Unit 5: The Human Body - Staying Alive (Biology B OCR GCSE)

Active transport

Movement of particles from low to high concentration, requires energy.

Diffusion

Spreading out of particles from high to low concentration, passive process.

Osmosis

Movement of water from high to low concentration through a membrane.

Entry & Exit

• Diffusion: Oxygen in, carbon dioxide out.

• Osmosis: Water into cells.

• Active Transport: Glucose into cells.

Cardiac System

• Heart Function:

  1. Deoxygenated Blood: Enters right atrium ➡ right ventricle ➡ lungs.

  2. Oxygenated Blood: Returns to left atrium ➡ left ventricle ➡ body.

🩸 Blood Vessels

• Arteries: Thick walls, high pressure, carry blood away from the heart.

• Veins: Valves prevent backflow and low pressure, and carry blood to the heart.

• Capillaries: Thin walls for exchange, connect arteries and veins.

🧠 Nervous System

• Central (CNS): The brain and spinal cord control the body's responses.

• Peripheral: Sensory neurons detect stimuli; motor neurons create responses.

🔌 Neurons

• Types: Sensory (input), relay (processing), motor (output).

• Synapse: Neurotransmitters cross the gap between neurons to continue the impulse.

⚡ Reflex Arc

1. Stimulus detected by receptors.

2. Sensory neuron transmits signals to the spinal cord.

3. Relay neuron processes signal.

4. The motor neuron sends a signal to an effector (muscle/gland).

5. The effector produces a response (e.g., moving the hand away from heat).

💡 Endocrine System

• Hormone Production: Glands like the pituitary and adrenal release hormones into the blood.

• Hormone Function: Hormones like insulin regulate blood sugar; adrenaline prepares the body for stress.

⚖ Negative Feedback

• Thyroxine: Regulates metabolism; if levels drop, more is produced until balanced.

• Adrenaline: Increases heart rate and glucose; body calms once the stress is gone.

🌡 Homeostasis

• Keeps internal conditions optimal for cell function, like temperature and water balance.

🔥 Temperature Regulation

• Cold: Shivering generates heat; vasoconstriction reduces heat loss.

• Hot: Sweating cools the body; vasodilation increases heat loss.

💧 Water Balance

• Kidneys: Filter blood, and regulate water.

• ADH: Adjusts water reabsorption in kidneys to maintain balance.

🔄 Menstrual Cycle

• FSH: Stimulates egg maturation and oestrogen production.

• LH: Triggers ovulation.

• Oestrogen: Thickens uterus lining; controls secondary sex traits.

• Progesterone: Maintains uterus lining for potential pregnancy.

💊 Contraception

• Hormonal Methods: Pills contain oestrogen and progesterone to prevent ovulation and pregnancy.

🩺 Blood Sugar Regulation

• Insulin: Lowers blood sugar; produced by the pancreas.

• Glucagon: Raises blood sugar; also from the pancreas.

💉 Diabetes

• Type 1: No insulin production; treated with insulin injections.

• Type 2: Insulin resistance; managed with diet, exercise, and medication.

👁 Eye Functions

• Parts: Cornea (focuses light), iris (controls light entry), lens (focuses light), retina (detects light).

• Defects:

  • Short-sightedness: Light focuses in front of the retina; distant objects are blurry.

  • Long-sightedness: Light focuses behind the retina; close objects are blurry.

Cataracts: Clouding of the lens, obstructing vision.

🧬 Neurone Damage

• Permanent: Once damaged, neurons typically don't regenerate, making nervous system injuries severe and hard to treat.