Endocrine System
Hormones🃏 Flashcard Drill — Endocrine System
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Master Gland
Pituitary Hormone Map
| Hormone | Target | Effect |
|---|---|---|
| TSH | Thyroid gland | Stimulates thyroxin production |
| FSH | Ovary / Testes | Stimulates follicle growth (ovary) / Sperm production (testes) |
| LH | Ovary | Triggers ovulation; forms corpus luteum |
| Prolactin | Mammary glands | Stimulates breast milk production |
| ACTH | Adrenal gland | Stimulates cortisone & aldosterone |
| ICSH | Testes | Stimulates testosterone production |
| GH | Skeleton & muscles | Promotes growth — hypersecretion = gigantism; hyposecretion = pituitary dwarfism |
| ADH | Distal/collecting duct | Makes tubules more permeable — increases water reabsorption (secreted by hypothalamus, stored in pituitary) |
Other Glands
Thyroid & Pancreas
🦋 Thyroid Gland
- Butterfly-shaped on the trachea, below the larynx
- Produces thyroxin — regulates metabolic rate, heart function, neuron awareness
- Hypothyroidism → Adults: myxoedema; Children: cretinism
- Hyperthyroidism → High metabolic rate, rapid heart rate
🫁 Pancreas (Dual-Function Gland)
- Attached to the small intestine
- Both endocrine (hormones) and exocrine (digestive enzymes)
- Islets of Langerhans = endocrine part
Alpha cells → glucagon (↑ glucose)
Beta cells → insulin (↓ glucose) - Diabetes 1: autoimmune; insulin-dependent; starts in childhood
- Diabetes 2: non-insulin dependent; cells don't respond to insulin
Self-Test
Endocrine Quick Quiz
Q1
Which gland is BOTH endocrine and exocrine?
Q2
A child has hypersecretion of GH from the pituitary gland. What disorder results?
Q3
Alpha cells of the islets of Langerhans secrete glucagon. What does glucagon do?
Reproduction
Male · Female · Strategies🃏 Flashcard Drill — Reproduction
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Sequence
Fertilisation → Implantation Steps
- Fertilisation in the Fallopian tube → Zygote formed
- Zygote undergoes mitosis as it travels toward uterus
- Solid ball of cells = Morula
- Hollow ball of cells = Blastocyst
- Blastocyst implants into the endometrium
- Chorionic villi grow to attach blastocyst to endometrium
- Chorion = outermost layer; has capillary network
- Placenta secretes progesterone and provides a barrier; foetal and maternal blood never mix
⚠️ Exam Watch
In the placenta, the VEIN carries oxygenated blood with nutrients to the embryo. The ARTERY carries deoxygenated blood with wastes away. This is opposite to normal body vessels!
28-Day Cycle
Menstrual Cycle — Hormones & Sequence
📈 Hormone Peaks — MUST KNOW
- FSH — peaks TWICE: once for Graafian follicle development, again to stimulate ovulation
- LH — peaks ONCE ONLY at day 14 ovulation; also forms corpus luteum
- Oestrogen — peaks TWICE: just before and just after ovulation
- Progesterone — peaks ONLY after ovulation; stays constant in pregnancy (does not dip)
🔄 Uterine Cycle Steps
- 1. Oestrogen repairs & thickens endometrium
- 2. Ovulation occurs (day 14)
- 3. Corpus luteum releases progesterone
- 4. Progesterone makes endometrium thicker & more vascular
- 5. High oestrogen & progesterone inhibit FSH & LH
- 6–10. If no pregnancy: corpus luteum shrinks → progesterone drops → oestrogen drops → endometrium falls away → FSH rises again
Strategies
External vs Internal · Ovipary · Vivipary
| Strategy | Where eggs develop | Advantages | Disadvantages |
|---|---|---|---|
| External fertilisation | Water | Large number of gametes; courtship brings gametes closer | Wasteful — many eggs; fertilisation not certain |
| Internal fertilisation | Inside parent | More certain; fewer gametes needed; protection | Finding a mate; fewer opportunities; longer gestation |
| Ovipary | Outside parent (laid as eggs) | More yolk; more protection; parental care possible | Land eggs susceptible to predators |
| Ovovivipary | Inside parent (no shell; hatches internally) | Large yolk; protected from predators; born fully developed | Fewer offspring; parent carries risk |
| Vivipary | Inside parent (no shell; born live) | Nourishment & protection via placenta; parental care | Fewer eggs; long gestation |
Self-Test
Reproduction Quick Quiz
Q1
What is the site of fertilisation in humans?
Q2
A solid ball of cells formed during early embryonic development is called a:
Q3
Which hormone keeps the smooth muscles of the uterus relaxed during pregnancy?
Nervous System
Brain · Spinal Cord · Neurons🃏 Flashcard Drill — Nervous System
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Pathway
Reflex Arc — 8 Steps
- Stimulus detected
- Sensory neuron carries impulse toward CNS
- Enters spinal cord via Dorsal Root
- Impulse enters Grey matter of spinal cord
- Interneuron (relay neuron) connects sensory to motor
- Leaves via Ventral root
- Motor neuron carries impulse to effector
- Effector (muscle or gland) responds
Brain Regions
Cerebrum · Cerebellum · Medulla
🧩 Cerebrum
- 4 lobes: frontal, parietal, temporal, occipital
- Corpus callosum connects hemispheres
- Ventricles filled with CSF for cushioning
- Gyri & sulci increase surface area
- White matter (myelinated axons) & grey matter (cell bodies)
🎯 Cerebellum
- Co-ordinates voluntary movement
- Provides muscle tone
- Maintains posture and balance
🫀 Medulla Oblongata
- Located in the brainstem
- Pathway to and from brain
- Controls breathing and heartbeat
- Less important reflexes: sneezing, coughing
📌 Meninges — Outer to Inner
Dura mater (outer) → Arachnoid (middle) → Pia mater (inner). Function: protection of the brain and spinal cord.
Self-Test
Nervous System Quick Quiz
Q1
Which part of the nervous system is responsible for 'rest and digest'?
Q2
Multiple sclerosis is classified as what type of disease?
Homeostasis
Regulation & FeedbackOsmoregulation
ADH — Water Balance Control
🏜️ Low Water in Blood (hot day / sweating)
- Hypothalamus detects low water (high osmolarity)
- Pituitary gland secretes MORE ADH
- ADH sent to distal and collecting duct
- Tubules become MORE permeable
- More water reabsorbed into blood
- SMALL volume of concentrated urine produced
🌊 High Water in Blood
- Hypothalamus detects high water (low osmolarity)
- Pituitary secretes LESS ADH
- Tubules become LESS permeable
- Less water reabsorbed
- LARGE volume of dilute urine produced
📌 Aldosterone Pathway
Low blood salt → Afferent arterioles secrete renin → Renin triggers angiotensin → Stimulates adrenal gland to secrete aldosterone → More sodium reabsorbed → More water reabsorbed → Blood volume rises.
Glucose Regulation
High & Low Blood Glucose Pathways
🍚 High Glucose (after eating)
- Blood glucose increases
- Beta cells in pancreas detect increase
- Insulin secreted
- Liver & muscles absorb glucose; liver converts to glycogen
- Blood glucose drops → negative feedback stops insulin
🥜 Low Glucose (starving)
- Blood glucose decreases
- Alpha cells in pancreas detect decrease
- Glucagon secreted
- Liver converts glycogen back to glucose
- Blood glucose rises → negative feedback stops glucagon
Thermoregulation
Hot Day vs Cold Day Responses
| Mechanism | Hot Day | Cold Day |
|---|---|---|
| Circular muscles (dermal arterioles) | Relax → vasodilation → more blood to surface → more heat lost | Contract → vasoconstriction → less blood to surface → less heat lost |
| Shunt vessels | Contract → less blood diverted to subcutaneous layer | Relax → more blood diverted away from surface |
| Sweating | Increases → evaporation removes heat | Decreases → less heat lost |
| ADH effect | More ADH secreted (sweating causes dehydration) | Less ADH secreted |
Self-Test
Homeostasis Quick Quiz
Q1
On a hot day when you sweat a lot, what happens to ADH secretion?
Q2
Which cells in the pancreas detect an INCREASE in blood glucose?
Plant Hormones
Auxins · Gibberellins · ABA🃏 Flashcard Drill — Plant Hormones
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Auxins
Phototropism & Geotropism Explained
☀️ Phototropism (light)
- Auxins move away from light → accumulate on DARK side
- Dark side: auxins stimulate cell elongation → cells get longer
- Light side: cells stay small/short
- Result: stem bends towards the light
- Shoots = positively phototropic
🌍 Geotropism (gravity)
- Auxins are attracted to gravity → sink to lower region
- In STEMS: auxins stimulate elongation → bend upwards (negatively geotropic)
- In ROOTS: auxins INHIBIT elongation → cells on lower side don't elongate → root bends downward (positively geotropic)
| Hormone | Key Functions | What it does NOT do |
|---|---|---|
| Auxins | Cell elongation; apical dominance; tropisms; made at apical tip | Seed germination; stem elongation between internodes |
| Gibberellins | Elongation of main stem (internode spacing); stimulates seed germination; breaks dormancy | Does NOT affect apical dominance |
| Abscisic acid (ABA) | Growth INHIBITOR; causes stomata to CLOSE; promotes dormancy in seeds and buds | Does not stimulate growth |
Senses
Eye · Ear · Skin🃏 Flashcard Drill — Senses
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Eye
Eye Structures & Visual Defects
| Defect | Eyeball shape | Image focus | Correction |
|---|---|---|---|
| Myopia (short-sighted) | Too LONG | In FRONT of retina | CONCAVE lens |
| Hypermetropia (long-sighted) | Too SHORT / cornea too flat | BEHIND retina | CONVEX lens |
| Astigmatism | Irregularly shaped cornea or lens | Blurred/distorted | Corrective lenses |
| Cataracts | Normal shape | Cloudy — proteins clump in lens | Surgery to remove hardened layer |
📌 Accommodation — Near vs Far
Near object: Ciliary muscles CONTRACT → ring gets smaller → suspensory ligaments SLACK → lens becomes FAT/convex → refracts light more.Far object: Ciliary muscles RELAX → ring gets larger → suspensory ligaments TAUT → lens becomes THIN → refracts light less.
Ear
Balance vs Posture — Key Distinction
🌀 Balance (change in speed/direction)
- Organ: Semicircular canals
- Receptor: Cristae
- Stimulus: change in speed or direction of movement
- Impulse → cerebellum via auditory nerve → muscles restore balance
🧍 Posture (head position)
- Organ: Utriculus and sacculus
- Receptor: Maculae
- Stimulus: change in position of head in space
- Impulse → cerebellum via auditory nerve → muscles restore posture
Human Evolution
Apes · Hominids · Evidence🃏 Flashcard Drill — Human Evolution
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Comparison
Ape vs Human Skull & Skeleton
| Feature | Ape | Human |
|---|---|---|
| Jaw | Prognathous (projects forward) | Non-prognathous (flat) |
| Foramen magnum | Positioned towards back | Positioned forwards/downwards |
| Palate shape | Rectangular | Parabolic (curved) |
| Brow ridges | Present and heavy | Absent or very reduced |
| Cranium | Small | Large |
| Canine teeth | Large | Small |
| Pelvis | Narrow and long | Broad and short |
| Big toe | Divergent (grasping) | Convergent (aligned) |
| Spine shape | C-shaped | S-shaped |
📌 Bipedalism Skeletal Requirements
Short, broad pelvis · S-shaped spine · Large heel bone · Convergent big toe · Foramen magnum positioned forwards/downwards
Evidence
3 Types of Evolutionary Evidence + Key Fossils
🦴 Fossil Evidence
Skeletal remains, endocasts, footprints. Example: Laetoli footprints (bipedalism), Taung Child skull.
🧬 Genetic Evidence
DNA comparison, mitochondrial DNA tracing. Example: mtDNA traces all humans to African ancestor.
🔥 Cultural Evidence
Tools, fire-making, art, burial practices. Example: Oldowan stone tools (H. habilis); fire use (H. erectus).
| Species | Fossil Name | Location | Discoverer |
|---|---|---|---|
| Ardipithecus ramidus | 'Ardi' | Ethiopia | Tim White |
| A. afarensis | 'Lucy' | Ethiopia | Donald Johanson |
| A. afarensis | Laetoli footprints | Tanzania | Mary Leakey |
| A. africanus | Taung Child | South Africa | Raymond Dart |
| A. africanus | Mrs Ples | South Africa | Robert Broom |
| A. africanus | Little Foot | South Africa | Ronald Clarke |
| H. habilis | Handy Man | Olduvai, Tanzania | Louis Leakey |
Genetics
Crosses · Mutations · Blood Groups🃏 Flashcard Drill — Genetics
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Key Concept
3 Types of Dominance + Ratios
| Type | Definition | Cross Ratio | Example |
|---|---|---|---|
| Complete dominance | One allele completely masks the other in the phenotype | 3:1 (heterozygous × heterozygous) or 1:1 (heterozygous × homozygous recessive) | Tall (T) masks short (t) |
| Incomplete dominance | Neither allele is dominant — an intermediate phenotype is expressed | 1:2:1 (heterozygous × heterozygous) | Red × White → Pink flowers |
| Co-dominance | BOTH alleles are expressed in the phenotype simultaneously | 1:2:1 (uses two DIFFERENT letters) | Blood group AB — both A and B antigens present |
⚠️ Co-dominance vs Incomplete Dominance
Co-dominance: BOTH traits show (e.g. roan cattle — red AND white patches). Incomplete dominance: a BLEND appears (e.g. pink — not red, not white, something in between). Use TWO DIFFERENT letters for co-dominance; always provide a key if using your own letters.
Protein Synthesis
Transcription · Translation🃏 Flashcard Drill — Protein Synthesis
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Step 1
Transcription (Nucleus)
- Double helix unwinds
- DNA unzips — weak hydrogen bonds break
- ONE strand acts as a template
- Free-floating RNA nucleotides from the nucleoplasm attach
- Base pairing: A-U and G-C (RNA uses Uracil, not Thymine)
- mRNA strand produced
- mRNA carries the coded message and moves from nucleus to cytoplasm
- mRNA attaches to a ribosome
Step 2
Translation (Ribosome)
- mRNA inserts into the ribosome
- Ribosome reads 3 bases at a time = a codon
- Each codon matches with a complementary anticodon on tRNA
- tRNA delivers its amino acid
- Amino acids form peptide bonds
- A polypeptide/protein is built
📌 Key Distinctions
Codon = 3 bases on mRNA · Anticodon = 3 bases on tRNA · tRNA carries the amino acid to the ribosome · DNA replication uses A-T and G-C (no U) · Transcription uses A-U and G-C
Meiosis & Mitosis
Cell Division🃏 Flashcard Drill — Meiosis
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Comparison
Meiosis 1 vs Meiosis 2
Meiosis 1
- Double-stranded chromosomes
- Homologous pairs line up at equator
- Crossing over takes place (chiasmata)
- Homologous pairs separate
- Result: 2 non-identical HAPLOID cells
Meiosis 2
- Single-stranded (or recombinant) chromosomes
- Single chromosomes line up at equator
- NO crossing over
- NO homologous pairs present
- Result: 4 non-identical HAPLOID cells
| Term | Definition |
|---|---|
| Synapsis | When homologous pairs move towards each other |
| Bivalent | When homologous pairs are touching |
| Chiasmata | The point at which homologous pairs touch/exchange genes |
| Crossing over | Where homologous pairs exchange genes to increase variation |
| Recombinant chromosome | Chromosome that has exchanged genes with its homologous partner — now contains different combination of genes |
| Centromere | Structure that joins two chromatids together |
| Homologous pair | Two chromosomes carrying similar genes — one from mother, one from father |