A&P Senses

What are the 4 paths of the path for sensory impulses?

receptors, sensory neurons, sensory tracts, and sensory areas

receptors

detect changes and generate impulses

sensory neurons

transmit impulses from receptors to CNS

Sensory neurons are found in what nerves?

cranial and spinal nerves

sensory tracts

bundles of white matter in the spinal csord or brain that transmit impulses to a specific region within the brain

sensory areas

mostly found within cerebral cortex, feel and interpret sensations

projection

feeling the sensation you are sensing in the area that its receptors are located within (associating the feeling with where the receptors are located)

How does phantom presence/pain work?

nerve endings continue to generate impulses although receptors from the missing limb are gone, impulses mapped in parietal lobe and cerebral cortex generates the sensation you feel

intensity

degree to which the sensations are felt

How does the brain differentiate between weak and strong stimuli?

weak stimulates few receptors and strong stimulates many, when more receptors are stimulated more impulses are sent to the sensory regions of the brain and due to the greater number of impulses received the sensation projected is more intense

contrast

when a previous or simultaneous sensation effects current sensation due to the brain comparing things

Why does the brain become unaware of a continuing stimulus?

because the receptors detect change not presence, if stimulus is constant firing will lessen or stop

Why do after-images occur?

sensation remains in consciousness for a bit longer than the stimulus lasts

Where are cutaneous receptors located?

dermis and subQ tissue

Cutaneous receptors sense which sensations?

touch, pressure, heat, cold, itch, and paid

What types of cutaneous receptors are free nerve endings?

temperature receptors, nociceptors, and Merkel’s discs

Nociceptors

receptors for pain, some enter the epidermis

Merkel’s discs

slow receptors for light touch

What types of cutaneous receptors use encapsulated nerve endings?

Pacinian, Meissner’s, and Ruffini’s corpuscles

Pacinian corpuscles aka

Lamellar corpuscles

Pacinian corpuscles

fast receptors for deep pressure/touch and high frequency vibrations

Meissner’s corpuscles

fast receptors for light pressure/fine touch and low frequency vibrations

Ruffini’s corpuscles

slow receptors for vibrations and skin stretching

chemical itch

caused by an irritant (ex. poison ivy sap, mosquito saliva) that triggers the release of Histamine in the skin which causes inflammation and itching

mechanical itch

caused by slight movement of smth against the skin (ex. coarse fabric against the skin, flea) that can be relieved by removing the external irritant or distracting the brain from the impulse

Why does scratching relieve the discomfort of a mechanical itch?

it causes more pain than the itch itself and distracts the brain

Pathologic itching is found in patients with what diseases?

liver or kidney disease, certain cancers, HIV/AIDS

pathologic itching

unrelenting itchiness that disrupts sleep and normal activities
no known cause, no satisfactory tx

What is referred pain?

when pain is project to a cutaneous area of the body when the actual problem is visceral

Why does cutaneous pain occur?

the sensory tracts within the spinal cord are shared by cutaneous and visceral receptors and the cutaneous receptors fire much more frequently, the brain projects based on past experiences so it sometimes projects cutaneous sensation for a visceral feeling

Pain of a heart attack may be found in where?

left arm/shoulder

Pain of gallstones can be felt where?

right shoulder

Where can the pain at appendix first be felt?

at the umbilicus

muscle sense aka (2)

proprioception, kinesthetic sense

stretch receptors aka (2)

proprioceptors, muscle spindles

What do stretch receptors do?

detect stretching muscles and send impulses that let the brain create a mental picture to know how muscles and the body’s positioned

Where in the brain is conscious muscle sense felt?

parietal lobes

Where in the brain is unconscious muscle sense used?

cerebellum (to coordinate voluntary movements)

Where are taste buds located?

on papillae (which are on the tongue)

chemoreceptors

detect chemicals in soln (ex. saliva)

What happens when your mouth is dry?

decreased ability to taste the food since theres no saliva (solvent) to dissolve the chemicals

What nerves send taste bud impulses and where in the brain do they go?

CN 7&9, (gustatory area of) parietal-temporal cortex

Explain the process of smell.

1. chemoreceptors within the wall of nasal cavity get stimulated by vaporized chemicals

2. send impulses through olfactory nerves that travel thru the cribiform plate of the ethmoid bone

3. impulses synapse at the olfactory bulb (which sits on top of the cribiform plate)

   1. impulses then sent thru the olfactory tracts to the olfactory cortex (temporal lobes)

hunger and thirst

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