Transcript The Endocrine System

The Endocrine System
Hormone =
Types:
• peptide or protein = at least 3 amino acids
• steroid = derived from cholesterol
• amine = derived from single amino acids (tryptophan,
tyrosine)
Peptide Hormones
Synthesis/transport/half-life =
Storage?
Multiple processing patterns for protein hormones
Because peptides are
impermeable, they must use
membrane receptors and
second messenger signal
transduction mechanisms to
produce the desired effects.
Most use g-protein coupled
receptors, but some use
tyrosine kinase type
receptors (i.e. insulin)
Steroid Hormones
Steroid hormone synthesis/storage/half-life
Mechanism of cellular activation?
Amine hormones
Neurohormones =
Three major groups
1. Posterior
pituitary/hypothalamus
•
Vasopressin (ADH)
•
Oxytocin
2. Anterior
pituitary/hypothalamus
3. Catecholamines of the
adrenal medulla
2. Anterior pituitary –
hypothalamus
• Prolactin
• Thyroid stimulating
hormone (TSH)
• Adrenocorticotropic
hormone (ACTH)
• Growth hormone (GH)
• Follicle stimulating hormone
(FSH)
• Leutinizing hormone (LH)
Most target other
endocrine glands or cells
Tissues can be targeted by multiple hormones
Hormones can act synergistically, permissively, or antagonistically
Synergistic effects of
hormones on blood
glucose concentration
Example of Hormone Regulation – Vasopressin (ADH)
• Regulation of body water is a response to ECF volume changes (in particular, blood
volume)
• When blood volume changes, volume receptors in the blood vessels and atria
respond
• Carotid sinus and aortic baroreceptors
• Afferent nerves from these receptors go to the cardiovascular center in the
brainstem
• Increased pressure would signal the center to
• Decreased pressure would signal the center to
• When blood volume changes, stretch receptors in the atria also respond
• Increased pressure also signals the cardiovascular center to
• Increased pressure signals the hypothalamus (this is where ADH release is
controlled)
• When blood volume
increases, filtration in the
kidney is adjusted so that
more fluid is filtered per
minute
• Typically, under normal
situations, the kidneys are
not under the influence of
ADH and water follows ions
as they pass through the
kidney tubules
• There are few aquaporin
molecules in the cell
membranes of the kidney
collecting ducts in the
absence of ADH. They are
stored inside the cells.
Influence of ADH on the Collecting Ducts
Feedback Loop for ADH
Negative feedback
What regulates NaCl?
Regulation of Na+
• Increasing osmolarity of the blood stimulates thirst behaviors, and increases
ADH secretion. Drinking and preventing water loss from the kidneys,
decreases blood osmolarity
How would this graph
change if an individual
had hypertension (high
blood pressure)?
Long-term regulation of Na+
• Under the control of aldosterone; it increases Na+ reabsorption into the
blood from the kidney filtrate
What will happen to plasma [K+]?
What will be the overall effect on plasma osmolarity?
The hormone leutininzing hormone (LH) stimulates ovarian cells
to produce the hormone progesterone by way of a second
messenger system. When an antagonist is used to activate
adenylyl cyclase in the ovarian cells, the level of progesterone
produced is not as great as when LH stimulates the cells. It has
also been observed that the intracellular levels of free calcium
increase when LH stimulates the cells. What does this
information imply about the mode of action of LH? Explain.