Coordination and RegulationThe endocrine system

homeo = same; stasis = standing Homeostasis is the term we use to describe the

constant state of the internal environment. Homeostasis is a state of

balance in the body. The processes and activities

that help to maintain homeostasis are referred to as homeostatic mechanisms.

Definition of Homeostasis

Set point

You are exposed to ever changing environmental conditions. For example, you may walk out of an air conditioned room into the hot summer sun.

However the cells in your body work best when their surroundings are kept constant. Your body has many mechanisms that keep the cells surroundings constant even though your external environment is changing. This is homeostasis.

Homeostasis is very important because when it fails you become ill and may die.  

Homeostasis

Biochemical processes are vital to life and occur efficiently only within a limited temperature range and at a specific pH.

The body must have good internal communication, using the endocrine and nervous systems, to maintain homeostasis.

Maintaining Homeostasis

Linkage system

Effector

Reponse

Sensor

Stimulus

Negative feedbackOccurs when feedback (from sensory organ to CNS) results in a reversal of the direction of change.

Negative feedback tends to stabilise a system, correcting deviations from the set point.

Negative Feedback

The endocrine system

Made up of endocrine glands that release chemical messengers called HORMONES right into the bloodstream.

Allow for the maintenance of the internal environment in the body, or internal homeostasis.

The endocrine system

The endocrine glands include the hypothalamus, pituitary, thyroid, parathyroid, adrenal, thymus, and pancreas.

Functions of Endocrine Glands

The pituitary gland communicates with the hypothalamus to control many body activities.

Functions of Endocrine Glands

What Are Hormones?

Hormones are chemical substances created by the body that control numerous body functions. They actually act as "messengers" to coordinate functions of various body parts. Most hormones are proteins consisting of amino acid chains. Functions controlled by hormones include:

• activities of entire organs• growth and development• Reproduction• sexual characteristics• usage and storage of energy• levels of fluid, salt and sugar in the blood

Endocrine Glands are found throughout the body

Hypothalamus and Pituitary are in the brain

Parathyroids are in the neck and sit on the Thyroid

Adrenals sit on the kidneys

Pancreas is in the abdomen

Testes are in the scrotum and Ovaries are in the hip area

Through negative feedback, when the amount of a particular hormone in the blood reaches a certain level, the endocrine system sends signals that stop the release of that hormone.

Negative Feedback

An example...

Your cells also need an exact level of glucose in the blood.

Excess glucose gets turned into glycogen in the liver

This is regulated by 2 hormones (chemicals) from the pancreas called:

InsulinGlucagon

Controlling Glucose levels

If there is too much glucose in the blood, Insulin converts some of it to glycogen

Glycogen

Insulin

Glucose in the blood

If there is not enough glucose in the blood, Glucagon converts some glycogen into glucose.

Glycogen

Glucagon

Glucose in the blood

Some people do not produce enough insulin.

When they eat food, the glucose levels in their blood cannot be reduced.

This condition is known as DIABETES. Diabetics sometimes have to inject insulin

into their blood. They have to be careful of their diet.

Diabetes

Time

Glucose Concentration

Meal eaten

Insulin is produced and glucose levels fall to normal again.

Glucose levels rise after a meal.

Normal

Time

Glucose Concentration

Meal eaten

Insulin is not produced so glucose levels stay high

Glucose levels rise after a meal.

Diabetic

The glucose in the blood increases.

Glycogen

Insulin

Glucose in the blood

But there is no insulin to convert it into glycogen.

Glucose concentration rises to dangerous levels.