GCSE Biology - Human nervous system

What is the definition of homeostasis? (3 marks)

1. It is the regulation of the internal conditions of a cell or organism. 2. It maintains optimum conditions for function in response to internal and external changes. 3. It is essential for maintaining optimal conditions for enzyme action and all cell functions.

Name three internal conditions controlled by homeostasis in the human body. (3 marks)

Blood glucose concentration. Body temperature. Water levels.

What are the three main components of all automatic control systems? (3 marks)

1. Receptors: Cells that detect stimuli (changes in the internal or external environment). 2. Coordination centres: Areas such as the brain, spinal cord, and pancreas that receive and process information from receptors. 3. Effectors: Muscles or glands that bring about responses which restore optimum levels.

Compare the coordination of the endocrine (hormonal) system with the nervous system. (3 marks)

1. The endocrine system is slower. 2. The endocrine system produces longer-lasting effects. 3. The endocrine system uses chemical transmission (hormones) via the blood, whereas the nervous system uses electrical impulses via neurones.

What is the overall purpose of the nervous system? (2 marks)

1. It enables humans to react to their surroundings. 2. It allows humans to coordinate their behaviour.

Describe the pathway of a nervous response. (5 marks)

1. A stimulus is detected by a receptor. 2. Information passes along sensory neurones as electrical impulses to the central nervous system (CNS). 3. The CNS (the brain and spinal cord) acts as the coordinator. 4. Impulses are sent along motor neurones to an effector. 5. The effector brings about a response.

What is a reflex action, and why is it important? (3 marks)

1. Reflex actions are automatic and rapid. 2. They do not involve the conscious part of the brain. 3. They are important because they help avoid danger/harm and take care of basic body functions like breathing.

Give two examples of reflex actions. (2 marks)

1. Releasing saliva when food enters the mouth. 2. Withdrawing the hand from a sharp object.

Describe the detailed sequence of events in a reflex arc when a person touches a hot object. (6 marks)

1. A receptor in the skin detects a stimulus (e.g., pressure or heat) and generates an electrical impulse. 2. A sensory neurone conducts the electrical impulse to the spinal cord (CNS). 3. At a synapse, a chemical (neurotransmitter) is released and diffuses across the gap. 4. This chemical stimulates a new electrical impulse in a relay neurone. 5. The impulse travels across another synapse to a motor neurone, which carries it to the effector. 6. The effector (a muscle) contracts to carry out the response (pulling the hand away).

Describe a method to investigate the effect of caffeine on human reaction time (RPA 7). (6 marks)

1. Use the ruler drop test: one person holds a ruler vertically above the subject's thumb and drops it without warning. 2. Ensure the starting position of the ruler is exactly at 0 cm. 3. Record the distance the ruler falls before being caught and convert this distance to a reaction time. 4. Test the subject without caffeine, then with caffeine. 5. Calculate a mean value for each condition, eliminating any anomalies. 6. Maintain strict control variables: the subject's age, biological sex, BMI, amount of sleep, volume/concentration of the drink, and the time interval between drinking and testing.

Give two ways to improve the precision and validity of the ruler drop test. (2 marks)

1. Use a more precise scale, such as a ruler with a millimetre (mm) scale. 2. Ensure the subject rests their hand/arm on the table to stop them moving their arm up to catch the ruler.

What is the brain made of and what is its function? (2 marks)

1. It is made of billions of interconnected neurones. 2. It controls complex behaviour.

Name the three main regions of the brain and describe their functions. (6 marks)

1. Cerebral cortex: Concerned with consciousness, intelligence, memory, and language. 2. Cerebellum: Concerned mainly with coordinating muscular activity and balance. 3. Medulla: Concerned with unconscious activities, such as controlling the heartbeat, movements of the gut, and breathing.

How have neuroscientists mapped the regions of the brain? (3 marks)

1. By studying patients with brain damage (matching changes in behaviour to damaged areas). 2. By electrically stimulating different parts of the brain (during conscious surgery). 3. By using MRI scanning techniques.

Give three advantages of using a modern fMRI scanner to investigate brain function compared to a traditional MRI scanner. (3 marks)

1. You can ask people to do specific tasks while taking the scan. 2. You can see exactly which part of the brain is active or inactive. 3. You can compare it with a person without brain damage to see exactly where the damage is.

Why is investigating and treating brain disorders very difficult? (3 marks)

1. The brain is incredibly complex and delicate. 2. It is encased within the skull, making it hard to access. 3. Surgery or treatment carries a high risk of causing unintended damage to vital functions.

What is the eye and what receptors does it contain? (2 marks)

1. The eye is a sense organ. 2. It contains receptors sensitive to light intensity and colour.

Describe the function of the sclera, cornea, and optic nerve. (3 marks)

1. Sclera: The tough, white outer layer that protects the eyeball. 2. Cornea: The transparent region at the front that lets light in and refracts (bends) light rays towards the retina. 3. Optic nerve: Carries sensory electrical impulses from the retina to the brain.

Describe how the retina and optic nerve function to allow a person to see. (3 marks)

1. Receptor cells in the retina are sensitive to light and detect it. 2. An electrical impulse passes along a sensory neurone. 3. The impulse travels along the optic nerve to the brain, which interprets it as a visual image.

Describe the pupil reflex in bright light. (3 marks)

1. Circular muscles in the iris contract. 2. Radial muscles in the iris relax. 3. The pupil constricts (gets smaller) to reduce the amount of light entering and prevent damage to the retina.

Describe the pupil reflex in dim light. (3 marks)

1. Circular muscles relax. 2. Radial muscles contract. 3. The pupil dilates (widens) to let as much light as possible enter the eye.

What is accommodation? (1 mark)

The process of changing the shape of the lens to focus on near or distant objects.

Explain how the eye focuses on a near object (e.g., reading a book). (4 marks)

1. The ciliary muscles contract (reducing their diameter). 2. The suspensory ligaments loosen (slacken). 3. The lens thickens and becomes more curved/rounded. 4. The thicker lens is more convergent, refracting light rays strongly so they focus precisely on the retina.

Explain how the eye focuses on a distant object. (4 marks)

1. The ciliary muscles relax. 2. The suspensory ligaments are pulled tight. 3. The lens is pulled flat and thin. 4. The lens only slightly refracts light rays so they focus on the retina.

Name the defect where light focuses behind the retina, explain its cause, and how it is corrected. (3 marks)

1. The defect is hyperopia (long-sightedness). 2. It is caused by the eyeball being too short or the lens not being able to thicken enough. 3. It is treated using spectacles with a convex (converging) lens, which refracts light rays inwards more so they focus on the retina.

Name the defect where light focuses in front of the retina, explain its cause, and how it is corrected. (3 marks)

1. The defect is myopia (short-sightedness). 2. It is caused by the eyeball being too long or the lens being too curved. 3. It is treated using spectacles with a concave lens, which spreads light rays out before they enter the eye, allowing the image to focus on the retina.

List three new technologies used to treat eye defects other than traditional spectacle lenses. (3 marks)

1. Hard and soft contact lenses. 2. Laser surgery (to change the shape of the cornea). 3. Replacement lenses implanted in the eye.

Where is body temperature monitored and controlled? (2 marks)

1. In the thermoregulatory centre in the brain, which contains receptors sensitive to the temperature of the blood. 2. The skin also contains temperature receptors that send nervous impulses to the thermoregulatory centre.

Explain why increased physical activity increases body temperature. (2 marks)

1. Activity and movement require energy from respiration. 2. Respiration (or metabolism) is an exothermic reaction that releases heat, which increases body temperature.

Explain how the body lowers its temperature when it is too high. (4 marks)

1. Blood vessels supplying the skin capillaries dilate (vasodilation). 2. More blood flows near the surface of the skin, so more heat energy is lost to the environment. 3. Sweat is produced from the sweat glands. 4. As sweat evaporates, it causes a transfer of energy from the skin to the environment, cooling the body.

Explain why less cooling occurs when humidity is high. (2 marks)

1. Less sweating occurs, or less sweat is able to evaporate. 2. So less heat is lost, as less heat is used for the evaporation of water/sweat.

Explain how the body raises its temperature when it is too low. (4 marks)

1. Blood vessels supplying the skin capillaries constrict (vasoconstriction). 2. This restricts blood flow near the skin surface, reducing energy loss. 3. Sweating stops. 4. Skeletal muscles contract rapidly (shiver); this requires respiration, which releases heat energy to warm the body.

Explain how having a lower body temperature gradient (a smaller difference between body temperature and air temperature) helps an animal survive in a cold environment. (2 marks)

1. The animal loses less energy (heat) from its body. 2. Therefore, its body energy store (glycogen/fat) lasts longer, and more energy is available for processes vital for life (such as brain and heart function).

Why do athletes drink sports drinks containing ions after heavy sweating? (1 mark)

To replace the ions/salt lost in sweat and prevent muscle cramp.