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a level biology > Nervous Coordination > Flashcards

Nervous Coordination Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are nerve cells?

A

Specialised cells also called neurones, adapted to rapidly carry electrochemical changes (nerve impulses), among largest (longest) cells in the body

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2
Q

What are nodes of ranvier?

A

Gaps where there is no myelination, increase speed

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3
Q

What is the myelin sheath?

A

Multiple cells wrapped around the axon, increases speed of impulse, membrane around Schwann cells

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4
Q

What are dendrites?

A

Extensions of the cell body, carry impulses towards the cell body

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5
Q

What is the axon?

A

A single, long fibre, collect and carry the impulse away from the cell body

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6
Q

What is the cell body?

A

Contains the nucleus and large amount of RER, produce a lot of proteins, particularly neurotransmitters

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7
Q

What are Schwann cells?

A

Individual cells, protect the neurone, provide electrical insulation

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8
Q

What are dendrons?

A

Extensions of cell body, thickest parts of the branches subdivided into dendrites

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9
Q

What is a nerve impulse?

A

A self propagating wave of electrical disturbance that travels along the surface of the axon membrane, a temporary reversal of the electrical potential difference across the axon membrane, not in the neurone, not an electrical current

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10
Q

What are the two states of a nerve impulse?

A

Action potential and resting potential

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11
Q

What is a resting potential?

A

Opposite charges, negative inside, positive outside, maintained by the sodium potassium pump, potential difference of -65mV across the membrane, membrane is polarised

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12
Q

How is a resting potential established?

A

Sodium potassium pump actively transports 3 Na+ out of the axon and 2 K+ into the axon. Sodium ions cannot diffuse down their concentration gradient as sodium gated channels are closed, but potassium ions can diffuse out as their channels are open, inside becomes negative compared to outside

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13
Q

What are ions?

A

Chemicals that carry electrical charge

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14
Q

What is an action potential?

A

Temporary reversal of charge, reversal is propagated called depolarisation, potential difference of +40mV

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15
Q

What is depolarisation (generation of an action potential)?

A

1) Stimulation of a neurone causes some sodium channels to open, allowing sodium to diffuse in, creating a small change in potential difference
2) If the potential difference reaches threshold level, voltage gated sodium channels open causing an influx of sodium ions
3) This causes the inside of the neurone to become more positively charged than the outside, this acts as a stimulus for the adjacent voltage gates channels to open

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16
Q

What is repolarisation (generation of an action potential)?

A

1) When the membrane potential reaches +40mV the sodium ion channels close and the potassium open
2) Sodium ions are unable to diffuse in and K+ diffuses out, causing repolarisation as the inside becomes more negative than the outside, however, ion concentration is different as sodium is higher inside and potassium is higher outside

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17
Q

What is hyperpolarisation?

A

1) Outward diffusion of potassium causes membrane potential to become more negative that at rest
2) potassium gated ion channels close
3) sodium potassium pump restored resting potential

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18
Q

What are voltage gated ion channels?

A

Channels in the membrane, the tertiary structure changes based on voltage to open or close

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19
Q

What factors effect the speed of an impulse?

A

Myelination (saltatory conduction), temperature, and diameter of the axon

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20
Q

How does myelination/saltatory conduction affect the speed of an impulse?

A

Myelin sheath is an electrical insulator and prevents action potentials from forming - they can only occur in the nodes of Ranvier - results in node hopping or saltatory conduction (action potential propagation along myelinated axons between nodes of Ranvier, energy not lost, each action potential is the same size)

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21
Q

How does temperature affect the speed on an impulse?

A

Higher temperature equals more kinetic energy, ions moving faster, too hot and protein channels denature, lower temperature equals less diffusion, so it takes longer for reversal of charge/threshold less likely to be met, decrease in enzyme action, less respiration to make energy for the sodium-potassium pump

22
Q

How does the diameter of an axon affect the speed of an impulse?

A

Larger= lower concentration of ions, smaller= ions can’t fit and leak out, threshold not met, harder to establish an electro chemical gradient, no voltage change to +40mV as harder to build up ions in the axon

23
Q

What is the refractory period?

A

The portion of the graph that leads back to the resting potential from hyperpolarised, unless resting potential is established, another action potential cannot be initiated “the time it takes for Na+ influx to be possible again”

24
Q

What does the refractory period ensure action potentials are?

A

In one direction, discrete, of a limited number at one time

25
Q

Why does the refractory period ensure action potentials are in one direction?

A

The area before the action potential will be in the refractory period, a new action potential cannot occur (wrong voltage), axon must be at rest, therefore it travels in the correct direction, to the brain/effector/next neurone

26
Q

Why does the refractory period ensure action potentials are discrete?

A

Area behind = action potential cannot occur, refractory period takes time, message sent to the brain discrete i.e. not muddled

27
Q

Why does the refractory period ensure action potentials are of a limited number at one time?

A

APs fixed distance apart, cannot occur behind each other, axon is a fixed length therefore only a certain number of action potentials will fit, clear message stops the brain from getting over complicated, and can respond to different intensities of stimulus for different responses

28
Q

What are neurotransmitters?

A

Chemical messages, specific, enable synaptic transmission, the response will depend on the cell, the cells location and the neuron

29
Q

What is the synapse?

A

The point where a neurone communicates with the dendrite of another or with an effector

30
Q

What is a cholinergic synapse?

A

A synapse that relies on the neurotransmitter acetylcholine made of acetyl (ethanol) and choline

31
Q

What is synaptic transmission?

A

Depolarisation of presynaptic neurone causes calcium gates channels to open

32
Q

Describe the process of synaptic transmission

A

an action potential arrives at the presynaptic neurone, stimulates voltage gated calcium ion channels to open in presynaptic knob, calcium ions diffuse in. Influx of calcium ions causes vesicles to move to the presynaptic membrane and fuse with the membrane, they release the neurotransmitter acetylcholine which diffuses across the synaptic cleft to bind to the neuroreceptors on the postsynaptic membrane, this changes the tertiary structure so sodium gated ion channels open and there is an influx of sodium ions, causing depolarisation, if threshold is met, an action potential is established,

33
Q

what happens after synaptic transmission?

A

acetylcholine is removed from the synaptic cleft so the response doesn’t keep happening, it is broken down (hydrolysed) by the enzyme acetylcholine sterase, after hydrolysis acetyl and choline diffuse back across the cleft to the presynaptic neurone, so neurotransmitters can be recycled and repackaged

34
Q

what are chemical synapses?

A

transmit impulses in one direction, to a precise location, prevent overstimulation (limit neurotransmitters, limit neuroreceptors, less sodium diffuses in) act as junctions between allowing a single impulse to multiple neurones, multiple presynaptic neurone impulses can be combined at a synapse

35
Q

what is summation?

A

the additive effect of low frequency action potentials to produce sufficient neurotransmitters to trigger an action potential across the synapse, two forms; spacial and temporal

36
Q

what is an inhibitory synapse?

A

a synapse in which the nerve impulse in a presynaptic cell results in a reduced likelihood of an action potential initiation at the post synaptic cell, neurotransmitters diffuse across, chloride channels in post synaptic membrane open Cl- (ions) diffuses across postsynaptic membrane, membrane becomes hyperpolarised at resting so action potential cannot be generated

37
Q

how do some drugs work by creating fewer action potentials?

A

they inhibit the release of the neurotransmitter, block sodium/potassium ion channels

38
Q

what is an example of a drug that works by creating fewer action potentials?

A

GABA - inhibits/slows brains function, promotes sleepiness

39
Q

how do some drugs work by stimulating the nervous system to create more action potentials?

A

they mimic the neurotransmitter, stimulate the release of neurotransmitter or inhibit the breakdown of neurotransmitter

40
Q

what is an example of a drug that works by stimulating the nervous system to create more action potentials?

A

serotonin - believed to help regulate mood, social behaviour, digestion, sleep, memory, sexual desire/function

41
Q

what are the key structural features of a basic nerve cell?

A

cell body, cytoplasm, nucleus, axon, nodes of ranvier, schwann cells, myelin sheath, dendrites, axon terminal

42
Q

how are motor neurones adapted to their function?

A

lots of dendrites to gather a lot of information for the muscle, the nerve endings are in muscle cells

43
Q

what are the key features of a sensory neurone?

A

axon either side of the cell body, dendrites all away from the cell body, a lot of dendrites for different responses, nerve endings in tissue/receptor

44
Q

what are the key features of an intermediate neurone?

A

short axon as the impulse has to travel a shorter distance/ just connecting nerves together, lot of dendrites to collect nerve impulses

45
Q

how are action potentials propagated in an unmyelinated neurone?

A

membrane at rest maintained by sodium potassium pump (-65mV), sodium gated channels open influx of sodium ions, voltage gated ion channels open, reversal of charge, acts as a stimulus opening sodium gated ion channels to open directly next to them, depolarisation in the adjoining region, behind, sodium gated channels close and potassium open, removal of potassium restores resting potential

46
Q

describe the process of saltatory conduction

A

1) sodium diffuses into axon down electrochemical gradient
2) reversal of charges, action potential occurs
3) sodium ions diffuse along outside of axon from high to low with con gradient
4) voltage gated channels open further along axon
5) Na+ diffuse in
6) new action potential occurs
7) AP moves along axon

47
Q

what are the key structural features of the synapse?

A

presynaptic neurone, synaptic knob, synaptic cleft, post synaptic neurone, SER/RER, calcium ion channels, mitochondria, vesicles, neurotransmitters

48
Q

why does the synaptic knob need SER/RER?

A

synthesise chemical messengers (neurotransmittters)

49
Q

why does the synaptic knob need mitochondria?

A

release energy for movement of vesicles towards synaptic cleft, release energy for protein synthesis

50
Q

why does the synaptic knob need vesicles?

A

package up neurotransmitters, move neurotransmitters to membrane

51
Q

what is temporal summation?

A

single presynaptic neuron release many neurotransmitters many times over a short period to exceed threshold

52
Q

what is spatial summation?

A

different presynaptic neurones come together to trigger one action potential, all presynaptic neurones must release neurotransmitters at the same time for an additive effect to generate an action potential at the post synaptic neurone, in order to meet threshold value

a level biology (21 decks)

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