The Human Nervous System Flashcards
All 45 cards in this deck
What are the two parts of the central nervous system (CNS)?
The brain and the spinal cord.
In what form does information travel along neurones?
As electrical impulses.
What is an effector?
A muscle that contracts or a gland that secretes hormones, producing the response.
What is the role of the CNS in coordination?
It receives impulses from receptors and coordinates the response of effectors.
What are the five parts of a nervous pathway, in order?
e.g. touching a hot pan
Stimulus → receptor → coordinator (CNS) → effector → response.
e.g. heat → temperature receptor in skin → spinal cord → arm muscle → hand pulls away.
True or false? Receptors and effectors are the same type of structure.
False. Receptors detect stimuli; effectors (muscles or glands) carry out the response.
In a reflex arc, what is the order of the three neurones involved?
Sensory neurone → relay neurone → motor neurone.
What is a synapse?
The junction (gap) between two neurones.
How is information passed across a synapse?
A chemical is released, diffuses across the gap and sets off a new electrical impulse in the next neurone.
What is meant by a 'reflex action'?
A response to a stimulus that is automatic/involuntary, with no conscious thought.
Why are reflex actions important?
They are rapid and automatic, protecting the body from danger or damage.
True or false? Reflex actions involve the conscious part of the brain.
False. The impulse does not pass through the conscious part of the brain, which is why reflexes are faster.
What are the steps of an impulse passing through a reflex arc?
e.g. touching a sharp pin
- Receptor detects stimulus, impulse passes along sensory neurone to CNS (pain receptor in finger).
- Impulse crosses a synapse to a relay neurone in the spinal cord.
- Impulse crosses another synapse to the motor neurone, which carries it to the effector (arm muscle contracts, hand pulls away).
In the ruler drop test for reaction time, what is the dependent variable?
The distance the ruler falls before it is caught (converted to reaction time).
Give three control variables for a ruler drop reaction time investigation.
Same starting position of the ruler (0 cm at the hand), same hand used, same person dropping/catching, arm rested on the table.
Name two ways of improving the ruler drop method for measuring reaction time.
Repeat and calculate a mean (ignoring anomalies), and use the same starting position of the ruler each time.
True or false? A shorter ruler-drop catch distance means a faster reaction time.
True. The ruler falls less far in a shorter time, so a smaller distance means a quicker reaction.
Name two factors a student could investigate for their effect on human reaction time.
Caffeine (drink) and background noise/distraction; also practice or time of day.
What is the function of the cerebral cortex?
It is responsible for consciousness, intelligence, memory and language (conscious decisions).
What is the function of the cerebellum?
It controls balance, posture and coordination of muscular activity.
What is the function of the medulla?
It controls unconscious activities such as heart rate and breathing rate.
Where is the cerebral cortex found in the brain?
The outer, highly folded layer covering the top of the brain (the cerebral hemispheres).
Name three methods neuroscientists use to map regions of the brain to functions.
Studying patients with brain damage, electrically stimulating parts of the brain, and MRI scanning.
Why is treating brain damage and disease very difficult?
The brain is extremely complex and delicate, and is hard to access inside the skull, so treatment risks further damage.
True or false? The brain is made of billions of interconnected neurones.
True. Different regions of the brain carry out different functions.
What is the function of the retina?
It contains the light receptors, which are sensitive to light intensity and colour.
What is the function of the cornea?
A transparent front layer that refracts light into the eye.
What is the function of the iris?
It contains muscles that change the size of the pupil, controlling how much light enters the eye.
What is the function of the optic nerve and the sclera?
The optic nerve carries impulses from the retina to the brain; the sclera is the tough white outer layer that protects the eye.
What is accommodation?
The process of changing the shape of the lens to focus on near or distant objects.
What happens in the eye when focusing on a near object?
Ciliary muscles contract, suspensory ligaments loosen, lens becomes thicker and refracts light rays strongly.
What happens in the eye when focusing on a distant object?
Ciliary muscles relax, suspensory ligaments are pulled tight, lens is pulled thin and only slightly refracts light rays.
How does the eye adapt to dim light?
Muscles in the iris relax/adjust so the pupil dilates (gets bigger), letting more light reach the retina.
In myopia and hyperopia, where do light rays focus, and which lens corrects each?
Myopia: rays focus in front of the retina, corrected by a concave lens. Hyperopia: rays focus behind the retina, corrected by a convex lens.
Other than spectacles, name three technologies used to correct eye defects.
Hard or soft contact lenses, laser surgery to change the shape of the cornea, and a replacement lens in the eye.
True or false? The ciliary muscles contract to make the pupil smaller in bright light.
False. The muscles of the iris change pupil size; the ciliary muscles change the shape of the lens.
Which part of the brain monitors and controls body temperature?
The thermoregulatory centre.
What does the thermoregulatory centre contain, and what does it monitor?
Receptors sensitive to the temperature of the blood flowing through the brain.
How does the skin send information about temperature to the thermoregulatory centre?
Temperature receptors in the skin send nervous impulses along neurones to the thermoregulatory centre.
What three responses happen if body temperature is too low?
Blood vessels constrict (vasoconstriction), sweating stops, and skeletal muscles contract (shivering).
What two responses happen if body temperature is too high?
Blood vessels dilate (vasodilation) and sweat is produced from the sweat glands.
How does vasodilation help lower body temperature?
More blood flows near the skin surface, so more energy is transferred from the blood to the environment.
How does shivering raise body temperature?
Skeletal muscles contract, increasing respiration, which releases energy that warms the body.
True or false? During vasodilation the blood vessels move closer to the surface of the skin.
False. The vessels do not move; they widen so more blood flows near the surface.
True or false? Sweating cools the body because energy is transferred from the skin as the sweat evaporates.
True. Evaporation of the sweat transfers energy from the skin to the environment, so less sweat means less cooling.