The endocrine system

What is the endocrine system?

The endocrine system is a network of glands that produce and secrete hormones (chemical messengers) into the bloodstream, to regulate the body’s functions.

Works closely with the nervous system to control behaviour and maintain homeostasis.

It works alongside the nervous system but acts slower and has longer lasting effects.

What are glands?

Organs that produce hormones

What are the endocrine glands?

(7)

Pituitary gland, Adrenal gland, Ovaries, Testes, Pancreas, Pineal.

What are hormones?

Chemical messengers that;

• Travel through the bloodstream

• Have widespread effects but only act on target organs.

• Regulates physiological processes; growth, mood, metabolism, stress, reproduction.

• Hormones only affect target cells in target organs which have specific receptors.

• E.g. Adrenaline, cortisol, testosterone, oestrogen, progesterone.

What does the pituitary gland do?

What are the 2 parts?

Master gland, controls the release of hormones from other glands.

Controlled by the hypothalamus in the brain.

Has 2 parts;

• Anterior pituitary; secretes the hormones; ACTH, LH, FSH, Growth hormones.

• Posterior pituitary; Secretes the hormones; Oxytocin and ADH.

What hormones does the anterior pituitary secrete and what is their function?

• ACTH; Stimulates the adrenal cortex to release cortisol. (Stress hormone)

• LH & FSH; Involved in the reproductive system - stimulates ovaries and testes.

• Growth hormones; Stimulates growth and cell reproduction.

What hormones do the posterior pituitary hormones secrete and what is their function?

• Oxytocin; Involved in uterine contractions, lactation and possible attachment and emotional bonding.

• ADH; Regulates water balance in the body.

What does the adrenal gland do?

2 parts

Located ontop of the kidneys.

Has 2 parts;

• Adrenal medulla (inner part); Involved in acute stress (fight or flight)

• Adrenal cortex (Outer part); Involved in chronic stress and vital functions

What hormones does the adrenal medulla release?

Adrenaline; Increases heart rate, Expands air passage, dilates pupils, inhibits digestion. Starts the fight or flight response

Noradrenaline; Works with adrenaline, constricts blood vessels → raises blood pressure, increases attention and alertness. Maintains the fight or flight response

What hormones does the adrenal cortex secrete?

• Cortisol; helps regulate metabolism, reduces inflammation, and manages long term stress. Too much can suppress the immune system.

What do the ovaries do?

Located in the female reproductive system.

Governed by LH and FSH in the pituitary gland.

Secretes the hormones Progesterone and Oestrogen.

What do the hormones secreted by the ovaries do?

Oestrogen; Development of female secondary sex characteristics, regulates menstrual cycle, affects mood and behaviour.

Progesterone; Maintains pregnancy, regulates menstrual cycle and may influence mood.

What do the testes do?

Located in the male reproductive system.

Also stimulated by LH and FSH.

Produces and secretes testosterone.

What do the hormones secreted by the testes do?

Testosterone; Development of male secondary sex characteristics, linked to aggression, sexual behaviour and muscle growth.

What does the pineal gland do?

Regulates biological rhythms - sleep/wake cycle (circadian rhythm)

Works closely with the SCN (Suprachiasmiatic nucleus) in the brain.

Releases the hormones melatonin

What does the hormone released by the pineal gland do?

Melatonin; makes you feel sleepy, levels increase in darkness, helps regulate the body clock.

What does the pancreas do?

The pancreas regulates blood sugar levels, also part of the digestive system.

Releases the hormones; insulin and glucagon.

What do the hormones secreted by the pancreas do?

Insulin; Lowers blood sugar by helping cells absorb glucose.

Glucagon; raises blood sugar by triggering the release of glucose stored in the liver.

What does the thyroid do?

Regulates metabolism, growth and energy levels.

Releases the hormone thyroxine

What does the hormone released by the thyroid do?

Thyroxine

Controls the rate of metabolism, affects heart rate, body temperature and growth.