Physiology 1

Question 1

how do skeletal and cardiac muscle differ in terms of initiation of contraction?

Answer 1

skeletal = neurogenic initiation of contraction - so have neuromuscular junctions
cardiac = myogenic initiation of contraction - have gap junction instead of neuromuscular

Question 2

how do skeletal and cardiac muscles differ in terms of excitation contraction coupling?

Answer 2

skeletal = calcium is all from sarcoplasmic reticulum
cardiac = calcium from ECF and sarcoplasmic reticulum (Ca induced Ca release)

Question 3

how are skeletal and cardiac contraction graded?

Answer 3

skeletal = by motor unit recruitment and summation of contractions
cardiac = depends on preload

Question 4

how are skeletal muscle fibres arranged?

Answer 4

motor units

alpha motor neurons come from spinal cord to supply more than 1 muscle fibre

Question 5

how is cardiac muscle arranged?

Answer 5

individual muscle fibres are connected via desmosomes and intercalated discs

Question 6

what does the number of nerve fibres supplied by one alpha motor neuron depend on?

Answer 6

functionality of the muscle
fine movement muscles have fewer fibres per motor unit as precision is more important than strength (e.g facial expression, eye, fingers)
where power is more important (thighs) 1 nerve can supply thousands

Question 7

how are nerves and skeletal muscle fibres connected?

Answer 7

no continuation of cytoplasm

acetylcholine acts as a neurotransmitter at neuromuscular junctions

Question 8

what does skeletal muscle consist of?

Answer 8

parallel muscle fibres bundled by connective tissue

Question 9

how is skeletal muscle attached to skeleton?

Answer 9

tendons

Question 10

what are the levels of organisation in skeletal muscle?

Answer 10

muscle as whole made up of muscle fibres (cells)
each muscle fibre made up of myofibrils
myofibrils are arranged into sarcomeres
sarcomers consist of contractile proteins actin (thin) and myosin (thick)

Question 11

what does skeletal muscle consist of?

Answer 11

parallel muscle fibres bundled by connective tissue which run the entire length of the muscle

Question 12

how is muscle tension produced?

Answer 12

sliding of actin filaments on myosin filaments to shorten the sarcomere which hence shortens the muscle

Question 13

ATP is only required for contraction?

Answer 13

false

needed for both as ATP also breaks down the cross bridge as well as switching on its formation

Question 14

what is needed for cross bridges to form?

Answer 14

calcium and ATP

Question 15

when is calcium released from lateral sacs of sarcoplasmic reticulum?

Answer 15

when the surface action potential spreads down T tubules

Question 16

where can sarcomers be found in skeletal muscle?

Answer 16

between two Z lines

where ends of thin filaments line up vertically - connects the thin filaments of two adjoining sarcomeres

Question 17

what are the 4 zones of the sarcomere?

Answer 17

A band
H zone
M line
I band

Question 18

what is the A band?

Answer 18

thick filaments in the middle as well as portion of thin filaments which overlap

Question 19

why is ATP needed for relaxation?

Answer 19

it pumps calcium back into sarcoplasmic reticulum and binds to myosin head

Question 20

what is the M line?

Answer 20

vertical line down middle of A band, within H zone

Question 21

what is the I band?

Answer 21

remaining portion of thin filaments that don’t overlap with A band (areas between A bands)

Question 22

ATP is only required for contraction?

Answer 22

false

needed for both as ATP also breaks down the cross bridge after aiding its formation

Question 23

what is excitation contraction coupling?

Answer 23

where surface action potential results in activation of contractile structures of muscle fibre

Question 24

what are the 2 functions of calcium?

Answer 24

switch on cross bridge formation

link between excitation and contraction

Question 25

name 5 physiological functions of skeletal muscle

Answer 25

maintain posture
movement
respiratory movements
heat production (metabolism, shivering)
contributes to whole body metabolism

Question 26

where is smooth muscle found?

Answer 26

internal viscera

vasculature

Question 27

which muscle types are striated?

Answer 27

cardiac

skeletal

Question 28

which muscles are involuntary?

Answer 28

cardiac muscle

smooth muscle

Question 29

what causes striation in muscles?

Answer 29

alternating dark and light bands of myosin and actin

Question 30

which nervous system innervated each muscle type?

Answer 30

skeletal = somatic

cardiac and smooth = autonomic

Question 31

how does calcium aid contraction?

Answer 31

myosin binding site on actin is covered by tropomyosin
calcium binds to troponin which causes a conformational change and tropomyosin moves away exposing myosin binding site
cross bridge forms

Question 32

summarise how action potential caused skeletal muscle contractgion

Answer 32

acetylcholine is released from motor neuron axon and binds to receptors
action potential created from acetylcholine binding spreads across membrane and down T tubules causing calcium to be released from lateral sacs of sarcoplasmic reticulum
calcium binds to troponin on actin exposing the myosin binding site
cross bridge forms, pulling actin filaments over myosin causing contraction
once action potential has finished, calcium taken back up into sarcoplasmic reticulum (aided by ATP)
troponin slips back over myosin bindng site and ATP binds to myosin head causing destruction of cross bridge resulting in relaxation