Download File - Biology with Radjewski

Endocrine System
Chapter 30
AP Biology 2012
Endocrine System
• Consists of cells that produce and release
chemical signals called hormones.
Endocrine vs. Exocrine
Endocrine Signals
• Secrete substances into the
extracellular fluid
• Done by endocrine cells or
secretory organs called
endocrine glands (testes,
thyroid)
• Example; Signaling
molecules
Exocrine Signals
• Secrete substances into a
duct or internal body cavity
that communicates with the
external world
• Example: saliva, sweat
Hormones
• “long distance” endocrine signals that are
released into the bloodstream and circulate
through the entire body
• 3 chemical groups
– Peptide and protein hormones
– Steroid hormones
– Amine hormones
Peptide and protein hormones
• Large
• Water soluble – therefore easily transported
in the blood
• Packaged in vesicles and released by
exocytosis
• Most hormones are this type
• Examples: insulin and growth hormone
Steroid Hormones
• Made from cholesterol (look similar too!)
• Lipid soluble
• Do not dissolve well in blood plasma so they
are bound to carrier proteins for transport in
the blood
• Found inside target cells
• Example: aldosteroids, cortisol, testosterone
Amine hormones
• Small molecules
• Made from single amino acids
• Could be polar or nonpolar depending on the
R group of the amino acid it was synthesized
from
• Example: Tyrosine  epinephrine and
thyroxine
30.2 Review
That same
hormone could
cause very
different
responses in
different types of
cells
Fight or Flight Response
• Rapid physiological
response to sudden
danger or highly
stressful situations
• Involves epinephrine
(adrenaline) and
norepinephrine
(noradrenaline)
What’s really happening
• Epinephrine and norepinephrine bind to a set
of adrenergic receptors (G proteins!)
• 2 categories
–Alpha
–Beta
Have different affinities
for ephinephrine and
norepinephrine!
Adrenergic Receptors
Alpha
• It causes blood vessels in
the skin to constrict, causing
cold hands and feet
• Shut off the secretion of
digestive enzymes and
decrease blood flow
through the gut (digesting
lunch waits)
Beta
• In heart cells, it causes a faster
and stronger heartbeat (thus
pumping more blood)
• Cause arterioles in skeletal
muscles to enlarge so
increased blood flow goes
there enabling you to run
• Breakdown of glycogen in liver
for quick energy!
• Breakdown of fats to yield
fatty acids – another source of
energy!!
Hormone receptors are regulated
• Downregulation – makes the cells less
sensitive to the hormone, causing cells to
ignore the excess hormone
– Example in diabetes
• High levels of insulin downregulates the production of
insulin receptors in body
Hormone receptors are regulated
• upregulation – occurs if hormone secretion is
chronically low; cell makes more receptor for
that hormone
– Example in high blood pressure
• People who are regular medication (beta blockers)
• Let’s say they go off the medication suddenly, the
effects of the receptors are amplified, resulting in
heightened anxiety and blood pressure
• Explains why dosages for medications are carefully
supervised. 
30.3
• Nervous system and Endocrine System are
linked.
• This is done by the Pituitary Gland!
Pituitary Gland
• Endocrine gland
• Attached to a region of the brain called the
hypothalamus
• Has 2 parts
– Anterior Pituitary
– Posterior Pituitary
Anterior Pituitary
• Releases 4 tropic hormones
1.
2.
3.
4.
» Hormones that direct and control the activities of other
endocrine glands
TSH – thyroid stimulating hormone
LH – luteinizing hormone
FSH – follicle stimulating hormone
ACTH – adrenocorticotropic hormone
• Produces peptide hormones
– Prolactin (stimulates milk production)
– Growth hormone (promotes growth)
GIGANTISM
•
Overproduction causes
•
Underproduction causes pituitary dwarfish
Posterior Pituitary
• Releases 2 neurohormones
– ADH
• Increases amount of water conserved by the kidneys
• When high, kidneys produce little volume of highly
concentrated urine
• When low, kidneys produce large volume of dilute urine
– Oxytocin
• Stimulates uterine contractions during birth
• Stimulates flow of milk from mother’s breasts
• Promotes pair bonding and trust; “cuddle hormone”
Negative Feedback Loop
• Corticotropin-releasing hormone (CRH) from
hypothalamus stimulates release of
adrenocorticotropic hormone (ACTH) from
anterior pituitary, which in turn stimulates
release of hormone cortisol from adrenal
glands.
• Once cortisol is released, it circulates thru
body, where it directly inhibits further release
of both CRH and ACTH
• This maintains a constant level of cortisol
30.4
MAMMAL HORMONES
Thyroid Glands
• Wrap around trachea
(windpipe)
• Produce two
hormones
– Thyroxine
– Calcitonin
Thyroxine
• Amine hormone made from amino acid
tyrosine
• Known as T4 – for 4 iodine atoms (T3 is a
nearly identical hormone)
• Raises metabolic rate
• Lipid soluble
• Critical during growth and development
• Insufficient amount during growth results in
physical and mental retardation - cretinism
Thyroxine continued…
• Levels are controlled by hypothalamus and
anterior pituitary
• Hypothalamus releases thyrotropin-releasing
hormone (TRH) which stimulates the anterior
pituitary to release thyroid-stimulating
hormone (TSH) which stimulates thyroid gland
to produce and release thyroxine
• Regulated by a negative feedback loop (like
cortisol)
Goiters
• Is an enlarged
thyroid gland
associated with
– Hyperthyroidism
(too much
thyroxine)
– Hypothyroidism
(too little
thyroxine)
Hyperthyroidism
• Caused by an antibody binding to and
activating TSH receptors, causing uncontrolled
production and release of thyroxine
• Symptoms:
– High metabolic rate
– Nervous and jumpy
– Hot
– Eyes bulge due to buildup of fat behind eye
Hypothyroidism
• Caused by a lack of circulating thyroxine to
turn off TSH production
• Caused by lack of iodine in diet
• Symptoms:
– Low metabolism
– Intolerance of cold
– Sluggish
• Greatly reduced by widespread use of iodized
table salt
Homeostasis of Calcium is VITAL!!
• Why?
– trigger
neurotransmitter
release
– Muscle contraction
Calcium levels
Too little Ca
• Muscle spasms
• Seizures
Too much Ca
• Nervous system to be
depressed
• Muscles and heart to
weaken or stop
99% of Calcium is in bone
1% in cells – so this tiny pool of Ca must be maintained!!
3 Mechanisms the body does to
maintain Ca levels
1. Deposition or resorption of bone
2. Excretion or retention of calcium by kidneys
3. Absorption of Calcium from digestive tract
Calcitonin
• Released by thyroid gland
• Lowers the concentration of Ca in the blood by
regulating bone turnover
– Bone is continuously being made (resorption of old bone
and synthesizing new bone)
– Osteoclasts break down bone and release Ca into blood
– Osteoblasts take up Ca and put it in new bone
• Decreases activity of osteoclasts
• Does not play major role in adults, but does in
younger actively growing individuals
Calcitriol
• Made from Vitamin D in the liver and kidneys
– Vitamin D is obtained from the sun (UV waves in
sunlight convert cholesterol into vitamin D)
– Otherwise Vitamin D must be obtained from diet
• Hormone that stimulates the cells of the
digestive tract to absorb calcium from
ingested food
Parathyroid Hormone
• Most important for homeostasis
• Glands located to the rear of the thyroid
• Synthesis is triggered when blood calcium fall
below set point
• Increases concentration of calcium 3 ways
1. Stimulates bone turnover activities of
osteoclasts and osteoblasts
2. Stimulates kidney to reabsorb Calcium
3. Increases body absorption of calcium from food
by activitating the synthesis of calcitriol from
vitamin D
Adrenal Glands
• Sit above the kidneys
• 2 of them
• Has a core, called the adrenal medulla, which
produces epinephrine and norepinephrine
– This release is under control of the nervous
system
– Both hormones increase heart rate and bp
– Cause fat and liver cells to release metabolic fuel
Arenal Cortex
•Surrounds the adrenal
medulla
•Produces 2 corticosteroid
hormones
1. Mineralocorticoids
2. Glucocorticoids
Mineralocorticoids
•Increase salt and water
balance of the extracellular
fluid
•Example: aldosterone –
stimulates the kidneys to
conserve sodium and
excrete potassium
Glucocorticoids
•Increase blood glucose concentrations and
affect macromolecule metabolism
•Example: cortisol – critical for mediating long
term metabolic responses to stress
Gonads
• Male – testes; Female – Ovaries
• Both produce hormones as well as the
gametes (sperm and egg)
• Male hormones produced are called
androgens, Example: testosterone
• Female hormones produced are estrogen and
progesterone
• ** Both sexes produce both testosterone and
estrogen
Sexual Differentiation
• Y chromosome – embryonic glands begin
producing testosterone in 7th week of
development and a peptide hormone called
MIS (Mullerian-inhibiting substance)
• Testosterone causes testes and ducts develop
and MIS induces apoptosis of cells of female
reproductive ducts, so they disappear
• So androgens are required for male
development in humans
Puberty
• Time of sexual maturation and dramatic
physical transformation around age 12-13
• Controlled by gonadotropins
– Contain two hormones, LH (luteinizing hormone)
and FSH (follicle-stimulating hormone)
– Under control of a hypothalamic neurohormone
called gonadotropin-releasing hormone GnRH
• Before puberty, the hypothalamus is
producing very low levels of GnRH
Puberty Continued…
• Initiated by a reduction in the sensitivity of
GnRH producing cells by negative feedback
• The reduced sensitivity overcomes the
negative feedback and so GnRH release
increases, stimulating production of
gonadotropins and hence production of sex
steroid hormones
Puberty Continued…
• In females, increased levels of LH stimulates
the ovaries to increase estrogen production
– This initiates development of enlarged breasts,
vagina and uterus, broadened hips, increased fat,
pubic hair, and menstrual cycle
• In males, increased levels of LH stimulates the
testes to produce testosterone
– This initiates the voice to deepen, facial and body
hair, muscle mass increase, testes and penis grow
larger