Basic Plan of the Nervous System

Question 1

What are the main functions of the NS?

Answer 1

sensory input
integration
motor output

Question 2

How is the NS structured?

Answer 2

CNS - brain and spinal cord

PNS - sensory - efferent, motor - afferent

Question 3

How is the motor section of the PNS split up?

Answer 3

somatic - voluntary

autonomic - involuntary

Question 4

How is the autonomic section of the PNS split up?

Answer 4

sympathetic - ‘fight or flight’ response, ACh and Epinephrine
parasymapthetic - the house keeping and homeostasis, ACh

Question 5

What are some of the regions of the brain?

Answer 5

cerebral hemispheres
diencephalon (thalamus) - relay station for sensory impulses
brain stem
cerebellum

Question 6

What are some specialised regions of the cerebrum?

Answer 6

motor, sensory, visual, gustatory, olfactory, auditory

Question 7

What kinds of glial cells might you find in the CNS and PNS?

Answer 7

CNS - ogliodendricytes(myelin sheaths)
astrocytes (absorb K+, NT and form blood-brain barrier),
microglia (clear debris, are scavengers),
ependymal cells (source of stem cells, barrier between compartments)
PNS - schwann cells (myelin sheaths),
satellite cells

Question 8

What is significant about neuroglia?

Answer 8

they outnumber neurones by 5-10 fold and divide, they are the formation of most brain tumours

Question 9

What is the function of astrocytes?

Answer 9

form a barrier between capillaries and neurones and control the chemical environment i.e. removing excess K+ and neurotransmitter, remove excess glutamate and convert it to glutamine to be re-used

Question 10

What are the NS support cells and their features?

Answer 10

microglia(CNS) - spider like phagocytes disposing of debris
ependymal cells (CNS) - lines brain cavities, have cilia, aid circulation of cerebrospinal fluid
oligodendrocytes (CNS) - produce myelin sheath
Satellite cells (PNS) - protect the cell bodies
Schwann cells (PNS) - produce myelin sheath

Question 11

What is special about the myelin sheath produced by schwann cells?

Answer 11

It is formed in a jelly roll form with nodes of ranvier to increase signal transduction. K+ and Na+ channels are concentrated here and this is where APs are regenerated

Question 12

How does MS affect the nervous system?

Answer 12

it causes demyelination in the CNS targeting myelin or oligodendrocytes slowing or stopping signal transduction

Question 13

How does Landry-Guillain-Barre syndrome affect the nervous system?

Answer 13

the most common PNS demyelinating disease causing segmental demyelination due to lymphatic infiltration of schwann cells

Question 14

What can happen in demyelinating diseases where two neurones are close together?

Answer 14

cross talk between neurones can occur causing ectopically generated APs

Question 15

Where is the trigger zone for APs in the neurone?

Answer 15

in the axon hillock

Question 16

Where is the movement of APs in a neurone?

Answer 16

dendrites -> cell body -> axon hillock -> axon

Question 17

What is the evidence for neurotransmission?

Answer 17

When two frog hearts are placed in solution and one is stimulated by the vagus nerve, transfer of that heart’s solution to the other heart, will stimulate the beating of that heart. the same effect is observed when using the vagus nerve on its own.

Question 18

What is the typical movement of ions during neurotransmission?

Answer 18

Na+, Ca2+ inwards - causing depolarisaton

K+ outwards, Cl- inwards causing hyperpolarisation

Question 19

What is the basis of neurotransmission?

Answer 19

depolarisation in neurones leads to transmitter release so neurones regulate the timing and location of transmitter discharge by invoking mechanisms of excitation and inhibition

Question 20

What are some possible drug actions on neurotransmission?

Answer 20

agonists - i.e. Na+ agonist -> opens Na+ channel -> excitation
antagonists - i.e. Na+ antagonist -> closes channel -> inhibition such as local anaesthetics

Question 21

What is the order of movement of ions during an AP?

Answer 21

All or nothing
Na+ comes into the cell generating the AP and depolarising the membrane
K+ goes out of the cell depolarising the membrane
The Na/K pump restores the configuration using ATP

Question 22

How might neurotransmitter be removed from the synaptic cleft?

Answer 22

returned to the axon terminals or into glial cells - astrocytes
enzymes inactivate them - cholinesterases
diffuse out of the synaptic cleft

Question 23

Give some examples of classes of neurotransmitters

Answer 23

amino acids - glutamic acid, glycine, GABA
monoamines - ACh, 5-HT, Serotonin, Histamine
catecholamines - dopamine, noradrenaline, adrenaline

Question 24

How might a neurotransmitter exert its post-synaptic effects?

Answer 24

directly - gating the ionotropic receptors

indirectly - gating the metabotropic receptors

Question 25

What are the two major families of ligand-gated channels?

Answer 25

pentameric - GABA, glycine, ACh

tetrameric - glutamate