B10: The human nervous system Flashcards
What is homeostasis?
The regulation of the internal conditions of a cell/ organism to maintain optimum conditions for function in response to internal and external changes
What is an automatic control system?
A nervous responses from the nervous system or chemical responses from the endocrine system
What is the pathway of an automatic control system when it detects a change in the environment?
The change (stimulus) is picked up by the receptor cells, which pass it to a coordination centre (like the brain, spinal chord or pancreas), which processes and receives the information, before passing it to an effector (a muscle which contracts or a gland which secretes hormones) which carries out the response
Describe the pathway taken by electrical impulses when detecting a stimulus
Electrical impulse picked up by a receptor, then sent down a sensory neurone, to the CNS. At the end, there’s a junction called a synapse where a chemical is released and it diffuses across a relay neurone to the CNS where an electrical impulse is triggered in the motor neurone which passes down the impulse to the effector.
RP: Describe how to measure reaction time
One person holds a ruler above another person’s thumb (level with the 0 mark). They then drop the ruler, and the other person has to catch the ruler as quickly as they can. Then, record, the measurement that is level with the top of their thumb. Repeat several times and calculate a mean
RP: Independent, Dependent and Control variables
IV: The person whose reaction time is being tested
DV: The measurement of reaction time
CV: Starting distance between thumb and ruler, measure from top of thumb, conditions in the room (noise/ lighting)
RP: What other independent variables can be investigated in the experiment?
The effect of practise on reaction time
The hand catching the ruler
The effect on certain chemicals on reaction time
What are 3 parts of the brain and what are their functions?
Cerebral cortex - memory, language, consciousness
Cerebellum - movement coordination, balance
Medulla - body temp/ breathing rate maintainence
Why is it hard to treat brain damage/ diseases?
Brain surrounded by thick skull - hard to access
Complex structures - we don’t exactly know which parts perform which functions
Brain is delicate and easy to damage
How can we study the brain?
Look at patients with brain damage, look at their behaviour and narrow down that part of the brain to its function
Electrically stimulate different parts of the brain, and see changes in behaviour
MRI scans, look at which parts of the brain are most active during certain activities
How does the eye focus on near objects?
Ciliary muscle contracts, suspensory ligaments relax, lens is now more curved and thicker
What causes short sightedness?
Long eyeball, light focused in front of the retina
Lens is too thick
What is accommodation?
Changing the shape of the lens to focus on near or distant objects
How does the eye focus on distant objects?
Ciliary muscles relax, suspensory ligaments contract, lens is now thinner and less curved
What causes long sightedness?
Short eyeball, light focuses behind the retina
Less elastic lens, cannot bend to focus on near objects
How can hyperopia be treated?
Convex lens - focus the light before it enters the eye
How can myopia be treated?
Concave lens - partially un focus light before it enters the eye
Where is the retina found and what is its function?
Layer of light sensitive cells found at the back of the eye. When light hits it, it stimulates the cells, and sends an impulse to the brain, which interprets the information to form an image.
Where is the optic nerve found and what is its function?
Nerve that leaves the eye and goes to the brain. Carries impulses from the retina and to the brain.
Where is the sclera found and what is its function?
White outer layer which supports the structures inside the eye - strong to prevent damage.
Where is the cornea found and what is its function?
See through layer in front of the eye.
Allows light through and the curved surface bends the light so it focuses on the retina.
Where is the iris found and what is its function?
Muscles surrounding the pupil.
Contract and relax to change the size of the pupil.
What is the function of the ciliary muscles and suspensory ligaments?
Hold lens in place and control its shape.
What are some treatments for eye defects?
Spectacle lenses
Contact lenses
Laser eye surgery - either reduce the thickness of the cornea (myopia) or change its shape (hyperopia).
Replacement lens - risks include retinal damage or risks of cataracts.
