Thermoreceptors
Dendrites that detect temp. changes
Mechanoreceptors
Dendrites or cells that detect mechanical distortions of cell membranes caused by touch or pressure, stretch or bend, vibrations
Photoreceptors
Cells that detect electromagnetic stimuli (light) .location-eyes
Chemoreceptors
Dendrites or cells that detect concentration of specific chemicals. Located in nasal cavity, on papillae of tongue and mouth and pharynx
Pain receptors (nociceptors)
Dendrites stimulated mainly by chemicals released by tissue damage or inflammation, may also be stimulated by intense mechanical or thermal stimuli
General anesthesia
Complete loss of sensation and consciousness, works at a level of cerebral cortex
Local anesthesia
Loss of sensation in a localized area, blocks conduction of impulses by sensory nerves
Superficial pain
Pain sensation in skin and sub-Q tissues
Deep pain
Pain sensation in muscles, joints, bones
Visceral pain
Pain sensation in internal organs ( no pain receptors in brain)
Analgesics
Drugs that decrease pain perception
Superficial thermoreceptors
Temp sensation found in skin, consciously perceived-mainly caused behavioral changes
Central thermoreceptors
Temp sensation- hypothalamus, detects core temps. (temp of blood) controls reflexes for sweating, shivering, piloerection, and thyroid function
Proprioception
Mechanoreceptors in muscles, tendons, and joints that monitor location of body parts. Moitored by cerebellum to coordinate movements
Muscle spindle
Detects stretching of skeletal muscle, brain regulates sensitivity to control muscle tone
Tactile sensations
Mechanoreceptors in skin and sub-Q tissues that detect touch and pressure
Meissners corpuscles
Encapsulated dendrites in dermal papillae of skin detect fine touch
Hair root plexus
Dendrites wrapped around hair follicles that detect movements of hairs
Pacininan corpuscles
Ecapsulated dendrites found in many tissues detect deep pressure
Visceral sensations
Related to organ functions-chemoreceptors and mechanoreceptors-stimulate sensation of hunger, thirst nausea
Olfactory Epithelium
Sense organ for smell
Olfactory receptors
First order neurons. Bipolar neurons with one knob-shaped dendrite with olfactory cilia, cilia have one receptor for odorant molecules
Olfactory nerve
Bundled axons extending through cribriform plate. Synapse in olfactory bulbs with second-order neurons
Basal stem cells
These divide and differentiate to produce new receptors
Olfactory gland
In underlying connective tissue they secrete mucus on surface-dissolve odorant molecules
Vomeronasal Organ
Specialized olfactory organ within incisive bones of some species, may communicate with nasal cavity and mouth. Detects pheromones
Physiology of Olfaction
Odorants dissolve in mucus, odorants bind to receptors on olfactory cilia, causing stimuli, threshhold stimuli produces an action potential, which propagates along the olfactory nerve through cribriform plate
Olfactory tract
Second-order neurons running to olfactory cortex
Primary tastes
Sour, sweet, salty, bitter, and umami. Taste is augmented by olfaction and tactile sensations
Taste buds
Sense organs for taste on papillae of tongue
Taste hairs
Long microvilli with receptors for certain molecules
Taste pore
Openings in papilla; tastant molecule pass through to bind to taste hairs
Physiology of gustation
Tatsants disolve in saliva, tastants bing to and stimulate taste hairs, threshhold stimuli triggers action potential in first-order neuron. first-order neuron runs via cranial nerves 7-9-10 to brainstem, second-order neurons run brainstem to thalamus, 3rd
Nictitating membrane
Third eyelid; movement is passive
Tarsal glands
Modified sebaceous glands of eyelids, oily secretions coat nargin of eyelid, prevents eyelids from sticking together and tears spilling out of eye
Conjuctiva
Protects mucous membrane on surface of eye and inner eyelids; mucus contains lysozyme-bacteriocide
Conjuctival sac
Site for giving eye meds
Lacrimal apparatus
Moistens and protects eye
Lacrimal glands
Produce tears
Nasolacrimal duct
Drains tears into nasal cavity
Extrinsic eye muscles
move eyeballs innervated by cranial nerves 3-4-6
Cornea
Accounts for most refraction. Fibrous layer, anterior transparent portion of eye and is avascular. 3 layers, outer-startified squamous epithelium, middle-orderly layer of collagen, inner-simple sqaumous epithelium
Sclera
Fibrous layer, White of eye, dense fibrous connective tissue, gives eye rigid shape to eyeball and attachment site for extrinsic muscles
Choroid
Vascular layer, posterior portion, highly vascular-provides nutrients to retina, pigmented. Melanin-aborbes stray light. Tapetum lucidum-reflective region in some species aids vision in low light conditions
Iris
Vascular layer, anterior colored portion regulates light entering eye
Pupil
Opening in iris where light enters eye; shape varies
Circular smooth muscle
Decreases pupil diameter, parasympathetic response
Radial smooth muscle
Increases pupil diameter, sympathetic response
Ciliary body
Vascular layer, between choroid and iris, secretes aqueous humor
Ciliary muscle
Focuses lens. Contraction reduces tension on lens=lens round. Relaxation increases tension on lense=flatten lens.
Suspensory ligaments
Attaches lens to ciliary body
Nervous layer
Retina, inner layer on posterior eyeball lacation for visual receptors
Optic disc
Optic nerve and blood vessels pass through eye wall
Pigmented layer
Outer layer of retina, simple cuboidal epithelial cells containing melanin
Neural layer
Inner layer of retina, contains photoreceptors and neurons which process visual impulses before passing them to brain
Photoreceptor layer
Outer most neural layer
Rods
Part of photoreceptor layer, very sensitive to low light, black and white vision only, many in nocturnal animals
Cones
Part of photoreceptor layer, sensitive to different light wavelengths need more light for stimuli, gives sharper vision in color
Central fovea
Part of photoreceptor layer, depression in retina with high concentration of photoreceptors, area of sharpest vision, only found in some species(primates and birds)
Bipolar cell layer
Middle neural layer that adjusts to contrast of visual image
Ganglion cell layer
Inner neural layer, cell bodies of first-order neurons, axons cross retinal surface to optic disc
Lens
Transparent, avascular structure composed of layers of transparent protiens. Normally round-elasticity allows it to change shape and recoil
Cataract
Opacity of lense which obscures vision
Aqueous compartment
Anterior to lense, with a anterior and posterior chambers to iris
Aqueous humor
Watery fluid filling aqueous compartment produced by ciliary body capillaries filtering blood, circulates to anterior chamber, returns blood at the canal of Schlemm found at limbus-junction of cornea and sclera
Vitreous humor
Jelly like substance filling compartment holds retina in place
Intraocular pressure
Pressure in eye regulated by aqueous humor
Glaucoma
Eye disease characterized by increased intraocular pressure usually due to decreased drainage of aqueous humor
Photopigments
Organic molecules that absorbs light
Retinal
Vitamin A derivative that absorbs light and activates a chain of reactions that produces graded potentials
Opsins
Molecules that promote absorption of different wavelenghts of light. Rhodopsin-absorbs any visible light
Refraction
Bending of light rays as they pass through substances of differing densities
Accommodations
Focusing light rays on retina by changing curvature of lense=changing refraction
Distant vision
Parallel light rays, focus on retina relaxed ciliary muscle (20 ft or more)
Near vision
Divergent light rays require more refraction to focus image on retina contracted ciliary muscles (20ft or less)
Physiology of Vision
Stimulation of photoreceptors release neurotransmitters, bipolar cell layer integrates photoreceptor signals, Ganglion cells integrate bipolar layer signals action potentials are triggered and conducted to optic disc, Optic nerves travel to optic chiasm.
Binocular vision
Depth perception due to overlap of visual fields of right and left eyes; placement of eyes varies depending on lifestyle.
Lens
Refraction varies due to changing shape, produces inverted image on retina (reversal) and brain interpretes correct orientation