9.2 Flashcards
What is the cornea?
A clear window at the front of the eye which allows light to enter.
What is special about the shape of the cornea?
Its shape allows it to function as a fixed focusing device. Responsible for 70-80% of the total focusing ability of the eye.
What are the eye and the pupil?
The size of the iris can vary to control the amount of light that enters the eye.
The pupil is the dark area at the centre.
What is the lens and why is it important?
It adjusts the level of focus.
When is the lens thickest and thinnest.
The lens is thickest when looking at a near object.
It is flattened when looking at a far object.
What effects accommodation (the lens)
Age and fatigue.
What is the retina.
A complex layer of nerve cells at the back of the eye connected to the optical nerve.
Contains two types of light sensitive cells: cones and Rods.
What are cones and how are they different from Rods?
Cones function in good light.
Cones can detect fine detail.
Rods.
Rods cannot detect colour.
Good at detecting movement in peripheral vision.
Cones are in the centre of the retina and rods are in the peripherals.
The fovea?
A small depression at the centre of the retina that is rés poi le for central vision
What does visual acuity mean?
The ability to discriminate sharp detail at varying details.
What is hypermetropia?
Long sightedness.
Shorter than normal eyeball
Lens is shorter than normal.
Objects nearby will appear blurred
What type of lens is used to correct hypermetropia?
Convex lens.
What is myopia?
Short-sightedness.
Eyeball is longer than normal.
Image is formed in front f the retina.
Distant objects will appear blurred.
What are other forms of visual problems?
Cataracts - clouding of lens (age related)
Astigmatism - misshapen cornea
Glaucoma - a build up in pressure of the fluid
Migraine - severe headaches, distort vision.
Presbyopia - loss of lens flexibility (age related)
Fatigue
Influence of foreign substances on vision.
(Drugs)
Reduces supply of oxygen to eye which can affect the sensitivity of the rods.
How long does it take foe cones and rods to adjust to changing lighting conditions.
7 minutes for cones
30 minutes for rods
What is colour blindness called
Colour vision deficiency
What % of people are effected by colour vision deficiency
8%of men
0.5% of women
Can age affect colour vision?
Yes due to yellowing of the lens.
CAP 563 Leaflet H-60
Use of glasses or contact lenses is suitable if prescribed for an engineer
What are the three divisions of the ear
Outer
Middle
Inner
Outer ear
The part of the ear that directs the sound along the auditory canal and into the eardrum.
Middle ear
Sits in the eardrum, transmits vibrations.
Made of three small bones called hammer, anvil, stirrup.
Inner ear
Filled with fluid.
Connected to the cochlea which contain hair like cells which react to the movement of the fluid and send of neural responses
What are aural reflex muscles.
Can reduce loud noises by 20db.
No protection to sudden explosive noises.
What range of frequency can a young person typically hear
20 - 20,000 Hz
Sensitivity peaks at 3000, Hz
Impact of noie on performance
Annoying others.
Interfering with communications
Causing fatigue and effecting concentration
Damage hearing.
What are regulations related to noise and hearing.
Employers must provide hearing protection if needed.
Employees have legal right to work without exposure to dangerous noise levels.
Two types of hearing protection, and how much protection the provide.
Ear plugs, ear defenders.
Noise levels are reduced by 20dB and 40dB respectively
Signs of early hearing loss.
Conversations become difficult or impossible.
You find it difficult to process sounds like “d” “t”
Permanent tinnitus.
Noise dose.
Any sound over 80dB over an 8 hour period
Any noise over 115 for even short period of time.
What is the process of information processing
Receiving information through the senses
Analysing information
Deriving meaning from the information
Storing information.
Iconic memory
Provides a smooth stream of visual information to the brain which can be extracted over an extended period of time in the visual short term memory.
Presbycusis
Hearing loss with age
Echoic memory
Registers sound, once a sound Is heard it is stored in the echoic memory where it can be processed and understood.
What are the forms of attention.
Selective attention
Divided attention
Focussed attention
Sustained attention
What is “attention”
The brain function that alllocates cognitive processing resources to focus on information or stimuli.
Selective attention.
When a person is monitoring several sources of input but focuses on the source that seems ore important
Divided attention
Divided attention is common in most work situations, where people are required to do more than one thing at a time
Focussed attention
Simply channeling your attention towards a single source and avoiding distraction.
Sustained attention.
Is the ability to maintain concentration and remain alert over long periods of time. Usually on one task.
What can perception be defined as?
the process of assembling sensations into a usable mental representation of the world
What are the three processes of memory
Encoding, storage, retrieval.
What is encoding (memory)
The input of information into the brain
3 types of memory.
Sensory memory
Short-term memory
Long-term memory.
Sensory memory
Ultra-short memory.
Consists of brief sensory events such as sights, sounds and tastes.
Very brief, up to a few seconds.
Short term memory
Takes information from sensory memory and sometimes connectes that memory to something.
Long term memory.
Used to store information no longer in use
Two types of long term memory
Semantic memory
General facts
Episodic memory.
Events
(Motor programmes
Driving a car)
What is retrieval
The act of getting information out of memory storage and back into conscious awareness.
Decision making is bases on retrieval and past experiences.
What is situation awareness
The synthesis of n accurate and up-to-date mental model of ones environment and state, and the ability to use this to make predictions about ones future state.
The influence of expectation.
Our perceptual system can reject irregularities, for example when skim reading you wont notice subtle changes in a text that you think you know well.
What is claustrophobia
Fear of enclosed spaces.
What is acrophobia
Fear of heights
