Unit 5: The Human Body - Staying Alive (Biology B OCR GCSE)
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:
Deoxygenated Blood: Enters right atrium ➡ right ventricle ➡ lungs.
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:
Stimulus detected by receptors.
Sensory neuron transmits signals to the spinal cord.
Relay neuron processes signal.
The motor neuron sends a signal to an effector (muscle/gland).
The effector produces a response (e.g., moving the hand away from heat).
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.
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.
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.
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.
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:
Deoxygenated Blood: Enters right atrium ➡ right ventricle ➡ lungs.
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:
Stimulus detected by receptors.
Sensory neuron transmits signals to the spinal cord.
Relay neuron processes signal.
The motor neuron sends a signal to an effector (muscle/gland).
The effector produces a response (e.g., moving the hand away from heat).
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.
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.
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.
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.
