Endocrine Systems

endocrine cells secrete

hormones

30 hormones

chemical messengers released from endocrine glands

hormones are

chemical messengers

Hormones function

coordinate organismal responses

hormones function

control: rates of enzymatic reactions, transport of ions or molecules across cell membranes, gene expression and protein synthesis

target cells

have receptors for specific hormones

mechanisms of intercellular communication

direct, paracrine, endocrine, synaptic

direct communication

Exchange of ions and molecules between adjacent cells across gap junctions, Occurs between two cells of same type, Highly specialized and relatively rare

autocrine

a chemical signal that binds to and affects the cell that makes it

paracrines

chemical signals released into intercellular fluid and affecting nearby cells

endocrine cells release

hormones into the blood

endocrine and nervous system similarities

Their common goal is to maintain homeostasis by coordinating or regulating activities of cells, tissues, and organs. Both are regulated mainly by negative feedback.

the endocrine system

includes all the glands that secrete chemical messengers called hormones

endocrine cells release

secretions into extracellular fluid

endocrine organs are

scattered throughout the body

endocrine processes

The endocrine system releases hormones that enhance short-term adjustments and direct long-term changes in cardiovascular performance

Hypothalamus location

in the brain, below the thalamus

Hypothalamus produces

ADH, oxytocin, regulatory hormones

pituitary gland is located

base of the brain

pituitary gland anterior lobe produces

ACTH, TSH, GH, PRL, FSH, LH, MSH

pituitary gland posterior lobe releases

oxytocin and ADH

The pineal gland is located

brain

pineal gland releases

melatonin

parathyroid gland is located

posterior surface of the thyroid gland

parathyroid produces

parathyroid hormone

The thyroid gland is located

neck

thyroid produces

Thyroxine (T4), Triiodothyronine (T3), Calcitonin

Adrenal glands are located

on top of the kidneys

adrenal glands consists of

medulla and cortex

medulla produces

epinephrine and norepinephrine

cortex produces

cortisol, aldosterone, androgenic steroids

organs with secondary endocrine functions

heart, thymus, digestive tract, kidneys, gonads

heart releases

atrial natriuretic peptide (ANP)

thymus releases

thymosin and thymopoietin

The thymus undergoes involution during:

old age

adipose tissue releases

leptin

digestive tract secretes

numerous hormones involved in the coordination of system functions, glucose metabolism, and appetite

gonads

ovaries and testes

ovaries release

estrogen, progesterone, inhibin

testes release

testosterone and inhibin

binding of hormones may

Alter genetic activity, Alter the rate of protein synthesis, Change membrane permeability

Three classes of hormones

amino acid derivatives, peptide hormones, lipid derivatives

amino acids derivatives

Small like, amino acid structures. epinephrine, norepinephrine, thyroid, melatonin

tyrosine and tryptophan

both are amino acid precursors

derivatives of tyrosine

thyroid hormones and catecholamines

thyroid hormones are

T3 and T4

Catecholamines

dopamine, norepinephrine, epinephrine

derivatives of tryptophan

serotonin and melatonin

Peptide Derivatives

chain of amino acids (peptides and small proteins)

prohormone

A physiologically inactive precursor to a hormone

glycoproteins

Membrane carbohydrates that are covalently bonded to proteins.

anterior pituitary

adenohypophysis

Short chain polypeptides

Antidiuretic hormone (ADH) and oxytocin (OXT) (each 9 amino acids long)

small proteins

insulin, growth hormone, prolactin

lipid derivatives

eicosanoids and steroid hormones

eicosanoids

derivatives of 20-carbon fatty acids; biologically active compounds that help to regulate blood pressure, blood clotting, and other body functions

prostaglandins

Modified fatty acids that are produced by a wide range of cells.

steroid hormones

derived from cholesterol

androgens, estrogens, progesterone

sex hormones

adrenal gland releases

cortisol

Catecholamines and peptide hormones

not lipid soluble and cannot penetrate the plasma membrane; bind to receptor proteins on outer surface of plasma membrane called extracellular receptors

steroid and thyroid hormones

lipid soluble, diffuse across plasma membrane and bind to receptors inside cell (intracellular receptors)

Hormones move through

bloodstream

Hormones travel through

circulatory system

free hormones

-Remain functional for less than 1 hour, Diffuse out of bloodstream and bind to receptors on target cells, Are broken down and absorbed by cells of liver or kidneys, Are broken down by enzymes in plasma or interstitial fluids

hormone receptors

protein molecules located on the cell membrane, cytoplasm or nucleus

extracellular receptors

Hormones that are NOT LIPID soluable and are unable to penetrate a plasma membrane, instead these hormones bind to receptor proteins at the OUTER surface of the plasma membrane (extracellular receptors) EX: catecholamines and peptide hormones

first messenger

A water soluble hormone that binds to its receptor at the outer surface of the plasma membrane.

second messenger

A small, nonprotein, water-soluble molecule or ion, such as calcium ion or cyclic AMP, that relays a signal to a cell's interior in response to a signal received by a signal receptor protein.

G protein

A GTP-binding protein that relays signals from a plasma membrane signal receptor, known as a G protein-coupled receptor, to other signal transduction proteins inside the cell.

cAMP

cyclic adenosine monophosphate

intracellular receptors

receptors located inside the cell rather than on its cell membrane

hormone secretion

Controlled by negative feedback, Stimulus triggers production of hormone that reduces intensity of stimulus.

hypophysis

another name for the pituitary gland

growth hormone stimulates

Liver cells to release somatomedins that stimulate tissue growth (Somatomedins cause skeletal muscle fibers and other cells to increase uptake of amino acids), Stem cells in epithelia and connective tissues to divide, Breakdown of triglycerides in adipocytes, which leads to glucose-sparing effect, Breakdown of glycogen by liver cells causing diabetogenic effect

MSH (melanocyte stimulating hormone)

A hormone produced and secreted by the anterior pituitary that regulates the activity of pigment-containing cells in the skin of some vertebrates.

isthmus

connects the two lobes of the thyroid gland

thyroid follicles

manufacture, store, and secrete thyroid hormones

C (clear) cells

Secrete hormone calcitonin, aids in calcium regulation

Triiodothyronine (T3)

Contains three iodide ions

Thyroxine (T4)

contains 4 iodide ions

thyroid hormones

hormones produced by the thyroid gland primarily responsible for regulation of metabolism

calorigenic effect

allows an animal to generate heat/maintain a constant body temperature by increasing their metabolism; production of thyroid hormone increases with exposure to cold temperatures

thyroid hormones bind to

intracellular receptors

thyroid hormones in children

essential to normal development of skeletal, muscular, and nervous systems

c cells

produce calcitonin

Calcitonin helps regulate

calcium homeostasis

calcitonin prevents

hypercalcemia

Hypercalcemia

excessive calcium in the blood

effect of thyroid hormones

set the basal metabolic rate, thermoregulation, growth and development, synergism with the SNS

parathyroid gland structure

*4 oval bodies*, 2 *superior* on poles, 2 *inferior* on poles

parathyroid hormone (PTH)

increases blood Ca2+ involved in bone maintenance

Effects of Parathyroid Hormone

stimulates osteoclasts and inhibits osteoblasts: accelerates mineral turnover and releases calcium from bone, reduces rate of calcium deposition in bone; enhances reabsorption of calcium at kidneys, reducing urinary losses; stimulates formation and secretion of calcitriol by the kidneys: effects complement or enhance PTH and enhances calcium and phosphate absorption by digestive tract

adrenal cortex is divided into

zona glomerulosa, zona fasciculata, zona reticularis

zona glomerulosa

outer region of adrenal cortex

zona glomerulosa secretes

aldosterone

Aldosterone

"salt-retaining hormone" which promotes the retention of Na+ by the kidneys. na+ retention promotes water retention, which promotes a higher blood volume and pressure

zona fasciculata

glucocorticoids (cortisol)

zona fasciculata secretes

glucocorticoids

Glucocorticoids

raises blood sugar levels