The Human Nervous System (AQA GCSE Biology)
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What is the role of the human nervous system?
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What is the role of the human nervous system?
The role of the nervous system is to allow humans to detect changes in their surroundings and coordinate responses.
What are receptor cells?
Receptor cells are cells that detect stimuli, e.g. cells in the eyes detect changes in light levels.
True or False?
Information passes along neurones in the form of electrical impulses.
True.
Information is passed along neurones and between the different parts of the nervous system in the form of electrical impulses.
Which two organs make up the central nervous system (CNS)?
The CNS is made up of the brain and the spinal cord.
What are effectors?
Effectors are the parts of the body that respond to changes in the environment. They can be muscles or glands.
Write a flow diagram to show the pathway of an electrical impulse through the nervous system.
The pathway of an impulse is as follows:
stimulus → receptor → sensory neurone → CNS → motor neurone → effector → response
What are reflex actions?
Reflex actions are automatic, rapid actions that do not involve conscious thought.
Why are reflex actions important?
Reflex actions are important because they protect the body from harm.
Write a flow diagram to represent a reflex arc.
A flow diagram that represents a reflex arc would be as follows:
stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response
True or False?
Sensory neurones in a reflex arc connect receptor cells with the conscious brain.
False.
Sensory neurones in a reflex arc connect receptor cells with relay neurones in the CNS.
While there are some reflex arcs that involve the brain, the brain regions involved are not connected with conscious thought.
What is a relay neurone?
A relay neurone is a neurone within the CNS that connects sensory and motor neurones.
True or False?
Synapses in reflex arcs are located between the end of a sensory neurone and the start of a relay neurone.
True.
Synapses are the junctions between neurones, such as that between the end of a sensory neurone and the start of a relay neurone.
What is the role of a motor neurone in a reflex arc?
Motor neurones in reflex arcs connect relay neurones with effectors.
Which factors could be chosen as independent variables when investigating the effect of a factor on reaction time?
Factors that could be chosen as independent variables when investigating the effect of a factor on reaction time include:
caffeine intake
environmental factors, e.g. background noise, room temperature
time since last meal
hours of sleep
How can a ruler be used to measure reaction time?
A ruler can be used to measure reaction time by dropping it vertically from a set height with 0 cm facing downwards and measuring the distance at which a volunteer catches it. The shorter the distance, the faster the reaction time.
In an investigation into the effects of caffeine on reaction time, which variables should be controlled?
Variables that should be controlled when investigating the effect of caffeine on reaction time include:
environmental factors, e.g. noise and temperature
the hand being used to catch the ruler, i.e. right vs left
the height from which the ruler is dropped
the time between caffeine consumption and the ruler drop test
When investigating the effect of a factor on reaction time, what is the benefit of repeating the measurement several times at each level of the independent variable?
The benefit of repeating the measurement several times at each level of the independent variable when performing the ruler drop test is that it allows anomalous results to be identified. These can then be left out when calculating the mean.
Which is the anomalous result in the table below?
The anomalous result in the table is attempt 3 for student C; this result should not be included when calculating the mean
What is the role of the brain in the nervous system?
The role of the brain is to control complex behaviour, as well as regulating body functions.
What are the brain structures labelled A-C on the diagram below?
Structures A-C can be identified as follows:
A = cerebral cortex
B = medulla
C = cerebellum
What is the role of the cerebral cortex in the brain?
The cerebral cortex is responsible for higher brain functions such as consciousness, intelligence, memory and language.
True or False?
The cerebellum in the brain is involved with the control of heart rate.
False.
The cerebellum in the brain is responsible for the coordination of movement.
Which body functions are regulated by the medulla in the brain?
The medulla in the brain regulates unconscious functions such as:
breathing
heart rate
digestion
Why is it difficult to study brain function and to treat damage in the brain? (Higher Tier Only)
It is difficult to study brain function and to treat damage in the brain because:
the brain is delicate
brain function is highly complex
the functions of different brain areas are interconnected so it is difficult to study regions in isolation
How can neuroscientists map brain function? (Higher Tier Only)
Brain function can be mapped by:
studying patients with damage to known areas of the brain
electrical stimulation of the brain and observation of response
MRI scanning
What are the structures labelled A-E on the diagram below?
The structures labelled A-E are:
A = ciliary muscles
B = suspensory ligaments
C = cornea
D = iris
E = retina
Where is the sclera of the eye?
The sclera of the eye is the white layer that forms the outside of the eyeball.
Define the term accommodation in the context of eye function.
Accommodation is the process by which the lens of the eye changes its shape to focus on objects at different distances.
What is the role of the ciliary muscle in accommodation?
The ciliary muscles contract or relax to change the shape of the lens during accommodation.
What happens to the ciliary muscles, suspensory ligaments and lens when focusing on a near object?
When focusing on a near object:
The ciliary muscles contract
The suspensory ligaments loosen
This causes the lens to become thicker (more curved), increasing refraction of light for close vision.
True or False?
When focusing on a distant object the ciliary muscles relax and the suspensory ligaments loosen.
False.
When focusing on a distant object:
The ciliary muscles relax
The suspensory ligaments tighten
This pulls on the lens, making it thinner; this reduces refraction of light for distant vision.
How does the eye adapt to deal with dim light?
The eye adapts to deal with dim light by dilating the pupil; this allows more light to enter the eye.
Define the terms myopia and hyperopia.
The terms can be defined as follows:
myopia = short sightedness
hyperopia = long sightedness
What causes short or long sightedness?
Short and long sightedness are caused by an inability to focus light onto the retina.
How can short and long sightedness be treated?
Short and long sightedness can be treated by:
wearing spectacles that refract light correctly
use of hard or soft contact lenses
laser surgery
replacing the lens of the eye
Which part of the brain monitors and controls body temperature?
The part of the brain that monitors and controls body temperature is the thermoregulatory centre.
What is the role of receptors in the control of body temperature?
Receptors are involved with temperature control as follows:
receptors in the thermoregulatory centre monitor blood temperature
receptors in the skin detect air temperature and send impulses to the thermoregulatory centre
How does sweating increase heat loss from the body?
Sweating increases heat loss when sweat evaporates from the skin surface. The evaporation of sweat transfers heat energy away from the skin.
Define the term vasodilation.
Vasodilation is a cooling mechanism in which the diameter of skin arterioles increases. This increases blood flow to capillaries in the skin surface, transferring heat to the environment by radiation.
How do blood vessels and sweat glands respond to an increased body temperature?
An increase in body temperature leads to the following changes:
Sweat glands release sweat which cools the skin by evaporation
Skin arterioles undergo vasodilation to increase blood flow to the capillaries at the surface of the skin
True or False?
When a person enters a colder environment blood flow to the surface of the skin is reduced.
True.
Vasoconstriction is a heat retention mechanism. The diameter of skin arterioles decreases to reduce blood flow to capillaries in the surface of the skin. This minimises heat loss by radiation.
How does shivering contribute towards temperature regulation?
Shivering occurs when body temperature is too low. The rapid muscle contractions generate heat, raising the core body temperature.
True or False?
Constriction of the capillaries reduces blood flow to the surface of the skin.
False.
Capillaries do not have a muscle layer and therefore cannot constrict. Constriction occurs in the arterioles that supply the skin capillaries, reducing blood flow to the skin surface.