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 T4 – Thyroxine - 80% of secretions T3 (Triiodothyronine) – 20% of secretions (4-5x stronger than T4) T4 – 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 *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