Physiology Flashcards
(165 cards)
1
Q
What is a motor unit?
A
the alpha motor neuron and all the skeletal muscle fibres it innervates
2
Q
if the alpha motor neurone supplies an area with fine motor control, will they have many or few muscle fibres?
A
few
3
Q
if the alpha motor neurone supplies an area with muscles needed for force, will they have many or few muscle fibres?
A
many
4
Q
what is the functional unit of a muscle?
A
sarcomere
5
Q
compare cardiac muscle and skeletal muscle in terms of gap junctions?
A
cardiac muscles have gap junction (so AP can spread)
skeletal muscles don’t have gap junctions
6
Q
compare cardiac muscle and skeletal muscle in terms of neuromuscular junctions?
A
cardiac muscle does not contain neuromuscular junctions
skeletal muscle contains neuromuscular junctions
7
Q
when is skeletal muscle at optimum length?
A
resting
8
Q
when is cardiac muscle at optimum length?
A
when stretched
9
Q
compare cardiac muscle and skeletal muscle in terms of initiation and propagation of contraction?
A
cardiac muscle- myogenic (pacemaker potential)
skeletal muscle- neurogenic
10
Q
compare cardiac muscle and skeletal muscle in terms of Ca++ input?
A
cardiac muscle- Ca++ from ECF and sarcoplasmic reticulum
skeletal muscle- Ca++ entirely from sarcoplasmic reticulum
11
Q
in skeletal muscle fibres, when is Ca++ released from lateral sacs of the sarcoplasmic reticulum?
A
when surface action potential spreads down the T tubules
12
Q
what are T tubules?
A
extensions of the surface membrane that dip into the muscle fibre
13
Q
what is the transmitter at the neuromuscular junction?
A
acetylcholine
14
Q
what is a myofibril?
A
made of lots of sarcomeres aligned head to tail
intracellular
15
Q
how far do skeletal muscle fibres (cells) usualy extend?
A
the entire length of the muscle
16
Q
how are skeletal muscles attached to the skeleton?
A
by tendons
17
Q
how are myofibrils positioned within a cell?
A
parallel to each other
18
Q
what lines form the borders of the sarcomere?
A
Z lines
19
Q
what is an A band?
A
the area of myosin
with or without overlapping actin
20
Q
what is an I band?
A
the area of actin without any overlapping myosin
21
Q
what is a H zone?
A
the area of myosin without any overlapping actin
22
Q
what is the M line?
A
extends vertially down the middle of the A band within the centre of the H zone
23
Q
what is required for both contraction and relaxation?
A
ATP
24
Q
what is required to switch on cross bridge formation between actin and myosin?
A
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
