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Flashcards in Physiology Deck (47)
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1

What is the largest tissue type in the body?

Muscle

2

All muscle in the body is striated. True/False?

False
Smooth muscle is not striated

3

Which division of the nervous system - autonomic or somatic - innervates skeletal muscle?

Somatic

4

Skeletal muscle fibres are organised into motor units. What are motor units?

Motor neuron + all the muscle fibres innervated by that single motor neuron

5

What determines the number of muscle fibres per motor unit?

The function of the muscle (whether it is concerned with powerful or precise movement)

6

Give examples of muscles that have few muscle fibres per motor unit

External eye muscles
Muscles of facial expression
Intrinsic hand muscles

7

What is contained within a muscle fibre?

Myofibrils and sarcomeres

8

Skeletal muscle contraction is brought about by myogenic initiation. True/False?

False
Neurogenic (nerve stimulated first)

9

Are there gap junctions between muscle fibres?

No

10

Which substance is released in response to action potential generation + presence in the T-tubule of the muscle fibre?

Calcium

11

What does calcium release by the sarcoplasmic reticulum cause?

Calcium binds to troponin, causing conformational change in tropomyosin complex to expose myosin-binding-site on actin to allow cross-bridge formation between actin and myosin

12

List the 4 zones of a sarcomere

A-band
H-zone
I-band
M-line

13

What does the A-band consist of?

Myosin + portion of actin that overlaps with myosin

14

Where is the H-zone?

Lighter area within A-band where actin doesn't reach

15

Where is the M-line?

Extends vertically down the middle of the A-band within the centre of the H-zone

16

What does the I-band consist of?

Remaining portion of actin that is not part of the A-band

17

What 2 primary factors determine gradation of skeletal muscle tension?

Number of muscle fibres contracting within the muscle
Tension developed by each muscle fibre

18

What is meant by "motor unit recruitment"?

Stimulating numerous motor units to contract elicits stronger contraction

19

Tetanic contractions of skeletal muscle are not possible. True/False?

False

20

How is tetanic contraction of skeletal muscle brought about?

Generation of numerous action potentials one after the other amplify the contraction/skeletal muscle twitch

21

When can maximum tetanic contraction of skeletal muscle be achieved?

At rest (optimal length of muscle at this point)

22

Name the 2 main types of skeletal muscle contraction

Isotonic
Isometric

23

What is isotonic skeletal muscle contraction used for?

Body movements
Moving objects

24

Muscle length changes in isotonic skeletal muscle contraction. True/False?

True
Muscle tension remains constant

25

What is isometric skeletal muscle contraction used for?

Maintaining fixed positions

26

Muscle length changes in isometric skeletal muscle contraction. True/False?

False
Muscle length is constant to allow tension to develop

27

Velocity of muscle length shortening increases/decreases with increasing load

Decreases

28

What is the stretch reflex?

Negative feedback mechanism that resists passive change to muscle length by contracting the muscle

29

Once a muscle is stretched, how does the stretch reflex elicit contraction?

Afferent fibres fire and synapse with alpha motor neurons which, when stimulated, contract the stretched muscle

30

What are the special sensory receptors for the stretch reflex, that, when stretched, elicit the reflex?

Muscle spindles AKA intrafusal fibres