Biology 12

6.2 The Adrenal Glands and Stress

184 MHR • Unit 2 Homeostasis

The body has two adrenal glands, one on top of

each kidney. As shown in Figure 6.18, the adrenal

glandis composed of two layers: an outer cortex

and an inner medulla. Each layer produces different

hormones and functions as an independent organ.

While the cortex and the medulla do not interact,

they are both regulated by the hypothalamus. In

addition to many other functions, the adrenal gland

produces adrenaline, noradrenaline, and cortisol as

part of the body’s response to stress.

EXPECTATIONS

Describe the anatomy and physiology of the endocrine system and explain

its role in homeostasis.

Compile and display, either by hand or computer, data and information about

homeostatic phenomena in a variety of formats.

Describe some Canadian contributions to knowledge and technology in the

field of homeostasis.

adrenaline

spinal cord

(cross section)

noradrenaline

tracts

sympathetic

fibres

neuron

cell body

Stress response is short -term Stress response is long-term

neurosecretory cells

produce releasing hormone

anterior pituitary

secretes ACTH

glucocorticoids

mineralocorticoids

adrenal medulla adrenal cortex

path of nerve

impulses

hypothalamus

stress

ACTH

Figure 6.18Both the adrenal medulla and the adrenal

cortex are under the control of the hypothalamus when they

respond to stress. The adrenal medulla provides a rapid but

short-lived emergency response, while the adrenal cortex

provides a sustained stress response.

Stress response:

heartbeat and blood pressure increase

blood glucose level rises

breathing rate increases

muscles become energized

digestive system shuts down

Stress response:

protein and fat metabolism occur instead of

glucose breakdown

reduction of inflammation; immune cells

are suppressed

sodium ions and water are re-absorbed by kidney

blood volume and pressure increase