Summary The Endocrine System Grade 12 Life Science (Biology)
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Course
Life Sciences
Institution
12th Grade
This document contains a very detailed summary of the entire endocrine system found in the Mind Action Series Life Science Grade 12 Textbook. The notes are colourful, contain diagrams and are easy to understand.
Module 2.1
Chemical Co-Ordination: Pituitary gland
= slow, prolonged process of = chemical co-ordinator of most
communicating info throughout body endocrine glands (called master gland)
by chemicals (hormones) o Attached to hypothalamus @ base
o Hormones = secreted by endocrine system of brain by short stalk
o Works w/ nervous system
= organic chem
substance, protein but sometimes
steroid secreted by endocrine gland
& carried in blood stream to target
organs where regulates metabolic { HORMONES SECRETED BY PITUITARY }
reactions
1. Thyroid stimulating hormone
= hormones are (TSH)
carried in blood through body & only o Stimulates thyroid gland to secrete
affect certain cells thyroxin
= vascular, 2. Follicle stimulating hormone (FSH)
o In females, stimulates oogenesis in
ductless gland that secretes
ovary (formation of eggs, ova)
hormones carried in bloodstream to
o In males, stimulates spermatogenesis
target organs in testes (sperm formation)
3. Luteinizing hormone (LH)
Exocrine = secretions carried in ducts to o Stimulation ovulation from ovary &
where needed while endocrine = x have ducts formation of corpus luteum
& secretions are carried in bloodstream to
target organs 4. Prolactin
o Stimulates prod of milk in female
mammary glands after birth
o Responsible for maternal instinct
5. Adrenocorticotropic hormone
(ACTH)
o Stimulates adrenal cortex to secrete
cortisone & aldosterone
6. Interstitial cell stimulating
Endocrine Glands in Body hormone (ICSH)
o Stimulates testes to secrete
testosterone
7. Growth hormone (GH)
o Promotes skeletal & muscular growth
o Done by stimulating protein
synthesis
GROWTH DISORDERS:
= over secretion of
Hypothalamus hormone
Part of brain above pituitary gland = under secretion
o Secretes ADH (anti - diuretic hormone) of hormone
, 2. Hyposecretion of GH =
Module 2.1
underdeveloped skeleton (short
stature) – known as pituitary dwarfism
thyroxin in blood constant
Done by control mechanism (negative
o Betw 91-122cm (body parts =
proportionate) feedback)
o Not mentally retarded but = sexually Thyroid & pituitary glands interact:
immature 1. Pituitary detect decr level of thyroxin
o Treated by injections of synthetic in blood ∴ secrete more TSH
growth hormone (STH) prod by 2. TSH stimulates thyroid to secrete more
genetically engineered bacteria 3. High level of thyroxin inhibits further
secretion of TSH from pituitary
In adults, over-secretion of GH =
acromegaly Negative feedback mechanism ensure level
of thyroxin in blood = kept @ correct level
o Bones of face, hands & feet = enlarged
o Thickening of soft tissue leads to
enlarged features & enlarged tongue
Thyroid gland:
Found on either side of trachea just
below larynx (voice box) @ front of neck Homeostasis and Negative
FeeDback Control
Tissue fluid & blood = extracellular fluid &
2gether form internal environ of body
= fluid that surrounds
Thyroid gland secretes thyroxin body cells
o Iodine = NB for prod of thyroxin =
o Goitre develops if levels of iodine = low
surroundings where organism lives
{ FUNCTION OF THYROXIN } Factors in internal environment need remain
constant (K) for optimal cell functioning
1. Increases basal metabolic rate – does it
by controlling rate of cellular respiration levels
o basal metabolic rate = amount energy body
- Conc H2O - Electrolytes
needs to keep functioning @ rest - CO2 - O2
- Glucose - Tempe
2. Promotes normal functioning of <3
- pH
3. Promotes normal functioning of nervous
system by increasing nervous activity & = process of
sharpening alertness & reflexes maintaining the internal environment
at a constant optimal state, despite
Disorders constant changes in the external
environment
Hypothyroidism = prod too little thyroxin leads
to low metabolic rate
o In adults result in myxoedema = condition of
mental & physical sluggishness w/ low blood detect any change from set point / norm
pressure, a slow heart + respiratory rate & low therefore need correct change / deviation
body temp
o In children results in cretinism, a condition in
which child x grow physically, has immature Negative feedback= a control mechanism
development & = mentally retarded whereby a change from the set point of any
factor is corrected by bringing about a change in
➢ Hypothyroidism = treatable w/ iodine
supplements / synthetic iodine
the opposite (neg) direction.
o Too much of a particular factor, a process is set
Hyperthyroidism = prod too much thyroxin in motion to reduce that factor; if there is too
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