Part 1: Muscle Physiology Flashcards Preview

SF1.12 Muscle Physiology (ZACHOW) > Part 1: Muscle Physiology > Flashcards

Flashcards in Part 1: Muscle Physiology Deck (49)
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1

To perform work and generate power, all muscles require:

ATP and calcium

2

Load of skeletal muscle, load of smooth muscle, load of cardiac muscle:

  • Skeletal: gravity
  • Smooth: blood pressure, food/digestion
  • Cardiac: blood pressure

3

Sources of calcium and ATP for skeletal muscle:

 

  • Ca2+: intracellular
  • ATP: stored, phosphagen, glycolytic, oxidative phosphoryation, fatty acids

4

Sources of calcium and ATP for smooth muscle:

  • Ca2+: extra- and intracellular
  • ATP: oxidative phosphorylation
     

5

Sources of calcium and ATP for cardiac muscle:

  • Ca2+: extra- and intracellular
  • ATP: oxidative phosphorylation, fatty acids

6

Functions of skeletal muscle:

  • Ambulation, posture
  • Displacing mass
  • Glucoregulation

7

Function of cardiac muscle (myocardium):

Moving blood volume
 

8

Function of smooth muscle:

  • Changing lumenal diameter
  • Digestion
  • Blood pressure

9

Hierarchy of muscle structure:

  1. Whole muscle
  2. Fascicles
  3. Muscle fibers/cells (covered with satellite cells)
  4. Myofibrils
  5. Sarcomeres
  6. Myofilaments
  7. Actin
  8. Myosin

10

The three types of troponin and their roles:

  • Troponin I (anchor to actin)
  • Troponin C (calcium binding)
  • Troponin T (anchors to tropomyosin)

11

What protein is interwoven into the actin filament and binds myosin?

tropomyosin

12

Structure of muscle myofilaments:

13

Process of voluntary muscle contraction:

  1. Brain initiates movement.
  2. Brain signal travels down spinal cord descending tracts.
  3. Signal leaves spinal cord through ventral root.
  4. Signal travels on alpha and gamma motor neurons to muscle fibers.

14

A motor unit consists of:

Motor neuron + fiber(s) it innervates

15

What motor neurons are involved in voluntary skeletal muscle contraction?

alpha and gamma motor neurons

16

Steps in neuromuscular transmission to muscle contraction:

  1. Action potential reaches motor neuron terminus. Voltage-gated calcium channels open, calcium influx, acetylcholine synaptic vesicles released.
  2. Acetylcholine binds to cholinergic-nicotinic (CN) receptors on the post-synaptic membrane of the muscle cell. Small sodium influx generates end plate potential.
  3. Endplate potential opens voltage-gated sodium channels, sodium rushes in and causes action potential firing in the muscle cell.
  4. Action potential travels down T-tubules of muscle cells and activates dihydropyridine receptors (DHPRs).
  5. DHPRs activate ryanodine receptors (RYRs), which are calcium channels. Calcium influx into the sarcoplasm of the T-tubule from the sarcoplasmic reticulum.
  6. Elevated sarcoplasmic reticulum calcium levels. Calcium binds to troponin C, causing conformational change in troponin C. Tropomyosin on actin revealed.
  7. Myosin head binds to tropomyosin on the actin.
  8. Myosin head changes conformation, power stroke occurs, which releases ADP + Pi from the myosin head.
  9. ATP binds to myosin head, myosin dissociates from tropomyosin/actin.
  10. ATP is hydrolyzed to ADP + Pi.
  11. Myosin head binds to tropomyosin. Repeat power strokes continue so long as increased calcium levels in the sarcoplasmic reticulum keep tropomyosin exposed.

17

Alpha and gamma motor neurons use what neurotransmitter/receptor to generate an end plate potential in muscle cells?
 

  • Neurotransmitter: acetylcholine
  • Receptor: cholinergic-nicotinic (CN)

18

Cholinergic-nicotinic (CN) receptors are:

  • ligand-gated sodium channels activated by acetylcholine.
  • activation generates an end plate potential.

19

What occurs when acetylcholine from a motor neuron crosses the synaptic cleft and binds to cholinergic-nicotinic (CN) receptors on the membrane of a muscle cell?

  • Small sodium influx generates end plate potential.
    • Endplate potential opens voltage-gated sodium channels, sodium rushes in and causes action potential firing in the muscle cell. 

20

Once an action potential is generated in a muscle cell, where does it go and what does it activate?

  • Action potential travels down T-tubules of muscle cells and activates dihydropyridine receptors (DHPRs), which activate ryanodine receptors (RYRs), which are calcium channels. 

21

Dihydropyridine receptors (DHPRs):

  • receptors located in the T-tubules of muscle cells
  • activated by calcium
  • activate ryanodine receptors (RYRs)

22

Ryanodine receptors (RYRs): 

  • Calcium channels activated by dihydropyridine receptors (DHPRs).
  • Cause a calcium influx into the sarcoplasm of the T-tubule from the sarcoplasmic reticulum.

23

What occurs in muscle cells when there is a sudden elevation in sarcoplasmic calcium levels?

cross-bridge cycling

  1. Calcium binds to troponin C, causing conformational change in troponin C.
  2. Tropomyosin on actin revealed.
  3. Myosin head binds to tropomyosin on the actin. 

24

Steps in cross-bridge cycling:

  1. Increased sarcoplasmic calcium levels from RYRs activation.
  2. Calcium binds to troponin C, causing conformational change. 
  3. Tropomyosin on actin revealed. 
  4. Myosin head binds to tropomyosin on the actin.
  5. Myosin head changes conformation, power stroke occurs, which releases ADP + Pi from the myosin head.
  6. ATP binds to myosin head, myosin dissociates from tropomyosin/actin.
  7. ATP is hydrolyzed to ADP + Pi.
  8. Myosin head binds to tropomyosin. Repeat.
     

25

Myosin head power strokes continue in muscle cells so long as:

  • increased calcium levels in the sarcoplasm keep troponin C structurally altered to keep tropomyosin exposed.

26

What occurs in the muscle cell when myosin powerstrokes occur?

  • Muscle contracts (Z-discs move closer to one another)

27

ATP for cross-brdige cycling in skeletal muscle is produced from:

  • Sarcoplasmic stores
  • Phosphocreatine
  • Glycolysis
  • Oxidative phosphorylation

28

Fuel for muscle contraction lasting a few seconds:

ATP stored in sarcoplasm
 

29

Fuel for muscle contraction lasting a few seconds to a  minutes: 
 

  • ATP generated from phosphocreatinine/creatinine kinase

30

Fuel for muscle contraction lasting a few minutes: 

ATP generated from anaerobic glycolysis