Nervous system and structure of the eye Flashcards
What is sensibility
The ability to detect or sense changes in the environment
What are the two systems that control the body
nervous system
endocrine system
What is a stimulus
A change in an organism’s surroundings
What is a receptor
receptors detect stimuluses and transduce the stimulus’ energy into electrical impulses
What is an effector
a muscle or gland that brings about a response to a stimulus
What can the ear detect
vibrations, sound, spacial positioning
What can the nose detect
chemicals in the air through nose chemoreceptors
what is the function of the nervous system
The nervous system uses electrical impulses to bring about fast but short lived responses which enable organisms to react to their surroundings and co-ordinate their behaviour.
what are the parts of the nervous system
CNS - central nervous system - brain, spinal cord
PNS - Peripheral nervous system- the rest
What are neurones
Specialised cells which carry electrical impulses
There are three types:
* Motor
* Sensor
* autonomic
* relay???
PRACTICE DRAWING NERVE CELLS MOTOR AND SENSORY
What can influence reaction time?
- age
- sex
- physical fitness
- fatigue
- distraction
- alcohol
- whether the stimulus is auditory or visual
- diet
- drugs - stimulus or depressant
What is a synapse
A gap where two neurones meet
How do impulses travel synapses
chemicals called neurotransmitters are released by the first neurone which carries the electrical impulse which diffuses across the gap and makes the next neurone transmit an electrical impulse by attaching to receptors on its surface.
PRACTICE STRUCTURE OF THE eye
What is the function of the cornea
transparent surface, meaning refraction occurs to focus light on retina
What is the function of the pupil
Hole in centre of iris through which light enters the eye
What is the function of the retina
Contains light sensitive receptor cells called rods (which respond to low light intensity but not wavelength à black and white) and cones (which respond to different wavelengths but only work in high intensity light à colour). It is dark to absorb as much light as possible.
Reflects light onto the optic nerve
What is the function of the optic nerve
Carries electrical impulses from the receptors along sensory neurones to the brain
Fovea
Where most cone cells are found on the retina
Ciliary muscle
Changing the shape of the lens by contracting which helps focus the light on the retina
Suspensory ligaments
slacken or become taught changing the shape of the lens
lens
A curved structure in the eye that bends the light entering the light through refraction and focuses it so that it hits the retina
Iris
This regulates the amount of light that accesses the back of the eye. This can dilate (expands eye) or constrict so that the right amount of light can be received
Sclera
This is the supporting wall of the eyeball
blind spot
This is where the eye cannot see, because the light cannot be reflected by the retina if it hits the nerve.
Conjunctiva
This is a transparent mucous membrane on the surface of the eyelids, which keeps the surface of the eye:
moist
lubricated
protected from dust
and can generate tears with glands
What are reflex actions
rapid, automatic and involuntary response of the nervous system which do not involve the brain as they pass through a relay neurone
Undergoes a reflex arc
What is the order that impulses travel in a reflex action
- A stimulus (heat) is received by a receptor
- The receptor converts this information into an impulse.
- This impulse is transmitted along a sensory neurone
- This impulse is transmitted along a relay neurone
- The impulse is transmitted along a motor neurone to an effector
- Effector (arm muscle) brings about a response by the arm muscle contracting which pulls hand away from flame.
Also known as reflex arc
What are the different types of photoreceptors in the eye
On the retina - cones and rods
What is the function of cones
colour vision - can detect primary colours r g b
located in the fovea
sensitive to high-light intensities
What is the function of rods
responsible for night vision Sensitive to low light intensities
around the periphery of the retina
How can an image be seen
light refracts on the cornea and the lens onto the retina where it is reflected. Means image is inverted at first, but the brain flips the image
What is accomodation
changes in the eye that allows us to see objects at different distances
accommodation (near vision)
ciliary muscles contract, suspensory ligaments slacken leading to thick lens increasing the refraction of light
Accommodation(distant vision)
ciliary muscles are relaxed, suspensory ligaments are tense and the lens are thin to allow for less refraction
What changes in the eye with different light intensities and why
high light intensity → pupil constricts
less light is absorbed to avoid damaging retina
low light intensity → pupil expands
This means that more light can be absorbed
How does the pupil constrict/expand
pupil expands by zonular fibres tightening and ciliary muscles relaxing
pupil constricts by zonular fibres relaxing and ciliary muscles contracting.
Antagonistic muscles
How are nerve cells adapted for their function
- long
- myelin sheath
- can make many connections
