A&P Senses

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