B5.1 How do substances get into, out of, and around our bodies? (F) & (H)

Definitions:

• Active transport: The movement of particles from an area of low concentration to an area of high concentration, against the concentration gradient. This requires energy.

• Diffusion: The net spreading out of particles from a high concentration to a lower concentration (down their concentration gradient). Energy is not required, so it is a passive process.

• Osmosis: The net movement of water molecules from a region of high concentration to a region of low concentration through a partially permeable membrane.

🚪 Entry & Exit:

• Substances Move:

  • Diffusion: Oxygen enters cells and carbon dioxide leaves.

  • Osmosis: Water moves into cells.

  • Active Transport: Nutrients like glucose enter cells even if there’s more inside the cell.

💓 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.

B5.2 How does the nervous system help us respond to changes? (F) & (H)

Definitions:

• Central nervous system (CNS): The brain and the spinal cord.

• Neurotransmitter: Signaling molecules that transmit impulses from one neuron to the next.

• Reflex arc: The pathway of neurons involved in a reflex action: stimulus → sensory neuron → relay neuron → motor neuron → effector → response.

🧠 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).

B5.3 How do hormones control responses in the human body? (F) & (H)

Definitions:

• Adrenaline: A hormone released by the adrenal gland that increases heart and breathing rates. It is involved in the fight-or-flight response. It also raises blood sugar levels by increasing the conversion of glycogen into glucose.

• Antidiuretic hormone (ADH): A hormone secreted by the pituitary gland that increases water reabsorption in the kidney by making the kidney tubules more permeable to water.

• Endocrine glands: Tissues or organs that are specialized to produce and secrete hormones directly into the bloodstream.

💡 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.

B5.4 Why do we need to maintain a constant internal environment? (F) & (H)

Definitions:

• Homeostasis: Maintenance of constant internal conditions.

• Vasoconstriction: The constriction of blood vessels when the body is too cold. This reduces heat loss from the blood.

• Vasodilation: The dilation of blood vessels when the body is too hot. This increases heat loss from the blood.

🌡 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.

B5.5 What role do hormones play in human reproduction? (H)

Definitions:

• Follicle-stimulating hormone (FSH) is a female reproductive hormone released by the pituitary gland. It is responsible for the maturation of an egg in the ovary and the production of Oestrogen.

• Luteinizing hormone (LH): A female reproductive hormone released by the pituitary gland that stimulates the release of an egg from the ovary (ovulation).

• Oestrogen: A female sex hormone produced in the ovaries that regulate the menstrual cycle and controls the development of secondary sexual characteristics.

• Progesterone: The hormone that maintains the uterus lining during the later stages of the menstrual cycle and in pregnancy.

🔄 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.

B5.6 What can happen when organs and control systems stop working? (F) & (H)

Definitions:

• Diabetes: A condition where the body cannot properly regulate blood sugar levels.

  • Type 1: The pancreas fails to produce insulin resulting in high blood sugar levels.

  • Type 2: A condition in which a person develops insulin resistance or doesn't produce enough insulin.

• Urea: A product of excess amino acid breakdown in the liver. It is the main waste product in urine.

🩺 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.