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Flashcards in Physiology Deck (165)
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1

What is a motor unit?

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

2

if the alpha motor neurone supplies an area with fine motor control, will they have many or few muscle fibres?

few

3

if the alpha motor neurone supplies an area with muscles needed for force, will they have many or few muscle fibres?

many

4

what is the functional unit of a muscle?

sarcomere

5

compare cardiac muscle and skeletal muscle in terms of gap junctions?

cardiac muscles have gap junction (so AP can spread)
skeletal muscles don't have gap junctions

6

compare cardiac muscle and skeletal muscle in terms of neuromuscular junctions?

cardiac muscle does not contain neuromuscular junctions
skeletal muscle contains neuromuscular junctions

7

when is skeletal muscle at optimum length?

resting

8

when is cardiac muscle at optimum length?

when stretched

9

compare cardiac muscle and skeletal muscle in terms of initiation and propagation of contraction?

cardiac muscle- myogenic (pacemaker potential)

skeletal muscle- neurogenic

10

compare cardiac muscle and skeletal muscle in terms of Ca++ input?

cardiac muscle- Ca++ from ECF and sarcoplasmic reticulum

skeletal muscle- Ca++ entirely from sarcoplasmic reticulum

11

in skeletal muscle fibres, when is Ca++ released from lateral sacs of the sarcoplasmic reticulum?

when surface action potential spreads down the T tubules

12

what are T tubules?

extensions of the surface membrane that dip into the muscle fibre

13

what is the transmitter at the neuromuscular junction?

acetylcholine

14

what is a myofibril?

made of lots of sarcomeres aligned head to tail
(intracellular)

15

how far do skeletal muscle fibres (cells) usualy extend?

the entire length of the muscle

16

how are skeletal muscles attached to the skeleton?

by tendons

17

how are myofibrils positioned within a cell?

parallel to each other

18

what lines form the borders of the sarcomere?

Z lines

19

what is an A band?

the area of myosin
(with or without overlapping actin)

20

what is an I band?

the area of actin without any overlapping myosin

21

what is a H zone?

the area of myosin without any overlapping actin

22

what is the M line?

extends vertially down the middle of the A band within the centre of the H zone

23

what is required for both contraction and relaxation?

ATP

24

what is required to switch on cross bridge formation between actin and myosin?

Ca++

25

How does Ca++ switch on cross bridge formation between actin and myosin?

by binding to troponin, this results in a conformational change of troponin-tropomyocin complex which uncovers the cross bridge binding sites on actin

26

Give 2 reasons why ATP is needed during muscle relaxation?

1. to release cross bridges
2. to pump Ca2++ back into sarcoplasmic reticulum

27

Give 1 reason why ATP is needed during muscle contraction?

1. to power cross bridges

28

What does the gradation of skeletal muscle tension depend on?

the tension developed by each contracting muscle fibre
and
the number of muscle fibres contracting within the muscle

29

What is motor unit recruitement?

stimulation of more motor units in order to get a stronger contraction

30

What 3 factors are determine the tension developed by a single contracting muscle fibre?

-the frequency of stimulation/summation of contractions
-length of the muscle fibre at onset o contractions
-thickness of the muscle fibre