PNS Receptors (Exam 2) Flashcards
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
What info do merkel endings transmit?
fine touch
The merkel disc is sensitive to displacement of the skin which we perceive as pressure. The merkel cell can release….
neurotransmitters
Nerve endings around hairs are referred to as hair follicle receptors. Moving or bending a hair distorts the receptors ending wrapped around the hair follicle and generates a potential. These mechanoreceptors respond to any displacement of the hair. They serve as receptors for….
light touch and direction
What is another name for pacinian corpuscles?
lamellar corpuscles (of pacini)
Which receptors are almost as common/widespread as free nerve endings?
pacinian corpuscles/lamellar corpuscles (of pacini)
Which receptor is this?
-large, ovoid mechanoreceptors
-found subcutaneously over the entire body and in numerous other connective tissue sites
-they are wrapped layers of corpuscle (up tp 70 layers and looks like an onion in a cross section)
-quickly applied forces are transmitted through the interior of the capsule and reaches the ending, but maintained forces are not
-vibratory stimuli causes a steady train of impulses
-they need a strong stimuli to be activated
-found between the dermis and subcutaneous tissue of the palm, fingers, and soles
-in CT near tendons and joints
-membranes of limbs, muscles, and bones, breast, penis, and clitoris
-also in human middle ear and related to all 3 ossicles
pacinian corpuscles/lamellar corpuscles (of pacini)
Which receptors are for gripping and allow for skilled movements?
meissner corpuscle
What is another name for meissner corpuscle?
tactile corpuscle of meissner
Are meissner corpuscles encapsulated or nonencapsulated?
encapsulated (thin outer capsule and a layered stack of schwann cells)
Where are meissner corpuscles found?
in the palm of hand, tips of fingers, forearms, lips, and big toe
Each meissner corpuscle is in a _______________ (hairless skin) just beneath the dermis
dermal papilla
Which receptors project perpendicular to the surface of the skin and are there for discriminative touch?
meissner corpuscle
Are meissner corpuscles slow or rapid adapting?
rapid adapting
As meissners corpuscles respond to light touch they are only found in the glabrous skin in areas of the body that requires highly acute sensation such as the eyelids and fingertips. What cranial nerve is involved here?
CN V
What size are the receptive fields for meissners corpuscles?
small (so the touch is localized)
Which receptors run parallel to the skin?
corpuscles of ruffini
What are the other names for corpuscles of ruffini?
ruffini endings or bulbous corpuscle
The corpuscles of ruffini are dermal receptors with a thin capsule and a large subcapsular space. Anatomically, they are enlarged dendritic endings with _____________________
elongated capsules
Where are corpuscles of ruffini found?
in hairy and hairless (glabrous) skin and deep fascia, capsules of joints, ligaments, tendons, and fibrous sheaths of flexor tendons
corpuscles of ruffini are mechanoreceptors that provide info about…..
direction, magnitude, and rate of change of tension in skin (respond to stretching of skin, pressure, and joint movement)
Do corpuscles of ruffini adapt slowly or rapidly?
slowly
T/F: the sensation of discriminative touch varies in different parts of the body
true
the larger the receptive field=
the more general the perception is
smaller receptive field= more localized
What does adaptation mean in sensory pathways?
receptor becomes less sensitive and less APs are transmitted (less info from receptor)
Slow adapting receptors are used for….
static position
(rapidly adapting receptors help indicate change and movement of a stimulus. Some are so quick to adapt they only signal and the start and end of a stimulus ex: pacinian corpuscles)
How many receptors are present in the human hand? What are they?
4
1) meissner corpuscle (superfical layer)
2) merkel ending (superfical layer)
3) pacinian corpuscle (deep layer)
4) ruffini corpuscle (deep layer)
(receptors in superficial layer have many fibers that innervate 1 receptor, whereas the deep layer has 1 fiber per receptor)
The deeper the receptor =
the larger the receptive field (generalized, not localized)
T/F: rapidly adapting receptors stop responding to a constant stimulus
true
What is a ganglion (pleural- ganglia)?
group of neuronal cell bodies found outside of the CNS along with some glial cells and CT
What info is conveyed by DRG neurons (pseudounipolar cells)?
somatosensory info
-the transduction and encoding of stimuli into electrical signals (APs)
-transmission of these signals to the CNS
What is the axon of a pseudounipolar neuron called?
primary afferent fiber
Which receptors are for touch and proprioception with a large diameter, myelinated axons, and rapid APs?
mechanoreceptors
Which 3 receptors have small diameter axons, are unmyelinated or are thinly myelinated, and have slow APs?
thermoreceptors, nociceptors, and chemoreceptors
Which nerve innervates the skin of the hand and some of the muscles that moves the hand?
median n.
