hormones Flashcards
define endocrine gland
an organ that secretes hormones directly into the blood
define exocrine gland
a gland that secretes something into a duct
define target tissue
a group of cells that contain receptors for a particular hormone and are therefore affected by it
explain the meaning of the term first messenger with ref to adrenaline and cyclic AMP
a molecule that binds to a receptor in the plasma membrane and causes changes to happen in the cell; adrenaline is an example
explain the meaning of the term second messenger with ref to adrenaline and cyclic AMP
a molecule that is affected by the binding of a first messenger to a receptor, cAMP is an example of a second messenger.
how do hormones affect their target cells
by attaching to a specific receptor molecule, which sets into action a series of events within the cell, an example of cell signalling
what is adrenaline
a hormone synthesised from amino acids,not soluble in lipids.
is a catecholamine.
what are adrenalines target cells
liver
muscle
have receptors in their plasma membrane which adrenaline binds to- this alters the shape of the receptor, causing it to interact with another protein in the membrane called a G-protein
what happens to the G protein once adrenaline has bound
g protein splits, one part combines with an inactive enzyme called adenylyl cyclase- this activates the enzyme which converts ATP to cyclic AMP (cAMP)
describe the functions of the adrenal glands
adrenline secreted from them in response to excitement, danger or stress. target organs and tissues include the SAN in the heart, smooth muscle in the wall of the alimentary canal and the muscles in the iris of the eye.
it brings about changes that prepare the body for vigorous activity, for escaping from danger or fighting against it
how does the pancras act as both an exocrine and endocrine gland?
exocrine: secretion of pancreatic juice- which flows along the pancreatic duct into the duodenum- this juice contains enzymes:
lipase, amylase, trypsin
lipase
catalyses the hydrolysis of lipids to fatty acids and glycerol
amylase
catalyses the hydrolysis of starch to maltose
trypsin
catalyses the hydrolysis of proteins to polypeptides
what are the islets of langerhan
patches of endocrine tissues scattered throughout the exocrine tissue of th pancreas (form about 15% of the pancreas) contain alpha and beta cells
alpha cell
secrete glucagon hormone
beta cell
secrete insulin hormone
how do alpha and beta cells detect changes to blood glucose concentration
by having receptors in their plasma cell surface membrane that detect these changes
explain how blood glucose conc is regulated when the plasma glucose conc RISES
- both alpha and beta cells detect the rising con of glucose
- alpha cells cease to secrete glucose but beta cells secrete insulin
- insulin binds with receptors in the plasma cell surface membranes of muscles fat and liver cells
- glucose uptake from the blood by these cells is increased
- use of glucose in respiration by cells is increased
- liver cells convert glucose to glycogen and stop the reverse reaction.
explain how blood glucose conc is regulated when the plamsa glucose conc FALLS
- both alpha and beta cells detect the falling conc of glucose
- beta cells cease to secrete insulin
- alpha cells secrete glucagon
- target cells the up less glucose
- the rate of glucose use decreases and fats or amino acids are used in respiration instead.
- glycogen in the liver is converted to glucose and released into the blood.
outline how insulin secretion is controlled with ref to potassium channels and calcium channels in betacells
beta cell- resting potential across it membrane is kept negative inside the cell by ATP sensitive potassium ion channels
when blood glucose rises, glucose enters the beta cell and is respired, allowing ATP production.
the ^ATP conc in the cell closes the potassium ion channels.
membrane depolarises and calcium ions rush into the cell.
insulin is released by exocytosis.
(K+ ion channels control the set point for plasma glucose homeostasis)
type 1 diabetes
occurs when there’s a lack of insulin because of the destruction of all or most beta cells of the pancreas by an autoimmune response.
regular injections of insulin are needed for survival.
the uptake of glucose by brain cells and RBC is not dependent of the presence of insulin but even in the presence of abundant glucose mussels do not take up the sugar in the absence of insulin
type 2 diabetes
occurs when the body target cells become less responsive to insulin. the type of diabetes can be controlled by diet
advantages of genetically modified bacteria to treat diabetes mellitus
- theres less likelihood of an immune response producing anti-insulin antibodies
- there’s a more rapid response and a shorter duration of response
- patients who have become tolerant of pig insulin (require larger doses to have same effect) respond better to human insulin.
- some patients don’t like the idea of using insulin from animals
- extraction and purification of insulin from animal pancreas is expensive.
