Nerves

Question 1

Describe the cerebral hemispheres:

Answer 1

4 lobes, with occipital at back and frontal at front (parietal and temporal in middle); highly convoluted surface of ridges (gyri) and valleys (sulci)

Question 2

Describe the brainstem

Answer 2

Consists of midbrain, then pons then medulla; target/source of all cranial nerves and has important functions

Question 3

Describe the cerebellum

Answer 3

Hindbrain attached to brainstem and is important for motor coordination, balance and posture

Question 4

How many axons do neurones have?

Answer 4

ONLY ONE

Question 5

What are the four morphologies of neurones?

Answer 5

Unipolar: One axonal projection
Pseudo-unipolar: Single axonal projection that splits into two
Bipolar: 2 Projections from cell body, 1 axon, one dendrite
Multipolar: Numerous projections from cell body, 1 axon, many dendrites

Question 6

What is a Soma?

Answer 6

Cell Body; contains nucleus and ribosomes. Neurofilaments are important for structure and transport

Question 7

What is an axon?

Answer 7

Long process (nerve fibre)
Starts at axon hillock of soma, can branch off into collaterals; usually myelinated

Question 8

What is a dendrite?

Answer 8

Highly branched and not myelinated - “like trees” coming out of cell body to receive signals from other neurones

Question 9

What is an astrocyte?

Answer 9

Most abundant cell in CNS and able to proliferate; foot processes important to maintain blood-brain barrier

Question 10

What are the 4 main functions of astrocytes?

Answer 10

Structural: maintain integrity of CNS - ensuring neurones stay where should

Cell repair: allow neurones to be repaired (neuroglia - umbrella term for all nervous cells that are not neurones)

Facultative macrophages: morphology changes so can become immune cells

Maintain homeostasis: clear up ions and neurotransmitters; will take up any excess water in brain to protect neurones

Question 11

What is an oligodendrocyte?

Answer 11

CENTRAL NERVOUS SYSTEM

Provides myelin for neuronal axons; myelinates many axons

Question 12

What is a Schwann cell?

Answer 12

PERIPHERAL NERVOUS SYSTEM

Only myelinates one section of an axon

Question 13

What is a microglial cell>

Answer 13

Specialist brain macrophage

Question 14

What is an Ependymal cell?

Answer 14

Epithelial cell that lines the CSF vesicles and regulates their production/movement

Question 15

What is the resting membrane potential of a neurone caused by?

Answer 15

Extracellular: High Na and Cl
Intracellular: High K and protins

Question 16

What is the resting membrane potential of a neuron?

Answer 16

-70mV

Question 17

What are the two membrane channels essential for an action potential?

Answer 17

VGSCs

VGKCs

Question 18

Describe the process of an action potential:

Answer 18

1. At RMP, VGSCs and VGKCs are closed (and membrane impermeable)
2. Change in membrane potential leads to depolarisation to -40mV and VGSCs opening, causing an influx and full depolarisation to +40mV, closing VGSC and opening VGKCs
3. K+ efflux leads to hyperpolarisation of cell

Question 19

Why does the action of sodium on the membrane potential happen first?

Answer 19

VGKC opens and closes more slowly than VGSC

Question 20

How is the membrane repolarised?

Answer 20

Na+/K+-ATPase uses ATP hydrolysis to move 3Na+ across the membrane, changing shape and then 2K+ bind and are moved into cell as pump returns to resting configuration

Question 21

What is saltatory conduction?

Answer 21

When the high resistance and low capacitance of myelin allows the AP to jump between Nodes of Ranvier?

Question 22

Where are the Na+/K+ ATPase concentrated?

Answer 22

Nodes of Ranvier

Question 23

Describe Synaptic transmission:

Answer 23

AP opens VGCCs causing a Ca2+ influx that leads to vesicle exocytosis, so NTs are released to cleft; NTs bind to receptors of post-synaptic membrane which modulate activity