hormonal communication Flashcards
5 differences between hormonal and nervous system
hormones
1. long lasting effect
2. slow response
3. travel via bloodstream
4. irreversible and permanent
5. widespread response
nerves
1. short lived effect
2. fast response
3. transmission via neurons
4. reversible and temporary
5. localized response
what is a hormone?
- chemical messenger (e.g. steroid or protein) that is made by an endocrine gland and secreted directly into the bloodstream
- binds to specific receptors on target cells
exocrine gland
- makes secretions other than hormones
- secretions passed into a duct where it is needed
- e.g. enzymes into intestine
- not secreted into blood
endocrine gland
- secrets hormones directly into the bloodstream
- triggered by other hormones
thyroid gland
- produces thyroxine
- involved in thermoregulation
adrenal gland
- secretes adrenaline
- fight or flight response
what does the pancreas secret?
insulin and glucagon for regulation of blood glucose
pituitary gland
- ADH (anti diuretic hormone)
- regulates water balance
how can hormones bring about an effect to a target cell but not affect other types of cells?
- target cell has specific receptors on its cell surface membrane
- that are complementary to the hormone
- so hormone can only bind to these receptors
why do steroid hormones have a faster response on the target cell than the protein hormones?
- steroid hormones are lipid soluble
- so can pass through the cell surface membrane of the target cell
- to have a direct effect on the genes
- initiating a faster response
how do steroid hormones work?
- lipid soluble so can pass through cell membrane of target cell
- once inside cell, they bind to internal receptors in the cytoplasm or nucleus
- forming a “hormone-receptor complex”
- which acts like a transcription factor, turning genes on and off
- so they have a direct effect on the DNA in the cell
- so result in certain proteins being inhibited or produced
how do non-steroid hormones work?
- hydrophilic and not lipid soluble so cannot pass through cell membrane of target cell
- hormones are seen as the 1st messengers and they bind to receptors on the cell surface membrane as they have comp shapes
- they activate other molecules in the cell
- a G-protein is activated first
- then an enzyme (usually adenyl cyclase) is activated
- this catalyses the conversion of ATP to cyclic AMP
- which acts a secondary messenger and brings about the response of the hormone
- by acting on protein channels
- or by triggering a cascade of enzyme controlled reactions
examples of steroid hormones?
sex hormones
- progesterone
- testosterone
- oestrogen
describe the adrenal cortex
- outer region of adrenal gland
- produces hormones that are vital to life
-e.g. cortisol and aldosterone - involved in short term and long term responses to stress
- controlled by hormones from pituitary gland, which is in turn controlled by hypothalamus
3 things adrenal cortex releases
- glucocorticoids (cortisol)
- mineralcorticoids (aldosterone)
- androgens
glucocorticoids
- cortisol
- regulates metabolic rate and energy release from resp
- stimulates release of glucose from glycogen stores (to be used in resp)
- helps to regulate blood pressure
- suppresses immune system
- steroid hormone
mineralcorticoids
- aldosterone
- regulates salt and water balance
- so helps to control blood pressure
- steroid hormone
androgen
- small quantities of male and female sex hormones
- small impact on body
- steroid hormone
describe the adrenal medulla
- inner region of gland
- produces non-essential hormones
- like adrenaline
- which helps body to respond to stress
- involved in short term responses to stress
- releases adrenaline and noradrenaline which prepares body for action
- these are non-steroid hormones
what does adrenaline and noradrenaline cause?
- increased HR and SV to increase CO, more O2 to cells for resp to make ATP
- vasoconstriction of arterioles to increase blood pressure and the O2 delivery to cells per min
- dilating pupils to allow more light in to see better
- body hair stands erect to deter predators
- inhibition of gut
what type of diabetes is type 1?
- insulin dependent
- so little or no insulin is produced
when is type 1 diabetes usually diagnosed?
childhood or early adulthood
cause of type 1 diabetes
- immune system attacks beta cells in the IOL, which make insulin and destroy them
- this is due to faulty genes or severe viral infections that cause the immune system to overreact
what does type 1 diabetes result in?
- hyperglycemia
- this is a very high blood glucose conc after eating
what does hyperglycemia from type 1 diabetes cause? (high blood glucose conc)
- glucose which is usually converted into glycogen
- stays in the bloodstream inserted and is excreted into urine by kidneys which is not normal
how is type 1 diabetes treated?
- insulin injections
- insulin pumps (permanent device that pumps insulin at controlled rate beneath skin)
why can insulin not be taken as a tablet, only an injection?
- insulin is a protein hormone (non-steroid)
- it will be hydrolysed by protease enzymes in the stomach before it can be absorbed
- denatured by HCL in stomach
insulin used to come from slaughtered pigs, it now comes from genetically engineered bacteria. advantages?
- exact copy of human insulin so less chance of rejection or an immune response
- lower risk of infection
- cheaper to manufacture
- less ethical problems
- supply can meet demand
what type of diabetes is type 2?
non insulin dependent
when is type 2 diabetes usually diagnosed?
middle age
describe type 2 diabetes
- body cells lose sensitivity to insulin and stop responding to it
- lower levels of insulin produced
causes of type 2 diabetes
- genetics
- lifestyle factors
causes of type 2 diabetes
- genetics
- lifestyle factors
how is type 2 diabetes treated?
- low sugar diet
- tablets to stimulate insulin production
- tablets to slow down rate at which body absorbs glucose
- insulin injections
- more exercise
lifestyle factors that increase risk of type 2 diabetes?
- overweight/obese
- lack of regular exercise
- a diet high in sugars
- genes/ family history
- afro-caribbean origin/ asian
explain why glucose is present in the urine of someone with diabetes
the glucose concentration is too high so the kidneys cannot reabsorb all of the glucose back into the bloodstream
describe the symptoms of excessive thirst and frequent urination
- glucose in the urine lowers the water potential of the urine
- so more water is drawn into the urine by osmosis
- so you drink more water
describe the symptom of being very hungry and tired
- body cells cannot store as much glucose in the form of glycogen
- so use other energy reserves like lipids
- so you have decreased energy
- a lower cell resp rate so less ATP
describe the symptom of weight loss
energy reserves are used up but not replaced
describe the symptom of sight loss/blurred vision
- excess glucose in blood
- causes Hb to become “glycosylated”
- so it is less efficient in carrying O2
- leading to damage of tissues like retina
describe gangrene
- damage to blood vessels
- so poor circulation and a lack of O2 and glucose to cells
- so resp cannot take place
- leading to cell death
how do diabetics use biosensors?
- to test blood glucose concentration in the blood
- enzyme glucose oxidase detects glucose
- turns it into digital reading
advantages of using stem cells
- donor availability is not an issue as stem cells can produce unlimited supply of beta cells
- less chance of rejection
- ## improved quality of life
disadvantages of using stem cells
destroying a potential human life
how does the body respond to a rise in blood glucose concentration, e.g after eating a meal with carbs?
- beta cells in the IOL detect the change
- secrete insulin (protein hormone) directly into bloodstream
- nearly all body cells have receptors for insulin
- insulin arrives at the skeletal muscle or liver cell and bind to the receptors on the cell surface membrane
- leads to more glucose transporter proteins being inserted into the cell memb so more glucose can be taken up from the blood by the cell (facilitated diffusion)
- increased conversion of glucose to glycogen (glycogenesis)
- increased cell resp rate to use up glucose
- increased conversion of glucose into lipids
- insulin also inhibits glucagon
how does the body respond to a fall in blood glucose concentration, e.g. after not eating for a long amount of time/ vomiting?
- alpha cells in the IOL detect the change
- secrete protein hormone glucagon directly into the bloodstream
- only liver and fat storage cells respond to glucagon
- glucagon arrives at the liver or fat storage cell and binds to the receptors
- increased conversion of glycogen to glucose (glycogenolysis)
- decreased cell resp rate
- glucose is generated from lipids and a.a (gluconeogenesis)
- increased release of glucose into blood by facilitated diffusion.
- glucagon inhibits insulin
glycogenesis
glucose is converted to glycogen
glycogenolysis
glycogen is converted to glucose
gluconeogenesis
glucose is generated from lipids and a.a
describe the beta cell at the resting state
- in the resting state, K+ channels in the memb of the B cells open as there is not enough ATP produced to bind to the channels and cause them to close since there is little glucose
- and K+ diffuse out of cell
- so the p.d across the memb is -70mv
- so the membrane is hyperpolarised
- so voltage gated Ca2+ channels stay closed
- Ca2+ ions cannot enter
- so secretory vesicles containing insulin are not released by exocytosis
how is insulin released from the beta cell?
- glucose enters the B cell via a glucose transporter
- increased resp occurs as glucose is metabolised inside the mito, increasing ATP
- ATP binds to K+ channels, closing them (ATP sensitive)
- so K+ cannot diffuse out of the cell
- p.d across the membrane is -30mv
- so memb is depolarised
- causes voltage gated Ca2+ channels to open
- Ca2+ ions enter by facilitated diffusion
- secretory vesicles release insulin via exocytosis
