Regents Biology2009-2010

Endocrine SystemHormones

& Homeostasis

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Homeostasis Homeostasis

maintaining internal balance in the body organism must keep internal conditions

stable even if environment changes also called “dynamic equilibrium”

example: body temperature humans:

too cold = shiver too warm = sweat

lizard: too cold = bask in sun too warm = hide in shade

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Regulation How we maintain homeostasis

nervous system nerve signals control body functions

endocrine system hormones chemical signals control body functions

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Controlling Body Temperature

high

low

nerve signals

sweat

nerve signals

brain

body temperature

shiver brain

dilates surfaceblood vessels

constricts surfaceblood vessels

Nervous System Control Feedback

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Hormones Why are hormones needed?

chemical messages from one body part to cells in other parts of body

communication needed to coordinate whole body

maintaining homeostasis

growth hormones

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Endocrine System Endocrine system releases hormones

glands which secrete (release) chemical signals into blood

chemicals cause changes in other parts of bodygrowth hormonessex hormonesresponse hormonesmetabolism hormonesand more….

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Responding to hormones Lock and key system

hormone fits receptor on “target” cell

targetcell

non-targetcells

secretingcell

can’tread

signal

can’tread

signal

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Glands Pineal

melatonin Pituitary

many hormones: TSH, FSH, ACTH,

Oxytocin, Calcitonin master gland

Thyroid Thyroxine

Adrenal adrenaline

Pancreas insulin, glucagon

Ovary Estrogen progesterone

Testes testosterone

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Pituitary Gland

TSH – thyroid stimulating hormone

ACTH – stimulates adrenal glands

FSH – stimulates the ovaries

Oxytocin – labor contractions

Calcitonin – Calcium metabolism

Releases hormone messengers (do not “do work”)

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ENDOCRINE GLANDS

Thyroid Gland – in neck

Releases Thyroxine which regulates metabolism

Parathyroids – 4 tiny glands behind thyroid

Releases Parahormone regulates Calcium in blood

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Adrenal Gland– on top of kidneys

Releases Adrenaline which allows the body to respond appropriately in times of emergency or stress

“Fight or Flight”

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Pancreas – glands located within the pancreas Releases Insulin which regulates blood sugar

levels

Diabetes – caused by decreased amounts of insulin which leads to increase blood sugar coma death if not medicated

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GONADS – sex glands

Ovaries Releases Estrogen – 2nd degree sex characteristics/ cycle

Releases Progesterone – cycle and maintain pregnancy

Testes

Releases Testosterone – 2nd degree male characteristics and

production of sperm

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Maintaining homeostasis

high

low

hormone 1

lowersbody condition

hormone 2

gland

specific body condition

raisesbody condition

gland

Feedback

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Negative Feedback Response to changed body condition

if body is high or low from normal level signal tells body to make changes that will

bring body back to normal level once body is back

to normal level, signal is turned off

high

hormone 1

lowersbody condition

gland

specific body condition

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liver

pancreas

liver

Regulation of Blood Sugar

blood sugar level(90mg/100ml)

insulin

body cells takeup sugar

from blood

liver storessugar

reducesappetite

glucagon

pancreas

liver releases

sugartriggershunger

high

low

FeedbackEndocrine System Control