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Endocrine Glands
hypothalamus
INTEGRATION AND CONTROL:
pineal gland
pituitary gland
thyroid gland
parathyroid glands
1. The Endocrine System
thymus gland
adrenal glands
Chapter 35 of Starr et al.
Chapter 32 for Background
pancreatic islets
ovaries
testes
Limbic System
•! Controls emotions and has role in memory
•! Damage to substantia nigra of hippocampus leads
to Parkinson’s disease
(olfactory tract) cingulate gyrus thalamus
Leads into limbic system!
Note the proximity between hypothalamus and pituitary
–! Releasing factors are secreted from hypothalamus
–! Feedback loops between brain and endocrine system
Mediates emotional
stability; interprets social
amygdala
clues!
Long-term memory !
formation! hippocampus
Mediates emotions, !
visceral activity!
Maintains internal!
homeostasis !
hypothalamus
Pituitary Hormones
Hypothalamus & Pituitary
•! Posterior Pituitary
•! Hypothalamus
–! Does not synthesize hormones
–! Secretes
•! Antidiuretic hormone (ADH)
–! Part of limbic system of brain
–! Monitors internal conditions,
emotional states
–! Connected to pituitary by a stalk
–! Secretes releasing factors to the
pituitary
–! Target: walls of kidney
tubules
»! regulates water and salt
levels
•! Pituitary
•! Oxytocin
–! Endocrine gland
–! Anterior lobe
•! outgrowth from roof of mouth
•! glandular
–! Posterior lobe
•! Outgrowth from brain
–! triggers uterine contractions
during birth
–! acts on mammary glands to
release milk
–! Pitocin - synthetic oxytocin
–! neural tissue
•! Anterior Pituitary
–! ACTH -- Corticotropin
[=adrenocorticotropic hormone]
•! Target: adrenal gland
–! Thyrotropin
•! Target: thyroid gland
–! FSH -- Follicle-stimulating hormone
•! Target: ovary
–! LH -- Luteinizing hormone
•! Target: ovary
–! Prolactin
•! Target: breast
–! Somatotropin -- STH, growth
hormone
•! Target: general
•! Does not synthesize hormones
HOMEOSTASIS ….
STH
(GH)
anterior lobe of pituitary
growth-promoting
effects on most
cells
ACTH
PRL
TSH
FSH
LH
both act
LH on:
adrenal
cortex
thyroid
gonads
mammary
glands
•! is the property of
a system that
regulates its
internal
environment so as
to maintain a
stable, constant
condition.
Cells (especially muscle)
take up glucose and use it
or convert it to glycogen.
insulin
Beta cells of pancreas
release insulin into blood.
Liver converts glucose
to glycogen, fats, proteins.
hypothalamus
STIMULUS:
blood level
of glucose
falls too low
CRH
adrenal
cortex
anterior pituitary
adrenal
medulla
ACTH
Blood glucose levels decline
to a set point; stimulus calling
for insulin diminishes.
Stimulus:
Glucose is
absorbed
following a meal.
adrenal cortex
adrenal
gland
blood glucose level
rises; leads to
inhibition of cortisol
secretion
cortisol
1. Blood glucose uptake inhibited.
Blood glucose levels increase
to a set point; stimulus calling
for glucagon diminishes.
Liver converts glycogen
to glucose, stops
synthesizing glycogen.
Alpha cells of
pancreas release
glucagon into blood.
glucose,
amino
2. Proteins degraded in many
acids, fatty
tissues. Free amino acids converted acids enter
to glucose.
blood
Stimulus:
Cells use or store
glucose between
meals.
glucagon
Feedback Loops
•! Negative feedback
–! May involve the same or another hormone
–! As hormone levels rise, further secretion is inhibited
•! Positive feedback
–! As hormone levels rise, further secretion is stimulated
kidney
3. Fats in adipose tissue degraded to
fatty acids, released to blood as
alternative energy sources.
Female Reproductive Cycle
•! Pituitary secretes FSH
–! Egg grows in follicle in ovary
–! Growing follicle secretes estrogen
–! 15 days of estrogen secretion --->
–! LH secretion by pituitary
–! LH causes follicle to burst: ovulation
–! ---> Corpus luteum (CL) formation
–! CL secretes progesterone
–! Progesterone stimulates uterine lining to grow
–! Implanted embryo produces HCG or human chorionic
gonadotropin
–! HCG maintains CL …
Hormone Cycling in Human Females
Summary: Integration and Control
•! Hormones are signaling molecules
–! interact with each other
•! synergistically
•! antagonistically
•! permissively
–! interact with the nervous system
–! respond to environmental cues
Estradiol-17ß
Hormone Structure:
Steroid Hormones
Hormone Structure:
Peptide hormones
•! Assembled from cholesterol
–! lipid soluble
–! readily cross cell membranes
•! (may bind to membrane and alter its characteristics)
Testosterone
•! Bind to a cellular receptor
–! enter nucleus
–! receptor-hormone complex binds to DNA
–! switches genes on or off, promoting (or inhibiting) protein
synthesis
•! Assembled from amino acids
–! water soluble
–! 3 - 180 amino acids in length
•! Bind to receptors in plasma membrane
–! activate membrane-bound enzyme(s)
–! may trigger action of 2nd messenger
ACTH: 39 aa
(adrenocorticotropic hormone)
•! intracellular molecule that relays signals from hormonereceptor complex into the cell
•! cAMP is most common 2nd messenger
Thyroid Gland
Adrenal Gland
•! Synthesizes and secretes thyroxine
–! Requires iodine
•! Lacking in inland salt deposits
•! Deficiency leads to goiter
–! Many effects on homeostasis
•! Temperature control
•! Metabolism
–! Deficiency
•! Weight gain
•! Sluggishness
•! Congenitally: mental retardation
Pineal Gland
•! Cortex produces cortisol
–! Lipid hormone
–! Suppresses inflammation
•! Medulla secretes adrenalin or epinephrine
–! Peptide hormone
–! “Fight or flight” hormone
Pancreas
•! Both exocrine and endocrine
•! Light-sensitive
•! Regulates timing of sexual activity in many
mammals
•! Secretes melatonin in the absence of light
–! Higher levels in winter
•! Regulates circadian rhythms
•! Endocrine function is in islets
–! Alpha cells secrete glucagon
–! Beta cells secrete insulin
•! Diabetes results if
–! Beta cells don’t produce
insulin
OR
–! Target tissues don’t respond
to insulin
Glands and
Hormones
•! Classical View:
•! Hormones + glands =
endocrine system
•! Endocrine Glands
–! 1st recognized ~ 100 years ago
–! Ductless
–! Secrete into bloodstream
•! Exocrine Glands
–! Secrete out of the body
–! Have ducts
•!
•!
•!
•!
Tears
Sweat
Saliva
Gastric secretions
Current Synthesis:
•! Hormones are a subset of
signaling molecules
•! Signaling molecules
–! Bind to a target cell
–! Elicit a response in the target
–! Include hormones, neurotransmitters,
local signalling molecules (cAMP),
pheromones
•! Nervous and endocrine systems
interact
–! Proximity between hypothalamus and
pituitary
–! Releasing factors secreted from
hypothalamus
–! Feedback loops between brain and
endocrine system