Transcript ENDOCRINE SYSTEM - Grade 12 Biology

ENDOCRINE SYSTEM
Series of glands that produce hormones to
help maintain homeostasis.
Hormones: Chemical regulators that affect other
parts of the body.
Insulin
Growth Hormone
Gastrin
Some glands produce one hormone, some
produce many kinds and even other chemicals.
Levels of hormones vary throughout the day.
COORDINATION
The nervous system and the endocrine system
work together to allow the body to function.
Nervous System --> SHORT TERM corrections
Endocrine System --> LONG TERM stability
HORMONES
To be susceptible to the effects of a hormone, a
cell must have a specific receptor .
Two types of hormones:
Steroid hormones: made from cholesterol, complex
ring structures, fat soluble
Sex hormones, cortisol
Protein hormones: amino acid chains
Insulin, growth hormone
Mechanism of Action
Steroid Hormones:
hormones diffuse out of blood stream and into the
target cells
combine with receptor molecules in cytoplasm
hormone-receptor complex diffuses into nucleus
attaches to chromosomes and activates a gene,
initiating transcription and protein synthesis.
Mechanism of Action
PROTEIN Hormones:
hormones diffuse out of blood stream
attach to receptors on the cell membranes of target
cells
the receptor-hormone complex activates the
production of adenylyl cyclase, an enzyme that
catalyzes the conversion of ATP into cyclic AMP
(cAMP).
The cAMP is a messenger that activates various
enzymes inside the cell to begin their normal functions.
(R-H complex activates an enzyme that converts ATP
into cAMP, cAMP activates enzymes inside the cell to
begin functioning)
PITUITARY GLAND
This is known as the master
gland because it controls a
lot of other endocrine glands.
A small sac connected to the
hypothalamus.
Pituitary gland stores
hormones while the
hypothalamus stimulates it to
release them.
PITUITARY GLAND
The pituitary gland has
two lobes:
The posterior lobe stores
and releases hormones
produced by the
hypothalamus (ex. ADH,
oxytocin)
The anterior lobe
produces and stores its
own hormones (ex. TSH,
prolactin)
PANCREAS
pancreas cells produce:
Digestive Enzymes
Hormones: Insulin and
Glucagon
The hormones are produced in
structures called the Islets of
Langerhans (discovered by
Paul Langerhans of Germany).
approx. 2000 islets in the
pancreas
each islet has 2 types of cells
INSULIN
produced in the Beta cells
released when blood sugar is
high (after a meal)
Stimulates uptake of glucose by
making muscles, liver and other
organs more permeable to
glucose so it can be stored
Liver converts glucose to
glycogen
Result: Decreases blood sugar
level.
GLUCAGON
produced in the alpha cells
released when blood sugar levels
are low (fasting)
Stimulates release of glucose by
organs into blood stream
liver breaks down glycogen
into glucose and releases it
Result: Increase blood sugar level
http://www.endocrineweb.com/insulin.htm
INSULIN
RELEASED
GLUCAGON
RELEASED
http://www.holistic-physician.com/articles/brochbs.htm
DIABETES
Chronic disease caused by insufficient production of
insulin
Type I (juvenile) (insulin dependent) - 10%
early degeneration of beta cells
Type II (adult) (non-insulin dependent, NIDDM) – 90%
decreased insulin production or ineffective use of
insulin produced.
Gestational
temporary condition of pregnancy that increases
risk of diabetes in both mom and child
Banting and Best – isolated insulin for treatment
p 383 #2-5
METABOLISM
Thyroid Gland is located
in front of the trachea.
It produces hormones:
Thyroxine (T4)
Calcitonin
Triiodothyronine (T3)
T4 and T3 regulate body
metabolism and growth
and differentiation of
tissues
METABOLISM
Parathyroid Gland
Parathyroid hormone
Pituitary Gland
Growth hormone
(somatotropin)
THYROID HORMONES
Thyroxine helps our body oxidize sugars and
nutrients at a faster rate.
All the energy of glucose is transferred to heat and
ATP, and ATP is consumed during activity, therefore
there is no weight gain.
Hypothyroidism: low thyroid secretions
glucose is not oxidized as quickly, and excess
glucose is converted to glycogen and stored.
once glycogen stores are filled, excess sugar is
stored as fat.
REGULATION of METABOLISM
Metabolic rate decreases
 hypothalamus sends thyroid
releasing hormone (TRH) to
the pituitary
pituitary releases thyroid
stimulating hormone (TSH)
TSH acts on thyroid to
release thyroxine.
thyroxine raises metabolism
by increasing sugar usage by
body tissues
thyroxine levels feedback on
TRH release

Metabolic rate decreases
Hypothalamus
inhibits
TRH
Pituitary
TSH
Thyroid
Thyroxine
Increase metabolism
GOITER
Lack of iodine for T4 and T3
Less T4 and T3 present
TSH produced continuously
Overstimulated thyroid enlarges
Other Metabolic Hormones
Calcitonin
Calcium absorption (bone formation)
Parathyroid Hormone
Calcium release (from bones, reabsorption at
kidneys, intestines)
Growth Hormone (somatotropin)
Dwarfism, gigantism, acromegaly
Protein synthesis
Breakdown of fats
p 387 #3-7
STRESS
Both the endocrine and nervous system make adjustments to
stress to enable the body to cope.
Nervous Response: quick, sudden.
Increase heart rate
Diversion of blood to needed muscles
Endocrine Response: slow, prolonged
More glucose available due to
increased Epinephrine (increases blood sugar levels,
heart rate and breathing rate)
increased Cortisol (converts proteins to glucose)
increased Glucagon (glycogen to glucose)
Decreased insulin* (decrease glycogen formation)
Lots of O2 and glucose = more energy
STRESS and FLUID LEVELS
Renin-Angiotesin-Aldosterone pathway
(Nervous)
and ADH (Endocrine)
both are active to increase reabsorption to help
maintain body fluid levels.
ADRENAL GLANDS
located above each
kidney
made up of a cortex
surrounding a
medulla
the cortex is regulated
by hormones
the medulla is
regulated by nervous
stimulation
MEDULLA
produces the hormones: Epinephrine and
Norepinephrine
“Fight or Flight”
In times of stress, EPI and NOREPI are released to
Increase blood glucose levels by stimulating the
break down of glycogen
increase heart rate, breathing rate, metabolism
dilate blood vessels and iris of eye
CORTEX
produces hormones known as Glucocorticoids
Ex. Cortisol
also released in times of stress, cortisol increases
amino acids (used by liver to convert into glucose,
excess used to build proteins)
inhibits glucose uptake in many tissues (also helps
increase blood levels).
LONG TERM STRESS
Hypothalamus
Pituitary
(Negative feedback)
ACTH
Adrenal cortex
Glucocorticoids
Mineralocorticoids
Cortisol
Aldosterone
hypothalamus sends a releasing hormone, ACTH
(adrenocorticotropic hormone), into the blood
ACTH stimulates adrenal cortex to release glucocorticoids and
mineralocorticoids (hormones).
cortisol - (see notes above)
aldosterone – increase Na+ and H O reabsorption in kidneys
2
Problems with Prolonged Stress
High blood sugar
High blood pressure
Increased water loss
Rupture of vessels / clotting
Increased Heart Rate (heart attack)
Hmwk p 383 #1,6-9; p 392 #1-4, 6*, 8*