Hormonal Communication Flashcards
Describe islets of langerhans
Large spherical clusters made of endocrine pancreas tissue, secrete and produce hormones
Within islets are different cells classified according to the hormone they secrete
Alpha cell, produce and secrete glucagon
Beta cells, produce and secrete insulin
Alpha cells are larger and more numerous than beta cells within an islets
Describe the acini
Small berry like clusters, exocrine tissue, produce and secrete digestive enzymes
Enzymes secretes into ducts which lead into pancreatic ducts
Released into the duodenum, top of the small intestine
Where are the islets of langerhans and acini found
Pancreas
Target tissue
Any tissue which contains a large number of target cells
Target cells
Cells that posses specific receptors that a specific hormone will bind to in order to produce a response
Hormones
Released by endocrine glands
Carried in blood
Act as Chemical messengers
Exocrine gland
Secretes chemcials into ducts which carry hormone to another place in body
Peptide hormones
Hormones made of amino acids
E.g Adrenaline, insulin, glucagon
Cannot pass through phospholipid bilayer
Steroid hormones
Lipid based
Can pass through phospholipid bilayer
Have direct effect on DNA
E.g cortisone
How glucose level is increased
Diet- eating carbohydrate rich foods which get broken down into sugars (glucose)
Glycogenolysis- glycogen stored in the liver+muscle cells are broken down into glucose
Gluconeogenisis- production of “new “ glucose from breaking down non carbohydrate sources e.g lipids and amino acids
Detection of high levels of glucose
Detected by beta cells in islets of langerhans
Secrete insulin into blood stream
How insulin lowers blood glucose
Increase uptake of glucose by cells,
Increased respiratory rate of cells,
Increased rate of glycogenesis increased conversion of glucose to glycogen
Inhibit release of glucagon from alpha cells
Causes of decrease in blood glucose
Respiration- glucose in blood is used by cells to release energy, during exercise more glucose is needed
Glycogenesis- production of glycogen, excess glucose is taken out of diet and turned into glycogen
Detection of lower levels of blood glucose
Alpha cells in islets of langerhans
Secrete glucagon into bloodstream
How glucagon raises blood glucose concentration
Glycogenolysis- the liver breaks down its glycogen store
Reducing amount glucose absorbed by the liver cells
Increasing gluconeogenesis - increasing the conversion of AA + glycerol into glucose
Control of insulin secretion
- at normal level of glucose potassium channels are open ( -70mv resting potential inside cell)
- when glucose levels rise, glucose enters the cell via glucose transporter
- glucose is metabolised inside the mitochondria, resulting in production of ATP
- ATP binds to ATP sensitive potassium channel causing the channels to close
- potassium ions can no longer diffuse out of the cell, depolarisation occurs, potential difference rises to -30mv
- depolarisation causes the voltage gated calcium channels to open
- calcium ions enter the cell causing secretory vesicles to release the insulin they contain by exocytosis
Name Hormone secreted from the adrenal cortex
aldosterone, cortisol
Which gland is ductless
Endocrine gland
Cell whose metabolism is altered by the binding of a hormone
Target cell
Difference between hormonal and neuronal
Hormones are secreted into the blood stream via gland whereas, neuronal- electrical impulses are carried by synapses.
Hormones bind to target receptors to trigger a response whereas electrical impulses stimulate a response in an effector
Hormonal is a slower response compared to neuronal which is much faster
Hormonal is a widespread long lasting response whereas neuronal is a localised short lasting response
Outline the hormonal and nervous mechanisms involved in the control of the heart rate
Hormones ( adrenaline) are released into blood stream, having a direct effect on SAN causing it to produce more electrical impulses increasing HR due to the fight/flight response
Controlled nervously by the vagus nerve and the accelerator nerve which decrease and increase heart rate respectively.
Barco/ chemo receptors stimulate a particular nerve centre in the medulla oblongata linked by a motor neurone directly to SAN
Chemo receptors detect a increase in co2 levels, leading to an increase is heart rate
Where are insulin moleuces synthesised
Ribosmes are the RER in beta cells in the pancreas
Purpose of homeostatic mechanisms
To keep their internal body conditions near constant
Endocrine system
Sectres hormones, chemcial messangers, into the blood which transmit infomation from one part of fhe organism to another to bring about change
They alter the activity of target organs
Definition of a gland
Group of cells that produce and relsease one or more stubstances
How hormones bring about a response
Transported round the body in the blood to target cells/tissues to bring about a response
Only affect cells with receptors that the hormone can bind to
Receptors must be complimentary
Adrenal glands
2 small glands located at the top of the kidney
Adrenal cortex - outer reigon of glands, produces hormones that are vital to life such as cortisol and aldosterone
Adrenal medulla - inner reigon of the gland which produce non essential hormones such as adrenaline
Adrenal cortex and the hormones they secrete
Production of hormones by the adrenal cortex is controlled by the hormones released from the pituarty gland
3 types of hormone:
Glucocorticoids - includes cortisol, help regulate metabolism
Mineralcorticoids - produces aldosterone which help maintain blood pressure by regulating water and salt concentrations
Androgens - small amounts of male and female sex hormones
Adrenal medulla
Hormones of the adrenal medulla are released when the sympathetic nervous system is stimulated
Hormones secreted are:
adrenaline - increases the heart rate sending blood quickly to the muscle and brain, also converts glyogen to glucose liver
Noradrenaline - works with adrenaline in response to stress prodlucing effects such as increased heart rate, widening of pupils, widening of air passages, and vasoconstriction in non essential organs
Exocrine and endocrine function of the pancreas
Exocrine -secretes pancreatic jucie into the small intestine
Endocrine - produce insluin and glucagon
Detection and action of a decrease in blood glucose
Detected by alpha cells
Alpha cells secrete glucagon which binds to recptors in the cell surface membranes of liver cells activating the G protein
Activated G protein activates the enzyme adenyl cylase
Adenyl cyclase catalyses the conversion of ATP to cyclic AMP, which activates protien kinases that catalyses the breakdown of glycogen to glucose, glycogenolysis
Enzyme cascade amplifys the orginal glucagon signal
Glycogenesis
Synthesis of glycogen from glucose molecules
Triggered by insluin
Removes glucose molecues from the blood stream
Glycogenolysis
Breakdown of glycogen to produce glucose molecues
Glucagon triggers this process
Releases moee glucose molecules into the bloodstream
Gluconeogenesis
Synthesis of glucose molecues from non carbohydrates moleclues
Glucagon triggers this reaction
Enzymes convert molecues such as fatty acids and amino acids into glucose molecules
What is diabetes
Condition where homeostatic control of blood glucose has failed or deterioated
Insulin function is disrupted which allows blood glucose concentration to rise
Known to have glucose in urine
Dehydration
Exocrine function of the pancreas
Secretes digestive enzymes into the pancreatic duct which carries the enzymes to the duodenum and then the small intestine
does not directly enter blood
Why use a mean
To reduce the effect of outliers / anomalous results
