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A Level Biology > C3- The nervous system > Flashcards

C3- The nervous system Flashcards

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1
Q

What does the CNS comprise of?

A

The brain and the spinal cord.

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2
Q

What is the name of the tough protective membrane that protects the brain and the spinal cord?

A

The meninges.

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3
Q

Describe the spinal cord.

A
  • The white matter contains nerve fibres surrounded by myelin ( which are fatty so look white).
  • The grey matter has less myelin and is composed mainly of nerve fibres of relay neurones and the cell body’s of relay and motor neurons.
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4
Q

What two nervous systems does is PNS comprised of?

A

The somatic nervous system and the autonomic system.

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5
Q

Describe the somatic nervous system.

A
  • It contains pairs of nerves and their branches that originated in the brain or spinal cord.
  • These nerves contain fibres of sensory neurons that carry impulses to the CNS and motor neurones that carry impulses from the CNS to effectors.
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6
Q

What is the autonomic nervous system?

A

It provides unconscious control of the functions of the internal organs, such as the heartbeat or digestion.

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7
Q

What is a reflex arc?

A

The neutral pathway taken by the nervous impulses of a reflex action.

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8
Q

Define a reflex action.

A
  • A rapid automatic response resulting from nervous impulses initiated by a stimulus.
  • The decision making area of the brain is not involved and this makes the response involuntary.
  • They’re a protective function.
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9
Q

Identify the elements of a reflex arc.

A 
Stimulus 
receptor 
sensory neurones 
relay neurones in the CNS
motor neurone
effector
response
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10
Q

Name a reflex action that does not require a relay neurone.

A

When your knee jerks.

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11
Q

Briefly describe the evolution of the nervous system.

A
  • Animals in the phyla who appear in early fossil records do not have a nervous system. They do have genes related to nerve formation though.
  • Later animals have radial symmetry and their nervous system is a nerve net.
  • Animals that have appeared even later have bilateral symmetry and a central nervous system.
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12
Q

Define a nerve net.

A

The simplest kind of nervous system, a diffuse network of cells that group into ganglia, but do not form a brain.

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13
Q

Name the two types of nerve net.

A
  • Ganglion cells provide connections in several directions.

- Sensory cells detect stimuli.

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14
Q

What are the non-neuronal cells in the human nervous system called?

A

Glia.

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15
Q

What do glia cells do?

A

Protect and support the neurons, including generating the myelin sheath.

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16
Q

What type of nervous system does a hydra have?

A

A nerve net.

17
Q

Why is the hydra used to study nerve nets?

A
  • Has a simple pattern.
  • Easy to manipulate in experiments.
  • Regenerates rapidly e.g. when replacing lost tentacles
18
Q

Where is the hydra’s net located?

A

It is in its ectoderm which is the outer of two layers of cells that make up its body wall.

19
Q

What does they Hydra’s nerve net allow it to do?

A
  • Sense light, physical contact and chemicals.
  • In response it can contract, perform locomotion, hunt and feed.
  • So even without a brain it shows complex movements.
20
Q

What is the limitation of the nerve net found inside a Hydra?

A

It cannot detect the direction of a stimulus, although a larger stimulus can stimulate more cells and so triggers a larger response.

21
Q

How many cell types does the Hydra’s nervous system have?

A

Two.

22
Q

Does the Hydra’s nervous system have a myelin sheath?

A

No.

23
Q

Compare the speed of the hydra’s nervous system to that of a human’s.

A

The human’s nervous systems significantly faster.

24
Q

Can the Hydra’s nervous system regenerate neurones?

A

Yes.

25
Q

What do each of the following neurones do?

  • Sensory
  • Motor
  • Relay/ connector/ association
A
  • Sensory- Carry impulses from the sense receptors or organs into the CNS.
  • Motor- Carry impulses from the CNS to the effector organs (e.g. muscles or glands)
  • Relay- receive impulses from the sensory neurones and transmit them to the motor neurones or other relay neurones.
26
Q

Explain the functions of the following structures of a neurone…

  • Cell body/ centron
  • Cytoplasm
  • Nucleus
A
  • Cell body- Contains the nucleus and granular cytoplasm.
  • Cytoplasm- It is granular and it contains many ribosomes.
  • Nucleus- Holds the DNA.
27
Q

Explain the functions of the following structures of a neurone…

  • Nissl granules
  • Dendrite
  • Axon
A
  • Nissl granules- Cytoplasmic granules comprising of ribosomes grouped on RER.
28
Q

What does the following statement mean?

‘Neurones are excitable.’

A

They can change their resting potential.

29
Q

What is the resting potential?

A

It is -70mV.

It is the potential difference across a neurones membrane.

30
Q

What does an action potential do to the polarity of a nerve cell?

A

It reverses its polarity.

31
Q

Describe the stages on a graph showing the phases of an action potential in relation to the potential difference of the cell.

A

resting potential → depolarisation → depolarisation → undershoot → resting potential

32
Q

What is the fluid that runs through the axon?

A

axoplasm

33
Q

Describe the overall charge inside a neurone at resting potential compared to outside the cell.

A

Inside the cell has an overall negative charge compared to outside the cell that has an overall positive charge.

34
Q

Explain simply how an action potential is created.

A

By positive ions rushing in.

35
Q

Describe the organic ions found in a nerve cell.

A
  • They’re large.
  • They remain within the cell.
  • They are negatively charged amino acids.
36
Q

How does K^+ move out of the cell?

A

Via potassium channels.

37
Q

How does Na^+ move into the cell?

A

Via sodium channels.

38
Q

How does Na^+ move out of the cell?

A
  • Active transport

- Sodium potassium pump

A Level Biology (10 decks)

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