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the nervous system Flashcards

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1
Q

what type of nervous system does hyrda have?

A

nerve nets

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2
Q

what are the properties of nerve nets?

A

no CNS
non-myelinated axons
slow conduction speed
do not possess many receptors/effectors
made of only one type of nerve cell

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3
Q

what does the human nervous system do?

A

detects changes inside body or in outside environment
detects a stimulus and initiates a response

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4
Q

what is the CNS made up of?

A

brain
spinal chord

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5
Q

what is the PNS made up of?

A

sensory neurones
motor neurones

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6
Q

what do sensory neurones do?

A

carries nerve impulses from receptor cells to co-ordinator in CNS

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7
Q

what do relay neurones do?

A

receives impulses from sensory neurone and sends impulses to motor neurone

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8
Q

what do motor neurones do?

A

carries impulses from co-ordinator to effector (muscle/gland)

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9
Q

what is a dendrite?

A

thin extension which carries impulses towards cell body

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10
Q

what is an axon?

A

long extension which transmits impulses away from the cell body

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11
Q

what does an axon terminal do?

A

secretes neurotransmitters

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12
Q

what does a schwann cell do?

A

supports and insulates neurones

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13
Q

what are nodes of Ranvier?

A

gaps where myelin is missing

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14
Q

what do nodes of Ranvier do?

A

allows rapid transmission of impulses

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15
Q

what is the reflex arc?

A

pathway taken by a nerve impulse during a reflex reaction (rapid automatic response)

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16
Q

where is the co-ordinator?

A

spinal cord

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17
Q

why do we need reflexes?

A

for protection of organism from dangerous situations

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18
Q

what is a neurone?

A

excitable cell able to change its resting potential

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19
Q

what is resting potential?

A

potential difference across membrane of a cell when no nervous impulse is being conducted

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20
Q

what do nervous impulses involve?

A

movement of Na+ and K+ ions in and out of the axon membrane

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21
Q

what are the different transport proteins in an axon?

A

Na+/K+ pump (NEEDS ATP)
voltage-gated Na+ channels
voltage-gated K+ channels
K+ channels (ALWAYS OPEN)

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22
Q

what is the normal potential difference in a neurone membrane?

A

-70mV

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23
Q

what does the Na+/K+ pump do?

A

actively pumps 2K+ in and 3Na+ out for every ATP molecule hydrolysed (active transport)
Na+ pumped faster

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24
Q

how is the resting potential reached?

Study These Flashcards
A

Na+/K+ actively being pumped out/in
creates gradient for Na+/K+
K+ channels always open to allow K+ ions to diffuse back in

25
how is an action potential created in a neurone?
resting potential depolarisation repolarisation hyperpolarisation
26
what causes depolarisation?
stimulus causes voltage-gated Na+ channels to open Na+ ions diffuse in rapidly down gradient inside of axon becomes positively charged (+40mV)
27
what causes repolarisation?
K+ channels and voltage-gated K+ channels diffuse K+ ions out down gradient axon becomes less positive inside
28
what causes hyperpolarisation?
more K+ diffuses out than Na+ in potential difference across membrane becomes more negative than resting potential
29
how is resting potential reached again after hyperpolarisation?
Na+/K+ pump pumps ions in to return to resting potential
30
what must happen for an action potential to occur?
depolarisation must exceed threshold value of -55mV stimulus weaker than threshold will not generate an action potential
31
how can you measure the transmission of a nerve impulse?
oscilloscope
32
what does an oscilloscope do?
measures potential difference across membrane (magnitude and speed)
33
what happens when an action potential is generated?
action potential travels rapidly to other end of neurone
34
what happens during the refractory period after an action potential has been generated?
voltage-gated Na+ channels close axon cannot transmit another action potential
35
what does the refractory period do?
stops action potential being generated in opposite direction stops second action potential being generated too close to the first
36
what are the factors that affect the speed of nerve impulse?
myelination diameter of axon temperature
37
how does myelination affect the speed of nerve impulse?
myelinated axons transmit action potentials faster they electrically insulate the axon depolarisation and action potential only occur at node of Ranvier so impulse can jump from node to node so speeds up transmission (salatory conditions)
38
what causes salatory conduction?
depolarisation and action potential only occur at node of Ranvier so impulse can jump from node to node so speeds up transmission
39
how does the diameter of the axon affect the speed of nerve impusle?
greater diameter means lower resistance to ion flower so greater speed of transmission
40
how does temperature affect the speed of nerve impusle?
as temperature increases to 40, speed of transmission increases as impulses need active transport and ATP ions move faster at higher temperatures as more kinetic energy
41
what are electrical synapses?
two membranes connected by a gap junction allows electrical impulse to be directly transferred
42
what are chemical synapses?
branches of axon lie close to dendrites of second neurone but do not touch impulses are transferred by a neurotransmitter
43
how does synaptic transmission occur?
nerve impulse arrives at synaptic end bulb impulse depolarises pre-synaptic membrane so Ca2+ channels open calcium enters membrane down concentration gradient influx of Ca2+ causes synaptic vesicles of neurotransmitters to move towards and fuse with the pre-synaptic membrane vesicles release their contents into synaptic cleft by exocytosis neurotransmitter diffuses across cleft neurotransmitter binds to complementary receptors on post-synaptic membrane receptor protein changes shape sodium channels open and sodium diffuses in down concentration gradient post-synaptic membrane becomes depolarises and initiates action potential
44
how does synaptic transmission occur (simple)?
nerve impulse at synaptic end bulb depolarises pre-synaptic membrane calcium channels open Ca2+ influx synaptic vesicles fuse with membrane and release neurotransmitters by exocytosis neurotransmitters diffuse across cleft and bind to receptors sodium channels open and sodium diffuses in post-synaptic membrane becomes depolarises and action potential is initiated
45
what enzyme can hydrolyse acetylcholine?
acetylcholinesterase
46
what does the hydrolysis of acetylcholine produce?
ethanoic acid and choline
47
how can you prevent acetylcholine from staying in the cleft?
taken up by pre-synaptic membrane Ca2+ transported out of pre-synaptic membrane so no exocytosis acetylcholine hydrolysed
48
what happens if acetylcholine stays in the synaptic cleft?
an action potential will constantly be initiated
49
what are the functions of synapses?
transmit impulses between neurones make sure impulses pass in only one direction allow junctions allow acclimatisation after repeated stimulation
50
what is temporal summation?
repeated depolarisation builds up to reach a threshold at which action potential is initiated
51
what are sedatives?
inhibits nervous system creates fewer action potential in post-synaptic neurones alcohol
52
what are stimulants?
more action potential in post-synaptic neurones
53
what are excitatory drugs?
stimulate nervous system creates more action potentials
54
what are inhibitory drugs?
inhibits nervous system reduces number of action potentials
55
what causes a tolerance to drugs?
synapses adapt e.g. makes new receptors more of drug needed to produce the same effect
56
how can drugs affect the nervous system?
initiate neurotransmitters by binding to receptors prevent breakdown of neurotransmitters block receptors on post-synaptic membrane prevent release of neurotransmitters
57
what does cocaine do?
attaches to dopamine transporter blocks normal recycling patterns build up of dopamine in synapse
58
what happens if you inhibit acetylcholinesterase?
acetylcholine builds up in cleft repeated firing of action potentials repeated effects brought out e.g. muscle spasm
59
what do psychoactive drugs do?
act on CNS alter brain function

bio component 3 (12 decks)

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