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Substance P

What 11-amino acid peptide is the neurotransmitter of sensory neurons that conveys pain from the periphery to the spinal cord?


A chain of 9 amino acids that causes histamine-like effects such as vasodilation, contraction of non-vascular smooth muscle, and an increase in capillary permeability.


"morphine within"--natural, opiatelike neurotransmitters linked to pain control and to pleasure.


an involuntary, constant, rhythmic movement of the eyeball that can be congenital or caused by a neurological injury or drug use

tonic receptors

are always sending signals to the CNS; phasic receptors become active only when the conditions that they monitor change.

phasic receptors

Receptors that rapidly adapt to stimulus, therefore the receptor will dim the stimulus as long as the stimulus remains contant.


Sensory receptors, located in the muscles and joints, that provide information about body position and movement.

free nerve endings

bare dendrites associated with pain, thermal, tickle, itch and some touch sensations.


respond to a variety of stimuli usually associated with tissue damage. Two types of painful sensations: fast (prickling); pain and slow (burning and aching) pain.

hair receptors.

unencapulated, free nerve endings that wrap basketlike around hair follicles functioning as light touch receptors that detect bending hairs

tactile corpuscles.

small, oval masses of flattened connective tissue cells within connective tissue sheaths. Two or more sensory nerve fibers branch into each corpuscle and end within it as tiny knobs. Abundant in hairless portions of skin. Respond to the motion of objects that barely contact the skin. Associated with the sensation of light touch.


respond to water-soluble and lipid-soluble substances that are dissolved in the surrounding fluid. They monitor the chemical composition of body fluids


respond to pressure changes in the walls of blood vessels and digestive, reproductive, and urinary tracts.

Krause's end bulbs

A form of Meissners corpuscle adapted for fine touch.

tactile (Merkel) discs

[unencapsulated Nerve endings] tonic receptors for light touch thought to sense textures edges and shapes. Are flattened n. ending that terminate adj. to specialized cells.

Ruffini corpuscles

Heavy touch, pressure, stretching of skin, and joint movements

laminated corpuscles

Deep pressure and vibration are detected by cutaneous sense organs called________, which have onion-like layers of connective tissue around a central sensory dendrite.

receptor field size

Inversely related receptor density, is the size that a single neuron can gather information from. to very small in fingertips and high in back

receptor types

photoreceptor (vision), chemoreceptors (taste, smell), thermoreceptors (hot, cold), mechanoreceptors (touch, stretch, proptio, sound), nocioceptors (pain)

first order neuron

coducts impulses from cutanious receptors and perpial ceptors. They branch diffusely when they enter the spinal cord or the medulla. They synapes with second order neurons

second order neuron

conducts impulse from brainstem or spinal cord to thalamus. thalmus relays info to appropriate area of brain. these are the neurons that cross over before enterint thalamus

third order neuron

originate in thalamus, terminate in parietal lobe of the cerebrum, specifically the post-central gyrus

somesthetic senses

receptors widely distributed in skin, muscles, tendons, joint capsules, and viscera; covers most everyday (conscious) senses as well as blood pressure and composition

diffuse pain

burning or aching pain resulting from action potentials that are propagated more slowly

localized pain

pain in one area that gets worse with movement/touch

referred pain

when pain seems to be coming from somewhere else; some organs and structures share a common nerve pathway; because of the the cerebral cortex may misinsinterpret the source of the pain (pain from heart referred to the the left shoulder or arm)

visceral pain

usually diffuse, vague. closely connected to ANS; thus associated with pallor, sweating, nausea, vomiting

somatic pain

body's warning system that something is being or is about to be damaged and tends to be sharp and fast. skin, muscles, tendons, and joints.

phantom pain

Perceived sensation of pain from an amputated limb; over activity of the dorsal horn neurons on the side of the amputated limb may create a false feeling that the pain is emanating from the amputated limb.

taste sensations

there are four primary: sweet, bitter, salty, and sour; and a possible fifth, MSG (mono-sodium glutamate); gustatory receptors most sensitive to sweet and salty sensations are found on the tip of the tongue, while bitter sensation are in the back and sour sensations are on the sides of the tongue; other taste sensations are a mixture of these four; smell, temperature, and texture (tactile sensation) contribute to our sense of taste

gustatory nucleus

-where the cranial nerves synapse in the Dorsal Medulla
-Neurons from THIS nucleus then synapse in the Ventral Posterior Medial Nucleus (VPM) of the thalamus
-from there, the VPM sends sensory info to the Primary Gustatory Cortex in the ventral parietal lobe

sense of smell

1) Olfactory epithelium of nasal cavity responsible for chemoreceptors 2) epithelium has ciliated cells that respond to odors and lick directly with brain via olfactory nerve 3) Olfactory cortex is located in limbic system with emotion

olfactory cells.

sensory receptors for smell, constantly replaced every 30 to 60 days. when stimulated by airborne molecules, the stimulation gets passed to its axons which bundle to create the olfactory nerve


light sensitive cells (rods and cones) that convert light to electrochemical impulses


retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond


retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations.


Is the opsin in cones. There are 3 types of photopsin that have different sensitivities to different wavelengths of light.


A visual pigment consisting of retinal and opsin. When rhodopsin absorbs light, the retinal changes shape and dissociates from the opsin, after which it is converted back to its original form.

peripheral vision

Ability to see objects as they come into the outer edges of the visual field.

visual accommodation

the ability of the lens of the eye to change shape to bring objects at different distances into focus.


(physiology) the automatic adjustment in focal length of the lens of the eye


The bending of a wave as it passes at an angle from one medium to another


nearsightedness; difficulty seeing distant objects when light rays fall short of the proper focus on the retina


visual impairment in which an object is seen as two objects

lacrimal glands

located on the underside of the upper eyelid just above the outer corner of each eye; secretes lacrimal fluid (tears)

consensual light reflex

when light is shown into one eye and the pupil constricts in the same eye and the other eye; abnormal finding indicates problem with cranial nerve II

sclera venous sinus

the vascular structure encircling the anterior chamber of the eye and through which the aqueous humor is returned to the blood circulation.

fibrous tunics of the eye.

Vascular, choroid and retina

what is the path light travels through the eye and where is it most refracted?

Light passes through the cornea, the aqueous humour, the pupil (which is just an opening in the iris), the lens, and the vitreous humour on its path through the eye to the retina. it is most refracted at the vitreous humour

depolarization of rods and cones

___________(causing release of their neurotransmitter) occurs because in the dark, cells have a relatively high concentration of cyclic guanosine 3'-5'. monophosphate (cGMP), which opens ion channels (largely sodium channels, though calcium can enter through these channels as well).

Cones, Rods

___are more sensitive to light, while _____can differentiate between wavelengths of light.


specialized mucosa; threadlike karatinzed elevations that cover the dorsal surface of the tongue. most numerous of the papillae


specialized mucosa; vertical grooves on the lateral posterior sides of the tongue, also contain taste buds


specialized mucosa; mushroom shaped papillae interspersed among the filiform papillae on the tip and sides of the tongue. appear redder and contain tastebuds


_______papillae are the largest and least numerous papillae; 7-12 7-12 of these form an inverted 'V' at the back of the tongue.

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