Module #2 : General Somatosensory System

Reception -\> Transduction -\> Transmission -\> Perception

General Principles: Sensory Process:

Reception

Sensory Process: action that takes place in the sensory cells

Transduction

Sensory Process: conversion of the stimulus into an electrical response (receptors potential, graded response: action potentials)

Transmission

Sensory Process: takes place in the synapse where the connection between the nerves and neurons

Perception

Sensory Process: processing of information in our complex network, which is governed by our CNS

SOMATOSENSORY SYSTEM

Part of the sensory system concerned with the conscious perception of touch, pressure, pain, temperature, position, movement, and vibration

all major parts of our body

SOMATOSENSORY SYSTEM: Distributed throughout \______

periphery, deeper

SOMATOSENSORY SYSTEM: Includes both sensory receptor neurons in the \______ (e.g., skin, muscle, and organs) and \___ neurons within the CNS

SOMATIC SENSES

nervous mechanisms that collect sensory information from all over the body

Mechanoreceptors of hearing (hair cells), Photoreceptors, Chemoreceptors: taste & smell

SPECIAL SENSES

MECHANORECEPTORS

Type of Sensory Receptor: Responds to mechanical stimuli such as touch, pressure, and vibration (mechanical displacement of the nerve endings)

Free nerve endings

Types of Mechanoreceptors: Non- encapsulated, Skin (epidermis and dermis), Slow, Light touch and pressure

Meissner's Corpuscles

Types of Mechanoreceptors: Elongated Encapsulated, Glabrous Skin, Rapid, Fine touch, Dynamic Pressure

Merkel’s Discs

Types of Mechanoreceptors: Tactile discs, Non- Encapsulated, Glabrous skin, basal epidermis, Slow, Discriminative touch, static pressure

Ruffini’s Corpuscles

Types of Mechanoreceptors: Multi- branched, Encapsulated, Deeper layers of the skin, tissues, and joints, Slow, Pressure, Stretch, and Torque

Pacinian Corpuscles

Types of Mechanoreceptors: Encapsulated, Dermis and Hypodermis, Rapid, Deep pressure and vibration

Hair Follicle Receptors

Types of Mechanoreceptors: Non - Encapsulated,Free, Base of Hair Follicle, Rapid, Bending of hair

discriminative and crude

Sense of touch can be divided into \____ \__ \____ types

Discriminative touch

Sense of touch: fine touch

Crude touch

Sense of touch: non discriminative touch

PROPRIOCEPTORS

Type of sensory receptors: Transmit sensory information from muscles, tendons, and joints; awareness of body position in space; helps provide cues

muscle spindles, golgi tendon organs, vestibular system

PROPRIOCEPTORS: Located in \___ \___, \___ \___ __, as well as in the \___ \___ of the inner ear (for head position)

STATIC POSITION SENSE

Proprioceptors: Orientation of the different parts of the body with respect to one another; Steady only (hindi gumagalaw)

KINESTHETIC SENSE

Proprioceptors: Movement of a body part & dynamic proprioception, Awareness of the range of movement that you are doing

NOCICEPTORS

Type of Sensory Receptor: Free nerve endings in the skin and other tissues

pain

NOCICEPTORS: Consist of \___ that occurs when tissues become destroyed or damaged; a way to tell our body something is harmful and to keep ourselves safe

FAST FIBERS

Nociceptors: Acute pain; Respond to intense mechanical stimuli or excessive heat

FAST FIBERS

Fast or slow: Nociceptors: Example: sharp pain, prickling pain, electric pain

SLOW FIBERS

Nociceptors: Chronic pain, Responds to temperature, intense mechanical stimuli, and chemicals

SLOW FIBERS

Fast or slow: Nociceptors: Example: slow burning pain, aching pain (body aches), throbbing pain, nauseous pain, and chronic pain

THERMORECEPTORS

Type of Sensory Receptor: Sensitive to warmth or cold

Cold receptors, warm receptors, temperature-sensitive nociceptors (extreme temperatures)

THERMORECEPTORS: Rectepors

relative degrees of stimulation

THERMORECEPTORS: Different gradations of thermal sensations are determined by \____ \___ \__ \___ of the different types of thermoreceptors

chemicals

THERMORECEPTORS: Aside from temperature, it responds to \____ (like menthol)

Post-Central gyrus - BA 1,2,3

SOMATOSENSORY CORTEX: What is the portion of the Brain?

Posterior lobe

Part of the brain related to the sensory systems

Frontal lobe

Part of the brain related to the motor systems

Contralateral

SOMATOSENSORY AREAS: \_____ representation d/t decussation of sensory fibers

Decussation

the crossing over of the fibers

right

if the left side of the brain is damaged, \____ side will have more somatosensory deficits because it is contralateral

Somatosensory Areas

This is where the processing and recognition of the stimuli starts

Somatosensory Area I

Somatosensory Areas: High degrees of localization of the different parts of the body; Central Part: thigh, thorax, neck, shoulder, hand, fingers, tongue, abdomen

Somatosensory Area II

Somatosensory Areas: Poor localization (roughly, face is anterior, arms are central, legs are posterior)

Sensory homunculus

SOMATOTOPIC ORGANIZATION: Some areas of the body are represented by large regions in the somatosensory cortex

larger

SOMATOTOPIC ORGANIZATION: Areas of the body surface w/ high receptor density occupy \____ areas in somatosensory cortex

laterally

Somatotopic Organization in the Spinal Cord: Facial area is more assigned \____

medially

Somatotopic Organization in the Spinal Cord: Trunk & Lips are assigned more \____

BA 5 and 7

SOMATOSENSORY ASSOCIATION AREAS

SOMATOSENSORY ASSOCIATION AREAS

Combines information arriving from multiple points in the primary somatosensory area to decipher its meaning and make a cohesive perception of the world

Somatosensory area I, Ventrobasal nuclei and other areas of the thalamus, Visual Cortex, Auditory Cortex

SOMATOSENSORY ASSOCIATION AREAS: Receives signals from:

without the help of some sensory systems

Since it receives signals from a lot of different places, the association areas can identify objects/understand the world \___________

organize, recognize

Function of the Primary Sensory Areas compared to Association Area: main function is to \___ the information and to an extent \___ the object already

SOMATOSENSORY PATHWAYS

Type of sensation, Location

Difference between the two somatosensory pathways:

POSTERIOR COLUMN - MEDIAL LEMNISCAL PATHWAY

Aka Dorsal-Column Medial Lemniscal Pathway

Fine discriminative touch, vibration, position sense, and deep pressure

POSTERIOR COLUMN - MEDIAL LEMNISCAL PATHWAY: Primary Sensations it Processes:

Mechanoreceptors and proprioceptors

POSTERIOR COLUMN - MEDIAL LEMNISCAL PATHWAY: Main Receptors it Responds to:

lower part to brain (down to up)

direction of the Sensory system pathway

Dorsal/Posterior Root

Specifically, the \_____ of the spinal cord (this is what the sensory system processes)

First-order neuron: dorsal root -\> dorsal column -\> synapse w/ dorsal column nuclei in the medulla; Second-order neuron: decussate -\> medial lemniscus -\> synapse w/ ventrobasal complex in the thalamus; Third-order neuron: project to the somatosensory cortex

POSTERIOR COLUMN - MEDIAL LEMNISCAL PATHWAY

lower medulla

POSTERIOR COLUMN - MEDIAL LEMNISCAL PATHWAY: Point of decussation

Nonspecific pathway for pain, temperature, and crude touch

ANTEROLATERAL PATHWAY: Primary Sensations it Processes:

Nociceptors and Thermoreceptors

ANTEROLATERAL PATHWAY: Main Receptors it Responds to:

Spinothalamic Tract:

ANTEROLATERAL PATHWAY: 3 tracts: main pathway for localization of pain

Lateral

ANTEROLATERAL PATHWAY: 3 tracts: Spinothalamic Tract: Pain and Temperature

Antero

ANTEROLATERAL PATHWAY: 3 tracts: Spinothalamic Tract: Crude Touch

Spinoreticular Tract

ANTEROLATERAL PATHWAY: 3 tracts: may be involved with attention and responds to pain (not clearly defined)

Spinomesencephalic Tract

ANTEROLATERAL PATHWAY: 3 tracts: control and inhibition of pain

First-Order Neuron: Dorsal root -\> synapse w/ dorsal horn cells of the spinal cord; Second-Order Neuron: decussate -\> anterior and lateral spinothalamic tracts -\> synapse w/ ventrobasal thalamus; Third-order neuron: project to the somatosensory cortex

ANTEROLATERAL PATHWAY

anterior and lateral white columns (spinal cord)

ANTEROLATERAL PATHWAY: Point of Decussation

Tactile sensations

ANTEROLATERAL PATHWAY: \___ \___will synapse to your ventrobasal complex

Pain

ANTEROLATERAL PATHWAY: \____ will synapse to the ventrobasal complex (ventral posterolateral [VPL] nucleus)

Oral peripheral mechanism (OPM)

ORAL SENSORY RECEPTORS: \_________ structures (face, lips, tongue, teeth, hard palate, soft palate, pharynx, and larynx)

Chemoreceptors, Mechanoreceptors, Proprioceptors, Nociceptors, Thermoreceptors

ORAL SENSORY RECEPTORS Also contains:

Cranial Nerves

ORAL SENSORY RECEPTORS: Innervated by

V - Trigeminal

Cranial Nerve: Pain, temperature, touch to face, hard palate, and anterior ⅔ of tongue

VII - Facial

Cranial Nerve: Taste to anterior ⅔ of tongue, proprioception to face

IX - Glossopharyngeal

Cranial Nerve: Touch and taste to posterior ⅓ of tongue, touch to soft palate, lateral and PPW

X - Vagus

Cranial Nerve: Sensation on lower pharynx and larynx

Receptors -\> Trigeminal Ganglion (CN V) -\> First-order neurons synapse w/ spinal nucleus of CN V -\> Second-order neurons decussate -\> Thalamus -\> Third-order Neurons -\> Somatosensory Cortex

CN V SENSORY PATHWAY: Pain and Temperature

Brainstem

CN V SENSORY PATHWAY: Pain and Temperature: Point of Decussation:

ganglion of CN V

CN V SENSORY PATHWAY: Pain and Temperature: First-order neuron \=

spinal nucleus of CN V (found in the brainstem)

CN V SENSORY PATHWAY: Pain and Temperature: Second-order neuron \=

Receptors -\> Trigeminal Ganglion (CN V) -\> First order neuron synapse w/ main sensory nucleus (CN V) -\> Second order neuron travel ipsilaterallly and contralaterally -\> Thalamus -\> Third-order neurons -\> Somatosensory cortex

CN V SENSORY PATHWAY: Pressure and Touch

Receptors -\> Petrosal Ganglion - \> First-order neurons synapse w/ nucleus tractus soliatrius (NTS) (medulla) -\> not known

CN IX SENSORY PATHWAY

PERCEPTION

How we process details, vibration, texture, objects, pain; How we integrate specific information

property of receptors

Sensitivity to process this information, is dependent to the

Merkel receptors

PERCEIVING DETAILS: \____ \____: govern our ability to perceive details; Very sensitive in processing groove patterns; Higher density in our fingertips; Respond well to changes that occur in the beginning and at the end of pressure stimuli

smaller

PERCEIVING DETAILS: Parallel representation in the brain: Higher density in our fingertips, the \___ the receptive fields, the more separation in the cortex

Pacinian Corpuscle

PERCEIVING VIBRATIONS: \___ \___: Consists of a series of layers with fluid between each layer, with this it transmits rapidly applied pressure, like vibration, to the nerve fiber

false

PERCEIVING VIBRATIONS: True or False: Pacinian Corpuscle responds to continuous pressure

Vibration

rapid pull and push of pressure

Spatial cues

PERCEIVING TEXTURE: Elements of space, Caused by relatively large surface elements, We can feel the frequency of bumps and grooves, Static and dynamic, Result in feeling different shapes, sized, and distributions of these surface elements

Temporal cues

PERCEIVING TEXTURE: Dynamic, Information: vibrations, for fine textures

Active Touch

PERCEIVING OBJECTS: \____ \____: allowed to explore the object, describing the object more than the sensation you’re feeling

Haptic Exploration

PERCEIVING OBJECTS: Active Touch: Presence of \____ \____: Allowed to explore what’s on your hand

Sensory system

PERCEIVING OBJECTS: Haptic Exploration: Systems involved: touch, temperature, and texture and the movements and positions of your fingers and hands

Motor system

PERCEIVING OBJECTS: Haptic Exploration: Systems involved: moving your fingers and hands

Cognitive system

PERCEIVING OBJECTS: Haptic Exploration: Systems involved: thinking about the information provided by the sensory and motor systems

Passive Touch

PERCEIVING OBJECTS: Stimulation on the skin, Tend to relate this to the sensation experience of the skin