Coordination and control - The nervous system 2.0

Question 1

what is a neurotransmitter?

Answer 1

Chemical involved in passing nerve impulses from one nerve cell to the next across a synapse

Question 2

how do CT scanners remove the difficulties of accessing brain tissue inside the skull? (2)

Answer 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.

Question 3

what are PET scanners used for?

Answer 3

to detect high levels of metabolic reactions inside a person

Question 4

how do PET scanners function? (3)

Answer 4

-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.

Question 5

what is brain damage?

Answer 5

any loss of cells in the brain

Question 6

what causes brain damage?

Answer 6

injuries when a person’s head hits an object with a great force.

Question 7

which factors contribute to the extent of the injury? (4)

Answer 7

-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

Question 8

why are brain injuries extremely difficult to treat and extremely dangerous? (2)

Answer 8

many are fatal

longer-term symptoms include speech or movement problems, reduced coordination, memory loss and personality changes.

Question 9

why is treating brain damage very difficult? (2)

Answer 9

-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

Question 10

what is the function of the cornea?

Answer 10

Refracts light - bends it as it enters the eye

Question 11

what is the function of the Iris?

Answer 11

Controls how much light enters the pupil

Question 12

what is the function of the lens?

Answer 12

Further refracts light to focus it onto the retina

Question 13

what is the function of the retina?

Answer 13

Contains the light receptors

Question 14

what is the function of the optic nerve?

Answer 14

Carries impulses between the eye and the brain

Question 15

what is the function of the sclera?

Answer 15

Tough white outer layer of the eye - it helps protect the eye from injury

Question 16

what are the 2 main types of light receptors?

Answer 16

rods and cones

Question 17

what is the main difference between rods and cones?
what does this make them useful for?

Answer 17

Rods are more sensitive to light than cones so they are useful for seeing in dim light.

Question 18

what do cone cells do?

Answer 18

produce colour vision.

Question 19

when does the size of the pupil change?
-what is this controlled by?

Answer 19

in response to bright or dim light.
-the muscles of the iris.

Question 20

describe the movement of the radial and circular muscles in dark and light conditions: (6)

Answer 20

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)

Question 21

what is accommodation?

Answer 21

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

Question 22

how does the lens change when you focus on near and distant object?

Answer 22

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.

Question 23

describe the

Ciliary muscles
Suspensory ligaments
Muscle tension on lens
Lens shape
Refraction of light rays

for NEAR objects:

Answer 23

Ciliary muscles: Contract
Suspensory ligaments: loosen
Muscle tension on lens: low
Lens shape: thicker
Refraction of light rays: Light is refracted strongly

Question 24

describe the

Ciliary muscles
Suspensory ligaments
Muscle tension on lens
Lens shape
Refraction of light rays

for DISTANT objects:

Answer 24

Ciliary muscles: Relax
Suspensory ligaments: tighten
Muscle tension on lens: high
Lens shape: thin
Refraction of light rays: Light is only refracted slightly

Question 25

what are the 2 common defects of the eye? and what can a person with them see?

Answer 25

-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

Question 26

what happens in eye defects?

Answer 26

rays of light do not focus on the retina so a clear image is not formed.

Question 27

how can eye defects be treated?

Answer 27

spectacle lenses, which refract (bend) the light rays so that they do focus on the retina.

Question 28

what is short-sightedness caused by? (2)

-how can it be treated?

Answer 28

-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

Question 29

what is long-sightedness caused by? (2)

-how can it be treated?

Answer 29

-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

Question 30

what is an easy alternative to spectacle lenses? how do they work? (2)

Answer 30

hard and soft contact lenses
-float on surface of cornea and and focus & refract light

Question 31

what are 2 other alternatives to spectacle lenses and how they work?

Answer 31

Laser surgery - reshapes the cornea surgically.

Replacement lens - implanting artificial lenses in front of the original lens

Question 32

what is a cataract and how can it be treated?

Answer 32

-a cloudiness in the lens, caused by a build up of protein inside the lens.
-removing the lens and replacing with a plastic lens.