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Receptor Types
- Chemoreceptors
- Photoreceptors
- Mechanoreceptors
- Thermoreceptors
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Chemoreceptors
- Chemo=chemical
- Taste, smell, pain
- Blood pH
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Mechanoreceptors
- Mechanical forces
- Hearing
- Gravity/Motion (equilibrium)
- Touch/pressure
- Proprioception
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Thermoreceptors
- In skin and hypothalamus
- Increase/Decrease temperature
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How Sensation Occurs
- Sensory receptor generates nerve impulse
- Sensory neurons send input
- Cerebral cortex consciously perceives stimulus
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Skin Receptors
- Temperature receptors
- Pressure receptors
- Fine Touch Receptors
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Temperature receptors
Free nerve endings in epidermis
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Pressure receptors
- Ruffini end organs
- Pacinian corpuscles (deep in dermis)
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Fine touch Receptors
- Meissner corpuscles - in fingers the most
- Merkel disks - where epidermis and dermis meets
- Root hair plexus
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Smell
- 10-20 million cells (modified neuron)
- 1 axon and 1 dendrite do through small holes
- Axons can get ripped off
- When you get older, you need more stimuli
- 80% of taste has to do with smell
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Taste
- 5 tastes: sweet, salty, sour, bitter, umami
- Taste buds not on the surface
- Taste hairs: Microvilli; Waiting for molecule to stimulate thermoreceptors
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Eyeball Anatomy
- Sclera (white of the eye)
- Cornea (bulges out)
- Choroid (attaches to lens)
- Iris (color part of eye)
- Lens
- Ciliary body
- Pupil (black part of eye)
- Retina (yellow area - nerves)
- Optic nerve (blind spot)
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Rods
- low light
- black, white, and gray
- periphery of retina
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Cones
- more light
- blue, red, green
- center of retina
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Nearsighted
- Can see up close
- Blurry when far away
- Eyeball too long
- Need concave lens
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Farsighted
- Can't see up close
- Eyeball too short
- Need convex lens
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Photoreceptors
- Light comes in
- Dark purple in cones (synapse at the end)
- Rhodopsin pigment
- Opsin: protein
- Retinal: Vitamin A derivative
- Optic nerve leaving retina (blind spot)
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Retinal Function
- 100 million rods and cones
- 3 layers of neurons:
- 1. rods and cones (furthest from light)
- 2. bipolar neurons
- 3. ganglion cells (closest to light)
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Fovea centralis
- dark spot
- looking straight and no blind spot
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Visual cortex
attach to occipital lobe
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Middle ear
- tympanic membrane
- eustachian tube
- oval window
- round window
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Cochlear Duct
- Snail
- Bony compartment and membranous part inside
- Fluid inside
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Auditory Pathway
- Amplify sound by 20 folds
- Everything starts moving along fluid
- Hair cells in spinal cord
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Rotational Equilibrium
Related to semicircular ducts
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Gravitational equilibrium
Related to utricle and saccule
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Hair Cells & Cupola
- These are cilia (hair cells)
- Stuck in cupola
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Effects of Prolonged Spinning
- Cupola will spin at the same speed of body
- When you stop, cupola will keep spinning
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Vertical plane movement
- Mechanoreceptors in saccule
- Up and down without getting sick
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Horizontal plane movement
- Mechanoreceptors in utricle
- Side to side
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Hair Cells and Otholiths
- Like a paint brush (angled)
- Hair cells on gelatinous membrane
- Oto: hair
- Liths: stones
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Effects of Head Movement
- Stones pull on surface
- Pulling hair cells in one direction
- Increases impulses in brain
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