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2024 Vet physiology > Exam 1: Lecture 6: Skeletal Muscle Physiology 1 > Flashcards

Exam 1: Lecture 6: Skeletal Muscle Physiology 1 Flashcards

1
Q

what is known as neurons that innervates muscle fibers

A

motorneuron

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2
Q

what is known as a single motorneuron and muscle fiber it innervates

A

motor unit

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3
Q

Are small or large motor units used for fine activities

A

small motor units

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4
Q

Are small or large motor units used for gross control

A

large motor units

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5
Q

At the neuromusclular junction, an AP is propigated to presynpatic terminal causing voltage gated Ca2+ channels opening, what follows?

A
  • Ca2+ permability increases
  • Ca2+ flows into the cell
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6
Q

After Ca2+ voltage gated channels increase, Ca2+ flows into the cell and Ca2+ permeability increases = causing a released in _______, which is stored in synaptic vessicles

A

Ach

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7
Q

Ach diffusing to post synaptic membrane is called

A

motor end plate

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8
Q

After Ach is released and flows down the motor end plate it binds to ______ = channels opens, Na+ moves in and K+ moves out

A

ACh binds to nicotine receptors

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9
Q

What is the end plate potential after Na+ moves into the cell and K+ moves out?

A

Motor end plate depolarizes from -90 mV to -50 mV

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10
Q

End plate potential stops when ACh is degraded by ____________-

A

acetylcholinesterase
AChE

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11
Q

This toxin blocks the release of ACh from presynaptic terminals
- does not tell the muscle to contract
- Death from respiratory failure, paralysis of limbs

A

Botulinum toxin

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12
Q

This prevents degradation of ACh in the synaptic cleft
- treat myasthenia gravis

A

AChE inhibitors

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13
Q

what do muscle fibers contain

A

myofibrils

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14
Q

What is the name for a group of muscle fibers

A

Fasciculus

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15
Q

Muscle cells are innervated by _______

A

motorneurons

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16
Q

Events between AP in muscle fiber and a contraction are called:

A

Excitation-contraction coupling

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17
Q

A muscle cell is composed of ________, ________. and ________ and surrounded by Sarcoplasmic reticulum

A

Actin
Mysoin
Titin

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18
Q

What is the basic definition of a sarcomere

A

Repeating thick and thin filaments along the myofibril
- contractile unit

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19
Q

Where do sarcomeres occur between

A

Adjacent Z lines (disks)

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20
Q

Light band is also known as:

A

I band

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21
Q

What band is composed of Thin filaments (actin) and Z disk

A

Light band ( I band)

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22
Q

Dark band is also known as:

A

A band

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23
Q

What band is composed of thick filaments (myosin)

A

Dark band (A band)

24
Q

define overlap and what band it is associated with

A

Associated with dark (A) band

  • overlap: overlap of actin thin filaments with myosin thick filaments
  • where force on contraction starts
25
Q

What is another name for the Bare zone

A

H zone

26
Q

Does the bare zone contain thin filaments and where it located

A

center of sarcomere
- NO thin filaments

27
Q

What is known as the dark staining protein and links thick filaments

A

M line

28
Q

Describe the formation of thick filaments - myosin

A
  • Heavy chains: forms the tail portion (2)
  • Light chains: 2 pairs forming two globular heads. ATP binding site and Actin binding site
29
Q

Describe the formation of thin filaments - actin

A

Two strands twisted

30
Q

________ runs along the grooves of twisted actin

A

Tropomyosin

31
Q

What typically blocks the myosin binding site when the muscle is at rest

A

tropomyosin

32
Q

Troponin T, I, or C?

Attaching entire complex (I,T, and C) to tropomyosin

A

Troponin T

33
Q

Troponin T, I, or C?

Ca2+ binds protein

A

Troponin C

34
Q

Troponin T, I, or C?

most important

A

Troponin C

35
Q

Troponin T, I, or C?

inhibit the interaction of actin + myosin by covering the binding site

A

Troponin I

36
Q

What anchors the myofibril scaffold to the cell membrane

A

Dystrophin

37
Q

What centers thick filaments in the sarcomere to have proper overlap

A

Titin

38
Q

What sets the length of thin filaments for interaction / contraction purpose and good for strong muscle contraction

A

Nebulin

39
Q

Muscle cells are surrounded by:

A

Sarcolemma

40
Q

Sarcolemma has invaginations called ______________ extending into the muscle and carries depolarization from motor endplate to the cell interior and contact the SR

A

Transverse T tubules

41
Q

Myofibrils are surrounded by what that regulate Ca2+ in the cytosol

A

Sarcoplasmic reticulum - SR

42
Q

How does the SR store Ca2+

A

SERCA pump - Ca2+ ATPase

43
Q

What is Ca2+ bound to in the SR

A

Calsequestrin

44
Q

What releases Ca2+ from the SR

A

Ryanodine receptor

45
Q

When an AP travels down T tubules what undergoes conformation change as the AP arrives

A

Dihydropyridine receptors in T tubules

46
Q

once the Dihydropyridine receptors in the T tubule under a conformation change, this receptor unders a conformation change also, which is a Ca channel that opens and releases Ca from the SR = Ca2+ cytosol levels / concentration increases

A

ryanodine receptor

47
Q

How many Ca bind one troponin C

A

4

48
Q

what sites on Ca2+ are responsible for:

  • bind both Ca + Mg with high affinity sites occupied by either ion under low Ca
A

Sites 3 and 4

49
Q

What sites on Ca2+ are responsible for:

  • Bind calcium with low affinity = need high concentration to keep sites occupied
  • Ca regulation sites for a contraction = they only bind Ca when Ca concentration levels are high
A

Sites 1 and 2

50
Q

What is the result of a conformation change in troponin complex in Excitation-contraction coupling

A

Moves tropomyosin away from myosin binding sites on actin = cross bridging can now occur

51
Q

What is it called when myosin heads bind actin

A

cross bridging

52
Q

In Cross bridge cycling, ATP binds the myosin head, decreasing affinity for actin, what is released

A

Myosin releases

  • 2nd step
53
Q

In Cross bridge cycling, Mysoin head attached to actin in a ________ position

A

rigor

  • 1st step
54
Q

In cross-bridge cycling, ATP hydrolyzes, and myosin moves towards the plus end of actin - away from the M line, meaning what?

A

Actin moves towards the center of the sarcomere

  • 3rd step
55
Q

In Cross bridge cycling, Myosin binds new site on actin, which is called

A

Power stroke

  • 4th step
56
Q

In Cross bridge cycling when power stroke occurs, when does contractions stop

A
  • When AP passes
  • Ryanodine receptors close
  • Ca reaccumulation by the SR via the SR Ca pump
57
Q

What conditions must be met for Cross bridge cycling continue

A
  • Ca2+ concentration in increased (bound to troponin C)
  • Cystostolic ATP must be available

2024 Vet physiology (28 decks)

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