Nervous System And Homeostasis Flashcards
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
What is the nervous system made up of?
The central nervous system (brain and spinal cord) and a network of nerves
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
What are reflex actions?
Reflex actions are automatic and rapid, they are not conscious movements
Help prevent damage to the body
What are neurones?
Carry electrical impulses around the body - relay neurones connect sensory neurones to motor neurones
What are synapses?
Gaps between neurones which allow electrical impulses in the nervous system to cross between neurones
What are the branched endings called?
Dendrites make connections with other neurones or effectors
What is the myelin sheath?
Insulates the axon, increasing the speed of electrical impulses
Where are axon terminals located?
On effectors, such as muscles or glands
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
What is the brain made from?
Billions of interconnected neurones, with different regions that carry out different functions
What is the cerebral cortex?
Outer layer of brain responsible for consciousness, intelligence, memory and language
What is the cerebellum?
At the back of the brain, coordinates muscle activity
What is the medulla oblongata?
Above the spinal cord, controls heart beat, breathing and other unconscious activities
How do neuroscientists study the brain?
MRI
Electrical stimulation of parts of the brain
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
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
