Coordination and control - The nervous system 2.0 Flashcards
what is a neurotransmitter?
Chemical involved in passing nerve impulses from one nerve cell to the next across a synapse
how do CT scanners remove the difficulties of accessing brain tissue inside the skull? (2)
-the ring takes a series of x-rays from different angles.
-these are processed by a computer to allow the doctors to see inside brains and other parts of the body.
what are PET scanners used for?
to detect high levels of metabolic reactions inside a person
how do PET scanners function? (3)
-PET scanners detect gamma rays that radiate from a chemical compound called a tracer.
-patient consumes the tracer which travels to any area of the body which has unusually high levels of metabolic reactions.
-this is often a tumour and so PET scans are used to detect cancers.
what is brain damage?
any loss of cells in the brain
what causes brain damage?
injuries when a person’s head hits an object with a great force.
which factors contribute to the extent of the injury? (4)
-the force of impact
-the size or shape of the object hitting the skull
-the position the object hits the skull
-the time it takes for treatment
why are brain injuries extremely difficult to treat and extremely dangerous? (2)
many are fatal
longer-term symptoms include speech or movement problems, reduced coordination, memory loss and personality changes.
why is treating brain damage very difficult? (2)
-all surgery carries a level of risk, but due to the complexity and delicacy of the brain, investigating and treating brain disorders can be very difficult
-more damage or side-effects may be created, which could affect the patients’ quality of life
what is the function of the cornea?
Refracts light - bends it as it enters the eye
what is the function of the Iris?
Controls how much light enters the pupil
what is the function of the lens?
Further refracts light to focus it onto the retina
what is the function of the retina?
Contains the light receptors
what is the function of the optic nerve?
Carries impulses between the eye and the brain
what is the function of the sclera?
Tough white outer layer of the eye - it helps protect the eye from injury
what are the 2 main types of light receptors?
rods and cones
what is the main difference between rods and cones?
what does this make them useful for?
Rods are more sensitive to light than cones so they are useful for seeing in dim light.
what do cone cells do?
produce colour vision.
when does the size of the pupil change?
-what is this controlled by?
in response to bright or dim light.
-the muscles of the iris.
describe the movement of the radial and circular muscles in dark and light conditions: (6)
dark:
-radial muscles of iris contract
-circular muscles of iris relax
-dilated pupil (more light enters eye)
light:
-radial muscles of iris relax
-circular muscles of iris contract
-dilated pupil (less light enters eye)
what is accommodation?
the process of changing the shape of the lens to focus on near or distant objects.
how does the lens change when you focus on near and distant object?
To focus on a near object - the lens becomes thicker which allows the light rays to refract (bend) more strongly.
To focus on a distant object - the lens is pulled thin which allows the light rays to refract slightly.
describe the
Ciliary muscles
Suspensory ligaments
Muscle tension on lens
Lens shape
Refraction of light rays
for NEAR objects:
Ciliary muscles: Contract
Suspensory ligaments: loosen
Muscle tension on lens: low
Lens shape: thicker
Refraction of light rays: Light is refracted strongly
describe the
Ciliary muscles
Suspensory ligaments
Muscle tension on lens
Lens shape
Refraction of light rays
for DISTANT objects:
Ciliary muscles: Relax
Suspensory ligaments: tighten
Muscle tension on lens: high
Lens shape: thin
Refraction of light rays: Light is only refracted slightly
what are the 2 common defects of the eye? and what can a person with them see?
-myopia (short-sightedness)
-can see near objects clearly, but cannot focus properly on distant objects
-hyperopia (long-sightedness)
-can see distant objects clearly, but they cannot focus properly on near objects
what happens in eye defects?
rays of light do not focus on the retina so a clear image is not formed.
how can eye defects be treated?
spectacle lenses, which refract (bend) the light rays so that they do focus on the retina.
what is short-sightedness caused by? (2)
-how can it be treated?
-the eyeball being elongated - so that the distance between the lens and the retina is too great.
-the lens being too thick and curved - so that light is focused in front of the retina.
-placing a concave lens in front of the eye
what is long-sightedness caused by? (2)
-how can it be treated?
-the eyeball being too short - so the distance between the lens and retina is too small
-a loss of elasticity in the lens - meaning it cannot become thick enough to focus (which is often age-related)
-putting a convex lens in front of the eye
what is an easy alternative to spectacle lenses? how do they work? (2)
hard and soft contact lenses
-float on surface of cornea and and focus & refract light
what are 2 other alternatives to spectacle lenses and how they work?
Laser surgery - reshapes the cornea surgically.
Replacement lens - implanting artificial lenses in front of the original lens
what is a cataract and how can it be treated?
-a cloudiness in the lens, caused by a build up of protein inside the lens.
-removing the lens and replacing with a plastic lens.
