Chemical Transmission in the Nervous System

Question 1

Give a pathological overview of the peripheral nervous system.

Answer 1

The autonomic and somatic nervous systems are inherently related to the pathology and therefore pharmacology of many different conditions including but not limited to asthma & COPD, angina, heart failure, hypotension, glaucoma etc.
It is also important in the use and application of anaesthetics.

Question 2

Outline nerve structure and function.

Answer 2

The cell body receives signals; the axon conducts that signal and the terminal(s) transmits that signal.

Question 3

What is the significance of Loewi’s experiment?

Answer 3

We are aware that a chemical transmitter is involved in the transfer of signals between nerves because of Loewi’s experiment in which the stimulation of the vagus nerve reduced the beating of the donor heart and then that of the recipient heart.

In 1936, Sir Henry Dale and Otto Loewi won the Nobel prize in physiology or medicine for their discoveries relating to chemical transmission of nerve impulses.

Question 4

What is the major site for pharmacological manipulation of the nerves?

Answer 4

• The synapse

Question 5

How is the nervous system organised?

Answer 5

Sensory (Afferent) nerves take signals to the central nervous system that then carry them to the peripheral nervous systems via afferent nerves.

Question 6

Explain the difference between the symapthetic and parasympathetic nervous system in terms of structure.

Answer 6

Parasympathetic: Long pre-ganglionic axon, short post ganglionic axon. Ganglia are situated at the organ.

Sympathetic: Short pre-ganglionic axon, long post-ganglionic axon. Ganglia are close to the CNS.

Question 7

Explain what is meant by the somatic and autonomic nervous systems.

Answer 7

Somatic: (voluntary)

• single fibre leaves the CNS
• innervates Skeletal Muscle

Autonomic: (involuntary)

• two fibre system in which preganglionic fibres come from the CNS and postganglionic fibres come from autonomic ganglia
• innervates most organs/tissues of the body

Question 8

Name two chemical transmitters of significant importance in the PNS.

Answer 8

acetylcholine (ACh) & noradrenaline (NA)/norepinephrine

Question 9

What are some receptors for Ach and NA?

Answer 9

Acetylcholine: Nicotinic receptors (LGIC) & Muscarinic receptors (GPCR)
Noradrenaline: α & β- adrenoceptors (GPCRs)

Multiple subtypes of these receptors exist.