Hormonal Communication

define hormone

substance secreted by an endocrine gland carried in the blood plasma to another body part

define endocrine gland

gland that secretes substances to the bloodstream (inside)

define exocrine gland

gland that secretes substances into a duct (tube)

define target cells

cells with receptors embedded in their plasma membrane that are complementary to specific hormone molecules

endocrine communication by hormones process

1) hormone secreted from endocrine gland. 2) hormone transported in blood plasma. 3) hormone diffuses out of the blood (fenestrations in blood vessel wall). 4) hormone binds to specific receptors on a target cell’s membrane or specific receptors in the cytoplasm of a target cell’s membrane. 5) once bound the hormone stimulates the target cell to produce a response

2 types of hormones

steriod and non-steriod

steriod hormones

hormone that is lipid-soluble and can pass through plasma membranes (sometimes nuclear membranes too like in the case of oestrogen)

the way steroid hormones cause effect on a target cell

bind to steroid hormone receptors in cytoplasm or nucleus forming a hormone-receptor complex which acts as a transcription factor (either facilitating/inhibiting the transcription of a specific gene in the target cell’s DNA)

non-steroid hormones

hormones that are hydrophilic and cannot pass directly through plasma membrane

the way non-steroid hormones cause effect on a target cell

bind to specific receptors on plasma membrane of target cell, binding triggers a cascade reaction mediated by secondary messengers (chemicals)

example of endocrine glands

adrenal glands

hormones secreted by the cortex

produces hormones vital to life, 3 main types of hormones it secretes: mineralocorticoids, glucocorticoids, androgens

hormones secreted by the medulla

produces non-essential hormones like adrenaline that help the body react to stress

function of the adrenal cortex

produce essential hormones like cortisol and aldosterone

structure of adrenal cortex

outer regions

structure of adrenal medulla

inner region

structure of adrenal gland capsule

thin, outer connective tissues

structure of adrenal glands

capsule, adrenal cortex, adrenal medulla

action of adrenaline

secreted by adrenal medulla. target organs: sinoatrial node in the heart, iris, alimentary canal (digestive tract from mouth to bum), liver. adrenaline triggers the body’s fight or flight response

increased heart rate purpose as a fight or flight response

pump more oxygenated blood around the body

pupils dilate purpose as a fight or flight response

take in as much light as possible for better vision

arterioles in skin contract purpose as a fight or flight response

more blood pumped to major muscle groups like the brain and heart

blood glucose levels rise purpose as a fight or flight response

increase respiration to provide energy for muscle contraction

smooth muscle of airways relax purpose as a fight or flight response

allow more oxygen to reach the lungs

non-essential systems shut down purpose as a fight or flight response

focus organs on emergency functions like muscles for fighting

difficulty focussing on small tasks purpose as a fight or flight response

brain solely focuses on the threat

increased ventilation rate and depth purpose as a fight or flight response

increase the removal of carbon dioxide and supply of oxygen

endorphins are released into the brain purpose as a fight or flight response

natural painkillers that may be required in situations of damage/injury

sweat production increases purpose as a fight or flight response

increased metabolism generates more heat that must be removed

mineralocorticoids function

control blood pressure by maintaining salt and water concentration balance in blood and bodily fluids

what is mineralocorticoids

(secreted by cortex) essential hormone. example=aldosterone. its release is mediated by signals triggered by the kidney

what is glucocorticoids

(secreted by cortex) essential hormone. examples= cortisol, corticosterone

glucocorticoids function

regulate metabolism by controlling how the body converts fats, proteins, carbohydrates into energy. regulate blood pressure and immune response. release of these hormones from the adrenal cortex is controlled by the hypothalamus

what is androgens

(secreted by cortex) essential hormone. example=androgen

androgen function

small amounts of male and female sex hormones are released. have a small impact but are especially important in women after menopause

how adrenaline takes effect in cells

adrenaline binds to its specific receptor on the plasma membrane of a liver cell - first messenger. the binding changes the receptor activating a G-protein which splits and combines with adenylyl cyclase enzyme. adenyl cyclase activates enzymes which convert ATP into cyclic AMP aka cAMP) - second messenger. cAMP binds to kinase (an enzyme) activated it. kinase activates other enzymes (by phosphorylating meaning adding phosphate group(s)) that convert glycogen into glucose

detection of hormones by target cells

target cells have specific receptors for hormone found on its plasma membrane. once the hormone binds to its receptor the target cell is stimulated and produces a response

what is an enzyme cascade

series of enzymes activated one after the other. for example adrenaline causes an enzyme cascade reaction that results in glycogen being converted into glucose

first messanger

hormone that binds to target cell because it carries the first signal. for example: adrenaline

second messenger

A molecule that relays a signal from a cell-surface receptor. for example: cAMP

cortisol

help regulate metabolism by controlling how the body converts fats, proteins, and carbohydrates into energy. helps regulate blood pressure and cardiovascular function in response to stress (flight or fight)

corticosterone

works with cortisol to regulate immune response and suppress inflammatory reactions

aldosterone

helps control blood pressure by maintaining the balance between salt and water concentrations in the blood and bodily fluids

androgens

small amounts of male and female sex hormones released by ovaries or testes

what hormones are released by the adrenal medulla

adrenaline and noradrenaline

function of the pancreas

exocrine gland and endocrine gland

pancreas role as an exocrine gland

acini produces digestive enzymes and alkaline pancreatic juice. the juice and enzymes are secreted into ducts leading to the pancreatic duct then are released into the duodenum

which parts of the pancreas are exocrine and endocrine tissue

exocrine - acini and ducts. endocrine - islet of Langerhans

pancreas role as an endocrine gland

the cells of the islet of Langerhans are responsible for producing insulin and glucagon.

3 important types of digestive enzymes produced by the pancreas and what they break down

amylase - breaks down starch into simple sugars, ie pancreatic amylase. proteases - break down proteins into amino acids, ie trypsin. lipases - break down lipids into fatty acids and glycerol, ie pancreatic lipase

endocrine pancreatic tissue (islet of Langerhans) characteristics

appearance = lightly stained, shape = large spherical clusters, type of tissue = endocrine pancreas, function = produce and secrete hormones

exocrine pancreatic tissue (acini) characteristics

appearance = darker stained, shape = small berry-like clusters, type of tissue = exocrine pancreas, function = produce and secrete digestive enzymes

types of cells inside the islets of Langerhans and what they secrete

alpha cells produce and secrete glucagon. beta cells produce and secrete insulin.

is alpha or beta cells larger

alpha cells are larger and more numerous than beta cells.

what colours do alpha and beta cells stain using differential staining

alpha cells stain pink. beta cells stain blue.

how does immunoperoxidase staining work

antibody binds to the antigen glucagon or insulin staining the cell. antibodies to glucagon are used to identify alpha cells (as alpha cells produce glucagon). antibodies to insulin are used to identify beta cells.