Endocrine System UNIT 7 Endocrine System Endocrine glands

Endocrine System UNIT 7

Endocrine System Endocrine glands – secrete hormones into nearby tissues, diffuse into bloodstream (Ex. thyroid, pituitary, adrenal, etc. ) Exocrine glands – secrete into tiny tubes or ducts (sweat, salivary, etc. ) Some organs (pancreas) are both endocrine and exocrine

Exocrine Gland - ducts

Hormones §Chemical secreted by a cell that has an effect on the functions of another cell §Very specific – affect only their target cell §Increase # of receptors – increase response §Effect can be brief or long-lasting §Antagonists – hormones that work against each other §Synergists – hormones that work together

Pituitary Gland (AKA Hypophysis)

Pituitary Gland §Also known as Hypophysis §Size of a pea §Attached to the brain by a stalk (infundibulum) §Rests in a bony depression of the sphenoid bone (sella turcica) § 2 lobes §anterior lobe – 7 hormones §posterior lobe – 2 hormones

Anterior Lobe (adenohypophysis) §Prolactin (PRL) – inc. milk production and sustains it after birth §Adrenocorticotropic Hormone (ACTH) Regulates hormone release from adrenal cortex (stress hormones) §Growth Hormone (GH) – stimulates body cells to grow and divide; inc. body’s ability to use fats and carbs for energy

GH Secretion § OVERSECRETION during childhood [before puberty] Leads to Gigantism § OVERSECRETION after puberty leads to Acromegly. § UNDERSECRETION before puberty leads to Dwarfism.

Posterior Lobe (neurohypophysis) § Anti-Diuretic Hormone (ADH) - AKA Vasopressin § stim. DCT/Collecting Duct to reabsorb water, § results in inc. in blood volume and blood pressure, and decrease in urination. § Also a vasoconstrictor (for raising blood pressure). § Failure of this hormone - diabetes insipidus - 20 -30 liters of diluted urine/day, inc. thirst.

§ Oxytocin (OT) - increase in uterine contractions in childbirth (works on positive fdbk loop) § Vasoconstriction – to reduce blood flow and bleeding after childbirth § Ejection of milk during breast-feeding § These two hormones differ chemically by only two amino acids § Both Vasoconstrictors !!

Adrenal Glands (Suprarenal Gl. ) • Located superior to Kidneys • 2 Parts with hormones

Adrenal Cortex (stim. by ACTH from ant. Pituitary) § Aldosterone – (a mineralcorticoid) § Kidney cells (DCT/Collecting Duct) to reabsorb Na+, increasing blood volume (too much, with a weakened blood vessel can burst) and blood pressure. § Released by renin-angiotensin pathway.

§ Cortisol – (a glucocorticoid) § promotes the use of sugar (convert glycogen glucose in the liver), lipids, and proteins § typically in the morning and/or during times of stress. § If not used – it will be re-stored as fat.

Adrenal Medulla §Epinephrine/Norepinephrine (catecholimines) § sympathomimetic – cause changes that mimic sympathetic response [fight or flight] § inc. in hrt rate, BP §diversion of blood to hrt, brain, skeletal muscles, away from digestive organs §bronchial dilation (opens airways)

Pancreas* • Located posterior to stomach • Both endocrine and exocrine*

Pancreas § Insulin From the beta cells in the pancreatic islets (of Langerhans). In response to elevated blood sugar – helps transport glucose into cells. § Glucagon From alpha cells in the pancreatic islets. In response to lowered blood sugar – stimulates cells to convert glycogen glucose

Pancreas conditions § Type I Diabetes Mellitus (juvenile-onset) – no insulin production § Type II Diabetes Mellitus (adult-onset) –decreased sensitivity to insulin --Obesity but can be gotten rid of with diet

Thyroid Gland • Cervical region • Butterfly-shaped

Thyroid Gland § T 3 (Triiodothyronine) – 20% of secretions (4 -5 x stronger than T 4) § T 4 – Thyroxine - 80% of secretions - Both function to increase metabolism, support growth and dev’t - Decrease in these hormones leads to fatigue and weight gain

*Iodine needed in the diet to make these two hormones. Not enough - can lead to overactivity, and swelling of the gland. Known as a goiter.

Thyroid Gland § Calcitonin – serves to increase storage of calcium in the bones by removing it from the blood - lowers blood calcium levels

Parathyroid Gland Located posterior to thyroid

Parathyroid §Parathyroid Hormone (Parathormone) §– opposite effect as calcitonin [antag] § – increases blood calcium levels by encouraging removal of calcium from the bones