IGCSE Biology 0610: Adrenaline and Comparing Nervous with Hormonal Control

A lifeguard at a busy swimming pool spots a swimmer struggling in the deep end and immediately prepares to dive in for a rescue. In the few seconds before diving in, the lifeguard's heart pounds faster, their breathing quickens, and their pupils widen.

(a) Name the gland that releases the hormone responsible for these changes, and name this hormone. [2]

(b) State two of the effects described above that this hormone produces on the lifeguard's body. [2]

(c) The lifeguard's nervous system also plays a part, sending nerve impulses to the leg muscles so the lifeguard can run and dive. Compare the speed of action and the duration of effect of this nervous response with the hormonal response described in (a) and (b). [2]

Part (a): Identifying the gland and hormone

The sudden increase in heart rate, breathing rate and pupil diameter, all happening together as the lifeguard prepares for sudden action, is characteristic of the “fight or flight” response.

This response is triggered by adrenaline, a hormone released by the adrenal glands directly into the blood.

Part (b): Effects of adrenaline

Adrenaline prepares the body for rapid physical action. Of the changes described, the effects produced by adrenaline include:

increased heart rate
increased breathing rate
increased pupil diameter

(Any two of these would be creditable.)

Part (c): Comparing nervous and hormonal control

Both the nervous system and the hormonal system are coordinating the lifeguard’s response, but they act differently:

Speed of action: nerve impulses travel electrically along neurones and act almost instantly, allowing the leg muscles to respond within a fraction of a second. Adrenaline, in contrast, has to be carried by the blood from the adrenal glands to its target organs, so it acts more slowly.
Duration of effect: the nervous response is very short-lived, the muscles stop contracting as soon as the impulses stop arriving. The hormonal response, by contrast, builds up and lasts for a longer period, keeping the lifeguard’s heart rate and breathing rate raised throughout the whole rescue, not just for the instant of diving in.

Final answers

(a) Adrenal glands; adrenaline.
(b) Any two of: increased heart rate, increased breathing rate, increased pupil diameter.
(c) Nervous control is fast but short-lived; hormonal control is slower but longer-lasting.