Lecture 2 (Receptors And Afferent Pathways) Flashcards
What does sensory information promote? Where is sensory info from?**
-adaptations in posture and movement (planned and reactive)
-sent from peripheral receptors
What is perception? What does it interpret?**
-Awareness of stimuli
-Interprets sensory info into meaningful forms (ex. Reaching for keys)
What type of process is perception? What are 3 examples?**
-active and ongoing process: perception involves acting within the environment
-proprioception, visual, vestibular
What are 3 cutaneous sensory receptors? Examples of each**
-mechanoreceptors (pressure, touch, vibration, proprioception)
-thermoreceptors (heat, cold)
-nociceptive (pain)
What are 5 cutaneous receptors?**
Meissner corpuscle
Pacinian corpuscle
Ruffini’s corpuscles
Merkel’s disks
Free nerve endings
What does Meissner corpuscle sense?**
Discriminative touch and low frequency vibrations
What does Pacinian corpuscle sense?**
High vibration and sudden stimuli
What does Ruffini’s corpuscle sense?**
Stretch
What does Merkel’s disks sense?
Surface pressure, static touch, hair follicles
What do free nerve endings sense?**
Pain, heat, cold
Where are Meissner’s corpuscles found? What vibration level does it sense? Velocity?
-superficial skin, greater density at fingertips
-30-50 Hz (flutter)
-velocity sensitive 2-40 mm/s
Where are Pacinian corpuscles found? Higher density found? What type of receptive fields?
-subcutaneous
-in fingertips
-large receptive fields (>4mm)
Where are Merkel’s Discs found? What is the receptive field range? What do they respond to?
-found in superficial skin (greater density at fingertips); dermis and hair follicles
-small receptive field (2-4mm)
-responds to pressure, touch and form
What is glamorous skin?
Has no hair
Where are free nerve endings found? What do they detect?
-throughout the skin and viscera (internal organs); in epidermis
-detects temp, pain, tickle and itch
What does pain stimulus do? What type of stimuli set it off?
-Translate potentially damaging stimuli into electrochemical signals
-mechanical, thermal, or chemical stimuli
What are two types of pain?
Nociceptive and neuropathic
What is nociceptive pain a result from? Is it a normal or abnormal response?
Activation of pain receptors in body due to tissue injury/inflammation; normal
What is neuropathic pain?
Direct injury to neural tissue, typically results in burning, radiating, following peripheral nerve
What do pain receptors transmit? Give examples
-precise information
-where injury is located
-characterized as sharp or dull (pressure, heat, cold)
What do pain receptors in organs do?
Refer pain to other locations since pain receptors in organs are not precise
What are myelinated delta free nerve endings? What types of sensations do they carry? Sense pain immediately or over time?
-afferent fibers
-carry sharp, stabbing, pricking pain or cold
-immediately
What type of pain does unmyelinated C fibers carry? What is the activation threshold like? Polymodal pain receptors?
-dull ache pain
-threshold is higher since info travels slower
-chemical, heat thermal, mechanical, hypoxia
What are the 4 different sizes of axons (motor and sensory)
-Alpha (motor neuron): highly myelinated, high speed transmission
-Beta (sensory neuron): Pacinian, Ruffini, Meissner, Merkel
-Delta: myelinated free nerve ending
-C fibers: free nerve ending
What is a muscle spindle and where is it found? Function?
-Sensory proprioception within muscle belly
-Gives feedback about muscle performance and speed
Which is intrafusal and extrafusal: muscle spindle and muscle
MS = intrafusal
Muscle = extrafusal
Where does MS send info to? What does that structure do with the info? **
-cerebellum
-calculate joint position and other variables to make appropriate movement
What does the cerebellum house, regarding muscle spindles?**
Motor memory (length and velocity)
What do muscle spindles respond to?**
Length and velocity of stx
Does muscle spindle contribute to force generation?
No, GTOs do
What do tendon reflexes assess?
The integrity of the MS system
What do GTOs give feedback about
Amount of force in a tendon
Describe how the patellar tendon reflex happens
Tendon tap = stimulus
Muscle spindle = receptor
Afferent neuron 1a (sensory neuron) sends info to SC
SC synapses synapse w/ other neurons
Two motor (effector) neurons activate muscles (one contracts quad, the other inhibits hs)
What is an order neuron?
Delivery of sensory info from periphery to cortex
How does stimulus travel to cortex?
-through PNS - dorsal root ganglion (1st order neuron)
-SC (2nd order neuron)
-Thalamus (relay; 3rd order neuron)
-Cortex
What are the two major sensory pathways?
Anterolateral (spinothroacic tract)
Posterior (dorsal) Columns (medial lemniscal pathway)
What does the anterolateral pathway sense? Where is the Decussation?
-pain, temp, crude touch
-SC
What info does the posterior (dorsal) column sense? Where is the Decussation?
-vibration, joint position, fine touch
-medulla
