Somatic Sensory System Flashcards
Comprises specialized nerve cells that respond to stimuli within or outside the body
Sensory Receptors
What is the job of sensory receptors?
Convert stimulus energy to electrical energy –> action potentials.
What means that a sensory signal reached CNS?
Perception
Nervous system responsible for taking in information from the environment and relaying it to the CNS.
Sensory System
Basic Pathway of Sensory System.
Stimulus Energy –> Transduction –> Sensory Receptor –> Output to CNS —> Perception
Overview of somatic sensations conveying to the CNS and the brain?
receptor endings –> mechanosensory afferent fiber –> dorsal root ganglion cells –> then travels up the spine.
The pathway depends on modality. What are the two types of modalities?
Discriminative touch.
Pain and Temperature
What are the First Order Neurons?
Mechanosensory Receptors From the Lower Body
Mechanosensory Receptors From the Upper Body
What are the Second Order Neurons?
Cuneate Nucleus
Gracil Nucelus
What are the Third Order Neurons?
Ventral Posterior Lateral Nucleus of Thalamus
Where does discriminative touch cross?
High in the Medulla Oblongata
Mechanosensory receptors from the upper body come in the level of?
Cervical Spinal Cord
Mechanosensory receptors from the lower body come in the level of?
Lumbar Spinal Cord
Gracile nucleus (pathways from _______ ________)
Lower Body
Cuneate nucleus (pathways from _______ _______)
Upper Body
What does decussate mean?
2nd order neurons projecting axons across the midline
Where does 2nd order nuerons synapse? What general location?
Caudal medulla (Gracile or Cuneate)
Where is the primary somatic sensory cortex located?
Post-Central gyrus
What is the dividing line of the brain?
Central Sulcus
Pathway for the face to the primary somatic sensory?
Mechanosensory receptors from face (Trigeminal ganglion) –> principal nucleus of trigeminal complex –> medial lemniscus –> trigeminal lemiscus –> Thalamus –> Primary Somatic Sensory Cortex
Somatosensory cortex is subdivided into ________ ______?
Brodmann’s Areas
What are the four areas of Brodmann?
1
2
3a
3b
What does cutaneous mean?
sensations coming through the skin
What does proprioceptive mean?
Where your body is in space. (sensations coming through the muscles, tendons)
What areas are cutaneous?
1 and 3b
What area(s) are proprioceptive?
3a
What area(s) are both cutaneous and proprioceptive?
2
What is the order of the areas from anterior to posterior?
3a
3b
1
2
Info from body comes through ______ of the thalamus?
VPL (Ventral Posterior Lateral Nucleus)
Info from face comes through _______ of the thalamus?
VPM (Ventral Posterior Medial Nucleus)
Primary Somatic Sensory Cortex: Number of neurons (or size of the cortex) is not proportional to ?
the size of that part of the body
Somatic sensory system sensory receptors specialized to transduce?
mechanical (kinetic) energy
Stimuli leads to ?
Deformation (changes in the shape of the cell membrane of the receptor)
Deformation leads to ?
Changes in the conductance of nerve ending
What causes changes in the conductance of nerve endings?
Altering the permeability of ion channels
What causes changes in the membrane?
Stimuli (Mechanically gated channels open)
After deformation what will you get?
A receptor (generator) potential
What is a receptor potential?
Changes of the membrane potential of the receptor.
What will cause an action potential?
Receptor potential is threshold or suprathreshold.
Action potential is conducted?
Centrally
What is signal transduction?
Conversion of stimulus energy to electrical energy
Receptors are ?
Transducers
CNS interprets stimulus ______ and _______.
quality and quantity.
What does it mean by quality?
What and where the stimulus is.
What is quality determined by? (two things)
- Type of receptor responding
2. Location of central target
What does it mean by quantity?
Strength of stimulus
What is quantity determined by?
Frequency of action potentials
Quality of stimulus is the # of ______ ______ _____ that respond to a stimulus.
Different receptor cells
Receptive Field =
Area of skin that sensory neuron innervates (is supplied)
Receptive fields are usually small when ?
High receptor density
Two-point discrimination:
Method of measuring minimal distance needed to sense two different and simultaneous stimuli.
What two things does the two-point discrimination depend on?
- Receptor density
2. Receptive fields
Sensory Adaptation:
Size of receptor potential and frequency of AP can decline if the stimulus persists
What are the two types of receptor classification based on response to enduring stimuli?
Phasic
Tonic
Phasic:
Rapidly Adapting
Tonic:
Slowly Adapting
Phasic responds to ________ stimuli.
Dynamic
What are the major subsystems of the SSS?
Mechanosensory
Pain/Thermal
Mechanosensory:
Detects mechanical stimuli
Receptors have nerve endings encapsulated in CT to modulate inputs
Pain/Thermal
Detects painful and thermal stimuli
Receptors have free nerve endings
In mechanosensory external stimuli receptors are found in?
Skin
In mechanosensory internal stimuli receptors are found in?
Muscles, joints, bonds and other deep tissues
Internal stimuli has to do with?
Proprioception
Examples of encapsulated nerve endings.
Meissner corpuscle
Merkel cell
Myelinated Type AB fibers Dermal papillae of glabrous skin Encapsulated by Schwann Cells Most common mechanoreceptor fo glabrous kin Stimulus - Light touch Phasic
Meissner’s Corpuscles
Myelinated Type AB fibers Dermis of glabrous skin Encapsulated Stimulus - Deep touch, ticklish (response) Phasic
Pacinian Corpuscle
Myelinated Type AB fibers Dermis of glabrous skin, ligaments and tendons Encapsulated Stimulus -Stretch Tonic
Ruffini’s Corpuscles
Myelinated Type AB fibers
Location - In epidermis (Deep folds)
Encapsulated and in close apposition to modulating cell that secretes neuromodulator
Stimulus - Shapes, edges, and rough textures
Tonic
Merkel’s Disk
List (of most used to least used) receptor to read braille.
Merkel Cell
Meisnner Corpuscle
Ruffini Corpuscle
Pacianian Corpuscle
