Topic 10 - The Human Nervous System Flashcards
What is homeostasis?
Keeping the body in a steady state.
What is the advantage of homeostasis?
The body is kept at optimum conditions so that the metabolism is the most effective as possible.
What internal conditions need to be kept the same in the body?
1) Temperature - (37 degrees) so that enzymes don’t denature but work at optimum temperature.
2) pH - So enzymes don’t denature but work at optimum.
3) Water concentration - to keep an osmotic balance, so cells won’t burst or shrink.
4) Sugar + salt concentration - to maintain an osmotic balance.
What are the five stages of a reflex action?
1) Stimulus
2) Sensory Receptor
3) Co-ordinator (nervous system)
4) Effector
5) Response
Which neurones link the different stages of the reflex action?
1) The sensory neurone links the sensory receptor and the relay neurone in the central nervous system.
2) The relay neurone links the sensory neurone and the motor neurone in the central nervous system.
3) The motor neurone links the relay neurone with the effector (muscle or gland).
What two parts consist the nervous system?
1) Central Nervous System - brain + spinal cord (co-ordinators).
2) Peripheral Nervous System - goes to the furthest parts of the body (sensory + motor neurones).
What are neurones?
Long specialised cells that are normally found in bundles of hundreds or thousands of neurones called nerves.
What are receptors?
Cells that detect stimuli.
What are effectors?
Areas (muscles or glands normally) that bring about a response from the body.
What are coordination centres?
Areas that receive and process information from receptors.
What are reflex arcs?
They bring about a reflex action. They involve the sense organ, sensory, relay and motor neurones.
What are reflexes?
Rapid automatic responses of the nervous system that do not involve conscious thought.
What does the cerebral cortex do?
This is the region of the brain associated with consciousness, memory and language.
What does the medulla do?
This is the region of the brain concerned with unconscious activities like controlling heart or breathing rate. Additionally, the medulla controls long term memory storage.
What does the cerebellum do?
This is the region of the brain concerned with coordinating muscular activity and balance.
What does the hypothalamus control?
This is the region of the brain that controls body temperature.
What does the temporal lobe do?
Processing auditory information and with the encoding of memory.
What do the meninges do?
They are semi-permeable and prevent diseases from entering the brain.
What does the brain stem do?
Sends signals to the rest of the body.
What do MRI scans do?
They use magnetic resonance to scan different areas of brain for the different levels of activity.
What does electrically stimulating the brain do?
It can contract and relax muscles due to stimulating parts of the brain via electrodes.
What does the pituitary gland do?
Controls the release of hormones.
What does the cornea do?
Refracts light - bends it as it enters the eye.
What does the iris do?
Controls how much light enters the pupil of the eye.
What does the lens do?
Due to it ps transparency and bi-convex shape, it focuses light onto the retina.
What does the retina do?
It contains the light receptors at the back of the eye, allowing the light to be sent to the brain via the optic nerve.
What does the optic nerve do?
Carries impulses from the retina at the back of the eye to the brain.
How does the pupil change in dark conditions?
The circular muscles relax, the radial muscles of the iris contact and thus pupil diameter increases, so more light enters the eye.
How does the pupil change in bright conditions?
The circular muscles contract, radial muscles of the iris relax and thus pupil diameter decreases, so less light enters the eye.
What happens to the eye when it focuses on an object that is close up?
The ciliary muscle contracts, suspensory ligaments slack and thus a fat lens is made, bending light rays more.
What happens when the eye focuses on an object far away?
The ciliary muscles relax, suspensory ligaments are pulled tight and the lens is pulled long and thin and thus light isn’t bent as much.
What is myopia?
Near objects are clear, far objects are blurred. light rays are bent too much and the focal point is in front of the retina.
What is hypermetropia?
Where far objects are clear, near objects are blurred as light rays are not refracted enough, the focal point is behind the retina.
What is the order of the nervous system?
Stimulus –> Receptor –> Coordinator –> Effector
What is a reflex?
An automatic response by the body when a stimulus is detected.
What parts of a reflex action are there?
Stimulus
Sensory receptor
Sensory neurone
Cell body of sensory neurone
Relay neurone
Synapse
White matter
Grey matter
Spinal nerve
Spinal cord
Motor neurone
Motor end plate
Bicep muscle that contracts and relaxes
How do synapses work?
There are gaps between neurones
An electrical impulse arrives at the first neurone
The electrical impulse makes sacs containing neurotransmitter chemicals
Chemicals are released into the gap between neurones
The chemicals reach and attach to the receptor site
Chemicals attach to the surface of the next neurone and set up a new electrical impulse
What parts of the brain do you have to know for GCSE?
Cerebral cortex
Cerebellum
Hypothalamus
Medulla
Pituitary gland
What does the cerebral cortex do?
It manages consciousness, intelligence, memory and language
What does the cerebellum do?
Coordinates muscular activity and balance
What does the medulla do?
Unconscious activites like heartbeat, gut movements and breathing.
What does the hypothalamus do?
Controls body temperature
What does the pituitary gland do?
Secretes different hormones
What example of brain damage do you need to remember?
In 1848 an explosives accident blew an iron rod through the skull of Phineas Cage. He went from polite and hardworking to wild, rude and unreliable.
What can MRI scans do?
It can show which area of the brain is affected by a condition through magnetic resonance.
What problems are there with treating the brain?
Drugs don’t always reach the brain
Synapses and the brain tissue are easily damaged
Surgery is difficult as it is not fully understood
What parts of the eye do you need to know for GCSE?
Ciliary muscle
Suspensory ligament
Iris
Pupil
Cornea
Lens
Retina
Sclera
Blind spot where optic nerve leaves
Optic nerve
What is accommodation?
Adjusting the eye to suit the light reaching it
How does the eye accommodate focusing on a distant object?
Ciliary muscles relax
Suspensory ligaments pulled tight
Lens pulled flat and thin
Refracts light rays slightly
What is myopia?
Short sightedness
What is hyperopia?
Long sightedness
What technology can help damaged eyes?
Contact lenses
Laser eye surgery
Replacement lenses
How does the eye accommodate near objects?
Ciliary muscles contract
Suspensory ligaments loosen
Lens becomes thick and fat
How do contact lenses work?
They are placed on the surface of the eye, they act like glasses, properly focusing light on the retina but are not as visible.
How does laser eye surgery work?
This is only available to adults after their eyes have stopped growing.
The thickness of the cornea is reduced using lasers.
The lens now focuses distant light on the retina instead of in front of the retina.
