Summary Biology Paper 2 Topic Summaries Matric IEB
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Course
Life Sciences
Institution
12th Grade
Master your IEB Life Sciences Paper 2 with this comprehensive, easy-to-understand summary! Covering all key topics in clear, concise points, this guide is designed to help you grasp complex concepts quickly and efficiently. Perfect for revision, exam prep, or as a quick refresher before your finals...
biology
Human Endocrine System
Hypothalamus
Above pituatary gland secretes ADH (Anti-diuretic hormone)
• helps conserve water
Pituatary Gland
Master gland: controls work fflow and direction
What hormones are secreted:
• TSH (Thyroid Stimulating Hormone)
• FSH (Follicle Stimulating Hormone): oogenesis and spermatogenesis
• LH (Luteinizing Hormone): stimulates ovulation
• Prolactin: Maternal instinct and breast milk
• ACTH (Adrenal Corticotropic Hormone): stimulates adrenal cortex
• ICSH (Interstitial Cell Stimulating Hormone): stimulates testes to secrete testerone
• GH/STH (Somatotrophic Hormone): stimulates protein synthesis
Growth Disorders
Hypersecretion
• gigantism
• in adults: acromegaly
Hyposecretion
• dwarfism
Thyroid Gland
Secretes thyroxin
If iodine levels are low, goitre may develop
Functions of Thyroxin
• Increases the basal metabolic rate (amount of energy needed while at rest)
• Heart
• Nervous System: sharpening alertness and reflexes
Disorders
,Hyperthyroidism (iodine supplements or synthetic iodine)
• myxoedema: mental and physical sluggishness
• Cretinism: children who become mentally retarded
Hyperthyroidism
• high body temperature and sweating
• Heart and respiratory rate and increased blood pressure
• Muscular tremors and nervousness
• Exophtalmic goitre (swollen)
Keeping thyroxin in blood constant (negative feedback system)
• decreased level of thyroxin, secretes more TSH
• TSH stimulates the thryoid gland to secrete more thyroxin
• Higher level of thyroxin inhibits further secretion
less TSH
too much thyroxine
Pituitary
Thyroid
too little thyroxine
More TSH
Homeostasis and Negative Feedback Control
How is it maintained?
Negative feedback system
Maintaining balance/equlibrium in the body regardless of changes in ext or int environment
Receptor - Control Centre - Effector
Pancreas
Exocrine function: secretion of pancreatic juice
Endocrine function: secretion of hormones by Islets of Langerhans
• Alpha cells secrete glucagon
• Beta cells secrete insulin
·
, glucose: blood sugar
glucagon: hormone
glycogen: stored version of glucose
Blood Glucose Regulation
insulin body cells take more
-
glucose
- liver takes + stores
BETA cells stimulated glycogen
↑ L
to release I into blood
sticky blood declines to a set
,
med
point
↑
high Stimulus carb
:
s homeostasis E
low Stimulus :
Y Skipping a meal
↓
rises to set point ALPHA cells stimulated
N to release into blood
of
liver breaks
(
down glucagon
glycogen
treleases
glucose
Insulin’s 2 main target organs:
• Muscles and liver
Diabetes Mellitus
High glucose levels in blood
Type 1: insulin dependant
Auto-immune disease
Pancreas doesn’t make insulin
From childhood
Daily insulin injections
Type 2: non-insulin dependant
Adulthood, influenced by lifestyle
Body produces less or isn’t able to correctly use insulin
Weight loss, fatigue
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