Transcript The Endocrine System

The Endocrine System
Anatomy & Physiology
The Endocrine System


The “other” great controlling system
of the body
What’s the first?
Endocrine vs. Nervous

Endocrine



Slower
Uses hormones
Responses are
continuous or longterm

Nervous



Faster
Uses nervous
impulses
Responses are
immediate
What Are Hormones?

Chemical substances, secreted by
cells into extracellular fluids, that
regulate the metabolic activity of
other cells of the body
Target Cells/Hormones


The specific cells or organs a
hormone is meant to affect
Each hormone must have a receptor
protein present on a cell’s plasma
membrane in order to work
Types of Hormones


Non-steroidal or amino-acid
based: made from proteins,
peptides or amines)
Steroidal: made from cholesterol

Includes all sex hormones and
hormones made in adrenal cortex
How Do They Work?

First Mechanism
1.
Direct Gene Activation
a. Steroid hormones diffuse through plasma
membrane (why?)
b. Enters nucleus
c. Binds to a specific receptor inside
nucleus—hormone-receptor complex
(HRC)
d. HRC binds to cell’s DNA—
causes transcription of mRNA
e. mRNA translated in cytoplasm—makes
new proteins
How Do They Work?

Second Mechanism
Second Messenger System
a. Non-steroidal hormones bind to
receptors on plasma membrane (why?)
b. Reactions go off inside cell activating an
enzyme
c. Enzyme sets off reactions to create a
second messenger (cAMP)
d. Second messenger instills changes in cell
2.
Controlling Hormone Release

Negative Feedback Mechanisms



Hormone released triggered by internal
or external stimuli
Rising hormone levels in blood inhibits
further release
Blood levels of hormones vary within a
very narrow range
Controlling Hormone Release
Hormone Stimuli
1. Humoral: changing blood levels of
different ions and nutrients
example: PTH in response to calcium
levels
2. Hormonal: endocrine organs
stimulated to work due to presence of
other hormones
example: TSH stimulates thyroid

Controlling Hormone Release
3. Neural: nerve fibers stimulate
hormone release
example: epinephrine and norepinephrine
Major Endocrine Organs







Pituitary gland (anterior &
posterior)
Pineal Gland (body)
Thymus
Thyroid & Parathyroid
Pancreas
Adrenal glands (cortex & medulla)
Gonads (testes or ovaries)
Anterior Pituitary Gland

Secretes 6 Hormones


Found at base of
hypothalamus
“Master Endocrine
Gland”



Actually regulated
by hypothalamus
All non-steroidal
All respond to
hormonal stimuli
from hypothalamus
http://www.becomehealthynow.com/images/o
rgans/nervous/glakgar_pit_hypothalamus.jpg
Anterior Pituitary Gland
1. Growth Hormone

Target cells: skeletal muscles & bones

Function:




to stimulate growth of target cells
Cause fat metabolism, sparing glucose
Hyposecretion disorder: dwarfism
Hypersecretion: kids = gigantism
adults = acromegaly
Anterior Pituitary Gland
2. Prolactin
 Target cells: the breasts of females
 Function:


stimulates & maintains milk production
after birth
No associated disorders
Anterior Pituitary Gland
3. Adrenocorticotropic
Hormone (ACTH)
Target cells: adrenal
cortex
Function: regulates
release of
hormones
4. ThyroidStimulating
Hormone (TSH)
Target cells: thyroid
Function: regulates
growth & activity
of gland
Anterior Pituitary Gland
5. Follicle-Stimulating Hormone
(FSH)
 Target cells: gonads
 Functions:



Females: stimulates follicle
development
Males: stimulates sperm development
Hyposecretion: sterility
Anterior Pituitary Gland
6. Luteinizing Hormone (LH)
 Target cells: gonads
 Functions:



Females: triggers ovulation
Males: stimulates testosterone
production
Hyposecretion: sterility
Posterior Pituitary Gland
Stores 2 hormones made by
hypothalamus
 Non-steroidal hormones
1. Oxytocin
Target cells: uterus & breasts of
pregnant women
Functions: stimulates contractions &
breast milk ejection

Posterior Pituitary Gland
2. Antidiuretic Hormone (ADH)
 Target Cells: kidneys
 Functions: causes kidneys to
reabsorb water—decrease urine
volume/ increases blood volume
 Hyposecretion: diabetes insipidus
 ** diuretics inhibit ADH
Thyroid Gland
Located at base of throat
 Makes 2 hormones both nonsteroidal
1. Calcitonin
 Target cells: bones
 Function: causes absorption of
calcium by bones


decreases blood calcium levels
Thyroid Gland
2. Thyroid Hormone (thyroxine, T4, & triiodothyronine, T3)
requires iodine
 Target cells: all body cells
 Function: controls rate of glucose
metabolism



Needed for normal tissue growth &
development
Hyposecretion: Kids: cretinism, adults:
myxedema
Hypersecretion: graves disease
Parathyroid Gland
Tiny masses of tissue on posterior
thyroid
1. Parathyroid Hormone (PTH)

Target cells: bone cells, kidneys &
intestines

Function: regulates blood calcium levels




Causes release of calcium from bones
Hyposecretion: tetany
Hypersecretion: massive bone loss
Adrenal Glands




2 bean shaped glands
Sit on top of kidneys
Steroidal hormones
2 parts:


Adrenal cortex: outside layer
Adrenal medulla: center
Adrenal Cortex
1. Corticosteroids:
mineralocorticoids, glucocorticoids,
sex hormones
A. Mineralocorticoids: aldosterone
 Target cells: kidneys
 Function: Regulates water &
electrolyte balance

Causes uptake of sodium (and water),
release of potassium by kidneys
Adrenal Cortex
B. Glucocorticoids: cortisol and
cortisone
 Target cells: all body cells
 Function: promote normal cell
metabolism


Assist body in coping with long-term
stress—increasing blood glucose
Can decrease edema and pain
Adrenal Cortex
C. Sex Hormones: aka androgens;
released in both males & females all
through life
 Hyposecretion of any adrenal cortex
hormone: addison’s disease
 Hypersecretion: cushing’s
syndrome
Adrenal Medulla
Located in center of adrenal gland
 Stimulated by sympathetic nervous
system
1. Catecholamines: epinephrine &
norepinephrine
 Target cells: all body cells
 Function: assists body in coping with
short-term stressors



increase glucose levels, increase breathing rate
“fight or flight” response
Pancreas


Located close to stomach in
abdominal cavity
Part exocrine gland/ part endocrine
gland

Pancreatic Islets—endocrine portion
Pancreas
1. Insulin:
stimulated by high
glucose
 Target cells: all
body cells
 Function: allows
for uptake of
insulin by cells
 Hyposecretion:
diabetes mellitus
2. Glucagon:
stimulated by low
glucose
 Target cells: liver
 Functions: calls
for breakdown of
glucagon to
glucose
Pineal Gland
aka pineal body

Small, cone-shaped

Located in diencephalon of brain
1. Melatonin

Target cells: ??

Function: day-night cycle




Peak levels occur at night– drowsiness
Low levels around noon—alertness
“Biological Clock” ???
Thymus
Located in upper thorax, posterior
to sternum
 Large in infants and kids—decreases
and converts to fat in adults
1. Thymosin
 Target cells: t-cells of immune
system
 Function: assists in maturation of tcells

Gonads
Females: ovaries
 Males: testicles
A. Ovaries
1. Estrogen
 Target cells: female sex organs
 Function: stimulate development of
secondary sex characteristics



Assists in preparing uterus for fertilized egg
Help maintain pregnancy and produce milk
Gonads
2. Progesterone
 Target cells: uterus
 Function: assists in preparation of
uterus for fertilized egg


During pregnancy—quiets contractions
of uterine muscle
Hyposecretion of either hormone—
inability to conceive and bear
children
Gonads
B. Testes
1. Testosterone (made by interstitial
cells)

Target cells: male sex organs

Function: development of male
secondary sex characteristics




Growth and development of sex organs
Male sex drive
Production of sperm
Hyposecretion: sterility