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Flashcards in Nerve cells and nerve impulses Deck (33)
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1

What is the nervous system?

The communication network and control centre of the body. Maintains a constant environment inside the body

2

What are neurons?

the basic structural and functional units of the nervous system

3

What is the myelin sheath

a layer of fatty material (in the CNS), cover the Schwann cells

4

Node of ranvier

gaps in the myelin sheath

5

Axon

carried nerve impulses away from the cell body

6

What are the functional types of neurons?

Afferent
Efferent
Interneurons

7

Afferent (sensory neurons)

carry messages from receptors in the sense organs, or in the skin, to the central nervous system

8

Efferent (motor neurons)

carry messages from the central nervous system to the muscles and glands (the effectors)

9

Inter-neurons (association or connector neurons)

- located in the central nervous system
- They are the link between the sensory and motor neurons

10

What are the structural types of neurons?

Multi-polar
Bipolar
Unipolar

11

Multipolar neurons

- Have one axon and multiple dendrites extending from the cell body
- The most common type
- Includes most of the interneurons in the brain and spinal cord and also the motor neurons

12

Bipolar neurons

- Have one axon and one dendrite
- Occur in the eye, ear and nose, where they take impulses from the receptor cells to other neurons

13

Unipolar neurons

- Have just one extension, an axon
- The cell body is to one side of the neuron
- Most sensory neurons

14

What is a neuron

A nerve cell

15

What is a nerve fibre

Any long extension of cytoplasm of a nerve cell body, although the term usually refers to an axon

16

What is a nerve

A bundle of nerve fibres held together by connective tissue

17

What is a synapse?

- The junction between the branches of adjacent neurons
- Usually occur between the axon of one neuron and a dendrite or cell body of another neuron

18

What is a nerve impulse?

- An electrochemical change that travels along a nerve fibre
- Is due to the changes in the concentration of ions inside and outside the cell membrane

19

Nerve impulses in un-myelinated fibres

Travel steady along the fibre

20

Nerve impulses in myelinated fibres

Impulse jumps from one node of Ranvier to the next. Known as salutatory conduction and allows the impulse to travel a lot faster

21

What is salutatory

when the impulse jumps form one node of Ranvier to the next

22

What does extracellular fluid contain?

A high concentration of sodium ions

23

What does intracellular fluid contain?

A high concentration of potassium ions

24

Why does the inside have a relatively negative charge?

Because there are less potassium ions than sodium ions

25

What is the membrane potential?

The potential difference in sodium and potassium ions

26

What is the resting membrane potential?

- The membrane potential of an unstimulated nerve cell
- Can be measured and is about -70mV
- This means that the potential of the inside is 70mV less than the outside
- The neuron is said to be polarised

27

What is the sub-threshold level?

the strength of an impulse needed for the cell membrane to become permeable to sodium ions (opening of the voltage gated sodium channels). Is usually about 15mV

28

What causes depolarisation

The opening of the sodium gates causing the Na+ to move into the cell

29

What causes the neuron to be repolarised?

Tthe closing of the sodium channels and the opening of the potassium channels

30

What is the role of the sodium potassium pump?

To return the membrane to its original state