Week 1 - neurons

Question 1

What is the function of neurons?

Answer 1

transmission of information

Question 2

What is the function of glia cells?

Answer 2

• specialised support cells
• provide structural, metabolic and defensive support for nervous tissue

Question 3

Recap of an action potential

Answer 3

stimulus reaches threshold of -55 mV -> depolarisation (Na+ ions in) -> depolarisation (K+ ions out) -> hyperpolarisation -> resting state

Question 4

What is the function of a dendrite?

Answer 4

• sensory (afferent)
• receives information and relay it to the cell body in order to innervate it

Question 5

What form of signals do dendrites relay?

Answer 5

electrical signals

Question 6

What is the function of the cell body (soma)

Answer 6

• large nucleus, abundant rER,
• performs most synthetic and metabolic functions
• integrates information i.e electrical signals, at the axon hillock

Question 7

What is the function of the nucleus?

Answer 7

• same as any other nuclei
• contains chromosomes, needed for DNA transcription
• production fo proteins

Question 8

What is the function of the axon?

Answer 8

• effector portion (efferent) - propagates the action potential
• having a larger diameter and myelination increases conduction velocity
• axon terminals, expansions at the ends of the axon branches, are specialised for chemical neurotransmission

Question 9

How many axons are there?

Answer 9

only one

Question 10

How many dendrites can arise from a neuron?

Answer 10

multiple

Question 11

What is the function of a myelin sheath?

Answer 11

• insulating layer that forms around nerves
• allows electrical impulses to transmit quickly and efficiently along the nerve cells

Question 12

What is a myelin sheath made up of?

Answer 12

protein and fatty substances

Question 13

What happens if myelin is damaged?

Answer 13

impulses slow down

Question 14

What is the function of the nodes of ranvier?

Answer 14

• periodic gasps in the insulating sheath facilitate rapid conduction of nerve impulses - saltatory conduction

Question 15

What are Schwann cell/ oligodendrocytes?

Answer 15

• glial support cells
• serve as myelinating cell of the PNS
• forms a myelin sheath by wrapping its plasma membrane concentrically around the inner axon

Question 16

What is the function of the synapse/ axon terminal

Answer 16

• the site of transmission of electric nerve impulses between two nerve cells (neurons) or between a neuron and a gland or muscle cell (effector)
• involves release of neurotransmitter across the gap
• innervates the dendrite at next neuron
• synapse splits to innervate multiple neurons

Question 17

What happens at a synapse? (1-6)

Answer 17

1. transmitter is synthesised and then stored in vesicles
2. an action potential invades the presynaptic terminal
3. depolarisation of presynaptic terminal causes opening of voltage gated Ca2+ channels
4. influx of Ca2+ through channels
5. Ca2+ causes vesicles to fuse with presynaptic membrane
6. Transmitter is released into synaptic cleft via exocytosis

Question 18

What happens at a synapse? (7-11)

Answer 18

7. transmitter binds to receptor molecules in postsynaptic membrane
8. opening or closing of postsynaptic channels
9. postsynaptic current causes excitatory or inhibitory postsynaptic potential that changes the excitability of the postsynaptic cell
10. removal of neurotransmitter by glial uptake or enzymatic degradation
11. retrieval of vesicular membrane form plasma membrane

Question 19

Are there more neurons or more glial cells?

Answer 19

there are 10 times as many glial cells as neurons

Question 20

Are there different types of glial cells?

Answer 20

yes - different types found in CNS and PNS

Question 21

Name examples of glial cells

Answer 21

• Schwann cells
• oligoendocytes
• astrocytes
• microbial cells
• ependymal cells

Question 22

Compare glial cell in CNS vs PNS

Answer 22

• PNS only contains satellite cells (support) and Schwann cells (myelinate)
• CNS glial cell types include astrocytes, microglial, oligodendrocytes, ependymal cells, stem cells

Question 23

What are the functions of Oligodendrocytes?

Answer 23

1. insulate axons preventing their spontaneous or accidental depolarisation
2. produce myelin by wrapping around axons many times,

Question 24

What does myelination of an axon do?

Answer 24

increases action potential conduction velocity

Question 25

can a single oligodendrocyte insulate multiple axons?

Answer 25

Yes

Question 26

What are ependymal cells and where are they found?

Answer 26

epithelia-like cells lining the ventricles of the brain and spina cord

Question 27

Microglia

Answer 27

act as defensive cells of the CNS, perform the functions of macrophages

Question 28

What are the 7 functions of astrocytes?

Answer 28

• development: form structural framework for migration of neurons eg. radial glia
• regulation of extracellular K+
• roles in neurotransmission eg. uptake of glutamate at synapses
• insulate neuronal cell bodies and dendrites at non-synaptic sites
• form continuous layer over blood vessels, part of the blood- brain- barrier, regulate local microcirculation and vascular permeability
• metabolic energy generation in neurons (transfer of substances form vasculature to neurons, provide lactate into extracellular fluid for neurons)
• form glial scars at sites of damage (gliosis) and have roles in a nr. of pathologies interacting with microglia and neurons