somatosensory system Flashcards
sensitivity to stimuli interacting with ones body (touch temp pain)
exteroception
ability to sense position, location and orientation
proprioception
stimuli originating from inside body
interoception
information from ___ is carried by dorsal root ganglia and spinal cord
trunk
information from ___ is carried by cranial nerves
face and head
dorsal root ganglia contain __ ___ __ that innervate skin, muscles, joints and organs
neuronal cell bodies
___ ___ of nerve fibers (DRG) involved in touch are encapsulated by special end organs
peripheral process
DRG neurons are
pseudounipolar
information carried by DRG enters in ___ spinal cord in each of the regions
dorsal
receptor type and fiber which carries proprioception
muscle spindle, and Ia, II (large and well myelinated); fast
receptor type and fiber which carries touch
merkel, meissner and ruffini cells (end organs), A beta (well myelinated not as big)
receptor type and fiber which carries pain and temperature
free nerve endings, A delta
receptor type and fiber which carries pain, temp, itch
free nerve endings, C fibers (smallest and unmyelinated)
cell that responds to mechanical stimulus
mechanoreceptors
the nerve endings of mechanoreceptors respond to stimulus by
stretching (as plasma membrane stretches it opens Na channels –> depolarization)
depolarizing potenial that accomponies stimulation of a sensory nerve (varies according to strength of stimulus)
receptor potential
part of a sensory field that can elicit neuronal responses when stimulated (each neuron has one but size and freq. can be different)
receptive field
decline of electrical response in a receptor cell over time, even thouhg stimulus id still present
adaptation
in the glaborous skin receptors (very sensitive skin) have
free nerve endings (no end organs)
small receptive fields near surface of skin that tracks motion; rapidly adapting
meissner corpuscle
small receptive fields near surface of skin that tracks shape and texture; slowly adapting
merkel cell
large receptive fields deeper in skin that tracks skin stretch; slowly adapting
ruffini corpuscle
large receptive fields deeper in skin that tracks skin vibration; rapidly adapting
pacinian corpuscle
the layers of the pacinian corpuscle get depressed and after a certain point stop ____
responding
superficial receptors
merkels and meissners
deep receptors; distributed more evenly throughout hand
ruffini and pacinian
type of hair follicle: longest, nerve fibers form touch domes and circumferential nerve endings
guard
type of hair follicle: longitudinal lanceolate endings
awl
type of hair follicle: circumferential and longitudinal endings
zigzag
innervation arising from one DRG and its spinal nerve
dermatome
2 types of muscle fibers
extrafusal and intrafusal
muscle fibers that contract and do the work
extrafusal
muscle fibers that detect stretch and dont contract
intrafusal
each ____ muscle fiber is innervated
intrafusal
____ ___ ___ signal changes in muscle lenght by muscle tension and correlation with muscle spindle
golgi tendon organ
the golgi tendon organ activates when __ ___ contract
extrafusal fibers
the __ neurons innervate golgi tendon and synspase on interneurons
Ib
_____ fibers enter into dorsal spinal cord
mechanosensitive
one branch of dorsal column synapses onto motor neuron and interneurons; other branch travels in the dorsal columns to ____
medulla
the dorsal column pathway decussates and then synapses at the ____
medulla
the dorsal column pathway finally hits the thalamus VPL then to
primary somatosensory cortex
major cranial nerves involved in ____ and pain is the ___ nerve
mechanoreception; trigeminal
the cranial nerves make synapses at ____ of the trigeminal complexes
nucleus
after it synapses it goes to the ___ of the thalamus and primary somatosensory
VPM
representation of body and face
somatopic
sensory cortices and thalamus are organized into ____ in the mammalian brain
modules
