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Biology A level - Hormonal communication Cheat Sheet by

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.
Pituitary gland
In brain - ADH, gonado­tro­phins, growth hormones.
In throat - thyroxine.
Adrenal gland
Above kidneys - adrena­line.
Proges­terone, oeastr­ogen.
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).

The pancreas

Exocrine and endocrine gland.
α cells
Produce and secrete glucagon.
β cells
Produce and secrete insulin.
Islets of Langerhan
Contain both types of cells.
Adrenal cortex
Glucoc­ort­icoids - e.g. cortisol, corticoseron.
Release controlled by hypoth­alamus
Minera­lco­rti­coids - e.g. aldost­erone (blood pressure and salt levels).
Release controlled by kidney signals.
Androgens - Small amounts of sex hormones.
Adrenal medulla (fight or flight resp.)
Adrenaline - Inc. blood glucose and heart rate.
Noradr­enaline - Works alongside adrena­line, increases heart rate, widens pupils.

Pancreas histology

Contro­lling blood glucose

Lowering blood glucose
Insulin released from beta cells.
Glucose converted to glycogen.
Increasing blood glucose
Glucagon released (alpha cells).
Causes glycog­eno­lysis - breaks down glycogen into glucose
Glycog­enesis - Make new glucose from other molecules.

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.
No cure, childhood symptoms develop early.
Insulin injection as treatment.
Type 2
Can't effect­ively use insulin
- Body cells don't respond / beta cells don't produce enough.
Caused by diet / exercise.
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.
CO2 level detected in aorta, carotid and medulla.
Regulates blood pressure, detected in aorta, vena cava, carotid.


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