Topic 5- Human nervous system

Question 1

What is the function of the nervous system?

Answer 1

The nervous system allows the body to react to its surroundings and coordinate an appropriate response

Question 2

How des a stimulus lead to a response being carried out by the body?

Answer 2

-Stimulus is converted into an electrical impulse by the receptors
-The electrical impulse passes along sensory neuron’s to the the central nervous system (CNS)
-The CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector, which carries out the response

Question 3

What sequence of events describes how the nervous system works?

Answer 3

Stimulus–> receptor–> coordinator–> effector–> response

Question 4

What is reflex action?

Answer 4

A reflex action is an automatic and rapid response which does not involve any conscious input from the brain

Question 5

Why are reflex actions important?

Answer 5

Reflex actions aid survival by preventing harm to the body

Question 6

Describe how a reflex action occurs via a reflex arc

Answer 6

-The stimulus is detected by a receptor
-An electrical impulse passes along a sensory neurone to the spinal cord (part of the CNS)
- At a synapse between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone
-The same process occurs at a synapse between a relay neurone and a motor neurone
-At the effector, an appropriate response is carried out

Question 7

What is the difference between a reflex pathway and a conscious pathway?

Answer 7

Within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord/unconscious parts of the brain. In a conscious pathway, the coordination centre is in the conscious part of the brain

Question 8

What is the function of the cerebral cortex?

Answer 8

Controls consciousness, intelligence, memory and language

Question 9

What is the function of the cerebellum?

Answer 9

Controls muscular coordination

Question 10

What is the function of the medulla

Answer 10

Controls unconscious activities (eg breathing, heart rate etc)

Question 11

Why is the investigation and treatment of the brain difficult

Answer 11

-Its a complex and delicate organ
-The brain is easily damaged and destroyed
-Certain membranes prevent drugs from reaching the brain
- The exact function of each part of the brain is not known

Question 12

What methods are used by scientists to determine brain function?

Answer 12

-Studying patients with brain damage
-Electrical stimulation of the brain
-MRI scans

Question 13

What stimuli are the receptors of the eye sensitive to

Answer 13

Light intensity and colour

Question 14

What are the two main functions of structures found within the eye?

Answer 14

Focusing on near or distant objects- accommodation
Adaptation to dim light

Question 15

Describe the structure and function of the retina

Answer 15

The retina is a light-sensitive layer found at the back of the eye
Light stimulates the retinal cells, resulting in impulses being sent to the brain

Question 16

Describe the structure an function of the the optic nerve

Answer 16

The optic nerve connects the eye and the brain
It carries impulses to the brain so that image can be visualised

Question 17

Describe the structure and function of the sclera

Answer 17

The sclera is the though outer layer of the eye which protects its internal structures

Question 18

Describe the structure and function of the cornea

Answer 18

The cornea is the curved transparent layer at the front of the eye
It lets light into the eye and allows light to be focused onto the retina

Question 19

Describe the structure and function of the iris

Answer 19

The iris is a muscle which controls the size of the pupil by contracting or relaxing. This allows the eye to adjust to bright and dim lighting

Question 20

Describe the structure and function of the ciliary muscles and suspensory ligaments

Answer 20

The ciliary muscles and suspensory ligaments hold the lens in place and control its shape

Question 21

Describe how the iris alters the size of the pupil in both bright and dim light

Answer 21

Bright light: Circular muscles contracts and radial muscles relax- makes pupil smaller to avoid retinal damage
Dim light: circular muscles relax and radial muscles contract- makes pupil larger so more light can enter the eye

Question 22

What is accommodation?

Answer 22

Altering the lens’ shape in order to focus on near or distant objects

Question 23

How does the eye focus on a nearby object?

Answer 23

-Ciliary muscles contract
-Suspensory ligaments loosen
-Lens becomes thicker and more curved- light rays are refracted strongly

Question 24

How does the eye focus on a far away object?

Answer 24

Ciliary muscles relax
Suspensory ligaments tighten
Lens becomes thinner- light rays are refracted weakly

Question 25

What is myopia

Answer 25

Myopia (short-sightedness) usually occurs Shen the lens of the eye is too curved. As a result, light focused in front of the retina so images appear blurry

Question 26

How can myopia treated

Answer 26

Myopia can be treated using glasses with a concave lens, which spreads out light rays so they can be focused on the retina

Question 27

What is hyperopia

Answer 27

Hyperopia (long-sightedness) usually occurs when the lens of they is too flat. As a result, light is focused behind the retina so images appear out focus

Question 28

How can hyperopia be treated

Answer 28

Hyperopia can be treated using glasses with a convex lens, which brings the light rays together so they can be focused on the retina

Question 29

What are the two types of contact lenses?

Answer 29

Contact lenses are lenses that are placed on the eye. There are two types: Hard- rigid material, last a long time, must be kept sterile Soft- flexible material, last for a shorter time, more comfortable

Question 30

What is laser eye surgery?

Answer 30

Laser eye surgery is the use of lasers to fix visual defects in adults. To treat myopia, lasers reduce the thickness of the cornea so light is refracted less strongly. To treat hyperopia, lasers alter the curvature of the cornea so that light is refracted correctly

Question 31

How can replacement lenses be used to treat visual defects?

Answer 31

A replacement lens can either implanted into the eye (along with natural lens) or it may replace the natural lens altogether. Risks of lens replacement include renal damage, cataracts, and infections

Question 32

What are the risks of lens replacement

Answer 32

Risks of lens replacement include renal damage, cataracts, and infections

Question 33

Where is body temperature controlled in the body

Answer 33

Body temperature is controlled by the thermoregulatory centre in the hypothalamus of the brain

Question 34

How is temperature monitored by the body

Answer 34

-Thermoregulatory centre has receptors sensitive to blood temperature -Skin has receptors sensitive to skin temperature - sends impulses to thermoregulatory centre

Question 35

What physiological changes occur when body temperature is too high

Answer 35

Vasodilation- blood vessels near the surface of the skin dilate- more heat is radiated away Sweating- evaporation of water takes away heat energy from the surface of the skin

Question 36

What physiological changes occur when the body temperature is too low

Answer 36

Vasoconstriction- blood vessels near the surface of the skin constrict- less heat radiated Shivering- respiration allows muscles to contract. It is an exothermic process, so heat energy is released Sweating stops