B3.1: The Nervous System Flashcards
What is your nervous system?
It detects change in your external environment
It is made up on the brain, spinal cord and nerves
What causes change in the environment?
A stimulus
What detects the stimulus?
Groups of cells - these are sensory receptors
The effectors respond
Muscles or glands
How do glands respond?
By releasing hormones
How do muscles respond?
By contracting - movement
Receptor cells for eye
Rods and cones
Receptor cells for tongue
Taste buds
Receptor cells for skin
Temperature and pressure
Receptor cells for nose
Smell and taste
Stimulus for eye
Light
Stimulus for tongue
Chemical
Stimulus for skin
Pressure and heat
Stimulus for nose
Chemical and chemical
3 types of neurone
Sensory, relay, motor
What do sensory nerves do?
Carry electrical impulses from receptor cells to the CNS
What do relay nerves do?
Carry electrical impulses from sensory to motor
What do motor nerves do?
Carry electrical impulses from CNS to glands/muscles (effectors)
Flowchart to nervous response
Stimulus -> receptor -> sensory neurone -> CNS -> relay nerve -> motor neurone -> effector -> response
What is a reflex action?
An automatic response to a stimulus
How does a synapse work?
- impulse arrives at synapse
- neurotransmitter is released and diffuses across the gap
- bind to receptor which triggers a new impulse
Eye anatomy
- iris
- cornea
- suspensory ligaments
- ciliary muscle
- retina
- optic nerve
- lens
- pupil
Iris
Alters pupil size by contracting/relaxing
Lens
Focuses light clearly onto the retina and refracts it
Cornea
Protects the eye, refracts light
Pupil
Black hole in the eye which allows light to pass through
Optic nerve
Carries nerve impulses to the brain
Retina
Has light receptors which detect light and convert into electric impulses -> optic nerve
Ciliary muscle
Alters the shape of the lens
Suspensory ligaments
Connects the ciliary muscle to the lens
In dim light
Pupil dilates
Circular muscle relaxes and radial muscle contracts
In bright light
Pupil constricts
Circular muscle contracts and radial muscle relaxes
How does the eye work?
- light enters the eye through the pupil and is refracted by the cornea and the lens
- light rays are focused onto the retina and the image is sent to the brain via the optic nerve
What is accommodation?
- when our lens changes shape in order to focus light coming from different distances
- shape of our lens is controlled by the ciliary muscle
For close objects
- ciliary muscle contracts
- suspensory ligaments are relaxing
- lens becomes thicker
For near objects
- ciliary muscle relaxes
- suspensory ligaments are contracting
- lens becomes thinner
Long sightedness (hypermetropia)
- can’t see objects far away
- eyeball is too short or lens is too weak
- image forms behind retina
Short sightedness (myopia)
- can’t see objects near
- eyeball is too long or lens is too strong
- image forms infront retina
Correcting short sightedness
- using a concave lens
- refracts light rays outwards
- clear image forms on the retina
Correcting long sightedness
- using a convex lens
- refracts light rays inwards
- clear image forms on the retina
What is colour blindness?
- people who have difficulty making out colours or who cannot see colour at all
Rods
Respond to light and allow you to see in low light levels
Cones
Respond to different colours - different cone cells respond to red, blue and green light
What is the brain?
- complex organ
- more than 100 billion nerves that communicate in trillions of connections called synapses
Cerebrum
Controls complex behaviour such as learning and memory, personality and conscious thought and language
Cerebellum
Controls posture and balance and involuntary movements
Medulla
Controls automatic actions such as blinking and breathing
Hypothalumus
Regulates temperature and water balanceP
Pituitary gland
Stores and releases hormones that regulates many body functions
3 ways of investigating the brain
- electrodes
- CT scans
- MRI scans
Electrodes
- placed inside animal and human brains
- transmit electrical impulses which results in movement in different parts of their body
- allows scientists to link an area of the brain to region of the body it controls
CT (computed tomography)
- uses x-rays to create 3D images of inside of the body
- can’t be done regularly because of radiation
- links to changes in patient’s behaviour
MRI (magnetic resonance imaging)
- use powerful magnets to identify brain abnormalities
- fMRI produces images in real time
CNS (central nervous system)
Brain and spinal cord
PNS (peripheral nervous system)
All neurones connected CNS to the rest of the body
Damage that can occur
- injury
- disease
- genetic condition
- ingesting a toxic substance
Effects of the damage
- inability to detect some stimuli
- numbness
- loss of coordiantion
PNS damage
- limited ability to regenerate
- minor nerve damage: self heals
- major nerve damage: surgery
CNS damage
- loss of control of body systems
- partial/complete paralysis
- processing difficulties/memory loss
- CNS cannot regenerate
CNS serious damage
- disease or damage to the spinal cord or brain is often impossible to repair
- spinal cord has 31 pairs of nerves, repairing one nerve without damaging another is tricky
- spinal injuries usually lead to permanent disability
Diagnosis
- damage to the brain is often difficult to diagnose but you can use MRI and CT scans
Treatment for brain tumour
Radiotherapy
Chemotherapy
Treatment to remove damaged brain tissue
Surgery
What is a reflex?
An automatic response to a stimulus
