B10 - The human nervous system 2️⃣✅ Flashcards
What is the function of the nervous system?
It enables organisms to react to their surroundings and coordinates behaviour
What are the 2 parts of the central nervous system?
The brain and spinal cord
Why are reflex actions described as rapid and automatic?
They do not involve the conscious part of the brain to happen almost automatically
Why are reflex actions important?
For survival value and to prevent damage to the body
Give the pathway of a nervous response
Stimulus → receptor → coordinator → effector → response
Give the function of the cerebral cortex
The frontal area of the brain associated with consciousness, memory and language
Give the function of the medulla
The region of the brain concerned with unconscious activities such as breathing and heart rate
Give the function of the cerebellum
Region of the brain concerned with balance and coordination of muscular activity
Why is it so difficult to treat brain disorders?
Because the brain is so very complex and delicate, one wrong move could cause permanent or fatal damage
What is a synapse?
A synapse is a ‘junction’ between 2 neurones (where they connect and transmit information/ electrical impulses)
What is the function of a neurone?
To carry electrical impulses around the body
What is homeostasis?
The maintenance of a constant internal environment
Give 3 internal conditions controlled by homeostasis
Body temperature, blood glucose concentration and water levels
What is eye accomodation?
How the eye lens has to adjust its shape to be able to look at both near and distant objects so they are in sharp focus. For this to work light rays need to converge onto the focal point
Give two common defects of the eye
Myopia (short-sightedness) and Hyperopia (long-sightedness)
Give 3 ways eyes can be treated
Glasses, contact lenses & laser surgery
What happens if body temperature is too high?
Blood vessels dilate and sweat is produced
What happens if body temperature is too low?
Blood vessels constrict, sweating stops and shivering takes place
How do you treated myopia (short-sightedness)?
concave spectacle lenses
How do you treated hyperopia (long-sightedness)?
convex spectacle lenses
Explain a reflex arc
- Stimulus - e.g. hot surface
- sensory receptor - detects change
↓ sensory neurone - coordinator - CNS (central nervous system)
synapse
↓ relay neurone - ‘relays’ information between synapses
synapse
↓ motor neurone - delivers electrical impulse to effector - Effector (e.g. muscle)
- response (e.g. move arm away from hot surface)
What is a nerve?
A bundle of neurones
What is a neurone?
A single nerve cell
How do synapses work?
- electrical impulse arrives at the nerve ending in ‘neurone 1’
- the electrical impulse causes sacs inside the synapse to fill with neurotransmitter chemicals
- once enough sacs are full they will release the chemicals into the synaptic gap and the chemicals will diffuse across the gap, down the concentration gradient until they reach the complementary receptors on the other side of the gap
- The neurotransmitter chemicals easily bind to the complementary receptor, if enough receptors are triggered then it will trigger another electrical impulse to remain its journey, but now in ‘neurone 2’
How do stimulant drugs affect a response?
A stimulant drugs shape is similar to the neurotransmitter chemicals so can bind to receptor & increase the chances of an impulse so overall decreases reaction time
How do depressant drugs affect a response?
A depressant drug may have a complementary shape to the receptor, but block them, preventing electrical impulses from being released at the usual speed so overall increases reaction time
What is the cornea?
Transparent tough outer coat that refracts light as it enters the eye
What is the iris?
Its pigmented (colour of your eyes) so light cannot pass through. Its muscles contract and relax to alter the size of the pupil. It controls how much light enters the pupil
What is the lens?
Transparent flexible disc behind the iris attached by the suspensory ligaments to the ciliary muscles
What is the retina?
The lining of the back of the eye containing to types of photoreceptor cells, rods and cones. The retina contains the light receptors in the eye
What is the optic nerve?
A bundle of sensory neurones at the back of the eye that carries impulses from the eye to the brain
What are rods?
Photoreceptor cells that are sensitive to dim light and black and white
What are cones?
Photoreceptor cells that are sensitive to colour
In dim light the radial muscles _________ and the circular muscles _________ therefore the pupil diameter _______ to let ________ light in.
In dim light the radial muscles contract and the circular muscles relax therefore the pupil diameter widens to let more light in.
In bright light the radial muscles _________ and the circular muscles _________ therefore the pupil diameter _______ to let ________ light in.
In bright light the radial muscles relax and the circular muscles contract therefore the pupil diameter shrinks to let less light in.
Label this eye
Label this brain
When seeing a near object, the lens shape becomes ________________________ in order to be able to ________ light more so it converges on the focal point to form a clear image
When seeing a near object, the lens shape becomes short and fat in order to be able to refract light more so it converges on the focal point to form a clear image
When seeing a distant object, the lens shape becomes ________________________ in order to be able to ________ light less as ________ does most of the refraction; this is so it converges on the focal point to form a clear image
When seeing a distant object, the lens shape becomes long and thin in order to be able to refract light less as cornea does most of the refraction; this is so it converges on the focal point to form a clear image
What are the structures associated with eye accomodation/ change of shape of the lens?
suspensory ligaments and cilliary muscles
What are the structures assosciated with eye relfex in dim/ bright light?
radial muscles and circular muscles
In order for lens shape to become short and fat the suspensory ligaments are ________ as the cilliary muscles have ___________
In order for lens shape to become short and fat the suspensory ligaments are slacken as the cilliary muscles have contracted
In order for lens shape to become long and thin the suspensory ligaments are ________ as the cilliary muscles have ___________
In order for lens shape to become short and fat the suspensory ligaments are taught as the cilliary muscles have relaxed
