5 1 the human nervous system

The role of the nervous system is to allow humans to detect changes in their surroundings and coordinate responses.

Receptor cells are cells that detect stimuli, e.g. cells in the eyes detect changes in light levels.

True. Information is passed along neurones and between the different parts of the nervous system in the form of electrical impulses.

The CNS is made up of the brain and the spinal cord.

Effectors are the parts of the body that respond to changes in the environment. They can be muscles or glands.

The pathway of an impulse is as follows: stimulus → receptor → sensory neurone → CNS → motor neurone → effector → response

Reflex actions are automatic, rapid actions that do not involve conscious thought.

Reflex actions are important because they protect the body from harm.

A flow diagram that represents a reflex arc would be as follows: stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response

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.

A relay neurone is a neurone within the CNS that connects sensory and motor neurones.

True. Synapses are the junctions between neurones, such as that between the end of a sensory neurone and the start of a relay neurone.

Motor neurones in reflex arcs connect relay neurones with effectors.

Factors that could be chosen as independent variables when investigating the effect of a factor on reaction time include:

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.

Variables that should be controlled when investigating the effect of caffeine on reaction time include:

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.

The anomalous result in the table is attempt 3 for student C; this result should not be included when calculating the mean

The role of the brain is to control complex behaviour, as well as regulating body functions.

Structures A-C can be identified as follows:

The cerebral cortex is responsible for higher brain functions such as consciousness, intelligence, memory and language.

False. The cerebellum in the brain is responsible for the coordination of movement.

The medulla in the brain regulates unconscious functions such as:

It is difficult to study brain function and to treat damage in the brain because:

Brain function can be mapped by:

The structures labelled A-E are:

The sclera of the eye is the white layer that forms the outside of the eyeball.

Accommodation is the process by which the lens of the eye changes its shape to focus on objects at different distances.

The ciliary muscles contract or relax to change the shape of the lens during accommodation.

When focusing on a near object: This causes the lens to become thicker (more curved), increasing refraction of light for close vision.

False. When focusing on a distant object: This pulls on the lens, making it thinner; this reduces refraction of light for distant vision.

The eye adapts to deal with dim light by dilating the pupil; this allows more light to enter the eye.

The terms can be defined as follows:

Short and long sightedness are caused by an inability to focus light onto the retina.

Short and long sightedness can be treated by:

The part of the brain that monitors and controls body temperature is the thermoregulatory centre.

Receptors are involved with temperature control as follows:

Sweating increases heat loss when sweat evaporates from the skin surface. The evaporation of sweat transfers heat energy away from the skin.

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.

An increase in body temperature leads to the following changes:

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.

Shivering occurs when body temperature is too low. The rapid muscle contractions generate heat, raising the core body temperature.

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.