Endocrine Control Chapter 32. An Orchestra of Hormones Hormones influence the growth, development, and reproductive cycles of nearly all animals They.

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