Topic 5: Sensation and perception (visual) Flashcards
The basics of sensation
the patterns of stimulation from external world, the energy is converted from external world into neural patterns
Muller
specific nerve energies, different inputs for different sensory organs
the senses (8)
touch/somatosensation olfaction vision hearing audtiion
proprioception (location and movement of the body)
vestibular (balance)
interoception (hunger, oxygen, blood vessels, throat)
sensory integration
essential to all sensation, this is how we experience the world, senses influence each other
we also need sensorimotor information integrating motor movements with the external world
The brain broadly
the back is senosry inputs mainly and the front is mainly motor outputs
8 steps general principles of sensory system
1 - transduction (energy converted)
2 - receptive fields (ganglion cells)
3 - sensory pathways
4 - parallel pathways supplementary information
5/6 - in our cortex, multiple topographic representations
7 - association areas of the cortex
8 - descending tracts send info back out into motor movement
electromagnetic waves
put the GravoX under U V for Indian Ramen
tiniest waves (0-0.1) = gamma rays (0.1-10) = x rays (10-300)= ultra violet rays (300nm - 760nm) = visible light (1000-1000000) = infrared rays (1mil- upto mega trillions)= radio
Visual system - transduction
physical energy converted into a RECEPTOR MEMBRANE POTENTIAL
IRIS PUPIL CORNEA LENS CILLIARY MUSCLE RETINA FOVEA RODS AND CONES BLIND SPOT OPTIC NERVE
IRIS: coloured part
PUPIL: gap in iris
CORNEA: clear cap over iris
LENS: ovular disk behind pupil flips image
CILLIARY MUSCLE:controls how taught the lens is
RETINA: back of eye ball
FOVEA: central point of focus for accute detailed vision. spot at back of retina
RODS AND CONES: the makeup of the retina
BLIND SPOT spot over optic nerve where no retina can be, where blood vessels are
OPTIC NERVE: at back and slightly down of reina
cells in the retina
photoreceptor cells: at the back of the eye, light goes through the bipolar and ganglion to be picked up by the photoreceptos (and then transmitted back inwards, then from ganglion to optic nerve backwards again into the optic nerve
bipolar cells&ganglion receptors are clear so light can pass through
horizontal cells transmit laterally between bipolar cells
amacrine cells transmit laterally between ganglion cells
photo-receptors
RODS AND CONES
cells with the rod or cone shape
rods 120million, in the periphery of the retina, sensitive to 400-600nm black white and grey e.g. night visions
cones 6 million, exclusively in the fovea, maximsed for bright light sensitive to restricted wavelengths (colour vision) for accute detailed vision. each cones has its own ganglion 9microganglion) whereas many rods go to one ganglion (less detailed vision)
TRI-CHROMATIC THEORY 3 cones blue 380-500 green 430 -640 red 470-760
the pattern of activation of the three cones determines different colours seen
neuroscience of photoreceptor activation
opsin
rodopsin and coneopsin
retinal (lipid fat)
they are depolarised by DARK;
cyclic guanosine monophosphate (cGMP) is activated in dark, keeping sodium and potassium ion channels open, which create continuous depolarisations and transmission of glutamate neurotransmitter
they are hyperpolarised (Inhibited) by light! reducing their activity;
light hits the photorecpetor,
when light hits the 11 cis retinal, it is converted to all trans retinal
energy from this conversion activates opsin proteins which DESTROYS the cGMP, so channels close, hyperpolerisation occurs no more glutamate (energy intensive process, to make new 11 cis retinal)
the message goes to bipolar cells whihc have on and off centres, responding to light or dark, and then these bipolar cells influence ganglion rate of firing
visual pathways
all senses go receptor to receptive fields to thalamus to the sensory cortex (except smell)
PRIMARY VISUAL PATHWAY
