B5 The Nervous Sytem Flashcards
What does the central nervous system do?
Coordinates a response
What is the nervous system made up of?
Neutrons (nerve cells)
Where do neutrons go?
To all parts of the body
The body has lots of sensory receptors, what do they do?
Detect a change in your external or internal environment (a stimulus)
Give 2 examples of the stimuli that different sensory receptors detect
(Eyes, skin)
Receptors in eyes detect light
Receptors in skin detect touch (pressure) and temperature changes
What happens when a stimulus is detected by receptors?
The information is sent as nervous (electrical) impulses along sensory neurones to the central nervous system (CNS)
What does the CNS consist of?
The brain and the spinal cord
What does the CNS do?
It coordinates the response
Decides what to do about the stimulus and tells something to do it
Where does the CNS send information to?
An effector (muscle or gland) along a motor neurone.
What does the effector do?
It responds to the information from the CNS, eg. a muscle may contract or a gland may secrete a hormone.
Complete the sentence
Nervous communication is very ……, but the response are short lived
Fast
How do neurones transmit information?
Rapidly as electrical impulses
Where are electrical impulses passed along ?
The axon of a neurone
What are dendrites?
The branched endings of neurones.
Why do neurones have branched endings (dendrites)?
So the can connect with lots of other neurone.
What is myelin?
What does it do?
The fatty sheath that some axons are surrounded by.
It acts as an electrical insulator, speeding up the impulse.
Why are neurones long?
This speeds up the impulse as connecting with another neurone slows the impulse down.
One long neurone is much quicker than lots of short ones joined together.
What is the connection between two neurones called?
Synapse - it is a very tiny gap
What does the electrical impulse trigger the release of?
Transmitter chemicals
What do the transmitter chemicals do?
They diffuse across the synapse.
Bind to receptor molecules in the membrane of the next neurone, setting of a new electrical impulse.
Complete the sentence
Reflex actions are………..
Involuntary
Why are reflex actions involuntary?
They are done without thinking, so they’re even quicker than normal responses.
What is the passage of information for a reflex action called?
Reflex arc
Where does a reflex arc carry information from and to?
From receptor to effector
Complete the sentence
The conscious brain isn’t involved in a ……..
Reflex arc.
How does a reflex arc occur?
The sensory neurone connects to a relay neurone in the spinal cord or an unconscious part of the brain, which links directly to the right motor neurone.
Why isn’t the conscious brain involved in a reflex arc?
So no time is wasted thinking about the response.
What is the role of reflex actions?
Protective.
Eg. snatching back your hand when you touch a burning hot plate
List the stages of the response to a bee sting to the finger 5
Bee stings finger
Stimulation of the pain receptor
Impulse travels along the sensory neurone
Impulse is passed along a relay neurone
Impulse travels along a motor neurone
When impulse reaches muscle, it contracts to move arm away from the bee.
When might the conscious brain override a reflex response?
To stop us dropping a hit plate of food.
Name the two main parts of the central nervous system (2marks)
Brain
Spinal cord
