Somatosensory systems Flashcards
Merkle cells are located within the -____ and are specialized for
epidermis; touch
Encapsulated receptors include Meisner’s corpuscles in the dermal papilla specialized for -_____. Ruffini endings are mostly for detection of _____ and Pacinian corpuscle are very rapidly adapting and are mostly for ____
Touch; Ruffini for stretch; Pacinian for vibration.
Specialized free nerve endings wrap around hairs and detect ____; however, the sensation is not ____
light touch; not well-localized
A-alpha nerve fibers:
muscle fibers. largest in size
A-beta nerve fibers:
second largest in size. Touch, pressure, and joint proprioception
A-gamma nerve fibers:
motor to muscle fibers
A-delta nerve fibers:
mechanoreceptors and nociceptors
B nerve fibers
preganglionic sympathetics
C nerve fibers
postganglionic ANS, thermoreceptors, and nociceptors
First order neurons in the ______ have cell bodies in the ____ and ____ and connect to second order neurons in the _____ which convey the signal to the _____. Finally, third order neurons connect the thalamus to the ____ _____
Peripheral nervous system; cell bodies in the DRG and cranial nerve sensory ganglion
second order neurons in the CNS convey signals to the Thalamus.
3rd order connect to Cerebral cortex
dorsal column-medial lemniscus system
well localized, fine tactile information, as well as vibratory sense and conscious proprioceptive information from the body
anterolateral system/spinothalamic tract
pain, temperature and poorly localized, crude touch sensation. emotional responses to pain like anxiety/suffering
trigeminal mechanosensory system
fine tactile and conscious proprioception from the face
spinal trigeminal system
mediates pain, temperature and crude tactile information in the face and anterior head
dorsal spinocerebellar and cuneocerebellar tracts
unconscious information to the cerebellum
The receptors for the anterolateral system are:
nociceptors, thermoreceptors and mechanoreceptors. Type III & 4, lightly myelinated/umyelinated
Nociceptors detect ____ stimuli which is conveyed through two types of neurons: ____ for “fast” and ___ for “slow”
intense stimulation; Adelta receptors»_space; sharp, “fast” pain and C receptors for throbbing or burning “slow” pain
The TRPV1 receptor is a channel in nociceptors that responds to:
heat, acid, and capsaican
nociceptor sensitization is caused by:
they release the neurotransmitter ____ which causes:
inflammatory mediators like bradykinins and prostaglandins that lower the threshold for activation.
nociceptors release Substance P, which causes vasodilation and activates mast cells to release histamine, which further activates nociceptors.
nociceptor sensitization leads to ____ and ____
allodynia: non-painful stimuli feel painful
hyperalgesia: painful stimuli feel even more painful
What is the dorsolateral tract of Lasseur?
tract of first order neurons located at the edge of the dorsal horn and is comprised of axons of the small dorsal root ganglia neurons
In the dorsal horn, first order neurons synapse with second order dendrites in which zones?
marginal zone and lamina V, as well as substantia gelatinosa –> lamina V
second order neurons decussate in the:
anterior white commissure
second order axons from the spinothalamic tract synapse w/ third order cell bodies primarily in the:
VPL (ventral posterior lateral) nucleus of the thalamus
Cell bodies in the VPL convey information through third order neurons to the ___ _____ cortex in the ____ gyrus
primary somatosensory cortex in the post central gyrus.
Pain is represented proportional to sensitivity, which is known as:
the sensory homunculus.
what is the periaqueductal gray matter of the midbrain:
activates descending pain-modulating system using neurotransmitters like serotonin and norepinephrine
pain-suppression systems are activated by:
endogenous opiates
what is the gate control theory of pain:
large, mechanoreceptors can override pain by activating pain inhibitors
