This is an OCR Gateway A level biology cheat sheet, Chapter 14 module 5. Specification reference: 5.1.4
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Endocrine glands release hormones in the blood.
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Exocrine glands release hormones via ducts.
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Gland
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Produces:
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Pituitary gland
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In brain - ADH, gonadotrophins, growth hormones.
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Thyroid
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In throat - thyroxine.
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Adrenal gland
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Above kidneys - adrenaline.
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Testes
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Testosterone
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Ovaries
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Progesterone, oeastrogen.
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Pancreas
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Between kidneys - insulin, glucagon.
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Thymus gland
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In thorax - thymosin
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Pineal gland
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In brain - melatonin
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Steroid hormones e.g. oestrogen
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Steroids = lipid-soluble and can therefore go through the membrane of the target cell.
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The hormone binds to a receptor in the nucleus.
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The hormone-receptor complex binds to DNA and acts as a transcription factor.
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mRNA produced for gene to create protein.
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Non-steroid hormones e.g. adrenaline
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Soluble in water - cannot go through the membrane.
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Hormone acts as primary messenger, binds to receptor on cell membrane surface.
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Receptor changes enzyme shape to catalyse formation of cAMP (secondary messenger) from ATP.
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Secondary messenger starts a cascade reaction which affects cellular function (for adrenaline, triggers glycogen breakdown).
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Exocrine and endocrine gland.
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Exocrine
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Amylases
Proteases Lipases |
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Endocrine
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Insulin
Glucagon |
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Histology
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α cells
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Produce and secrete glucagon.
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β cells
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Produce and secrete insulin.
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Islets of Langerhan
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Contain both types of cells.
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Adrenal cortex
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Glucocorticoids - e.g. cortisol, corticoseron.
Release controlled by hypothalamus |
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Mineralcorticoids - e.g. aldosterone (blood pressure and salt levels).
Release controlled by kidney signals. |
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Androgens - Small amounts of sex hormones.
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Adrenal medulla (fight or flight resp.)
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Adrenaline - Inc. blood glucose and heart rate.
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Noradrenaline - Works alongside adrenaline, increases heart rate, widens pupils.
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Lowering blood glucose
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Insulin released from beta cells.
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Glucose converted to glycogen.
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Respiration.
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Increasing blood glucose
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Glucagon released (alpha cells).
Causes glycogenolysis - breaks down glycogen into glucose |
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Glycogenesis - Make new glucose from other molecules.
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Diet.
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Glucose outside beta cell diffuses in through glucose transport protein.
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Glucose allows mitochondria to respire more and produce more ATP.
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ATP closes KATP channels.
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No movement of K+ makes it build up, depolarising the membrane (-30mV).
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Voltage-gated Ca2+ ion channels open, Ca2+ diffuses in.
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Ca2+ binds to vesicles containing insulin which binds to the - exocytosis and insulin is released.
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Type 1
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No insulin produced by beta cells.
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No cure, childhood symptoms develop early.
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Insulin injection as treatment.
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Type 2
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Can't effectively use insulin
- Body cells don't respond / beta cells don't produce enough. |
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Caused by diet / exercise.
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Can regulate person's carb intake through diet and drugs.
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Medically produced insulin
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Genetically modified bacteria produce human insulin.
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Stem cells
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Create new beta cells.
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Medulla oblongata
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Sends impulses to:
- Accelerator nerve to inc. heart rate. - Vagus nerve to dec. heart rate. |
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Chemoreceptors
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CO2 level detected in aorta, carotid and medulla.
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Baroreceptors
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Regulates blood pressure, detected in aorta, vena cava, carotid.
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