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A2 biology 1.3
OCR biology - hormones
| Question | Answer |
|---|---|
| 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 |
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