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