General A & P - Unit 10: Endocrine System

Endocrine gland

secrete hormones directly into blood; produce chemical messengers that travel via bloodstream

hormone

chemical messenger that produce a desired change or function, very specific

hormone functions

regulate metabolic processes; speed up reactions (activate enzymes), change membrane permeability (transport), water & electrolyte balance, reproduction, growth/development, protein synthesis

hormone action

lock and key mechanism; hormone will only bind to a specific receptor, and each specific complex will produce a specific effect

target cells

contain specific receptors; hormone binding to target cell receptor produces effect

steroid group & action

(cortisol, aldosterone, estrogen, testosterone, etc) lipid molecules- lipid soluble (can enter directly into cell) where the receptor is located inside the nucleus (mobile receptor), H-R complex activates certain genes: produces protein. 45 min-several days for full effect to occur

Non-steroid group & action

(peptides, glycoproteins, proteins, aa derivatives, prostaglandins) hormone (1st messenger) outside of cell binds to “fixed receptor”: within cell causes a 2nd messenger in cell to produce a desired cellular changes. H-R complex; G protein activates adenylate cyclase (enzymes) that converts ATP to cAMP (send messenger), which activates protein kinases to activate enzymes to produce desired response.

prostaglandins

a group of lipids produced by fatty acid and ACT LOCALLY: secrete into fluid surrounding a gland. Functions include fever, lowering BP, preventing ulcers, uterine contractions, cAMP interaction

hormonal secretion control mechanism

hypothalamus controls release of hormones from anterior pituitary

neural secretion control mechanism

nervous system can directly stimulate adrenal medulla to secrete

humoral secretion control mechanisms

gland cells can respond directly to internal environment

pituitary gland

“master gland”; found in sella turcica, connected to hypothalamus via infundibulum

adenohypophysis: anterior pituitary gland

regulated by releasing hormones from hypothalamus which are released directly into hypophyseal portal system; can produce AND release hormones

hypophyseal portal system

how hypothalamus communicates with anterior pituitary gland: effects can be inhibitory or stimulator

neurohypophysis: posterior pituitary gland

stores hormones that are produced by neurosecretory cells found in hypothalamus; neural tissue

Growth hormone (GH)

secreted by anterior post. pituitary; increase aa transport into cells, therefore stimulation protein anabolism, increases growth rate

GH hyposecretion

hypopituitary dwarfism

GH hypersecretion

before g.p. closes: gigantism

After g.p. closes: acromegaly

Prolactin (PRL)

simulate breast development and milk secretion

PRL hyposecretion

unable to breastfeed, miscarriage

PRL hypersecretion

male infertility, disrupt menstral cycle

tropic hormone

stimulate other endocrine glands to release their hormones (TSH, ACTH)

Thyroid stimulating hormone (TSH)

tropic, secreted by anterior pituitary; maintain thyroid gland, stimulates thyroid to secrete T4 and T3 (helps regulate metabolism)

Adrenocorticotrophic hormone (ACTH)

tropic, secreted by anterior pituitary; maintains adrenal cortex, stimulates adrenal cortex to secrete

gonadotropins

glycoproteins (FSH, LH, and ISCH)

Follicle stimulating hormone (FSH)

gonadrotropin; in women, stimulate ova production and ovaries to secrete estrogen

in men, development of seminiferous tubules and stimulate sperm production

Luteinizing hormone (LH)

causes ovulation, stimulates corpus lutetium to secrete progesterone/estrogen

ISCH = male LH (stimulate development of interstitial cells —> secrete testosterone)

hypothalamus

neural control center of endocrine system; controls release of hormones from anterior pituitary gland

posterior pituitary gland

ADH & oxycotin storage and release site; synthesized in hypothalamus by neurosecretory cells —> axons travel to post pituitary gland where hormones get released

ADH

concentrates urine, increases water reabsorption in kidney tubules

Controlled by: dehydration is sensed by osmoreceptors in hypothalamus, causing release of ADH

Oxycotin (OT)

increases uterine muscle contractions, stimulates milk “let down” (positive feedback), allows milk release

diabetes insipidus

impairs ADH regulation of water balance

thyroid gland

secretes T4, T3, and calcitonin

T4 (thyroxine)

produced by follicle cells, stored as colloid, 4 iodine atoms, 20x more in blood, converted to T3

T3 (triiodothyronine)

produced by follicle cells, stored as colloid, 3 iodine cells, 5x more potent, principle thyroid hormone)Fu

Function of T4 & T3 cells

regulate basal metabolic rate of all cells (cell growth and tissue differentiation), general “target": can potentially act with any cell

Calcitonin

produced by thyroid (due to humoral mechanism); increases bone formation, decreases bone breakdown, antagonist to PTH for calcium homeostasis, released from thyroid stimulus when blood calcium levels are high

hypersecretion of thyroid gland

graves disease; weight loss, nervousness, increased heart rate, eyes protrude

may result in enlarged thyroid

hyposecretion of thyroid gland

cretinism - (infantile)

myxedema (adult) - lower metabolic rate, weight gain, hair loss

hashimoto’s thyroiditis - autoimmune

goiter - iodine deficiency; decreased production of thyroid hormone

may result in enlarged thyroid

Parathyroid hormone (PTH)

posterior of thyroid glands, 3 targets

bone cells - increase bone breakdown

kidneys - increase calcium reabsorbed into blood

intestines - activates vitamin D to increase calcium absorption

overall effect: blood calcium levels back up

hyperparathyroidism

fatigue, muscle weakness, painful joints, altered mental functions, etc

hypoparathyroidism

muscle cramps and seizures

adrenal glands

closely associated with kidneys, adrenal cortex and medulla

Aldosterone

produced by mineralocorticoids (outermost layer or cortex): main function is sodium homeostasis increase sodium reabsorption into blood by kidneys; secondary functions include water reabsorption, increased potassium & hydrogen into urine)

stimulated by high potassium directly

Cortisol

produced by glucocorticoids (middle layer of cortex): effects every cell in the body, stimulates breakdown of proteins into aa’s, which go to liver —> gluconeogenesis: making glucose from scratch using aa’s. decreased immunity and anti-inflammatory effect

Androgens

produced by gonadocorticoids (innermost layer of cortex): sex hormones

adrenal medulla

modified sympathetic post gang. fiber (neural tissue), activated by sympathetic system, produces epinephrine and norepinephrine

pancreas

mixed gland; exocrine function produces digestive enzymes released into intestine

function: produce hormones i

islets of langerhans

(pancreas) 3 types of cells

Alpha- Glucagon

Beta- Insulin

Delta - Somatostatin

Glucagon

promotes glycogenolysis, promotes glyconeogenesis

glycogenolysis

glycogen broken down into glucose by liver

insulin

promotes formation of of glycogen, facilitated diffusion of glucose into cells, protein synthesis, fat synthesis, movement of glucose, aa’s, and fatty acids from blood into cells

decreases blood glucose levels

stimulated by high blood glucose levels

diabetes mellitus

cannot makeenough insulin

Type I diabetes

insulin dependent, juvenile onset, autoimmune, decreased/low insulin production, need insulin injections

Type II diabetes

adult onset, 85% of population, low insulin receptors, risk factors: obesity, sedentary lifestyle , control by diet, exercise, healthy lifestyle

pineal gland

biological clock; secretes melatonin: induces sleep, seasonal affective disorder

thymus gland

located in mediastinum, large until puberty, secretes thymosin: stimulates production of specialized lymphocytes (T cells)

estrogen

develop secondary sex characteristics; stimulated by FSH

progesterone

maintain uterus; stimulated by LHt

testosterone

develop secondary sex characteristics (stimulated by ICSH)

adrenal cortex

outer pancreas; produce cortisol, androgens, and aldosterone