate cortisol release

Question 275

CRH is released from the _____

Answer 275

hypothalamus

Question 276

ACTH is released from the _____

Answer 276

anterior pituitary

Question 277

cortisol is released from the _______

Answer 277

adrenal cortex

Question 278

what does the HPA axis stand for

Answer 278

hypothalamic pituitary adrenal complex

Question 279

explain the HPA axis in simple terms

Answer 279

CRH is released from the hypothalamus, this targets the anterior pituitary (ACTH is released), this targets the adrenal cortex (cortisol is released into circulation)
-response

Question 280

how would an injection of cortisol effect the HPA axis?

Answer 280

an injection of cortisol will inhibit release of CRH from the hypothalamus and ACTH from the anterior pituitary

Question 281

endocrine dysfunction: target cell

Answer 281

lack of receptor or biochemical machinery at the target cell

-ex: hyperinsulinemia - type 1 diabetes, dysfunction at target site - inhability to maintain set point

Question 282

what are the 3 main factors that contribute to endocrine dysfunction?

Answer 282

• hyposecretion
• hypersecretion
• target cell dysfunctions

Question 283

response at target cell: up and down regulation

Answer 283

receptors at the target cell are themselves regulated in response to hormone levels influencing abundance and affinity

Question 284

measurement of binding kinetics for hormone/receptor complexes relies heavily on ___?

Answer 284

the chemical law of mass action

Question 285

according to the law of mass action, if Kd is high, binding affinity is ?

Answer 285

low

Question 286

do all hormone receptor complexes adhere to the law of mass action?

Answer 286

• non-cooperative = law of mass action upheld
• positively cooperative = ligand binding increases receptor affinity of vacant receptors (affinity increases)
• negatively cooperative = ligand binding decreases receptor affinity of vacant receptors (ex: insulin, insulin binds neighbouring receptors are less likely to bind insulin - to make sure there’s not an overwhelming amount of ligand binding)

Question 287

response at target cell: permissiveness

Answer 287

one hormone cannot fully exert its effect without the other being present - dual action required

Question 288

response at target cell: synergism:

Answer 288

the combined effect is greater than the sum of the parts

Question 289

what does the combination of glucagon, epinephrine, and cortisol do to the glucose levels in the blood?

Answer 289

increase significantly (over 250 mg/dl)

Question 290

what does the combination of glucagon and epinephrine do to the glucose levels in the blood?

Answer 290

slightly increases, not as much as the combination of glucagon, epinephrine, and cortisol

Question 291

response at target cell: antagonism

Answer 291

the actions of one hormone reduces the effectiveness of the second - can be direct or indirect

• antagonism controls hypersecretion
• agonism controls hyposecretion (sometimes hypersecretion)

Question 292

membrane bound hormone receptors

Answer 292

• 4 priamry: ligand gated, enzyme linked, guanylyl cyclase and G-protein linked receptors
• second messenger systems include: adenylate cyclase, guanylate cyclase, and inositol phosphate and diacyl glycerol

Question 293

nuclear hormone receptors

Answer 293

most lipophilic hormones act through nuclear receptors and many genes will have responsive elements

Question 294

explain the process of carrier protein binding to a nuclear receptor

Answer 294

• steroid released from carrier protein, binds to cytoplasmic receptor - binds to DNA - conformational changes
• chaperone proteins: large group = heat chock proteins (HSPs)
• these protect receptor in cytoplasm
• steroid receptor is therefore available for steroid to bind to
• these HSPs increase during stressful periods

Question 295

what is another name for posterior pituitary

Answer 295

neurohypophysis, pars nervosa

Question 296

what is another name for anterior pituitary

Answer 296

adenohypophysis, pars distalis

Question 297

as a foetus, how many parts do we have to the pituitary gland?

Answer 297

3

Question 298

posterior pituitary

Answer 298

1) the hypothalamus and posterior pituitary form a neuroendocrine system with cell bodies based in the hypothalamus
2) posterior pituitary hormones synthesized in the hypothalamus
3) cell bodies then extend down the infundibulum and terminate in the posterior pituitary

Question 299

which hormones are released from the posterior pituitary?

Answer 299

oxytocin and vasopressin (predominantly but not always)

Question 300

what are the abreviations for oxytocin and vasopressin?

Answer 300

oxytocin = OT and vasopressin = AVP

Question 301

precursor peptides for OT and AVP (neurophysins) are produced int he _____

Answer 301

hypothalamus

Question 302

AVP and OT neurophysins (precursor for oxytocin and vasopressin) + proteolytic enzymes are packaged in secretory granules and begin to migrate down the axon to the ______ where the nerve terminals are located

Answer 302

neurohypophysis

Question 303

reduced ECFV (extracellular fluid volume) increases plasma osmolarity which increases osmoreceptor activity which increases which hormone from the posterior pituitary?

Answer 303

vasopressin release

Question 304

reduced ECFV (extracellular fluid volume) decreases left atrial volume which decreases arterial blood pressure which increases which hormone in the posterior pituitary?

Answer 304

vasopressin release

Question 305

what two things can lead to an increase in vasopressin release from the posterior pituitary? What is the consequence of this?

Answer 305

increase osmoreceptor activity or decreased arterial blood flow

• increased H2O reabsorption in renal tubules
• vasoconstriction of vascular smooth muscle

Question 306

vasopressin is an anti-diuretic hormone (reduction in urine flow rate or production)

true or false?

Answer 306

true

Question 307

which two situations cause an increase in oxytocin release?

Answer 307

birth canal distension and infant suckling

Question 308

birth canal distension causing an increase in oxytocin release is what kind of feedback loop?

Answer 308

positive - as the birth canal distends, more oxytocin is released until the baby is born

Question 309

what is the effect of an increase in oxytocin release due to infant suckling?

Answer 309

increase in uterine muscle (myometrium) contraction during parturition, increase in milk ejection from breast

Question 310

what are 3 behavioural aspects of oxytocin?

Answer 310

• increases maternal behaviour in rats but estrogens need to be present
• plasma OT levels increase during sexual arousal in both sexes
• act as neuromodulators in the brain to influence social recognition, memory, and affiliative behaviours such as “pair bonding” (rodent research)

Question 311

what are 3 behavioural aspects of vasopressin release?

Answer 311

• stimulated release of ACTH that is synergistic with CRH
• seems to play a greater role in males rather than females in regard to social recognition and consolidation of social memory (rodent research)
• aggression, courtship, scent making, and learning (rodent research)

Question 312

hormones released from the anterior pituitary go through the ______

Answer 312

blood supply

Question 313

what are the hormones that are released from the anterior pituitary

Answer 313

ACTH, TSH, FSH, LH, PRL, GH

Question 314

adenohypophysial cells (anterior pituitary)

Answer 314

histological and cytological methods have provided definitive evidence on the cellular source for each hormone released from the adenohypophysis

Question 315

which hormone from the anterior pituitary is a corticotroph

Answer 315

ACTH

Question 316

which hormone from the anterior pituitary is a thyrotroph

Answer 316

TSH

Question 317

which hormones from the anterior pituitary are gonadotrophs

Answer 317

FHS and LH

Question 318

which hornome from the anterior pituitary is a lactotroph

Answer 318

PRL

Question 319

which hormone from the anterior pituitary is a somatotroph

Answer 319

GH

Question 320

hormones synthesized and released from the anterior pituitary are under the control of ______ hormones that can be stimulatory or inhibitory

Answer 320

hypophysiotrophic

Question 321

name each hypophysiotropic hormone from the anterior pituitary and their associated pituitary hormone along with the final hormone produced

Answer 321

1) TRH; pituitary hormone - thyroid stimulating hormone; final hormone - TH
2) CRH; pituitary hormone - adrenocorticotropic hormone; final hormone - cortisol
3) GnRH; pituitary hormone - follicle stimulating hormone and lieutinising hormone; final hormone - estrogens and androgens
4) GHRH; pituitary hormone - growth hormone; final hormone - GH and IGF’s

Question 322

what does a release of TSH do to the body

Answer 322

-hypothalamic pituitary TSH axis

anterior pituitary releases TSH, stimulates the thyroid gland, releases T3 and T4, affects metabolic rate

Question 323

what does the release of ACTH do to the body

Answer 323

-hypothalamic pituitary ACTH axis

anterior pituitary releases ACTH, stimulates adrenal cortex, release of cortisol, affects metabolic actions

Question 324

what does the release of prolactin do to the body

Answer 324

dopamine stimulates release of prolactin from the anterior pituitary, stimulates mammary glands, breast growth and secretion

Question 325

what does a release in growth hormone do to the body

Answer 325

somatostatin stimulates the release of GH from anterior pituitary, targets the liver and/or many tissues, liver releases somatomedins which targets bone and soft tissue; other tissues target metabolic actions

Question 326

what does the release of LH and FSH do to the body

Answer 326

LH and FSH are released from the anterior pituitary, target gonads (ovaries and testies), this targets sex hormones (estrogens, progesterone, testosterone), and gamete production (ova and sperm)

Question 327

we have TSH, ACTH, LH and FSH, prolactin, and GH. Which of these are under stimulating control? which are not?

Answer 327

stimulating control means that there needs to be a stimulus to activate the release. Inhibitory control means that in order to be released, there needs to be a lack of stimulus

TSH, ACTH, LH and FSH are under stimulating control

GH’s are largely under inhibitory control (same with prolactin)

Question 328

structural characterisation of adenohypophysial hormones: GH family; growth hormone is well conserved, however there are many different variants of _____

Answer 328

prolactin

Question 329

structural characterisation of adenohypophysial hormones: GH family; what are 3 different variations of prolactin

Answer 329

mammalian prolactin (normal), cleaved prolactin, spliced variant (deletion)

Question 330

structural characterisation of adenohypophysial hormones: glycoprotein family

Answer 330

follicle stimulating hormone (FSH), leutinizing hormone (LH), thyroid stimulating hormone (TSH), human chorionic gonadotropin (hCG) - all belong to this group

-each has an alpha and a beta subunit, the amino acid sequence of the alpha subunit is similar between hormones but the beta subunit varies

Question 331

pregnancy tests use the difference in glycoprotein hormones to determine if a female has conceived or not. In these hormones, there are an alpha subunit and a beta subunit, which one differs across the glycoprotein family? which one stays the same?

Answer 331

alpha stays the same, beta varies

Question 332

Pars intermedia

Answer 332

many animals have an anatomically separate pars intermedia (sits between anterior and posterior pituitary)

• the predominant endocrine product is alphaMSH development
• as adults these cells are not anatomically distinct but still synthesize and secrete alphaMSH

Question 333

alphaMSH is derived from what? (what is the precursor?)

Answer 333

POMC

Question 334

POMc is a precursor for which hormones?

Answer 334

ACTH, lipoprotein, beta endorphin

-ACTH can split into alpha MSH (leads to melanin synthesis, immune response, decreased food intake)

Question 335

which enxyme cleaves POMC to create the molecules that it serves as a precursor for?

Answer 335

proconvertase

Question 336

normal growth means:

Answer 336

1) protein, fat, and cartilage synthesis
2) cell proliferation (hyperplasia and hypertrophy)
3) bone lenghtening (increased extracellular matrix)

Question 337

normal growth is influenced by:

Answer 337

1) genetic resolve
2) diet and nutrient transfer
3) disease and stress (this can be reversed regardless of when this may occur)
4) multiple layers of hormonal control (ex: growth hormones (GH; IGF’s; steroids; TH’s; Ca++ regulation)

Question 338

where do we find most of the calcium in our body?

Answer 338

in our bones

Question 339

growth rate

Answer 339

neonatal growth under influence of placental hormones growth rate varies throughout life

• GH levels increase during puberty
• in males, testicular androgens are very important and increase dramatically during puberty
• adrenal androgens also increase and may be more important in females
• testosterone and estrogen both ultimately “put the brakes on”

Question 340

____% of brain growth appears in the first two years of life

Answer 340

70

Question 341

growth hormone (GH) production is stilumated by _____ and inhibited by ______

Answer 341

GHRH, GHIH (somatostatin)

Question 342

GH is a ____ amino acid long polypeptide produced in somatotrophs

Answer 342

191

Question 343

____ is the most abundant adenohypophysial hormone (4-10% of the wet weight of the gland approx 5-10mg)

Answer 343

GH

Question 344

spontaneous secretion of GH over a 24 hour period usually peaks in the first ____ minutes of sleep

Answer 344

90

Question 345

GH is transported in _____ attached to one or more _____ (even tho it’s hydrophilic)

Answer 345

plasma, binding proteins

Question 346

the somatomedin hypothesis

Answer 346

“growth hormone does not have direct effect on growth of any given tissue but rather acts indirectly through somatomedins”

• there are two main somatomedins - insuline like growth factors (IGF) 1 and 2 (I and II)
• they are 70 and 67 amino acids long respectively and share many similarities with insulin
• IGF II is 3X more abundant in adult plasma in comparison to IGF I

Question 347

where does the somatomedin hypothesis come from ?

Answer 347

Can measure bone growth through the incorporation of sulfate (in petri dish)
-add plasma - bone growth

Hypophysectomised mouse
-add plasma - no growth

Hypophysectomized mouse
-add plasma and GH (growth hormone) - growth occurs

Growth hormone is stimulating the release of an additional factors that causes bone growth
-that’s where this hypothesis comes from

Question 348

insulin and IGF receptors

Answer 348

insulin acts through and has highest affinity for its own receptor and vice versa, IGF I can bind to insulin receptors and cause an effect, but insuline tends to not bind to IGF I receptors at all

Question 349

IGF’s

Answer 349

circulating levels of IGF A increase massively during pubertal growth spurt but GH increaes moderately by comparison

• tissue specific regulation of IGF I synthesis (related to the role that IGF is playing in regulating bone growth)
• GH does not regulate IGF II production to the same extent (during puberty)
• IGF II is important during fetal development and plays a role in adult growth but not to the same extent as IGF I

Question 350

what is a bone

Answer 350

bone is living tissue surrounded by an extracellular organinc matrix with a variety of cell types that have specific roles

• compact bone is dense and used for support
• spongy bone or trabecular bone forms a calcified lattice

Question 351

the ______ is the mature bone shaft with the _____ at either end. In a growing bone the epiphysis is separated from the diaphysis by the ______

Answer 351

disphysis, epiphysis, epiphyseal plate

Question 352

where does growth happen in a bone?

Answer 352

epiphyseal plate

Question 353

bone growth (width)

Answer 353

osteoblasts produce enzymes (osteoid) collagen and proteins to provide a framework for hydroxyapatite crystals. they deposit new bone on the outer edges of old bone to increase width. this is a dynamic process
-osteoblasts will ultimately turn into mature bone cells - osteocytes

Question 354

bone growth (length)

Answer 354

bone length growth is a different process and is regulated by cartilage cells, chondrocytes, located in the epiphyseal plates
-chondrocytes divide and multiply, lengthening the epiphysis with the older cartilage cells enlarging at the border of the diaphysis

Question 355

the dual-effector theory

Answer 355

growth of long bone is under the influence of growth hormone and the insulin like growth factors (IGF)
-in the absense of these hormones, normal bone growth does not occue

Question 356

where does abnormal bone growth happen?

Answer 356

-can happen in a variety of regions where lesions occur (increase or decrease in growth hormone)

Question 357

abnormal bone growth: lesion in anterior pituitary

Answer 357

reduction in GH, reduction of IGF = reduction of growth = hypopituitary dwarfism - extremely small population, predisposed to a lack of GH production

• increase of release of GH, increase in IGF from liver, increase in action of IGF’s on somatic tissue (can happen2 times in life = infancy, results in genetic resolve in extremely tall people; can result in big head or big hands; can occur during adulthood (puberty or slightly after) = acromegaly
• in infants, it’s called gigantism, in adults, it’s called acromegaly

Question 358

abnormal bone growth: lesion in the liver

Answer 358

• liver is less responsive to growth hormone stimulation IGF-I release
• results in Laron dwarfism
• there are various forms of this

3 primary effectors of Laron’s Dwarfism:

• lack of GH receptors at the liver
• lack of IGF-I responsiveness
• lack of GH binding carrier proteins (not enough gets to action site)

Question 359

abnormal bone growth: lesion at the end organ

Answer 359

• reduce growth rate
• not binding properly to end organs
• receptors for IGF-I for example might have a mutation, lessened affinity, responsiveness is reduced

Question 360

____ - involved in energy homeostasis. hypothyroidism = reduced growth, largely permissive

Answer 360

thyroid hormones (TH)

Question 361

_____ - involved in carbohydrate metabolism. Deficiency can block growth and excess can promote growth, potential cross reactivity with IGF receptors (doesn’t tend to bind strongly to these)

Answer 361

insulin

Question 362

_____ and ____ - arrest “long-bone” length increase by closure of the epiphyseal plate (at the end of puberty, these should be at steady levels for the next 10-20 years and growth (lengthening) does not occur, only widening or narrowing)

Answer 362

androgens and estrogens

Question 363

_____ - belongs to the GH family and influences mammary gland growth as well as aspects of the immune system

Answer 363

prolactin

Question 364

______ - belongs to the GH family and influences neonatal development, metarnal glucose and amino acid supply. Peaks around mid pregnancy until full term

Answer 364

placental lactogen

Question 365

____ - nerve growth factors (NGF’s) - peripheral neurons, often used as therapeutic when people have neurodegenerative diseases such as alzheimer’s

Answer 365

neurotropic factors

Question 366

______ - red blood cell growth factor - released from kidneys, greater oxygen carrying capacity from more red blood cells

Answer 366

erythropoietin

Question 367

______ - vascular injury repair but also involved in the development of artherosclerosis - how blood vessels mature

Answer 367

platelet derived growth factors

Question 368

______ - enhances proliferation of epidermis, gut lining, pulmonary lining - epidermal growth factor released from cows saliva, promotes growth of plant

Answer 368

epidermal growth factors

Question 369

_____ angiogenesis - fibroblast growth factors (growth of blood vessels) - transforming growth factors

Answer 369

tumour derived growth factors

Question 370

what is the most tightly regulated ion in circulation?

Answer 370

Ca++

Question 371

___% of the bodies calcium is calficied structures, ____% is intracellular ___% exists in the ECF, half of this is bound to proteins or negatively charged ions and the rest is in free form Ca++

Answer 371

99, 0.9, 0.1

Question 372

up to ___% of Ca++ ions are bound to proteins so that when blood filters through kidneys, it won’t be lost (peed out), retain a lot of calcium in circulation because of this

Answer 372

60

Question 373

neuromuscular excitability - reduced calcium leads to _____ muscle contraction and high levels lead to _____ muscular contraction

Answer 373

tetanic, reduced

Question 374

stimulus secretion coupling

Answer 374

many cells will require calcium to enter the cell to stimulate the secretion of a given substance

Question 375

why regulate calcium? (5 reasons)

Answer 375

1) neuromuscular excitability
2) stimulus-secretion coupling
3) cell to cell integrity or tight junctions
4) cofactor for clotting blood
5) required for structural form of bone and teeth

Question 376

to maintain Ca++ balance, dietary intake should ___ Ca++ loss in the urine and feces

Answer 376

equal

Question 377

bone is a living tissue that is packed with _____ crystals between a collagen matrix

Answer 377

hydroxyapatite

Question 378

regulation of calcium always impacts phosphate concentrations

true or false?

Answer 378

true

Question 379

what provides strength to bones?

Answer 379

Ca++ and phosphate hydroxyapatite crystals

-if we get crystallization of these at the wrong places it can cause things like kidney stones

Question 380

bone remodelling

Answer 380

remodelling requires deposition and resorbtion

• osteocytes
• osteoblasts
• osteoclasts

Question 381

osteocytes

Answer 381

mature bone cells

-have Ca++ pumps on cell membrane

Question 382

osteoblasts

Answer 382

bone builders responsible for depositing the collagen matrix

Question 383

osteoclasts

Answer 383

bone breakers

• decrease the pH of the environment, crystlas are more likely to dissolve
• carbonic anhydrase drives the reaction

Question 384

what are the 2 places we can get Ca++ from the bony matrix?

Answer 384

• can be taken from bone matrix (takes longer cause we need to get calcium from crystals)
• calcium can be taken from bone fluid space

Question 385

hormones involved in Ca++ regulation: parathyroid hormone

Answer 385

• negative relationship between plasma [ ] and plasma [Ca++] that is extremely sensitive
• parathyroid hormone is hypercalcaemic
• primary job is to increase levels of Ca++
• there is a negative relationship between the two

Question 386

hormones involved in Ca++ regulation: vitamin D3

Answer 386

• cholecalciferol

- needs to be converted to 1.25 - (OH) - vitamin D3 (calcitriol)

Question 387

hormones involved in the regulation of Ca++: calcitonin

Answer 387

• the ONLY hypocalcaemic hormone
• decreases Ca++ levels in the body
• as Ca++ goes up, calcitonin goes up and vice versa

Question 388

what is parathyroid hormones effect on bone

Answer 388

1) fast homeostatic regulation of Ca++ from bone fluid space

2) slower balancing of total body Ca++ from resorptive processes

Question 389

partahyroid hormone (PTH) _____ calcium and ____ phosphate reabsorption in the kidneys

Answer 389

increases, decreases

Question 390

parathyroid hormone (PTH)’s effect on intestines

Answer 390

actions are indirect through stimulation of vitamin D3 production

Question 391

vitamin D

Answer 391

• considered by many as a hormone as it can be produced in the skin from 7-dehydrocholesterol
• two important enzymatic steps that involve the sequential addition of hydroxyl groups onto the backbone of vitamin D
• activation of 1alpha hydroxylase is the most important step and this enzyme is regulated by PTH
• NB vitamin D is often considered a steroid therefore where does it at in the target cell? (likely acts in the nucleus, causing transcriptional change)
• slower than non-genomic response
• can trigger fast responses

Question 392

target site for vitamin D3

Answer 392

the gut is probably the best documented area of vitamin D3 action, where both fast and slow components are initiated

Question 393

what is the concentration of Ca++ in the lumen

Answer 393

approx 1 mM

Question 394

is the concentration of calcium higher in the lumen or in the cytosol

Answer 394

way higher in the lumen

Question 395

____ and _____ are carrier proteins inside cells that Ca++ binds to to keep constant concentration

Answer 395

calbindin and calmodulin

-vitamin D initiates response, vitamin D defficiency can cause low [ ] of Ca++

Question 396

ECaC

Answer 396

epithelial Ca++ channel = gate keeper of passive movement of Ca++ from outside to inside the cell

Question 397

what are different modes of transport of Ca++ into our out of cells?

Answer 397

• ECaC = epithelial Ca++ channel
• Na/Ca exchange
• PMCA = plasma membrane calcium ATPase
• vitamin D initiation of calmodulin and calbindin which increases transcription of ECaC

Question 398

regulation of vitamin D with PTH: hypocalcaemic event

Answer 398

• Ca++ is lower than it should be
• -rapid release of parathyroid hormone
  
  • TCH is a hypercalcemic hormone (trying to get calcium back to where it should be)
  • translocated to liver
  • attaches to backbone of D3
  • in kidney, 2 groups attached to backbone
  • PTH stimulated synthesis of alpha hydroxylase
  • 2 hormones working to promote an increase in circulating levels of Ca++
  • 2 hormones target 3 main organs (kidney - promotion of Ca++ reabsorption by parathyroid hormone; bone, promotion of calcium an d phosphate dissolution; gut - increase in vitamin D3 = increase in Ca++ uptake throughout the gut)
    
    • to promote Ca++ reabsorption into the blood, levels go back up to where they should be
      
      • Ca++ itself is negatively feeding back
      • phosphate as well - reduces the amount of available vitamin D3

Question 399

regulation of vitamin D with PTH: hypocalcaemic event

Answer 399

• Ca++ is lower than it should be
• -rapid release of parathyroid hormone
  
  • TCH is a hypercalcemic hormone (trying to get calcium back to where it should be)
  • translocated to liver
  • attaches to backbone of D3
  • in kidney, 2 groups attached to backbone
  • PTH stimulated synthesis of alpha hydroxylase
  • 2 hormones working to promote an increase in circulating levels of Ca++
  • 2 hormones target 3 main organs (kidney - promotion of Ca++ reabsorption by parathyroid hormone; bone, promotion of calcium an d phosphate dissolution; gut - increase in vitamin D3 = increase in Ca++ uptake throughout the gut)
    
    • to promote Ca++ reabsorption into the blood, levels go back up to where they should be
      
      • Ca++ itself is negatively feeding back
      • phosphate as well - reduces the amount of available vitamin D3

Question 400

calcitonin

Answer 400

not involved in day to day regulation but may be involved during the absorptive state and also during pregnancy
-calcitonin has both hypocalcaemic and hypophosphatemic effects

Question 401

when plasma Ca++ concentrations go up, this stimulates the _____ gland ___ cells and causes an increase in _____ which lowers the plasma Ca++ concentration

Answer 401

thyroid, C, calcitonin

Question 402

when plasma Ca++ concentrations go up, this stimulates the _____ gland ___ cells and causes an increase in _____ which lowers the plasma Ca++ concentration

Answer 402

thyroid, C, calcitonin

Question 403

osteoblasts are derived from ____ in the bone marrow and osteoclasts are derived from ____ in the bone marrow

Answer 403

stromal cells, macrophages

Question 404

osteoblasts are derived from ____ in the bone marrow and osteoclasts are derived from ____ in the bone marrow

Answer 404

stromal cells, macrophages

Question 405

osteoblasts and its precursor cells produce two main messengers, what are they?

Answer 405

RANKL (receptor activator of NFkB ligand) and osteopritegerin

Question 406

____ stimulates the production of osteoprotegerin

Answer 406

estradiol

Question 407

why aren’t men subject to high risk of osteoporosis like women?

Answer 407

• androgen levels don’t tend to decline throughout the male life cycle
• P450 aromatase is a key enzyme to make estrogen from androgen, this enzyme is always present in men

Question 408

thyroid hormones (T3 and T4)

Answer 408

tetraiodothyronine (T4) and triiodothyronine (T3) are both derived from thyroglogulin and synthesized in the follicular cells and the colloid of the thyroid gland

• involved in the regulation of metabolic rate and are key during development (particularly development of neural tissue)
• the basic ingredients are the amino acid tyrosine and the element iodine, tyrosine can be made in the body whereas iodine is an essential component of our diet

Question 409

thyroid hormones (T3 and T4)

Answer 409

tetraiodothyronine (T4) and triiodothyronine (T3) are both derived from thyroglogulin and synthesized in the follicular cells and the colloid of the thyroid gland

Question 410

a lot of energy is required to synthesize T3 and T4, because oft his, tyrosines are subject to recycling

true or false?

Answer 410

true

Question 411

what are 4 actions of thyroid hormones?

Answer 411

1) calorigenic: TH is the most important regulator of basal metabolic rate
2) sympathomimetic effect: action is similar to the sympathetic nervous system (increases target response to catecholamines)
3) cardiovascular: largely as a result of the increases in catecholamine receptors and calorigenic effects
4) growth: synergistic actions with both GH and IGF’s, TH is essential for normal growth and neural development

Question 412

thyroid hormone abnormalities

Answer 412

• this is one of the more common endocrine disorders and is very prevalent in young adult women
• includes both hypothyroidism and hyperthyroidism either of which are characterized by goiter
• goiter is an over stimulation of the thyroid gland and not necessarily related to the capacity of the gland to synthesize and release TH
• exophthalmos is a common feature of graves disease which is an autoimmune disease

Question 413

hypothyroidism (3 different causes)

Answer 413

cause: primary failure of the thyroid gland = decrease in T3 and T4, increase in TSH: goiter is present
cause: secondary to hypothalamic or anterior pituitary failure = decrease in T3 and T4, decrease in TRH and/or TSH: goiter is not present
cause: lack of dietary iodine = decrease in T3 and T4, increase in TSH: goiter is present

Question 414

hyperthyroidism (3 causes)

Answer 414

cause: abnormal presence of long acting thyroid stimulator (LATS) (grave’s disease) = increase in T3 and T4, decrease in TSH: goiter is present
cause: secondary to excess hypothalamic or anterior pituitary secretion = increase in T3 and T4, increase in TRH and/or TSH: goiter is present
cause: hypersecreting thyroid tumour = increase in T3 and T4, decrease in TSH: goiter is not present (occasionally this can cause inflammation of thyroid gland)

Question 415

possible symptoms of hypothyroidism

Answer 415

• low BMR
• decreased perspiration
• slow pulse
• lowered body temperature
• cold intolerance
• lethargy, tiredness
• weight gain
• loss of hair
• edema of face and eyelids
• menstrual irregularities
• goiter (may or may not be present)

Question 416

possible symptoms of hyperthyroidism

Answer 416

• elevated BMR
• increase perspiration
• rapid pulse
• increase body temperature
• heat intolerance
• nervouseness and anxiety
• weight loss
• muscle wasting
• increased appetite
• exophthalmos (sometimes)
• goiter (primary or secondary origin)

Question 417

melatonin

Answer 417

primary hormone released from the pineal gland and is synthesized from the amino acid tryptophan (acts as a neurotransmitter as well)

• synthesized and released in a rhythmical fashion that is closely related to circadian rhythms - scotophase (dark) and photophase (light)
• darkness is a universal stimulation for the synthesis and release of melatonin from the pineal gland suggesting a strong link between the pineal and the optic tract

Question 418

what is the link between the pineal gland and the optic tract?

Answer 418

the link comes from the suprachiasmic nucleus (SCN) which is our major biological clock where the interaction between PER genes and CLOCK proteins cycle at a remarkably constant rate that shifts depending on light cues

Question 419

there is an inhibition of the pineal gland during _____

Answer 419

phosphotase (light)

Question 420

reproduction follows cycles, so there is a link between _____, sex hormones, and reproduction

Answer 420

melatonin

Question 421

the adrenal gland sits on top of which structure?

Answer 421

kidney

Question 422

the adrenal gland has three layers to its cortex, what aret hese layers and which steroids do they each produce

Answer 422

inner layer: zona reticularis - adrenal androgens (primary = DHEA)

middle layer: zona fasiculata - glutocorticoids (main one that we produce is cortisol)

outer layer: zona glomerulosa - mineralocorticoids (involved in mineral balance, increases in Na+ and K+)

Question 423

adrenal hormones

Answer 423

Adrenal steroids released from the adrenal cortex:

• mineralocorticoids: aldosterone
• gluticocorticoids: cortisol
• sex hormones: dehydroepiandrosterone androstenedione (androgens) and estrogens

Catecholamines released from the adrenal medulla:

• epinephrine (80%)
• norepinephrine (20%)

Question 424

cholesterol as a precursor for steroid synthesis

Answer 424

• composed of 4 main loops with an extension on loop D
• P450 side chain cleavage (sits on inner mitochondrial membrane)
• huge impact on steroid synthesis

Question 425

three main “parent” molecules of cholesterol

Answer 425

C21 - pregane (base of progesterone)

C19 - androstane (bases of androgens)

C18 - estrane (base of estrogens)

Question 426

adrenocorticosteroids

Answer 426

1) gluticocorticoids: corticosteron - precursor for cortisol

2) mineralocorticoids - aldosterone (precursor is corticosterone)

Question 427

sex steroids

Answer 427

1) androgens: DHEA is precursor for androstenedione which is the precursor for testosterone, which is the precursor for DHT
2) estrogens: estrone (made from androstenedione with the help of aromatase), estradiol (made from testosterone with the help of aromatase), estriol (made from estradiol)

Question 428

mineralcorticoid

Answer 428

• aldosterone acts on the distal and collecting tubules of the nephron in the kidney to promote Na+ reabsorption and inhibit K+ reabsorption (there are very few life sustaining hormones but this is one of them, if you lack the ability to synthesize aldosterone you will die)
• regulates body fluid volume which has implications on the renal and cardiovascular systems
• secretion is regulated by the renin angiotensin system and also directly by circulating K+ [ ] . aldosterone regulation is largely independent of the pituitary gland
• hyperaldosteronism can be either primary (Conn’s syndrome) or secondary. symptoms present as hypernatremia, hypokalemia, and usually hypertension

Question 429

why are estrogens considered female sex steroids and androgens considered male sex steroids?

Answer 429

-in females, there’s a higher concentration of estrogen and in males more androgens

Question 430

dehydroepiandrosterone (DHEA)

Answer 430

• the adrenal gland produces small amounts of both (estrogens and androgens) as DHEA is an adrenal androgen (in females this is important in directing development, major source of adrenal androgens in females)
• in males, testosterone overpowers the actions of DHEA, however as females otherwise lack androgens DHEA plaus a role in the pubertal growth spurt, hair growth and the female sex drive

Question 431

adrenogenital syndrome

Answer 431

symptoms are dependent on sex and age of hyperactivity onset

• adult females: masculinisation, facial hair,, deepening of voice, etc.
• newborn females: psuedohermaphrodism (females with male parts)
• adult males: no effect
• pubertal males: precocious pseudopuberty (individual develops secondary sexual characteristics but is not fertile)

Question 432

glucocorticoid release

Answer 432

• triggered by stress or diurnal rhythm
• targets the hypothalamus which releases CRH
• CRH targets teha ntrior pituitary which releases ACTH
• targets adrenal cortex which releases cortisol
• results in an increase in blood glucose (by stimulating glucogenesis and inhibiting glucose uptake)
• increase in blood amino acids (by stimulating protein degradation)
• increase in blood fatty acids (by stimulating lipolysis)

Question 433

what are the direct action of glucocorticoids

Answer 433

• stimulates gluconeogenesis - generation of glucose from non-carbohydrate substrates (amino acids, pyruvates, glycerol)
• inhibits glucose uptake by many peripheral tissues
• stimulates protein degradation in muscle
• stimulated lipolysis, mobilising fatty acids as an alternative energy source

Question 434

what are the permissive actions of glucocorticoids

Answer 434

-vascular collapse during stressful events in the absense of glucocorticoids

Question 435

what are the anti-inflammatory and immunosuppresive actions of glucocorticoids

Answer 435

• the anti-inflammatory effects are seen following administration of supra physiologic or pharmacologic levels
• prevention of leucocytes infiltration into the wound site
• atrophy of lymphatic system

Question 436

cortisol hypersecretion

Answer 436

Cushings syndrome (hypersecretion), caused by:

• increased amounts of CRG or ACTH
• adrenal tumours
• ectopic ACTH release

symptoms include:

• excess glucose (coining the term adrenal diabetes)
• fat deposition in the face and abdomen, thin legs and arms
• facial hair excess

Question 437

cortisol hyposecretion

Answer 437

Addison’s disease (hyposecretion)

• general name for bilateral damage to the adrenals
• can also be primary or secondary in nature

symptoms include:

• increased integument pigmentation
• weakness, weight loss, hypotension, salt craving (because this enhances salt reabsorption) and hypoglycemia

Question 438

general adaptation to stress: primary alarm response

Answer 438

• catecholamine surge into the system
• increase in BMR
• increase in blood flow to required organs
• hepatic glycogenolysis

-mobilizing energy reserves immediately

Question 439

general adaptation to stress: secondary resistance response

Answer 439

• described actions of cortisol on metabolism
• continued mobilization of glucose for central organs
• continued breakdown of alternative energy stores (lipids and proteins)

Question 440

general adaptation to stress: tertiary exhaustion response

Answer 440

• muscle wasting, hyperglycemia (diabetes mellitus)
• atrophy of the immune system
• vascular derangements

could be maladaptation to exposure of chronic stress
-this stage only comes int play in this situation

Question 441

the adrenal medulla

Answer 441

-essentially acts as an extension of the sympathetic nervous system

Question 442

catecholamine release from the adrenal medulla is largely under the control of the ____

Answer 442

SNS

Question 443

both catecholamines are sotred in ____ granules

Answer 443

chromaffin

Question 444

both catecholamines are the active ligands in the adrenergic system and they will bind to one of the 4 adrenergic receptors, what are they?

Answer 444

alpha 1 and 2, beta 1 and 2

Question 445

physiological effect of epinephrine

Answer 445

• rapid mobilization of the bodies energy reserves
• increase cardiac output and total peripheral resistance
• increase coronary and skeletal muscle anteriolar dilation
• reduce gut motility
• increases glycogenolysis in liver and muscle
• increased CNS alterness
• dilates pupils and flattens the lens
• increases sweating

Question 446

adrenoceptors: alpha 1

Answer 446

• most sympathetic target cells
• ligand affinity is higher in norepinephrine than epinephrine
• 2nd messenger = PLC
• ex: generalized anterior vasoconstriction

Question 447

adrenoceptors: alpha 2

Answer 447

• digestive system
• ligand affinity higher in norepinephrine than epinephrine
• 2nd messenger: decreased cAMP
• ex: decreased motility in digestive tract

Question 448

adrenoceptors: beta 1

Answer 448

• heart and kidney
• ligand affinity is equal in epineprhine and norepinephrine
• 2nd messenger: increase in cAMP
• ex: inotropic and chronotropic actions

Question 449

adrenoceptors: beta 2

Answer 449

• skeletal and smoothe muscle in some blood vessels and organs
• ligand affinity is higher in epinephrine than norepinephrine
• 2nd messenger = increase in cAMP
• ex: glycogen breakdown in skeletal muscle bronchiolar dilation and smooth muscle dilation in blood vessels nin the heart

Question 450

adrenoceptors: beta 3

Answer 450

• adipose tissue
• ligand affinity is higher in norepinephrine than epinephrine
• 2nd messenger = increase in cAMP
• ex: mobilises lipids for subsequent catabolism

Question 451

all adrenoreceptors are g-protein coupled receptors

true or false?

Answer 451

true

Question 452

epinephrine reversal

Answer 452

epinephrine can bind to different isoforms of the adrenergic receptor, causing completely different response (vasodilation vs vasoconstriction)

• this is due to numerous agonists/antagonists for adrenoreceptors
• phenylephrine is an antagonist specific for the alpha adrenoceptor, when it is blocked, epinephrine will bind to the beta receptor and cause the opposite response

Question 453

a stressor targets the ____ which causes an increase in CRH, which then targets the ______ and causes an increase in ACTH (from precursor peptide POMC) which then targets the _____ and releases cortisol

Answer 453

hypothalamus, anterior pituitary, adrenal cortex

Question 454

a stressor targets the hypothalamus, which activates the ______. it then stimulates the adrenal medulla which causes an increase in ______. This will target the endocrine pancreas (which increases glucagon release and decreases insulin release) or the ______ (this leads to vasoconstriction, decrease in renal blood flow, and increase in renin, angiotensin, and aldosterone).

Answer 454

sympathetic nervous system, epinephrine, arteriolar smooth muscle

Question 455

islets of langerhans and pancreatic hormones

Answer 455

• insulin and amylin: released from beta cells (10:1 ratio)
  0glucagon: released from alpha cells
• somatostatin: released from D or ? cells (weird s shape thing)
• pancreatic polypeptides: released from PP or F cells

-all these hormones are involved in regulating fuel metabolism and all act at multiple levels

Question 456

amylin

Answer 456

• released with insulin following a meal

- slows down the appearance of glucose in blood

Question 457

somatostatin

Answer 457

• released in response to increased glucose and amino acid levels
• D cells are always found in close association with alpha and beta cells (suggests paracrine role for somatostatin, regulating release of insulin and/or glucagon
• inhibits digestive and absorptive processes

Question 458

pancreatic polypeptide

Answer 458

• dramatic postprandial increase in plasma PP
• PP levels suppress SST levels and vice cersa
• D and F cells may be regulating each other (as well as alpha and beta cells)

Question 459

explain the glucose activation of insulin secretion from pancreatic beta cells after an increase in extracellular glucose

Answer 459

• this increase inititaes a series of events within the cell
• increase in ATP production within beta cells
• this inhibits K+ATPase channels
• this changes resting membrane potential
• results in L-type Ca++ channels opening, allowing Ca++ to flood into the cell
• Ca++ can do many things as a second messenger (one is to promote exocytocic release)
• enhances glucose uptake by cells

Question 460

fuel metabolism: fuel

Answer 460

carbohydrates, fats, proteins

Question 461

fuel metabolism: metabolism

Answer 461

a generalist term for the chemical reactions that occur in the body

Question 462

fuel metabolism: anabolism

Answer 462

the required energy input (ATP) and is the synthesis of larger macromolecules either for function or energy storage

Question 463

fuel metabolism: catabolism

Answer 463

• breakdown of macromolecules
• ex: hydrolysisL glycogen broken down to glucose
• ex: oxidation: glucose broken down to ATP

Question 464

the balance between anabolism and catabolism is not always straight forward. what are some exceptions?

Answer 464

• growth periods
• short and long term “gaps” in food intake
• absorptive (fed) and post-absorptive (fasted) states

Question 465

what causes glucose levels to go up?

Answer 465

• glucose absorption from digestive tract
• hepatic glucose production
  a) glycongenolysis
  b) gluconeogenesis

Question 466

what causes glucose levels to go down?

Answer 466

• transport of glucose into the cells
  a) energy production
  b) energy storage
• urinary excretion of glucose

Question 467

proinsulin is made of what

Answer 467

C-peptide (connecting peptide) and insulin (A chain and B chain)

Question 468

insulin - carbohydrates : facilitates glucose transport

Answer 468

facilitate glucose transport

• glucose cannot simply diffuse into cells it is transported by a family of proteins known as GLUT or by Na+ glucose co-transport
• GLUT-4 transports most of the circulating glucose during the absorptive state into skeletal muscle and adipose tissue
• GLUT-4 are housed in intracellular vesicles and are recruited onto the cell membrane in response to insulin
• in the post absorptive state glucose is transported out of the hepatocyte by GLUT-2 transporters
• in the absorptive state insulin facilitates conversion of glucose into glucose 6-phosphate to keep intracellular concentrations low

Question 469

in the absense of insulin, there are no ____ transporter in the membrane

Answer 469

GLUT-4

Question 470

in the fed state, insulin signals the cell to insert ____ transporters into the membrane, allowing glucose to enter the cell

Answer 470

GLUT-4

Question 471

in the fasted state, the hepatocyte makes glucose and transports itout into the blood, using ____ transporters

Answer 471

GLUT-2

Question 472

in the fed state, the glucose concentration gradient ______ and glucose enters the hepatocyte

Answer 472

reverses

Question 473

insulin - carbohydrates: inhibits glycogenolysis in the liver

Answer 473

• favoring carbohydrate storage

- hypoglycemic hormone = job to ensure that there is sufficient energy stored in your system

Question 474

insulin - carbohydrates: inhibits gluconeogenesis

Answer 474

-reduces circulating amino acids

Question 475

insulins action on fat

Answer 475

• inhibits lipolysis
• stimulates fatty acid uptake in adipose tissue
• stimulates glucose uptake and conversion to triglycerides

all of these actions promote removal of fatty acids and glucose from the blood and storage in adipose tissue

Question 476

insulins action on protein

Answer 476

• promotes amino acid uptake
• stimulates protein synthesis
• inhibits protein degradation

Question 477

insulin as the ONLY hypoglycemic hormone

Answer 477

• there is a positive relationship between blood glucose and amino acid concentrations and insulin concentration
• feed forward regulation by glucagon-like peptide-1 and gastric inhibitory peptide (anticipatory response when you’re about to eat)

Question 478

diabetes mellitus

Answer 478

-likely the most common endocrine disorder in the western world, literally means “honey running through”

Question 479

type 1 insulin-dependent diabetes

Answer 479

lack of insulin secretion

-normally seen in children and represents a small proportion of diabetics (normally genetically based)

Question 480

type 2 or non-insulin-dependent diabetes

Answer 480

lack of insulin sensitivity

-the most common form and invariably seen alongside obesity (80-90%)

Question 481

insulin deficiency can cause what 6 things?

Answer 481

1) increase in hepatic glucose output
2) decrease in glucose uptake by cells
3) decreased triglyceride synthesis
4) increased lipolysis
5) decreased amino acid uptake by cells
6) increased protein degradation

Question 482

explain the process of an increase in hepatic glucose output due to insulin deficiency

Answer 482

this causes hyperglycemia, glucosuria (increase in glucose in urine), osmotic diuresis (peeing a lot, get dehydrated), polyuria, dehydration (which leads to polydipsia or cell shrinkage), decrease in blood volume, peripheral circulatory failure (which leads to renal failure and death)

Question 483

explain the process of a decrease in glucose uptake by cells due to insulin deficiency

Answer 483

this causes either hyperglycemia (and following this, all the symptoms associated with this), or intracellular glucose deficiency, which leads to polyphagia (lots of eating)

Question 484

explain the process of a decrease in triglyceride synthesis or lipolysis due to an insulin deficiency

Answer 484

this leads to increase in blood fatty acids, alternative energy source utilisation, ketosis (ketone bodies in circulation - sweet smell in breath), metabolic acidosis (which leads to increased ventilation or diabetic coma which can lead to insulin shock), which leads to death

Question 485

explain the process of a decrease in amino acid uptake by cells due to a deficiency of insulin

Answer 485

this can cause an increase in blood amino acids, increase in gluconeogenesis, aggravation of hyperglycemia, which leads to the following symptoms associated witht his

Question 486

explain the process of an increase in protein degradation due to insulin deficiency

Answer 486

this can cause an increase in blood amino acids (and following symptoms) or muscle wasting which leads to weight loss

Question 487

what is glucagon’s relationship with blood glucose levels

Answer 487

there is a negative relationship b etween blood glucose levels and glucagon

Question 488

what is glucagon’s relationship with carbohydrates

Answer 488

carbohydrates stimulate hepatic glycogenolysis and gluconeogenesis (promoting the liberation of glucose into the circulation)

Question 489

what is fats relationship with glucagon

Answer 489

• glucagon promotes fat breakdown (lipolysis) and increase release of TG, DG and MG lipase’s from fats
• inhibits hepatic ketogenesis reducing FFA conversion to ketone bodies

Question 490

what are proteins relationship with glucagon

Answer 490

-glucagon promotes hepatic protein catabolism (trying to liberate energy sources)

Question 491

glucagon acts in the opposite way as insulin

true or false?

Answer 491

true

Question 492

feasting and fasting actions of insulin and glucagon

Answer 492

pancreatic alpha and beta cells respond in the opposite direction to sugars and fats in the blood but in the same direction in response to amino acids

-after eating a high protein meal, there’s an increase in blood amino acid concentration

beta cells: cause a increase in insulin, which promotes cellular uptake and assimilation of amino acids; increase in glucose uptake by cells which causes hypoglycemia; decrease in hepatic glucose output which causes hypoglycemia
(blood glucose remains normal)

alpha cells: cause an increase in glucagon, which causes an increase in hepatic glucose output, which leads to hyperglycemia
(blood glucose remains normal)

the actions of these balance eachother out