Neuronal Cell

Question 1

Describe a neurones dendrites?

Answer 1

They are short, tapered and highly branched with specialised surfaces for contacts with other neurones so that they can revived impulses. And their cytoplasm contains mitochondria and nissl bodies.

Question 2

Describe a neurones axon?

Answer 2

Long, thin, cylindrical shaped and contain mitochondrial, microtubules and neurofibrils for impulse conduction away from the soma. They have no ER and don’t synthesise proteins.

Question 3

What is the:

a) axon hillock?
b) trigger zone?
c) axoplasm?
d) axolemma?
e) axonal collaterals?
f) axon terminals?
g) synaptic end bulbs?

Answer 3

a) where the soma joins the axon
b) where most signals arrive, the junction of hillock and initial segment
c) cytoplasm
d) plasma membrane
e) axon side branches
f) ends of axons/collaterals
g) swollen tips containing neurotransmitter vesicles

Question 4

What are multipolar, bipolar and unipolar neurones?

Answer 4

Multipolar: several dendrites and one axon, most common cell type in brain and spinal cord.
Bipolar: one main dendrite and one axon, in retina, olfactory and inner ear
Unipolar: axon and dendrite fuse and branch at soma, only involved in one process (sensory)

Question 5

What is the functional classification of neurons?

Answer 5

Sensory afferent, interneurones and motor efferent

Question 6

Describe the mechanism of an action potential?

Answer 6

1. Resting potential, -70mV
2. Influx of sodium ions through voltage-gated channel
3. Membrane potential rises due to depolarisation
4. When at 30 mV voltage-gated potassium channels open and polarise the cell
5. Hyperpolarisation phase aka refractory period
6. Resting potential.

Question 7

What are rate limiting steps in action potentials?

Answer 7

Properties of the axon, presence or absence of a myelin sheath, axon diameter (larger is faster)

Question 8

What can inflammation in multiple sclerosis causes?

Answer 8

Demyelination

Question 9

What are the two types of SNARE proteins?

Answer 9

T-SNARES (or Q) which associate with target membranes or V-SNARES (or R) which associates with vesicle membranes.

Question 10

What are the steps by which SNARES work?

Answer 10

1. Vesicles approach and SNARES zip together from their N-termini
2. Hemi fusion occurs
3. Two bilayer leaflets that were further apart form a new bilayer
4. Fusion pores are formed
5. The fusion pores expands as the membranes relax.

Question 11

What two things can neurotransmitter a cause?

Answer 11

Channels to open or secondary messengers to act

Question 12

Give examples of
a) small molecule 
b) biogenic amine
c) amino acid 
d) peptide 
e) gases
neurotransmitters?

Answer 12

a) acetylcholine
b) dopamine, adrenaline, serotonin
c) GABA, glutamine, aspartate, glycine
d) endorphins, substance P, somatostatin
e) NO, CO

Question 13

Give the life cycle of a neurotransmitter?

Answer 13

1. Synthesis
2. Storage
3. Release
4. Receptor activation
5. Transmitter inactivation

Question 14

Give some examples of neurodegenerative disorders?

Answer 14

Alzheimer’s, Parkinson’s, Huntington, Prion, Amyotrophic lateral sclerosis, Familial British dementia.

Question 15

What are the symptoms of Alzheimer’s caused by?

Answer 15

Nerve cells in the brain dying, connection degenerating, loss of the hippocampus, intracellular neurofibrillary tangles and extracellular amyloid plaques.

Question 16

What do current drugs for Alzheimer’s do?

Answer 16

Don’t cure, can relieve some symptoms.

Eg. Cholinesterase inhibitors: Aricept and Exelon and NMDA antagonists: Ebixa

Question 17

What causes a) Parkinson’s, b) Huntington’s, c) prion, d) amyotrophic lateral sclerosis and e) familial British dementia?

Answer 17

a) Lewy bodies in nigral neuron
b) intramuscular and cytoplasmic inclusions
c) PrPsc deposition
d) SOD1 inclusion bodies
e) amyloid disposition.

Question 18

Describe a neurones cell body?

Answer 18

aka Soma.
Contains a single nucleus with prominent nucleolus, nissl bodies have rough ER and free ribosomes for protein synthesis, shape and support provided by neurofilaments/fibrils, microtubules are used for transport.