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- oriented in perpendicular planes
- filled with a jellylike substance and lined with hair cells.
sensation of the body and its movements is many senses.
detects sudden displacements of high frequency vibrations on the skin.
- limited area of the body that gets its own spinal nerve
- overlaps one third to one half of next dermatome
- Spinal nerves connect 31 dermatomes to CNS
- chemical found in hot peppers that stimulates pain receptors.
released during mild pain
released during strong pain
systems that respond to opiate drugs and similar chemicals.
periaqueductal gray area
opiates bind to receptors found here in the midbrain.
contraction of endogenous morphines.
spinal cord neurons that receive messages from pain receptors also receive input from touch receptors and from axons descending from the brain.
Vestibular organ is located close to inner ear (cochlea)
- Monitors:Direction of head tilt; Acceleration of the head
- Easier to read a sentence while you move your head than if someone else moves the sentence around
- Movement of head to right -> compensatory eye movement to the left, and vice versa
- Vestibulo-ocular reflex –
- connects vestibular organ with muscles of the eye.
- Vestibular system
- consists of 2 otolith organs
Otoliths: calcium carbonate particles, lie next to hair cells in a chamber
- Movement pushes particles against hair cell – excitation
- Chambers with patches of hair, detect motion in
- Horizontal – Utricle
- Vertical – Saccule
Central pathway: action potentials from hair cells travel through 8th cranial nerve to brainstem (pons) and cerebellum
Nausea induction: optokinetic drum; environment is moving but you aren’t, throws you off
- Located in both hairy and hairless areas of the sin
- Responds to stretch of skin, slipping of objects along skin
- Helps with finger coordination (gripping objects)
Free nerve ending
- Unmyelinated or thinly myelinated axons
- Located near base of hairs and in skin
- Sensations of pain, warmth, cold
- Can also be stimulated by chemicals
- Capsaicin (chemical in hot peppers)
Conversion of physical or chemical stimuli into bioelectrical signals, by specialized cells or sensitive endings in sense organs: “receptors”
2 pathways of pain
- sensory – to thalamus, somatosensory cortex
- emotional – to medulla, thalamus, hypothalamus
- law of specific nerve energies
- impulses in one neuron indicate light, impulses in another indicate sound.
- closest to center of eye
- receive bipolar messages
- form optic nerve
- middle layer of receptor cells
- receives input from rods and cones
tiny area specialized for acute detailed vision.
each is small and responds to just a single cone.
- more numerous than cones
- for dim light
- not in color
- more numerous in periphery or macula
- chemical that releases energy when struck by light.
- rods and cones contain photopigments.
- need bright light
- highest concentration in fovea
- color vision
- less numerous than rods
wavelengths we can see
trichromatic theory of color vision
we perceive color through the relative ratio of response by three kinds of cones
opponent process theory of color
we perceive color in terms of opposites
- cortex and retina perceive color
- cortex compares info from various parts of retina to determine the brightness and color for each atrea
- color vision deficiency
- complete color blindness is rare
- some people lack one or two of the types of cones b/c of genetics
lateral geniculate nucleus
part of the thalamus
part of the visual field that excites or inhibits a cell.
- small cell bodies and small receptive fields
- mostly in or near the fovea.
- larger cell bodies and receptive fields
- distributed evenly throughout retina.
- small cell bodies
- occur throughout retina.
ability to respond to visual info that people report not seeing.
primary visual cortex
- occipital cortex/ V1
- damage: no conscious vision, imagery, images in dreams.
secondary visual cortex, v2
processes the information further and transmits it to additional areas.
- the “what” pathway
- specialized for identifying and recognizing objects.
- the “where/how” pathway
- because it helps the motor system find and use objects.
- has a receptive field with fixed excitatory and inhibitory zones.
- response depends on angle of bar of light.