Endocrine System

By:Sarah

Shelby&

Sierra

HELP

FUL P

REFIX

ES

AN

D

SU

FFIXES

-crin (to secrete)dieuret-(to pass urine)endo-(within)exo-(outside)Hyper-(above)Hypo-(below)Para-(beside)Toc-(birth)

Sarah

Function of the System

Endocrine Function

Helps regulate conditions within the body to maintain homeostasis

Secretes hormones in the body’s internal environment

Works with the nervous system so that different parts of the body can communicate with each other and adjust to changing incoming signals

Exocrine Function Secrete substances

outside the body through tubes or ducts; leading to the surface

En

docrin

e v

s. E

xocrin

e

endocrin

eexo

crine

Secrete within the body EX: pituitary gland

Secrete to the outside of the body EX: sweat gland

HORMONES

Hormones are substance(s) that are secreted by endocrine glands and transported into the blood

Hormones influence their target cells during stimulation

A hormone alters the metabolism of the target cells

*Paracrine: secretions affect only neighboring cells

*Autocrine: secretions affect only secreting cell

1

Control of Hormone Secretion

Hypothalamus regulates anterior pituitary gland’s release of hormones that stimulate other endocrine glands to secrete hormones.

Hypothalamus receives information about the internal environment from neural connections and cerebrospinal fluid

Nervous system stimulates glands directly

A group of glands responds directly to changes in the composition of the internal environment

2

Gen

era

l ch

ara

cte

ristic

s

Only target cells can respond to a hormone, they have a specific receptor that other

cells lack such as proteins or glycoprotein (these can bind with a hormone)

Endocrine glands and hormones

Endocrine and nervous system “oversee” the cell- to-cell communication through chemical signals that bind receptors to molecules

Help maintain metabolic processes

Control rate of reactions Help transport substances

across membranes Helps with water balance Helps with electrolyte balance

Steroids and Nonsteroids

Sierra

MOST HORMONES ARE STEROIDS OR

STEROID-LIKE SUBSTANCES WHICH

ARE SYNTHESIZED FROM

CHOLESTEROLAMINES

PEPTIDESPROTEINS

OR GLYCOPROTEIN WHICH IS

SYNTHESIZED FROM AMINO ACIDS.

Hormones can produce change in the target cell, even at low concentrations.

Steroids are carried through the bloodstream and are weakly bound to plasma proteins, so they can be efficiently released to their target cells.

3

Steroid hormones are insoluble in water but soluble in lipids

When a steroid hormone enters a target cell:1. The steroid hormone diffuses through the cell

membrane2. Then binds to a specific protein molecule-the

receptor for the hormone3. The resulting hormone-receptor complex binds in

the nucleus to particular regions of the target cell’s DNA and copies genes into the mRNA molecules

4. mRNA molecules leave the nucleus and enter cytoplasm

5. mRNA molecules and the ribosome direct the synthesis of specific proteins

NONSTEROID HORMONES

INCLUDEAMINES

PEPTIDESAND PROTEINS

WHICH USUALLY BIND RECEPTORS TO TARGET CELL

MEMBRANES

The receptors are protein molecules that have a binding and activity siteMessages are sent to the target cell by joining the binding site of it’s receptor (hormones sending the message)This stimulates the receptor’s activity site to interact with other membrane proteins

Receptor binding can alter functions of enzymes or

membrane transport mechanisms, which changes

concentration of other cellular components

Nonsteroid hormones

The hormone

triggerin

g this

is

First messenger

Nonsteroid hormones

Biochemicals in cells that

produce changes in response to

hormone building

Is called Second messenger

The process of chemical

communication from the outside to the inside of the cell

Is calledSignal

transduction

The second messenger associated with one group

of hormones is cyclic adenosine monophosphate

(cyclic AMP)

It works like this

Hormone binds to

its receptor

Resulting hormone-receptor activates

a G protein

G protein activates a membrane protein called adenylate cyclase

Adenylate cyclase catalyses the

circulation of ATP in cytoplasm into

cAMP

cAMP activates protein kinases enzymes that

transfer phosphate groups from ATP to

their substrate molecules(specific

proteins)

4

prostaglandins

Group of biochemicals that regulate cells

Lipids from a fatty acid in cell membranes called arachidonic acid

Usually only affect the organs where they are produced

Influence movements of sodium ions and water molecules in the kidneys

Helps regulate blood pressure

Produced in many cells

5

NEG

ATIV

E FE

ED

BA

CK

SYS

TEM

Hormone level rises in the blood, the hormone does its effect.

The negative feedback inhibits the system and the hormone secretion decreases.

As the hormone level decreases, the effects of the hormone stop.

When inhibition of the system is lifted, secretion of the hormone takes place once again.

Negative feedback systems keeps hormone levels in the bloodstream relatively stable.6

Major endocrine glands!!!!

Shelby

PIT

UITA

RY G

LAN

D

Attached to the base of the brain and has an anterior and posterior lobe.

Releases hormones from the hypothalamus, which controls the secretions of the anterior lobe.

Posterior lobe releases hormones into the bloodstream in response to nerve impulses from hypothalamus.

7

Anterior Pituitary hormones

Growth hormone(GH): stimulates body cells to grow and reproduce, and speeds up rate at which cells use carbohydrates and fats

Prolactin(PRL): promotes milk production following the birth of an infant

Thyroid-stimulating hormone(TSH): controls secretion of hormones from thyroid gland

Thyrotropin-releasing hormone(TRH): from the hypothalamus regulates release of TSH

Adrenocorticotropic hormone (ACTH): controls secretion of hormones from adrenal cortex

Corticotropin-releasing hormone (CRH): regulates ACTH from the hypothalamus, stress can also increase it’s release

Follicle-stimulating hormone (FSH): gonadotropins affecting male and female gonads

Luteinizing hormone (LH): gonadotropins affecting male and female gonads

8

Posterior Pituitary Hormones

Neurons in the hypothalamus produce antidiuretic hormone and oxytocin

ADH causes kidneys to conserve water Hypothalamus regulates ADH secretion

based on the amount of water in body fluids Oxytocin plays a role in childbirth by

contracting muscles from uterine wall, and forcing milk into ducts from milk glands

Stretching of the uterus in later stages of pregnancy stimulates the release of oxytocin

9

Thyroid Gland

Located below the larynx and consists of

2 lobes

Thyroxin tetraiodothyronin

e

Thyroxin triiodothyronin

e

Cells release energy from carbohydrates,

enhance protein synthesis, and

stimulate breakdown of lipids

These 2 increase the rate at whichThese hormones are

essential for growth

and development

Hypothalamus and pituitary gland control

release of these

10

Thyroid continued…

Extrafollicular cells of thyroid secrete calcitonin

This lowers blood levels of calcium and phosphate ions when they

are too high

Calcitonin increases the rate at

which calcium is stored in

bones and excreted by urine

Calcitonin secretion is regulated by

negative feedback involving blood

concentrations of calcium

Parathyroid GlandLocated on

posterior end of thyroid

Parathyroid hormone(PTH) increases blood

calcium ion concentration and

decreases phosphate ion concentrationPTH stimulates

bone reabsorption by

osteoclasts, releasing

calcium into blood

PTH influences kidneys to conserve calcium

A negative feedback mechanism involving blood

calcium levels regulates release of PTH

*Calcitonin and PTH exert opposite

effects in regulating calcium ion levels in

blood

11

Adrenal glands

Adrenal medulla: secretes epinephrine and norepinephrine into the bloodstream(used in times of “fight or flight”) Adrenal cortex: produces over 30 steroidso Aldosterone: (mineralocorticoid) causes kidneys to

conserve sodium ions and thus water, and excrete potassium ions

o Cortisol: (glucocorticoid) influences metabolism of glucose, protein, and fat in response to conditions that stress the body

o Adrenal sex hormones: released by the gonads and may stimulate early development of reproductive organs

12

PANCREAS: SECRETES

HORMONES AS AN

ENDOCRINE GLAND, AND

DIGESTIVE JUICES TO

DIGESTIVE TRACT AS AN

EXOCRINE GLAND

Posterior to stomach

Has 2 cell types:Alpha cells: secrete glucagon-glucagon increases the blood levels of glucose by stimulating the breakdown of glycogen and conversion of noncarbohydrates into glucose

Beta cells: secrete insulin-insulin decreases the blood levels of glucose by stimulating the liver to form glycogen, increasing protein synthesis, and stimulating adipose cells to store fat

*insulin and glucagon coordinate to maintain a relatively stable blood glucose concentration

13

Other Endocrine GlandsPineal gland: lies near the

upper portion of the thalamus, and secretes

melatonin which is involved in regulation of circadian

rhythms-also linked to the onset of

puberty

Thymus gland: lies between lungs and sternum, secretes

thymosins that affect production of T lymphocytes

ovaries produce estrogen Placenta produces estrogen, progesterone,

and gonadotropin Testes produce testosteroneProduces

atrial natriuretic peptide

Kidney produces

erythropoietin

All pictures from BingAll info from the anatomy book