Lecture 6 Flashcards
What are the 5 layers of the general sensory hierachy
Receptors. Thalamic Nuclei. Primary Sensory Cortex. Secondary Sensory Cortex. Association Cortex.
Describe the general sensory hierachy
At the bottom are the receptors, which are the neurons that gather the information from the outside world and the body and send it to the thalamic nuclei. The primary sensory cortex then receives most of its input from the thalamic nuclei. From the primary sensory cortex information goes up to the secondary sensory cortex of the same system. Then the association cortex receives input from this, as well as from other sensory systems.
Define sensation
Process of detecting the presence of a stimulus.
Define perception
Higher-order process of integrating, recognising and interpreting sensations
What are the 6 most important parts of the eye
Pupils & Iris. Lens. Retina. Fovea. Blind spot. Optic nerve.
Where does light enter the eye
Through the pupil.
How is the size of the pupil regulated
By the iris, which is a band of contractile tissue.
Discuss the differences between pupil size
High illumination = small pupil.
Where does the light go and what does it do when it enters the pupil
Through the lens. Focuses incoming light on the retina & turns everything upside down
What is the job of the retina
It contains the receptors and four other types of neurons which are arranged in layers - the receptor cells are the innermost layer
What is the innermost layer of neurons
Receptor cells
What leave the eye in one bundle
Axons of the retinal ganglion cells.
What is the bundle (the eye) called
Optic nerve.
Why is there a blind spot
Because where the optic nerve leaves the eye there is a gap in the receptor layer, which is the blind spot.
Are we aware of the blind spot
Not usually, because the eye is constantly moving and the visual system will fill in the missing information from receptors that surround the blind spot.
Describe the fovea
It is specialized for high-acuity vision. It is a small area in the centre of the retina with a diameter of 33mm
Name the two types of receptors in the retina
Rods and Cones
Describe what rod receptors are
Periphery of the retina. Respond best to faint light. 20x more than cones. Many rods converge to one ganglion cell.
Describe what cone receptors are
Primarily in the fovea, but also around it too. Respond best to bright light and are essential for colour vision. For the cones in the fovea, each cone is associated with one ganglion cell, but also other cones are characterised by a generally low convergence - meaning few cones converge to one ganglion cell
Discuss the photopigments within rods and cones
When struck by light the photopigments release energy. The energy activates second messengers - the second messenger is a chemical that carries messages to several areas within the neuron. Second messengers inhibit the activity of the receptor cell, which initiates other neurons (including the ganglion cells) to the brain
