Lecture 4- Nerves

Question 1

What are the valleys and ridges called

Answer 1

Gyri- ridges

Sulci- valleys

Question 2

What are the four regions of the cerebral hemisphere

Answer 2

frontal
parietal
temporal
occipital

Question 3

What are the three sections of the brainstem?

Answer 3

Midbrain
Pons
Medulla

Question 4

What originates from the brain stem?

Answer 4

Cranial nerves

Question 5

What is the role of the cerebellum?

Answer 5

Motor coordination
Balance
Posture

Question 6

What is the role of the spinal cord?

Answer 6

Coordinates reflex actions

For nerve transmission

Question 7

What are the 4 types of neurones and what do they look like?

Answer 7

1) Unipolar: 1 axonal projection
2) Pseudo-unipolar: single axonal projection that divides into two
3) Bipolar: 2 projections
4) Multipolar: Numerous projections

Question 8

Name three types of Multipolar cells

Answer 8

Pyramidal cells
Purkinje cells
Golgi cells

Question 9

Describe the structure of a neurone

Answer 9

1) Soma (cell body): contain nucleus & ribosomes
2) Axon: nerve fibre, from axon hillock on soma, branches into collaterals, covered in myelin
3) Dendrites: highly branched, not myelinated, receive signals

Question 10

What are neurones?

Answer 10

Excitable cells of CNS

Non-dividing

Question 11

What are the functions of astrocytes?

Answer 11

• structural cells
• cell repair
• immune cells (facultative macrophages)
• neurotransmitter release and reuptake)

CAN PROLIFERATE

Question 12

Which two cells produce myelin? What is the difference between them two?

Answer 12

Oligoendrocytes and Schwann cells

1 Oligo–> myelinates many axons
but…
1 Schwann –> myelinates one axon segment and PNS nerves

Question 13

What are microglial cells?

Answer 13

• Similar to macrophages

- perform immune functions in CNS

Question 14

What are Ependymal cells

Answer 14

• Epithelial cells which line fluid filled ventricles

- regulate production and movement of CSF

Question 15

What are the relative concentrations of ions at rest?

Answer 15

High EC- Na+ and Cl-
Low EC- K+
High conc gradient- K+

Question 16

What is the RMP of neuronal cells?

Answer 16

-40mV to -90mV

Question 17

Which two channels are found in neuronal membranes and what are their states at RP?

Answer 17

Voltage gated Na+ channels (VGSCs)
Voltage gated Ca2+ channels (VGCCs)
Both are closed at RP

Question 18

What happens when membranes depolarise?

Answer 18

VGSCs open–> Na+ influx –> further depolarisation

Question 19

What happens when membranes repolarise?

Answer 19

VGKCs open–> efflux of K+ from cell –> membrane repolarisation

Question 20

What is the purpose of the Na+/ K+ ATPase pump after repolarisation?

Answer 20

• After AP, there is an imbalance in Na+ and K+

- the pump restores the ion gradients

Question 21

Explain how the ATPase pump transports K+ and Na+

Answer 21

• Resting configuration- Na+ enters and when channel is phosphorylated ions are transported
• Active configuration- Na+ removed from cell–> K+ enters vestibule
• Returns to Resting configuration- transported back into cell

Question 22

What are the characteristics of myelin which allow saltatory conduction?

Answer 22

• high resistance

- low capacitance (ability to store electrical charge)

Question 23

What is saltatory conduction?

Answer 23

AP jumping between nodes of Ranvier

Question 24

Describe the sequence of events that allow transmission of an AP at a synapse

Answer 24

1) AP arrives at synapse
2) Causes VGCC to open
3) Ca2+ influx
4) Causes vesicles containing neurotransmitters to fuse with the presynaptic membrane
5) Neurotransmitter diffuses across synaptic cleft
6) NT binds with receptors on postsynaptic membrane, AP propagated here
7) Neurotransmitter broken down by synaptic enzymes
8) Reuptake of neurotransmitter by presynaptic knob