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Flashcards in Physiology Deck (165):
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

31

what is the name of a maximal sustained contraction due to high frequency of stimulation?

tetanus

32

compare cardiac muscle fibre and skeletal muscle fibre in terms of refractory period and twitch summation

cardiac muscle fibre- long refractory so no summation ability

skeletal muscle fibre- short refractory period so summation can occur

33

What are the 2 types of skeletal muscle contraction?

isotonic contraction
isometric contraction

34

what is isotonic contraction of a skeletal muscle?

muscle tension remains constant as the muscle length changes

35

what is isometric contraction of a skeletal muscle?

muscle tension develops at constant muscle length

36

what happens to the velocity of muscle shortening as load increases?

velocity of muscle shortening decreases

37

what is reflex action?

a reflex action is a stereotyped response to a specific stimulus

38

what is the simplest monosynaptic spinal reflex?

stretch reflex

39

what are the 5 steps of a stretch reflex?

1. muscle is stretch passively
2. sensory receptors in muscle spindles are activated
3. afferent neurons increase firing
4. neurons synapse on spindle cord with the alpha motor neuron that supplies the stretched muscle
5. efferent neuron sends impulse to contract muscle

40

what is the purpose in a stretch reflex?

negative feedback to resist passive change in muscle length- maintains optimal resting length of muscle

41

what muscle is involved in the knee jerk reflex?

quadriceps femoris

42

what peripheral nerve is involved in the knee jerk reflex?

femoral nerve

43

what peripheral nerve is involved in the ankle jerk reflex?

tibial nerve

44

what peripheral nerve is involved in the biceps jerk reflex?

musculocutaneous nerve

45

what peripheral nerve is involved in the brachioradialis jerk reflex?

radial nerve

46

what peripheral nerve is involved in the triceps jerk reflex?

radial nerve

47

what does it mean if there is an over-jerked reflex?

inhibitory mechanisms from the brain (upper motor neuron) have become damaged

48

what are muscle spindles also known as?

intrafusal fibres
(because they run within the belly of muscles)

49

what are the sensory nerve endings of muscle spindles called?

annulospiral fibres

50

what happens to the discharge from the muscle spindles sensory endings as the muscle is stretched?

increased discharge

51

what type of motor neurons supply muscle spindles?

gamma motor neurons

52

in order to maintain their sensitivity, what do gamma-motor neurons do?

adjust their level of tension when the muscles shorten during contraction (active)

53

as you increase the capacity to synthesis ATP, what happens to the muscle?

becomes more resistant to fatigue

54

what can muscles with a high activity of myosinATPase do?

can contract faster

55

what are the 3 types of skeletal muscle fibre?

type 1: slow oxidative
type 2a: fast oxidative
type 2x: fast glycolytic

56

compare the 3 types of skeletal muscle fibre in terms of myosin-ATPase activity and therefore speed of contraction?

type 1: slow oxidative -low myosin-ATP activity so slow
type 2a: fast oxidative- high myosin-ATP activity so fast
type 2x: fast glycolytic- high myosin-ATP activity so fast

57

compare the 3 skeletal muscle fibre types in terms of their resistance to fatigue?

type 1: slow oxidative - high resistance
type 2a: fast oxidative - intermediate resitance
type 2x: fast glycolytic- low resistance

58

compare the 3 skeletal muscle fibre types in terms of oxidative phosphoylation capacity?

type 1: slow oxidative- high capacity
type 2a: fast oxidative- high capacity
type 2x: fast glycolytic- low capacity

59

compare the 3 skeletal muscle fibre types in terms of the volume of enzymes for anaerobic glycolysis?

type 1: slow oxidative- low
type 2a: fast oxidative- intermediate
type 2x: fast glycolytic- high

60

compare the 3 skeletal muscle fibre types in terms of mitochondria?

type 1: slow oxidative- many
type 2a: fast oxidative- many
type 2x: fast glycolytic- few

61

compare the 3 skeletal muscle fibre types in terms of surrounding capillaries?

type 1: slow oxidative- many
type 2b: fast oxidative- many
type 2x: fast glycolytic- few

62

compare the 3 skeletal muscle fibre types in terms of myoglobin content and therefore colour?

type 1: slow oxidative- high so red
type 2b: fast oxidative- high so red
type 2x: low so white

63

compare the 3 skeletal muscle fibre types in terms of glycogen content?

type 1: slow oxidative- low
type 2: fast oxidative- intermediate
type 3: fast glycolytic- high

64

what are slow oxidative type 1 skeletal fibres mainly used for?

prolonged, low work, aerobic activities

65

what are fast oxidative type 2a skeletal fibres mainly used for?

prolonged, moderate work, aerobic and anaerobic activities

66

what are fast glycolytic type 2x skeletal fibres mainly used for?

short-term, high intensity, anaerobic activities

67

what does a electromyography (EGM) help differentiate from?

primary muscle disease from muscle weakness caused by neurological disease

68

Where do the vesicles containing ACh in the pre-synaptic cell cluster at?

active zones

69

what is the name of the folds on the post-synaptic cell of a neuro-muscular junction?

junctional folds

70

what is the function of schwann cells in the neuromuscular junction?

they try to encapsulate the neuromuscular junction to insulate from other influences

71

how is choline transported into the presynaptic cell?

choline transporter
(using Na+)

72

in the choline transporter state the direction of Na+ and choline movement?

both move into the pre-synaptic cell

73

in the pre-synaptic cell, what provides acetyl CoA for making ACh?

mitochondria

74

what enzyme uses choline and acetyl CoA to make acetyl choline?

choline acetyltransferase
(CAT)

75

what causes depolarisation of the presynaptic cell?

the action potential

76

what does depolarisation of the presynaptic cell cause?

opening of voltage gated Ca++ channels causing an influx of calcium

77

what does an influx of calcium in the presynaptic cell cause?

causes fusion of vesicles at the active zones with the presynaptic membrane
EXOCYTOSIS

78

what makes up a nicotinic ACh receptor?

5 subunits with a central cation-conduction pore

79

when does the central pore of a nicotinic receptor open?

when 2 ACh molecules are binded to it

80

What happens when 2 ACh molecules bind to the nicotinic receptor on the muscle end plate?

central pore opens allowing influx of Na+ (faster) and efflux of K+ (slower)

81

when the central pore of a nicotinic receptor is open, why is the influx of Na+ faster than the eflux of K+?

because the driving force for Na+ is greater than for K+ at resting membrane potential

82

when the central pore of a nicotinic receptor is open, what happens to the polarisation of the cell? what is this known as?

depolarisation
end plate potential

83

end plate potential is a graded response, what does this mean?

many miniature end plate potentials summate to produce the end plate potential

84

if the end plate potential is large enough to trigger the all-or none response, what happens?

triggered opening of Na+ channels around the muscle end plate so further Na+ influx
(positive feedback)

85

why are the positive feedback Na+ channels around the opening of the muscle end plate important?

to amplify the AP to ensure propagation
(because as it spreads it will slowly decline due to the skeletal muscle fibre being a poor insulator)

86

What enzyme hydrolyses the ACh to choline and acetate?

acetylcholinesterase (AChE)

87

Where is acetylcholinesterase found?

on the end plate membrance

88

what happens to the choline once the ACh has been broken down?

gets taken up by choline transporter

89

what happens to the acetate once the ACh has been broken down?

diffuses from the synaptic cleft

90

what antibodies are formed in neuromyotonia? and what does this cause?

antibodies against the voltage-activated K+ channels

hyperexcitability of muscular end plate (repetitive firing)

91

what is the drug treatment for neuromyotonia? and why does this work?

anti-convulsants (eg carbamazepine, phenytoin)
block voltage-activated Na+ channels (to reduce excitability of muscular end plate)

92

What cancer is Lambert-Eaton Myasthenic Sndrom (LEMS) associated with?

small cell carcinoma of hte lung

93

what antibodies are formed in Lambert-Eaton Myasthenic Syndrome? and what does this cause?

antibodies against voltage-activated Ca++ channels

reduced Ca++ entry into presynaptic cells so reduced ACh release

94

what antibodies are formed in Myasthenia Gravis? and what does this cause?

antibodies against nicotinic ACh receptors in the endplate

so reduces the amplitude of the end plate potential

95

What does botulinum toxin do to neuromuscular junction?

irreversibly inhibits ACh release

96

what are the 3 types of joint?

synovial
fibrous
cartilaginous

97

in a fibrous joint, what are the bones united by?

fibrous tissue

98

describe the movement range of a fibrous joint?

no movement

99

what type of joints are the joints holding skull bones together?

fibrous joint

100

in a cartilaginous joint, what are the bones united by?

cartilage

101

describe the movement range of a cartilaginous joint?

limited movement

102

what type of joints are intervertebral discs?

cartilaginous joint

103

what type of joint is the pubic symphysis?

cartilaginous joints

104

what type of joins are costochondral joints?

cartilaginous joints

105

in a synovial joint, what are the bones separated by?

a joint cavity containing synovial fluid

106

in a synovial joint, what is the joint capsule made of?

fibrous capsule

107

what is the inner aspect of the fibrous capsule of a synovial joint lined with?

synovial membrane

108

what cells within the synovial membrane produce synovial fluid?

fibroblasts

109

in a synovial joint, what are the articular surfaces of bones covered with?

hyaline cartilage

110

compare a simple synovial joint to a compound synovial joint?

simple- only one pair of articular surfaces
compound- more than one pair of articular surfaces

111

what is the function of ligaments in a joint?

to provide a stabilising influence

112

what is the function of synovial fluid in a synovial joint?

lubricates joint
reduces friction
aid in nutrition of articular cartilage and removal of waste

113

what 3 things within synovial fluid provide joint lubrication?

-cartilage interstitial fluid
-synovium-derived hyaluronic acid (mucin)
-synovium-derived lubricin

114

what is the name of cartilage cells?

chondrocytes

115

why is the synovial fluid quite viscous?

due to the hyaluronic acid (mucin)

116

what is the appearance of normal synovial fluid?

colourless

117

when does the synovial fluid WBC count increase?

inflammatory arthritis
septic arthritis

118

what colour does the synovial fluid turn during haemorrhagic arthritis?

red

119

what is the viscosity of normal synovial fluid?

high

120

what is the clarity of normal synovial fluid?

transparent

121

what is the viscosity of inflammatory synovial fluid?

low

122

what is the colour of inflammatory synovial fluid?

straw-yellow

123

what is the clarity of inflammatory synovial fluid?

translucent

124

what is the viscosity of septic synovial fluid?

variable

125

what is the colour of septic synovial fluid?

variable

126

what is the clarity of septic synovial fluid?

opaque

127

what are the functions of articular cartilage?

provides a low friction lubricated gliding surface
distributes pressure

128

what zone makes up the subchondral bone section of articular cartilage?

calcified zone

129

what happens to cartilage water content as age increases?

water content decreases

130

what happens to type II collagen content of cartilage as age increases?

cartilage content decreases

131

what are the 3 main substances of the extra cellular matrix of hyaline cartilage?

water
collagen (mainly type II)
proteoglycan

132

within cartilage, where is the highest concnetration of proteoglycan found?

middle and deep zone

133

what is the function of water within cartilage?

maintains resiliency of the tissue
contributes to nutrition and lubrication system

134

what is the function of collagen within cartilage?

maintains cartilage architecture
provides strength

135

what is the function of proteoglycan within cartilage?

load bearing

136

how does articular cartilage receive nutrients and O2?

via synovial fluid

137

what is the effect of TNF on proteoglycan synthesis?

inhibits
(catabolic)

138

what is the effect of IL-1 on proteoglycan synthesis?

inhibits
(catabolic)

139

what is the effect of tumour growth factor on proteoglycan synthesis?

stimulates
(anabolic)

140

what is the effect of insulin-like growth factor on proteoglycan synthesis?

stimulates
(anabolic)

141

what are the 2 main markers of cartilage degradation?

1. increased serum and synovial keratin sulphate
2. increased synovial type II collagen

142

what are the main 3 effects on the subchondral bone following cartilage wear and tear?

-cyst formation
-sclerosis in subchondral bone
-osteophyte formation (bony projection)

143

deposition of needle-shaped uric acid cystals within the joints causes what condition?

gouty arthritis

144

deposition of rhomboid-shaped calcium pyrophosphate cyrastas causes what condition?

pseudogout

145

What are the 3 forms of pain?

nociceptive pain
inflammatory pain
pathological pain

146

what are nociceptors?

nociceptors are peripheral primary sensory afferent neurones that are activated by intense stimuli that are noxious

147

why is nociceptive pain adaptive?

serves as an early warning system to detect and minimise contact with damaging stimuli
(inscribes memories that cause avoidance)

148

why is inflammatory pain adaptive and protective?

caused by activation of the immune system
(to injury or infection)

149

how does inflammatory pain affect further sensory stimuli?

pain hypersensitivity (heightened sensitivity to noxious stimuli)
allodynia *innocuous stimuli now elicit pain

150

how does inflammatory pain help in healing a damaged body part?

discourages physical contact
discourages movement

151

why is pathological pain known as maladaptive?

no protective function

152

what does pathological pain result from?

abnormal nervous system function:
neuropathic or dysfunctional
(disease state of nervous system)

153

what congenital insensitivity to pain caused by?

loss of function mutations in a particular voltage-activated Na+ channel which is highly expressed in nociceptive neurones

154

what nociceptors respond to noxious mechanical and thermal stimuli and mediate fast pain? (stabbing, prickiling sensations)

Adelta-fibres

155

what nociceptors respond to all noxious stimuli and mediate slow pain? (burning, throbbing, aching)

C-fibres

156

compare the myelination of Adelta fibres to C-fibres

Adelta fibres- myelinated
C-fibres- unmyelinated

157

how do nociceptors elicit a depolarising receptor potential in response to a noxious sitmuli?

open cation selecive ion channels

158

why do a subset of C-fibres (peptidergic) have an efferent function of releasing pro-inflammatory mediators?

to contribute to neurogenic inflammation

159

how does long term noxious stimulation contribute to hyperalgesia and allodynia?

increases spinal excitability

160

what is the primary neurotransmitter between the nociceptor primary afferent and second order neurone in the dorsal horn?

glutamate

161

where do primary afferent axons terminate in the spinal cord?

dorsal horn of the spinal cord in laminae of Rexed

162

where do nociceptive C and Adelta fibres terminate usually?

dorsal horn of spinal cord in laminae I and II of Rexed

163

second order neurones ascend the spinal cord in which 2 tracts of the anterolateral system?

spinothalmic tract
spinoreticular tract

164

projections from Adelta fast pain are transmitted by second order neurones in which tract of the anterolateral system of the spinal cord?

spinothalmic tract

165

projections from C-fibre slow pain are transmitted by second order neurones in which tract of the anterolateral system of the spinal cord?

spinoreticular tract