Nervous System And Homeostasis Flashcards by Eloise Frewer

What is the function of the nervous system?

Allows humans to react to their surroundings and to coordinate behaviour through both voluntary and involuntary actions

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What is the nervous system made up of?

The central nervous system (brain and spinal cord) and a network of nerves

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What is a nervous system response?

A change in environment (stimulus) is detected by receptors
Information from receptors passes along neurones (cells) to the CNS as electrical impulses
The CNS coordinates the body’s response
Effectors bring about a response
The body responds to the stimulus

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What are reflex actions?

Reflex actions are automatic and rapid, they are not conscious movements
Help prevent damage to the body

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What are neurones?

Carry electrical impulses around the body - relay neurones connect sensory neurones to motor neurones

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What are synapses?

Gaps between neurones which allow electrical impulses in the nervous system to cross between neurones

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What are the branched endings called?

Dendrites make connections with other neurones or effectors

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What is the myelin sheath?

Insulates the axon, increasing the speed of electrical impulses

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Where are axon terminals located?

On effectors, such as muscles or glands

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How does a synapse work?

Impulse arrives in the neurone to sacs containing chemicals. Chemicals are released into the gap and attach to the surface of the next neurone to set up an electric impulse

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What is the brain made from?

Billions of interconnected neurones, with different regions that carry out different functions

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What is the cerebral cortex?

Outer layer of brain responsible for consciousness, intelligence, memory and language

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What is the cerebellum?

At the back of the brain, coordinates muscle activity

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What is the medulla oblongata?

Above the spinal cord, controls heart beat, breathing and other unconscious activities

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How do neuroscientists study the brain?

MRI
Electrical stimulation of parts of the brain

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Why is treatment of the brain difficult?

It is not fully understood what each part of the brain does
Drugs do not always reach the brain through its membranes
Surgery can easily cause damage

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What are two other important areas of the brain?

Hypothalamus, pituitary gland

What is the eye?

A sense organ containing receptors sensitive to light intensity and colour

What is the iris?

Coloured part of the eye that contains muscles which relax and contract, changing the size of the pupil in order to let more or less light in

What is the ciliary muscle?

Contracts and relaxes to change the shape of the lens

What is the retina?

Layer of receptors at the back of the eye containing light sensitive cells known as rods and cones

What is the sclera?

Tough white layer to protect eye

Where is the blind spot?

Where the optic nerve leaves the eye

What is the optic nerve?

Nerve that connects the eye to the brain

What is the suspensory ligament?

Tightens and slackens to change the shape of the lens

What is the lens?

Sits behind the pupil and focuses light on the retina

What is the cornea?

Transparent and curved to let light in and changes direction so that light is focused on the retina

What is accommodation?

Changing the shape of the lens to focus on near or distant objects

How do you focus on a near object?

Ciliary muscles contract Suspensory ligaments slacken Lens is thicker and more curved, refraction is stronger

How do you focus on a distant object?

Ciliary muscles relax Suspensory ligaments tighten Lens is thinner and flatter, only refracts light rays slightly

What is myopia?

Short sighted Distant objects look blurry Rays of light focus in front of the retina Correct using concave lens glasses

What is hyperopia?

Long sighted Near objects are blurry Light focuses behind retina Corrected using convex lens glasses

What is homeostasis?

Homeostasis is the regulation of internal conditions of a cell or whole organism in response to internal and external changes to constantly maintain optimum conditions for functioning. This maintains optimum conditions for all cell functions and enzyme action, which includes control of blood glucose concentration, body temperature and water levels.

What do all control systems involve?

Receptor cells, which detect stimuli Coordination centres which receive and process information from receptors Effectors, which produce responses to restore optimum conditions

How is body temperature controlled (too low)?

Thermoregulatory centre Body temp too low Vasoconstriction Sweating stops and skeletal muscles contract (shivering) Body temperature rises

How is body temperature controlled (too high)?

Thermoregulatory centr Body temperature too high Vasodilation Sweat produced from sweat glands Energy transferred from skin to environment and body temperature falls

How can eye defects be treated?

Spectacle lenses to refract light rays to focus on retina Hard and soft contact lenses act the same as spectacles Laser eye surgery to change the shape of the cornea Replacement lenses permanently corrects defects

What is the Thermoregulatory centre?

Monitors and controls body temperature Contains receptors sensitive to blood temperature Skin also contains temperature receptors Sends nerve impulses to the Thermoregulatory centre

What is laser eye surgery?

No need for glasses and contact lenses Quick recovery Improves vision Lasers reshape cornea of the eye so that you can focus better

What are the cells around the axon called?

Nodes of ranvier Schwann cells