(A Level) Nervous and endocrine coordination

Learning objectives

Describe the endocrine system using ADH, glucagon and insulin as examples, and compare hormonal and nervous communication in speed, duration, route and range of targets.

Describe the structure and function of sensory and motor neurones, state that intermediate neurones connect them, and outline how a receptor cell turns a stimulus into impulses, using a chemoreceptor in a taste bud as the example.

Explain how the resting potential of about −70 mV is maintained by the sodium–potassium pump and by potassium ions leaking out through open channels.

Explain depolarisation, repolarisation and hyperpolarisation during an action potential in terms of voltage-gated sodium and potassium channels, and how the refractory period restores the resting potential, keeps impulses separate and one-way, and limits their frequency.

Explain how myelin and saltatory conduction between nodes of Ranvier make impulse transmission faster.

Label the parts of a cholinergic synapse and explain transmission across it: calcium ions entering the presynaptic knob, exocytosis of acetylcholine, binding to receptors that depolarise the postsynaptic membrane, and hydrolysis by acetylcholinesterase.