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Summary Strand 2 - Life Processes in Plants and Animals
For Life Sciences Strand 2, this is a full summary with definitions and diagrams, all the facts you need to know as it is followed according to the SAGs document.
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Life Processes in Animals and PlantsHuman Endocrine System
Hypothalamus
It is part of the brain, situated above the pituitary gland, where it secretes ADH.
Role: (Osmoregulation)
Low water levels – more ADH released – water reabsorbed from collecting ducts – concentrated
urine released.
High water levels – less ADH released – water released as collecting ducts are not permeable –
diluted urine released.
Pituitary Gland
Attached to the hypothalamus at the base of the brain by a short stalk.
What hormones are secreted?
1. Thyroid Stimulating Hormone (TSH)
Stimulates the thyroid gland to secrete thyroxin.
2. Follicle Stimulating Hormone (FSH)
In females FSH stimulates oogenesis in the ovaries. In males FSH stimulates
spermatogenesis in the testes.
3. Luteinizing Hormone (LH)
Stimulates ovulation from the ovary and the formation of the corpus luteum.
4. Prolactin
Stimulates the production of milk in the female mammary glands after birth.
5. Growth Hormone
Promotes skeletal and muscular growth by stimulating the synthesis of proteins.
6. Oxytocin
Causes the wall of the uterus to contact and relax during labour.
,Thyroid Gland
Found on either side of the trachea just below the larynx in the front of the neck. It secretes
thyroxin.
Functions
Increases basal metabolic rate in all body cells by controlling the rate of cellular
respiration.
Promotes the normal functioning of the heart.
Promotes the normal functioning of the nervous system by increasing nervous activity.
Disorders
Hyperthyroidism: (overactive thyroid, high metabolic rate)
Swollen thyroid, weight loss, increase heart, respiratory rate and blood pressure, increase
temperature and swearing etc.
Hypothyroidism: (low metabolic rate)
In children, cretinism is a condition in which a child does not grow physically, immature sex
development, mentally retarded.
In adults, myxedema is a condition of mental and physical sluggishness, low blood pressure and
body temperature. Slow heart and respiratory rate.
Increased thyroxin Thyroid more stimulated,
inhibits the more thyroxin. Increased
pituitary gland. cell metabolism
More TSH
Pituitary Gland Thyroid Gland
Less TSH
Decreased thyroxin Thyroid less stimulated, less
stimulates pituitary thyroxin released. Decreased
gland. cell metabolism.
Pancreas
Glucagon
Secreted by alpha cells in Islets of Langerhans. Increases blood sugar by causing the conversion
of glycogen into glucose.
, Insulin
Secreted by beta cells in Islets of Langerhans. Lowers blood sugar by causing the conversion of
glucose into glycogen and allows glucose to enter cells.
Over secretion – Obesity Under secretion – Diabetes
High blood sugar –
insulin released. Glucose absorbed
Eating, drinking into cells. Used or
(sugary things) stored as glycogen.
Optimal blood sugar level.
Glycogen turned
Exercise or have into glucose, in the
not eaten. liver and released
Low blood sugar – into bloodstream.
Type 1 Diabetes glucagon released.
Usually starts in childhood.
The body’s immune system destroys the insulin-producing beta cells in the pancreas. The
pancreas does not make insulin. Glucose remains in bloodstream.
Type 2 Diabetes
Usually starts in adulthood.
Lifestyle choices. It develops when the body produces less insulin or not able to use the insulin
correctly.
Adrenal Glands
Found on the top end of each kidney. The adrenal medulla secretes Adrenalin.
Function
Secreted under situations of sudden danger or excitement and prepares the body for action.
Effects on the body
Blood pressure increased.
Blood sugar levels increased.
Oxygen content of the blood is raised.
Heart rate increased.
Dilation of pupils.
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