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bio component 3 > the nervous system > Flashcards

the nervous system Flashcards

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Biology 101 flashcards
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?

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
Q

how is an action potential created in a neurone?

A

resting potential
depolarisation
repolarisation
hyperpolarisation

26
Q

what causes depolarisation?

A

stimulus causes voltage-gated Na+ channels to open
Na+ ions diffuse in rapidly down gradient
inside of axon becomes positively charged
(+40mV)

27
Q

what causes repolarisation?

A

K+ channels and voltage-gated K+ channels diffuse K+ ions out down gradient
axon becomes less positive inside

28
Q

what causes hyperpolarisation?

A

more K+ diffuses out than Na+ in
potential difference across membrane becomes more negative than resting potential

29
Q

how is resting potential reached again after hyperpolarisation?

A

Na+/K+ pump pumps ions in to return to resting potential

30
Q

what must happen for an action potential to occur?

A

depolarisation must exceed threshold value of -55mV
stimulus weaker than threshold will not generate an action potential

31
Q

how can you measure the transmission of a nerve impulse?

A

oscilloscope

32
Q

what does an oscilloscope do?

A

measures potential difference across membrane (magnitude and speed)

33
Q

what happens when an action potential is generated?

A

action potential travels rapidly to other end of neurone

34
Q

what happens during the refractory period after an action potential has been generated?

A

voltage-gated Na+ channels close
axon cannot transmit another action potential

35
Q

what does the refractory period do?

A

stops action potential being generated in opposite direction
stops second action potential being generated too close to the first

36
Q

what are the factors that affect the speed of nerve impulse?

A

myelination
diameter of axon
temperature

37
Q

how does myelination affect the speed of nerve impulse?

A

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
Q

what causes salatory conditions?

A

depolarisation and action potential only occur at node of Ranvier so impulse can jump from node to node so speeds up transmission

39
Q

how does the diameter of the axon affect the speed of nerve impusle?

A

greater diameter means lower resistance to ion flower so greater speed of transmission

40
Q

how does temperature affect the speed of nerve impusle?

A

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
Q

what are electrical synapses?

A

two membranes connected by a gap junction
allows electrical impulse to be directly transferred

42
Q

what are chemical synapses?

A

branches of axon lie close to dendrites of second neurone but do not touch
impulses are transferred by a neurotransmitter

43
Q

how does synaptic transmission occur?

A

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
Q

how does synaptic transmission occur (simple)?

A

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
Q

what enzyme can hydrolyse acetylcholine?

A

acetylcholinesterase

46
Q

what does the hydrolysis of acetylcholine produce?

A

ethanoic acid and choline

47
Q

how can you prevent acetylcholine from staying in the cleft?

A

taken up by pre-synaptic membrane
Ca2+ transported out of pre-synaptic membrane so no exocytosis
acetylcholine hydrolysed

48
Q

what happens if acetylcholine stays in the synaptic cleft?

A

an action potential will constantly be initiated

49
Q

what are the functions of synapses?

A

transmit impulses between neurones
make sure impulses pass in only one direction
allow junctions
allow acclimatisation after repeated stimulation

50
Q

what is temporal summation?

A

repeated depolarisation builds up to reach a threshold at which action potential is initiated

51
Q

what are sedatives?

A

inhibits nervous system
creates fewer action potential in post-synaptic neurones
alcohol

52
Q

what are stimulants?

A

more action potential in post-synaptic neurones

53
Q

what are excitatory drugs?

A

stimulate nervous system
creates more action potentials

54
Q

what are inhibitory drugs?

A

inhibits nervous system
reduces number of action potentials

55
Q

what causes a tolerance to drugs?

A

synapses adapt e.g. makes new receptors
more of drug needed to produce the same effect

56
Q

how can drugs affect the nervous system?

A

initiate neurotransmitters by binding to receptors
prevent breakdown of neurotransmitters
block receptors on post-synaptic membrane
prevent release of neurotransmitters

57
Q

what does cocaine do?

A

attaches to dopamine transporter
blocks normal recycling patterns
build up of dopamine in synapse

58
Q

what happens if you inhibit acetylcholinesterase?

A

acetylcholine builds up in cleft
repeated firing of action potentials
repeated effects brought out e.g. muscle spasm

59
Q

what do psychoactive drugs do?

A

act on CNS
alter brain function

bio component 3 (12 decks)

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