Transcript The Endocrine System

The Endocrine System
Anatomy and Physiology
Endocrine System
• Endocrine organs
secrete hormones
directly into body
fluids (blood)
• Hormones are
chemical messengers
that only affect target
cells that have a
special receptor on the
cell surface
Hormones…
• Are of two types:
steroid and nonsteroid,
usually peptide
(protein)
• Steroid hormones may
enter the cell through
the cell membrane, but
nonsteroid hormones
cannot
Nonsteroid hormones
• These hormones, usually proteins, cannot
get through the cell membrane.
• They must attach to a receptor on the
outside of the membrane
• They use a 2nd messenger system to get the
message into the cell, to achieve the desired
response
Pass it on!
2nd messenger system
A chain reaction
Endocrine Glands
Control of Hormones
• Most often controlled
by negative feedback
• This means a gland or
system is sensitive to
the concentration of
the substance it
secretes, or a product
it controls
Control of Hormones
• If high levels of a
hormone or product
are detected, then the
gland is inhibited (shut
off)
• If low levels are
detected, more must
be needed, so the
gland is not inhibited
(allowed to turn on)
Control of Hormones
• What turns on and off
each gland varies
• Some have many steps
involved, like a chain
reaction
Control of Hormones
Control of Hormones
Growth hormone is
controlled by a releasing
and an inhibiting hormone.
Which one is secreted in
greater concentration
determines whether GH is
released or not.
Control of Hormones
Hypothalamus controls Pituitary
Hypothalamus controls Pituitary
Hormones of the Pituitary
Master gland
Growth Hormone
• Stimulates cell growth
and division
• Under-secretion can
be dwarfism, with
correct proportions
and normal mental
development
• Over-secretion can be
gigantism
6’1” normal
male’s hand
Twelve years old: 6’5”
Gigantism
Twelve
year old’s
hand
Hypopituitary Dwarfism
Posterior Pituitary
Vasopressin is
also called
ADH:
antidiruetic
hormone
Thyroid Gland
• Secretes three
hormones
• Thyroxine (T4),
Triiodothyronine (T3)
• Calcitonin
Thyroid Hormones
Grave’s disease
Cretinism
• T3 and T4 control
metabolism
• Undersecretion in
childhood could cause
cretinism; in adults
called myxedema with
sluggishness, obesity
• Oversecretion can be
Grave’s disease
Goiter
• Enlarged thyroid
gland
• Caused by lack of
iodine
• Iodine is required to
make T4, and if not
present, the thyroid
keeps working to the
point of enlargement,
yet cannot make T4
Thyroid Control
• TRH (TRF) from
hypothalamus to
pituitary
• TSH from pituitary to
thyroid
• T3 and T4 (thyroxine)
from thyroid
• Negative feedback
Parathyroid
• Parathyroid gland
secretes parathyroid
hormone (PTH)
• PTH increases blood
calcium and decreases
blood phosphate
• Parathyroid gland can
sense level of calcium
in the blood
Parathyroid
• Osteoblasts are cells that build bone
• Osteoclasts are cells that break down bone to
release calcium
• If calcium is low in the blood, PTH stimulates
osteoclasts
• If calcium is high in the blood, PTH inhibits
osteoclasts
• Controlled by the parathyroid glands, sensing the
amount of blood calcium
Parathyroid
Parathyroid
• Your body sacrifices bone tissue to maintain
correct levels of calcium in the blood.
Thyroid helps with calcium
• The thyroid gland also helps with calcium
regulation
• It secretes calcitonin, which decreases level
of blood calcium by encouraging the kidney
to excrete calcium and inhibiting osteoclasts
• PTH and calcitonin are opposites
Adrenal Hormones
• Adrenal glands on
each kidney
• Inner part is called
medulla
• Outer part is called
cortex
• Each section produces
different hormones
Adrenal Hormones
• Cortex produces
cortisol
(hydrocortisone)
• Stimulates
carbohydrate
metabolism
• Reduces inflammation
• Stimulates muscle
growth
Cortisol from Adrenal cortex
• Undersecretion leads to
Addison disease, can be
fatal by disturbing
electrolyte balance
• Oversecretion is Cushing
syndrome, alters
carbohydrate and protein
metabolism, and
electrolyte balance
Adrenal Hormones
• Cortex also produces
aldosterone
• Acts on kidney to
increase uptake of
sodium
• Essential for survival
because of its role in
water and solute
balance
Adrenal Hormones
• Medulla produces
epinephrine, also
called adrenaline
• “Fight or Flight”
• Increases heart rate,
blood pressure,
glucose level, and
blood flow to heart
and lungs
Pancreas
• Functions as both
endocrine and
exocrine gland
• Endocrine: hormones
are insulin and
glucagon
• Exocrine: digestive
enzymes
Pancreas
Pancreas
• Special clusters of
cells called the Islets
of Langerhans secrete
hormones
• Alpha cells secrete
glucagon
• Beta cells secrete
insulin
Pancreas
• Glucagon stimulates
the liver to break
down glycogen into
glucose
• Stimulated by low
blood sugar
Pancreas
• Insulin stimulates the
liver to form glycogen
and promotes the
absorption of glucose
into cells
• Lowers blood sugar
• Stimulated by high
blood sugar
Diabetes Mellitus
• Lack of insulin
• Cells are starving;
cannot get glucose into
the cell without
insulin, thus weight
loss is a symptom
• Kidneys try to get rid
of excess sugar,
increasing urine output
and thirst
Diabetes Mellitus
Diabetes Mellitus
High blood sugar
damages blood vessels,
leading to complications
Complications
include:coronary artery
disease, retinal damage,
kidney damage, and
problems from poor
circulation in the
peripheral areas