B3.1 the nervous system Flashcards
What is the nervous system made up of?
Neurones (nerve cells), which go to all parts of the body.
What is a stimulus?
A stimulus is a change in the environment.
What detects a stimulus?
Sensory receptors
What receptor cells are found and what is their stimulus for the following sense organs:
a) eye
b) tongue
c) skin
d) nose
a) receptor cell-light; stimulus-light
b) receptor cell-taste; stimulus-chemical
c) receptor cells-pressure(touch), temperature; stimuli- pressure, heat
d) receptor cells-smell, taste; stimuli- chemical (for both)
Describe the stages in a nervous response.
The receptor cells detect the stimulus. When a stimulus is detected by receptors, the information is sent as nervous (electrical) impulses along sensory neurones to the central nervous system (CNS) which consists of the brain and the spinal chord. The CNS coordinates the response (so decides what to do about the stimulus and tells something to do it). The CNS send information to an effector (muscle or gland) along a motor neurone. The effector then respond accordingly - eg. a muscle May contract or a gland may secrete a hormone.
What are the three types of neurones?
Sensory neurones
Replay neurones
Motor neurones
Describe the role of sensory neurones
Its role is to carry electrical impulses from receptor cells to the CNS
Describe the role of the relay neurones.
They carry impulses from sensory neurones to motor neurones
Describe the role of motor neurones
They carry impulses from the CNS to effectors
What is the role of the axon?
Electrical impulses are passed along the axon of a neurone
Why do neurones have dendrites?
Neurones have branched endings (dendrites) so they can connect with lots of other neurones
What is the myelin sheath?
The myelin sheath acts a an electrical insulator, speeding up the electrical impulse.
As well as the myelin sheath how else do the neurones speed up the impulse?
Neurones are long, which also speeds up the impulse (connecting with other neurones slows the impulse down, so one long neurones is much quicker than lots of short ones joined together).
What is a synapse?
The connection between two neurones.
Explain what happens in the synapse.
The electrical impulse triggers the release of transmitter chemicals, which diffuse across the gap.
These chemicals bind to receptor molecules in the membrane on the next neurone. This sets off a new electrical impulse.
What are reflex reactions?
Reflex actions are automatic (involuntary) reactions as they occur without thinking. By missing out the brain, your body can react even faster.
They often have a protective role
Give basic example of reflex actions.
Breathing
Heart rate
Digestion
Describe the cornea and its function.
It is a transparent coating on the front of the eye.
Its function is to protect the eye by refracting light into the eye.
Describe the pupil and its function
It is a central hole in the iris
Its function is to allow light to enter the eye
Describe the iris and its function
It is a coloured ring of muscle tissue
Its function is to alter the pupil size by contracting or relaxing
Describe the lens and its function
It is a transparent biconvex lens
Its function is to focus light clearly onto the retina
Describe the ciliary body and its function
It is a ring of muscle tissue attached to suspensory ligaments
Its function is to alter the shape of the lens
Describe the sensory ligaments and its function
They are ligament tissue
They connect the ciliary muscle to the lens
Describe the optic nerve and its function
It is nervous tissue
It carries nerve impulses to the brain
What is the retina?
Retina is the light sensitive part and it’s covered in receptors called rods and cones, which detect light
What are rods and cones?
Rods are more sensitive in dim light and can’t sense colour. They allow you to see in low light levels.
Cones are sensitive to different colours but are not so good in dim lights.
How are images formed in the eye?
The cornea refracts incoming light rays. This provides most of the focus to the incoming light. The light then passes through the pupil and is further refracted by the lens. This creates a sharp image on the retina. Photoreceptors in the retina produce a nervous impulses when exposed to the light. This impulse travels down the optic nerve in the brain, which interprets the impulses as a visual image.
What happens to your eye when you focus on distance objects?
The ciliary muscle relaxes, which allows the suspensory ligaments to pull tight.
This pulls your lens so your lens become less conveys (thinner), so light is refracted less.
What happens to your eye when you focus on nearby objects?
The ciliary muscle contracts, which slackens the suspensory ligaments. The lens become more convey (fatter), so light is refracted more.
What is long-sightedness and what is it caused by?
Long-sighted people are unable to focus on nearby objects.
It is caused by a person’s lens being too weak, or by the eyeball being too short.
The lens too weak so the light rays are not refracted enough.
What is short-sightedness and what is it caused by?
Short-sighted people are unable to focus on distant objects.
It is caused by a person’s lens being too strong, or by the eyeball being too long.
The lens are too strong so the light is refracted too much so the lght Rays meet before they reach the retina.
What type of lens is used to correct short-sightedness?
Concave lens (they are in the shape of a time glass)
What type of lens is used to correct long-sightedness?
Convex lens (They are in a sort of oval shape)
What is red-green colour blindness caused by?
It’s caused when red or green cones in the retina are not working properly.
What are there five main areas of the brain?
medulla cerebellum hypothalamus pituitary gland cerebrum
What does the cerebrum do?
They control complex behaviour such as learning, memory, personality, language, intelligence and conscious thought.
It is the outer wrinkly bit
What does the cerebellum?
It controls posture, balance, and involuntary movement like muscle coordination.
What does the medulla do?
It controls unconscious activity such as heart rate and breathing rate
What does the hypothalamus do?
The hypothalamus regulates temperature and water balance.
It also produces hormones that control the pituitary gland.
What does the pituitary gland do?
It stores and releases hormones that regulate many body functions
How can electrodes be used to study brain function?
The electrodes transmit electrical impulses, which result in movement in different parts of the animal’s body. This enables scientists to link an area of the brain to the region of the body it controls.
How can Computed tomography (CT) be used to study brain function?
CT scans used x-Ray’s to create 3D images of the inside of the body. The position of any abnormalities can be linked to changes in a patient’s behaviour.
What is the disadvantage of using CT scans to study brain function?
CT scans cannot be sued regularly, as x-Ray radiation increases the risk of cancer.
How can magnetic resonance imaging (MRI) be used to study brain function?
MRI scans use powerful magnets to identify brain abnormalities
Explain functional magnetic resonance imaging (fMRI).
fMRI scans produce images in real time so scientists can identify areas of the brain that show increased blood flow.
What are the problems with studying brain functionality?
If a person is severely brain damaged, it may be unethical to study them as they might not be able to give informed consent.
Studying the brains of people who have died relied on people donating their brains for research.
There can be problems when interpreting the results of case studies. For example, it cannot be known for sure that the same pattern of activity would occur in a normal situation (i.e when not in a machine)
Define CNS
CNS stands for central nervous system
This consists of your brain and spinal chord
Define PNS
PNS stands for peripheral nervous system
This consists of all the neurones that connect the CNS to the rest of the body. These are the sensory neurones, which carry nerve impulses from the receptors to the CNS, and the motor neurones, which carry nerve impulses away from the CNS to the effectors.
What can damage to the PNS result in?
an inability to detect pain
numbness
loss of coordination
What is the ability of the PNS to regenerate?
The PNS has a limited ability to regenerate
What can damage to the CNS lead to?
a loss of control of body systems
partial or complete paralysis
memory loss or processing difficulties
Why can damage to the CNS lead to permanent damage?
This is because the CNS cannot regenerate so any damage is permanent unless it can be corrected by surgery
How many nerves are in the spinal cord?
31 pairs of nerves
What treatment is used to treat brain tumour?
Radiotherapy and chemotherapy is used to treat a brain tumour
What treatment is used to remove brain tissue?
Surgery
How to scientists insert an electrode to stimulate brain function?
deep brain stimulation
