Physiology

Question 1

What do motor units contain?

Answer 1

a single aplha neuron and all of the muscle fibres it innervates

Question 2

What initiates skeletal muscle contraction?

Answer 2

neurogenic

Question 3

What links excitation and contraction in skeletal muscle?

Answer 3

Ca from sarcoplasmic reticulum

Question 4

Is a neuromuscular junction present in skeletal muscle or cardiac muscle?

Answer 4

Skeletal

Question 5

What initiates cardiac muscle contraction?

Answer 5

myogenic - pacemaker potential

Question 6

Are gap junctions present in cardiac or skeletal muscle?

Answer 6

cardiac

Question 7

What links excitation in cardiac muscle?

Answer 7

Ca from the ECF and sarcoplasmic reticulum

Question 8

What is the transmitter at neuromuscular junctions?

Answer 8

acetylcholine

Question 9

what are myofibrils?

Answer 9

alternating sections of myosin and actin, arranged into sacromeres

Question 10

What is the functional unit of muscle?

Answer 10

sarcomeres

Question 11

What are the zones of sacromeres?

Answer 11

A band, H zone, M line, I band

Question 12

Where is a sacromere found/where does it span?

Answer 12

between two z lines

Question 13

What is the A band?

Answer 13

thick filaments with thin portions that overlap at the end

Question 14

What is the H zone?

Answer 14

light area in the middle of the A band

Question 15

What is the M line?

Answer 15

extends vertically down the H zone and the A band

Question 16

What is the I band?

Answer 16

remaining portion of filament that does not project into the A band

Question 17

What happens when a surface action potential is reached?

Answer 17

Ca is released from the lateral sacs of the SR, when the action potential spreads down the transverse T tubules
this causes cross bridge formation - actin and myosin

Question 18

What does skeletal muscle contraction depend on?

Answer 18

number of muscle fibres contracting

tension developed by each muscle fibre

Question 19

What is twitch summation?

Answer 19

muscle stimulated once = twitch

stimulated again before it can relax = greater tension twitch

Question 20

What is a muscles optimal length?

Answer 20

point where maximal tension is achieved - its resting length

i.e. point of optimal overlap of thick filament and thin filament cross bridge

Question 21

Describe isoTonic contraction?

Answer 21

FIXED POSTION

Tension constant, length changes

Question 22

Describe isometric contraction?

Answer 22

MOVEMENT

Tension changes, length constant

Question 23

Describe slow oxidative type 1 muscle fibres?

Answer 23

RED

used for prolonged, low work aerobic activities - walking

Question 24

Describe fast oxidative type 2a muscle fibres?

Answer 24

WHITE

use aerobic and anaerobic metabolism and are useful in prolonged moderate work - jogging

Question 25

Describe fast oxidative type 2b muscle fibres?

Answer 25

WHITE | use anaerobic metabolism and are useful in short term, high intensity activities

Question 26

What is the stretch reflex?

Answer 26

A negative feedback mechanism that resists passive change in muscle length to maintain the optimal length of muscle

Question 27

What is the receptor for the stretch reflex?

Answer 27

muscle spindle

Question 28

What is the effector for the stretch reflex?

Answer 28

increased firing in afferent neurones

Question 29

What are extrafusal fibres?

Answer 29

ordinary muscle fibres

Question 30

What are intrafusal fibrers?

Answer 30

muscle spindles - specialised muscle fibres

Question 31

What are muscle spindles supplied by?

Answer 31

gamma motor neurones

Question 32

What is the action of muscle spindles when muscle is stretched?

Answer 32

increased discharge from sensory endings

Question 33

What is the role of gamma motor neurones?

Answer 33

ajust the level of tension in muscle spindles to maintain their sensitivity when the muscles shorten during contraction

Question 34

What does electromyography measure?

Answer 34

detects the presence of muscular activity, frequencey and amplitude of muscle fibres