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Biology > Neuronal communication > Flashcards

Neuronal communication Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the 3 types of neurons called?

A

Sensory, motor and relay neurons

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2
Q

What is the nervous system made up of?

A

A complex network of cells called neurones

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3
Q

What is the role of sensory neurons?

A

To transmit nerve impulses from receptors to the centeral nervous system (CNS)- the brain and spinal cord

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4
Q

What is the role of motor neurons?

A

Transmit nerve impulses from the CNS to effectors.

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5
Q

What is the role of relay neurons?

A

Transmit nerve impulses between sensory neurones and motor neurones.

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6
Q

What is a stimulus detected by and then what happens?

A

Detected by receptor cells and a nerve impulse is sent along a sensory neurone.

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7
Q

What happens when a nerve impulse (action potential) reaches the end of a neurone?

A

Chemicals called neurotransmitters take the information across to the next neurone, which then sends a nerve impulse.

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8
Q

What does the CNS do?

A

Processes information, decides what to do about it and sends impulses along motor neurones to an effector.

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9
Q

What is the process of the nervous system, starting from the stimulus of seeing a friend waving?

A

Receptors- light receptors (photoreceptors) in your eyes detect the wave.
(Action potential sent along sensory neurone)
CNS- CNS processes information and decides what to do about it.
(Action potential sent along motor neurone)
Effectors- Muscle cells are stimulated by motor neurones
Response- Muscles contract to make your arm wave.

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10
Q

What is the role of sensory receptors?

A

They are transducers- they convert a stimulus energy into a nerve impulse

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11
Q

What is a mechanoreceptor?

A

A type of sensory receptor for pressure and movement stimuli.

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12
Q

What is an example of a mechanoreceptor?

A

A Pacinian corpuscle

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13
Q

Where are pressure receptors located?

A

Deep in skin, mainly in fingers and feet

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14
Q

What does the sensory neurone in the Pacinian corpuscle have?

A

Has special channel proteins in its plasma membrane

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15
Q

What do the membrane of the Pacinian corpuscle have? And what does this allow?

A

Have stretch-mediated channels.
These open and allow NA+ (sodium ion) to enter the sensory neurone only when they are stretched and deformed.

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16
Q

What happens when pressure is applied to the Pacinian corpuscle?

A

It deforms the neurone plasma membrane, stretches and widens the NA+ (sodium ion) channels and so NA+ diffuses in which leads to the establishment of a generator potential.

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17
Q

What happens when a neuron is not conducting an impulse?

A

There is a differnece between the electrical charge inside and outside the cell, this is known as the resting potential.

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18
Q

What is the resting potential voltage and why?

A

-70mV
Because there are more positive ions, Na+ and K+, outside compared to inside, therefore the inside of the neurone is comparatively more negative.

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19
Q

What is the resting potential maintained by?

A
  • Maintained by a sodium-potassium pump, involving active transport and ATP.
  • The pump moves 2 K+ ions in and 3 NA+ ions out of the axon.
  • This creates an electrochemical gradient causing K+ to diffuse out and NA+ to diffuse into the axon.
  • The membrane is more permable to K+ ions and so more are moved out of the axon, resulting in the -70mV.
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20
Q

Why is the axon membrane more permable to potassium ions than sodium ions?

A
  • Because many of the potassium ion channels are permanently open, whereas the sodium ions channels aren’t always open.
  • And because there are more potassium ion channels embedded in the membrane.
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21
Q

What is an action potential?

A

When a neurone’s voltage increases beyond a set threshold.

22
Q

What is an increase in voltage known as and why?

A

Depolarisation becasue the membrane becomes more permable to NA+ (sodium ions).

23
Q

What does a stimulus trigger (in the graph)?

A

Sodium ion channels to open in the membrane allowing sodium ions to diffuse into the neurone down an electrochemical gradient.

24
Q

What happens if a large enough stimulus is detected by the neurone?

A

The resting potential can be converted into an action potential
- The potential difference must reach a threshold of around -55mV to trigger depolarisation.

25
Q

What happens when depolarisation occurs?

A

Voltage-gated sodium ion channels in the axon membrane open
- More sodium ions diffuse into the axon down the electrochemical gradient
This is an example of positive feedback.

26
Q

What potential difference across the membrane will an action potential reach (i.e. depolarisation)?

A

+30 mV

27
Q

What happens very shortly after the potential difference has reached +30mV and what is this called?

A

Repolarisation
- The sodium ion voltage-gated channel proteins close.
- Potassium ion voltage-gated channel proteins open, allowing the diffusion of potassium ions out of the axon, down their concentration gradient.
- This returns the potential difference to normal -70mV.
Example of negtaive feedback.

28
Q

What is hyperpolarisation?

A

Because potassium ion channels are slow to close, which results in too many potassium ions diffusing out causing a short period of hyperpolarisation.
- This means that the potential difference becomes more negtaive than the normal resting potential.

29
Q

What happens after an action potential?

A

After an action potential, the neurone cell membrane can’t be excited again straight away. This is because the ion channels are recovering.

30
Q

What is the all-or-nothing principle?

A

The idea that if the threshold is not reached (-55mV), an action potential won’t fire.

31
Q

What is myelin sheath formed from?

A

Schwann cells

32
Q

What can’t happen in myelinated neurones?

A

In sections of the axon that are surrounded by myelin sheath, depolarisation cannot occur, as the myelin sheath stops the diffusion of sodium ions.

33
Q

Where can depolarisation happen in myelinated neurones?

A

Depolarisation (action potentials) can only occur at the nodes of Ranvier.

34
Q

What is saltatory conduction?

A

When the presence of Schwann cells means the action potentials ‘jump’ from one node to the next.

35
Q

What does saltatory conduction allow?

A

Allows the impulse to travel much faster (up to 50 times faster) than in an unmyelinated axon in the same diameter.

36
Q

What factors affect the speed of conduction along a neurone?

A

Myelinated
The diameter of the axon
Temperature

37
Q

How does the diameter of the axon affect the speed of conduction?

A

An impulse will be conducted at a higher speed along neurones with thicker axons comapred to those with thinner axons.

38
Q

Why do thicker axons conduct impulses at a higher speed?

A
  • Thicker axons have an axon membrane with greater SA over which diffusion of ions can occur
    -> This increases rate of diffusion of sodium and potassium ions through protein channels, which in turn increases the rate at which depolarisation and action potentials can occur.
39
Q

What is a synapse?

A

The junction where two neurones meet is known as a synapse.

40
Q

What are cholinergic synapses?

A

Synapses that use acetylcholine (ACh) as a neurotransmitter.

41
Q

What happens when an electrical impulse arrives at the end of axon on the presynaptic neurone?

A
  • Vesicles move towards, and fuse with, the presynaptic membrane.
  • Chemical messengers called neurotransmitters are released from vesicles at the presynaptic membrane.
  • The neurotransmitters diffuse across the synaptic cleft and temporarily bind with receptor molecules on the post-synaptic membrane.
  • This triggers an impulse which travels along the postsynaptic neurone.
42
Q

What happens to the neurotransmitters after they have temporarily binded with the receptors on the post-synaptic neurone?

A

The neurotransmitters are either destroyed or recycled to prevent continued stimulation of the second neurone, which could cause repeated impulses to be sent.

43
Q

What stimulated the ACh-containing vesicles to fuse with the presynaptic membrane?

A
  • The arrival of the action potential which causes depolarisation of the membrane.
  • Which stimulates the voltage-gated calcium ion channel proteins to open.
  • Calcium ions diffuse down an electrochemical gradient from the tissue fluid surrounding the synapse into the synaptic knob.
    Which stimulates the vesicles to fuse with the presynaptic membrane.
44
Q

What type of receptors does ACh temporarily bind with?

A

Cholinergic receptors

45
Q

What is the process by which ACh diffuses across the synaptic membrane?

A

Exocytosis

46
Q

What happens when the ACh binds to the cholinergic receptors?

A
  • Sodium channels open in the postsynaptic membrane
  • Sodium ions diffuse down the electrochemical gradient into the cytoplasm causing depolarisation of the postsynaptic membrane, restarting the electrical impulse once the threshold is reached.
47
Q

How do synapses ensure the one-way transmission of impulses?

A

Because the neurotransmitters is released on one side and its receptors are on the other side-chemical transmission cannot occur in the opposite direction.

48
Q

What can excitatory neurotransmitters do?

A

Stimulate the generation of an action potential in a postsynaptic neurone.
- This is done by opening the sodium ion channels in the post-synaptic membrane which causes depolarisation if a threshold is reached.

49
Q

What can inhibitory neurotransmitters do?

A

Can prevent the generation of an action potential in the post-synaptic neurone
- They do this by opening the potassium ion channels in the post-synaptic membrane which causes hyperpolarisation of the membrane.

50
Q

What is the threshold

A

-55 mV

Biology (20 decks)

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