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:

Feature

Nervous System

Hormonal System

Speed

Fast

Slower

Duration

Short-term

Long-term

Signal type

Electrical/chemical

Chemical (hormones)

Specificity

Precise targets

Broader targets

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