WEEK 3 - Peripheral Nervous System, Adrenergic System, and Cholinergic System

Question 1

Briefly explain what the Nervous System comprises of…

Answer 1

The NS is a complex circuitry comprising of:
- > 10 billions neurones (of which each can have 100s - 1000s of synapses).
- With supporting cells including Schwann cells, and Oligodendrocytes.

Question 2

Give an example/s of neurotransmitters:

Answer 2

• Acetylcholine (Ach)
• Noradrenaline (NA)

Question 3

Briefly list, and if possible explain, the different branches of the Nervous System…

Answer 3

Nervous System —> CNS or PNS

PNS —> Somatic (voluntary control of skeletal muscle) OR Autonomic (involuntary control of smooth muscle, cardiac muscle, and some exocrine secretions).

Autonomic —> Sympathetic NS OR Parasympathetic NS

Question 4

List the functions of the Sympathetic Nervous System…

Answer 4

• Overall effect is excitatory.
• Active during stressful conditions.
• Neurotransmitter = Noradrenaline.
• Pre-ganglionic fibre emerges from spinal nerves only.
• Its components are consolidated so as to have a visibly distinct anatomical entity.

Question 5

List the functions of the Parasympathetic Nervous System….

Answer 5

• Overall effect is inhibitory.
• Active during relaxing times.
• Neurotransmitter = Acetylcholine.
• Pre-ganglion is fibre emerges from spinal and cranial nerves.
• Its components are isolated and don’t have a visibly distinct form.

Question 6

Explain the core differences between Noradrenaline and Acetylcholine…

Answer 6

Noradrenaline has Adrenergic receptors (alpha and beta).

Acetylcholine has Cholinergic receptors (nicotinic and muscarinic receptors).

Question 7

What are Adverse Effects usually due to in terms of Pharmacology…

Answer 7

• Excessive target receptor activation / blockade.
• Activation / blockade of the receptor in a different tissue than intended.
• incorrect receptor activated / blocked.
• Chronic use: desensitisation and super-sensitivity.

Question 8

Briefly explain the Noradrenaline Adrenorceptors…

Answer 8

Beta:
B1/B2/B3 - Gs is the main signalling mediator - its main action is activating adenylyl cyclase.

Alpha:
a1 - Gq is the main signalling mediator - its main action is activating phospholipase C.
a2 - Gi is the main signalling mediator - its main action is inhibiting adenylyl cyclase.

Question 9

What are the drugs affecting the Sympathetic NS…

Answer 9

• Inhibitors of Noradrenaline storage.
  [e.g. Pseudoephridrine]
• Receptor Agonists: Alpha and Beta.
  [a1: phenylephrine, oxymetazoline / a2: Methyldopa]
  [ B1: dobutamine / B2: Salbutamol]
• Receptor Antagonists: Alpha and Beta.
  [a1: prazoin, tamsulosin / a2: — ]
  [ B1/B2: Beta Blockers]

Question 10

What are the ADRs of beta blockers…

Answer 10

• Respiratory: Bronchodilation.
• Cardiovascular: Braachycardia, Hypotension, cold extremities.
• CNS: Sedation.
• Metabolic: issues for diabetics (exaggerated hypoglycaemia, or masked effects of hypoglycaemia) OR ADRs on blood lipids.
• Impotence (inability to take effective action).

Question 11

Briefly explain the types of Cholinergic receptors…

Answer 11

Also called Muscarinic receptors:
- M1; neural
- M2; Cardiac
- M3; Glanandular / smooth muscle
- M4 & M5; mainly found in CNS

Question 12

Explain Anti-Cholinesterase, and its types:

Answer 12

Mechanism of action:
- Inhibit AChE at the active site.

Types:
- Reversible (short acting - e.g. Edrophonium) (Medium acting -e.g. Carbamates)
- Irreversible (Organophosphates).

Question 13

Explain the clinical uses of Anti-Cholinesterases…

Answer 13

Reversible:
USE ; Myaesthenia gravis.

• Autonomic disease.
• Body generates antibodies against Nm receptor.
• Inhibits signalling at the neuromuscular junction.
• Causes muscle weakness.
• Diagnosis; Edrophonium administered (lasts 45 minutes, where improvement suggests diagnosis).
• Treatment; Neostigmine.