| when are endorphins released? | inescapable pain
sex, thrilling music
decreases depressed mood |
| What is the hierarchical organisation of the sensory system? | 1. association cortex
2. secondary sensory cortex
3. primary sensory cortex
4. thalamic nuclei
5. receptors |
| explain the levels of hierarchy | each level of sensory hierarchy receive input from lower levels
with increasing level neurons respond to stimuli of greater specificity |
| what is sensory organisation? | hierarchical organisation also reflected in differentiation sensation & perception |
| what does sensation mean? | process of detecting presence of stimulius |
| what does perception mean? | higher order process of integrating recognising & interpreting sensations |
| describe what the pupil does | light enters eye through pupil
size of pupil regulated by iris
high illumination= small pupil |
| what is the retina? | contains receptors & 4 other types of neurons
neurons arranged in layers, receptor cells on innermost layer |
| axons in the retinal ganglion cell.. | leave the eye in a bundle
bundle- optic nerve
= gap in receptor layer= blind spot
blind spot filled by visual system from surrounding receptors |
| what is the fovea? | area in centre of retina
specialised for high vision |
| what are rods? | periphery of retina
respond best to faint light
outnumber cones (20x)
many rods converge to 1 ganglion cell |
| what are cones? | fovea, also surround fovea
respond to bright light
needed for colour vision
each cone associated with one ganglion cell |
| what is a photopigment? | when struck by light, release energy
activates 2nd messengers
inhibit activity of receptor cell
initiates signal transduction across other neurons |
| what is the retina geniculate striate pathway? | 90% of axons of ganglion cells
signals from left visual field reach right visual cortex & vice versa |
| retina to primary visual cortex | light from left visual field meets right retina
axons from nasal part of retinas cross (optic chiasm)
axons from temporal part of retinas don't cross
after optic chiasm
signals go through thalamus to primary visual cortex |
| what is the summarised pathway of light? | eye > retina > brain |
| what is optic chiasm? | axons from nasal part of the retinas cross |
| what is edge perception? | contrast perception |
| why do we need to move our eyes? | 3 brief eye movements per saccades
high acuity, coloured perception
needed to maintain retinal images
neurons in visual system respond to change not steady input |
| how does colour vision work? | mixture of wavelengths of light that it reflects
wavelengths between 400- 700nm
2 principles- component & opponent processing |
| what is component processing? | 3 different types of cones
photopigment in each cone= responsive to short/ medium/ long wavelengths
perceived colour depends on relative activity of 3 cones |
| what is opponent processing? | neurons respond in opposite direction to commentary colours
at all levels of visual pathway NOT reactors
explains why complementary colour cannot exist together |
| what is colour blindness? | can't distinguish certain colours
results from deficiency/ absence of photopigments
often red/ green deficiencies
mainly men |
| what is the primary visual cortex? | 1st stage of visual processing
receives input from thalamus |
| what is the secondary & association visual cortex? | each composed of different areas
areas specialised for particular types of visual analysis (colour etc.)
interconnecting pathways
major streams in visual stream: dorsal & ventral system |
| what is the dorsal stream? | primary visual cortex > dorsal peristriate cortex > posterior parietal cortex
'where' stream- primarily involved in perception of where thing are
damage- possible to describe object
can't reach out & grab object |
| what is the ventral system? | primary visual cortex > ventral prestriate cortex > inferotemporal cortex
'what' stream- involved in perception of what things are |
| what are a group active neurons called? | an assembly |
| what do receptors do? | receptors with different characteristics
perception of range of different touch & pain sensations
sensory pathways |
| sensory pathway 1 | touch & position of body
axons ascend on same side of body, cross over to other side of brain stem
pathway continues to thalamus
neurons project to primary somatosensory cortex (SI) |
| sensory pathway 2 | pain & temperature
neurons cross over to contralateral side when enter spine
part of pathway continues to thalamus
other part terminates in brain stem
neurons that reach thalamus project to (SI, SII) |
| what is the SI postcentral gyrus? | somatotopy organised according to map of body surface
input from contralateral
output to secondary somatosensory (SII) & association cortex |
| what is the secondary somatosensory cortex? | input from same side & opposite side SI
output to association cortex |
| what is the association cortex? | posterior parietal lobes
input from SI & secondary somatosensory areas
extensive damage to right posterior parietal lobe= asomatognosia |
| how do we feel pain? | mild pain- glutamate
strong pain- glutamate & substance P |
| 2 pathways of pain to the brain | thalamus= somatosensory cortex pathway- conveys sensory aspects of pain
limbic system= prefrontal cortex pathway- reacts to emotion associated with pain |
| what happens in pain relief? | morphine bind to opiate receptors in CNS
opiate receptors block release of substance P= reduced pain
body produces own opiates- endorphins
endorphins inhibit release of substance P in spine
gate control theory |
