HOMEOSTASIS“Keeping The Status

Quo”

A set of processes used to maintain a balanced body environment Blood pressure at 120/80 Body temperature at 37oC Blood pH at 7.4 Glucose concentration 100 mg per mL Heartbeat at 50 – 100 beats per minute

HOMEOSTASIS

There are TWO kinds of mechanisms used in homeostasis: NEGATIVE FEEDBACK: a

mechanism used to CORRECT change

POSITIVE FEEDBACK: a mechanism used to AMPLIFY change

HOMEOSTASIS

NEGATIVE FEEDBACK

TEMPERATURE CONTROL

COLD Shivering VASOCONSTRICTION:

blood vessels constrict (tighten) and move away from the surface to keep the core organs (heart, brain, liver, etc.) warm

Goosebumps raise the hair up to trap warm air to the surface of the skin

HOT Sweating VASODILATION:

blood vessels in the body dilate (widen) and rise to the surface of the skin to radiate off heat.

When we stop breathing: Carbon dioxide levels increase This produces carbonic acid This lowers the pH of the blood Receptors detect the change in pH The brain sends a message to the diaphragm

and intercostal muscles to contract Heart rate also increases to deliver oxygen

and remove carbon dioxide quickly

BREATHING CONTROL

GLUCOSE CONTROL

AFTER A MEAL… Blood glucose levels

increase Specialized receptor

cells signal the release of insulin from the pancreas

Insulin is released which promotes the uptake of glucose from blood to restore normal levels

WHEN YOU ARE STARVING…

Blood glucose levels decrease

Receptor cells signal the release of glucagon from the pancreas

Glucose is released from energy reserves in the liver

Associated with disease or addiction EXAMPLE: High Blood Pressure

High blood pressure leads to damage of the walls of the arteries

The arteries develop scar tissue Cholesterol sticks to the scar tissue with

causes the diameter of the artery to shrink The flow of blood decreases, which increases

blood pressure

POSITIVE FEEDBACK

ENDOCRINE SYSTEM

An organ system comprised of: HORMONES:

chemical messengers GLANDS:

specialized group of cells that deliver hormones

ENDOCRINE GLANDS

EXOCRINE GLANDS

Hormones are released through DUCTS

ENDOCRINE GLANDS

Hormones are released directly into the blood vessels

No ducts

HYPOTHALAMUS: monitors the body and regulates the pituitary gland

PITUITARY: produces hormones to regulate the endocrine system

THYROID: controls metabolism with the hormone THYROXIN

PANCREAS: regulates blood sugar with the hormones INSULIN and GLUCAGON

ENDOCRINE ORGANS

ADRENALS: regulates stress CORTISOL: hormone released

during long term stress ADRENALINE: hormone released

during short term stress or the “flight or fight” stress

ENDOCRINE ORGANS

OVARIES AND TESTES: produce and use the same hormones FSH and LH

ENDOCRINE ORGANS

FEMALES MALES

LH and FSH are involved in the menstrual cycle

LH: involved in testosterone productionFSH: involved in sperm production