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Physiology Flashcards

1
Q

what are the 3 types of muscle in the human body?

A

skeletal
cardiac
smooth

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2
Q

what are the 3 types of muscle capable of?

A

developing tension & producing movement through contraction

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3
Q

which types of muscle are striated?

A

skeletal & cardiac

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4
Q

what do striations look like?

A

dark bands & light bands

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5
Q

what are the light bands in striations caused by?

A

actin (thin)

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6
Q

what are the dark bands in striations caused by?

A

myocin (thick)

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7
Q

what are the physiological functions of skeletal muscles?

A
  • maintenance of posture
  • purposeful movement in relation to external environment
  • respiratory movements
  • heat production
  • contribution to whole body metabolism
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8
Q

what are skeletal muscle fibres organised into?

A

motor units

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9
Q

what is one motor unit?

A

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

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10
Q

what does the number of muscle fibres per motor unit depend on?

A

the functions served by the muscle

  • strength - lots of muscle fibres
  • precision - fewer muscle fibres
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11
Q

how long is a muscle fibre?

A

the length of the muscle it’s in

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12
Q

what is the mechanism of the initiation of contraction in skeletal muscle?

A

neurogenic

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13
Q

what is the mechanism of the initiation of contraction in cardiac muscle?

A

myogenic

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14
Q

what two things are present in muscles that allow the propagation go contraction in skeletal muscle?

A

motor units & neuromuscular junctions present.

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15
Q

what one thing is present in muscles that allow the propagation go contraction in cardiac muscle?

A

gap junctions

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16
Q

where does the Ca++ from from to cause excitation coupling contraction in skeletal muscle?

A

Ca++ entirely from sarcoplasmic reticulum

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17
Q

where does the Ca++ from from to cause excitation coupling contraction in cardiac muscle?

A

Ca++ from ECF & sarcoplasmic reticulum

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18
Q

what does the gradation of contraction depend on in skeletal muscle?

A

1) motor unit recruitment

2) summation of contractions

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19
Q

what does the gradation of contraction depend on in cardiac muscle?

A

depends on the extent of heart filling with blood

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20
Q

what is excitation contraction coupling?

A

the process whereby the surface action potential results in activation of the contractile mechanism of the muscle fibre

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21
Q

where is Ca++ released from in skeletal muscle fibres & when?

A

released from the lateral sacs of the sarcoplasmic reticule when the surface action potential spreads down the transverse tubules (T-tubules)

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22
Q

what are the muscle fibres in skeletal muscle bundled by?

A

connective tissue

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23
Q

how are skeletal muscles usually attached to the skeleton?

A

by tendons

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24
Q

what intracellular structure does each muscle fibre contain lots of?

A

myofibrils

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25
Q

what do myofibrils have alternating segments of?

A

thick (myocin) & thin (acctin) protein filaments

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26
Q

how are actin & myosin arranged within each myofibril?

A

arranged not sacromeres

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27
Q

what are sarcomeres?

A

functional units of skeletal muscle

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28
Q

what is the functional unit of any organ?

A

the smallest component capable of performing all the functions of that organ

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29
Q

where is the sarcomere found?

A

between two z-lines which connect the thin filaments of 2 adjoining sacromeres

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30
Q

what are the four zones of a sarcomere?

A

the A-band, the H-zone, the M-line & the I-band

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31
Q

what is the A-band?

A

Made up of thick filaments along with portions of thin filaments that overlap in both ends of thick filaments

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32
Q

what is the H-zone?

A

Lighter area within middle of A-band where thin filaments don’t reach

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33
Q

what is the M-line?

A

Extends vertically down middle of A-band within the centre of H-zone

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34
Q

what is the I-band?

A

Consists of remaining portion of thin filaments that do not project in A-band

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35
Q

how is muscle tension produced?

A

by the sliding of actin filaments on myocin filaments

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36
Q

what does force generation depend on?

A

ATP-dependent interaction between thick (myocin) & thin (actin) filaments

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37
Q

what is required in both contraction & relaxation?

A

ATP

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38
Q

how does Ca++ switch on cross bridge formation?

A 
Ca2+ binds to troponin. This results in 
repositioning of
troponin-
tropomyocin
complex to 
uncover the cross bridge binding sites on actin.
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39
Q

what two primary factors does gradation (strength of contraction) of skeletal muscle depend on?

A

number of muscle fibres contracting within the muscle & tension developed by each contracting muscle fire

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40
Q

what is motor recruitment?

A

a stronger contraction can be achieved by stimulation of more motor units

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41
Q

what kind of motor unit recruitment can help prevent muscle fatigue?

A

a synchronous motore units recruitment during sub maximal contraction

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42
Q

what does tension developed by each contracting muscle fibre depend on?

A
  • frequency of stimulation & summation of contraction
  • length of muscle fibre at the onset of contraction
  • thickness of muscle fibre
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43
Q

in skeletal muscle is the AP or the muscle twitch shorter?

A

the AP

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44
Q

how can you bring about a stronger contraction?

A

summate twitches to bring about a stronger contraction through repetitive fast stimulation of skeletal muscle

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45
Q

what happen if a muscle fibre is restimulated after it has completely relaxed?

A

the magnitude of the second twitch will be the same as the first twitch

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46
Q

what happens if a muscle fibre is restimulated before it has completely relaxed?

A

the second twitch is added onto the first twitch resulting in summaion

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47
Q

what happens if a muscle fibre is stimulated so rapidly that it does not have an opportunity to relax at all?

A

a maximal sustained contraction known as tetanus occurs

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48
Q

what prevents cardiac muscle from being tetanised?

A

the ling refractory period

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49
Q

what does a single twitch produce?

A

little tension & is not useful in bringing about meaningful skeletal muscle activity

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50
Q

if the frequency of stimulation is increased what happens to the tension developed by skeletal muscle?

A

increases

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51
Q

when can maximal tetanic contraction be achieved?

A

when the muscle is at its optimal length before the onset of contracion

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52
Q

what is the optimal length of muscle?

A

the point of optimal overlap of thick filament cross bridges & thin filaments cross bridge binding sites.

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53
Q

when does the percentage of maximal titanic contraction that can be achieved decrease?

A

when the muscle fibres is longer or shorter than optimum length before contraction

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54
Q

why does the muscle fibre being longer decrease the percentage of maximal titanic contraction that can be achieved?

A

When it is longer, fewer thin-filament binding sites are accessible for binding with thick-filament cross bridges, because the thin filaments are pulled out from between the thick filaments

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55
Q

why does the muscle fibre being shorter decrease the percentage of maximal titanic contraction that can be achieved?

A

When the fiber is shorter, fewer thin-filament binding sites are exposed to thick-filament cross bridges because the thin filaments overlap & further shortening and tension development are impeded as the thick filaments become forced against the Z lines

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56
Q

what is resting muscle length in the body?

A

optimal length

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57
Q

how much can muscles cary beyond their optimal length?

A

30% due to skeletal attachments

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58
Q

how is skeletal muscle tension transmitted to bone?

A

as a result of cross bridge cycling (contractile component) it is transmitted via the stretching & tightening of muscle connective tissue & tendon (elastic component)

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59
Q

what is isotonic contractions used for?

A

body movements & moving objects

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60
Q

what happens in isotonic contraction?

A

muscle tension remains constant as the muscle length changes

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61
Q

what is isometric contraction used for?

A

supporting objects in fixed positions & maintaining body posture

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62
Q

what happens in isometric contraction?

A

muscle tension develops at constant muscle length

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63
Q

how is muscle tension transmitted to the bone in the two types of contraction?

A

via elastic components of muscle

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64
Q

what 4 things can impairment of skeletal muscle function be caused by?

A

(1)Intrinsic disease of muscle (in the muscle itself)
(2) Disease of neuromuscular junction
(3) Disease of lower motor neurons
which supply the muscle
(4) Disruption of inputs to motor
unit

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65
Q

what main two types of myopathies are there?

A

genetic or acquired

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66
Q

what types of genetic myopathies can you get?

A
  • congenital
  • chronic degeneration of contractile elements
  • abnormalities in muscle membrane ion channels
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67
Q

what happens in congenital myopathies?

A

characteristic microscopic changes lead to reduced contractile ability of muscles

68
Q

give an example of a disease which involves the chronic degeneration of contractile elements

A

muscular dystrophy

69
Q

give an example of a disease which involves abnormalities in muscle membrane ion channels

A

myotonia

70
Q

what 3 types of acquired myopathies are there?

A
  • inflammatory
  • endocrine
  • toxic
71
Q

name an inflammatory myopathy

A

polymyosytis

72
Q

name an endocrine myopathy

A

Cushing syndrome or thyroid disease

73
Q

name a toxic myopathy

A

alcohol or statins

74
Q

what is a reflex action?

A

a stereotyped response to a specific stimulus i.e. the simplest form of coordinated movement

75
Q

what is the stretch reflex?

A

the simplest monosynaptic spinal reflex

76
Q

what type of feedback is the stretch reflex?

A

negative feedback

77
Q

what does the stretch reflex resist?

A

passive Chang ein muscle length to maintain optimal resting length of muscle

78
Q

what does the stretch reflex help to maintain?

A

posture e.g. while walking

79
Q

what is the sensory receptor in the stretch reflex?

A

the muscle spindle found in the muscle belly running parallel to ordinary muscle fibres

80
Q

what does stretching the muscle spindle do?

A

increase firing in the afferent neurones

81
Q

where do afferent neurones synapse?ion of the stretch reflex cause?

A

in the spinal cord with the alpha motor neurone (efferent limb of the stretch reflex) that innervate the stretched muscle

82
Q

what does activation of the stretch reflex cause?

A

contraction of the stretched muscle

83
Q

what is the stretch reflex coordinated by?

A

simultaneous relaxation of the antagonist muscle

84
Q

how can the stretch reflex be elicited?

A

by tapping the muscle tendon with a rubber hammer

85
Q

which spinal nerves are involved in the knee jerk?

A

L3 & L4

86
Q

which peripheral nerve is involved in the knee jerk?

A

femoral nerve

87
Q

which spinal nerves are involved in the ankle jerk?

A

S1 & S2

88
Q

which peripheral nerve is involved in the ankle jerk?

A

tibial nerve

89
Q

which spinal nerves are involved in the biceps jerk?

A

C5 & C6

90
Q

which peripheral nerve is involved in the biceps jerk?

A

musculocutaneous nerve

91
Q

which spinal nerves are involved in the brachioradialis?

A

C5 & C6

92
Q

which peripheral nerve is involved in the brachioradialis?

A

radial nerve

93
Q

which spinal nerves are involved in the triceps jerk?

A

C6 & C7

94
Q

which peripheral nerve is involved in the triceps jerk?

A

radial nerve

95
Q

what are muscle spindles?

A

collection of specialised muscle fibres

96
Q

what are muscle spindles also known as?

A

intrafusal fibres

97
Q

what are ordinary muscle fibres known as?

A

extrafusal fibres

98
Q

what are the muscle spindles sensory nerve endings known as?

A

annulospiral fibres

99
Q

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

A

increases

100
Q

what nerves supply the muscle spindle?y

A

have their own efferent (motor) nerve supple (gamma motor neurone)

101
Q

what do gamma motor neurones adjust to keep muscle spindles’ sensitivity during contraction?

A

adjust the level of tension in the muscle spindles

102
Q

does the contraction of intrafusal fibres contribute to the overall strength of muscle contraction?

A

no

103
Q

what are the main differences between different types of skeletal muscle fibres?

A
  • enzymatic pathways for ATP synthesis
  • resistance to fatigue
  • activity of myosin ATPase
104
Q

which muscle fibres are more resistant to fatigue?

A

muscle fibres with a greater capacity to synthesise ATP

105
Q

what does the activity of myosin ATPase determine?

A

the spread at which energy is made available for cross bridge cycling i.e. speed of contraction

106
Q

what 3 metabolic pathways can supply muscle fibres with ATP?

A
  • Transfer of high energy phosphate from creatine Phosphate to ADP - immediate source for ATP
  • Oxidative phosphorylation: main source when O2 is present
  • Glycolysis: main source when O2 is not present
107
Q

what are slo oxidative type 1 fibres used for?

A

used mainly for prolonged relatively low work aerobic activities e.g. maintenance of posture, walking

108
Q

what are fast oxidative type 2a fibres used for?

A

use both aerobic and anaerobic metabolism and are useful in prolonged relatively moderate work activities e.g. jogging

109
Q

what are fast glycolytic type 2b fibres used for?

A

use anaerobic metabolism and are mainly used for short-term high intensity activities e.g. jumping

110
Q

name 3 investigations useful for neuromuscular diseases

A
  • electromyography (useful to differentiate between primary muscle disease or neurological disease)
  • nerve conduction studies (determine functional integrity of peripheral nerves)
  • muscle enzymes
111
Q

what is skeletal muscle innervated by?

A

motor neurones with myelinated axons & cell bodies in the spinal cord or brain stem

112
Q

what does the motor neurone axon divide into unmyelinated branches?

A

near to the muscle fibre

113
Q

what does each unmyelinated branch of the motor neurone axon innervate?

A

an individual muscle cell

114
Q

what do the unmyelinated branches of the motor neurone axon further divide into

A

multiple fine branches ending in a terminal bouton

115
Q

what does each terminal bouton form a chemical synapse with?

A

the muscle membrane at the neuromuscular junction

116
Q

what are action potential arising in the cell body conducted via?

A

the axon to the boutons causing the release of the transmitter acetylcholine

117
Q

what are the key features of the skeletal neuromuscular junction?

A
  • terminal bouton & surrounding schwann cell
  • synaptic vesicles
  • synaptic cleft
  • end plate region of muscle cell membrane
118
Q

where do synaptic vesicles awaiting release cluster?

A

active zones

119
Q

where are the nicotinic acetylcholine receptors located?

A

regions of the junctional folds that face the active zones

120
Q

what is acetylcholine synthesised from?

A

choline & acetyl coenzyme A

121
Q

what do nicotinic ACh receptors assemble as?

A

pentamer of glycoprotein subunits that surround a central cation selective pore

122
Q

the gate in the nicotinic ACh receptor opens when what?

A

2 molecules of ACh bid to the exterior of the receptor

123
Q

what enters the muscle cell when the gat of the nicotinic ACh receptor is open?

A

sodium

124
Q

what leaves the muscle cell when the gate of the nicotinic ACh receptor is open?

A

potassium

125
Q

is influx of sodium or efflux of potassium greater at resting membrane potential?

A

influx of sodium is greater

126
Q

what is the e.p.p?

A

end plate potential

caused by the activation of nicotinic ACh receptors at the endplate & is a graded response

127
Q

If large enough, what does the e.p.p trigger?

A

the opening of voltage-activated Na+ channels around the end plate causing an action potential

128
Q

what does one action potential in the motor nerve normally trigger?

A

one action potential in the muscle and a subsequent twitch

129
Q

where does the action potential need to arrive at to trigger the release of calcium from the sarcoplasmic reticulum?

A

T-tubule triggers

130
Q

what does the release of calcium from the sarcoplasmic reticulum cause?

A

contraction by interacting with troponin associated with the myofibrils

131
Q

what is the rapid termination of neuromuscular transmission the result of?

A

hydrolysis of ACh by acetylcholinesterase (AChE)

132
Q

what does AChE hydrolyse ACh to?

A

choline and acetate

133
Q

what happens to the viscosity and elasticity of synovial fluid during rapid movement?

A

decreased viscosity

increased elasticity

134
Q

what does normal synovial fluid look like?

A

clear & colourless

135
Q

how do the zones of articular cartilage differ?

A

in organisation of collagen fibres & relative content of cartilage components

136
Q

name the 4 zones of articular cartilage

A

superficial zone
middle zone
deep zone
calcified zone

137
Q

what is the function of water in cartilage?

A

maintains the resilience of the tissue & contributes to the nutrition & lubrication system (705)

138
Q

what is the function of collagen in cartilage?

A

maintain cartilage architecture and provides tensile stiffness & strength (20%)

139
Q

what is the function of proteoglycan in cartilage?

A

responsible for the compressive properties associated with load bearing (10%)

140
Q

which cells synthesise, organise, degrade & maintain the ECM>

A

chondrocytes

141
Q

what do catabolic factors do to the cartilage matrix?

A

stimulate proteolytic enzymes & inhibit proteoglycan synthesis

142
Q

name two catabolic factors

A

tumour necrosis factor-alpha

interleukin-1

143
Q

what do anabolic factors do to the cartilage matrix?

A

stimulate proteoglycan synthesis & counteract effects of IL-1

144
Q

name two anabolic factors

A

tumour growth factor-beta

insulin-like growth factor-1

145
Q

what happens to serum & synovial keratin sulphate levels during cartilage breakdown?

A

increase

146
Q

other than cartilage breakdown, when do serum & synovial keratin sulphate levels rise?

A

with age & in OA

147
Q

what happens to type 2 collagen in synovial fluid during cartilage breakdown?

A

increase

148
Q

when is type 2 collagen in synovial fluid particularly useful?

A

in evaluating cartilage erosion

149
Q

what are the 3 types of pain?

A

nociceptive pain
inflammatory pain
pathological pain

150
Q

which type of pain is maladaptive?

A

pathological pain

151
Q

what are nociceptors?

A

specific peripheral primary sensory afferent neurones

152
Q

when are nociceptors activated?

A

preferentially by intense stimuli that are noxious (e.g. thermal, mechanical, chemical)

153
Q

what type of neurones are nociceptors?

A

first order neurones that relay information to second order in the CNS by chemical synaptic transmission

154
Q

what causes inflammatory pain?

A

activation of the immune system in injury or infection

155
Q

what does inflammatory pain cause?

A

pain hypersensitivity and allodynia

156
Q

what does inflammatory pain assist with?

A

healing of a damaged body part by discouraging physical contact and movement

157
Q

what does pathological pain result from?

A

abnormal nervous system function

158
Q

what are the two types of pathological pain?

A

neuropathic or dysfunctional

159
Q

what two fibre types compromise nociceptors?

A

Aδ-fibres

C-fibres

160
Q

what are Aδ-fibres?

A

mechanical/thermal nocicepetors that are thinly myelinated

161
Q

what do Aδ-fibres do?

A

respond to noxious mechanical and thermal stimuli, mediated “first” or fast pain

162
Q

what are C-fibres?

A

unmyelinated

163
Q

what do C-fibres do?

A

collectively respond to all noxious stimuli, mediate “second” or slow pain

164
Q

which receptors are stimulated by thermal stimuli?

A

members of the transient receptor potential (TRP) family, particularly TRPV1

165
Q

which receptors are stimulated by H+?

A

acid sensing ion channels (ASICs)

166
Q

which receptors are stimulated by ATP?

A

P2X and P2Y

167
Q

which receptors are stimulated by bradykinin?

A

B2 receptors

Musculoskeletal (22 decks)

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