Endocrine System

Chapter 16Human Anatomy & Physiology 8/e, Marieb & Hoehn. (Pearson 2010)

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Today’s class

Endocrine glands and hormones Mechanisms of hormone action Hypothalamus and pituitary gland Adrenal gland Thyroid and parathyroid glands Pancreas

Nervous and endocrine systems

Two systems of internal communication and regulation act individually or together

Nervous system high-speed electrical signals via neurons

Endocrine system endocrine glands secrete hormones

slower, longer-acting responses

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Endocrine glands

Ductless Secrete hormones

into bloodstream hormones affect

target with receptor some prehormones

and prohormones

fig 16.1

Types of chemical signals

pheromones endocrine paracrine

Human Reproductive Biology, 3/e. by S. Mader. McGraw Hill publishers. 2005. fig 5A

Hormones trigger cell signalling

Three stages:

1. reception

2. signal transduction

3. response

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Structural categories of hormones

Polypeptides and proteins Amino acid derivatives (amines) Steroids (Eicosanoids)

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Examples

(Anatomy and Physiology, 8/e, Seeley, Stephens and Tate, 2008, McGraw Hill, fig 17.3)

(autocrine regulator)

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General hormone effects Interactions

Synergistic (effect of 2 combine better than one)

Permissive Antagonistic

Concentration half-life (how long in the blood stream)

Target cell specificity receptor type, number and affinity upregulation, desensitization/downregulation

Importance of receptorse.g. complete androgen insensitivity syndrome (AIS)

XY individual testes present no ovaries or uterus testosterone

synthesized but no functional receptor

10Human Reproductive Biology, 3/e. by S. Mader. McGraw Hill publishers. 2005. fig 3.14

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Mechanisms of hormone action Peptide/protein/amines: receptors in Plasma membrane (cuz the

molecules are too big) different mechanisms, between from getting point A to B e.g.

cAMP – second message. 1st message in hormone DAG/IP3 (phospholipase C) – cut the phosphol

tyrosine kinase Activate “premade” proteins

Lipids: intracellular receptors reach target via carrier proteins in plasma

why the need for carrier? Need a carrier cuz there hydrphobic and direct to the right tissue

nuclear hormone receptors as transcription factors They create protein with transcription, translation, termination.

Recall cAMP as second messenger

12fig 16.2

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Phospholipase C system

PIP2 IP3 + DAGphospholipase C

Human Physiology, 10e, by Fox, McGraw Hill publishers, 2008, fig 11.9

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Insulin and its tyrosine kinase receptor

Human Physiology, 10e, by Fox, McGraw Hill publishers, 2008, fig 11.11

no second messenger required

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Lipid-soluble hormones

fig 16.3

Control of hormone release

Endocrine gland stimuli Humoral Neural Hormonal

Nervous system modulation

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Control of hormone release

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fig 16.4

Hypothalamus and pituitary Control much of endocrine system Integrate nervous and endocrine systems

receives nerve signals from body initiates appropriate responses

Neurosecretory cells Posterior pituitary – not true (keeper and releaser of

hyperthalmus) stores and releases hormones made by hypothalamus

Anterior pituitary Hypthalmus when to make/ nt make the hormones

true endocrine gland makes 6 trophic hormones

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Hypothalamus and posterior pituitary

19fig 16.5aWhat are functions of oxytocin and ADH?

Hypothalamus and anterior pituitary

20fig 16.5b

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Targets of anterior pituitary hormones

Human Physiology, 10e, by Fox, McGraw Hill publishers, 2008, fig 11.15

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Hypothalamus and anterior pituitary

Hypothalamic-releasing hormones stimulate anterior pituitary gonadotropin-releasing hormone (GnRH) prolactin-releasing hormone (PRH) growth hormone-releasing hormone

(GHRH) corticotropin-releasing hormone (CRH) thyrotropin-releasing hormone (TRH)

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Hypothalamus-pituitary-target axis

Hypothalamus anterior pituitary target GnRH FSH, LH gonads sex hormones PRH prolactin mammary glands GHRH growth hormone various CRH ACTH adrenal cortex

corticosteroids (stress response) TRH TSH thyroid metabolism hormones

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Feedback examples

hypothalmus-pituitary-gonad axis

hypothalmus-pituitary-thyroid axis

Human Physiology, 10e, by Fox, McGraw Hill publishers, 2008, figs 11.17, 11.18

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Thyroid gland

Located just inferior to larynx

Follicles follicular cells

thyroxine colloid fluid

Parafollicular cells calcitonin

fig 16.8

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Thyroid hormones

T3 and T4 (thyroxine) elevate basal metabolic rate

stimulate protein synthesis, increase respiration, etc

Calcitonin lowers blood calcium concentrations

inhibits dissolution of calcium phosphate in bone

stimulates excretion of calcium in urine

Synthesis of thyroid hormone

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fig 16.9

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Diseases of thyroid: hypothroidism

Hypothyroidism: thyroid function slower than normal metabolism myxedama (fluid/mucoprotein accumulation

in subcutaneous tissue) Causes

Gland defect (e.g. by Hashimoto’s thyroiditis) Too little TRH and/or TSH for trophic effects Endemic goiter: by iodine deficiency

Hyperthyroidism: thyroid function more rapid than normal metabolism e.g. by Grave’s disease (autoimmune)

autoantibodies are TSH receptor agonists

fig 16.10

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Parathyroid glands

4 glands embedded in lateral lobes of thyroid gland

Secrete parathyroid hormone (PTH) control of blood Ca2+ levels

fig 16.11

Recall

30fig 16.12

Adrenal gland

Outer cortex no neural innervation steroid hormones

corticosteroids (corticoids) aldosterone effects will be covered in more

detail with urinary system Medulla

preganglionic sympathetic neurons catecholamines

epinephrine (mainly) norepinephrine 31

Adrenal gland

32fig 16.13

Cushing’s syndrome: excess glucocorticoid

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fig 16.15

Stress and adrenal gland

34fig 16.16

Aldosterone release from adrenal cortex

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* Aldosterone targets kidneys

fig 16.4

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Pancreas Exocrine and endocrine Islets

alpha cells: glucagon in response to blood glucose

stimulates liver: glycogen glucose, fat hydrolysis

beta cells: insulin in response to blood glucose

promotes entry of glucose into tissue glucose glycogen, fat

feeding versus fasting?

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Pancreas and blood glucose homeostasis

Human Physiology, 10e, by Fox, McGraw Hill publishers, 2008, fig 11.31

fig 16.18

Other hormones

Pineal gland: melatonin Gonads (testes and ovaries): sex

hormones will be covered with reproductive system

Other organs (non-endocrine glands) secrete hormones heart, GI tract, kidneys, skin, adipose

tissue, skeleton, thymus38

Up next

December office hours Monday, December 6: 10-12, 2-4 Monday, December 13, 2-5

Exam (cumulative) Tuesday, December 14, 9-11

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