Topic 5: The Nervous System Flashcards
What is the central nervous system? (CNS)
The brain and spinal cord.
what is the peripheral nervous system?
Nerve cells that carry information to or from the central nervous system.
What are sense organs?
A group of specialised cells called receptor cells, which can detect changes around them, either internally or externally.
What is a stimulus?
A change in environment that can be detected.
What are 5 examples of stimuli?
Light, sound, chemicals, touch and temperature.
Where does the information from sense organs travel to?
The brain and spinal cord (CNS) along nerve cells (neurones).
What are nerves formed by?
neurones which are grouped together.
What is an impulse?
The signal that travels along the neurones as an electrical current.
What are motor neurones?
Specialised neurones that pass through the central nervous system toward a muscle and conducts an impulse that causes movement.
What are sensory neurones?
Specialised neurons that send information from the sense organs to the CNS.
What is reaction time?
When a response happens, reaction time is the time taken between the stimulus and the response.
What is a synapse?
A tiny gap at the junction between two nerve cells, which nerve signals must cross.
What is a reflex?
A very rapid, automatic response.
What are 5 examples of reflexes?
Breathing, blinking, swallowing, sneezing and coughing.
What is a receptor?
An organ that detects the stimulus.
What does a coordinator do?
Detect the signal from a receptor and sends an impulse to the effector.
What is an effector?
Part of the body that produces the response.
usually a muscle
What is the response?
The action carried out.
What is a receptor cell?
A cell that can detect stimuli inside or outside the body.
What is a relay neurone?
A specialised neurone that carries nerve impulses within the central nervous system.
What are the 5 stages of a reflex?
- The stimulus is received by the receptor.
- An impulse is sent along the sensory neurone to the spinal cord.
- The impulse moves across a synapse to the relay neurone.
- The relay neurone transmits the signal to the motor neurone.
- The motor neurones stimulates the effector (the muscle) to respond.
Why are reflexes involentary?
Because reflexes don’t go through the brain, they go through the spinal cord.
What is a hormone?
A chemical messenger produced in glands and carried by the blood to specific organs in the body.
What is a reflex arc?
The nerve pathway followed by a reflex action.
What is a tropism?
A plant tropism is a growth in response to a stimulus.
What is a phototropism?
A growth in response to light.
What is a gravitropism?
Growth towards or away from the pull of gravity.
What is an example of a positive tropism?
Plant shoots grow towards the light.
What is an example of a negative tropism?
Roots grow away from light.
What is an example of a positive gravitropism?
Roots of plants.
What is an example of a negative gravitropism?
stems of plants.
What are tropisms controlled by?
Auxin (a type of hormone).
What is auxin?
A family of plant hormones.
Where are auxin mostly made?
In the tips of the growing stems and roots, which are the meristems.
What does auxin do?
They can diffuse to other parts of the stems or roots. Auxin change the rate of elongation in plant cells, controlling their length.
What is an eye?
A sense organ which detects light and sends information about the patterns of light it receives to the brain, which builds a picture from that information.
What is the sclera?
Tough white, outer layer which protects the retina.
What is the retina?
Light-sensitive inner layer that has cells that detect light, some detecting coloured light.
What is the optic nerve?
The cells send nerve impulses from the eye to the brain. Located at the back of the eye.
What is the blind spot?
The point where the optic nerve leaves the retina so lacks receptor cells.
What is the cornea?
Clear area of the sclera, it refracts light - bends it as it enters the eye.
What is the iris?
The muscles which alter the size of the pupil, controlling the amount of light entering the eye.
What is the lens’s function?
The lens focuses light onto the retina.
What is the choroid?
The pigmented middle layer with many blood vessels. It absorbs light to avoid reflection and nourishes the retina.
What is the pupil?
The small hole at the centre of the iris through which light enters the eye.
