A revision summary of OCR A level Biology Hormonal Communication 5.1.4
Made by a student who achieved A* in A level Biology.
Covers all the points within the OCR Biology Specification.
Condenses 3 OCR specification books and class notes.
Endocrine system – hormones, blood, glands. LH, FSH
Endocrine gland – ductless glands that secrete hormones directly into blood stream
Exocrine gland – ducts secrete hormones directly into bloodstream
Hormones –chemical messengers released directly into bloodstream. Thyroxine
- Protein/ peptide hormones not soluble in pp-lipid bilayer. Must bind to specific target
cell on CSM to bind and cause response. need 2 nd messenger Thymosin
- Steroid hormones soluble and pass through CSM and enter cell & nucleus. (As cholesterol
based)
Adrenaline
Hormonal system Nervous system
Chemical messenger nerve impulses
Transmission by bloodstream Transmission by neurones Insulin
Not released to receptor so slower Rapid response
effect Travel to specific parts of body Oestrogen,
Travel to all parts of body No target tissue Progesterone
Target tissue Short-lived
Long-lasting effect Temporary & reversible Testosterone
Can be permanent & irreversible
Adrenal Glands (endocrine) – secrete hormones directly into surrounding blood vessels.
Cortex – outer region Medulla – inner region
- Steroid hormones from cholesterol - protein hormone, polar molecule
Glucocorticoids Mineralocorticoids e.g. Adrenaline
e.g. Cortisol Aldosterone
Metabolism of conc. of sodium & 1. 1st messenger Adrenaline is secreted from Adrenal medulla directly into blood stream
proteins & potassium ions in blood (endocrine).
carbs in liver. (blood pressure) 2. Bind to specific complementary receptor sites on target tissue CSM
- Stimulates - Acts on distal tubules & 3. Binding causes G protein inside cell to split which activates effector molecule - Adenyl
glycogen collecting ducts of Cyclase
glucose in kidneys 4. Adenyl Cyclase converts ATP cAMP (2nd messenger)
liver. - ↑reabsorption of Na+ 5. Causes cascade of enzyme-controlled reactions.
ions and ↓reabsorption In response to shock, stress
of K+ ions = ↑water - ↑heart rate, ↑blood flow to muscles and brain, ↑glycogenolysis, pupil dilation, sweat
retention = ↑bp secretion
Adrenal Cortex
Zona glomerulosa – outer layer secretes
aldosterone
Zona fasciculata – middle layer secretes cortisol
Zona reticularis – inner layer secretes androgens
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