Physiology

Question 1

Functions of Skeletal muscle

Answer 1

Maintainposture, purposeful movement, resp movements, heat production, contributes to metabolism

Question 2

Skeletal muscle features

Answer 2

Striated and voluntary (innervated by somatic nervous system), no gap junctions, neurogenic initiation (acteylcholine neurotransmitter @ neuromuscular junction), calcium entirely from SR

Question 3

Cardiac muscle features

Answer 3

striated and involuntary (autonomic)

Question 4

Smooth muscle

Answer 4

unstriated and involuntary (autonomic)

Question 5

Motor unit

Answer 5

a single alpha motor neuron and all the skeletal muscle fibres it innervates

Question 6

Precision > ….

Answer 6

Power

Question 7

Fine movements have …

Answer 7

fewer fibres per motor unit (10 or so)

Question 8

Powefful movements have …

Answer 8

more fibres per motor unit (100s -1000s)

Question 9

Breakdown of muscle

Answer 9

Muscle > Muscle fibre > Myofibril > Sarcomere

Question 10

Sarcomere contains …

Answer 10

Myocin and actin (actin slides over myocin)

Question 11

Actin is …

Answer 11

thin and light

Question 12

Myocin is …

Answer 12

thick and dark

Question 13

skeletal muscle consists of …

Answer 13

parallel muscle bundled by connective tissue (fibres suually exteend entire length of muscle)

Question 14

Sarcomeres are found….

Answer 14

between two Z lines (

Question 15

Sarcomeres contain four zones

Answer 15

A band, H zone, M line and I band

Question 16

How calcium is released in skeletal muscles…

Answer 16

In fibres Ca2+ is released from the lateral sacs of the SR when the surface action potential spreads down the transverse tubules (T-tubules)

Question 17

ATP is needed:

Answer 17

• during muscle contraction (to power cross bridges)

- During relaxation to release cross bridges and to pump Ca2+ back into SR

Question 18

Skeletal muscle tension is dpendent on

Answer 18

number of muscle fibres contracting and the tension developed by each contracting muscle fibre (depends on frequency of stimulation and summation of contractions)

Question 19

In skeletal muscle the duration of action potential is …

Answer 19

much shorter than the resulting twitch

Question 20

Stronger contractions can be achieved by …

Answer 20

summating twitches through repetitive fast stimulation of skeletal muscle

Question 21

Tetanus

Answer 21

muscle fibre stimulated so rapidly that it has no oppurutnity to relax (e.g. lock jaw)

Question 22

Why can’t cardiac muscle tetanus

Answer 22

it has too long a refractory period

Question 23

Increasing frequency of stimulation of skeletal muscle causes

Answer 23

stonger contraction

Question 24

Maximal contraction can be achieved when

Answer 24

the muscle is at its optimal length before the onset of contraction

Question 25

Isotonic contraction

Answer 25

used for body movements and moving objects. Tension remains constant as the muscle changes

Question 26

Isometric contraction

Answer 26

used for supporting objects in fixed positions and maintain body posture. Muscle tension develops at constant muscle length.

Question 27

Slow oxidative

Answer 27

type 1 = slow contraction, high reisstance to fatigue, low work aerobic e.g. walking

Question 28

Fast oxidative

Answer 28

type IIa = fast contraction, average resistance to fatigue, aerobic and anaerobic e.g. jogging

Question 29

Fast-glycolytic

Answer 29

type IIx = fast contraction, low resistance, to fatigue, anaerobic, short term high intensity e.g. jumping

Question 30

reflex action

Answer 30

stereotyped response to a specific stimulus

Question 31

stretch reflex

Answer 31

a negative feedback that resists passive change in muscle length to maintain optimal resting length of muscle.

Question 32

Muscle spindle

Answer 32

sensory receptor in muscle stretch (afferent neurons increase firing to motor units)

Question 33

example of stretch reflex

Answer 33

tendon hammer on patellar tendon (checks femoral nerve L3, L4)

Question 34

causes of imapired skeletal muscle function

Answer 34

intrinsic disease of muscle diseae of NMJ disease of lower motor neurons which supply muscle disruption of input to motor nerves (e.g. MND)

Question 35

Genetic causes of intrinsic muscle disease

Answer 35

``` Congenital myopathies (reduced contractility of musles) Chronic degeneration (e.g. muscular dystrophy) Abnormalities in membrane ion channels (e.g. myotonia) ```

Question 36

Acquired causes of intrinsic muscle disease

Answer 36

inflammatory myopathies (polymositis) Non-inflammatory (fibromyalgia) Endocrine (cushing syndrome, thyroid disease) Toxic (alcohol, statins)

Question 37

Symptoms of muscle disease

Answer 37

muscle weakness, delayed relaxation post voluntary contraction (myotonia), muscle pain (myalgia), msucle stiffness

Question 38

Invx in neuromsucular disease

Answer 38

Electromyography (EMG) [electrodes detect muscular activity] > Nerve conduction studies (done with EMG, checks function of peripheral nerves) > Muscle enzymes (CK) > Inflammatory markers (CRP, Plasma Viscocity) > Muscle Biopsy