NE101 Lec 16: Somatosensation

touch, pain, temperature, and sensory pathways

The somatosensory system is important for sensing ________, ________, and ________, and for discriminating objects by texture.

temperature, pain, pressure

The Pacinian corpuscle senses ________ pressure and ________ vibration and adapts ________.

deep, fast, rapidly

The Meissner’s corpuscle senses ________ touch and ________ vibration and adapts ________.

fine, slow, rapidly

The Merkel’s disk senses ________ touch and ________ pressure and adapts ________.

fine, sustained, slowly

The Ruffini’s ending senses skin ________ and adapts ________.

stretch, slowly

Free nerve endings act as ________ for pain and temperature.

nociceptors

Mechanoreceptors have heavily ________ axons with a wide radius for fast transmission.

myelinated

Mechanosensitive means being sensitive to ________ and ________.

pressure, touch

Receptive field size refers to the area of skin that ________ a mechanoreceptor.

activates

A large receptive field means ________ acuity, while a small field means ________ acuity.

low, high

Rapidly adapting receptors respond only to the ________ and ________ of pressure.

onset, offset

Slowly adapting receptors respond ________ sustained pressure.

throughout

The best receptors for discriminating points on the skin have ________ receptive fields.

small

Two-point discrimination measures how far apart two ____ must be to be perceived as two points.

stimuli

Fine discrimination occurs in the ________, ________, and ________.

hands, fingers, face

Coarse discrimination occurs on the ________.

back

Two-point discrimination differs across the body due to differences in ________ distribution.

mechanoreceptor

Large receptive fields are found where fine discrimination is ________ needed.

not

High density of small receptive fields exists in areas needing ________ discrimination.

fine

A dermatome is the region of skin innervated by axons entering a single ________ root of the spinal cord.

dorsal

_____ is a viral infection of all neurons in a single dermatome.

shingles

Shingles symptoms are restricted to ________ dermatome.

one

Nociceptors are free nerve endings that respond to ________ stimuli.

noxious

Nociceptor cell bodies are located in the ________.

dorsal root ganglion

Pain fibers are ________ and conduct signals more ________ than touch fibers.

unmyelinated, slowly

_______ releases chemicals that bind nociceptor receptors and alter signaling.

tissue damage

Referred pain occurs when sensory neurons from internal organs synapse on the same ________ neurons as skin inputs

dorsal horn

Referred pain causes pain to be misidentified as coming from the ________.

skin

Thermoreceptors are free nerve endings that detect ________.

temperature

Each thermoreceptor expresses one type of receptor, making small skin areas more sensitive to either ________ or ________.

hot, cold

________ channels are sensitive to specific temperature ranges.

TRPV

Thermoreceptors respond best to ________ in temperature.

changes

Cold receptors increase firing when temperature ________ and decrease when it ________.

drops, rises

Warm receptors increase firing when temperature ________ and decrease when it ________.

rises, drops

First-order neurons in the touch pathway are ________ and mechanoreceptors entering via the dorsal root.

proprioceptors

Touch pathway ascends the spinal cord ________ before crossing.

ipsilaterally

Second-order neurons in the touch pathway cross in the ________ and ascend ________.

medulla, contralaterally

Third-order neurons in the touch and pain/temp pathway synapse in the ________ and project to the ________ cortex.

thalamus, primary somatosensory

First-order neurons in the pain/temp pathway are ________ and ________ entering via the dorsal root.

nociceptors, thermoreceptors

Pain and temperature pathway first order neurons ascend the spinal cord ________.

contralaterally

Second-order neurons in the pain/temp pathway ascend ________ in the spinal cord.

ipsilaterally

Somatotopy refers to how much cortical space is devoted to each ________ part.

body

Loss of limbs or digits can cause ________ of neighboring cortical areas.

reorganization

Cortical map plasticity allows remaining systems to ________ for lost functions.

compensate

Phantom limb sensations occur when the brain feels a ________ limb after stimulation elsewhere.

missing

Phantom limb may result from ________.

corticol map plasticity

String musicians show an ________ representation of digits in the somatosensory cortex

overrepresenation

what part of the skin is this?

dermis

what part of the skin is this?

epidermis

what part of the skin is this?

pacinian corpuscle

what part of the skin is this?

meissner’s corpuscle

what part of the skin is this?

merkel’s disk

what part of the skin is this?

ruffini’s ending

what part of the skin is this?

free nerve ending

All the parts of the skin except free nerve endings have______

mechanoreceptors