Biology

The Endocrine system

The endocrine system

• Have ductless glands, endocrine glands, which secrete hormones into the bloodstream

• The certain organs that the hormones reach are called as target organs.

• Responses of body to hormones are slow• Excess of hormone production illness

The endocrine glands

• Thyroid• Adrenal• Pancreas• Reproductive • organs• Pituitary gland

• situated in front of neck – in front of windpipe• produces thyroxine (made from iodine and amino acid)

• Effects metabolic rate• Controls level of activity• Promotes normal skeleton growth• Essential for normal development

of the brain

Thyroid gland

The endocrine glands

The endocrine glands

• attached to back of abdominal cavity, above kidneys• outer layer adrenal cortex• inner zone adrenal medulla• produces hormones:

Adrenaline - Adrenaline on the body causes a rise in body glucose and it increases heart rate. It also constricts the blood vessels, dilates air passages and also participates in the fight-or-flight response of the sympathetic nervous system of the body. Epinephrine is another name for adrenaline.

Corticosteroids - are a class of chemicals that includes steroid hormones naturally produced in the adrenal cortex. Control metabolism of carbohydrates, fats, proteins, salts and water

Adrenal glands

The endocrine glands

• also a digestive gland• the hormone producing cells are arranged in islets• hormones produced:

• Glucagon - comes into the scene when sugar level in blood becomes low

• Insulin – comes into the scene when sugar level in blood becomes high

Pancreas

The endocrine glands

•IN FEMALES:• Oestrogen• Progesterone

•IN MALES:• Testosterone

Reproductive organs

The pituitary gland is an endocrine gland – hence it produces hormones.Hormones it produces: Antidiuretic hormone (ADH) -

acts on kidneys; regulates water reabsorption in kidney tubules

Growth hormone – affects growth rate of whole body

Follicle-stimulating hormone (FSH) – reaches ovaries and makes one of the follicles start to mature and to produce oestrogen

Luteinizing hormone (LH) – together with FSH, induces ovulation

Thyroid-stimulating hormone (TSH) - acts on thyroid gland; makes it produce thyroxine

Pituitary Gland

The endocrine glands

Fate of hormones

hormones

bloodstream

Spent hormones

Liver

Spent hormones are converted to inactive substances by the liver

Excretedbykidneys

brain

pituitary gland

follicle-stimulating hormone (FSH)

ovary

oestrogen

oestrogen

uterus

Homeostasis and negative feedback

A follicle is a group of cells enclosing an ovum (egg cell). The follicle enlarges, and protrudes from the surface of the ovary before bursting and releasing its ovum