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PHGY 209 > 8. Muscle/ANS > Flashcards

8. Muscle/ANS Flashcards

1
Q

3 types of muscle

A
  • skeletal muscle
  • cardiac muscle
  • smooth muscle
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2
Q

skeletal muscles purpose

A

used for posture and locomotion, enabling our arms and legs to contract under voluntary control

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3
Q

cardiac muscles purpose

A

responsible for rhythmic contractions of the heart

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4
Q
A
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4
Q

smooth muscles purpose

A

cause involuntary contraction in blood vessels, gut, bronchi, uterus etc…

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5
Q

tendon

A

attaches muscle to bone

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6
Q

joint

A

point where two bones meet, where tendon is attached

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7
Q

skeletal muscle contraction tendons/joint

A

contraction pulls on tendons, which pull on joint, causing the flexion of joints

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8
Q

muscle fiber is aka

A

muscle cell

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9
Q

muscle cell

A

long, thin cells extending throughout the entire muscle

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10
Q

fascicle

A

bundle of muscle fibers

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11
Q

skeletal muscle characteristics

A
  • multinucleated
  • striated: highly ordered structure
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12
Q

how is the highly ordered structure of muscle fibres beneficial?

A

allows for simultaneous contraction of muscle fiber

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13
Q

why are muscle fibers multinucleate?

A

they originate from myoblasts (1 nucleus each) which fuse together

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14
Q

advantage of multinucleation

A
  • multiple sites of mRNA and protein synthesis
  • more copies of a gene = more proteins generated
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15
Q

myofibrils

A

long, thin fibers made of proteins, found in muscle fiber

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16
Q

I band corresponds to

A

light band, thin filaments

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17
Q

A band corresponds to

A

overlap between thick and thin filaments

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18
Q

Z line is

A

the dark strip in middle of the I band

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19
Q

sarcomere

A
  • the distance between 2 Z lines
  • contractile unit of skeletal muscle
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20
Q

sarcomere contracts –>

A

myofibril contracts –> muscle fiber contracts

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21
Q

M line

A

in middle of A band, holding thick filaments together

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22
Q

the I band contains only

A

thin filaments

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23
Q

the H zone contains only

A

thick filaments

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24
Q

where is the H zone?

A

in the middle of A band

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25
Q

crossbridges

A

myosin head groups extending out from thick filaments, interacting with thin filaments

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26
Q

where do thick and thin filaments overlap?

A

dark A band zone

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27
Q

each thick filament is surrounded by…

A

6 thin filaments

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28
Q

each thin filament is surrounded by…

A

3 thick filaments

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29
Q

thin filaments are made of?

A

actin -> 2 chains of globular actin subunits

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30
Q

thick filaments are made of?

A

myosin -> 2 myosin bundles brought together with heads in opposite directions

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31
Q

actin:

A

small globular + soluble protein which can bind to itself to form long actin filaments

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32
Q

myosin:

A

fibrous protein composed of a long, thin fiber + 2 head groups

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33
Q

myosin bundles

A

myosin molecules brought together with heads facing same direction

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34
Q

what drives the cross bridge cycle

A

ATP binding and hydrolysis by the myosin head group

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35
Q

cross bridge cycle

A
  1. myosin head bound w ATP
  2. ATP hydrolysis generates ADP+Pi, causing myosin head to become cocked
  3. myosin head binds to actin causing Power stroke
  4. conformational change triggered, causing ADP+Pi to fall off
  5. ATP binds to myosin head so myosin dissociates from actin filament
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36
Q

what causes the power stroke?

A

myosin heads binding to actin filament and ADP+Pi falling off

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37
Q

what causes Rigor mortis?

A

too much calcium in the cell

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38
Q

what happens to the myosin head group when ATP is added?

A

it dissociates from the actin filament

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39
Q

what purpose does ATP hydrolysis have in cross-bridge cycle?

A

change the ATP-bound myosin head conformation to its active/cocked position

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40
Q

where is the motor neuron soma located?

A

ventral horn of spinal cord

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41
Q

where is the motor neuron axon located?

A

goes out through the ventral root of spinal cord

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42
Q

motor unit

A

a motor neuron and the group of muscle fibers it innervates

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43
Q

where are the synapses of muscle fibers located?

A

in the middle of their length

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44
Q

what is special about the motor unit?

A

a single motor neuron makes synapses with many muscle fibers

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45
Q

neuromuscular junction

A

synapse of muscle fibers

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46
Q

neurotransmitter at neuromuscular junction

A

acetylcholine

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47
Q

receptor at neuromuscular junction

A

nicotinic acetylcholine receptors (nACh)

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48
Q

nACh can be activated by…

A

Acetylcholine and nicotine

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49
Q

End Plate

A

post-synaptic terminal of neuromuscular junction, specialised to muscle fibers with junction folds

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50
Q

where are the nACh receptors found?

A

in the End Plate

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51
Q

neuromuscular transmission

A
  1. action potential in motor neuron propagates down axon, depolarise the presynaptic membrane
  2. acetylcholine is released at presynaptic terminal
  3. ACh binds to nACh receptors, activating them so Na+ flows through nACh receptors, depolarising the end plate
  4. endplate potential generated is big enough to fire an AP on its own
  5. voltage-gated sodium channels in endplate activated cause fiber AP to propagate in both directions fast for muscle fiber contraction
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52
Q

what are nACh receptors permeable to?

A

Na+

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53
Q

Endplate potential

A

ie. EPSP in a muscle fiber

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54
Q

why is a single endplate potential so big?

A

the synapses are very large

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55
Q

T-tubules

A

invaginations in muscle fiber plasma membrane

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56
Q

Sarcoplasmic Reticulum (SR)

A

intracellular storage site for calcium, forming a network around myofibril

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57
Q

ryanodine receptors

A
  • ion channel embedded in SR membrane
  • activated by ryanodine binding
  • permeable to Ca2+ when activated
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58
Q

DHP receptor

A

voltage-gated calcium channel on muscle fiber external plasma membrane

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59
Q

excitation-contraction coupling key points

A
  • external plasma membrane filled with Na+ voltage-gated channels
  • AP propagates along plasma membrane to t-tububles
  • t-tubule membrane depolarised, activating DHP receptors
  • conformational change in DHP receptors allows its coupling to Ryanodine receptors
  • Ca2+ influx from SR into cytoplasm
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60
Q

which ion channel releases bigger amounts of Calcium? DHP or ryanodine?

A

ryanodine since embedded in SR membrane

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61
Q

troponin

A

globular proteins found along actin filament length

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62
Q

troponin gets activated by…

A

the binding of Ca2+

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63
Q

tropomyosin

A

long thin protein wrapped around actin filament

64
Q

tropomyosin conformation at rest

A

covers all the binding sites for myosin heads

65
Q

how is excitation-coupling linked to the cross bridge cycle?

A
  1. calcium released from SR binds to troponin
  2. troponin changes conformation
  3. causing tropomyosin to move away from myosin binding sites on actin
  4. myosin head groups can now bind to actin filament and cross-bridge cycle can begin
66
Q

twitch

A

contraction of muscle fiber in response to a single action potential

67
Q

latent period

A

muscle contraction lags behind the muscle AP due to delays associated with excitation-contraction coupling

68
Q

why does muscle contraction take about 100ms to relax back to normal state?

A

time taken for Ca2+ conc to return to normal

69
Q

tension

A

force generated by a muscle

70
Q

recruitment

A

increase in number of active fibers

71
Q

summation

A

additive effects of several closely spaced twitches

72
Q

what controls the tension exerted by a whole muscle?

A

recruitment and summation

73
Q

tetanus

A

sustained muscle fiber contraction due to motor neurons firing APs in bursts
-> Ca2+ has no time to be pumped back into SR

74
Q

most important mechanism for increasing muscle tension

A

recruitment of additional motor units

75
Q

how is ATP concentration maintained stable during muscle contraction?

A
  1. ATP hydrolysis
  2. Creatine phosphate donates its phosphate to ADP with the help of Creatine kinase to form ATP
  3. anaerobic respiration: glycolysis –> glucose and glycogen converted to lactic acid in cytoplasm
  4. aerobic respiration: oxidative phosphorylation –> oxygen + fatty acids generate lots of ATP in mitochondria
76
Q

where does glycolysis take place?

A

cytoplasm

77
Q

where does oxidative phosphorylation take place?

A

mitochondria

78
Q

enzyme used to convert ADP to ATP

A

creatine kinase

79
Q

glycogen

A

long chains of glucose molecules

80
Q

how do muscle fibres store energy?

A

as glycogen

81
Q

fast glycolytic fibers key points

A
  • myosin with high ATPase activity
  • no myoglobin
  • generation of large force over short time
  • fatigue rapidly
  • energy mostly from glycolysis, causing lactic acid to build up
  • not dependent on blood supply
82
Q

generation of large force over short period of time

A

fast glycolytic fibers

83
Q

fast glycolytic fibers color

A

white, lack myoglobin

84
Q

slow oxidative fibers key points

A
  • myosin with low ATPase activity: ATP consumed more slowly
  • myoglobin to facilitate oxygen transport from blood
  • generation of little force over long time
  • use both glycolysis and oxidative phosphorylation
  • depends on blood supply
85
Q

generation of little force over long period of time

A

slow oxidative fibers

86
Q

purpose of myoglobin in slow oxidative fibers

A

to facilitate oxygen transport from blood, facilitating oxidative phosphorylation

87
Q

slow oxidative fibers color

A

red, myoglobin

88
Q

fast oxidative fibers key points

A
  • intermediate properties
  • fast myosin and oxidative metabolism
89
Q

order in which muscle fibers are recruited as contraction gets stronger

A
  1. slow oxidative
  2. slow oxidative + fast oxidative
  3. slow oxidative + fast oxidative + fast glycolytic
90
Q

muscle fatigue purpose

A

to protect muscles from damage

91
Q

muscle fatigue is caused by depletion of ATP. True/False?

A

False

92
Q

causes of fatigue in fast glycolytic fibers

A
  • changes in ion gradients
  • reduction in pH due to build of lactic acid from glycolysis
93
Q

cause of fatigue in slow oxidative fibers

A

depletion of glycogen

94
Q

other possible cause of muscle fatigue

A

central command fatigue

95
Q

central command fatigue

A

failure of command signals from CNS due to fatigue = less motivation to continue

96
Q

hypertrophy

A

increase muscle size as the fast glycolytic muscle fibers get thicker, since they contain more myosin

97
Q

hypertrophy results from which type of exercise

A

high intensity and short duration
-> fast glycolytic fibers

98
Q

how does low intensity and long duration exercise change muscles?

A
  • slow oxidative fibers become more efficient at generating energy: increased mitochondria in muscle fibers
  • stronger cardiovascular system
99
Q

why are muscles sore after exercise?

A

due to inflammation in response to small muscle damage

100
Q

muscle cramps cause

A

dehydration changes ionic concentrations so muscle fiber becomes abnormally depolarised, generating more AP for muscle contraction

101
Q

Smooth muscle contraction controlled by… why?

A

the ANS to maintain stable internal states

102
Q

differences/similarities between smooth and skeletal muscles

A
  • no striation: not highly ordered
  • similar contraction mechanism: myosin filaments pull on actin filaments
103
Q

smooth muscle activation steps

A
  1. Ca2+ released from SR or membrane calcium channels
  2. Ca2+ binds to calmodulin, activating it
  3. calmodulin activates myosin light chain kinase which phosphorylates/activates myosin
  4. muscle contracts
104
Q

calmodulin

A

soluble protein floating inside cell, activated by calcium binding

105
Q

kinase proteins

A

proteins that activate other proteins by adding phosphate to them

106
Q

how is smooth muscle contraction similar to skeletal muscle contraction?

A

it is activated by calcium release in SR

107
Q

how is smooth muscle contraction different to skeletal muscle contraction?

A
  • calcium can also be released from calcium channels in the membrane
  • calcium binds to calmodulin, not troponin
108
Q

activity of smooth muscles is regulated by…

A

extracellular signals, such as hormones and neurotransmitters of ANS

109
Q

the Autonomic Nervous System function(s)

A
  • to control visceral organs
  • to maintain homeostasis
110
Q

3 major divisions of the ANS

A
  • Sympathetic
  • Parasympathetic
  • Enteric
111
Q

ganglion

A

organised cluster of neuron cell bodies in PNS

112
Q

sympathetic nervous system

A

activated in energy fight or flight reactions

113
Q

sympathetic preganglionic neurons anatomy

A
  • short axon extending out through ventral root
  • axon synapses with postganglionic neuron
114
Q

where are sympathetic preganglionic neurons found?

A

in spinal cord grey matter

115
Q

sympathetic postganglionic neurons anatomy

A

have long axons projecting to visceral organ

116
Q

sympathetic ganglia

A

found at the synapse between sympathetic preganglionic and postganglionic neurons between thoracic and lumber regions of spinal cord
–> form a chain so they all get activated together

117
Q

how does the sympathetic nervous system work?

A
  1. preganglionic neurons release acetylcholine at synapse with postanglionic neuron
  2. acetylcholine activates nACh receptors, causing Na+ to flow in and postganglionic neuron depolarisation
  3. norepinephrine released, activating alpha and beta adrenergic receptors
  4. 2nd messenger released, innervating the target organ
118
Q

sympathetic effect on heart

A

heart muscles contract more and faster

119
Q

sympathetic effect on bronchial tubes

A

smooth muscles relax, allowing for more space in lungs to breathe

120
Q

neurotransmitter released by sympathetic preganglionic neurons

A

acetylcholine

121
Q

neurotransmitter released by sympathetic postganglionic neurons

A

norepinephrine

122
Q

alpha and beta adrenergic receptors

A
  • metabotropic receptors
  • activated by norepinephrine
  • have different effects depending on the target organ
123
Q

parasympathetic nervous system

A

involved in rest and digest processes

124
Q

parasympathetic preganglionic neuron anatomy

A

long axons that extend almost to target organ

125
Q

where are parasympathetic preganglionic neurons found?

A
  • brainstem (cranial nerves)
  • sacral spinal cord
126
Q

parasympathetic postganglionic neuron anatomy

A

close to target organ so very short axons

127
Q

vagus nerve (X)

A

cranial nerve providing preganglionic parasympathetic input to visceral organs

128
Q

how does the parasympathetic nervous system work?

A
  1. preganglionic neurons release acetylcholine at synapse with postganglionic neuron
  2. acetylcholine activates nACh receptors so Na+ flows in, depolarising postganglionic neuron
  3. acetylcholine released by postganglionic neuron, activating muscarinic acetylcholine receptors
  4. 2nd messenger activate in target tissue
129
Q

sympathetic effect on heart

A

heart contractions slow down

130
Q

neurotransmitter released by parasympathetic preganglionic neurons

A

acetylcholine

131
Q

neurotransmitter released by parasympathetic postganglionic neurons

A

acetylcholine

132
Q

muscarinic acetylcholine receptors

A
  • metabotropic receptors
  • activated by acetylcholine
  • parasympathetic response
  • effects depend on target organ
133
Q

enteric nervous system

A

controls gastrointestinal tract + pancreas + gallbladder

134
Q

2 functions of enteric nervous sytem

A
  • control contractions to mix and push food through dig. tract
  • secrete dig. enzymes
135
Q

the enteric system can function on its own. True/False

A

True, but it also receives input from sympathetic and parasympathetic systems for regulation

136
Q

neurons in enteric system

A
  • cholinergic neurons
  • adrenergic neurons
  • neurons that release neuropeptides, ATP and Nitrous Oxide
137
Q

cholinergic neurons

A

activate peristaltic contractions of the gut

138
Q

adrenergic neurons

A

suppress gut peristalsis to focus on smth more important (sympathetic influence)

139
Q

intestine layers

A

2 layers of smooth muscles
- longitudinal
- circular

2 layers of neurons
- myenteric plexus
- submucous plexus

140
Q

longitudinal smooth muscles

A

vertical contractions

141
Q

circular smooth muscles

A

circular contractions

142
Q

myenteric plexus

A

neuron layer innervate the 2 layers of smooth muscles in intestine

143
Q

submucous plexus

A

neuron layer that regulates secretion of digestive enzymes

144
Q

sources of sensory input to ANS

A
  • somatosensory system
  • vagus nerve or spinal cord
145
Q

brainstem

A

integrates visceral sensory inputs and autonomic outputs, projecting to higher brain centres involved in homeostasis

146
Q

nuclei

A

organised group of neurons in CNS

147
Q

hypothalamus

A

integrates autonomic responses, endocrine function and behaviour to maintain homeostasis

148
Q

which organ is referred to as master controller of homeostasis?

A

hypothalamus

149
Q

5 basic physiological needs regulated by hypothalamus

A
  • blood pressure +electrolyte balance (thirst)
  • body temperature
  • energy metabolism (food intake)
  • reproduction (hormones)
  • emergency responses to stress
150
Q

how does the hypothalamus process information?

A
  • compares sensory information to biological set points
  • if deviation detected, it coordinates autonomic, endocrine and behavioural responses to restore homeostasis
151
Q

pituitary gland

A

controls all glands in the body that regulate hormone release

152
Q

cerebral cortex is important for…

A

functions related to emotions, feelings and motivation

153
Q

what other brain regions does the hypothalamus interact with?

A
  • pituitary gland
  • cerebral cortex
  • amygdala
154
Q

how would the hypothalamus regulate for body temperature too low?

A
  • shivering = generates heat from skeletal muscles (automatic response)
  • thyroxin released from pituitary = vessel constriction on skin
  • cerebral cortex makes you feel uncomfortable/unmotivated = put sweater on
155
Q

amygdala

A

brain region that relates visceral responses to conscious feelings and connect emotions to memories

156
Q

which brain region is involved in learning? and how?

A

amygdala: remembers the emotions associated with the learning process/content

157
Q

uncus

A

small bump in temporal lobe that contains the amygdala

PHGY 209 (8 decks)

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