Physiology Flashcards
(167 cards)
1
Q
what are the 3 types of muscle in the human body?
A
skeletal
cardiac
smooth
2
Q
what are the 3 types of muscle capable of?
A
developing tension & producing movement through contraction
3
Q
which types of muscle are striated?
A
skeletal & cardiac
4
Q
what do striations look like?
A
dark bands & light bands
5
Q
what are the light bands in striations caused by?
A
actin (thin)
6
Q
what are the dark bands in striations caused by?
A
myocin (thick)
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
8
Q
what are skeletal muscle fibres organised into?
A
motor units
9
Q
what is one motor unit?
A
a single alpha motor neurone and all the skeletal muscle fibres it innervates
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
11
Q
how long is a muscle fibre?
A
the length of the muscle it’s in
12
Q
what is the mechanism of the initiation of contraction in skeletal muscle?
A
neurogenic
13
Q
what is the mechanism of the initiation of contraction in cardiac muscle?
A
myogenic
14
Q
what two things are present in muscles that allow the propagation go contraction in skeletal muscle?
A
motor units & neuromuscular junctions present.
15
Q
what one thing is present in muscles that allow the propagation go contraction in cardiac muscle?
A
gap junctions
16
Q
where does the Ca++ from from to cause excitation coupling contraction in skeletal muscle?
A
Ca++ entirely from sarcoplasmic reticulum
17
Q
where does the Ca++ from from to cause excitation coupling contraction in cardiac muscle?
A
Ca++ from ECF & sarcoplasmic reticulum
18
Q
what does the gradation of contraction depend on in skeletal muscle?
A
1) motor unit recruitment
2) summation of contractions
19
Q
what does the gradation of contraction depend on in cardiac muscle?
A
depends on the extent of heart filling with blood
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
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)
22
Q
what are the muscle fibres in skeletal muscle bundled by?
A
connective tissue
23
Q
how are skeletal muscles usually attached to the skeleton?
A
by tendons
24
Q
what intracellular structure does each muscle fibre contain lots of?
A
myofibrils
25
what do myofibrils have alternating segments of?
thick (myocin) & thin (acctin) protein filaments
26
how are actin & myosin arranged within each myofibril?
arranged not sacromeres
27
what are sarcomeres?
functional units of skeletal muscle
28
what is the functional unit of any organ?
the smallest component capable of performing all the functions of that organ
29
where is the sarcomere found?
between two z-lines which connect the thin filaments of 2 adjoining sacromeres
30
what are the four zones of a sarcomere?
the A-band, the H-zone, the M-line & the I-band
31
what is the A-band?
Made up of thick filaments along with portions of thin filaments that overlap in both ends of thick filaments
32
what is the H-zone?
Lighter area within middle of A-band where thin filaments don’t reach
33
what is the M-line?
Extends vertically down middle of A-band within the centre of H-zone
34
what is the I-band?
Consists of remaining portion of thin filaments that do not project in A-band
35
how is muscle tension produced?
by the sliding of actin filaments on myocin filaments
36
what does force generation depend on?
ATP-dependent interaction between thick (myocin) & thin (actin) filaments
37
what is required in both contraction & relaxation?
ATP
38
how does Ca++ switch on cross bridge formation?
```
Ca2+ binds to troponin. This results in
repositioning of
troponin-
tropomyocin
complex to
uncover the cross bridge binding sites on actin.
```
39
what two primary factors does gradation (strength of contraction) of skeletal muscle depend on?
number of muscle fibres contracting within the muscle & tension developed by each contracting muscle fire
40
what is motor recruitment?
a stronger contraction can be achieved by stimulation of more motor units
41
what kind of motor unit recruitment can help prevent muscle fatigue?
a synchronous motore units recruitment during sub maximal contraction
42
what does tension developed by each contracting muscle fibre depend on?
- frequency of stimulation & summation of contraction
- length of muscle fibre at the onset of contraction
- thickness of muscle fibre
43
in skeletal muscle is the AP or the muscle twitch shorter?
the AP
44
how can you bring about a stronger contraction?
summate twitches to bring about a stronger contraction through repetitive fast stimulation of skeletal muscle
45
what happen if a muscle fibre is restimulated after it has completely relaxed?
the magnitude of the second twitch will be the same as the first twitch
46
what happens if a muscle fibre is restimulated before it has completely relaxed?
the second twitch is added onto the first twitch resulting in summaion
47
what happens if a muscle fibre is stimulated so rapidly that it does not have an opportunity to relax at all?
a maximal sustained contraction known as tetanus occurs
48
what prevents cardiac muscle from being tetanised?
the ling refractory period
49
what does a single twitch produce?
little tension & is not useful in bringing about meaningful skeletal muscle activity
50
if the frequency of stimulation is increased what happens to the tension developed by skeletal muscle?
increases
51
when can maximal tetanic contraction be achieved?
when the muscle is at its optimal length before the onset of contracion
52
what is the optimal length of muscle?
the point of optimal overlap of thick filament cross bridges & thin filaments cross bridge binding sites.
53
when does the percentage of maximal titanic contraction that can be achieved decrease?
when the muscle fibres is longer or shorter than optimum length before contraction
54
why does the muscle fibre being longer decrease the percentage of maximal titanic contraction that can be achieved?
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
55
why does the muscle fibre being shorter decrease the percentage of maximal titanic contraction that can be achieved?
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
56
what is resting muscle length in the body?
optimal length
57
how much can muscles cary beyond their optimal length?
30% due to skeletal attachments
58
how is skeletal muscle tension transmitted to bone?
as a result of cross bridge cycling (contractile component) it is transmitted via the stretching & tightening of muscle connective tissue & tendon (elastic component)
59
what is isotonic contractions used for?
body movements & moving objects
60
what happens in isotonic contraction?
muscle tension remains constant as the muscle length changes
61
what is isometric contraction used for?
supporting objects in fixed positions & maintaining body posture
62
what happens in isometric contraction?
muscle tension develops at constant muscle length
63
how is muscle tension transmitted to the bone in the two types of contraction?
via elastic components of muscle
64
what 4 things can impairment of skeletal muscle function be caused by?
(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
65
what main two types of myopathies are there?
genetic or acquired
66
what types of genetic myopathies can you get?
- congenital
- chronic degeneration of contractile elements
- abnormalities in muscle membrane ion channels
67
what happens in congenital myopathies?
characteristic microscopic changes lead to reduced contractile ability of muscles
68
give an example of a disease which involves the chronic degeneration of contractile elements
muscular dystrophy
69
give an example of a disease which involves abnormalities in muscle membrane ion channels
myotonia
70
what 3 types of acquired myopathies are there?
- inflammatory
- endocrine
- toxic
71
name an inflammatory myopathy
polymyosytis
72
name an endocrine myopathy
Cushing syndrome or thyroid disease
73
name a toxic myopathy
alcohol or statins
74
what is a reflex action?
a stereotyped response to a specific stimulus i.e. the simplest form of coordinated movement
75
what is the stretch reflex?
the simplest monosynaptic spinal reflex
76
what type of feedback is the stretch reflex?
negative feedback
77
what does the stretch reflex resist?
passive Chang ein muscle length to maintain optimal resting length of muscle
78
what does the stretch reflex help to maintain?
posture e.g. while walking
79
what is the sensory receptor in the stretch reflex?
the muscle spindle found in the muscle belly running parallel to ordinary muscle fibres
80
what does stretching the muscle spindle do?
increase firing in the afferent neurones
81
where do afferent neurones synapse?ion of the stretch reflex cause?
in the spinal cord with the alpha motor neurone (efferent limb of the stretch reflex) that innervate the stretched muscle
82
what does activation of the stretch reflex cause?
contraction of the stretched muscle
83
what is the stretch reflex coordinated by?
simultaneous relaxation of the antagonist muscle
84
how can the stretch reflex be elicited?
by tapping the muscle tendon with a rubber hammer
85
which spinal nerves are involved in the knee jerk?
L3 & L4
86
which peripheral nerve is involved in the knee jerk?
femoral nerve
87
which spinal nerves are involved in the ankle jerk?
S1 & S2
88
which peripheral nerve is involved in the ankle jerk?
tibial nerve
89
which spinal nerves are involved in the biceps jerk?
C5 & C6
90
which peripheral nerve is involved in the biceps jerk?
musculocutaneous nerve
91
which spinal nerves are involved in the brachioradialis?
C5 & C6
92
which peripheral nerve is involved in the brachioradialis?
radial nerve
93
which spinal nerves are involved in the triceps jerk?
C6 & C7
94
which peripheral nerve is involved in the triceps jerk?
radial nerve
95
what are muscle spindles?
collection of specialised muscle fibres
96
what are muscle spindles also known as?
intrafusal fibres
97
what are ordinary muscle fibres known as?
extrafusal fibres
98
what are the muscle spindles sensory nerve endings known as?
annulospiral fibres
99
what happens to the discharge from the muscle spindle endings as the muscle is stretched?
increases
100
what nerves supply the muscle spindle?y
have their own efferent (motor) nerve supple (gamma motor neurone)
101
what do gamma motor neurones adjust to keep muscle spindles' sensitivity during contraction?
adjust the level of tension in the muscle spindles
102
does the contraction of intrafusal fibres contribute to the overall strength of muscle contraction?
no
103
what are the main differences between different types of skeletal muscle fibres?
- enzymatic pathways for ATP synthesis
- resistance to fatigue
- activity of myosin ATPase
104
which muscle fibres are more resistant to fatigue?
muscle fibres with a greater capacity to synthesise ATP
105
what does the activity of myosin ATPase determine?
the spread at which energy is made available for cross bridge cycling i.e. speed of contraction
106
what 3 metabolic pathways can supply muscle fibres with ATP?
- 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
what are slo oxidative type 1 fibres used for?
used mainly for prolonged relatively low work aerobic activities e.g. maintenance of posture, walking
108
what are fast oxidative type 2a fibres used for?
use both aerobic and anaerobic metabolism and are useful in prolonged relatively moderate work activities e.g. jogging
109
what are fast glycolytic type 2b fibres used for?
use anaerobic metabolism and are mainly used for short-term high intensity activities e.g. jumping
110
name 3 investigations useful for neuromuscular diseases
- electromyography (useful to differentiate between primary muscle disease or neurological disease)
- nerve conduction studies (determine functional integrity of peripheral nerves)
- muscle enzymes
111
what is skeletal muscle innervated by?
motor neurones with myelinated axons & cell bodies in the spinal cord or brain stem
112
what does the motor neurone axon divide into unmyelinated branches?
near to the muscle fibre
113
what does each unmyelinated branch of the motor neurone axon innervate?
an individual muscle cell
114
what do the unmyelinated branches of the motor neurone axon further divide into
multiple fine branches ending in a terminal bouton
115
what does each terminal bouton form a chemical synapse with?
the muscle membrane at the neuromuscular junction
116
what are action potential arising in the cell body conducted via?
the axon to the boutons causing the release of the transmitter acetylcholine
117
what are the key features of the skeletal neuromuscular junction?
- terminal bouton & surrounding schwann cell
- synaptic vesicles
- synaptic cleft
- end plate region of muscle cell membrane
118
where do synaptic vesicles awaiting release cluster?
active zones
119
where are the nicotinic acetylcholine receptors located?
regions of the junctional folds that face the active zones
120
what is acetylcholine synthesised from?
choline & acetyl coenzyme A
121
what do nicotinic ACh receptors assemble as?
pentamer of glycoprotein subunits that surround a central cation selective pore
122
the gate in the nicotinic ACh receptor opens when what?
2 molecules of ACh bid to the exterior of the receptor
123
what enters the muscle cell when the gat of the nicotinic ACh receptor is open?
sodium
124
what leaves the muscle cell when the gate of the nicotinic ACh receptor is open?
potassium
125
is influx of sodium or efflux of potassium greater at resting membrane potential?
influx of sodium is greater
126
what is the e.p.p?
end plate potential
| caused by the activation of nicotinic ACh receptors at the endplate & is a graded response
127
If large enough, what does the e.p.p trigger?
the opening of voltage-activated Na+ channels around the end plate causing an action potential
128
what does one action potential in the motor nerve normally trigger?
one action potential in the muscle and a subsequent twitch
129
where does the action potential need to arrive at to trigger the release of calcium from the sarcoplasmic reticulum?
T-tubule triggers
130
what does the release of calcium from the sarcoplasmic reticulum cause?
contraction by interacting with troponin associated with the myofibrils
131
what is the rapid termination of neuromuscular transmission the result of?
hydrolysis of ACh by acetylcholinesterase (AChE)
132
what does AChE hydrolyse ACh to?
choline and acetate
133
what happens to the viscosity and elasticity of synovial fluid during rapid movement?
decreased viscosity
| increased elasticity
134
what does normal synovial fluid look like?
clear & colourless
135
how do the zones of articular cartilage differ?
in organisation of collagen fibres & relative content of cartilage components
136
name the 4 zones of articular cartilage
superficial zone
middle zone
deep zone
calcified zone
137
what is the function of water in cartilage?
maintains the resilience of the tissue & contributes to the nutrition & lubrication system (705)
138
what is the function of collagen in cartilage?
maintain cartilage architecture and provides tensile stiffness & strength (20%)
139
what is the function of proteoglycan in cartilage?
responsible for the compressive properties associated with load bearing (10%)
140
which cells synthesise, organise, degrade & maintain the ECM>
chondrocytes
141
what do catabolic factors do to the cartilage matrix?
stimulate proteolytic enzymes & inhibit proteoglycan synthesis
142
name two catabolic factors
tumour necrosis factor-alpha
| interleukin-1
143
what do anabolic factors do to the cartilage matrix?
stimulate proteoglycan synthesis & counteract effects of IL-1
144
name two anabolic factors
tumour growth factor-beta
| insulin-like growth factor-1
145
what happens to serum & synovial keratin sulphate levels during cartilage breakdown?
increase
146
other than cartilage breakdown, when do serum & synovial keratin sulphate levels rise?
with age & in OA
147
what happens to type 2 collagen in synovial fluid during cartilage breakdown?
increase
148
when is type 2 collagen in synovial fluid particularly useful?
in evaluating cartilage erosion
149
what are the 3 types of pain?
nociceptive pain
inflammatory pain
pathological pain
150
which type of pain is maladaptive?
pathological pain
151
what are nociceptors?
specific peripheral primary sensory afferent neurones
152
when are nociceptors activated?
preferentially by intense stimuli that are noxious (e.g. thermal, mechanical, chemical)
153
what type of neurones are nociceptors?
first order neurones that relay information to second order in the CNS by chemical synaptic transmission
154
what causes inflammatory pain?
activation of the immune system in injury or infection
155
what does inflammatory pain cause?
pain hypersensitivity and allodynia
156
what does inflammatory pain assist with?
healing of a damaged body part by discouraging physical contact and movement
157
what does pathological pain result from?
abnormal nervous system function
158
what are the two types of pathological pain?
neuropathic or dysfunctional
159
what two fibre types compromise nociceptors?
Aδ-fibres
| C-fibres
160
what are Aδ-fibres?
mechanical/thermal nocicepetors that are thinly myelinated
161
what do Aδ-fibres do?
respond to noxious mechanical and thermal stimuli, mediated "first" or fast pain
162
what are C-fibres?
unmyelinated
163
what do C-fibres do?
collectively respond to all noxious stimuli, mediate "second" or slow pain
164
which receptors are stimulated by thermal stimuli?
members of the transient receptor potential (TRP) family, particularly TRPV1
165
which receptors are stimulated by H+?
acid sensing ion channels (ASICs)
166
which receptors are stimulated by ATP?
P2X and P2Y
167
which receptors are stimulated by bradykinin?
B2 receptors
