Week 6 Flashcards
What is the purpose of a sensory system?
To bring an organism in contact with the world
Sensory systems serve an adaptive purpose and do not necessarily convert the world faithfully.
What are the main components of all sensory systems?
- Sensory receptor cells
- Neural pathways
- Primary cortical area
- Higher cortical areas
What is the physical stimulus for vision?
Light
What part of the eye is responsible for focusing light?
- Pupil
- Cornea
- Lens
What are the two types of photoreceptors in the human retina?
- Rods
- Cones
What is convergence in terms of how rods work?
Many photoreceptors report to one cell
What is the primary function of rods?
Respond to low levels of illumination
How do cones differ from rods in terms of convergence?
Cones exhibit no convergence; each reports to its own cell
What are the three types of color-sensitive cones?
- Short
- Medium
- Long
What happens to photoreceptors in the dark?
They are active and release neurotransmitters
What is the ‘dark current’?
A constant influx of Na+ ions through special channels in the rod
What causes rods to hyperpolarize in response to light?
Light reduces the availability of a messenger that opens Na+ channels
What neurotransmitter do photoreceptors release in the dark?
Inhibitory neurotransmitter
What activates ON bipolar cells?
Release from inhibition when photoreceptors stop releasing neurotransmitter
What is the role of ganglion cells?
Pass information to the brain via the optic nerve
What is lateral inhibition?
A form of competition where activated photoreceptors suppress their neighbors
What is the optic chiasm?
The crossing point where some visual information crosses to the opposite side of the brain
Which brain region helps reset the body’s internal clock with daylight?
Superchiasmatic nucleus
What is the function of the lateral geniculate nucleus (LGN)?
Acts as a relay station for visual signals to the visual cortex
What is the significance of the fovea in the retina?
It contains only cones and is responsible for high acuity vision
Fill in the blank: The _______ is the opening where light enters the eye.
pupil
True or False: Cones are more sensitive to low light than rods.
False
What enhances the detection of edges in vision?
Lateral inhibition
How does light affect the activity of photoreceptors?
Inhibits their activity
What happens to bipolar cells when photoreceptors are no longer inhibited?
They become activated
What is the role of horizontal cells in the retina?
Receive input from photoreceptors and send outputs to nearby photoreceptors
