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Biology February Mock > Nervous Control > Flashcards

Nervous Control Flashcards

1
Q

What do dendrites do?

A

Carry nerve impulses towards the cell body

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2
Q

What do axons do?

A

Carry neber impulses away from the cell body

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3
Q

Describe the structure and function of sensory neurones

A

One long dendron carries nerve impulses from receptors to the cell body
One short axon carries nerve impulses from cell body to CNS

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4
Q

Describe the structure and function of relay neurones

A

Many short dendrites carry never impulses from sensory neurones to cell body
An axon carries nerve impulses from cell body to motor neuorne

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5
Q

Describe the structure and function of motor neurones

A

Many short dendrites carry nerve impulses from CNS to cell body
One long axon carries nerve impulses from cell body to effector cells

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6
Q

What does it mean that some neurones are myelinated?

A

They contain a myelin sheath which acts as an electrical insulator, made up of Schwann cells

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7
Q

What are the patches of bare membrane in between Schwann cells?

A

Nodes of Ranvier

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8
Q

What the term ‘receptors are specific’ mean?

A

They only detect one particular stimulus

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9
Q

What is a potential difference?

A

Voltage across a membrane that is generate by ion pumpe and ion channels

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10
Q

What controls pupil size?

A

The iris

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11
Q

What happens to pupil in dim light?

A

Radial muscles contract
Circular muscles relax
Pupil dilates

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12
Q

What happens to pupil in bright light?

A

Radial muscles relax
Circular muscles contract
Pupil constricts

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13
Q

What is the figure for resting potential

A

-70 mv

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14
Q

Describe the polarity when a neurone is at rest:

A

The outside of the membrane is positively charge

The inside of the membrane is negatively charged

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15
Q

How is the resting potential maintained?

A

Sodium potassium pumps AND potassium ion channels in the neurone membrane

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16
Q

Describe the sodium potassium pumps

A

Use active transport to pumo 3 sodium ions out of the neurone for every 2 potassium ions pumped in
Requires ATP

17
Q

How is an electrochemical gradient built up?

A
  • Sodium-potassium pumps move sodium ions out of neurone, membrane is not permeable to sodium so they can’t diffuse back into neurone = sodium ion electrochemical gradient
  • Sodium-potassium pumps move potassium into cell but membrane is permable to potassium due to potassium ion channels (facilitated diffusion) so can diffuse back out of neurone
  • outside of cell is positively charged compared to inside
18
Q

Describe the sequence of events in an action potential:

A
  • Stimulation causes membrane to become slightly depolarised due to small influx of socdium ions
  • Threshold value of -55 mv reached
  • Voltage gated sodium channels open, sodium ions diffuse into neurone down its electrochemical gradient = cell becomes depolarised
  • membrane polarity peaks at 40mv
  • potassium channels open slowly so potassiumnions diffuse out of the cell down an electrochemical gradient = repolarisation
  • too much potassium leaves neurone causing hyperpolarisation
  • generates a refractory period
19
Q

How does a nerve impulse travel along the neurone?

A
  • some sodium ions that enter the neurone diffuse sideways

- sodium ion channels open in the next region of the neurone and diffuse in, causing a wave of depolarisation

20
Q

Why is the refractory period useful?

A
  • Ensures action potentials only travel in one direction (hyperpolarisation of previous region means further from threshold value)
  • Ensures a time delay between one action potentil and the next, eo they don’t overlap
21
Q

How do local anaesthetics work?

A
  • Bind to sodium ion channels in the membrane of neurones
  • Stops sodium ions moving into the neurones so the membrane will not depolarise
    Prevents action potentials being conducted and stops info about pain being sent to brain
22
Q

In a myelinated neurone, where does depolarisation occur?

A

Only happens at the nodes of Ranvier

23
Q

What is saltatory conduction?

A

Where a impulse jumps from node to node in a myelinated neurone, making it very fast

24
Q

What is conduction velocity?

A

The speed at which an impulse moves along a neurone

25
Q

What is a synapse?

A

The junction between a neurone and another neurone, or between a neurone and an effector cell eg. muscle or gland cell

26
Q

What is the synaptic cleft?

A

The tiny gap between the two cells

27
Q

What does the presynaptic neurone contain + what is the function?

A

Has a swelling called a presynaptic knob which contains synaptic vesicles filled with neurotransmitters

28
Q

What feauture of synapses ensures that an impulse only travels in one direction?

A

Receptors are only found om the postsymaptic membrane so unidirectional

29
Q

Give an example of a neurotransmitter and what does it control?

A

Acetylcholine controls heart rate and muscle contraction

30
Q

How do neurotrasmitters transmit neeve impulses between neurones? X5

A
  1. AP arrives at synaptic knob which stimulates voltage-gated calcium ion channels in presynaptic neurone to open, calcium ions diffuse into synaptic knob
  2. Influx of calcium vauses synaptic vesicles to move towards and fuse with presynaptic membrane, exocytosing neurotransmitters into synaptic cleft
  3. Neurotransmitter diffuses across synaptic cleft and binds to specific receptors on postsynaptic membrane causing sodium ion channels to open
  4. Influx of sodium ions into postsynaptic membrane causes depolarisation and a AP is generated if threshold value reached
  5. Neurotransmitter is removed from synaptic cleft by enzymes and taken back to presynaptic neurone to be recycled
31
Q

What is synaptic divergence?

A

Where ONE neurone connects to many neurones so info can be dispersed to different parts of body

32
Q

What is synaptic convergence?

A

Where MANY neurones connect to one neurone to amplify the impulse

33
Q

What is summation?

A

Where the effct of neurotransmitters released from many neurones is added together: temporal or spatial

Biology February Mock (9 decks)

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