B3.1 Nervous System Flashcards
What is the function of your nervous system?
To detect a change in the external environment and to cause a response
What are the 3 main stages to a nervous response?
There is a change in the environment eg light or heat (stimulus)
Receptors detect the stimulus
Effectors such as muscles or glands cause a response
What do receptor cells do and where are they found?
They are found in your sense organs such as eye, tongue, skin and nose and they detect stimuli. They then change the stimuli into electrical impulses
What is the CNS?
Central nervous system
Made of the brain and spinal cord and are protected by the skull and bones
What are sensory neurones?
The neurone that carries electrical impulses from receptor cells to the CNS
What are relay neurones?
Found in the CNS and carry impulses from sensory to motor neurones
What are motor neurones?
Neurones that carry impulses away from the CNS to effectors
What is the structure of a sensory neurone?
Nucleus in the middle surrounded by cell body, myelin sheet for insulation, axon and dendrons on in the center
What is the structure of a relay neurone?
The round one
Nucleus in the centre surrounded by cell body then dendrons then dendrites
Direction of impulse from outside to inside
Structure of motor neurones
Nucleus on the end surrounded by cell body and dendrites
Direction of impulse from left(nucleus side) to right
What are nerves?
Bundles of many neurones
Flow diagram of a nervous reactions and how long it takes
Stimulus - receptor cells - sensory neurone - spinal cord - brain - spinal cord - motor neurone - effector - response
0.7 seconds
What is a coordinated response?
Responses sent to different parts of your body to produce different responses
What is a reflex action?
Involuntary reaction s which occur without thinking, probably when you are in danger. Only takes 0.2 seconds as the brain is missed out
Name some normal reflex actions
Breathing, heart rate, digestion
Write the reflex arc
Stimulus - receptor cells - sensory neurones - spinal cord - motor neurones - effectors - response
How are images formed in the eye?
The cornea refracts light
Light passes through the pupil and is refracted by the lens onto the retina
Photoreceptors which detect light produce a nervous impulse when exposed to light
The impulse travels down the optic nerve to the brain
What happens when you focus on near objects?
The ciliary muscle contracts so the lense becomes convex(fatter)
What happens when you focus on far objects?
Ciliary muscles relax, lens becomes concave(thin)
What is short sightedness? What is it caused by? What is it corrected by?
When far objects are blurry
Caused by lens being too strong or eyeball being to long so the light rays meet before the retina is reached
Concave lens to bend light outwards
What is long sightedness? What is it caused by? How is it corrected?
When close objects are blurry
Caused by lens being too weak or eyeball being too short so light rays go past the retina and don’t focus on it
Corrected by convex lens which bends light inwards
What are the 2 types of photoreceptor cells and what do they detect?
Rods - light
Cones - colour(red,blue,green)
What is colour blindness?
People who cannot see some colours. Most common form is red green colour blindness where people cannot see the different between red and green
What is the function of the brain?
To process all the information collected by receptor cells about changes in internal or external environments to produce a coordinated response. It is a central control centre
What does the cerebrum do?
Control complex behaviour, memory, personality, thought
What does the cerebellum do?
Controls balance, posture, involuntary movements
What does the medulla do?
Automatic actions like breathing
What does the hypothalamus do?
Regulates temperature and water balance
What does the pituitary gland do?
Releases hormones
How is the brain investigated?
Case studies can be used. If a part of the brain has been damaged the effect in the patient can tell you about the function of the damaged part
Placing electrodes in brains which transmit electrical impulses which result in movements of the body which helps us link parts of the brain to the body
CT Scans
MRI scans
What are CT scans?
CT(Computed tomography) scans - use xrays to create 3d images so that abnormalities can be detected. However it can’t be used regularly as high dosages of xrays increase risk of cancer
What are MRI scans?
Magnetic resonance imaging uses powerful magnets to identify brain abnormalities.
fMRI produces live images and shows areas of increased blood flow which are active when a specific activity is being done
What is the PNS?
Peripheral nervous system - all the neurones that connect the CNS to the body
What can damage to the PNS or CNS occur from?
Injuries, disease, genetic conditions, toxic substances(eg lead)
What does damage to the nervous system mean?
Impulse cannot be passed effectively
Effects of PNS nervous system damage?
Inability to detect pain and numbness
Loss of coordination
Has limited ability to regenerate so severe damage needs surgery
Effects of damage to CNS?
Loss of control of body systems
Partial or full Paralysis
Memory loss
CNS cannot regenerate so damage is permanent unless surgery
Why is is difficult to repair the CNS?
Identifying individual nerve fibres in the spinal cord without damaging others is extremely difficult
Damage to brain is difficult to diagnose
Treatments to CNS damage
Radio/chemo therapy for brain tumours
Surgery to remove tissue
Deep brain stimulation where an electrode stimulates brain function
