PNS Receptors (Exam 2) Flashcards
(58 cards)
T/F: receptors in the skin, tissues, and organs are parts of neurons and therefore continuous with nerves
true
Each pair of spinal nerves supplies a strip of skin with sensory innervation and is known as a….
dermatome
Based on receptor distribution and function, they can be classified into 3 groups:
1) exteroceptors
2) interoceptors
3) proprioceptors
Exteroception is responding to stimuli in the external environment. Exteroceptors are at or near the surface of the body. There are 2 categories. What are they?
1) general cutaneous receptors (hair follicles and endings related to touch)
2) special receptors (in nose for olfaction, mouth for gustation, eye for vision, and ear for hearing)
What are interoceptors?
-receptors that respond to internal stimuli
-responds to stretch, volume, or pressure changes in the walls of viscera, blood vessels, or overstretched muscles
-also responds to pH changes and distension
-essential for regulating blood flow and pressure in the cardiovascular system
-they give info on the physiological condition of the entire body
Proprioception is our sense of awareness of the position of our appendages and body. Is it conscious or unconscious?
can be both
Proprioceptors are essential for the coordination of movements and maintenance of posture. These receptors can respond to stimuli arising in muscles, tendons, joints, and musculotendinous junctions. What cranial nerves are involved here?
CN VIII
What are the 6 classes of receptors based on modality?
1) mechanoreceptors (detects displacement, movement, or mass)
2) thermoreceptors (temp changes)
3) nociceptors (pain signals for potential damage occurring, and are also multimodal (can involve another receptor))
4) chemoreceptors (chemcial changes)
5) photoreceptors (photons/wavelength changes)
6) osmoreceptors (water changes)
note: chemoreceptors and osmoreceptors work closely together
What are the 3 categories for receptors based on structure?
1) free nerve endings (dendrites)
2) endings in hair follicles
3) terminal corpuscles of nerves
Free nerve endings are ________________ (C fibers) or ___________________ (A delta fibers) that lose myelin layers as they approach the skin
unmyelinated, finely myelinated
Endings in hair follicles are mechanoreceptors responding to any displacement of the hair. These receptors are very sensitive and rapidly adapt with low thresholds. They transmit info on light tough. Which tract does this receptor work with?
ventral/anterior spinothalamic tract
Mechanoreceptors respond to non-painful mechanical displacements or forces applied to them. What are the 4 types of mechanoreceptors?
1) musculoskeletal mechanoreceptors (within a muscle, tendon, or joints, responds to changes in muscle length or tension, or the movements of joints)
2) cutaneous mechanoreceptors
3) visceral mechanoreceptors (occur throughout the thorax, abdomen, and pelvis)
4) serosal mechanoreceptors (respond to traction on the mesentery and to compression or distension of the adjacent organs)
Thermoreceptors respond to small changes in skin temp. Thermoreceptors are _________________ and widespread across the skin. The sensations of warmth and cold are known to follow from the excitation of separate warm and cold cutaneous thermoreceptors are measured by the firing rates of the afferent nerves that form the receptors. The firing rates depend on the rate of temp change. The firing rate of the afferent nerves that serve the warm receptors increases with increasing temp while the firing rate of nerves that serve the cold sensors is reduced. The systems adapt to long-term temp changes
free nerve endings
(its harder to heat the body than it is to cool it, so cold receptors are faster than warm receptors)
Warm receptors are ____ fibers, unmyelinated afferent nerve fibers
C
Cold receptors are differentiated ______ fibers myelinated axons
A delta
There are several types of nociceptors, including thermal nociceptors, mechanical nociceptors, chemical nociceptors, and polymodal nociceptors. Noxious insults activate nociceptors and evoke pain. Pinching, pricking, or scraping the skin stimulates mechanical nociceptors. Chemical nociceptors can be surface (cutaneous) or visceral. Visceral pain results from the release of a chemical substance (___________________) from injured tissue
cytokines/ inflammatory proteins
T/F: pain is a perception
true
Chemoreceptors detect changes in the composition of solutions. What are some examples?
-Na+
-K+
-H+ (pH)
-oxygen
-CO2
What receptors are here?
-receptors for gustation are modified dendrites within the taste buds and papillae of the tongue, soft palate, and pharynx
-olfactory sensation occurs in the olfactory epithelium. The receptors are modified bipolar neurons with bulbous endings directed towards the nasal cavity where they bind chemical (odors)
-alterations in pH, oxygen tension activates carotid bodies and numerous receptors within the major arteries
-abdominal chemoreceptors in the gastric mucosa are sensitive to pH
chemoreceptors
The skin is densely innervated by a variety of sensory endings. They are divided into:
encapsulated (capsules can help modify the incoming info acting like a filter or help regulate the environment of the fluid around the endings) or nonencapsulated (free nerve endings or endings with some structures working with them but not surrounding them)
Which receptor is this?
-formed by branching terminations of sensory fibers in the skin
-interdigitated among basal epidermal cells
-have minimal or no schwann cells around their fibers
-can work as mechanoreceptors, thermoreceptors, or nociceptors
-slow adapting, high threshold
-can have C fibers (no myelin) or A delta (thin myelin)
free nerve endings
What 2 structures make a merkel disc?
merkel cell and free nerve ending
Where are merkel endings found?
-in both hairy and glabrous skin
-situated in the basal layer of the epidermis
-densely found in regions of the body requiring highly acute sensitivity like the fingertips
Are merkel endings slow or fast adapting?
slow adapting
