Flashcards - 5.2 Human Nervous System - AQA Biology GCSE

What is the function of the nervous system?

The nervous system allows the body to react to its surroundings and coordinate an appropriate response.

How does a stimulus lead to a response being carried out by the body?

Stimulus is converted into an electrical impulse by the receptors, which passes along sensory neurones to the CNS, which coordinates a response and sends an impulse along motor neurones to the effector.

What sequence of events describes how the nervous system works?

Stimulus → receptor → coordinator → effector → response.

What is a reflex action?

A reflex action is an automatic and rapid response which does not involve any conscious input from the brain.

Describe how a reflex action occurs via a reflex arc.

The stimulus is detected by a receptor, an electrical impulse travels to the spinal cord via a sensory neurone, crosses synapses to a relay neurone, then to a motor neurone, and the effector carries out the response.

What is the difference between a reflex pathway and a conscious pathway?

A reflex pathway's coordination centre is a relay neurone in the spinal cord, while a conscious pathway has its coordination centre in the conscious part of the brain.

What is the function of the cerebral cortex?

Controls consciousness, intelligence, memory, and language.

What is the function of the medulla?

Controls unconscious activities such as breathing and heart rate.

Why is the investigation and treatment of the brain difficult?

The brain is complex, easily damaged, certain membranes prevent drug access, and the functions of each part are not entirely known.

What methods are used by scientists to determine brain function?

Studying patients with brain damage, electrical stimulation of the brain, MRI scans.

What are the two main functions of structures found within the eye?

Focusing on near or distant objects (accommodation) and adaptation to dim light.

Describe the structure and function of the retina.

The retina is a light-sensitive layer at the back of the eye that sends impulses to the brain when stimulated by light.

Describe the structure and function of the optic nerve.

The optic nerve connects the eye to the brain and carries impulses so that images can be visualized.

Describe the structure and function of the sclera.

The sclera is the tough outer layer of the eye that protects its internal structures.

Describe the structure and function of the cornea.

The cornea is the curved transparent layer at the front of the eye that lets light in and allows it to be focused onto the retina.

Describe the structure and function of the iris.

The iris is a muscle that controls the size of the pupil by contracting or relaxing to adjust to lighting conditions.

Describe the structure and function of the ciliary muscles and suspensory ligaments.

Ciliary muscles and suspensory ligaments hold the lens in place and control its shape.

Describe how the iris alters the size of the pupil in bright light.

In bright light, circular muscles contract and radial muscles relax, making the pupil smaller to avoid retinal damage.

Describe how the iris alters the size of the pupil in dim light.

In dim light, circular muscles relax and radial muscles contract, making the pupil larger to allow more light in.

What is accommodation?

Accommodation is the alteration of the lens’s shape to focus on near or distant objects.

How does the eye focus on a nearby object?

Ciliary muscles contract, suspensory ligaments loosen, and the lens becomes thicker and more curved to strongly refract light.

How does the eye focus on a far-away object?

Ciliary muscles relax, suspensory ligaments tighten, and the lens becomes thinner to weakly refract light.

What is myopia?

Myopia (short-sightedness) occurs when the lens of the eye is too curved, causing light to focus in front of the retina.

How can myopia be treated?

Myopia can be treated with glasses that have a concave lens to spread out light rays.

What is hyperopia?

Hyperopia (long-sightedness) occurs when the lens of the eye is too flat, causing light to focus behind the retina.

How can hyperopia be treated?

Hyperopia can be treated with glasses that have a convex lens to bring light rays together.

What are the two types of contact lenses?

There are hard contact lenses, which are rigid and long-lasting, and soft contact lenses, which are flexible and more comfortable.

What is laser eye surgery?

Laser eye surgery uses lasers to fix visual defects by altering the cornea’s thickness or curvature.

How can replacement lenses be used to treat visual defects?

Replacement lenses can be implanted or replace the natural lens, with risks including retinal damage, cataracts, and infections.

What are the risks of lens replacement?

Risks include retinal damage, cataracts, and infections.

Where is body temperature controlled in the body?

Body temperature is controlled by the thermoregulatory centre in the hypothalamus of the brain.

How is temperature monitored by the body?

The thermoregulatory centre has receptors sensitive to blood temperature and skin receptors that send impulses regarding skin temperature.

What physiological changes occur when body temperature is too high?

Vasodilation occurs (blood vessels dilate), and sweating increases, allowing heat to be radiated away.

What physiological changes occur when body temperature is too low?

Vasoconstriction occurs (blood vessels constrict), shivering happens, and sweating stops.