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A2 biology 1.3

OCR biology - hormones

What is the exocrine/ endocrine systems? Exocrine - cells in exocrine glands secrete substances (tears, sweat, saliva) into a duct that carries it elsewhere. Endocrine - cells in endocrine glands (ductless!) secrete homrones into blood, transported around body, bind to complementary receptors
What is a target cell? A cell that a specific hormone acts on, as it contains the complementary receptor to the hormone
What are the 2 types of hormone? Protein - lipophobic, bind to complementary receptors on plasma membrane and activate genes via second messengers. Steroid - lipophilic, diffuse through phospholipid bilayer and affect DNA directly.
What is a 1st/ 2nd messenger? 1st messenger = a hormone that transmits a signal around the body. 2nd messenger = transmits a signal inside a cell
What is adrenaline's mechanism of action? An amino acid derivative - adrenaline (1st messenger) binds to a complementary receptor on plasma membrane, which is associated with adenyl cyclase. Adenyl cyclase is activated: ATP -> cAMP. cAMP (2nd messenger) =enzyme cascade reaction, activates genes
WHat is the function of adrenaline? It prepares the body for activity - increases rate of respiration -relaxes smooth muscle in bronchioles, increases heart rate/stroke vol, vasoconstriction, glycogenolysis. Dilates pupils, increases mental awareness, pilo-erection, inhibits action of gut
Where are the adrenal glands and what is their structure/functions? 2 adrenal glands, 1 above each kidney. Adrenal medulla in manufactures and secretes adrenaline in response to stress. Adrenal cortex manufactures steroid hormones using cholesterol: glucocorticoids e.g. cortisol, mineralocorticoids e.g. aldosterone
What are the exocrine functions of the pancreas? It manufactures digestive enzymes, secretes them into a fluid inside tubules, which lead to the pancreatic duct, which leads to the duodenum. Fluid contents: amylase, trypsinogen, lipases, HCO3- ions
What are the endocrine functions of the pancreas? Islets of Langerhans synthesise hormones and secrete them into networks of capillaries. a cells synthesise and secrete glucagon. b cells synthesise and secrete insulin. monitor blood glucose conc, optimum is 90mg 100cm-3
What happens if blood [glucose] is too high? Detected by b cells, b cells secrete insulin, binds to complementary receptors on liver/muscle cell membrane, adenyl cyclase, ATP-> cAMP -> enzyme cascade reaction, more glucose channels inserted, influx, glycolysis, glycogenesis, glucose -> fat
What happens if blood [glucose] is too low? Detected by a cells, a cells secrete glucagon, binds to complementary receptors on hepatocytes, adenyl cyclase, ATP -> cAMP, enzyme cascade reaction: gluconeogenesis, glycogenolysis, glucose leaves cells, fatty acids used for respiration.
What is a) gluconeogenesis, b) glycogenolysis, c) glycolysis, d) glycogenesis? a) pyruvate/ amino acids -> glucose b) glycogen -> glucose c) glucose -> pyruvate d) glucose -> glycogen
How is insulin secreted by beta cells? K+ ion channels open at rest, K+ efflux , -70mV. High blood [glucose], influx of glucose, lots of ATP generated, ATP blocks K+ ion channels. Depolarisation opens voltage-gated Ca2+ ion channels, influx, bind to channels on vesicles, dock, fuse, exocytosis
what is diabetes mellitus? The condition where blood [glucose] isn't maintained effectively by the body. Low [glucose] = hypoglycaemia - fatigue, irrational behaviour. High [glucose] = hyperglycaemia - ketoacidosis, thirsty, blurred vision
What is type 1 diabetes mellitus? Insulin-dependent, juvenile onset, caused by a viral/autoimmune attack on B cells, body doesn't produce sufficient insulin so no glycogen, treatment: insulin injections or stem cells from pancreas that can differentiate into b cells
What is type 2 diabetes mellitus? Non-insulin dependent.Individuals produce less insulin, responsiveness to insulin decreases with age (number of receptors and ability of receptors to respond decrease), higher chance: obesity, high sugar intake, afro-carribean/Asian origin, family history
Why is it advantageous to use genetically modified bacteria to produce insulin instead of extracting it from pigs? Exact copy of human insulin (more effective, faster acting), lower chance of rejection, tolerance, infection, fewer ethical issues, production can be increased/decreased according to demand, cheaper
What is a property of heart muscle? Myogenic - contracts + relaxes without external nervous/ hormonal stimulation
At rest, how is heart rate controlled? By SAN - frequency of excitation waves:60-80 waves per min. SAN initiates waves of electrical excitation -> AVN -> Bundle of His -> Purkyne tissue -> apex -> up ventricle walls, causing ventricular contraction
How does the medulla oblongata affect heart rate? Cardiovascular centre sends impulses to SAN to alter frequency of contractions, accelerator pathway (sympathetic, increases heart rate, noradrenaline), vagus nerve (parasympathetic, decreases heart rate, acetylcholine)
What factors affect heart rate? Exercise - chemoreceptors detect drop in blood pH + increase HR, baroreceptors detect change in pressure, stretch receptors detect muscle movement +increase HR, after exercise, stress
How/ why does heart activity change during increased activity? heart rate increases, stroke volume increases, strength of heart contractions increase. Increases speed of blood flow around the body to provide cells with more O2/glucose and excrete CO2 more quickly
How/ why does heart activity change during stress? Adrenaline is secreted by adrenal medulla in response to pain, shock, anticipation, excitement. Binds to noradrenaline receptors in accelerator pathway to increase heart rate and stroke volume - increases rate of respiration to prepare body for activity
Define: medulla oblongata Region of brain (at base) controls autonomic functions, controls cardiac and involuntary (smooth) muscle
Created by: 11043



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