B3.1 Flashcards
What is the nervous system?
Where a stimulus is detected by the body and send this as an impulse to the brain
The brain decides the appropriate response and tells the body how to respond
What are the stages of a reflex arc? (non specific)
1) A stimulus is detected by receptors
2) The impulse travels along the sensory neurone and reaches the CNS
3) The impulse synapses with the relay neurone
4) Then it synapses with the motor neurone which takes the impulse to an effector (muscle/gland)
5) Then there is a response
What is the CNS?
Made up of the brain and spinal cord
Made of delicate tissue so protected by bones (skull & backbone)
What receptor cells would the skin have?
Pressure and Temperature (change in heat)
What does a sensory neurone do?
Carries electrical impulses from receptor cells to the CNS
What is the structure of a sensory neurone?
Receptors on one end
Nucleus in the middle of the structure inside cell body
Axon (after the cell body), dendron (before)
Myelin sheath - impulses travel between these
What do relay neurones do?
Carry electrical impulses from sensory neurone to motor neurone
What does a mitote neurone do?
Carries electrical impulses from the CNS to the effectors
What is the structure of a motor neurone?
Same as sensory neurone but cell body is at the start
No dendron
What are nerves?
Bundles (hundreds & thousands) of neurones
What is a reflex?
Involuntary actions
Unconscious
Occur when in danger
What are the structures & description in the eye?
Cornea - transparent coating in front of the eye
Pupil - central hole in the iris
Iris - coloured ring of muscle tissue
Lens - transparent biconvex lens
Ciliary body - ring of muscle tissue
Suspensory ligaments - ligament tissue
Optic nerve - nervous tissue
What are their different functions?
Cornea - protects the eye, first point of refraction of light
Pupil - allows light to enter the eye
Iris - alters pupil size by contracting or relaxing
Lens - focuses light clearly onto the retina
Ciliary body - alters the shape of the lens
Suspensory ligaments - connects the ciliary muscle to the lens
Optic nerve - carries nervous impulses to the brain
What is the retina?
Where the light is reflected from the eye onto so an image is formed
How are images formed?
Photoreceptors (light sensitive cells) in the retina produce a nervous impulse when exposed to light
This impulse travels down the optic nerve to the brain where it is interpreted as an image
What happens to the pupil in dim light?
The pupil dilates:
- radial muscles contract
- circular muscles relax
What happens to the pupil in bright light?
Pupil constricts:
- radial muscles relax
- circular muscles contract
What is accommodation?
The way the lens changes to focus on different objects
How do you focus on a near object?
1) The ciliary muscle contracts
2) Causes the suspensory ligaments to slacken
3) Lens become thicker so light is refracted more
How do you focus on distant objects?
1) Ciliary muscle relaxes
2) Suspensory ligaments taught
3) Lens becomes thinner so less light is refracted
What is myopia?
Short sightedness
Lens is more curved or eyeball is too long (light is refracted too much)
Focal point is not on retina but infront
How to treat myopia?
Concave lens
Diverges light rays before entering the eye
What is hyperopia?
Long sightedness
Lens is less curved or eyeball is too short
Focal point is behind the eye
How to treat hyperopia?
Convex lens
Converges the light rays before entering the eye
What are the two photoreceptors?
Cones - respond to different colours
Rods - respond to different light levels
What is the function of the brain?
Processes all the information from receptors & hormonal system
What is the structure of the brain
Cerebrum - controls complex behaviour (memory, personality)
Cerebellum - controls posture, balance and involuntary actions
Medulla - controls automatic responses (heart rate)
Hypothalamus - regulates temperature and water balance
Pituitary gland - stores and release hormones that regulate the bidy
What are the difficulties with investigating the brain?
- patients must give consent for information to be shared
- many believe animal testing is unethical
What is the peripheral nervous system?
All the neurones that connect the CNS to the rest of the body
How does damage to the nervous system occur?
Injury
Disease - diabetes, cancer
Genetic condition - Huntingtons
Ingesting toxic substances
What are the effects of damage to the nervous system?
Inability to detect pain
Numbness
Loss of coordination
Why is damage to the CNS more severe?
PNS has limited ability to regenerate
Minor damage self heals
damage to CNS means loss of control systems, paralysis, memory loss
CNS cannot regenerate
Why is it difficult to repair CNS?
Many nerve fibres so identifying and repairing each fibre without damaging others is difficult
Difficult to diagnose damage to brain
What treatments are for brain damage?
Radiotherapy & chemotherapy
Surgery
Deep brain stimulation (inserting and electrode to the brsin
