B10 - Human Nervous System

What is Homeostasis?

Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes

What is homeostasis important for?

Maintaining optimal conditions for enzyme action and all cell functions

What does Homeostasis control in the human body?

Blood glucose concentration, body temperature and water levels

What are the two types of responses for automatic control systems?

Nervous or Chemical responses

What are three features that all control systems need?

All control systems include receptors, coordination centers and effectors.

What are receptors?

Cells that detect changes in the internal or external environment. These changes are known as stimuli. Receptors may be part of the nervous or the hormonal control systems of the body.

What are coordination centers?

Areas that receive and process information from the receptors. They send out signals and coordinate the response of the body. They include the brain which acts as a coordination centre for the nervous and hormonal system, the spinal cord and some organs such as the pancreas

What are Effectors?

Muscles or glands that bring about responses to the stimulus that has been received. These responses restore conditions in the body to the optimum levels

What are neurones?

Special cells that pass along information through electrical impulses

What is the central nervous system made up of?

The brain and the spinal cord

What are sensory neurones?

The cells that carry impulses from your receptors in your sense organs to your CNS

What do Motor neurones do?

They carry information from the CNS to the rest of the body and effectors

A summed up diagram which describes the nervous system

stimulus → receptor → Coordinator(CNS) → Effector

What are Reflex actions?

Automatic and rapid responses which do not involve the conscious part of the brain. They involve sensory, relay and motor neurones. They control everyday functions such as breathing

What is the main stages of a reflex arc?

stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response

What is the brain composed of?

Billions of interconnected neurones that control complex behaviour

What are three examples of regions of the brain?

cerebral cortex, cerebellum and medulla

What does the cerebral cortex do?

The cerebral cortex is concerned with consciousness, intelligence, memory and language.

What does the cerebellum do?

coordinating muscular activity and balance

What does the medulla do?

Concerned with unconscious activities such as controlling the heartbeat, the movements of the gut and breathing

How do scientists map regions of the brain through studying patients with brain damage?

By electrically stimulating different areas of the brain or by using MRI techniques.

What is a detailed description of the eye?

The eye is a sense organ which contains receptors in the retina that are sensitive to light intensity and colour

What does the cornea do?

The tough outer sclera has a transparent region at the front called the cornea that lets light in and refracts light towards the retina

What does the muscular iris control?

The size of the pupil and the amount of light entering the eye

What does the ciliary muscles and suspensory ligaments do?

Change the shape of the lens to fine focus light on to the retina

What does the optic nerve do?

Carries impulses from the retina to the brain

What is acommodation?

Acommodation is the process of changing the shape of the lens of the eye to focus on near or distant objects.

To focus on the distant objects, what does the eye do?

The ciliary muscles relax, the suspensory ligaments are pulled tight, and the lens is pulled thin so it only refracts light slightly.

To focus on the close objects, what does the eye do?

The ciliary muscles contract, the suspensory ligaments loosen and the lens becomes thicker so it refracts light strongly.

What is the difference between myopia and hyperopia?

myopia - short sightedness

hyperopia - long sightedness

How can sight defects be treated?

Using spectacle lenses(that refract light rays so they focus on the retina, hard and soft contact lenses, laser surgery and replacement lenses in the eye

What are rod and cone cells?

rod cells are a type of light receptors that are more sensitive to light intensity

cone cells are a type of light receptors that are useful for producing colour vision.

How are neurone cells adapted?

Axons are insulated by a fatty myelin sheath. Axons are normally long and thin, and they are used to carry messages all round the body

How does information travel through a synapse?

In the synapse, an electrical signal is converted into a chemical signal, which is then converted back to an electrical signal on the other side of the synapse

What is the peripheral nervous system?

The CNS is linked to sense organs by neurones, which form the peripheral nervous system

What is the response of the eye when its dim compared to when its bright?

When there’s dim light, more light is allowed to enter. The radial muscles contract so that the iris opens up, making the pupil larger, and allowing more light to enter.

When there’s bright light, less light is allowed to enter. The circular muscles contract in order to close up the iris, making the pupil smaller.