Chapter 16: The Endocrine System

Objectives Define the terms endocrine and

exocrine.

Describe the physiology of hormones including the different types and the mechanisms of their actions.

Compare endocrine and neural controls of physiology.

Functions System of glands and cells make hormones

Alters metabolic activities of many tissues and organs simultaneously

Regulates long-term processes: growth development reproduction

What is a Hormone? A chemical messenger that is produced

at one site and carried by the blood to its site of action (target cells)

Mechanism of Hormone Action Hormones produce one or more of the

following cellular changes: alter plasma membrane permeability

stimulate protein synthesis

activate or deactivate enzyme systems

induce secretory activity

stimulate mitosis

Homeostasis Homeostasis maintaining internal balance

in the body organism must keep

internal conditions stable even if environment changes

also called “dynamic equilibrium”

How we maintain homeostasis nervous system endocrine system

What is the functional significance of the differences between the two systems?

Endocrine System Nervous System

Chemical signals control body functions

Is unable to handle split-second responses

Nerve signals control body functions

Handles crisis management

Endocrine vs. Exocrine

Endocrine Glands Exocrine Glands

Glandular secretory cells that release their secretions directly into the blood stream

The glands are called ductless

Secrete their products onto epithelial surfaces-

(skin or mucosa)

The glands that have ducts

Glands Hypothalamus Pituitary Thyroid Parathyroid Adrenal Pineal Pancreas Thymus Gonads

Hypothalamus

Hypothalamus Links the nervous system to the

endocrine system

Controls: body temperature

hunger

thirst

fatigue

sleep

circadian cycles

Controlling Body Temperature

high

low

nerve signals

sweat

nerve signals

brain

body temperature

shiver brain

dilates surface blood vessels

constricts surface blood vessels

Pituitary Gland Functions: stimulates the elongation of bones in the

body

“master gland” since it regulates endocrine functions

Hormone: growth hormone

Location: base of the brain, below hypothalamus

Pituitary Gland

Pituitary Gland Hormones

Pituitary Gland Hormones

Pituitary Dwarfism

Gigantism

Andre the Giant At 7'4" and 500 pounds,

Andre the Giant could have been famous for his size alone. His drive, talent and ambition, however, proved to be as big as Andre himself, and the wrestler became legendary for his achievements in and out of the ring.

Acromegaly Occurs in adults

Bones of hands face and feet are enlarged

Due to the release of growth hormone in adults

Thyroid Gland Functions:

controls metabolism

regulates tissue growth

maintains blood pressure

glucose oxidation

makes proteins

Location:

by the Adams apple

largest gland in the body

Thyroid Gland

Goiter Not enough iodine

in the diet (iodine deficiency)

Causes swelling of the thyroid gland

Goiter

Graves Disease Overactive thyroid

Excessive amounts of thyroid hormones are produced

Inflammation of the eye muscles by attacking autoantibodies

Parathyroid Glands 4

Functions: breaks down bone to regulate blood calcium

Hormone: secretes parathormone

Location: embedded in the thyroid

Adrenal Glands Functions: raises heart rate

increases breathing

increases blood sugar level

dilates blood vessels

Secretion: adrenaline

Location: on top of the two kidneys

Pineal Gland Function: modulates the wake/sleep

patterns

modulates photoperiodic (seasonal) functions

Secretion: melatonin

Location: near the center of the brain

Pancreas Functions: controls blood sugar breaks down carbohydrates, proteins, and fats

Secretions: insulin glucagon hormones that control the blood sugar in the body

Location: behind the stomach side of the small intestine

Pancreas Secretions Insulin allows glucose to enter cells

LOWERS blood glucose levels

Glucagon stimulates liver to make glucose

RAISES blood glucose levels

Islets of Langerhans Two cell types: Alpha ( ) cells

produces glucagon

Beta ( ) cells produce insulin

Diabetes Under-secretion

of insulin

High blood sugar

liver

pancreas

liver

Regulation of Blood Sugar

blood sugar level (90mg/100ml)

insulin

body cells take up sugar from blood

liver stores sugar

reduces appetite

glucagon

pancreas

liver releases sugar

triggers hunger

high

low

Thymus Function: controls the immune system

development of T-lymphocytes

Secretion: Thymosin

Location: thorax

anterior mediastinum

Ovaries Two main hormones: Estrogen

create female secondary sex characteristics

Progesterone

thickens the uterus lining every month

Testes One main hormone: Testosterone (an

androgen)

affects the secondary sex characteristics in men

Hirsutism Caused by an increase in testosterone

secretion

Aging Causes few functional changes

Decline in concentration of: growth hormone

reproductive hormones