B3.1 - Nervous system Flashcards
What does the nervous system do
- detects change in external environment and sends it to the brain
what are the three stages of a nervous response?
1) stimulus (change in environment)
2) sensory receptor (detects stimulus)
3) effector (responds to an impulse)
how to glands respond to a stimuli?
release hormones
where are receptor cells found?
sense organs (eyes, ears, nose, tongue, skin)
what do receptor cells do?
change the stimuli to electric impulses to travel along neurone to CNS
what is the CNS made of?
brain and spinal cord
how is the spinal cord protected?
by the vertebrae column (backbone)
what is the stimulus for skin?
pressure, heat
what is the role of sensory neurones?
carry electric impulses from receptor cells to CNS
what is the role of motor neurones?
carry electric impulses from CNS to effectors
what is the nervous system made of?
- brain
- -spinal cord
- neurones
what are effectors?
muscles or glands that respond to the change in environment
what are synapses?
gaps between neurones which allows nerve impulses to travel
how do synapses work?
- electrical impulse reaches the end of neurone
- triggers the release of chemicals called neurotransmitters from vesicles
- neurotransmitters diffuse (move down a concentration gradient) across the synapse.
- neurotransmitters bind to receptors on the next neurone.
- presence of the neurotransmitter causes the production of an electrical impulse in the next neurone.
how do reflex actions help?
allow us to respond to dangerous situations rapidly and automatically
give three examples of reflex actions
blinking, sneezing, flinching from a hot pan
what is a stimulus?
change in the environment to which the body needs to respond
describe the reflex arc
- stimulus detected by a receptor
- sensory neurone carries signal (through impulse) to CNS
- motor neurone carries electrical impulse from the CNS to an effector.
- effector (a muscle or gland) produces the response to the stimulus
what can effect human reaction time?
caffeine, exercise
what is the role of the brain?
processes all the information collected by body and produces a co-ordinated response
medulla
Automatic actions (breathing rate, heart rate)
cerebellum
muscle coordination (AD)
- posture, balance, involuntary movements (MD)
cerebral cortex
Outer later of the cerebrum
Why is it hard to treat brain damage or problems in the brain?
we don’t understand it enough, easy to make mistake and cause irreversible damage
name some of the techniques used in neuroscience
- studying brain damage
- electrical stimulation
- MRI scanners
name different damages to PNS or CNS
- injury - falling of a ladder
- disease - cancer, diabetes
- genetic condition - Huntington’s
- ingesting a toxic substance (lead)
what does damaging the nervous system cause?
prevents impulse being passed through nervous system effectively
effects of PNS damage?
Can affect both sensory and motor neurones. May result in:
- inability to detect pain
- numbness
- lack of co-ordination
list features of PNS damage - fixing it means.
- limited ability to regenerate (minor nerve damage self heals), and symptoms gradually decrease
- severe nerve damage treated through surgery
how can nerve damage be treated through surgery?
sections of nervous tissue can be grafted over damaged tissue (restoring electric conduction path for impulse)
can the CNS regenerate
no, unless corrected by surgery
why is it difficult to repair the spinal cord?
- 1.5 cm in diameter
- so identifying and repairing damage to an individual nerve fibre without damaging others is difficult
why is damage to the interior of the brain difficult to treat?
it is difficult to diagnose, not many different treatments available as hard to test, as may kill person
optic nerve function
Transmits visual information, in the form of electrical impulses, from the retina to the brain
cornea
The transparent frontal portion of the eye responsible for refracting light entering the eye
+ protects the eye
sclera
The white of the eye; the opaque protective outer layer (all around the eye)
- even in a cross-sectional diagram, would see it on outer edge
retina
- Packed with receptor cells
- sensitive to both the brightness
- colour of light
pupil
A hole in the centre of the iris through which light passes to get to the retina
iris
- controls pupil dilation and quantity of light reaching retina
ciliary muscles
- ring of muscle tissue
- alters the shape of lens (to focus light)
suspensory ligaments
- ring of fibres, connect ciliary muscle to lens
what is the process of changing lens shape in order to focus on an object at its distance from the eye changes?
accommodation
What happens when our eyes focus on a distant object?
- ciliary muscles relax
- suspensory ligaments tighten
- lens become flatter and thinner
- minor refraction of light rays
what controls how our eyes adapt to different light levels?
iris
what is hyperopia, and treatment?
- longsightedness
- lens too thin
- eyeball too short
- light ends up behind retina
- convex lens (fat one)
what is myopia and treatment?
- short sightedness
- lens too thick
- eyeball too long
- light in front of retina
- concave lens
what causes colour blindness?
- defects in the photoreceptors
focusing on a close object?
contraction of the ciliary muscles and loosening of the suspensory ligaments.
focusing on a far object?
loosening of the ciliary muscles and contraction of the suspensory ligaments.
as people get older, the lens in the eye becomes less flexible and cannot change shape easily.
This means they cannot focus clearly on near objects.
Explain why.
- lens cannot become fat
- light is focused behind retina
what is a CT scan and what does it show?
- computed tomography
- uses X-rays to create 3D images of inside of body
- but cannot be used regularly (X-rays can cause cancers)
- only show still images
what is MRI scanning and how does it work?
- magnetic resonance imaging
- use powerful magnets to identify brain abnormalities
- see which areas of brain are active
what is fMRI scanning and how does it work?
- functional magnetic resonance imaging
- produces images in real time by sending magnetic radiation
- radiation bounces back and can see the properties/density of tissue ie. whether it is oxygenated or not
- areas are active when increased blood flow during a specific activity
how does electrical stimulation work?
- electrodes places inside animal/human brains
- electrodes transmit electrical impulses + result in movement
what does the cerebrum control?
complex behaviour (memory/learning/personality/conscious thought)
draw a neurone out
label with - nucleus, cell body, axon, dendrites
nucleus - little circle
cell body - area around little circle
axon - the body - long bit
dendrites - sticky out bits around cell body
How muscles respond to an impulse?
Contracting
Receptor cells of : skin + stimulus
Pressure, temperature
Pressure, heat
Receptor cells of nose + stimulus
Smell, taste.
Chemical, chemical
What relay neurones do?
Carry electrical impulses from sensory neurones to motor neurones
Nerves are
Bundles of neurones
Steps of nervous reaction, flow diagram .
How long?
Stimulus -> receptor cells > sensory neurone > spinal cord > brain > spinal chord > motor neurone > effector > response
0.7 seconds
Breathing, Heart rate, digestion are examples of what actions
Reflex
There are reflex actions that take care of basic bodily functions
Reflex arc flow diagram
Stimulus > receptor cells > sensory neurone > spinal cord > motor neurone > effector > response
Lens : description
Transparent biconvex lens
Optic nerve: description
Nervous tissue - carries nerve impulses to brain
Why have a central control centre - brain?
So that neuronal commutation is much faster than if control centres for different functions were spread around the body
Hypothalamus
Regulates temperature and water balance
Pituitary gland
Stores and releases hormones that regulate many body functions
PNS: - consists of
Consists of all the neurones that connect the CNS to the rest of the body
Damage to CNS is more severe, it can lead to:
- loss of control of body systems
- partial or complete paralysis
- memory loss or processing difficulties
Treatment to brain damage
Radiotherapy + chemotherapy — to treat brain tumour
Surgery — to remove damaged tissue
Deep brain stimulation — inserting an electrode to stimulate brain function
What are Schwann cells
The axons are insulated by fatty myelin sheath called Schwann cells = so electrical impulses don’t leak/dissipate
Where are relay neurones found
ONLY in CNS when it is a REFLEX = no brain
Label the eye
- Sclera - Tough outer wall, ‘White’
- Conjunctiva - membrane over eye
- Cornea - transparent outer layer
- Lens - focuses light
- Pupil - allows light into eye
- Aqueous humor - nutrients & pressure
- Iris - controls diameter of pupil via circular and radial muscles
- Vitreous humor - pressure and shape.
- Choroid - nutrients & waste
- Fovea - blind spot
- Optic nerve head - nerves exit
- Optic nerve - impulses to eye
- Retina - contains rods & cones
Axon
transmits the nerve impulse away from the cell body and onto the next neurone.
Dendron
carries the nerve impulse from the last neurone to the cell body.
Sensory neurone
Motor Neurone
How do your eyes adjust to different levels of light
- In dim light the radial muscles contract and the circular muscles relax to make the pupil become larger to allow more light to reach the retina.
- In bright light the radial muscles relax and the circular muscles contract to make the pupil become smaller and protect the retina.
Function of the conjunctiva
- Protective membrane contiunuous with the eyelids across the front of the visible sclera
- Protects from infection by stopping pathogens entering the eye
Describe processes of accommodation
- When an object is nearby the cilliarymusclecontracts down towards the lens allowing the suspensory muscles to become slack. This causes the lens to fatten and become more convex, increasing the refraction of the light passing through.
- When an object is far the cilliarymusclerelaxes away from the lens allowing the pulling the suspensory muscles taut. This causes the lens to be pulled thiner and become less convex, decreasing the refraction of the light passing through
