a&P chapter 1 endocrine system

neuroendocrine organs

hypothalamus, pineal gland, posterior pituitary gland, adrenal medulla

what is the function of neuroendocrine organs

links brain to endocrine system - secreting hormones directly into blood

endocrine organs

Anterior pituitary gland, thyroid gland, parathyroid glands, thymus gland, adrenal cortex, pancreas, kidneys, ovaries, and testes, and heart

endocrine vs. Nervous system

• uses bloodstream and uses receptors - (located in target cells that are specialized proteins that bind to that hormones

  • no bloodstream - links directly to cell

types of pathway and function

endocrine -endocrine cell does long distance communication where hormones travel bloodstream to distant cell

paracrine - tissue cell does short distance communication of paracrine chemical in the extracellular fluid to nearby cell

Autocrine - specialized cell when autocrine chemicals travel though Extracellular fluid to same type of cell

differences in views of thyroid and parathyroid gland

• anterior view has nodules

  • posterior view has 3-8 parathyroid glands (dots)

which gland makes melatonin

pineal gland

difference in function of adrenal cortex and adrenal medulla

• cortex makes hormones

• medulla makes epinephrine (flight or fight)

  • located on the kidneys

2 types of pancreas and function

endocrine - regulates blood sugar by hormone - insulin

exocrine - digestive enzymes

Free hormones

small, amino acid—based hormones that are able to freely reavel though blood (hydrophilic)

Bound hormones

complexes with binding proteins that allow hydrophobic hormones to travel through blood

up-regulation

target cells produce and display greater number of receptors

• hormone in blood declines, cells sensitivity to hormones increase

  • also can occur in response to temporary increase in hormone level in blood

down-regulation

target cells decrease number of receptors in response to prolonged exposure to high level of hormone in blood

First messengers

hydrophilic hormones binds to receptor in plasma membrane

(external signal)

second messengers

amplify signals from cell-surface receptors to targets insides of the cell

MECHANISMS OF HORMONE ACTION

hydrophobic hormone through cell membrane → binds to intracellular receptor located on cytosol → hormone + receptor enter nuclear and attach to DNA

amino acid-based hormones

made from amino acids, generally hydrophilic, include amines, peptides, and proteins

• bind to receptors on the plasma membrane

steroid hormones

made of cholesterol, always hydrophobic, bind to receptors in the cell, either in the cytosol or nucleus

Target cell

cell that responds to a specific hormone

• must have a specific receptor for a hormone

• must bind to the receptor and cause a response in the cell

Half-life

amount of time it takes for the concertation of a hormone in the blood to decrease by half

Half life in hydrophobic and hydrophilic molecules

Hydrophobic - have longer half-life because they bind to bound proteins helping transport through watery portion of blood

• weeks to more

Hydrophilic - shorter life span because they travel freely in plasma

• few minutes to seconds

hormone clearance

how fast the hormone is removed from the blood

• mainly by kidney and liver, also can be in target cells by reaction catalyzed by enzymes

maintaining homeostasis - negative feed back loop

1. Stimulus regulated physiological variable drops under normal range

2. receptors on endocrine cells detect the deviation of the variable

3. Control Center - stimulated control center ( often the endocrine cell) increases or decreases its secretion depending on the hormone

4. Effector/resposnse - the hormone triggers a response in its target cells that moves conditions towards the normal range

• at the variable returns into the normal range, effector and control center decrease the effectors response

tropic hormones

controls secretion of hormones from other endocrine glands

trophic hormones

induce growth in target cells

Anterior pituitary (adenohypophysis)

made of glandular epithelial tissue. producing its own hormones and is regulated by releasing and inhibiting hormones from the hypothalamus through the hypothalamic-hypophyseal portal system

hypothalamic-hypophyseal portal system

specialized blood supply; allows both hypothalamus and pituitary to deliver hormones directly to target cells

• tiny capillaries merge at hypothalamus; form larger portal veins that travel through the infundibulum

  • portal veins lead to second group of capillaries in anterior pituitary gland

Posterior pituitary (neurohypophysis)

Made of nervous tissue. doesn’t produced hormones; instead stores two neurohormones and releases ADH and oxytocin, which are produced by the hypothalamus

ADH (antidiuretic hormone)

produced by the hypothalamus and stored and released by the posterior pituitary/neurohypophysis

• causes kidneys to retain water by inserting aquaporins into kidney tubule cells. Helps maintain water balance

Aldosterone

main mineralocorticoid produced by the adrenal cortex. helps regulate sodium, potassium, extracellular fluid volume and blood pressure.

• causes kidneys to retain sodium and excrete potassium, increasing water retention and maintain blood pressure.

  • major stimuli is high blood potassium, low ph and angiotensin 2

ANH (atrial natriuretic hormone)

helps regulate blood pressure and blood volume

• released when bp/ blood vol. is too high

• promotes sodium and water loss by the kidneys, which decrease blood volume

water maintenance by kidneys — what hormones and what they do

ADH - causes the kidneys to retain water, increasing water reabsorption

Aldosterone - causes the kidneys to retain sodium and excrete potassium; water follows sodium, increasing fluid volume

ANH - causes kidneys to excrete sodium and water, decreasing blood volume and BP

Oxytocin

produced by the hypothalamus and stored in posterior pituitary/neurohypophysis. targets mammary glands and uterine smooth muscle. causes milk ejection during breastfeeding and uterine contractions

• milk → positive feedback loop

Hypothalamus

connects endocrine to nervous system and regulates the pituitary gland. Produces ADH and oxytocin. Produces releasing (stimulate) and inhibiting TROPIC hormones that regulate the anterior pituitary

Diabetes insipidus

caused by the lack of ADH secretion or activity

• extreme thrist and signs of dehydration; body can’t conserve most of water consumed

hormone pathway

• first tier - hypothalamus - releasing hormone that tells the anterior pituitary what to do

• second tier - anterior pituitary - releases a tropic hormone. hormone travels to and stimulates another endocrine gland

• third tier - target cell/gland - target gland releases its hormone. produces the final effect on the body and helps regulate the original stimulus through negative feedback

  • Hypothalamus → pituitary → target gland

TRH ( thyrotropin-releasing hormone)

helps maintain metabolic homeostasis by stimulating the anterior pituitary to release TSH

• TSH stimulates the thyroid to produce T3 and T4, which regulates metabolic rate and body temp. Rising T3/T4 provide negative feedback loop to reduce TRH and TSH

• thyroid hormone are the target organ hormone

CRH (corticotropin-releasing hormone)

helps maintain stress and metabolic homeostasis by stimulating the anterior pituitary to release ACTH (adeno-cortico-tropic hormone)

• stimulate the adrenal cortex to produce cortisol, which helps respond to stress and regulate blood glucose

• glucocorticoids - regulate blood glucose and help with stress

PRH (Prolactin-releasing hormone)

PRH stimulates the anterior pituitary to release prolactin (PRL). promotes milk production in the mammary glands, helps maintain the physiological processes needed for breastfeeding

GnRH (gonadotropin-releasing hormone)

GnRH stimulates the anterior pituitary to release LH (luteinizing hormone) and FSH (Follicle-stimulating hormones) stimulates the gonads to produce sex steroids and support reproductive cell development

• testosterone and estrogen

GHRH (growth hormone-releasing hormone)

• stimulate the anterior pituitary to release growth hormone. regulate growth, metabolism, in liver, muscle, bones, and fat

  • IGF (insulin-like growth factor) is primary chemical messenger that growth hormone uses to stimulate growth

Somatostatin

acts as an inhibitor that stops the pituitary gland from releasing growth hormone

• promotion of far breakdown, increase of blood glucose and fatty acid levels; can be used for fuel and raw materials for growth

Gigantism

hypersecretion of GH before epiphyseal plates have closed; developed in youth also increases heart size

Acromegaly

hypersecretion of GH after epiphyseal plate has closed; (big ears, head, hands, and feet, as well as liver and heart; progressively distorts organ; can lead to heart failure

• developed after youth

Pituitary dwarfism

condition of hyposecretion of GH; leads to individuals that are short in stature

structures of thyroid and parathyroid glands

Collids - protein rich, gelatinous material; contains precursor for thyroid hormone and high concentration of iodine atoms
Parafollicular cells - spaces between adjacent thyroid follicles; large cells that produce hormone calcitonin

Parathyroid glands

3-5 separate glands located on the posterior surface of the thyroid; secretes parathyroid hormones from chief cells (regulate blood calcium levels)

thyroid hormones

• set basal metabolic rate (amount of energy required by body at rest)

Increases ATP consumption by increasing

• Synthesis of NA+/K+ pump

• Gluconeogenesis ( breakdown of proteins in muscles and fat in fat tissue)

• homeostasis of body temp

  • all of these produces heat maintaining thermoregulation

composition of thyroid hormones (T4 and T3)

Thyroglobulin - large thyroid hormone precursor protein (secreted in the colloids)

iodide ions - converted to iodine atoms that attach to thyroglobulin (secreted in the colloids)

• iodinated thyroglobulin enters follicle cells and are converted into T3 and T4

• T4 (less active) contains 4 iodine atoms while T3 (more active 10% of thyroid hormones) contains 3 iodine atoms

  • t4 can be converted into t3 by the removal of a iodine atom

hyperthyroidism

overproduction of thyroid hormones, development of goiters and exophthalmos (inability to calm down)

Graves disease vs Hashimoto thyroiditis

most common, autoimmune system produces antibodies mimicking TSH stimulating the thyroid gland ( bulging of eyes can occur)

• goiter occur to overstimulation by antibodies, causing entire thyroid to become enlarged (usually smoother)

Hashimoto - antibodies go to thyroid and attack thyroid tissue

• Goiter occur due to inflammation from thyroid tissue damage

Congenital hypothyroidism

baby born with inadequate thyroid function; leading to delayed physical and nervous system development

why are thyroid disorders more common in places of poverty

nutrient deficiency leading to lack of iodine → T3/T4 production decreases, TSH (thyroid stimulating hormone) increases leading to goiter

Parathyroid hormone (PTH)

is released by the parathyroid glands when blood CA2+ levels are too low

what are the 3 ways that PTH parathyroid hormone raises blood CA2+

bones - stimulate bone breakdown (osteoclasts) → releases Ca2+ into the blood

kidneys - increase Ca2+ reabsorption → less Ca2+ is lost in urine

Vitamin D - stimulates the kidneys to activate vitamin D → increases Ca2+ absorption from the intestines

Osteoporosis

characterized by decrease in mineral density of bones; results in weak bones, increase in bone fractures

Calcitonin

hormone produced by the parafollicular cells of the thyroid when blood Ca2+ levels are too high

adrenal glands

on superior aspect of each kidney

• Cortex - typical endocrine gland

  • medulla - neuroendocrine organ that secretes neurohormones

3 layers of the adrenal cortex and functions

Zona glomerulosa → produces aldosterone from mineralocorticoid

• aldosterone regulates Na+ and K+ and maintains bp and blood vol, and pH homeostasis (kidneys)

Zona fasciculata - produces cortisol from glucocorticoids and testosterone and estrogen from androgenic steroids

• regulates blood glucose and body’s stress response (throughout body for stress and metabolism)

Zona reticularis - produces adrenal androgens for sexual development

• produces sex hormones (gonads)

  • released throughout the bloodstream but target specific organs

hypersecretion of aldosterone can lead to

hypokalemia - (low blood potassium ion levels) likely to have high blood pressure because depleted levels of potassium mean increased levels of sodium

Hypernatremia - (high blood sodium ion levels) high salt low potassium

• both can lead to hypertension (high blood pressure)

  • aldosterone activates sodium potassium pump

Stress response

stress causes the body to release cortisol from the adrenal cortex, signaling the liver to make more glucose.

• liver performs gluconeogenesis ( making glucose from non-carbs) helping maintain normal blood glucose

  • during stress, cortisol increase this to provide extra glucose for energy

    • Chronic stress (Cortisol) can lead to high blood glucose which damages blood vessels

Cushing’s disease

too much cortisol → increased blood glucose, weight gain, high BP, muscle weakness

• loss of muscles for energy

Addison’s disease

too little cortisol (often too little aldosterone)

• low blood glucose, weight loss, low Bp, weakness

  • opposite of Cushing’s disease

what glands produce estrogen

ovaries, adrenal glands and adipose tissue w

What glands produce testosterone

testes, ovaries, and adrenal glands

pancreas

club-shaped organ in abdominal cavity

• endocrine - releases hormones directly into the bloodstream

  • Islets of langerhans - (islands) secrete hormones into bloodstream

    • exocrine - releases digestive enzymes into the small intestines through ducts (acinar cells), enzymes help break down macronutrients

Pancreatic islets main cells

Alpha cells - secrete glucagon - increase levels of glucose and metabolic fuels in blood

• glycogenolysis and gluconeogenesis

Beta cells - secrete insulin

Delta cells - secrete somatostatin

glucagon

breakdown of proteins in muscle tissue to release amino acids for gluconeogenesis

• release of fat from adipose for fuel to be used during gluconeogenesis

Ketoacidosis

breakdown of fat lowering blood pH

Insulin

hormone produced by beta cells in the endocrine pancreas that lowers blood glucose

• released when blood glucose is high

  • promotes storage of glucose as glycogen

hypoglycemia

blood glucose levels are too low; can be caused by elevated insulin levels

• diabetes

Type 1 diabetes (insulin dependent)

caused by the destruction of beta cells (cannot secrete insulin) causing glucose to stay in blood instead of entering cells.

• requires insulin replacements

• glucose and ketones exit body through urine can cause polyuria (frequent urination) and polydipsia (excessive thirst)

  • born with also known as early onset/childhood diabetes

type 2 diabetes

body becomes resistant to insulin, body don’t respond to insulin properly. Pancreas

• generally produce enough insulin to prevent ketoacidosis (breakdown of fat lower body pH)

• associated with genetics and obesity

  • also known as adult/late onset

peripheral neuropathy in diabetes patients

chronically high blood glucose can damage nerves outside of the brain and spinal nerve (peripheral nerves) often affecting feet and hands (numbness)

• high blood glucose damages the small blood vessels and feet and hands are the furthest from heart receiving poorly oxygenated blood and overtime causing nerve damage

endocrine vs nervous system

Endocrine System	Nervous System

Signal

Hormones

Electrical impulses + neurotransmitters

How signals travel

Through the bloodstream

Along neurons

Speed

Slower

Very fast

Duration

Effects usually last longer

Effects usually shorter

Target

Can affect many cells/tissues with the correct receptor

Usually affects specific target cells

Main functions

Growth, metabolism, reproduction, stress, and homeostasis

Sensation, movement, coordination, and rapid responses

Processes the endocrine system controls or regulates

• Metabolism – controls how the body uses energy.

• Growth and development – regulates body growth and tissue development.

• Blood glucose – insulin and glucagon maintain blood sugar levels.

• Blood calcium – PTH and calcitonin regulate Ca²⁺ levels.

• Water and electrolyte balance – hormones regulate water, Na⁺, and K⁺ levels.

• Stress response – cortisol helps the body respond to stress.

• Reproduction – regulates sexual development and reproductive functions.

• Body temperature – thyroid hormones help regulate metabolic heat production.

HPT Axis function

hypothalamus releases TRH ( thyroid releasing hormone) → pituitary releases TSH thyroid stimulating hormones → thyroid releases t3/t4 → regulates metabolism, growth, and development