Life Sciences June Exam Notes
Strand 2: Life Processes in animals and plants pg. 37 – 89
2.1. Human Endocrine System pg. 37
Term Definition/Explanation
Chemical coordination Slow, prolonged process of communicating information throughout
body using hormones secreted via endocrine glands.
Hormone Organic, chemical substance secreted by an endocrine gland and
carries in the blood stream to its target organ(s) where it regulates
metabolic reactions, e.g. steroid/protein.
Target organ Specific cells that respond to a given hormone and have receptor sites
for it.
Endocrine gland Vascular, ductless gland that secretes hormones throughout
bloodstream to target organs.
Feature Exocrine Glands Endocrine Glands
Definition Glands that secrete substances Glands that secrete hormones
into ducts directly into blood
Mode of Secretion Via ducts to a surface (e.g., skin, Directly into the bloodstream
digestive tract)
Secretion Type Enzymes, sweat, saliva, mucus, Hormones (chemical messengers)
etc.
1. Hypothalamus: Role of ADH (antidiuretic hormone) - osmoreceptors in brain detect change in
osmolarity levels, releases more or less ADH to regulate water levels.
2. Pituitary gland (Master gland):
Hormone (Full Name) Target Organ(s) Main Function(s)
TSH (Thyroid Stimulating Thyroid gland Stimulates the thyroid gland to produce thyroxine
Hormone) (T₄), which regulates metabolism.
FSH (Follicle Stimulating Ovaries (females), Stimulates growth of ovarian follicles and
Hormone) Testes (males) oestrogen secretion in females; initiates sperm
production in males.
LH (Luteinizing Hormone) Ovaries (females), Triggers ovulation and progesterone production in
Testes (males) females; stimulates testosterone secretion in
males.
ICSH (Interstitial Cell Testes (Leydig cells) Stimulates testosterone production in males.
Stimulating Hormone) (Same as LH in males.)
ACTH (Adrenocorticotropic Adrenal cortex Stimulates secretion of cortisol and other
Hormone) glucocorticoids, especially during stress.
Prolactin (Lactogenic Mammary glands Promotes milk production after childbirth and
Hormone) (breasts) maintains lactation.
Oxytocin Uterus and Causes uterine contractions during childbirth and
mammary glands milk ejection (let-down reflex) during
breastfeeding.
1 of 51
,Growth disorders:
Age Hormone Imbalance Condition Description
Group
Children Hypersecretion of Gigantism Abnormally increased height and large body size
Growth Hormone (GH) caused by excessive secretion of GH before the
closure of growth plates.
Children Hyposecretion of Growth Dwarfism Short stature and stunted growth due to
Hormone (GH) insufficient secretion of GH during childhood.
Adults Hypersecretion of Acromegaly Enlargement of hands, feet, and facial features
Growth Hormone (GH) due to excessive GH secretion after the closure of
growth plates.
Children Hyposecretion of Cretinism Mental retardation and physical growth defects
Thyroxine caused by thyroid hormone deficiency during
early development.
3. Thyroid Gland (Butterfly Gland):
Functions: 1Increases basal metabolic rate controlling rate of cellular respiration, 2promotes normal
functioning of heart and 3promotes normal functioning of the nervous system by increasing nervous
activity and sharpening alertness and reflexes.
Negative Feedback System:
1. Low thyroxine levels in the blood are detected by the hypothalamus.
2. The hypothalamus releases TRH (Thyrotropin-Releasing Hormone).
3. TRH stimulates the anterior pituitary to release TSH (Thyroid Stimulating Hormone).
4. TSH stimulates the thyroid gland to produce and release thyroxine (T4).
5. As thyroxine levels rise, they inhibit further release of TRH and TSH.
6. This stops overstimulation of the thyroid, maintaining hormonal balance.
Homeostasis and negative feedback control:
Concept Definition Key Features Example
Homeostasis The process by Involves constant monitoring, Body temperature, blood
which the body regulation, and correction of sugar, water balance, pH,
maintains a stable body conditions hormone levels
internal environment
despite external
changes
Negative A control mechanism Works like a thermostat: Regulation of thyroxine,
Feedback that reverses a when a level is too high or blood glucose (insulin &
change to return the low, corrective action is taken glucagon), body temperature,
body to normal to restore balance water levels (ADH)
How Negative Feedback Works (Basic Steps):
1. Stimulus: A change occurs in the internal environment (e.g., low thyroxine).
2. Receptor: Detects the change (e.g., hypothalamus senses low hormone level).
3. Control Centre: Processes the information and sends signals (e.g., pituitary gland releases
TSH).
4. Effector: Acts to correct the change (e.g., thyroid releases more thyroxine).
5. Response: The internal condition returns to normal, and further stimulation stops.
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,Age Hormone Imbalance Condition Description
Group
Children Hyposecretion of Cretinism A condition in infants and children caused
Thyroxine (T₄) by thyroid hormone deficiency; leads to
stunted growth, mental retardation, and
delayed physical development.
Adults Hyposecretion of Myxoedema A condition in adults resulting from low
Thyroxine (T₄) thyroid hormone levels; causes fatigue,
weight gain, swollen face, dry skin, and
slow mental and physical activity.
Hyposecretion of Hypothyroidism General term for underactive thyroid activity —
Thyroxine (T₄) body metabolism slows down, causing weight
gain, tiredness, cold intolerance, and
depression.
Hypersecretion of Hyperthyroidism Overproduction of thyroid hormones leading to
Thyroxine (T₄) (Graves’ Disease) increased metabolism, weight loss, rapid
heartbeat, sweating, irritability, and bulging
eyes (exophthalmos).
Gender / Hormone Imbalance Endocrine Disorder Description / Effect on Fertility
System
Female Hyposecretion of Ovarian Failure / Low levels of female sex hormones
Oestrogen and Hypogonadism lead to failure of ovulation,
Progesterone irregular or absent menstrual
cycles, and inability to conceive.
Female Hypersecretion of Polycystic Ovary Excess production of androgens
Androgens Syndrome (PCOS) (male hormones) disrupts normal
ovulation, causes infertility,
irregular periods, and cysts on
ovaries.
Male Hyposecretion of Testicular Low testosterone levels result in
Testosterone Hypofunction / decreased sperm production,
Hypogonadism reduced libido, and infertility.
Both Hormonal Imbalance in Pituitary Disorders Abnormal secretion of pituitary
(Male & Pituitary Gland (e.g., hormones affects gonadal function
Female) excess Prolactin or low — can inhibit ovulation in females
FSH / LH) or sperm production in males.
Both Thyroid Hormone Hypothyroidism / Both underactive and overactive
(Male & Imbalance Hyperthyroidism thyroid can interfere with
Female) reproductive hormones, leading to
irregular cycles, low sperm count,
or miscarriage risk.
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, 4. Pancreas:
Hormone Secreted by Target Function
Organ(s)
Insulin Beta cells (Islets of Liver, Muscles Lowers blood glucose by converting
Langerhans) glucose → glycogen
Glucagon Alpha cells (Islets of Liver Increases blood glucose by converting
Langerhans) glycogen → glucose
Aspect Details
Location Behind the stomach, near the small intestine
Functions Both exocrine and endocrine functions
Exocrine Role Produces digestive enzymes (amylase, lipase, proteases) that are released into the
small intestine to aid digestion
Endocrine Produces hormones:
Role
- Insulin (lowers blood glucose)
- Glucagon (raises blood glucose)
- Somatostatin (regulates insulin and glucagon release)
Importance Regulates blood sugar levels critical for energy balance and metabolic functions
Disorders Diabetes mellitus (insufficient insulin production or response), pancreatitis,
pancreatic cancer
How Insulin lowers blood sugar levels:
Step Process Effect
1. Insulin Release Pancreas releases insulin in response to Insulin enters the bloodstream
high blood glucose levels
2. Cellular Uptake Insulin binds to receptors on muscle and Signals cells to increase glucose
fat cells uptake from blood and speeds
up conversion rate
3. Glucose Glucose is converted into glycogen in liver Stores excess glucose for future
Conversion and muscles energy needs
4. Reduced Blood Less glucose remains circulating in the Blood sugar levels decrease to
Sugar blood normal range
5. Inhibition of Insulin inhibits glucose production by the Prevents further rise in blood
Glucose Production liver glucose
(Glucagon raises blood sugar levels)
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Strand 2: Life Processes in animals and plants pg. 37 – 89
2.1. Human Endocrine System pg. 37
Term Definition/Explanation
Chemical coordination Slow, prolonged process of communicating information throughout
body using hormones secreted via endocrine glands.
Hormone Organic, chemical substance secreted by an endocrine gland and
carries in the blood stream to its target organ(s) where it regulates
metabolic reactions, e.g. steroid/protein.
Target organ Specific cells that respond to a given hormone and have receptor sites
for it.
Endocrine gland Vascular, ductless gland that secretes hormones throughout
bloodstream to target organs.
Feature Exocrine Glands Endocrine Glands
Definition Glands that secrete substances Glands that secrete hormones
into ducts directly into blood
Mode of Secretion Via ducts to a surface (e.g., skin, Directly into the bloodstream
digestive tract)
Secretion Type Enzymes, sweat, saliva, mucus, Hormones (chemical messengers)
etc.
1. Hypothalamus: Role of ADH (antidiuretic hormone) - osmoreceptors in brain detect change in
osmolarity levels, releases more or less ADH to regulate water levels.
2. Pituitary gland (Master gland):
Hormone (Full Name) Target Organ(s) Main Function(s)
TSH (Thyroid Stimulating Thyroid gland Stimulates the thyroid gland to produce thyroxine
Hormone) (T₄), which regulates metabolism.
FSH (Follicle Stimulating Ovaries (females), Stimulates growth of ovarian follicles and
Hormone) Testes (males) oestrogen secretion in females; initiates sperm
production in males.
LH (Luteinizing Hormone) Ovaries (females), Triggers ovulation and progesterone production in
Testes (males) females; stimulates testosterone secretion in
males.
ICSH (Interstitial Cell Testes (Leydig cells) Stimulates testosterone production in males.
Stimulating Hormone) (Same as LH in males.)
ACTH (Adrenocorticotropic Adrenal cortex Stimulates secretion of cortisol and other
Hormone) glucocorticoids, especially during stress.
Prolactin (Lactogenic Mammary glands Promotes milk production after childbirth and
Hormone) (breasts) maintains lactation.
Oxytocin Uterus and Causes uterine contractions during childbirth and
mammary glands milk ejection (let-down reflex) during
breastfeeding.
1 of 51
,Growth disorders:
Age Hormone Imbalance Condition Description
Group
Children Hypersecretion of Gigantism Abnormally increased height and large body size
Growth Hormone (GH) caused by excessive secretion of GH before the
closure of growth plates.
Children Hyposecretion of Growth Dwarfism Short stature and stunted growth due to
Hormone (GH) insufficient secretion of GH during childhood.
Adults Hypersecretion of Acromegaly Enlargement of hands, feet, and facial features
Growth Hormone (GH) due to excessive GH secretion after the closure of
growth plates.
Children Hyposecretion of Cretinism Mental retardation and physical growth defects
Thyroxine caused by thyroid hormone deficiency during
early development.
3. Thyroid Gland (Butterfly Gland):
Functions: 1Increases basal metabolic rate controlling rate of cellular respiration, 2promotes normal
functioning of heart and 3promotes normal functioning of the nervous system by increasing nervous
activity and sharpening alertness and reflexes.
Negative Feedback System:
1. Low thyroxine levels in the blood are detected by the hypothalamus.
2. The hypothalamus releases TRH (Thyrotropin-Releasing Hormone).
3. TRH stimulates the anterior pituitary to release TSH (Thyroid Stimulating Hormone).
4. TSH stimulates the thyroid gland to produce and release thyroxine (T4).
5. As thyroxine levels rise, they inhibit further release of TRH and TSH.
6. This stops overstimulation of the thyroid, maintaining hormonal balance.
Homeostasis and negative feedback control:
Concept Definition Key Features Example
Homeostasis The process by Involves constant monitoring, Body temperature, blood
which the body regulation, and correction of sugar, water balance, pH,
maintains a stable body conditions hormone levels
internal environment
despite external
changes
Negative A control mechanism Works like a thermostat: Regulation of thyroxine,
Feedback that reverses a when a level is too high or blood glucose (insulin &
change to return the low, corrective action is taken glucagon), body temperature,
body to normal to restore balance water levels (ADH)
How Negative Feedback Works (Basic Steps):
1. Stimulus: A change occurs in the internal environment (e.g., low thyroxine).
2. Receptor: Detects the change (e.g., hypothalamus senses low hormone level).
3. Control Centre: Processes the information and sends signals (e.g., pituitary gland releases
TSH).
4. Effector: Acts to correct the change (e.g., thyroid releases more thyroxine).
5. Response: The internal condition returns to normal, and further stimulation stops.
2 of 51
,Age Hormone Imbalance Condition Description
Group
Children Hyposecretion of Cretinism A condition in infants and children caused
Thyroxine (T₄) by thyroid hormone deficiency; leads to
stunted growth, mental retardation, and
delayed physical development.
Adults Hyposecretion of Myxoedema A condition in adults resulting from low
Thyroxine (T₄) thyroid hormone levels; causes fatigue,
weight gain, swollen face, dry skin, and
slow mental and physical activity.
Hyposecretion of Hypothyroidism General term for underactive thyroid activity —
Thyroxine (T₄) body metabolism slows down, causing weight
gain, tiredness, cold intolerance, and
depression.
Hypersecretion of Hyperthyroidism Overproduction of thyroid hormones leading to
Thyroxine (T₄) (Graves’ Disease) increased metabolism, weight loss, rapid
heartbeat, sweating, irritability, and bulging
eyes (exophthalmos).
Gender / Hormone Imbalance Endocrine Disorder Description / Effect on Fertility
System
Female Hyposecretion of Ovarian Failure / Low levels of female sex hormones
Oestrogen and Hypogonadism lead to failure of ovulation,
Progesterone irregular or absent menstrual
cycles, and inability to conceive.
Female Hypersecretion of Polycystic Ovary Excess production of androgens
Androgens Syndrome (PCOS) (male hormones) disrupts normal
ovulation, causes infertility,
irregular periods, and cysts on
ovaries.
Male Hyposecretion of Testicular Low testosterone levels result in
Testosterone Hypofunction / decreased sperm production,
Hypogonadism reduced libido, and infertility.
Both Hormonal Imbalance in Pituitary Disorders Abnormal secretion of pituitary
(Male & Pituitary Gland (e.g., hormones affects gonadal function
Female) excess Prolactin or low — can inhibit ovulation in females
FSH / LH) or sperm production in males.
Both Thyroid Hormone Hypothyroidism / Both underactive and overactive
(Male & Imbalance Hyperthyroidism thyroid can interfere with
Female) reproductive hormones, leading to
irregular cycles, low sperm count,
or miscarriage risk.
3 of 51
, 4. Pancreas:
Hormone Secreted by Target Function
Organ(s)
Insulin Beta cells (Islets of Liver, Muscles Lowers blood glucose by converting
Langerhans) glucose → glycogen
Glucagon Alpha cells (Islets of Liver Increases blood glucose by converting
Langerhans) glycogen → glucose
Aspect Details
Location Behind the stomach, near the small intestine
Functions Both exocrine and endocrine functions
Exocrine Role Produces digestive enzymes (amylase, lipase, proteases) that are released into the
small intestine to aid digestion
Endocrine Produces hormones:
Role
- Insulin (lowers blood glucose)
- Glucagon (raises blood glucose)
- Somatostatin (regulates insulin and glucagon release)
Importance Regulates blood sugar levels critical for energy balance and metabolic functions
Disorders Diabetes mellitus (insufficient insulin production or response), pancreatitis,
pancreatic cancer
How Insulin lowers blood sugar levels:
Step Process Effect
1. Insulin Release Pancreas releases insulin in response to Insulin enters the bloodstream
high blood glucose levels
2. Cellular Uptake Insulin binds to receptors on muscle and Signals cells to increase glucose
fat cells uptake from blood and speeds
up conversion rate
3. Glucose Glucose is converted into glycogen in liver Stores excess glucose for future
Conversion and muscles energy needs
4. Reduced Blood Less glucose remains circulating in the Blood sugar levels decrease to
Sugar blood normal range
5. Inhibition of Insulin inhibits glucose production by the Prevents further rise in blood
Glucose Production liver glucose
(Glucagon raises blood sugar levels)
4 of 51
