15 nervous coordination and muscles Flashcards
1
Q
what is a neurone?
A
specialised cell that is adapted to its function of carrying electrical impulses from one part of the body to another
2
Q
what are the 3 types of neurones?
A
sensory, relay, motor
3
Q
what does the motor neuron carry an electrical impulse to and from?
A
CNS to effector
4
Q
what is the CNS?
A
central nervous system- brain and spinal cord
5
Q
what is the PNS?
A
peripheral nervous system- nerves that originate from brain or spinal cord
6
Q
what can the peripheral nervous system be divided into?
A
autonomic
voluntary (somatic)
7
Q
what can the autonomic nervous system be divided into?
A
sympathetic
parasympathetic
8
Q
what does the sympathetic branch of the nervous system do?
A
fight or flight:
increase heart rate and blood pressure
9
Q
what does the parasympathetic branch of the nervous system do?
A
decrease heart rate and blood pressure
10
Q
what is the structure of a motor neuron?
A
dendrites
cell body
nucleus
myelin sheath
node of ranvier
schwann cell
axon
terminal end branch
11
Q
what forms neurotransmitters in the cell body of a neuron?
A
80s ribosomes on the RER
12
Q
what is the function of the myelin sheath?
A
acts as an electrical insulator
increases the speed of electrical impulses
13
Q
what are the 6 stages of nerve impulses?
A
- resting potential
- depolarisation
- action potential
- repolarisation
- hyper-polarisation
- propagation
14
Q
what does potential mean in a nerve impulse?
A
ability to change
15
Q
what type of impulse is a nerve impulse?
A
an electrical impulse
16
Q
why are nerve cells able to transmit an electrical impulse?
A
because there is a difference in electrical potential across the membrane
17
Q
what can a membrane potential difference be measured with?
A
a voltmeter
18
Q
at rest when there is no nerve impulse in the neuron, what is the electrical potential difference?
A
-70 mV
19
Q
briefly, what is a resting potential?
A
when the axon is at rest (not transmitting a nerve impulse)
20
Q
what 2 ions are responsible for the resting potential?
A
K+
Na+
21
Q
which ion has a higher concentration on the outside of the neurone at resting potential?
A
Na+
22
Q
which ion has a higher concentration on the inside of the neurone at resting potential?
A
K+
23
Q
how is the difference in electrical potential with the ions maintained?
A
sodium potassium pump
24
Q
how does the sodium potassium pump work?
A
moves 2 K+ in and 3 Na+ out of the cell using energy from ATP
25
what other proteins are within the cell membrane of a neurone?
voltage gated channel proteins for both K+ and Na+
26
in a resting neurone, is the Na+ voltage gated channel protein open or closed?
closed
27
in a resting neurone, is the K+ voltage gated channel protein open or closed?
mainly closed but some are open/leaky
28
what is the net result of charge due to the proteins embedded in the neurone membrane during resting potential?
more positive ions on the outside of the neuron than inside so the inside is slightly negative compared to the outside
29
what is the value of resting potential?
-70mV
30
what causes depolarisation?
stimulus
31
what has to happen before the membrane depolarises?
threshold
32
what is the value of threshold?
around -55mV
33
what happens to Na+ channel proteins during depolarisation
they are all open
34
what happens to K+ channel proteins during depolarisation?
closed (leaky)
35
what happens due to all Na+ channel proteins being open during depolarisation?
Na+ diffuse into the membrane so the charge is more positive inside
36
is the charge more or less positive inside the membrane during depolarisation?
more positive
37
what generates an action potential?
high concentration of positive ions inside the cell
38
what value does depolarisation go to?
+40mV
39
what happens to channel proteins during repolarisation?
at +40mV Na+ channel proteins close and K+ channel proteins open
40
what happens to the Na+ channel proteins during repolarisation?
close
41
what happens to the K+ channel proteins during repolarisation?
open
42
what happens due to all K+ channel proteins being open during repolarisation?
K+ ions diffuse out- down a concentration gradient
43
what is hyperpolarisation?
where the K+ channel proteins remain open longer than needed to reach resting potential
44
what value is hyperpolarisation?
around -90mV
45
how is hyperpolarisation fixed?
sodium potassium pump
46
what is meant by the all or nothing response?
sub-threshold- no action potential will occur
above threshold- full size action potential occurs regardless of intensity of stimulus
47
what does the intensity of a stimulus affect and not affect?
affects: frequency of action potentials
doesn't affect: size of action potential
48
define the refractory period
the time taken to restore the resting potential
49
explain impulse transmission along the axon
action potential passed along areas of the membrane
50
what are the factors affecting the speed of conduction of impulses?
1. myelin sheath and saltatory conduction
2. temperature
3. axon diameter
51
what is saltatory conduction?
how the impulse travels by jumping from one node of ranvier to the next node of ranvier
52
how does saltatory conduction affect the rate of transmission?
increases the rate of transmission as less of the axon needs to be polarised
53
how does saltatory conduction work?
the myelin sheath provides electrical insulation so depolarisation can only occur at the next nodes of ranvier
54
how does temperature affect the rate of transmission?
higher temp
increases the kinetic energy
increases the rate of diffusion
increases the rate of conduction
55
how does axon diameter affect the rate of transmission?
large axon diameter
greater speed of conduction
as larger membrane means more channel proteins
56
what does 'the synapse is unidirectional' mean?
- vesicles only found in the pre-synaptic neuron
- receptors only found in post-synaptic neuron
impulses only go from pre-synaptic to post-synaptic neuron
57
what happens when an action potential arrives at the terminal knob?
voltage gated Ca2+ channels open in the pre-synaptic membrane
58
what happens when Ca2+ channels open due to an action potential approaching the terminal knob?
Ca2+ diffuse in by facilitated diffusion and activate enzymes that cause vesicles to fuse with the pre-synaptic membrane
59
what do vesicles contain?
neurotransmitters (acetylcholine most of the time)
60
what happens to neurotransmitters when vesicles fuse with the pre-synaptic membrane?
neurotransmitter (acetylcholine) is released into synaptic cleft by exocytosis
61
what does exocytosis require?
ATP
62
what happens when the acetylcholine/neurotransmitter is released from the pre-synaptic neuron?
acetylcholine/neurotransmitter diffuses across the cleft and binds to specifically complementary receptors on the post-synaptic neuron
63
what happens when the neurotransmitter binds to the specifically complementary receptor on the post synaptic neuron?
Na+ channel proteins open allowing Na+ to diffuse in
64
explain how acetylcholine undergoes reabsorption in a cholinergic synapse
1. enzyme acetylcholinesterase hydrolyses acetylcholine into choline and ethanoic acid (breaks the ester bond)
2. choline and ethanoic acid diffuses back across synaptic cleft into the pre-synaptic neuron
3. ATP released used to resynthesise acetylcholine which is stored in vesicles again
65
what is the neuromuscular junction?
the synapse between a motor neuron and a muscle cell
66
what neurotransmitter do neuromuscular junctions use?
acetylcholine
67
what does the acetylcholine in a neuromuscular junction bind to?
nicotinic cholinergic receptors
68
what 3 features does a neuromuscular junction have that is different to a cholinergic synapse?
1. post-synaptic membranes have folds that form clefts and increase surface area so more enzymes
2. more receptors
3. always triggers a response in muscle cell
69
what is summation?
build up of neurotransmitters
70
what are the 2 types of summation?
spatial
temporal
71
what is spatial summation?
1. multiple neurons have the same synapse
2. action potentials arrive from different neurons
3. causing threshold and an action potential
72
what is temporal summation?
1. only one pre-synaptic neurons
2. impulses arrive rapidly after eachother (cumulative effect)
3. causing threshold and an action potential
73
describe how the inhibition of acetylcholinesterase affects the action of synapses
1. acetylcholine not hydrolysed
2. Na+ continue to enter and depolarise post-synaptic neuron
74
what is fatigue in a neurotransmitter?
where the neurotransmitter release rate is higher than the rate it is reformed
75
what happens if a neurotransmitter is fatigued?
pre-synaptic neuron can't release enough neurotransmitter to generate an action potential
76
what does an excitatory neurotransmitter do?
1. more likely to generate action potential
2. by making the resting potential of the post-synaptic neuron less negative
3. so less Na+ are required to reach threshold
77
what does an inhibitory neurotransmitter do?
1. less likely to generate action potential
2. by making resting potential in post-synaptic neuron more negative/hyperpolarised
3. so more Na+ are required to reach threshold
78
what 2 ways can drugs act on a synapse?
1. have excitatory effects
2. have inhibitory effects
79
what are the types of muscle?
skeletal
smooth
cardiac
80
describe how a smooth muscle works
contracts without conscious control
81
where are smooth muscles located?
found in walls of internal organs
82
describe how a cardiac muscle works
myogenic, contracts without conscious control
83
where are the cardiac muscles located?
only within the heart
84
briefly, describe how a skeletal muscle works
used in locomotion (movement)
85
how is skeletal muscle attached to the bone?
through tendons
86
what do skeletal muscles contract in respond to?
the release of acetylcholine from motor neurons
87
do muscles pull in the same or opposite directions?
opposite
88
why can muscles only pull?
no active process in muscle relaxation
89
what is the contracting muscle group and the relaxing muscle group called?
contracting: agonist
relaxing: antagonist
90
name all the structures in a skeletal muscle
bone
tendon
sarcolemma
sarcoplasm (sarcoplasmic reticulum and many mitochondria)
myofibrils
myofilaments (actin and myosin)
91
name all the structures in a myofibril of a skeletal muscle
actin
myosin
I band
A band
M line
H zone
Z disc
sarcomere
92
what is actin in the myofibril anchored to?
Z disc
93
what is the myosin in myofibrils anchored to?
M line
94
when the muscle contracts, what part of the myofibril shrinks?
sarcomere
I band
H zone
95
explain the sliding filament theory
1. calcium ions diffuse into myofibrils from sarcoplasmic reticulum
2. calcium ions bind to troponin and cause movement of tropomyosin
3. exposing the binding sites on the actin
4. myosin heads attach to binding sites on actin
5. ATP hydrolase hydrolysing ATP causes myosin heads to bend
6. pulling actin molecules
7. attachment of a new ATP molecule to each myosin head
causes myosin heads to detach
96
what is ATP required for in muscle contraction?
1. sliding of filaments
2. active transport of Ca2+ into sarcoplasmic reticulum
97
describe the role of phosphocreatine in muscle contraction
1. provides phosphate group
2. to synthesise ATP
98
what are the two types of muscle fibres?
fast and slow twitch
99
what kind of contractions are slow and fast twitch fibres used in?
slow: slow sustained contractions
fast: rapid, strong contractions
100
how long do the contractions controlled by slow and fast twitch muscle fibres last?
slow: long time period
fast: small time period
101
are fast and slow muscle fibres slow or fast to fatigue?
slow: slow to fatigue
fast: fast to fatigue
102
why are slow twitch muscle fibres slow to fatigue?
because they are specialised to aerobic respiration so no build up of lactate
103
why are fast twitch muscle fibres fast to fatigue?
because they are specialised to anaerobic respiration ad therefore build up lactate
104
is phosphocreatine-ATP used within slow or fast twitch muscle fibres?
fast twitch
105
describe the mitochondria in slow and fast twitch muscle fibres
slow: many large mitochondria
fast: fewer small mitochondria
106
what do slow twitch muscle fibres have a high concentration of, which fast twitch muscle fibres have a low concentration of?
(apart from mitochondria)
myoglobin
107
describe the concentration of capillaries in slow and fast twitch muscle fibres
slow: higher concentration
fast: lower concentration
108
describe glycogen in slow and fast twitch muscle fibres
slow: less glycogen as aerobic respiration breaks down into glucose
fast: more glycogen as glucose is required because anaerobic respiration yields less ATP
