Unit 1 Anatomy Review

Endocrinology

study of hormones and endocrine organs

Hypothalamus function

stimulates pituitary gland which secretes tropic hormones

exocrine organs/ glands

produce non-hormonal substances which are secreted onto membrane surface from ducts

endocrine organs/glands

ductless, produce hormones which are secreted directly into bloodstream

3 Factors of cell activation

1. Blood level of hormone

2. Relative number of receptors on/in target cell

3. Affinity (binding strength between receptor and hormone)

up-regulation

consistently low hormone presence stimulates cell to generate more receptors for hormone

down-regulation

consistently high hormone presence stimulates cell to lose receptors for hormone

Amino Acid-based (peptide) hormones

• made from amino acids

• almost all water-soluble (except thyroid hormone)

• cannot enter cell: must bind to a receptor on plasma membrane triggering second messengers

Steroid Hormones

• made from cholesterol

• all fat-soluble

• directly enter cell: diffuse through the membrane, bind receptor inside cell and directly activate genes

amino acid based hormones stimulate effects by…

Receptors on cell membrane activate a signal carrier (G protein) inside the cell. That carrier binds to an enzyme that stimulates the release of second messenger. The second messenger stimulates hormone’s effect on cell

steroid hormones stimulate effects by…

Hormone binds directly to intracellular receptor on nucleus while the receptor-hormone complex binds to specific region on DNA then DNA transcription and translation begin

3 ways hormones interact at target cells

• permissively

• synergistically

• antagonistically

Permissive Interaction

one hormone will not exert its effects without the other hormone being present

Synergist Interaction

multiple hormones working together toward same end-goal

• can amplify (stronger) effect

• 2 different effects creating greater overall effect

Antagonist interaction

one or more hormones oppose actions of another

Humoral stimulus

change in blood levels of ions and nutrients

Neural stimulus

nerve fibers stimulate hormone release

Hormonal (tropic) stimulus

hormones stimulate other endocrine organs to release their hormones

• aka hormonal stimulus

• ex: hypothalamic-pituitary-target feedback loop

hypothalamic-pituitary-target endocrine organ feedback loop

Hypothalamus stimulates release of pituitary hormone that stimulates target endocrine organ to release its hormone. The increased target organ hormone presence & effects causes humoral changes which are interpreted by hypothalamus then adjustment made by hypothalamus.

Negative feedback

hormone released to counter a changer in blood or cellular chemistry

• concentrations in solutes or solvent

Positive feedback

hormone released reinforces change until process achieves natural conclusion

• oxytocin

• often sex/ reproduction related

endocrine organs/ glands

• hypothalamus

• pituitary gland

• thyroid gland

• adrenal gland

• pancreas

• gonads

hypothalamus

main homeostasis regulator

Hypophyseal portal system

connects the hypothalamus to the pituitary gland by neurohypophysis and adenohypophysis

Neurohypophysis

neurally stimulates the posterior pituitary

• hypothalamic neurons’ axons run into posterior pituitary and directly secrete hormones from pituitary into bloodstream

Adenohypophysis

hormonally stimulates the anterior pituitary

• hypothalamic neurons secretes releasing and inhibiting hormones into portal veins to regulate the release of pituitary hormones

Pituitary gland separates into

anterior pituitary and posterior pituitary

Anterior Pituitary contains

• growth hormone (GH)

• prolactin (PRL)

• thyroid-stimulating hormone (TSH)

• adrenocorticotropic hormone (ACTH)

• follicle-stimulating hormone (FSH)

• luteinizing hormone (LH)

Posterior Pituitary contains

• antidiuretic hormone (ADH)

• oxytocin

Growth Hormone (GH)

directly increases glucose uptake, glycogen breakdown, blood fatty presence, protein synthesis, musculoskeletal growth

Prolactin (PRL)

increases milk formation at mammary glands

Thyroid-stimulating hormone (TSH)

stimulates production of thyroxine (T4) at thyroid gland

Adrenocorticotropic hormone (ACTH)

stimulates adrenal cortex to release corticosteroids (cortisol) and androgens

follicle-stimulating hormone (FSH)

stimulates the production of gametes (sperm and egg)

luteinizing hormone (LH)

stimulates the production of gonadal hormones (testosterone, estrogen, and progesterone)

antidiuretic hormone (ADH)

targets kidney tubules to reabsorb water (reduce urine production/ output) when body is dehydrated, blood pressure, and solute concentrations are very high

• inhibited by alcohol & diuretics

oxytoxin

stimulates uterine contractions and milk ejection

• used to simulate labor contractions

Diabetes insipidus

hyposecretion of antidiuretic hormone (ADH)

Gigantism

• hypersecretion of growth hormone

• very tall (~8ft) but everything proportional

Acromegaly

• hypersecretion of GH

• overgrowth of hands, feet, face

• closed growth plates

pituitary dwarfism

• hyposecretion of GH

• everything is proportional, often in children

prolactinoma

• pituitary tumore causing hypersecretion of prolactin in men

• may trigger lactation

thyroid gland

• regulates all metabolism

• cells (follicles) produce thyroglobulin which creates colloid when iodine is present

goiter

lack of iodine results in a hyperproduction of unstable thyroglobulin causing gland to swell

Thyroid hormone

• body’s major metabolic hormone

• responsible for raising basal metabolic rate and heat production

• regulates tissue growth and development (skeletal, nervous, reproductive)

• 2 forms: thyroxine (T4) and triiodothyronine (T3)

Thyroxine (T4)

major, inactive thyroid hormone form containing 4 iodine atoms

Triiodothyronine (T3)

active form containing 3 iodine atoms; converted from T4

calcitonin

• secreted from parafollicular cells

• antagonist to PTH acting to lower blood calcium levels

• high doses can be used to combat osteoporosis

myexdema

hyposecretion of thyroid hormone

• symptoms: low metabolic rate, thick/dry skin, cold intolerance, mental sluggish, lethargy (tired, lazy)

cretinism

congenital hypothyroidism often caused by poor development of thyroid gland

• causes reduced growth and brain development in early childhood

grave’s disease

autoimmune disease where body makes abnormal antibodies against thyroid cells

• causes hypersecretion of thyroid hormone as antibodies mimic TSH

• symptoms: elevated metabolic rate, sweating, rapid & irregular heartbeats, rapid weight loss without dietary/ exercise intervention, bulging/ protruding eyes (exophthalmos)

parathyroid gland

4 to 8 tiny glands embedded on posterior aspect of thyroid

• secretes parathyroid hormone (PTH)

Calcium functions

muscle contraction, heart function, blood clotting

parathyroid hormone (PTH)

• targets bones, kidneys, & intestines to reabsorb Ca²⁺

• raises blood calcium when it’s low

• inhibited by high blood Ca²⁺ levels

hyperparathyroidism

• caused by parathyroid tumor

• Ca²⁺ leeched from bones causing them to soften and deform

• elevated Ca²⁺ levels depress nervous system and contribute to kidney stone formation

• often treated with gland resection and vitamin D supplements

adrenal glands

• paired, pyramid shaped glands which sit atop the kidneys

• both structurally and functionally two glands in one

• adrenal cortex and adrenal medulla

adrenal cortex

tri-layered gland with each later synthesizing and secreting different hormones (superficial to deep layers)

• mineralcorticoids, glucocorticoids, gonadocorticoids

• zone glomerulosa, zona fasciculata, zona reticularis

mineralcorticoids

regulate electrolyte concentrations

• aldosterone

aldosterone

stimulates sodium reabsorption and potassium elimination to increase BP and blood volume

glucocorticoids

influence metabolism of most cells and help resist stressors; keep glucose levels constant

• cortisol

cortisol

main glucocorticoid; increases blood glucose, fatty acids, & amino acids; triggers new glucose formation in liver (gluconeogenesis)

gonadocorticoids

adrenal sex hormones (androgens) converted to testosterone in tissue cells

• contributes to onset of puberty & secondary sec characteristics, sex drive in women, estrogen in postmenopausal women

adrenal medulla

nervous tissue tying in with sympathetic nervous system

• responsible for the secretion of catecholamines

catecholamines

epinephrine and norepinephrine

epinephrine

metabolic effects (bronchodilation, blood flow redirection, increased HR, increased blood glucose)

norepinephrine

cardiac effects (peripheral vasoconstriction, increased BP)

cushing’s disease

hypersecretions of cortisol caused by tumor on pituitary, lungs, pancreas, kidney, or adrenal cortex

• depresses bone/ cartilage formation and immune system, inhibits inflammation, disrupts neural, CV & GI function

• signs: “moon” & “buffalo hump”

• can also be caused by excessive corticosteroid use

addison’s disease

hyposecretion of both gluco- and mineralcorticoids

• low plasma glucose and sodium levels, weight loss, sever dehydration, hypotension, hypoglycemia

• early sign is bronzing skin due to elevated ACTH levels triggering elevated melanin production

adrenogenital syndrome (masculinization)

hypersecretion of androgens

• not noticeable in adult males, noticeable signs in females & pre-pubertal males

  • boys: early onset of puberty & presentation of secondary sex characteristics

  • females: bearding & masculine patterns of body hair; clitoris enlarges resembling small (faux) penis

pheochromocytoma

tumor causing hypersecretion of catecholamine leading to “uncontrolled” sympathetic response (fight or flight)

Pancreas

• triangular gland located partly behind the stomach

• has exocrine and endocrine cells

  • Acinar cells and islets of langerhans

acinar cells

exocrine cells located in the pancreas tail; produce pancreatic digestive enzymes

islets of langerhans

endocrine cells located in pancreas head; produce blood glucose-regulating hormones

• alpha islet cells

• beta islet cells

alpha islet cells

produce glucagon to raise blood sugar

• stimulates liver glycogenolysis & gluconeogenesis

beta islet cells

produce insulin to lower blood sugar

• stimulates glucose transport from blood into cells

diabetes mellitus

• “sweet urine”

• caused by insulin hyposecretion (Type 1) and insulin hypoactivity (Type 2)

Type I diabetes mellitus

• insulin hyposecretion

• lack of faulty beta cells

• always insulin dependent

Type II diabetes mellitus

• insulin hypoactivity

• cells have become desensitized to insulin; insulin receptors down-regulated

• can become insulin-dependent if diet, exercise, or other inventions fail

ketones

acidic compounds formed from fat metabolism when cell’s sugars are too low

• can be used as alternative fuel from glucose

ketoacidosis

buildup of ketones

• if untreated can lead to hyperpnea, disrupted heart & O₂ transport activites, depression of nervous system leading to coma or death

hyperpnea

excess air intake during breathing

• sometimes caused by untreated ketoacidosis

gonads

produce the sex hormones

• ovaries

• testes

• placenta

Ovaries

produce estrogen and progesterone

estrogen

responsible for maturation of reproductive organs & appearance of secondary sex characteristics

progesterone

acts with estrogen to stimulate breast development & the uterine cycle of menstruation

Testes

produces testosterone

testosterone

• initiates maturation of male reproductive organs and appearance of secondary sex characteristics

• also develops sex drive and is necessary for sperm production

placenta

produces estrogen, progesterone, & human chorionic gonadotropin (hCG)

• important for fetal growth & development

blood

• opaque fluid with metallic taste

• only fluid tissue in the body

Brighter red blood

oxygenated, arterial blood

Darker red blood

deoxygenated, venous blood

Blood’s major functions

• Transport

• Regulation

• Protection

Transport (blood function)

• deliver O₂ & nutrients top body cells

• carry metabolic wastes

  • CO₂ to lungs; other products to kidneys for filtration and elimination

• carry hormones from endocrine organs to target cells

regulation (blood function)

• maintain body temperature by absorbing distributing heat

  • dilation and constriction of peripheral vessels

• buffering factors maintain pH

• maintain adequate fluid volume in circulatory system

  • helps maintain and facilitate all blood functions

protection (blood function)

• prevent blood loss via clotting factors and platelets

• prevent infection via circulating immune cells

plasma

• 90% water with >100 dissolved solutes

• other 10%:

  • electrolytes, gases, hormones, water, nutrients

  • plasma proteins are most abundant solutes

    • Albumin

    • globulin

    • fibrinogen

albumin

60% of plasma proteins and contributes to maintaining plasma osmotic pressure

• plasma protein

globulin

aids in formation of antibodies

• plasma protein

fibrinogen

main clotting proteins

• plasma protein

Erythrocytes

oxygen carrying red blood cells (RBCs)