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Biology > Nervous system > Flashcards

Nervous system Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

neurones

A

highly specialised cells that contain organelles such as nucleus, endoplasmic reticulum, golgi, ribosomes and mitochondria in the cell body, as well as dendrites and axons

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2
Q

motor neurone

A
  • cell body in spinal cord or brain
  • axons can be very long
  • cell body and dendrites on one end of the axon, axon terminals on the opposite end
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3
Q

sensory neurone

A
  • cell body in dorsal root ganglia just outside spinal cord
  • dendrites and dendron on one end, cell body in middle on a stalk, axon and axon terminals on other end
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4
Q

relay/intermediate neurone

A
  • cell body in brain or spinal cord and connects with sensory and motor neurones
  • cell body in the middle surrounded by dendrites with axon shown as more defined part
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5
Q

schwann cells

A
  • wrap their cell membranes around the axon resulting in layers of fatty substance called myelin
  • the protein P0 locks the schwann cell together - mutations of the gene coding for this protein results in neuropathies
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6
Q

nodes of ranvier

A
  • gaps in myelin - 1-3mm
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7
Q

differences between myelinated and non-myelinated neurones

A

Myelineated;
- diamter 1-25 micrometers
- speed 6-120ms-1
- in 1/3 of sensory and motor neurones
Non-myelinated
- diameter <1 micrometer
- speed 0.2-0.5ms-1
- tend to be in CNS and neurones over short distances

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8
Q

nerve

A
  • bundle of neurones surrounded by perineurium
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9
Q

how does the myelin sheath allow signals to travel faster down a neurone?

A
  • myelin does not conduct electricity well so it prevents the loss of electrical signal from an action potential
  • myelin also isolates axons from one another in the white matter of the brain preventing the short-circuiting of signals in the central nervous system
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10
Q

sensory receptors

A
  • external or internal
  • detect changes in our surroundings (stimuli) and produce an electrical discharge by converting energy into electro-chemical signals (they’re transducers)
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11
Q

what is the information pathway of an impulse?

A
  • receptor, sensory neurones, relay neurones, spinal cord/brain, motor neurone, effector
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12
Q

what determines the strength of an electrical signal?

A

the frequency of impulses produced by the receptor

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13
Q

mechanoreceptor

A
  • pressure/movement
  • eg. parcinian corpuscle in skin
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14
Q

chemoreceptor

A
  • detects chemicals
  • eg. in nose
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15
Q

thermopreceptor

A
  • detects heat
  • eg. on tongue
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16
Q

photoreceptor

A
  • detects light
  • eg. cones in eye
17
Q

transducer

A

a device that converts one form of energy to another

18
Q

how does the parcinian corpuscle produce an electrical signal?

A
  • they are mechanoreceptors that detect pressure and movement
  • when pressure is applied, the lamellae will bend or stretch causing sodium ion channels to open in the axon membrane
  • sodium ions rush through the channel, if enough sodium ions make it through the channel it reaches the threshold and creates an action potential
19
Q

action potential - resting state

A
  • 3 Na+ ions being pumped out the axon for every 2 K+ ions pumped in
  • inside of axon negatively charged at -70mV
  • Na+ ion channels closed
  • K+ ion channels open
  • voltage gated channels only open when a certain voltage is reached
20
Q

action potential - depolarisation

A
  • some Na+ ion channels open and there is rapid influx of sodium ions down electro-chemical gradient
  • inside of cell becomes less negative
  • the change in charge causes more voltage gated Na+ ion channels to open and more sodium ions diffuse in - this is positive feedback
21
Q

action potential - repolarisation

A
  • when the potential difference reaches around +40mV, voltage gated sodium ion channels close and voltage gated potassium channels open
  • potassium ions move out of the cell restoring the negative charge but the position of the ions is reversed
  • so many K+ ions leave the axon that the potential difference becomes even more negative than the resting potential briefly - hyperpolarisation
22
Q

action potential - refractory period

A
  • sodium and potassium ion channels close
  • sodium potassium ion pump was always working but the action can be seen
  • resting potential restored as Na+ ions return to outside and K+ ions to the inside of the neurone
  • this area of the membrane is now able to generate another action potential
23
Q

how to action potentials travel across a neurone?

A
  • an action potential at one point in an axon membrane generates another action potential in the next part of the membrane as voltage gated sodium ion channels further along the channel open due to changes in charge
  • temporary depolarisation of the membrane causes a ‘local circuit’ to be set up and voltage-gated Na+ ion channels open
  • due to the refractory period, the action potential flows one way
24
Q

where on a neurone can action potentials occur?

A
  • at nodes of ranvier - they jump from node to node speeding up conduction by up to 50 times
25
Q

saltatory conduction

A
  • myelination prevents action potentials so they only occur at nodes of Ranvier
  • longer local circuits are generated where there’s myelin which meaning the action potentials almost jump from node to node
  • this speeds up conduction by up to 50 times
26
Q

synapse

A
  • when neurones meet but do not join
  • made up of the ends of neurones and the gap between them - around 20nm
  • eg. neuromuscular junctions - where motor neurone end plate meets muscle fibres causing contraction
27
Q

how does an impulse travel across a synapse?

A
  • action potential arrives
  • Ca+ channels open and they move in to activate cytoskeleton to move vesicles
  • vesicles containign neurotransmitter move to presynaptic membrane
  • vesicles fuse with membrane and release neurotransmitter into synaptic cleft
  • neurotransmitter diffuses across synaptic cleft to post-synaptic membrane and binds with receptors
  • Na+ channels open - membrane is depolarised an action potential produced

Biology (13 decks)

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