Hormonal communication Flashcards
Communication systems
Nervous and hormonal systems, which together coordinate the activities within a whole organism.
Cell siganlling
Cells use to communicate with adjacent and distant cells: insulin released by beta cells in the pancreas is transported to liver cells and binds to receptors on their cell surface membranes to increase uptake of glucose from the blood.
Homeostasis
Maintenance of a constant internal environment via physiological control systems to ensure optimum conditions for enzymes to work: body temp, blood pH, blood glucose.
NEGATIVE feedback
Negative feedback
When there is a deviation from normal values, reverse/counteract the change to restore optimum levels.
Positive feedback
Deviation from set limit triggers response to increase the deviation further: during childbirth, baby’s head presses on cervix causing oxytocin to be released, causing uterus to contract and release more oxytocin.
Endotherm
Physiological responses to regulate internal body temperature via nervous responses.
Peripheral temperature receptors detect external temperature changes triggering vasodilation/vasoconstriction as well as sweating/shivering.
Ectotherm
Internal body temperature dependent on environmental temperature, adapting their behaviours to minimise temperature change to their bodies: basking in sun or moving to shade.
Liver structure
Hepatocytes
Receives oxygenated blood through hepatic artery and leaves via hepatic vein.
Kupffer cells
Macrophages in sinusoids of liver which engulf pathogens via phagocytosis.
Functions of Liver
- glycogen storage
- detoxification
- carbohydrate and protein metabolism
- amino acid synthesis
- bile production
Detoxification
Neutralisation and breakdown of unwanted chemicals (alcohol, drugs, toxins)
Deamination
Amine group removed from amino acid, converting it into ammonia which occurs in the liver as proteins cannot be stored.
Kidney structure
2 kidneys
Renal artery: supplies blood to be filtered
Renal vein: carries filtered blood away
Cortex, medulla, pelvis (composed of nephrons).
Nephron structure
Bowman’s capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct
Bowman’s capsule
Ultrafiltration: afferent arteriole is wide than efferent arteriole (80% water lost by ultrafiltration)
creates high hydrostatic pressure
Small molecules and water forced out of capillaries into renal capsule, and plasma proteins and blood cells remain in blood.
Proximal convoluted tubule
Selective reabsorption: walls made of microvilli epithelial cells which provide large SA for reabsorption of glucose into cells.
Osmoregulation
Process of controlling water potential of blood with hormones: antidiuretic hormone ADH released from pituitary gland.
Nephron
Blood filtered and useful substances are reabsorbed into the blood.
Reabsorption of glucose by PCT
Na+ ions actively transported out cells of PCT into capillaries to create concentration gradient.
Na+ ions move by cotransport (facilitated diffusion) from filtrate into cells, co transporting glucose (and amino acids) with them.
High conc in cells allows glucose to diffuse into blood and water moves in same direction due to water potential gradient.
Reabsorption of water by DCT/collecting duct
Water moves out of DCT and collecting duct by osmosis down a water potential gradient, controlled by ADH which changes the permeability of membranes to water.
ADH cause vesicles containing aquaporins to move to cell surface membranes increasing the reabsorption of water.
Role of hypothalamus in osmoregulation
Osmoreceptors detect changes in water potential, producing ADH when blood has lower water potential. Osmoreceptors shrink and stimulate more ADH to be made so more released rom pituitary gland.
ADH
Produced by hypothalamus and released by pituitary gland.
Increases permeability of walls of collecting duct and DCT to water.
More ADH = more aquaporins fuse with walls so more water reabsorbed back into blood and urine is more conc.
Endocrine glands
Secrete hormones which are transported in blood before binding to their target cell, causing a response: pancreatic glands release insulin and target cells are hepatocytes in liver.
Hormones
Chemical messengers transported in blood
Effects more widespread and longer lasting
Range of chemicals: steroids, proteins, glycoproteins, polypeptides, amines.
Steroid hormones
Lipid-soluble and can diffuse across cell surface membrane into their target cell to bind to receptor located in cytoplasm: oestrogen binds to transcription factors within cytoplasm.
Non-steroid hormones
Insoluble in lipids so cannot diffuse across cell surface membrane, binding to complementary-shaped receptors on cell surface membrane of target cell. Binding receptor causes cascade of effects within cell.
Adrenal glands
Adrenal cortex and adrenal medulla, surrounded by capsule.
AC and AM both secrete hormones.
Adrenal cortex
Controlled by hormones secreted by pituitary gland (in brain): cortisol, aldosterone, androgens.
Adrenal medulla
Controlled by nervous system, stimulation of sympathetic nervous system secreting: adrenaline and noradrenaline.
Pancreas
Releases hormones that control blood glucose concentration (endocrine gland) and enzymes for digestion (exocrine gland).
Adrenaline
Released by adrenal glands if body anticipates danger, increasing heart rate and raises blood glucose concentration.
Noradrenaline
Increased heart rate
Pupils dilate
Widens airways in lungs
Narrows blood vessels (creating higher blood pressure).
Islets of Langerhans
Tissue in pancreas containing cells involved in detecting changes in blood glucose levels.
Contains endocrine cells (Alpha and Beta) which release hormones to restore blood glucose levels.
Alpha cells
Islets of Langerhans
Release glucagon when low blood glucose concentration detected.
Beta cells
Islets of Langerhans
Release insulin when high blood glucose concentration detected.
Factors affecting blood glucose concentration
Eating carbohydrates (glucose reabsorbed from intestine to blood)
Exercise (increase rate of respiration, using glucose).
Action of insulin
Binds to specific receptors on membranes of liver cells, increasing permeability of cell membrane.
Glucose enters from blood by facilitated diffusion.
Activation of enzymes in liver for glycogenesis.
Rate of respiration increases.
Action of glucagon
Binds to specific receptors on membrane of liver cells and activates enzymes for glycogenolysis which then activates enzymes for gluconeogenesis.
Rate of respiration decreases and blood glucose concentration increases.
Gluconeogenesis
Creating new glucose from non-carbohydrate stores in liver (amino acids -> glucose).
Occurs when all glycogen has been hydrolysed and body requires more glucose, initiated by glucagon when blood glucose concentration are low.
Glycogenolysis
Hydrolysis of glycogen back into glucose, occurring due to glucagon to increase blood glucose concentration.
Glycogenesis
Glucose converted to glycogen when blood glucose is higher than normal, caused by insulin to lower blood glucose concentration.
Second messenger model
Stimulation of molecule (enzyme) which can then stimulate more molecules to bring about desired response: adrenaline causes glycogenolysis to occur inside cell when binding to receptors on outside.
Second messenger model process
Adrenaline (first messenger) binds to specific complementary receptors on cell surface membrane.
Activates adenyl cyclase
Converts ATP to cAMP (secondary messenger)
cAMP activates protein kinase A which activates cascade of enzyme controlled reactions to break down glycogen to glucose (glycogenolysis).
Diabetes
Disease when blood glucose concentration cannot be controlled naturally.
Type 1 diabetes
From childhood, autoimmune disease, body unable to produce insulin as beta cells are attacked.
Treated using insulin injections.
Type 2 diabetes
From obesity/poor diet, receptors in target cells losing responsiveness to insulin.
Treated by controlling carbohydrates in diet and increasing exercise with insulin injections.
