UNIT 4: ENDOCRINE SYSTEM (CHEMICAL COORDINATION)

(Campbell et.al, 2010 – CHAPTER 45)

ENDOCRINE SYSTEM The nervous system and the endocrine system work together

To regulate the activities of the other systems in the body.

Both systems use chemical signals when they respond to changes.

But they have different means of delivering the signals

Differences between the CNS and the endocrine system

Central nervous system

Endocrine system

Transmits electrical impulses

Transmits chemical biological messengers

Impulse send through neurons through neurotransmitters

Transmits message through bloodstream by means of hormones

Fast reaction Slow reactionReaction doesn’t last a long time

Reaction lasts a long time

ENDOCRINE GLANDSEndocrine system consist of different endocrine glands in the body.

Endocrine glands are ductless .And produce and secrete hormones. That are transported through the blood

in the blood vessels of the body.Towards a specific target organ where

it has a specific function.

ENDOCRINE GLANDSThe target cells only respond to specific hormones secreted by specific endocrine glands.

If the cell can respond to the hormone, the hormone and the receptor proteins bind together as a key fits into a lock.

EXOCRINE GLANDS Exocrine glands have ducts

and secrete chemicals like enzymes into these ducts which takes it to the lumen of organs or to the outside of the body.

HORMONES (CHEMICAL SIGNALS)

• Hormones are biological chemical messengers that help cells, body parts and even individuals to communicate with one another.

• Most hormones are proteins, but the steroids are fats.

• Hormones can inhibit or stimulate a reaction.

• Hormones are temperature, pH and substrate sensitive

ENDOCRINE GLANDS1. PITUITARY GLAND2. THYROID3. ADRENAL GLAND4. PINEAL GLAND5. PARATHYROID GLAND6. THYMUS7. PANCREAS8. GONADS

ENDOCRINE GLANDS

HYPOTHALAMUS AND PITUITARY GLAND

The hypothalamus controls the glandular secretions of the pituitary gland

PITUITARY GLAND Attached to a stalk onto the hypothalamus. Consist of a posterior- and anterior

pituitary. Posterior- (Pars nervosa) produce and

secrete the following hormones: ADH and Oxytocin.

Anterior- (Pars distalis) produce and secrete the following hormones: TSH, ACTH, prolactin, growth hormone, FSH and LH.

Posterior pituitary gland hormones: ADH and Oxytocin

ADH: Regulate the water reabsorption through the kidneys by changing the permeability of the renal tubules.

Oxytocin: Stimulates the uterus wall to contract during the process of giving birth and stimulates milk production during pregnancy.

How ADH functions

Anterior pituitary gland hormones: TSHACTH

prolactingrowth hormone

FSH LH.

TSH (THYROID STIMULATING HORMONE)

Stimulates the thyroid gland to secrete thyroxin.

Function by means of a negative feedback reaction.

TSH (THYROID STIMULATING HORMONE)

ACTH (Adrenocorticotropic hormone)

Stimulates the adrenal cortex to produce glucocorticoid that is released during stress.

PROLACTIN Control milk production in

females

Growth hormone

Promotes skeletal and muscular growth.

It stimulates the rate at which amino acids enter cells and protein synthesis occurs.

It promotes fat metabolism as opposed to glucose metabolism.

Growth hormone

DISORDERS CAUSED BY THE UNDERSECRETION OF GROWTH HORMONE

When a too little GH has been produced during childhood.

Normal proportions but small stature.

Low blood pressure. Can be rectified by

injecting the child with growth hormone

PITUITARY DWARFISM

DISORDERS CAUSED BY THE OVERSECRETION OF

GROWTH HORMONE

If too much GH have been produced during childhood.

Excessive growth of muscles and bones.

Usually have diabetes. Much taller than normal

children/adults.

GIGANTISM

Disorder of GH : ACROMEGALY

Caused by overproduction of GH in adults.

Enlargement of bones in the face, fingers and toes as a person ages.

FEEDBACK MECHANISMS CAUSED BY HORMONE ACTION

NEGATIVE FEEDBACK MECHANISM

FSH (follicle stimulating hormone) and LH

Stimulates the gonads (testis and ovaries) to produce sex hormones and gametes.

THYROID GLAND Located in the neck

around the trachea. Red – high blood volume 2 lobes connected by

isthmus. Uses Iodine to produce

the hormone thyroxin Thyroxin production is

stimulated by TSH secreted by the Hypophysis

Also secretes the hormone calcitonin

STRUCTURE OF THYROID GLAND

FUNCTIONS OF THYROXIN

Increase the metabolic rate of a person.

No specific target organ, they stimulate all cells of the body to metabolize at a faster rate.

Promotes the metabolism of glucose so that more energy is released.

DISORDERS OF THE THYROID GLAND

Disorder caused by the lack of Iodine in the diet.

Without iodine the thyroid is unable to produce thyroxin and continued anterior pituitary stimulation causes the gland to enlarge.

Retarded growth during infancy.

Body is short and stocky with mental retardation

SIMPLE GOITERCONGENITAL HYPOTHYROIDISM

Disorder of Thyroid Gland: Exophthalmic goiter

This goiter is due to an overactive thyroid gland

The eyes of a person protrudes because of edema in the eye socket tissue

Person is hyperactive, nervous, irritable, suffers from insomnia.

Sweat excessively and is heat sensitive.

Enlarged thyroid can be surgically removed and treated with radioactive iodine.

FUNCTIONS OF CALCITONIN

Regulates the Calcium level in the blood.

Calcitonin brings about the deposit of calcium in the bones when the level of calcium in the blood is too high.

When the blood calcium level lowers to normal, the release of calcitonin by the thyroid is inhibited.

This lower level of calcium in the blood, stimulates the release of parathyroid hormone (PTH) by the parathyroid glands.

PARATHYROID GLAND 4 parathyroid glands are located on the

thyroid. Secretes the hormone: Parathyroid

Hormone (PTH) PTH corrects a low blood calcium level PTH promotes the release of calcium by

the bones PTH promotes the reabsorption of

calcium from the kidneys PTH brings about the activation of

Vitamin D.

PARATHYROID GLAND

DISORDERS OF THE PARATHYROID GLAND

Insufficient PTH secreted.

Dramatic drop in blood calcium levels.

The body shakes from continuous muscle contraction

The blood calcium level becomes abnormally high.

Bones become soft and fragile.

Person irritable and prone to get kidney stones

TETANY HYPERPARATHYROIDISM

CALCITONIN AND PTH – ANTAGONISTIC HORMONES

These 2 hormones (Calcitonin and PTH) are antagonistic.

Both hormones work together regulate the blood calcium level.

When the blood calcium level is high – the thyroid gland secretes calcitonin.

When the blood calcium level is low – the parathyroid gland releases PTH

ADRENAL GLAND

Located ontop of the kidneys.

Consist of an inner part the adrenal medulla and outer part called the adrenal cortex.

The adrenal medulla secretes 2 hormones: adrenalin and nor-adrenalin.

STRUCTURE

FUNCTIONS OF ADRENALIN AND NOR-ADRENALIN

Brings about all the bodily changes that occur when an individual reacts to an emergency situation.

Effect of this hormone is short term. Released during fright,

anxiousness and anger. Increase heart rate. Increase blood flow and blood

pressure.

ADRENALIN and NOR-ADRENALIN

FUNCTIONS OF ADRENALIN AND NOR-ADRENALIN

Muscles absorb glucose for energy to react.

More blood (oxygen) to brain. Actions of the digestive system

inhibited. Pupils dilate to observe clearly

ADRENALIN and NOR-ADRENALIN

MALFUNCTION OF THE ADRENAL CORTEX

Bronzing of the skin

Excess amount of ACTH.

This lead to a buildup of melanin.

Excess cortisol in blood

Sub-cutaneous fat deposits.

ADDISON DISEASE CUSHING SYNDROME

PANCREAS The pancreas consist of exocrine tissue

with ducts that produce and release digestive juice (pancreatic sap) into the duodenum, and endocrine tissue without ducts that secrete hormones directly into the bloodstream.

The endocrine tissue is know as the Islets of Langerhans and it secretes two hormones: Insulin and glucagon (antagonistic hormones).

PANCREAS

FUNCTIONS OF INSULIN IN THE PANCREAS

If blood sugar (glucose) level is high. Insulin is secreted. Insulin stimulates the uptake of glucose

by the cells (liver, muscle and adipose) In the liver and muscles it is stored as

glycogen. Muscle cells break it down for energy. Fat cells convert it to glycerol for the

forming of fat. Therefore insulin lowers the blood

sugar level.

FUNCTIONS OF GLUCAGON

When the blood sugar level is low.

Glucagon is secreted into the blood.

Glucagon stimulates the liver cells to convert glycogen into glucose for energy production.

Therefore glucagon raises the blood sugar level.

DIABETES MELLITUS Type 1 Diabetes: Pancreas is not

producing insulin Islets of Langerhans

damaged. Glucose accumulate

in blood. Coma results if not

treated with insulin injections.

Treatment of Diabetes:

Self study

TESTIS AND OVARIES Testis produce

testosterone (male sex hormone)

Stimulates the formation of male traits during puberty

Stimulates oil and sweat glands.

Stimulates hairloss (baldness)

Ovaries produce estrogen and progesterone (female sex hormones)

Estrogen stimulates growth of the uterus and vagina during puberty and secondary sexual female traits.

Stimulate egg production and preparation of the uterus for pregnancy.

Progesterone prepare the uterus wall for possible implantation of an embryo.

HORMONES PRODUCED BY THE TESTIS HORMONES PRODUCED BY THE

OVARIES

Effects of testosterone on males

Effects of estrogen and progesterone in females