Chapter 10 Peripheral Somatosensory System & start of 11 Flashcards
how do we investigate the world
through light and touch to move accurately and avoid injury and harm
how do superficial and deep sensory receptors work
they tell us about touch and movement. all send their axons in toward spinal cord, past spinal cord and to peripheral somatosensory cells and goes into the CNS
where are somatosensory cells located
in dorsal root ganglion, pseudounipolar
surface receptors pick up
touch, nocioception, and temperature
deep recptors detect
proprioception and nociception
from receptor to brain there are generally
three neurons with three pathways
first order neuron is
pseudounipolar
mechanoreceptors
mechanical stimuli (ligand modality gate) can depolarize peripheral sensory axons they are high threshold nociceptors.
a high threshold nocipcetor is
it takes a big stimulus before they send the signal
chemoreceptors
detect chemical stimuli that can harm us
high threshold
thermoceptors
same
tonic receptors
maintain signaling as long as there’s a stimulus–touching shoulder. they don’t adapt to stimulus, they stay active
phasic receptors
fast acting, respond to change (hand on shoulder and then removed
how are first order neurons classified
axon diameter
Scheme 1
Ia, Ib, II, III, IV
the firster the number or letter the bigger the diameter neuron
Scheme 2
A-beta, A-delta, and C
receptive fields are smallest….
in hands feet and around corners of mouth
what is a receptive field
area of skin that is innervated by one peripheral sensory axon and all its terminal branches
receptive fields are greater where
proximally, core, hips, and shoulder
where are there more sensory axons
distally than proximally
light or discriminative touch travels on
A-beta
superficial discriminative touch can detect…
touch, vibration, pressure, hair movement, and stretch
superficial are located
right at skin or under surface of skin. all are class A-beta (peripheral sensory axons that carry message of discriminative touch in CNS)
Coarse touch travels on
a-delta and C
they are axons with
no terminal branches but no specialized receptors
free nerve ending (coarse touch) can detect
touch, pain, and temperature
what is coarse touch
can’t describe the touch well or locate it well
Nociception travels on
A-delta and C
there are free nerve endings with nocipcetion where…
under skin that are sensitive to pain (mechanical stimulation) that carry message of pain
temperature…
same as nociception card and travel on A-delta and C
neurons of peripheral travel on
a-delta and c
peripheral nerves have a different distribution than dermatomal innervation
yeahhhh
look over slide 13
how do the spinal and peripheral mix at plexus
mix at plexus on way down from spinal to peripheral but in sensory system the plexus unmixed peripheral into spinal nerve
are named peripheral patterns different than dermatome patterns?
yes
what is a muscle spindle?
a sensory deep in muscle
muscle spindle tells central neurons two things
length of muscle (stretch or unstretched)
how fast the length is changing
what is the shape
fusiform
intrasfusal and extrafusal
inside the spindle and outside the spindle
slide 19 shows how the spindles are physically oriented
neat
nuclear bag fibers (mechanoreceptors)
bulging in picture
detect the rate of change of length
nuclear chain fibers (mechanoreceptors)
how long it is
together the nuclear bag and nuclear chain tell you
tell brain the length of muscle and if it’s changing and how fast it’s changing
two types of axons that take messages from the spindle
primary and secondary
primary (Sensory endings)
AP on Ia (biggest and fastest)
Ia pick up from the bulge and skin so it says length and rate of change. messages come from middles of both bulges
secondary (sensory) neurons
AP on II (thinner blue line)
send messages just from the chain and maller sensory, so just a confirmatory message of length
even at rest, they are constantly sending AP
when it gets stretch the number of AP goes
up
when it gets unstretched, number of AP goes
down
Associated motor neurons
A-alpha, A-gmma
A-alpha
contracts extrafusal muscles (outside the spindle and fibers of muscle contraction)
shortens the muscle overall
A-gamme
travels from spinal cord out to the muscle spindle and make little muscle of the spindle contract
when A-gammes are active they don’t cause you to contract but they contract the spindle so it keeps the spindle sensitive to stretch throughout movement
goldi tendon organs
job is to sense tension in the tendon
tension is due to active contraction
passive stretch gives brain info about stretch on a muscle tendon on a unit
what sensory neuron do goldi tendon organs tranmist on
Ib
overall golgi tendon organs do what
send messages of tension and stretch which influence movement
joint receptors
specialized capsule receptors and those help with position and movement of joint
specialized capsule receptors transmit on which sensory neurons
II
ligament receptors transmit on which sensory neuron
Ib
ligament receptors
ligaments all have mechanoreceptors that help with tension on the ligament suppporting a joint
free nerve endings transmit on which sensory neurons
A-delta and C
free nerve endings
trandsduce pain and inflammation… any damage to stimuli and any inflammation from injury
free nerve endings send their messages where
into the nervous system
large diameter axons
myelinated… this includes muscles, tendons, and joints
muscles, tendons and joints transmit info on which sensory neurons
Ia,Ib
medium diamter axons are
myelinated
medium diamater include
muscle spindles and specialized cutaneous receptors
muscle spindles and specialized cutaneous receptors transmit info on which sensory neurons
II (muscle spindle) and A-beta (specialized cutaneous receptors)
small diameter axons are
myelinated
an example of a small diameter axon includes a ______ and transmits info on which sensory neurons
free nerve endings
A-delta
another small diameter axon is also
unmyelinated
an example is and transmits info on which sensory neuron
free nerve endings and C
Sensory loss with compression
Conscious proprioception and light touch Cold Fast nociception (“sharp, stinging” pain) Heat Slow nociception (“dull, aching” pain)
sensation returns how
reverse order
list
When a patient reports extra signs or symptoms (tingling in an extremity)
extra almost always means irritation of the nervous system
reminder
Ataxia (incoordination not due to weakness) can effect
Sensory
Cerebellar
Vestibular
research how. i think you know
some messages of sensation go to
conscious awareness
conscious awareness of sensation can classify
hurt and where you got hurt
what does conscious mean
cerebral cortex
parietal lobe=somatosensation
somatosensory signals are also located in the
cerebellum
cerebellum is
autonomic and the signals are not conscious
somatosensory signals can also go to
emotional and autonomic areas
emotional and autonomic areas have a
high degree of conscious awareness but DONT go to cortex
when hurt goes to the emotional part your heart rate
goes up to maintain homeostasis
conscious relay is located in
cerebral cortex
divergent pathways means
two routes for sensory signals
there are many divergent pathways in the
brain stem and cerebellum
divergent pathways can be
conscious and unconscious
nonconscious relay is located in
cerebellum
high fidelity pathway
high degree of body map organization
parietal lobe is high fidelity
part of brain devoted to a part of the body is either _______
bigger or smaller depending on density of sensory receptors to that body part
if the middle cerebral artery was impacted there would be more defecits to
the arm
low fidelity pathways
low degree of body map organization
example: spino-emotional pain (divergent pathways that don’t go all the way to cerebral cortex)
projection neurons
(neurons in pathways)
1st in pathway and 1st order
peripheral and pseudounipolar
spinothalamic
2nd neuron and in pathway
start and end is in the name but ultimately ends in cerebral cortex
interneurons
can be interspursed through any of synapses
synapses
spot in any sensory pathway where signal can be turned up or down or spread out or gathered
interneurons between the green and blue
interneuron inhibits pain pathway, turns down signal in pain pathway and can only be turned on at the synapse
