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Human Biology - Unit 3 > Chapter 3 A- Nerve Cells & Nerve Impulses > Flashcards

Chapter 3 A- Nerve Cells & Nerve Impulses Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a neuron?

A

A nerve cell, basic structural and functional units of the nervous system

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2
Q

What do all neurons consist of?

A
  • cell body

- two extensions: axon and dendrites

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3
Q

Neuron: cell body

A
  • contains nucleus, organelles and cytoplasm
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4
Q

Neuron: dendrites

A
  • fairly short extensions of the cytoplasm
  • highly branched
  • carry nerve impulses into the cell body
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5
Q

Neuron: axon

A
  • single, long extension of the cytoplasm
  • length varies greatly, can be very long
  • most covered with layer of fatty material called the myelin sheath
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6
Q

What is a nerve fibre?

A

Term used for any long extension of a neuron, usually refers to an axon

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7
Q

Neuron: myelinated fibre

A
  • axon with myelin sheath
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8
Q

Neuron: unmyelinated fibre

A
  • axon with no myelin sheath
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9
Q

What does grey matter consist of?

A

Cells with unmyelinated fibres

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10
Q

What does white matter consist of?

A

Cells with myelinated fibres

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11
Q

Neuron: Schwann cells

A
  • wrap around myelin sheath

- forms myelin sheath

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12
Q

Neuron: nodes of Ranvier

A
  • gaps in the myelin sheath
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13
Q

Neuron: neurilemma

A
  • outermost coil of the Schwann cell

- helps repair injured fibres

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14
Q

What are the functions of the myelin sheath?

A
  • acts as an insulator
  • protects axons from damage
  • speeds up movement of nerve impulses along axon
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15
Q

What are the three functional types of neurons?

A
  1. sensory (receptor) neurons
  2. Motor (effector) neurons
  3. Inter neurons
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16
Q

What is the function of sensory neurons?

A
  • carry messages from the receptors in the sense organs, or skin, to the central nervous system
17
Q

What is the function of motor neurons?

A
  • carry messages from the central nervous system to muscles and glands - the effectors
18
Q

What is the function of interneurons?

A
  • located in the central nervous system and are the link between sensory and motor neurons
19
Q

What are the structural types of neurons?

A
  1. Multipolar neurons
  2. Bipolar neurons
  3. Unipolar neurons
20
Q

Structure of multipolar neurons:

A
  • have one axon and multiple dendrites extending from the cell body
21
Q

Where are multipolar neurons found?

A
  • most of the interneurons in the CNS

- motor neurons

22
Q

Structure of bipolar neurons:

A
  • one axon and one dendrite

- both axon and dendrite may have many branches

23
Q

Where are bipolar neurons found?

A
  • sensory neurons in the eye, ear and nose, where they take impulses from receptor cells to other neurons
24
Q

Structure of unipolar neurons:

A
  • have just one extension: an axon

- the cell body is to the side of the axon

25
Q

Where are unipolar neurons found?

A
  • sensory neurons that carry impulses to the spinal chord
26
Q

What is a synapse?

A

The junction between the branches of adjacent neurons

27
Q

What is a neuronmuscular junction?

A

The synapse that exists where an axon meets a skeletal muscle cell

28
Q

What is the all-or-none response?

A

A stimulus is either strong enough to trigger an impulse, or it is not. The magnitude of an impulse is always the same.

29
Q

How are we able to distinguish stimuli of different intensities?

A
  • a strong stimulus causes depolarisation of more nerve fibres than a weak stimulus
  • a strong stimulus produces more nerve impulses in a given time than a weak stimulus
30
Q

What ions are found in high concentration inside the membrane?

A
  • K+

- variety of negative ions that come from organic substances made by the cell

31
Q

What ions are found in high concentration outside the membrane?

A
  • Na

- Cl

32
Q

The cell membrane is highly permeable to __________

A
  • K

- Cl

33
Q

The cell membrane is slightly permeable to __________

A
  • Na
34
Q

How does the cell membrane maintain the potential difference?

A
  • actively moves ions across the membrane (sodium-potassium pump)
  • there are a large number of negatively charges ions trapped inside the cell
35
Q

Where are unipolar neurons found?

A

Sensory neurons

36
Q

Where are bipolar neurons found?

A

Sensory neurons in the eye, ear and nose

37
Q

Where are multipolar neurons found?

A

Connector neurons, motor neurons

38
Q

Which way does the nerve impulse travel?

A

Axon to dendrites

Human Biology - Unit 3 (18 decks)

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