Science Human Biology

How body systems work together:

• Circulatory system transports oxygen, nutrients, and waste.

• Respiratory system brings in oxygen and removes carbon dioxide.

• Digestive system breaks down food into nutrients absorbed into the blood.

• Excretory system (kidneys, lungs, liver, skin) removes waste products.

• These systems interact to maintain homeostasis—e.g., oxygen from lungs travels via blood to cells; nutrients from digestion are transported by blood; waste is removed by kidneys/lungs.

2. Define ‘metabolism’:

• Metabolism is the sum of all chemical reactions in the body that sustain life, including breaking down molecules (catabolism) and building new ones (anabolism).

3. Catabolic vs Anabolic reactions:

• Catabolic: Breaks large molecules into smaller ones (e.g., digestion). Releases energy.

• Anabolic: Builds complex molecules from simpler ones (e.g., protein synthesis). Uses energy.

4. Enzymes: Structure and Function

• Structure: Proteins with a specific 3D shape, including an active site.

• Function: Speed up biochemical reactions by lowering activation energy.

5. Lock and Key Model:

• The enzyme’s active site fits the substrate like a key fits a lock, forming an enzyme-substrate complex, which then forms products.

6. Enzyme Action Diagram (text version):

mathematica

Copy code

Enzyme + Substrate → Enzyme-Substrate Complex → Products + Enzyme

(Label: Enzyme, Substrate, Complex, Products)

7. Factors affecting enzyme activity:

• Temperature: Increases rate to a point; too high denatures enzyme.

• pH: Each enzyme has an optimal pH; extreme pH denatures.

• Enzyme concentration: More enzymes = faster reaction (to a point).

• Substrate concentration: More substrate = faster reaction (until saturation).

8. Enzymes in digestion:

• Break down large food molecules into absorbable units.

  • Amylase (carbs → glucose), protease (proteins → amino acids), lipase (fats → fatty acids/glycerol).

9. Excretion organs:

• Liver: Processes toxins, breaks down amino acids → urea.

• Lungs: Exhale CO₂ (waste from respiration).

• Kidneys: Filter blood, remove urea, excess salts/water in urine.

10. Function of the nervous system:

• Detects stimuli, processes information, and coordinates responses.

11. Central vs Peripheral Nervous Systems:

• CNS: Brain + spinal cord. Processes and sends instructions.

• PNS: Nerves outside CNS. Carries messages to/from CNS.

12. Neuron structure and function:

• Structure: Cell body, dendrites, axon.

• Function: Transmit electrical impulses.

13. Types of neurons:

• Sensory neurons: Carry signals from receptors to CNS.

• Connector (interneurons): Connect sensory to motor neurons in CNS.

• Motor (effector) neurons: Carry signals from CNS to muscles/glands.

14. Nerve signal transmission:

• Electrical impulse travels along axon; at synapse, neurotransmitters carry signal to next neuron.

15. Brain diagram labels:

• Cerebrum, Cerebellum, Medulla oblongata, Hypothalamus, Pituitary gland.

16. Brain region functions:

• Cerebrum: Thinking, memory, senses.

• Cerebellum: Movement, balance.

• Medulla oblongata: Involuntary actions (e.g., breathing).

• Hypothalamus: Controls temperature, hunger, thirst; links to endocrine system.

• Pituitary gland: "Master gland" that releases many hormones.

17. Reflex vs normal response:

• Reflex: Automatic, fast, no conscious control (e.g., pulling hand from flame).

• Normal response: Involves processing in the brain.

18. Reflex arc pathway:

Stimulus → Receptor → Sensory neuron → Interneuron (spinal cord) → Motor neuron → Effector (muscle/gland) → Response

19. Protective role of reflexes:

• Quick reactions to danger (e.g., blink, withdraw from pain) reduce injury.

20. Purpose of endocrine system:

• Produces hormones to regulate growth, metabolism, mood, reproduction, and homeostasis.

21. Endocrine glands diagram labels:

• Pituitary, thyroid, adrenals, pancreas, ovaries/testes, pineal gland.

22. Functions affected by hormones:

• Growth, blood sugar, water balance, metabolism, puberty, stress, sleep.

23. Hormone targeting:

• Hormones travel in blood but only affect target cells with matching receptors.

24. Hypothalamus and pituitary gland relationship:

• Hypothalamus controls the pituitary gland by releasing hormones that stimulate or inhibit pituitary hormone release.

25. Define homeostasis:

• Maintenance of a stable internal environment despite external changes.

26. Negative-feedback system:

• A change triggers a response that reverses the original change (e.g., too hot → sweat → cool down).

27. Pancreas & insulin in glucose regulation:

• Pancreas detects high blood glucose → releases insulin → cells absorb glucose → lowers blood sugar.

28. Endotherm vs Ectotherm:

• Endotherm: Regulates internal body temperature (e.g., humans).

• Ectotherm: Body temperature depends on environment (e.g., lizards).

29. Hormonal and nervous control:

• Nervous system: Fast, electrical signals, short-term.

• Hormonal system: Slower, chemical signals (hormones), longer-lasting effects.

30. Comparison of hormones and nerves:

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