NS 1 - Organisation and basic function

Question 1

3 functional characteristics of the CNS

Answer 1

Spinal cord level
Subcortical level or lower brain
Cortical level or higher brain

Question 2

What are the functions of the neuronal circuits performed by the SC? (4)

Answer 2

• Walking movements.
• Reflexes to withdraw away from pain source.
• Reflexes that support the body against gravity
• Reflexes that control local blood vessels, GIT wall movements
  and urinary excretion.

Question 3

What is the overall function of the lower brain/ subcortical level?

Answer 3

Subconscious control of body function

Question 4

Feeding reflexes (salivation and licking the lips) in response to the taste of food - are
controlled by areas in which structures? (5)

Answer 4

medulla, pons, mesencephalon, amygdala, and
hypothalamus.

Question 5

Emotional responses are controlled by which level of the brain?

Answer 5

Subcortical level/lower brain

Question 6

What structures make up the subcortical level of the brain? (7)

Answer 6

medulla, pons, mesencephalon, hypothalamus, thalamus,
cerebellum, and basal ganglia.

Question 7

Where is arterial pressure and respiration controlled?

Answer 7

In the pons

Question 8

Equilibrium is a combined function of what?

Answer 8

of the cerebellum and the reticular substance of
the medulla, pons, and mesencephalon.

Question 9

What are the functions of the higher brain/cortical level?

Answer 9

Essential for thought processes and cannot function independently.
* Cerebral cortex store memory

Question 10

How many neurons are in the CNS?

Answer 10

▪ CNS contain ~ 80 to 100 billion neurons.

Question 11

Name the major structural features of the neurons

Answer 11

Dendrites, cell body (soma), and axon

Question 12

What is the cytoplasm in n exon called?

Answer 12

Axoplasm

Question 13

What structural proteins are in the axoplasm?

Answer 13

Axoplasm contains dense bundles of microtubules and
neurofilaments.

Question 14

What is the function of the axon transport system?

Answer 14

Axon transport system moves organelles and
macromolecules between the cell body and the axon
terminals.

Question 15

Differentiate between anterograde/orthograde and retrograde

Answer 15

Axonal transport from the cell body toward the terminals is
called anterograde or orthograde.
▪ Axonal transport from the terminals toward the cell body is
called retrograde.

Question 16

What is the clinical significance of anterograde and retrograde transport?

Answer 16

Axonal transport is important in the pathogenesis of
some human neurologic diseases.

Question 17

Explain the rabies virus - site of replication and its use of axonal transport

Answer 17

▪ Rabies virus replicates in muscle tissue at the site of a
bite by a rabid animal and is then transported in a
retrograde direction to the cell bodies of neurons
innervating the muscle.

Question 18

________________is also transported in a retrograde direction in nerve cells whose axons
terminate at the site of infection.

Answer 18

Bacterium Clostridium tetani

Question 19

Virus in mucocutaneous nerve endings uses _________________ transport to reach ____________________ and becomes latent

Answer 19

retrograde
dorsal root ganglion

Question 20

A reactivated virus travels from where to where? Using what transport?

Answer 20

Reactivated virus within the dorsal root
ganglion to become infectious followed by
passage of virus down (anterograde) the axon
to mucocutaneous site.

Question 21

List the 3 types of glial cells

Answer 21

Astrocytes
* Oligodendrocytes (Schwann cells)
* Microglial cells.

Question 22

What are the functions of glial cells? (4)

Answer 22

Glial cells control the CNS environment within which neurons function.

Shuttle nutritive molecules from blood vessels to neurons.

• Removal of waste products
• Maintaining the electrochemical surroundings of neurons.

Question 23

Function of the oligodendrocytes

Answer 23

Function of oligodendrocytes is myelination

Question 24

What is myelin sheath and what is its function?

Answer 24

Myelin sheath is an electrochemical insulator around
axons in the white matter.
▪ Myelin sheath around an axon greatly increases the
speed of conduction of action potentials along the
axon.

Question 25

What happens in demyelinating diseases?

Answer 25

Degeneration of oligodendrocytes and their myelin segments Myelin sheath is an electrochemically insulator around axons in the white matter. Loss of myelin results in slower action potential propagation along demyelinated axons.

Question 26

Degeneration of the distal axon is called_____________

Answer 26

denervation

Question 27

Degeneration of the distal axon (denervation) and myelin sheath results in____________________

Answer 27

atrophy of denervated myofibers (muscle fibres)

Question 28

What does demyelination result in?

Answer 28

Demyelinating results in random segmental degeneration of individual myelin internodes

Question 29

What is a synapse?

Answer 29

▪A Synapse is the junction point at which an electrical response in one cell is transmitted to another cell. ▪Synapses determine electrical impulse spread through the nervous system

Question 30

List the 3 types of synapses

Answer 30

Axodendritic Axoaxonal Axosomatic

Question 32

Define presynaptic facilitation

Answer 32

Neuron exerting powerful excitatory effect on synaptic contact with the axon terminal

Question 33

Define presynaptic inhibition

Answer 33

Neuron exerting powerful inhibitory effect on synaptic contact with the axon terminal

Question 34

Repeated use of a synapse can lead to?

Answer 34

Increase in the quantity of transmitter released (long term potentiation(LTP) - synaptic plasticity Decrease in transmitter release (Long term depression (LTD))

Question 35

What is the importance of LTP and LTD

Answer 35

Learning and memory storage

Question 36

What are IPSP and EPSP

Answer 36

EPSP- excitatory post-synaptic potential IPSP - inhibitory post-synaptic potential They are graded potentials that only influence the local membrane and then rapidly decay.

Question 37

Explain resting state of neuron in synaptic integration

Answer 37

Motor nerve cell shown with synaptic boutons of excitatory and inhibitory nerve fibers ending close to it

Question 37

Explain partial depolarisation

Answer 37

Impulse from 1 excitatory fiber has caused partial (below threshold) depolarisation of a motor neuron

Question 38

Explain temporal excitatory summation

Answer 38

A series of impulses in one excitatory fiber together produce a suprathreshold depolarisation that triggers an action potential.

Question 39

Explain spatial excitatory summation

Answer 39

Impulses in 2 excitatory fibers cause 2 synaptic depolarizations that together reach the firing threshold, triggering an action potential