Endocrine System

What you need to know

Role of Hormones

• help maintain homeostasis –by causing or preventing change in

target cells

• is slower than the nervous system but has longer effect. • Endocrine system and Nervous

system work together.

Glands

Brain• Pineal • Hypothalamus• PituitaryNeck• Thyroid

Thorax• Thymus.Abdomen/scrotum• Ovaries and

testes• Adrenal• Pancreas islets

Hypothalamus

• regulates the internal environment through the autonomic system. • It controls heart beat, temperature,

water balance, as well as glandular secretions of pituitary gland.

Pituitary Gland

• Is connected to hypothalamus by a stalk. • ~ 1 cm in diameter and lies just

below the hypothalamus.• Has two parts: posterior pituitary

and anterior pituitary.

Posterior Pituitary

• Hypothalamus releases products into posterior pituitary where they are stored and will eventually trigger production of hormones.

• Hypothalamus releases two products– Oxytocin– ADH (Antidiuretic hormone)

Oxytocin

• Involved in positive feedback• stimulates; –uterine muscle contraction–release of milk from mammary

glands. –In males, it is associated with sperm

transport.

ADH

Promotes absorption of water in kidneys1.Nerve cells in hypothalamus detect

concentrated blood; ADH released and kidneys reabsorb water.

2.As blood becomes dilute, ADH is no longer released.

3.What kind of feedback is this?

Anterior Pituitary

• Neurohormones synthesized in the hypothalamus regulate release of 6 hormones from anterior pituitary

Six Hormones from anterior pituitary

Hormones that go to other glands1. Thyroid-stimulating hormone (TSH)

thyroxin. 2. Adrenocorticotropic hormone (ACTH)

cortisol.3. Gonadotropic hormones: (follicle-

stimulating hormone [FSH] and luteinizing hormone [LH]) secrete sex hormones.

• Hormones with direct effects on body1.Prolactin (PRL) is produced in quantity

only after childbirth 2.Melanocyte-stimulating hormone (MSH) 3.Growth Hormone (GH or somatotropic

hormone)

Thyroid

• Produces 4 hormones1.T3 thyroxine

2. T4 triiodothyronine– Which target all cells of body– Increase metabolic rate

3.Calcitonin– Targets bones– Lowers blood calcium levels

4. PTH (Parathyroid hormone) – Targets kidneys– Increase Calcium uptake in kidneys

and intestines, releases calcium from bones

Adrenal Glands

• On top of kidneys• Each has two parts – outer cortex

and inner medulla

Inner medulla

• Produces: Epinephrine and norepinephrine• Causes fight of flight response– Blood glucose level rises– Metabolic rate increases– Bronchioles dilate – Breathing rate increases– Blood vessels to digestive tract and skin constrict;

those to skeletal muscles dilate– Cardiac muscle contracts more forcefully and heart

rate increases

Cortex

Produces Cortisol and Aldosterone• Cortisol– Breaks down of muscle protein to amino acids – Breaks down fatty acids– Raises blood glucose levels.– Counteracts inflammatory response

Aldosterone • Primary target organ is kidney• Promotes uptake of Na + to help control low

blood pressure

Pancreas

Composed of two types of tissue• Exocrine tissue produces and secretes

digestive enzymes • Endocrine tissue called pancreatic islets (of

Langerhans) produce insulin and glucagon

All body cells utilize glucose; therefore, its level must be closely regulated.

• Insulin is secreted when blood glucose level is high

Three actions of insulin

1. Stimulates liver, fat, and muscle cells to take up glucose

2. Stimulates liver and muscles to store glucose as glycogen.

3. Promotes buildup of fats and proteins - inhibits their use as an energy source.

Three types of hormones

• Peptides• Amino acids• Lipids

How hormones interact with target cells

1. Amino acids and peptides - bind to receptors on outside of cell (not lipid soluble)

2. (double messenger system) a) Peptide hormones are the first messenger; b) cAMP and calcium are often the second

messengerc) sets an enzyme cascade in motion, which

produces response

Lipid Soluble

• Steroids/lipids enter cells by crossing cell membrane (lipid soluble) and bind to receptors on nuclear membrane/envelope

• Hormone-receptor complex binds to DNA resulting in activation of genes that produce enzymes required for response

Task 1

• Design an experiment to show the effects of the removal of the thyroid gland in mice. Identify the physiological characteristics that should be observed and explain how the data should be recorded.

Task 2

• Perform the laboratory activities provided to illustrate some aspects of the endocrine system. These may include the following: – microscopic examination of pancreas to

distinguish endocrine tissue from digestive enzyme producing

– growth of plants in response to hormonal stimulation

Feedback• analyse homeostatic phenomena to identify the

feedback mechanisms involved (317-2)• hypothalamus-pituitary complex include RF

(releasing factor), pituitary hormones and target tissues (e.g., TSH on thyroid).

• ID of Hyperglycemia, p. 400 • Effects of Hormones on BloodSugar, p. 401• Hormonal Control of Metamorphosis, pp.

402–3• Hormone Levels During the Menstrual Cycle,

p. 404

Task 3Effects of Hormones on Blood

Sugar, p. 401Task 4

Hormonal Control of Metamorphosis, pp. 402–3

Task 5Hormone Levels During the

Menstrual Cycle, p. 404

Tasks 3

• Analyse and interpret the data provided on blood or urine composition. Use it to determine the role of hormones in homeostasis. (317-2)

Task 5

Task 6