L7

Question 1

Anatomical divisions of the nervous system (5):

Answer 1

• The brain
• The spinal cord
• The peripheral nerves
• The autonomic nervous system
• The enteric nervous system (controls activity of the gut)

Question 2

The CNS is made of two main types of cell:

Answer 2

•Nerve cells or neurons :

–different morphological types

–have characteristic thread-like extensions: dendrites at the input end and axon at the output

–Cell bodies found in grey matter of CNS and in autonomic ganglia

•Glial cells or neuroglia

Question 3

Glial cells or neuroglia:

Answer 3

–The support cells of the CNS, and far outnumber neurons (~90% of all cells in the nervous system) – 4 main types:

astroglia,

oligodendrocytes,

microglia,

ependymal cells

(in the PNS Schwann cells and macrophages). Oligodendrocytes and Schwann cells are crucial to neurotransmission

Question 4

Ependymal cells -

Answer 4

line central fluid filled spaces e,g, ventricles of brain

Question 5

Astroglia -

Answer 5

attach to blood vessels

Question 6

Microglia: phagocytic -

Answer 6

converge of site of injury or infection

Question 7

Axons in bundles-fascicles -

Answer 7

anchored to connective tissues by epineurium

Question 8

Each bundle covered by ….

Answer 8

perineurium

Question 9

Phases of an Action Potential (3):

Answer 9

1. Depolarisation
2. Repolarisation
3. Hyperpolarisation

Question 10

Neurons (nerve cells) require a certain minimum depolarization before they will generate an action potential. This is known as the ….

Answer 10

threshold.

Question 11

Przypomnienie refractory period

Answer 11

After an action potential has passed along an axon it cannot conduct another until a certain time has elapsed - axons have a refractory period.

Question 12

Action Potentials are usually initiated at the ….

Answer 12

axon hillock (cell body)

Question 13

fajna strona z AP

Answer 13

http://outreach.mcb.harvard.edu/animations/actionpotential_short.swf

Question 14

Refractory periods contribute to:

Answer 14

All or none property

Frequency of firing i.e. coding of information

Unidirectional propagation along axons but can back propagate in dendrites!

[See Gasparini et al 2007; Hausser et al 2000)]

Question 15

Thus two main mechanisms have emerged to increase speed of conduction:

Answer 15

1. increase the diameter of the nerve (axial resistance ↓ α d^2)
2. myelination (insulation; nodes of Ranvier- saltatory conduction; increased insulation decreases capacitance;)

Question 16

Przypomnienie ciekawostka

Answer 16

A myelin sheath can have up to 300 layers of membrane

Question 17

Saltatory conduction (myelinated nerves):

Answer 17

current can only cross the membrane at the nodes of Ranvier

Question 18

Continuous conduction (neurons without myelin sheath):

Answer 18

current flows from A (active region) to B. Like a fuse!

Question 19

Przypomnienie CAP? slajd 24…

Answer 19

compound action potentials (CAP) The CAP represents the result of stimulation of several axons, hence its change in amplitude with increasing stimulus strength. There is also a refractory period for whole nerve stimulation.

Question 20

‘A’ fibres conduct at …. m/s depending on type. The fastest are …

Answer 20

30-70, sensory afferents

Question 21

‘C’ fibres are the slowest: …. m/s. These are unmyelinated

Answer 21

0.5 -2.0

Question 22

This period of inexcitability is known as the absolute refractory period and lasts for …

Answer 22

1-2 ms.

Question 23

After the absolute refractory period there is a period of reduced excitability called the ….

Answer 23

relative refractory period.

Answer 24