endocrine ch 17

endocrine system

Composed of endocrine glands throughout the body

hormones

molecules that communicate with and control body cells; process is done via receptors on target cells

target cells

target cells have various specific receptors for specific hormones (skeletal muscle cells & testosterone) (osteoblasts for parathyroid hormone)

endocrine system communication methods

glands lack ducts & release to surrounding environment

hormones travel via blood circulation to all body tissues

hormones randomly leave blood into interstitial fluid

hormones bind to target cell receptors (may start or stop metabolic activities)

endocrine vs nervous system

Endocrine is slower but lasts longer, slower reaction time, secrete hormones, widespread effects on body and target any cell with receptors

they are COMPLIMENTARY

functions of endocrine

regulate development (cell division & differentiation), growth, and metabolism (metabolic activities, anabolic & catabolic processes)

control digestive processes (secretory & motility process)

maintain homeostasis of blood vol. and comp. (regulate substances dissolved in blood)

control reproductive activities

endocrine glands

connective tissue framework & house/support epithelial tissue that will produce & release hormones from secretory cells

secretory cells are organized(?)

single organ with only endocrine function

cells in small clusters within organs with other primary function (pancreas)

endocrine organs

thyroid gland, pituitary gland, sex glands, adrenal glands, pancreas, parathyroid glands

hormonal stimulation

release of a hormone in response to another hormone

ex: anterior pituitary releases TSH (thyroid stimulating hormone) to release TH

humoral stimulation

release of a hormone in response to changes in level of nutrient or ion in the blood.

ex: insulin & glucagon (alpha & beta cells)

nervous system stimulation

release of a hormone in response to stimulation by the nervous system.

ex: norepinephrine & epinephrine in adrenal medulla

alpha cell

secretes glucagon to increase blood glucose levels

beta cell

Secretes insulin to lower blood glucose.

adrenal medulla

secretes epinephrine and norepinephrine & is endocrine out. inner medulla is nervous system

circulating hormones

circulate blood throughout the body

Steroids

- circulating hormone & building block for cholesterol

- lipid soluble (sustain itself in water & mix well w/fatty substances)

Biochemical amines & proteins

- circulating hormones & building block for amino acids

- water soluble

synthesized within endocrine cells from

cholesterol or amino acids

local hormones

large group of signaling molecules that do not circulate within the blood & either auto or para stimulation

Autocrine stimulation

synthesize/release hormones that bind to itself

Paracrine stimulation

synthesize/release hormones that behind to neighboring cells

Eicosanoids

- primary type of local hormones

- can be synthesized throughout the body

Prostaglandins

vasodilator (part of inflammatory response)

Thromboxanes and Leukotrienes

vasoconstrictors (prevent blood loss)

carrier proteins (transporters)

attach to lipid soluble hormones to help circulate bloodstream & can either be really picky (only binding to specific lipid soluble molecules ex: thyroxine-binding globulin)

or nonselective (ex: albumin)

blood plasma

pale yellow fluid portion of whole blood that consists of water

bound hormones

- thyroid and steroid hormones w/ carrier/transport protein

- remain bound in circulation much longer because they are attached to carrier proteins & may be used much later when needed

unbound hormone (free hormone)

a hormone that is not attached to a carrier/transport protein & can leave blood and bind to cell receptors of target organs

blood concentration

dependent on physiologic effect of hormones

Hyperthyroidism

excess production of thyroid hormone

(increased metabolic rate, weight loss, heat intolerance)

Hypothyroidism

decreased production of thyroid hormone

(low metabolic rate, weight gain, photophobia, lethargy)

hormone release vs elimination

2 primary factors that influence hormone concentration

hormone release

- positive correlation w/ hormone concentration

increased release = increased blood concentration

decreased release = decreased blood concentration

hormone elimination

- negative correlation w/ hormone concentration

faster rate of elimination = lower blood concentration

slower rate of elimination = higher blood concentration

how does hormone elimination occur?

•Enzymatic degradation in liver cells

•Removal from blood via kidney excretion or target cell uptake

•The faster the elimination rate, the lower the blood concentration and vice versa

how do we maintain homeostatic hormone levels?

negative feedback (insulin vs. glucagon)

lipid soluble hormones

- non polar molecules & lipophilic

- once entering, they form hormone receptor complex

Hormone-Receptor Complex

Binding of hormone to its specific receptor.

hormone response element (HRE)

DNA sequence where hormone-receptor complex binds.

What does the hormone receptor complex bind to?

Hormone response element

What is the result of the hormone receptor complex binding to the hormone response element?

Leads to mRNA transcription

What occurs after mRNA transcription?

mRNA translation where the specific protein is synthesized

What can new proteins synthesized from mRNA do?

Alter cell structure or shift cell metabolic activity

What type of proteins can shift cell metabolic activity?

Enzymes

water soluble hormones

- polar molecules (unable to diffuse across plasma membrane)

How do water-soluble hormones stimulate?

bind via plasma membrane receptor to initiate signal transduction pathway

- hormone 1st messenger

- hormone + receptor = 2nd messenger synthesis

signal transduction pathway

A series of steps linking a mechanical, chemical, or electrical stimulus to a specific cellular response.

2nd messenger

within the cell & modifies cellular activties

actions of water soluble hormones

- enzymes can be activated or inhibited

- growth can be stimulated (cell division)

- cellular secretions can be released

- membrane ion permeability can be changed

- muscles can be contracted or relaxed

g protein

signal trasduction pathways function through

Adenylate cyclase activity

•After hormone (e.g., glucagon) binds to its receptor, G protein is activated

•Activated G protein activates adenylate cyclase

•Adenylate cyclase generates cAMP

•cAMP activates a protein kinase (protein kinase A)

•Protein kinase A phosphorylates other molecules (activating or inhibiting them)

G protein activation

Receptor binding to a G protein and the G protein causing a GTP to displace the GDP (when the receptor is appropriately activated)

water soluble vs lipid soluble hormone

water goes initiates signal transduction & lipid goes through HRC and HRE

up-regulation

# of receptors increase to make the cell more sensitive to a hormone

down regulation

# of receptors decrease to make the cell less sensitive to a hormone

synergistic

hormones work together to produce greater effect (estrogen, progesterone & oxytocin)

permissive

1st hormone allows action of 2nd hormone (prolactin & oxytocin)

antagonistic

1 hormone causes opposite effect of another hormone (insulin & glucagon)

What is the master control of the autonomic nervous system?

Hypothalamus - influences HR, BP, digestive activities, & respiration

What is the master control of the endocrine system?

Hypothalamus - oversees most of the endocrine system's functions

What regulates body temperature?

Hypothalamus

What controls emotional behavior?

Hypothalamus

What regulates the hunger drive?

Hypothalamus

What regulates the thirst drive?

Hypothalamus

What regulates sleep/wake rhythms (circadian)?

Hypothalamus

T.P. F.L.A.G.- Anterior Pituitary Hormones

Thyroid stimulating, prolactin, follicle stimulating, luteinizing, adrenocorticotropic, growth hormones

A.O Posterior Pituitary Hormones

Antidiuretic and oxytocin hormones

glucogeneogenesis

formation of glucose

glycolysis

the breakdown of glucose by enzymes, releasing energy and pyruvic acid.

take nutrients out

glucagon

grow tissues

growth hormone

metabolic activity

antidiuretic

paraventricular nucleus

produces oxytocin

supraoptic nucleus

produces antidiuretic hormone (ADH) primarily

hypothalamo-hypophyseal tract

neural connection between the hypothalamus and the posterior pituitary

infundibulum

A stalk that attaches the pituitary gland to the hypothalamus.

What is another name for the posterior pituitary gland?

Neurohypophysis

What type of tissue makes up the posterior pituitary gland?

Nervous tissue/neurons

Which two hormones are stored and secreted by the posterior pituitary gland?

Oxytocin and ADH

How is the posterior pituitary gland controlled?

By action potentials from the hypothalamus

hypothalamo-hypophyseal portal system

A vascular system that transports releasing and inhibiting hormones from the hypothalamus to the anterior pituitary

releasing hormones of the hypothalamus

- thyrotropin-releasing hormone (TRH)

- prolactin-releasing hormone (PRH)

- gonadotropin-releasing hormone (GnRH)

- corticotropin-releasing hormone (CRH)

- growth hormone-releasing hormone (GHRH).

Inhibiting hormones of the hypothalamus

prolactin inhibiting hormone (PIH), growth hormone inhibiting hormone (GIH)

PG

tropic hormones

hormones that stimulate other glands to release their hormones

-TFLA only not PG

growth hormone & hormonal stimulation

GH releasing from hypothalamus acts on anterior pit. gland to release GH

GH primarily acts on liver to release insulin growth factors (IGF)

IGF last longer in blood stream & increase response from target cell so increased hormone levels

GH effects muscle, bone, all cells

- amino acids

- increased growth, amino acid uptake which results in protein synthesis, stimulated cellular division, cell differentiation

GH effects liver

-increases gluconeogenesis, glycogenolysis

-decreased glycogenesis

Glycogenolysis

breakdown of glycogen to glucose

Glycogenesis

formation of glycogen from glucose

GH effects adipose connective tissue

- increased lipolysis

- decreased lipogenesis

thyroid gland

endocrine gland that surrounds the trachea in the neck & highly vascularized

anatomy of thyroid gland

thyroid follicles

- wall of each follicle = simple cuboidal epithelium called follicular cells surround central lumen

colloid

lumen houses viscous, protein rich fluid (gelatin fluid)

follicular cells

secrete thyroid hormone

parafollicular cells

secrete calcitonin

What stimulates the hypothalamus to release thyrotropin-releasing hormone (TRH)?

Decreased thyroid hormone, cold weather, pregnancy, high altitude, and hypoglycemia.

What hormone does the hypothalamus release in response to stimuli?

Thyrotropin-releasing hormone (TRH).

What does TRH stimulate the anterior pituitary to release?

Thyroid-stimulating hormone (TSH).

What is the role of thyroid-stimulating hormone (TSH)?

It stimulates the thyroid gland to release thyroid hormone (TH) into the blood.