Wada A&P II Endocrine System

Endocrine System Functions

1. Maintains homeostasis

2. Influences metabolic activities

3. Integrates and regulates growth and development

4. Controls, maintains and instigates sexual reproduction, including gametogenesis (generating gametes), coitus, fertilization, fetal growth and development, nourishment of the newborn)

Nervous vs Endocrine Duration of Effect

Nervous System- Short-term crisis management

Endocrine System- Long-term crisis management

Nervous vs Endocrine system Signal

Nervous- Neurotransmitters

Endocrine- Hormones

Nervous vs Endocrine speed of response

Nervous- Very fast (milliseconds)

Endocrine- Take minutes to hours to act

Nervous vs Endocrine distribution of effect

First, both act through receptors

Nervous- Localized effect

Endocrine- Systemic (hormones travel in the blood stream)

Exocrine Glands

• Excrete non-hormonal products (ex. enzymes) to a membrane surface

• Have ducts

Endocrine Glands

• Secrete hormones

• Ductless glands

• Into the bloodstream

Most hormone release are controlled by ______

Negative Feedback (in rare cases, it’s positive feedback)

The hormone feeds back to inhibit its own secretion

Hypothalamus hormones

• Produces antidiuretic hormone (ADH) and oxytocin

- Hypothalamic neurons extend into the posterior pituitary gland

• Produces regulatory hormones (regulates hormone secretion from anterior pituitary gland)

*Portal system: Capillary bed→Vein→Capillary bed

Posterior Pituitary Gland hormones

• Secretes ADH and oxytocin (produced in hypothalamus)

Anterior Pituitary Gland hormones

(Secretion is regulated by hypothalamic regulatory hormones)

• Produces LH, FSH, ACTH, TSH, GH

Pineal Gland hormones

Produces and secretes melatonin which regulates the biological clock

Thyroid gland hormones

• Produces and secretes T3 (triiodothyronine) and T4 (thyroxine)

Parathyroid gland hormones

• Produces and secretes parathyroid hormone

• Parathyroid hormone affects calcium and phosphate levels in the body

Heart hormones

• Produces and secretes Atrial natriuretic peptide (ANP)

• ANP decreases renin, aldosterone, and ADH

Digestive System hormones

• Produce and secrete gastrin, secretin, somatostatin, and cck

Pancreas hormones

• Produce and secrete insulin (lowers blood glucose) and glucagon (increases blood glucose)

• Both endocrine and exocrine glands

Kidney hormones

• Erythropoietin, which stimulates red blood cell production

Adrenal Cortex hormones

• Cortisol (stress), aldosterone (Na+ reabsorption and K+ secretion)

Adrenal Medulla hormones

• Epinephrine and Norepinephrine (fight or flight response)

Adipose Tissue hormones

Leptin- regulates food intake and energy expenditure in the long term

Gonad hormones

Testes: androgen, inhibin

Ovaries: estrogen, progesterone, inhibin

3 Types of Hormones

• Amino Acid derivative- Epinephrine and thyroid hormone

• Peptide derivative- TRH, ADH, oxytocin, LH, and FSH

• Lipid derivative- Estrogen and testosterone

Amino Acid and Peptide derivative hormone characteristics

• Water soluble (cannot cross cell membrane and dissolves well in blood)

• No binding proteins

• Bind to membrane receptors on the cell membrane

• Activate second messenger, such as cAMP (activate or inactivate enzymes in a cell)

Exception: Thyroid hormones- are from tyrosine BUT act as lipid derivative

Thyroid and Steroid hormone characteristics

• Lipid soluble- CAN cross cell membrane, doesn’t dissolve well in blood

• Bind to binding proteins for transport in the blood

• Bind to intracellular receptors (inside cell), TH- receptors in mitochondria

• Hormone-receptor complex enters the nucleus, binds to DNA and start/stop making a protein by transcription and translation

Hormone action depends on

• Blood levels of the hormone

- Rate of hormone synthesis by endocrine cells

- Levels of binding proteins (when hormones are bound to receptors they cannot enter the cell)

- Clearance rate (how quickly hormones are removed from blood/body)

• Number of receptors present on target cells

- Can increase by up-regulation of receptors (more action by hormone)

- Can decrease by down-regulation of receptors (less action by hormone)

• Affinity (strength of hormone and receptor interaction) of those receptors for the hormone

Target cells of hormones from Anterior Pituitary Gland

• Prolactin: Mammary glands (Milk production)

• Growth Hormone: Bone Growth

• LH and FSH: Gonads (Steroid synthesis and gametogenesis)

• Thyroid Stimulating hormone (TSH): Thyroid gland (to produce T3 and T4)

• ACTH: Adrenal gland (to produce cortisol, aldosterone, androgens)

Target Cells of hormones from posterior pituitary gland

ADH: Kidney- inserts aquaporins to increase water reabsorption

Oxytocin: Mammary Gland and Uterus- Milk release and uterus contraction during childbirth

Acute Stress Response

• Hormone: Epinephrine/Noepinephrine (adrenal medulla)

1. Brain sends signal down the spinal cord

2. Sympathetic nerves stimulate adrenal medulla to secrete epinephrine and norepinephrine

3. Those hormones trigger a fight or flight response

- Increases HR and BP

- Vasoconstriction of some vessels

- Vasodilation in skeletal muscle and heart

- Suppression of digestive system and urine output

- Dilation of bronchioles=more air into the lungs

Long-Term Stress Response

• Hormone: Cortisol and aldosterone

1. In response to a stressor, hypothalamus secretes corticotropin releasing hormone (CRH)

2. CRH stimulates anterior pituitary to secrete ACTH

3. ACTH travels through blood to adrenals

4. ACTH stimulates the secretion of cortisol, aldosterone, and androgens

5. Cortisol feedback negatively to decrease CRH+ACTH

Look at this page

Cortisol

Can lead to hyperglycemia and eventually diabetes

1. Increases glycogen synthesis

2. Protein catabolism/breakdown of proteins

3. increases gluconeogenesis (make new glucose from aa+glycerol)

Can lead to hypertension, infection/disease, and infertility

4. Insulin resistance

5. Fat deposition around abdomen

6. Increase in blood pressure

7. Suppresses immune system

8. Suppresses reproductive system (decrease in testosterone from testes)

Elevated or Depressed hormone levels are caused by:

• Failure of f