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Exercise Physiology > Muscle Physiology: Lecture 1 > Flashcards

Muscle Physiology: Lecture 1 Flashcards

1
Q

each muscle consists of ______ to ______ of individual contractile fibers

A

hundreds to thousands

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2
Q

connective tissue is made up of mostly…

A

mostly collagen, some elastin

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3
Q

epimysium

A

tough coat of tightly woven bundles of collagen which surround entire muscle, separating it from other muscles and structures

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4
Q

myotendinous junction

A

ends of the muscle where epimysium connects with the sarcolemma

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5
Q

why is there extensive folding of both the epimysium and sarcolemma?

A

more surface area?

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6
Q

perimysium

A

tough and thick

  • divides muscle fibers into fascicles, or bundles
  • provides pathway for arteries, veins and nerves
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7
Q

endomysium

A
  • surrounds each muscle fiber

- connects both the perimysium and the basement membrane

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8
Q

sarcolemma

A

consists of a

  • basement membrane
  • plasmolemma or cell membrane
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9
Q

basement membrane

A

several compounds, mostly proteins, glycoproteins, and collagen

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10
Q

conduit arteries and veins

A

parallel along surface of muscle

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11
Q

perforating arteries and veins dive into the belly of muscle in ______

A

parallel (in the belly)

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12
Q

arterioles lead to a ______ which surrounds each fiber

A

capillary network

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13
Q

a capillary network surrounds ______

A

each fiber

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14
Q

nerves usually run in _______ with the arteries and veins

A

parallel

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15
Q

what makes up 60% of the nervous innervation of skeletal muscle?

A

motor nerves

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16
Q

what represents the final nerve in the path from the motor centers In the cerebrum to the target muscle?

A

motor nerves

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17
Q

what produces muscle contraction when stimulated

A

motor nerves

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18
Q

motor nerve impulses travel in an ______ direction

A

efferent direction

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19
Q

efferent means

A

away from the spinal cord/central nervous system

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20
Q

impulses travel very fast along an axon because of ____

A

the myelin sheath

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21
Q

the region of muscle plasmalemma under the terminal axon

A

motor end plate

22
Q

what kind of nerves represent 40% of the nerves in skeletal muscles

A

sensory nerves

23
Q

sensory nerve impulses travel in an ____ direction

A

afferent direction

24
Q

afferent means

A

toward the spinal cord/central nervous system

25
Q

what is the purpose of sensory nerves?

A

they relay a variety of touch, pain, and muscle tension and contraction information

26
Q

skeletal muscles appear _____

A

striated

27
Q

____ is the cell membrane surrounding each cell

A

sarcolemma

28
Q

______ is a membranous network that surrounds each myofibril.

A

sarcoplasmic reticulum

29
Q

what is one of the primary roles of the of the sarcoplasmic reticulum?

A

the release of Ca++ which initiates the contraction process

30
Q

_____ are membranous channels that extend inward from the sarcolemma and pass completely through the fiber

A

transverse tubules

31
Q

the transvers tubules pass between enlarged portions of the SR called ______.

A

cisternae

32
Q

each ______ is long and rod-like in shape, it consists of a 3 dimensional arrangement of the contractile elements.

A

myofibril

33
Q

the basic unit of the contractile element is the ______. each is separated from the next by connective tissue called a Z line.

A

sarcomere

34
Q

myosin filaments

A

thicker, make up the dark A band

35
Q

actin filaments

A

thin, and extend in both directions from the Z line

-constitute the lighter region of the sarcomere called the I band

36
Q

H zone

A

at the center of the sarcomere

-represents the area of only myosin, between the actin filaments extending from the Z line at each end of the sarcomere

37
Q

actin

A

double helix of spherical molecules which contain sites for binding to myosin

38
Q

tropomyosin

A

helical molecule that wraps around the actin strand to cover up the myosin binding sites

39
Q

troponin

A

sits on the tropomyosin strands

-has a binding site for Calcium

40
Q

titin

A

the largest proteins in our bodies (keeps myosin in place)

  • found in cardiac and skeletal muscle fibers
  • acts like a giant spring
  • thethers the myosin filament within the sarcomere
  • source of much of the passive force in skeletal muscle
  • the major mechanism for the frank-starling mechanism in the heart
41
Q

motor-end plate

A

the site where the alpha motor neuron ends and transmits depolarization signal to the muscle

42
Q

true or false: the alpha motor neuron physically touches the sarcolemma of the muscle cell

A

false: it does not touch the sarcolemma of the muscle cell

43
Q

neuromuscular junction or synaptic cleft

A

where the sarcolemma inviginates around the alpha motor neuron synapse

44
Q

steps in excitation contraction coupling ECC

A
  1. alpha motorneuron depolarization wave (action potential)leads to the release of acetylcholine ACh from nerve ending (nerve bouton)
  2. ACh binds to ACh binding site, causing Na+ entry into cell, leading to depolarization of muscle cell membrane (sarcolemma): called the end-plate potential
  3. depolarization wave on sarcolemma is transmitted down the t-tubules
  4. this leads to the release of calcium from the sarcoplasmic reticulum
  5. Calcium then binds to troponin initiating contraction process
  6. to restore the cell to its pre contraction state, calcium is pumped back into the SR by the SR Calcium ATP-ase
  7. ACh is broken down by enzyme acetylcholinesterase
45
Q

consequence of excitation contraction coupling

A

there has to be continual motorneuron activity to cause continued muscle contraction

46
Q

muscle contraction – the sliding filament theory

A
  1. rest
  2. excitation coupling
  3. active contraction
  4. recharging system
  5. subsequent response dependent on presence of Calcium
47
Q

step 1. rest of sliding filament theory

A

a. myosin heads extended, but not contacting actin
b. Calcium stored in sarcoplasmic reticulum
c. myosin head is energized by breakdown of ATP

48
Q

Step 2. excitation coupling

of the sliding filament theory

A

a. nerve impulse from motor neuron leads to depolarize of sarcolemma, SR.
b. Calcium released from SR into cytosol
c. Calcium binds to troponin, causes tropomyosin to shift, exposing myosin binding sites on actin
d. myosin binds to active site on actin

49
Q

Step 3: active contraction

of the sliding filament theory

A

a. myosin heads flex, causing myosin chain to move along the actin filament, resulting in shortening of the sarcomere
b. force is developed
c. ADP and Pi are released from the myosin head

50
Q

Step 4: recharging system

of the sliding filament theory

A

a. ATP binds to myosin, causing release of actin myosin bond

b. ATP is then broken down, resulting in charging of the myosin head, and production ADP and Pi

51
Q

Step 5: subsequent response dependent on presence of calcium

of the sliding filament theory

A

a. if calcium is still present, means nerve stimulation still occurring, muscle contraction, repeat steps 2-4.
b. if nerve depolarization ceases, Calcium can be resequestered in SR by calcium ATPase. this leads to muscle resting in step #1.

Exercise Physiology (10 decks)

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