B3.1 The nervous system Flashcards
What does the nervous system do?
detect + respond to changes in environment
what is the nervous system needed for?
move, communicate, control internal processes + carry out higher order functions like memory + thinking
what are neurones?
Specialised nerve cells which transmit electrical impulses around the nervous system
What does the CNS contain?
Central nervous system - brain + spine
How is the CNS linked to the rest of the body?
by neurones of the PNS (peripheral nervous system)
What is a stimulus?
a change in the environment
What do receptors do?
detect the stimulus
what dies the CNS do?
co-ordinates how and where impulses are transmitted next
What are the effectors?
muscles or glands
What is the response?
a reaction to stimulus carried out by the effector
5 main stages leading to a nervous response?
Stimulus –> Receptors –> CNS –> Effectors –> Response
Draw a sensory neurone
what are reflexes?
involuntary responses that occur without conscious thought - don’t have control over these responses
are reflexes fast?
very fast - 0.2 seconds - need to be fast to protect us from harm
What is a reflex arc?
pathway taken by the impulse during a reflex action
describe the reflex arc when you tough something hot
- Stimulus - touching hot pan
- Receptor - temp receptors in skin
- Sensory neurone
- Spinal cord
- motor neurone
- Effector - bicep muscle contracts
- Response - hand pulled away
What is a synapse?
the gap between 2 neurones
What happens in the synapse?
- elec impulses cant travel through
- chemicals (neurotransmitters) diffuse across the gap - diffusion across a synapse is sower than transmission of a nerve impulse along a neurone
what is the iris responsible?
controlling size of pupil + therefore amount of light falling on retina
where does light pass in the eye?
refracted by cornea and then through pupil to retina
- too much light = damage to light sensitive cells on retina
- too little light = not enough stimulus to cells
What is the antagonistic muscle pair in the iris?
circular + radial
- bright light = smaller pupil - circular contracted, radial relaxed - lets less light in
lens power (in eye) =
1 / focal length (m)
what does the cerebrum do?
controls complex higher level functions - learning, memory, behaviour, conscious thought - lobes coordinates diff sensory + motor info
what does the cerebellum do? (little brain!)
controls posture + balance - coordinates learned + fine movements
what does the medulla do?
contains control centres for automatic processes - e.g. HR + breathing
what does the hypothalamus do?
regulates body temp + water balance (homeostasis)
what does the pituitary gland do?
stores + releases important hormones
what does the corpus callosum do?
connects cerebral hemispheres to allow left + right brain to communicate
Imaging techniques - CT & MRI
- CT - computed tomography
- MRI - magnetic resonance imaging
- provide real times images throughout brain
CT scans
uses x-rays to create 3d images of inside brain + detect abnormalities
- cant be done regularly - x-rays increase cancer risk
MRI scans
use powerful magnets to identify abnormalities
- can identify areas of brain which are active during specific activities
limitations of investigating brain function
- same area could be used for multiple functions
- often many areas of brain are involved in a specific function
- ethical issues - testing
- patients must give consent for medical info to be shared
- getting large enough sample of case studies to draw reliable conclusions
label a motor neurone
label a relay neurone
label a sensory neurone
draw a motor neurone
draw a relay neurone
label a picture of the eye
label a picture of the brain
`when focusing on near objects does the light need to be refracted more or less?
more
what is accommodation in the eye?
Ability to change focal length of the lens by changing the curvature of the eye lens
accommodation - distant object
ciliary muscle relaxed
suspensory ligament tight
lens pulled thin
accommodation - near object
ciliary muscle contracts
suspensory ligament slackens
lens allowed to thicken
Short sightedness - CAN see short
- eye cant focus on distant object
- incorrect image forms in front of retina
- because eyeball is too long OR lens is too powerful
- ciliary muscles cant make lens thin enough to focus
How do you correct short sightedness?
concave lens - bend light out before enter the eye
Long sightedness - CAN see long
- eye cant focus on nearby objects
- incorrect image is formed behind retina
- eye lens cant thicken enough to focus on image on retina
- caused by lens being too weak / eyeball being too short
How do you correct long sightedness?
convex lens - bends light rays inwards before they enter the eye
what are the two types of receptor cells in the eye?
rods and cones
what do rods do?
respond to different light intensities - more sensitive to light than cones - help give good vision in low light
what do cones do?
respond to different colours (wavelengths of light) - work best in relatively bright light
What does the PNS consist of?
motor and sensory neurones
damage to PNS neurones result in what?
- inability / reduced ability to detect pain
- lack of ‘feeling’ - numbness
- loss coordination of actions
damage to the CNS result in what?
more severe
- loss of control of body systems
- partial or complete paralysis
- memory loss
- processing difficulties
treating the PNS
- PNS neurones have some ability to repair themselves - damaged neurones often regenerate from the cell body end of neurone forming new axons
- slow process - symptoms gradually fade overtime
- severe cases - use nervous tissue skin grafts
