Human Nervous System Flashcards
What is a stimulus ?
A change in environment
What is a receptor ?
A cell that detects change
What is the coordination centre ?
Consists of brain + spinal cord
Receives and processes information from receptors around the body
What is the peripheral nervous system ?
Consists of motor and sensory neurones that carry information from receptors to CNS and instructions from CNS to effectors
What is an effector ?
A muscle that contracts, or a gland that releases or secretes hormones and chemicals. Brings about a response.
Stimulus and receptor for sight
Light
Photoreceptors
Stimulus and receptor for hearing
Sound / vibrations
Auditory receptors
Stimulus and receptor for smell
Odour / chemicals in air
Olfactory receptors
Chemoreceptors
Stimulus and receptor for taste
Chemicals
Chemoreceptors
Stimulus and receptor for touch
Mechanical forces
Mechanoreceptors
Receptor for temperature
Thermoreceptors
Receptor for blood pressure
Baroreceptors
Receptor for body positioning
Proprioceptors
What are sensory neurones ?
The electrical impulse moves along it in the direction away from the receptor.
They run along the axon, which is coated in a myelin sheath.
What is a myelin sheath ?
Made up of protein + fatty substances.
Many Schwann cells make up a myelin sheath.
What is a motor neurone ?
The impulse moves along it towards the effector.
The cell body appears at the end furthest from the effector and is surrounded by dendrites.
The impulse runs along the axon which is coated in a myelin sheath.
Adaptations of neurones
Have a long fibre ( axon ) so they can carry messages over long distances.
Axon is insulated by myelin sheath that increases speed of nerve impulses.
Dendrites receive incoming nerve impulses from other neurones.
What is multiple sclerosis ?
Breaks down the myelin sheath around the axon and exposes nerve fibre.
Therefore, MS sufferers have slower reactions to stimuli activating their receptors and sensory neurone.
This decrease in speed can lead to sufferers experiencing numbness in extremities.
What is a reflex action ?
An automatic and rapid response to a stimulus, which minimises any damage to the body from potentially harmful conditions.
What is the general sequence of the reflex arc ?
Stimulus
Receptor
Sensory neurone
Relay neurone - in CNS
Motor neurone
Effector
Response
What happens at a synapse ?
An electrical impulse travels along the first axon to the axon terminal.
This triggers the axon terminal to release chemical messengers called neurotransmitters.
These chemicals diffuse across the synapse and bind with receptor molecules on the membrane of the second neurone.
This stimulates the dendrite of the second neurone to transmit the electrical impulse, which then travels down the neurone.
What is a reaction time ?
The time it takes your body to react to a stimulus.
Factors that affect reaction time
Drugs
Tiredness
Age
Physical fitness
Mental fitness
Distractions
What are method limitations ?
Any flaw or fault in the method or design that affects the accuracy of the result
What is accuracy ?
How close a reading / measurement is to its true value
What is precision ?
How similar repeat readings / measurements are to each other
What is Reliability ?
Experiments are repeated many times to ensure the reliability of a method
What is validity ?
The other variables in the experiment are identified and controlled in order to ensure the validity of an experiment
Ruler Drop Test method
Work with a partner.
Person A holds out their hand with a gap between their thumb and first finger.
Person B holds the ruler with the zero at the top of person A’s thumb
Person B drops the ruler without telling Person A and they must catch it.
The number level with the top of person A’s thumb is recorded in a suitable table. Repeat this ten times.
Swap places, and record another ten attempts.
What is the cerebrum ?
Largest part of the brain
Outermost 2mm is known as the cerebral cortex. It is highly folded and contains most of the neurones that help to carry out the cerebral functions:
Conciousness
Intelligence
Memory
Language
Emotional responses
What is the cerebellum ?
The 2nd largest part of the brain
Does not initiate movement, but contributes to coordination, precision and accurate timing.
Receives input from sensory systems of the spinal cord and other parts of the brain, and integrates these inputs to fine-tune movements.
What is the medulla oblongata ?
Part of the brain stem
Involved with unconscious activities eg. controlling heartbeat, gut, breathing, vomiting and blood pressure
What is the hypothalamus ?
Small area that has many functions, including linking nervous system to hormonal system via pituitary gland.
Contains main different receptors that coordinates responses.
Involved with instinctive behaviours.
What is the pituitary gland ?
Releases hormones that causes other glands to release hormones that bring about a response.
Linked to hypothalamus, which releases hormones to make the pituitary gland release hormones.
Neurology
A branch of medicine that deals with disorders in the nervous system ( CNS and PNS )
What is an MRI ?
Magnetic Resonance Imagery
Uses strong magnetic fields and radio waves to produce image of the nervous system or other parts of the body.
Patients are asked to perform various tasks and, by looking at the scan, scientists can see which parts of the brain are active when the task is carried out.
Pros of MRI
Non invasive
No ionising radiation
Safer than alternatives
Cons of MRI
Expensive
Enclosed space
Cannot distinguish between benign and malignant tumours
What is a CT ?
Computer Tomography Scan
Uses X-rays to diagnose conditions ( bone damage, internal organ injuries, problems with blood flow ) and guide further tests or treatments ( detects location and size of tumours ).
Risks of CT scan
Ionising radiation
Injection of dye ( radioactive or heavy metal )
Expensive
What is EEG ?
Electroencephalography
Works by attaching small sensors all over scale to detect electrical signals produced when brain cells send messages to each other. Highly trained specialists can read these changes to detect unusual activity.
Pros of EEG
Can detect epilepsy, fits and memory problems
Safe, non-invasive
Cheaper than alternatives
No radiation involves
Cons of EEG
Can’t detect cancer or disease that doesn’t affect electrical systems.
Time consuming
What is the retina ?
Made up of light sensitive receptor cells
What is the optic nerve ?
Carries impulses from the retina to the brain
What is the sclera ?
Tough outer layer
What is the cornea ?
Transparent region of the sclera at the front of the eye. Refracts light, which bends as it enters the eye.
What is the iris ?
Has sets of muscles that control the size of the pupil and regulate the light reaching the retina.
What are the cilliary muscles and suspensory ligaments ?
Change shape of the lens to focus light rays onto the retina.
What are rods ?
Photoreceptors that are sensitive to light
What are cones ?
Photoreceptors that are sensitive to colour. There are 3 types.
How does the pupil change in dim light ?
Radial muscles of the iris contract
Circular muscles of the iris relax
Pupil dilates to allow more light to enter the eye.
How does the pupil change in bright light ?
Radial muscles of the iris relax
Circular muscles of the iris contract
Pupil constricts to allow less light to enter through eye.
What is accommodation ?
The process of changing the shape of the lens to focus on a near or distant object.
How does the eye change when an object is near ?
Ciliary muscles contract
Suspensory ligaments slacken
Muscle tension is low
Lens shape is thicker
Refraction is strong
How does the eye change when an object is distance ?
Ciliary muscles relax
Suspensory ligaments are stretched
Muscle tension is high
Lens shape is thin
Refraction is low - only refracted slightly
What is myopia ?
Short-sightedness
What is myopia caused by ?
Elongated eyeball - distance between lens and retina is too great
Lens too thick and curved - light is focused in front of the retina.
What lens corrects myopia ?
Concave
What is hyperopia ?
Long-sightedness
What is hyperopia caused by ?
Too short eyeball - distance between lens ad retina is too small
Loss of elasticity in lens - cannot become thick enough to focus, focuses light behind retina instead
What lens corrects hyperopia ?
Convex lens
How do contact lenses correct defects of the eye ?
They float on the surface of the eye, focusing and refracting light
How does laser eye surgery correct defects of the eye ?
Reshape cornea surgically
How do replacement lens correct defects of the eye ?
An artificial lens can be placed in front of the original lens, through a small cut in the cornea.
A recent development.
