exam 2- muscle physiology, endocrine, reproductive Flashcards
what are the three types of muscle?
cardiac, skeletal, smooth
characteristics of cardiac muscle
striated (sarcoma), involuntary
characteristics of skeletal muscle
striated (sarcoma), voluntary
characteristics of smooth muscle
involuntary (no sarcoma)
the 4 properties of muscle are:
contractatility, excitability, extensibility, elasticity
contractility
the ability to generate force by contracting
excitability
the ability to respond to a stimulus (this is often from a motor neuron)
extensibility
stretch beyond resting length without being damaged
elasticity
ability to return to resting length after being stretched
what is the primary function of all muscle?
to generate force
what is the secondary function of skeletal muscle?
to maintain posture, stabilize joints, generate heat (shivering)
how are skeletal muscles attached to bones?
via tendons
what causes joint movement?
muscle tension on the tendon
origin of the muscle
the part of the muscle that is closer to the body. this part remains immobile during the action
insertion of the muscle
the part of the muscle that is farther from the body. this part moves during the action
what is the tendon connected to?
the bone on one end, and epimysium on other end
structure of the muscle, from smallest part to biggest:
muscle cell (fiber), endomysium (between the cell fibers), fasicle (wraps a group of fibers), perimysium (wraps the fasicles in groups), epimysium (wraps around the perimysium) and is attached to tendon, which is attached to bone
what does a parallel arrangement of fascicles tell you?
works for range of motion
what does a pennate arrangement of fascicles tell you?
works for power. you can fit more muscle cells into a space that is pennate vs parallel. more muscle cells = more force = power
where is calcium stored in the myofiber?
sarcoplasmic reticulum
what is the importance of the t-tubule in the myofiber?
propogates action potentials into the interior of the cell
what is the sarcomere?
it is the functional unit of muscle contraction. it gives rise to the striated appearance of cardiac and skeletal muscles
z-disk
protein structure that serves as a point of attachment for the thin myofilament. from one z-disk to another = one sarcomere
m-line
in the middle. a protein structure that acts as a place of attachment for the thick myofilaments
a-band
the length of the thick myofilament
what is the largest protein in the body?
titin
what is the thin myofilament made out of?
actin, wrapped in tropomyosin
h-band
the length from the end of one thin myo to the start of the next thin myo
what happens in the sarcomere as the muscle contracts?
thin filaments slide between thick filaments. the distance between the z-disks shortens. the I-band (which is the part that is thin filament between z-disks of dif. sarcomeres) completely disappears. the h-band shortens. the a-band does not shorten
sliding filament mechanism
imagine the thin myofilament (purple helix balls) above the thick myofilament (green stripes with heads). the myosin head is ATPase and has an ATP bonding site. it is currently in the kinked position. as ATP binds, myosin undergoes hydrolysis and the head extends to a non-kinked postion. the ATP has now turned into inorganic phosphate and ADP. the actin binding site has binded the myosin head to the actin on the thin myofilament. the connection that was just made is called a cross bridge.
power stroke mechanism
now that the myosin head is binded to the actin, inorganic phosphate may leave. the action of inorganic phosphate leaving is called a power stroke. it brings it back to kinked position, but still bonded to the actin. the sarcomere shortens as the thick myofilament pulls the thin closer to the middle
how do we regulate muscle contraction?
when the muscle is relaxed, tropomyosin blocks the binding site on actin, remember, tropomyosin is the string that is attached and runs the span of the thin myofilament. troponin can displace tropomyosin, therefore exposing the actin active site and allow for cross bridge attachment. calcium will bind to troponin, which causes a conformational change, which is what allows for the active actin site to be exposed
how are calcium levels regulated?
this is the process of excitation-contraction coupling
motor unit
each motor neuron plus the muscle fiber it makes contact with
neuromuscular junction
where contact is made between motor neurons and muscle fibers
characteristics of motor neurons
they are all or none, meaning that when the motor neuron is activated, ALL of the muscle fibers that it is connected to become depolarized. depolarization is what allows for muscle contraction
innervation ratio
motor neuron : muscle fiber
eye muscles 1:20
calf muscles 1:2000
some things need more/bigger movements and power
how is an action potential generated?
- the motor neuron action potential drives down the axon. 2. because of the depolarization from the last step, the voltage gated calcium channels open and calcium enters. 3. calcium forms into ACh vesicles which get released and bind to acetylcholinesterase. 4. the ACh binding opens ion channels. 5. sodium enters through the opened channels. 6. the positive charge from sodium travels as a local current through the muscle plasma membrane. 7. this charge go through voltage gated sodium channels, which propogate action potentials
steps of excitation-contraction coupling
(in somatic motor neuron). somatic neuron gets activated.
ACh gets released
(in sarcolemma) ACh binds to nicotinic ACh receptors, opens ligand gated channels. sodium diffuses in, producing a depolarizing stimulus of the muscle membrane. an action potential is produced.
(in transverse tubules) action potential are conducted about the tubules. action potentials open the voltage gated calcium channels.
(in sarcoplasmic reticulum) calcium release channels open. calcium diffuses out into sarcoplasm
(in myofibrils) calcium binds to troponin, stimulating contraction
what must happen for muscle relaxation?
action potentials must stop. calcium release channels close. calcium gets pumped back into SR via calcium atpase pumps
what is a twitch
single contraction of muscle. the muscle quickly contracts and relaxes
what is on the twitch graph
action potential, calcium concentration, force
what is a tetanus
there is a high frequency of action potentials that lead to the max amount of force a muscle can generate. muscle is stimulated repeatedly. no relaxation between action potentials.
what does the length tension relationship describe?
the relationship between the size of the sarcomere and the ability to generate force
what is the optimal amount of overlap?
2.0-2.25 um
what happens when the percentage of rest length is shorter than the optimal amount of overlap?
at 1.65, steric hinderance causes a disrupted spacing sue to maximal overlap
what happens when the percentage of rest length is too long?
there will be no overlap. no overlap means the thin and thick can’t reach each other, which means that there is no chance of creating cross bridges, meaning no force can be generated
what are the types of muscle contractions?
isometric & isotonic (which branches into concentric and eccentric)
isometric contraction
muscle length remains constant. you are generating max force. the load is greater than the force. this is like trying to push a parked car.
concentric contraction
active shortening. think CONcentric = CONcise
the muscle shortens with contraction. the force of the contraction exceeds the load. this is when you’re curling a dumbbell and you are lifting your arm up
eccentric contraction
active lengthening. think Eccentric = Elongating
the muscle lengthens with contraction. the load may exceed the force of contraction. this is when you are curling a dumbbell and your arm is going down
what are the determinants of isometric force?
activation frequency, motor unit recruitment, muscle size, sarcomere length
activation frequency
this is how fast the action potentials are being generated (think twitch vs tetanus). a higher activation frequency= more calcium being released from SR, which allows for more cross bridge formation, which allows for higher force
motor unit recruitment
this dictates how much force is being generated. not every movement needs to be a big movement. if you’re flicking something you will recruit more motor units than if you are pushing something
force velocity curve. velocity = distance the muscle shortens / time
as the load increases, the velocity decreases. this makes sense. you can shorten and extend your muscle quicker when you are curling 5lbs compared to 200 lbs
when does the force velocity curve show the maximum shortening velocity?
at 0 load
when does the force velocity curve show the maximum isometric tension?
at 0 shortening velocity. this makes sense. this is when you cant move (like trying to push a car)
what are the 3 energy systems that create ATP needed for myosin and calcium pumping?
phosphagen, glycolytic, aerobic
phosphagenic system
is able to generate/resynthesize ATP at the fastest rate possible. but, creates a limited amount of phosphocreatine. this is what is employed during a 10 second sprint. rapidly converts ADP to ATP
look for PCr domination
glycolytic system
is able to generate/resynthesize ATP at 80% intensity, which can last a few minutes. this is what is employed in a 400 m swim
look for glycolysis domination
aerobic system
is able to generate/resynthesize ATP at a lower intensity, but is virtually unlimited. this is what is employed in marathon runners. occurs in the mitochondria (where glucose and fats are converted to ATP). consumes oxygen. by-product=co2,h20,heat
look for oxidative domination
how do we classify between a slow twitch and a fast twitch fiber?
the contraction speed
what type of fiber is a slow twitch?
type 1
what type of fiber is a fast twitch?
type 2 (2 types of this, 2a & 2x)
what color are slow twitch fibers (type 1)
red
do slow twitch fibers have a lot or a little capillaries/myoglobin?
Many
do slow twitch fibers have a lot or a little mitochondria?
many. high oxidative capacity
are slow twitch fibers resistant to fatigue?
yes, they are common in endurance muscles
why are fast twitch fibers called fast?
they have a fast contraction time
what is the most predominant type of fast twitch fibers?
type 2a
do fast twitch fibers have a lot or a little mitochondria?
many, but not as many as slow twitch
are fast twitch type 2 fibers resistant to fatigue?
yes
what color are fast twitch type 2x fibers?
white, because they lack myoglobin
what do fast twitch 2x fibers store a lot of ?
glycogen
do fast twitch 2x fibers have a lot of or a little capillaries and mitochondria?
little
what is the function for fast twitch 2x fibers?
sprint tasks
type 1 diameter
small
type 1 z-line thickness
wide
type 1 glycogen content
low
type 1 resistance to fatigue
high
type 1 capillaries
many
type 1 myoglobin content
high
type 1 respiration
aerobic
type 1 oxidative capacity
high
type 1 glycolytic ability
low
type 1 twitch rate
slow
type 1 myosin ATPase rate
low
type 2a diameter
intermediate
type 2a z-line thickness
intermediate
type 2a glycogen content
intermediate
type 2a resistance to fatigue
intermediate
type 2a capillaries
many
type 2a myoglobin content
high
type 2a respiration
aerobic
type 2a oxidative capacity
high
type 2a glycolytic ability
high
type 2a twitch rate
faster
type 2a myosin ATPase rate
higher
type 2x diameter
large
type 2x z-line thickness
narrow
type 2x glycogen content
high
type 2x resistance to fatigue
low
type 2x capillaries
few
type 2x myoglobin content
low
type 2x respiration
anaerobic
type 2x oxidative capacity
low
type 2x glycolytic ability
high
type 2x twitch rate
fastest
type 2x myosin ATPase rate
highest
what type of stem cell is a satellite cell?
multipotent. it is restricted to muscle cells
Duchenne Muscular Dystrophy
- most common form of dystrophy
- it is recessive and linked to the x (which is why its more common in boys)
- the mutation lies in the dystrophin gene, which is the gene that provides structural stability to the cell membrane
symptoms of DMD
- symptoms may first appear at ages 2-3
- muscle weakness in legs and pelvis due to muscle mass loss
- pseudo hypertrophy (it looks like the muscles are getting bigger, but really fat fibrotic tissue is replacing the muscle)
- life expectancy is 30 due to paralysis
how are cardiac muscle cells joined together?
by gap junctions
how does action potential travel through cardiac muscle cells?
by gap junctions
how do the cells behave in a cardiac muscle cell?
as one unit (syncitium)
how does EC coupling in the heart happen?
via calcium induced calcium release
do smooth muscle cells have sarcomeres?
no, not striated
what is the ratio of actin to myosin in smooth muscle cells?
16:1 (more thin myos than thick myos). hence not an every other pattern that we can see in the cardiac and skeletal muscles
what are the actin filaments attached to in smooth muscles?
dense bodies (en vez de zdisk)
do smooth muscles have more or less opportunity to form cross bridges?
more, they have more actin
the steps of smooth muscle contraction are:
- stimulated by a rise in intracellular calcium
- this calcium then binds to calmodulin
- this calcium-calmodulin complex activates the myosin light chain kinase
- this makes the myosin heads be phosphorylated
- then, myosin heads bind to the actin
- relaxation will occur when calcium decreases
what is endocrinology
the branch that is concerned with glands that secrete hormones into the blood
what does impaired endocrine function lead to?
higher morbidity and mortality. someone with diabetes has a higher risk for many other damages and concerns
what are the 6 endocrine glands?
pancreas
hypothalamic-pituitary
thyroid-parathyroids
adrenals
male gonads
female gonads
what are the 2 communication systems that are used for maintaining the body’s homeostasis?
nervous system and endocrine system
what is the functional unit of the endocrine system?
a gland cell
what is the chemical messenger of the endocrine system?
hormone
what is the mode of transmission for the endocrine system?
circulation (via blood)
what is the reaction time for the endocrine system?
minutes-days
analogy you can use for the endocrine system and how it affects the body
is it like the wifi connection. it affects every device it is connected to.
what is a hormone
a chemical messenger from a ductless gland
where do endocrine hormones travel?
in the blood to communicate with their target cells in every corner of the body
what are the 4 things that can happen to a hormone that is circulating in the blood?
- excreted in urine or feces
- inactivated by metabolism
- activated by metabolism
- binds to receptor of target cell and create a cellular response
what does the concentration of the hormone in blood reflect?
the secretion rate by the gland cell, the excretion rate, and activation rate
how do we group endocrine hormones?
based on its polarity, either polar (hydrophilic) or non-polar (hydrophobic)
hydrophilic (polar) hormones
catecholamine
peptide/protein
hydrophobic (non-polar) hormones
thyroid
steroid
vitamin D
where are hydrophilic hormones stored?
secretory vesicles. released after stimulation
how do hydrophilic hormones travel in the blood?
free of proteins. hydrophilIC they get the ICK
what do hydrophilic proteins bind to?
trans-membrane receptor proteins. they cant make it through the plasma membrane, so must be trans membrane
how are catecholamine hormones secreted?
by sympathetic neurons and adrenal medulla: dopamine, norepinephrine, and epinephrine
synthesis of catecholamine:
tyrosine > tyrosine hydroxylase > dopa > tyrosine hydroxylase > dopamine > tyrosine hydroxylase > norepinephrine > tyrosine hydroxylase > epinephrine
2 pathways for catecholamine
1) ACh gets secreted into the ganglion. it binds to the nicotinic receptor on the post ganglionic neuron. norepinephrine gets released in the nerve ending
2) ACh gets secreted into the adrenal medulla. norepinephrine and epinephrine get released into the blood vessel/stream
is the half life of catecholamine short or long? why?
short. there are enzymes in the blood that are destructive. because ceta travels in the blood by itself, it gets destroyed quickly
what does catecholamine do
bind trans-membrane receptor proteins (G protein coupled receptors) > activate enzymes (adenylyl cyclase) and produce 2nd messengers (cAMP) > evoke a rapid response
examples of peptide/protein hormones
insulin, prolactin
how are peptide/protein hormones synthesized?
via transcription-translation
where are peptide/protein hormones stored?
secretory vesicles
what are the 3 transmembrane receptors for peptide hormones?
GPCR, tyrosine kinase, JAK
example of GCPR (g coupled protein receptor) for peptide hormone
glucagon-R, ACTH-R
example of tyrosine kinase receptor for peptide hormones
IGF 1-R, insulin-R
example of JAK kinase receptor for peptide hormones
GH-R, Leptin-R, PRL-R
GPCR (peptide hormone)
generation of second messenger
tyrosine kinase receptor (peptide hormone)
autophosphorylation - none for JAK (he aint got JAK shit)
what do GPCR, TKR, and JAK all lead to?
activation of cellular kinase and cellular response
summary of catecholamines:
- hydrophilic
- secreted by neurons and adrenal medulla
- synthesized through enzymatic reactions from tyrosine
- stored in secretory vesicles
- secreted in response to secretagogue (stimulus)
- binding and activating G-protein coupled receptors
- evoke a rapid response in a target cell
summary of protein/peptide hormones:
- hydrophilic
- synthesized through transcription translation (think- this process ends in protein production, duh)
- stored in secretory vesicles
- secreted in response to secretagogue (stimulus)
- binding and activating transmembrane receptors (GCPR, TKR, or JAK)
- evoke a rapid response in a target cell
examples of hydrophobic hormones
thyroid, steroid, vitamin D (these cannot be stored, meaning they are made on demand)
how do hydrophobic hormones circulate in the blood?
mostly protein-bound. small amount of free hormones
what does the free hormone do and why is it important?
it diffuses across the PM of the target cell. it is the only one that can do this. they modulate the rate of transcription
what do hydrophobic hormones do?
bind and activate their specific intracellular receptor proteins and change the rate of transcription of their target genes
how are thyroid hormones (T3&T4) secreted?
via thyroid gland
how are thyroid hormones created?
from enzymatic reactions from tyrosine, which requires iodine ingestion
what do thyroid hormones do in plasma?
bind liver-produced proteins
(thyroxine-binding globulin)
what do thyroid hormones do in target cells?
bind intracellular thyroid hormones receptors and alter transcription
what do thyroid hormones do in the liver?
they are modified. they become hydrophilic and get excreted
T4 thyroid hormone
most abundant
most stable
pro-hormone form
T3 thyroid hormone
most potent. the active hormone. you want to convert T4 to T3
how are steroid hormones secreted?
by:
adrenal glands
ovaries
testes
how are steroid hormones made?
from cholesterol
what is the rate limiting enzyme for steroid hormones?
P450 SCC
what do steroid hormones do in plasma?
bind liver produced binding globulins
what do steroid hormones do in target cells?
bind their specific intracellular receptor proteins
what do steroid hormones do in the liver?
become modified, hydrophilic, excreted
summary of thyroid hormones:
- hydrophobic
- synthesis involves enzymatic incorporation of iodide onto tyrosine
- not stored (made on demand)
- bind intracellular receptors, ligand-induced transcription factors
- slow cellular response that involves changes at transcription translation
- metabolized for increased solubility and excreted
summary of steroid hormones:
- hydrophobic
- synthesis involves enzymatic reactions from cholesterol
- not stored (made on demand)
- bind intracellular receptors, ligand-induced transcription factors
- slow cellular response involving changes at transcription translation
- metabolized for increased solubility and excreted
summary of vitamin D:
- hydrophobic
- synthesis involves enzymatic activation to 1,25-dihydroxy-vitamin D
- not stored (made on demand)
- bind intracellular receptors, ligand-induced transcription factors
- slow cellular response involving changes at transcription translation
- metabolized for increased solubility and excreted
what are the catecholamine hormones?
dopamine
norepinephrine
epinephrine
what are the thyroid hormones?
T3
T4
what are the steroid hormones?
estrogen
progesterone
testosterone
DHT
androstenedione
cortisol
aldosterone
DHEA
what is the vitamin D hormone?
calcitriol
the hormone __________ is derived from cholesterol
cortisol
which hormones is hydrophilic and circulates free of proteins in the plasma?
TSH (thyroid stimulating hormone)
which hormone is synthesized by trasncription-translation process?
insulin
a patient with a lower sensitivity to insulin would require _______ insulin for the same response
more
T/F
receptors for all of the hormones are proteins
true
this modified amino acid is an example of a catecholamine
epinephrine
this hormone is derived from cholesterol
aldosterone, cortisol
this hormone’s receptor leads to the changed production of cAMP
epinephrine, TSH
this hormone is carried in plasma by liver produced binding globulins
aldosterone, cortisol, thyroid hormone
this hormone is not a steroid but acts on intracellular receptors
thyroid hormone
this hormone’s receptor is a transcription factor
aldosterone, cortisol, thyroid hormone
this hormone is hydrophilic and circulates free in plasma
insulin, epinephrine, prolactin, TSH
T/F
an estrogen priming which increases the synthesis of the receptor for progesterone is required for progesterone effects. this is known as additive effects
false
T/F
a prolonged presence of a hormone at a high concentration may decrease its receptors in target cells. this is known as down-regulation
true
compared to a normal subject, a person with type 2 diabetes mellitus has lower sensitivity to insulin and requires __________ insulin for the same response
more
what do blood glucose levels do after each meal?
they peak
what hormone do insulin and glucagon belong to?
peptide
is glucagon an alpha or beta cell
alpha
is insulin an alpha or beta cell
beta
how many kcal/g for carbohydrate?
4
how many kcal/g for fat?
9
how many kcal/g for protein?
4
where is energy stored? (3 places)
fat
carbohydrate
protein
what is anabolism?
the building up/storing of energy
what is catabolism?
the breaking down/releasing of stored energy
what is carbohydrate stored as?
stored as glycogen in the liver and muscle
what is fat stored as?
stored as triglyceride in adipocytes
*most abundant
*most efficient
where is protein stored?
muscle. *remember that this is only available for long term fasting
timeline of absorptive state
(fed state) 4 hours after meal
timeline of post-absorptive phase
(fasting state) period 4 hours after meal until next one
what is happening with energy in the absorptive phase?
use energy, store energy
what is happening with energy in the fasting state?
mobilize and release energy
levels of glucose, insulin, and glucagon during the fed state
glucose: high
insulin: high
glucagon: low
what does insulin do for anabolism and catabolism?
stimulates anabolism
inhibits catabolism
anabolism process
building blocks -> organic macromolecules
this is stimulated by elevated levels of insulin
what does the combo of high insulin and low glucagon promote and inhibit?
promotes anabolism
inhibits catabolism
*this makes sense, this combo is seen during the absorptive (fed) state, and this is when energy gets used/stored. you wouldnt be breaking it down (catabolism) while youre eating
ended on pg 129 of notes
