Endocrine System

(a) Endocrine signaling Figure 45.2a Blood vessel Response (a) Endocrine signaling Response (b) Paracrine signaling Figure 45.2 Intercellular communication by secreted molecules. Response (c) Autocrine signaling

(d) Synaptic signaling Figure 45.2b Synapse Neuron Response (d) Synaptic signaling Neurosecretory cell Figure 45.2 Intercellular communication by secreted molecules. Blood vessel Response (e) Neuroendocrine signaling

Major endocrine glands: Figure 45.4 Major endocrine glands: Hypothalamus Pineal gland Pituitary gland Organs containing endocrine cells: Thyroid gland Thymus Parathyroid glands (behind thyroid) Heart Liver Adrenal glands (atop kidneys) Stomach Pancreas Kidneys Small intestine Figure 45.4 Major human endocrine glands. Ovaries (female) Testes (male)

Cerebrum Pineal gland Thalamus Hypothalamus Cerebellum Pituitary gland Figure 45.14 Cerebrum Pineal gland Thalamus Hypothalamus Cerebellum Pituitary gland Spinal cord Hypothalamus Figure 45.14 Endocrine glands in the human brain. Posterior pituitary Anterior pituitary

Water-soluble (hydrophilic) Lipid-soluble (hydrophobic) Figure 45.5 Water-soluble (hydrophilic) Lipid-soluble (hydrophobic) Polypeptides Steroids 0.8 nm Insulin Cortisol Amines Figure 45.5 Hormones differ in structure and solubility. Epinephrine Thyroxine

Water- soluble hormone Lipid- soluble hormone Figure 45.6-2 SECRETORY CELL Water- soluble hormone Lipid- soluble hormone VIA BLOOD Transport protein Signal receptor TARGET CELL OR Signal receptor Figure 45.6 Receptor location varies with hormone type. Cytoplasmic response Gene regulation Cytoplasmic response Gene regulation NUCLEUS (a) (b)

G protein-coupled receptor GTP Figure 45.7-2 Epinephrine Adenylyl cyclase G protein G protein-coupled receptor GTP ATP Second messenger cAMP Figure 45.7 Cell-surface hormone receptors trigger signal transduction. Protein kinase A Inhibition of glycogen synthesis Promotion of glycogen breakdown

Estradiol (estrogen) receptor Figure 45.8-2 Hormone (estradiol) EXTRACELLULAR FLUID Estradiol (estrogen) receptor Plasma membrane Hormone-receptor complex NUCLEUS CYTOPLASM Figure 45.8 Steroid hormone receptors directly regulate gene expression. DNA Vitellogenin mRNA for vitellogenin

Same receptors but different intracellular proteins (not shown) Figure 45.9 Same receptors but different intracellular proteins (not shown) Different receptors Different cellular responses Different cellular responses Epinephrine Epinephrine Epinephrine  receptor  receptor  receptor Glycogen deposits Figure 45.9 One hormone, different effects. Vessel dilates. Vessel constricts. Glycogen breaks down and glucose is released from cell. (a) Liver cell (b) Skeletal muscle blood vessel Intestinal blood vessel (c)

S cells of duodenum secrete the hormone secretin ( ). Figure 45.11 Pathway Example  Stimulus Low pH in duodenum S cells of duodenum secrete the hormone secretin ( ). Endocrine cell Hormone Negative feedback Figure 45.11 A simple endocrine pathway. Blood vessel Target cells Pancreas Response Bicarbonate release

Hypothalamus/ posterior pituitary Figure 45.12 Pathway Example  Stimulus Suckling Sensory neuron Hypothalamus/ posterior pituitary Posterior pituitary secretes the neurohormone oxytocin ( ). Neurosecretory cell Positive feedback Neurohormone Blood vessel Figure 45.12 A simple neuroendocrine pathway. Target cells Smooth muscle in breasts Response Milk release

Cerebrum Pineal gland Thalamus Hypothalamus Cerebellum Pituitary gland Figure 45.14 Cerebrum Pineal gland Thalamus Hypothalamus Cerebellum Pituitary gland Spinal cord Hypothalamus Figure 45.14 Endocrine glands in the human brain. Posterior pituitary Anterior pituitary

Liver, bones, other tissues Figure 45.16 Tropic effects only: FSH LH TSH ACTH Neurosecretory cells of the hypothalamus Nontropic effects only: Prolactin MSH Nontropic and tropic effects: GH Hypothalamic releasing and inhibiting hormones Portal vessels Endocrine cells of the anterior pituitary Posterior pituitary Pituitary hormones Figure 45.16 Production and release of anterior pituitary hormones. HORMONE FSH and LH TSH ACTH Prolactin MSH GH TARGET Testes or ovaries Thyroid Adrenal cortex Mammary glands Melanocytes Liver, bones, other tissues

Mammary glands, uterine muscles Figure 45.15 Hypothalamus Neurosecretory cells of the hypothalamus Neurohormone Axons Posterior pituitary Anterior pituitary Figure 45.15 Production and release of posterior pituitary hormones. HORMONE ADH Oxytocin TARGET Kidney tubules Mammary glands, uterine muscles

Figure 45.17 Pathway Example Stimulus Cold Sensory neuron  Hypothalamus Hypothalamus secretes thyrotropin-releasing hormone (TRH ). Neurosecretory cell Releasing hormone Blood vessel  Anterior pituitary secretes thyroid-stimulating hormone (TSH, also known as thyrotropin ). Anterior pituitary Tropic hormone Negative feedback Thyroid gland secretes thyroid hormone (T3 and T4 ). Figure 45.17 A hormone cascade pathway. Endocrine cell Hormone Target cells Body tissues Increased cellular metabolism Response

Hypothyroidism Goiter

Hyperthyroidism

Increases Ca2 uptake in intestines Active vitamin D Figure 45.20-2 Increases Ca2 uptake in intestines Active vitamin D Stimulates Ca2 uptake in kidneys PTH Parathyroid gland (behind thyroid) Stimulates Ca2 release from bones Figure 45.20 The roles of parathyroid hormone (PTH) in regulating blood calcium levels in mammals. STIMULUS: Falling blood Ca2 level Blood Ca2 level rises. Homeostasis: Blood Ca2 level (about 10 mg/100 mL)

Rickets

(a) Short-term stress response and the adrenal medulla Figure 45.21a (a) Short-term stress response and the adrenal medulla Stress Nerve signals Spinal cord (cross section) Hypo- thalamus Nerve cell Nerve cell Adrenal medulla secretes epinephrine and norepinephrine. Effects of epinephrine and norepinephrine: Adrenal gland Figure 45.21 Stress and the adrenal gland. Glycogen broken down to glucose; increased blood glucose Kidney Increased blood pressure Increased breathing rate Increased metabolic rate Change in blood flow patterns, leading to increased alertness and decreased digestive, excretory, and reproductive system activity

(b) Long-term stress response and the adrenal cortex Figure 45.21b (b) Long-term stress response and the adrenal cortex Stress Hypothalamus Releasing hormone Anterior pituitary Blood vessel ACTH Effects of mineralocorticoids: Effects of glucocorticoids: • Retention of sodium ions and water by kidneys • Proteins and fats broken down and converted to glucose, leading to increased blood glucose Adrenal gland Figure 45.21 Stress and the adrenal gland. Adrenal cortex secretes mineralo- corticoids and glucocorticoids. • Increased blood volume and blood pressure • Partial suppression of immune system Kidney

Body cells take up more glucose. Insulin Figure 45.13 Body cells take up more glucose. Insulin Beta cells of pancreas release insulin into the blood. Liver takes up glucose and stores it as glycogen. STIMULUS: Blood glucose level rises (for instance, after eating a carbohydrate-rich meal). Blood glucose level declines. Homeostasis: Blood glucose level (70–110 mg/m100mL) STIMULUS: Blood glucose level falls (for instance, after skipping a meal). Figure 45.13 Maintenance of glucose homeostasis by insulin and glucagon. Blood glucose level rises. Liver breaks down glycogen and releases glucose into the blood. Alpha cells of pancreas release glucagon into the blood. Glucagon