10. Peripheral Sensation

Somatosensation

Info from body (touch, pressure, temperature)

Somatosensation does not involve

special sensation (ex. vision)

Cutaneous

from skin (touch, nociception, temp)

Nociception

perception of tissue damage or potential damage

(often interpreted as painful)

Proprioception

awareness of extremity position w/o visual confirmation

Proprioception is primarily associated with which system?

MSK system

Which of the following regions of inputs contribute MOST directly to proprioception?

muscles/skin

tension on tendons

joint position

deep vibration

Kinesthetic Sense

movement awareness of the extremities

Light (fine or complex) touch

Vibration, skin stretch, skin pressure

Light (fine or complex) touch is also know as

discriminative (active) touch

What are the characteristics of the light touch?

easily localized, not painful

tactile discrimination is a specific kind of touch that involves

Deep sense of touch and pressure

Tactile discrimination is a ___ point discrimination.

2

Vibratory sense includes

detecting differences in materials

Stereognosis is

the ability to recognize size, shape and texture of objects by feeling them

Which sensory function is essential for stereognosis?

Spatial localization and tactile perception

Crude/coarse (simple) touch includes all of the following except

able to localize

Pain and temperature

levels of degree and change

dermatome is

an area of skin innervated by axons in a single dorsal root from DRG cell bodies

In the brachial and lumbosacral plexus, sensory axons come from

different nerves

Where do the sensory axons from different nerves converges?

in a same dorsal root

The musculocutaneous n supplies the

lateral cutaneous of the forearm

The radial n supplies the

posterior radial side of the forearm and hand

Sensory information from the body is transmitted to which two major brain regions?

Cerebrum and cerebellum

Sensory information that reaches the cerebrum is primarily used for:

Conscious awareness and behavioral responses to stimuli

Which two spinal cord afferent pathways carry sensory information to consciousness awareness?

Dorsal columns and Anterolateral tracts

Sensory information sent to the cerebellum is used primarily for:

motor control

What happens If peripheral afferent information is absent?

awareness of body parts can be lost

First-order neuron travels from

Receptor to the CNS

What type of neuron is the 1st order sensory?

peripheral (afferent)

Where is the cell body of 1st order sensory located?

in the dorsal root ganglion

What type of neuron is the first-order neuron?

pseudounipolar

The 1st order pseudounipolar neuron has a cell body that

splits into 2 axons

Ia, Ib, II, III, IV =

proprioception

Aβ, Aδ, C =

Cutaneous: Touch (all types), nociception, P&T

All sensory pathways begin with

receptors

All of the following are the correct location sensory receptors for the origin of sensory pathways except

brain and spinal cord

Sensory receptors are typically located at the _______ ends of peripheral axons

peripheral

Each sensory receptor is best described as:

A specialized end organ (free nerve ending)

Sensory receptors respond when:

a specific type of stimulus adequately stimulates the receptor

Sensory receptors can be ______ or _____ receptors

tonic; phasic

Exteroceptors are a type of sensory neuroreceptor that includes

nonciceptors, thermoreceptors, mechanoreceptors

nonciceptors

cutaneous stimuli for pain

thermoreceptors

temperature, heating, and cooling

mechanoreceptors

simple and fine touch, pressure, vibration, stretch

Which of the following neuroreceptors serves as the reflex adjustment of muscle movement and the awareness of position and movement?

prioproceptors

Statis limb position, kinesthetic position, and degree of muscle stretch are components of which neuroreceptor?

proprioceptors

Which chemoreceptor are located in viscera (carotid sinus/bodies

= O2 and CO2 levels)?

interoceptors

Special sense involves all of the following except

Gustation

The mechanoreceptor in the skin respond to

a mechanical deformation from touch, pressure, stretch, vibration

Which skin mechanoreceptor involves dynamic movement across skin,

slippage during grip?

Meissner

Which skin mechanoreceptor involves vibration?

Pacicnian corpuscle

Which skin mechanoreceptor involves skin stretch?

Ruffini corpuscle

Which skin mechanoreceptor involves light pressure, curvature, edges?

Merkel cell

Which skin mechanoreceptor involves hair movements?

hair follicles

________ are the skin thermoreceptor that respond to heat/cold.

free nerve endings

Proprioceptors are MSK somatosensery receptor that respond to

stimuli in muscle/tendon

Which MSK proprioceptors responds to muscle stretch?

muscle spindles

Which MSK proprioceptors respond to tendon/ligament tension?

Golgi tendon organs

Which MSK proprioceptors respond to extreme joint range?

Ruffini’s endings

Which MSK proprioceptors respond to movement?

Paciniform endings

Which MSK proprioceptors respond to nociception?

free nerve endings

What are the modalities perceived consciously from Skin

touch, pain, temp

touch perceived consciously from the skin includes

Simple, crude/coarse touch

Fine, discriminative touch (Pressure/Vibratory Sense)

pain perceived consciously from the skin includes

sharp pain vs dull pain

temperature perceived consciously from the skin includes

hot vs cold

FNE(cutaneous)::

Pain, temp, hair follicles

Meissner’s(cutaneous)::

Movement across skin

Merkel’s(cutaneous)::

Pressure

Pacinian(cutaneous)::

Vibration

Ruffini’s (cutaneous):

stretch of skin

Free Nerve Endings: Peritrichial hair follicle endings →

hair displacement sensation (light touch)

Free Nerve Endings: Pain to

potentially damaging stimuli

Free nerve endings:

just temperature

Meissner Corpuscles

Superficial light touch

Merkel’s Disk

Pressure sensitive

Pacinian Corpuscles

Touch and vibration

Ruffini Corpuscles

Mechanical, stretch of skin

Human skin is a mosaic of

receptor spots

Each receptor spot responds selectively to

only one modality

The response of receptors spots is always

the same no matter the stimulus type applied

Each spot is supplied by

numerous axons

The quality of sensation ________ be correlated with specific nerve endings

cannot

Sensory Receptive Fields are

the area of skin innervated by a single afferent neuron

Sensory Receptive Fields are larger ______ and smaller _______.

proximally; distally

Distal regions of the body have

a greater density of receptors

What is the sensory organ in muscle?

muscle spindles

Muscle spindles respond to (stretch)

change in muscle length and velocity of length change

Muscle Spindles are embedded in

skeletal fibers

Muscle Spindles sense

degree of muscle stretch and speed of stretch

What are muscle spindle fibers innervated by?

motor fibers

Golgi Tendon Organs

(Ib) Muscle tendon tension

Nerve ending

(III & IV) Pain

Paciniform Corpuscle

(II) Pressure, Proprioception, Vibration

Ruffini’s endinga

(II) Extreme positions

Aβ:

transmit light touch (vibration, skin stretch, skin pressure)

Aδ and C:

all skin free nerve endings (coarse touch, nociception, temperature)

I-IV:

convey musculoskeletal sensory signals

Ia and II:

muscle length

Ib:

tension in tendons