Neurons & Neurotransmission

Question 1

Name the five key parts of the neuron

Answer 1

• dendrite
• cell body/soma
• axon hillock
• axon
• synapse

Question 2

What is the function of a dendrite?

Answer 2

Receives inputs from other neurons and convey graded electrical signals passively to the soma

Question 3

Describe the contents of the soma

Answer 3

Synthetic and metabolic centre it contains nucleus, ribosomes, mitochondria and ER

Question 4

What is the function of the axon of hillock?

Answer 4

site of initiation of all or none action potentials

Question 5

What is the function of the axon?

Answer 5

Conducts output signals as action potentials to the presynaptic terminal

Question 6

In what direction do chemicals move in an axon?

Answer 6

Retrograde and anterograde

Question 7

What happens at the synapse?

Answer 7

Point of chemical communication between neurons/other cells

Question 8

How are neurons classified?

Answer 8

According to shape - number and conformation of processes (neurites)

Question 9

State four types of neuron

Answer 9

• unipolar (one neurite)
• pseudounipolar (bifurcation of axon gives rise to two terminals)
• bipolar (two neurites)
• multipolar (three or more neurites, cell body gives rise to multiple dendrites)

Question 10

Where are each type of neuron found?

Answer 10

Unipolar - peripheral autonomic neuron
Pseudounipolar - dorsal root ganglion
Bipolar - retinal ganglion
Multipolar - lower motor neuron

Question 11

State four functional regions of a neuron

Answer 11

• input
• integrative (soma/axon of hillock)
• conductile
• output (release of neurotransmitter)

Question 12

What leads to the shape of the action potential?

Answer 12

Upstroke - sodium influx

Down stroke - potassium efflux

Question 13

What two factors affect how far an action potential will travel?

Answer 13

Membrane resistance (leakiness) 
Axial resistance (impedance)

Question 14

What happens to the amplitude of the action potential as it moves along the axon?

Answer 14

Remains constant

Question 15

Why do passive signals not travel far?

Answer 15

Membrane is leaky due to reduced change in potential

Question 16

How do you increase the spread of an action potential?

Answer 16

Decrease axial resistance (axon diameter)

Increase membrane resistance (insulator)

Question 17

Name two types of insulator cell

Answer 17

Schwann cell (PNS)
Oligodendrocyte (CNS)

Question 18

Describe the node of ranvier

Answer 18

Concentration of ion channels due to a gap in myelin sheath leads to saltatory conduction which action potentials jump between nodes

Question 19

What is the general process of neurotransmission?

Answer 19

1. Uptake of precursor
2. Synthesis of transmitter
3. Storage of transmitter
4. Depolarisation by AP
5. Ca2+ influx by voltage activated channels
6. Ca2+ induced release of transmitter
7. Receptor activation
8. Enzyme mediated inactivation of transmitter or re-uptake of transmitter

Question 20

Name the two membrane involved in a chemical synapse

Answer 20

pre synaptic and post synaptic

Question 21

What holds the two synaptic membranes together?

Answer 21

Matrix of extracellular protein in the cleft

Question 22

How can you distinguish between pre and post synaptic membranes?

Answer 22

Pre - vesicles that store neurotransmitter in active zones

Post - density containing lots of receptors

Question 23

Name three types of synapse based on the location of the synapse

Answer 23

• axodendritic (very common)
• axosomatic (common)
• axoaxonic (rare)

Question 24

Name two types of synapse based on function

Answer 24

Excitatory

Inhibitory

Question 25

Describe and give an example of an excitatory synapse

Answer 25

CNS most frequently glutamate activates post synaptic cation selective ionotropic receptors and leads to local graded depolarisation

Question 26

What causes an e.p.s.p?

Answer 26

Sodium influx

Question 27

Describe and give an example of an inhibitory synapse

Answer 27

CNS most frequently GABA/glycine activates post synaptic anion ionotropic receptors to generate a local graded hyperpolarisation

Question 28

What causes an i.p.s.p?

Answer 28

Chloride influx

Question 29

State the two types of integration

Answer 29

Spatial | Temporal

Question 30

Describe spatial integration

Answer 30

Many inputs converge upon a neuron to determine its output

Question 31

Describe temporal integration

Answer 31

Single input may modulate output by variation in AP frequency of that input

Question 32

Where are peptides released from?

Answer 32

Secretory vesicles

Question 33

Where are amino acids/amines released from?

Answer 33

Synaptic vesicles

Question 34

What type of channels mediate fast neurotransmission?

Answer 34

Ionotropic ligand gate ion channels

Question 35

What type of receptor mediate slow neurotransmission?

Answer 35

G protein coupled receptors

Question 36

Name the one neurotransmitter that does not activate G protein coupled receptors

Answer 36

Glycine

Question 37

State the two key types of receptor

Answer 37

Ionotropic receptor | Metabotropic receptor

Question 38

Describe the metabotropic receptor

Answer 38

Receptor and channel are distinct, slow and indirect

Question 39

Name three artificial glutamate receptors

Answer 39

- AMPA - Kainic Acid - NMDA

Question 40

Describe non-NMDA receptors

Answer 40

Sodium and potassium permeable channel that is fast and excitatory

Question 41

Describe NMDA receptors

Answer 41

Sodium, potassium and calcium permeable, slow and excitatory

Question 42

How do glutamate metabotropic receptors work?

Answer 42

By secondary messenger cascade, no specific ion channel but can be inhibitory

Question 43

What are the two key types of supporting cell in the nervous system?

Answer 43

Ependymal | Glia

Question 44

Describe ependymal cells

Answer 44

Ciliated cells that line the ventricles of the brain and central canal of the spinal cord.

Question 45

What is the function of ependymal cells?

Answer 45

Contribute to formation and circulation of CSF and have a role in early development

Question 46

Name two types of glial cells

Answer 46

Microglia | Macroglia

Question 47

Describe microglia

Answer 47

Phagocytes that engulf debris and involved in the relationship between CNS and immune system

Question 48

Name the four types of macroglia

Answer 48

- astrocytes - oligodendrocytes - schwann - capsular

Question 49

What do the astrocyte processes do?

Answer 49

- subpial end feet on the surface of the brain and spinal cord - perivascular end feet at the capillaries of blood brain barrier - contacts with neurons

Question 50

State five functions of the astrocytes

Answer 50

- control electrolyte balance - produce neurotrophins - uptake neurotransmitters - supply glutamine for synthesis of glutamate - regulate tightness of BBB

Question 51

Describe oligodendrocytes

Answer 51

Small cells with few processes - processes form myelin sheath around multiple CNS axons and produce neurotrophic factors that are important in repair of damaged axons in CNS

Question 52

Describe Schwann cells

Answer 52

Each cell is only a short segment of one axon and cells spiral around the axon to form the lamella

Question 53

What is the purpose of schwann cells?

Answer 53

Vital in regeneration of transected axons - they proliferate to form a tube which growth sprouts from the proximal end to re-innervate the de-innervated target

Question 54

Where are capsular cells found?

Answer 54

Surround neuronal cell bodies in sensory and autonomic ganglion

Question 55

Describe the structure of capsular cells

Answer 55

Flattened cells form an almost complete layer that separates ganglion cell bodies in the DRG and cranial nerves from the surrounding tissue and vasculature

Question 56

Where are capsular cells found?

Answer 56

Autonomic ganglion particularly the sympathetic division