Endocrine Control Chapter 32. An Orchestra of Hormones Hormones influence the growth, development,...
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Transcript of Endocrine Control Chapter 32. An Orchestra of Hormones Hormones influence the growth, development,...
Endocrine Control
Chapter 32
An Orchestra of Hormones
• Hormones influence the growth,
development, and reproductive cycles
of nearly all animals
• They influence behavior, physical
appearance, and well-being
Hormones
• Secreted by endocrine glands,
endocrine cells, and certain neurons
• Animal hormones travel through the
bloodstream to nonadjacent target cells
Other Signaling Molecules
• Neurotransmitters
• Local signaling molecules
• Pheromones
Endocrine System
Main Sources • Pituitary gland• Adrenal glands• Thyroid gland• Parathyroid
glands• Pineal gland• Thymus gland
Fig. 32.2b, p. 523
HYPOTHALAMUS
PITUITARY GLAND
ADRENAL GLANDS
OVARIES
TESTES
PINEAL GLAND
THYROID GLAND
PARATHYROID GLANDS
THYMUS GLAND
PANCREATIC ISLETS
Responses to Hormones Vary
• Different hormones activate different
responses in the same target cell
• Not all types of cells respond to a
particular hormone
Two Main Hormone Types
• Steroid hormones– Derived from cholesterol– Estrogens, progestins, androgens (such as
testosterone), cortisol, aldosterone
• Peptide hormones– Peptides, proteins, or glycoproteins– Glucagon, ADH, oxytocin, TRH, insulin,
somatotropin, prolactin, FSH, LH, TSH
Steroid Hormone Action
• Most diffuse across the plasma membrane and bind to a receptor
• Hormone-receptor complex acts in nucleus to inhibit or enhance transcription (protein synthesis)
Steroid Hormones
receptor
hormone-receptor complex
gene product
hormone
• Most diffuse across the plasma membrane and bind to a receptor
• Hormone-receptor complex acts in nucleus to inhibit or enhance transcription
Protein Hormone
• Hormone binds to a receptor at cell surface
• Binding triggers a change in activity of enzymes inside the cell
glucagon receptor
cyclic AMP + Pi
ATP
cAMP activatesprotein kinase A
glucagon
Protein kinase A converts phosphorylasekinase to active form and inhibits an enzyme required for glucagon synthesis.
The Hypothalamus
• Region in the brain
• Contains hormone-
secreting cells
• Interacts with
pituitary
hypothalamus
pituitary gland
Fig. 32.2a, p. 522
HYPOTHALAMUS
PITUITARY GLAND
anterior lobe posterior lobebone at base of cranial cavity
Pituitary Gland
• Two lobes
– Posterior lobe (neurohypophysis) stores and
secretes hormones that were synthesized in
the hypothalamus
– Anterior lobe (adenohypophysis) produces
and secretes its own hormones
Posterior Lobe
• Antidiuretic hormone (ADH )
• Oxytocin (OCT)
cell body in hypothalmus
axons
to the general circulation
Fig. 32.5, p. 527
POSTERIOR LOBE OF PITUITARY
kidney tubules
mammary glands
smooth muscle in wall of the uterus
ADH
oxytocin
cell body in hypothalmus
axons
to the general circulation
Anterior Pituitary
• ACTH• TSH• FSH• LH• PRL• STH
Fig. 32.6, p. 527
ANTERIOR LOBE OF PITUITARY
mammary glands
adrenal cortex
thyroid gonads
growth-promoting effects on most cells
ACTH
PRLFSH LH
both act on:TSH
STH(GH)
Capillary bed at base of hypothalmus
Cell bodies secrete releasing and inhibiting hormones
Capillary bed in anterior pituitary
Feedback Mechanisms
• Negative feedback
– An increase in concentration of a hormone
triggers activities that inhibit further secretion
• Positive feedback
– An increase in concentration of a hormone
triggers activities that stimulate further
secretion
Control of Cortisol Secretion (1)
• Hypothalamus senses decline in glucose
and secretes a releasing hormone (CRH)
• CRH stimulates anterior pituitary to
secrete ACTH
• ACTH acts on the adrenal cortex to
stimulate cortisol secretion
Control of Cortisol Secretion (2)
• Cortisol secretion
– Inhibits blood glucose uptake by muscle and
other tissues
– Causes breakdown of proteins to amino
acids and conversion to glucose
– Causes degradation of adipose tissue to fatty
acids for use as energy source
Control of Cortisol Secretion (3)
• Decrease in glucose uptake and release of glucose from protein breakdown causes blood glucose level to rise
• Hypothalamus and anterior pituitary detect the increase and decrease secretion of CRH and ACTH
• Adrenal cortex decreases cortisol secretion
Thyroid Gland Disorders
• Goiter
• Hyperthyroidism
• Hypothyroidism
Feedback Control of Ovaries
• Pituitary produces hormones (LH, FSH) that stimulate egg maturation and ovulation in the ovary
• They also stimulate ovary to produce progesterone and estrogen
• After ovulation, rising levels of these hormones inhibit further secretion of LH and FSH
Control of Glucose Metabolism
insulin
Glucose rises
Glucose fallsGlucose is absorbed
Cells use glucose
glucagonGlycogen to glucose
Glucose uptake
Glucose to glycogen
Diabetes Mellitis
• Disease in which excess glucose accumulates in blood, then urine
• Effects include– Excessive urination– Constant thirst– Weight loss– Ketone formation and acid-base imbalances
Two Types of Diabetes
• Type 1
• Auto-immune disease
• Usually appears in
childhood
• Treated with insulin
injections
• Type 2
• Target cells don’t
respond
• Usually appears in
adults
• Treated with diet,
drugs