Module 7: Sensory System pt.1 Flashcards
what are the 4 sensory systems
Somatosensory (touch)
Visual
Olfactory (smell)
Gustatory (taste)
Transduction of environmental information
how info from the external envirponment is communicated to the brain (action potentials!)
Environmental stimuli
things like heat, light, touch or sound
different types of sensory receptors
mechanical
chemical
light
gravity and motion
all produce action potentials
Adequate stimulus
specific env. Stimulys the sensory receptor is most sensetive to
receptor (generator) potentials similarities to EPSPs
Depolarizing but can be hyperpolarizing
Caused by ^ permeability to Na+ ot K+ ions
Local (don’t propogate)
- Decrease with time and distance
Proportional to stimulus strength
- Larger receptor more likely to fire an AP
the somatosensory systemdetects
Tough
Vibration
Temperature
Pain
cutaneous receptors types
Receptors in skin = cutaneous receptors
hair follicle free nerve endings meissner's corpuscles ruffini's corpuscles pacinian corpuscles
hair follicle stimuli
Fine touch
vibration
Free nerve endings
pain
temp
Meissner’s corpuscles
Low frequency vibrations (30-40 cycles/s)
Touch
Ruffini’s corpuscles
touch
Pacinian corpuscles
High frequency vibrations (250-300 cycles/sec)
Touch
receptive field
Stimuli has to be in range
the spinothalamic (anterolateral) tract
Pain, temp, crude touch
First order neuron = sensory neuron sends info to
Spinal cord (synapse with second order neuron)
Second order neuron crosses to opposite side and ascends to
Thalamus (relay station) meets second synapse with third order neuron travel to somatosensory cortex
dorsal comumn, medial lemniscal system
Fine touch, proprioception (muscle sense), vibration
…see steps in pic on notes
primary somatosensory cortex
In parietal lobe
On postcentral gyrus
Behind central sulcus
primary somatosensory cortex – the somatosensory homunculus
see pic - it is like a map of brain correspondance withbody parts
Some are larger than others (seem unproportianate)
Hand, tongue, lips most sensetive so they contain many more sensory receptors than any other body parts
visual system
Detect light, convert to AP, send to primary visual areas for processing
Consisnts of: eye (contains photoreceptors that convery light to AP), visual pathway (transmit APs) & primary visual area (in occipital lobe)
the eye makes pictures how
- light pass through cornea
- amount of light is regulated by iris (constrict when bright or dilate when low light)
- Lens flips
parts of eye
cornea
lens
iris
fovea
optic nerve
retina
rod cells
Sensetive to light
Function best in low light
One type potopigment (chemical sensetive to light) - Threfore cannot detect color
Located: outside and around the fovea
cone cells
Function best in bright light
Detect detail
3 types, each with different photopigment and each sensetive to one primary color
both rod cells and cone cells
No axons, no APs
Generate receptor potentials
- Release inhibitory neurotransmitter
when there is no light rod and cone cells
release inhibitory neurotransmitters
- Depolarized
- Na+ flows into photoreceptors
when there is light cone and rod cells
shut off
- Hyperpolarize
- Na+ channels shut down
types of eye movement
saccades
smooth pursuit
vestibular ocular reflex (VOR)
vergences
saccades
Rapid jerky
Look around to object of interest
Ex, looking around room
smooth pursuit
Smooth movement to keep things in focus
Ex, following flight of bird through sky while keeping head still
Vestibular ocular reflex (VOR)
Focus and then move head
Ex, nodding while agreeing or disagreeing with someone
vergences
When something is moving away or closer
Diverge – moving away
Converge – moving forward
Ex, pencil moving away or closer
