L14 Proprioception Flashcards
Submodalities of Proprioception?
Limb Position Sense: Sense of stationary limb position
Kinesthesia: Sense of speed and direction of limb movement
Location/What is detected by Golgi Tendon Organs?
Location: Junctions of Muscle and Tendon
Detects:
○ FORCE of muscle contraction (Greater on tendon => increased firing)
○ TENSION applied to a tendon (Only @ extreme tensions, at verge of failure)
Protects tendon/muscle from excessive tension (Inhibits muscles when they approach the point of potential tissue damage)
Which type of mechanoreceptor protects tendon/muscle from excessive tension? How does it do so?
Golgi Tendon Organs inhibit muscles when they approach the point of potential tissue damage
Location/What is detected by Joint Kinesthetic Receptors?
Location: Synovial Joint Capsules
Detects:
○ FLEXION/EXTENSION of the joint
○ ACCELERATION/DECELERATION of Joint Movement
○ PRESSURE in joint
○ Excessive joint STRAIN
Stretch-sensitive receptors in the skin (Ruffini endins/Merkel’s Disks) also detect postural changes
Which type of mechanoreceptor detects Joint FLEXION/EXTENSION, ACCELERATION/DECELERATION, PRESSURE, and STRAIN?
Joint Kinesthetic Receptors
Stretch sensitive receptors in the skin (Ruffini endings/Merkel’s Disks) also detect postural changes
Location/What is detected by Muscle Spindles?
Location: Within Corpus of Skeletal Muscle
Detects:
○ Changes in Muscle LENGTH
○ RATE of change of muscle fiber length
Aids in coordination and efficiency of muscle contraction
Which type of mechanoreceptor aids in the coordination and efficiency of muscle contraction?
Muscle Spindle
Main components of the Muscle Spindle? (3)
- Intrafusal muscle fibers (Nuclear Bag Fibers, Nuclear Chain Fibers)
- Afferent sensory fiber-endings
- Efferent motor fiber-endings
Two Types of Intrafusal Muscle Fiber?
Nuclear Bag Fibers:
□ ____ fibers per spindle
□ Nuclei concentrated in “bag type” central part of fiber
□ Sensitive to ________________________________
□ Ends of fibers are:
- Straited (containing actin/myosin)
- Contractile
- Attached to __________________________
Nuclear Bag Fibers:
□ 1-3 fibers per spindle
□ Nuclei concentrated in “bag type” central part of fiber
□ Sensitive to RATE OF CHANGE in muscle length
□ Ends of fibers are:
- Straited (containing actin/myosin)
- Contractile
- Attached to EXTRAFUSAL FIBERS (Normal Contractile Skeletal Muscle)
Nuclear Chain Fibers:
□ ______fibers per spindle
□ Nuclei spread in a chain-like fashion in center of fiber
- Sensitive to ______________________________
□ Ends of fibers are:
- Straited (containing actin/myosin)
- Contractile
- Attached to ________________________
Nuclear Chain Fibers:
□ 3-7 fibers per spindle
□ Nuclei spread in a chain-like fashion in center of fiber
- Sensitive to ABSOLUTE LENGTH of muscle
□ Ends of fibers are:
- Straited (containing actin/myosin)
- Contractile
- Attached to ENDS OF NUCLEAR BAG FIBERS
Intrafusal fibers sensitive to RATE OF CHANGE in muscle length?
Nuclear Bag Fibers
Intrafusal fibers sensitive to ABOLUTE LENGTH of muscle?
Nuclear Chain Fibers
Sensory Neurons that Innervate Nuclear Bag and Nuclear Chain Fiber?
- Diameter?
- Speed of Conduction?
- Facet of Muscle the Neuron responds to?
- Receptors Innervated?
- Type of Ending?
1) Primary Endings (Type Ia Fibers)
□ 15 micron Diameter
□ Conducts impulses @ 100m/s (Larger diameter= faster conduction)
□ Responses to RATE OF CHANGE in muscle fiber length
□ Innervates Proprioceptors of Skeletal Muscle
□ Annulospiral Endings
2) Secondary Endings (Type II Fibers)
□ 8-micron diameter
□ Conducts impulses more slowly
□ Responds to OVERALL LENGTH of muscle fiber
□ Innervates mechanoreceptors of Skin
□ Flower-Spray Endings
Sensory Neurons that Innervate Nuclear Bag and Nuclear Chain Fiber?
- Diameter?
- Speed of Conduction?
- Facet of Muscle the Neuron responds to?
- Static/Dynamic Response
- Receptors Innervated?
- Type of Ending?
1) Primary Endings (Type Ia Fibers)
□ 15-micron Diameter
□ Conducts impulses @ 100m/s (Larger diameter= faster conduction)
□ Responses to RATE OF CHANGE in muscle fiber length
- Firing INCREASES during Stretch, DECREASES from Relaxation
□ Innervates Proprioceptors of Skeletal Muscle
□ Annulospiral Endings
2) Secondary Endings (Type II Fibers)
□ 8-micron diameter
□ Conducts impulses more slowly
□ Responds to OVERALL LENGTH of muscle fiber
- Firing rate not affected by Tap/Vibration
□ Innervates mechanoreceptors of Skin
□ Flower-Spray Endings
Describe the Muscle Spindle response to stretch
As membrane is deformed, cytoskeletal chains pull ion channels open => cell depolarization
Greater the force=> more ion channels open (Graded Response: the amount of depolarization ∞ to force of stretch)
Describe the Knee Jerk Reflex
Tap on Tendon => stretch on quadriceps=> activates dynamic fibers => sensory signal up through spinal cord => synapses on motor neuron:
- => ACTIVATES QUADRICEPTS
- => INHIBITS hamstring
Muscle Spindle afferent is stimulated => _____ generated with _______ latency in the motor neuron going to the same muscle. What does this indicate?
Muscle Spindle stimulated in an Antagonistic Muscle => _____ generated with ______ latency
What does this indicate?
Muscle Spindle afferent is stimulated => EPSP generated with SHORT latency in the motor neuron going to the same muscle, indicating a direct, excitatory connection
Muscle Spindle stimulated in an Antagonistic Muscle => IPSP generated with LONG latency, indicating an inhibitory interneuron is involved
EPSPs and IPSPs from Spindle Afferents start as __________ encoded but are converted to ______________ encoded
Describe the process of Modification to SPINDLE Response during Stretch/Relaxation of Muscle FIBERS…
Fusimotor Firing modifies Spindle Response to Stretch:
Muscle FIBER shortens, must also shorten muscle SPINDLE (sensory)
- Efferent ALPHA motor neurons are activated (Shortens Muscle FIBERS)=> activate Efferent GAMMA neurons innervating Intrafusal Muscal Fibers => Shortens Muscle SPINDLES
- Spindle sensitivity maintained throughout Fiber contraction
Describe the pathway responsible for conveying conscious awareness of limb position?
Dorsal Column/Medial Lemniscus Pathway:
- Sensory neurons ascend IPPSILATERALLY to Medulla
- 2nd order neurons decussate and synapse in CONTRALATERTAL Thalamus
- 3rd order neurons synapse in CONTRALATERAL Cortex (Responsible for conscious awareness of limb position)
Different pathways for conveying proprioceptive information to the Cerebellum?
- Posterior Cerebellar Tract from the LOWER body
- Cuneocerebellar Tract from the UPPER body.
These pathways both travel ipsilaterally to the ipsilateral Cerebellum
1st order sensory neurons from proprioceptors ALSO synapse on ascending neurons in the CNS and ascend via one of three pathways to the brain:
- _________________________
- Sensory neurons ascend ______________ to ___________________
- 2nd order neurons decussate and synapse in _______________________________
- 3rd order neurons synapse in _________________________ (Responsible for conscious awareness of limb position)
- Two IPSILATERAL pathways to the Cerebellum:
- ___________________________ from the LOWER body
- ____________________________ from the UPPER body.
- _________________________
- Appears to carry information relating to joint position, remains active when the dorsal roots are cut!!
- Not purely sensory, probably relays info about spinal motor neuron activity.
1) Dorsal Column/Medial Lemniscus Pathway:
- Sensory neurons ascend IPPSILATERALLY to Medulla
- 2nd order neurons decussate and synapse in CONTRALATERTAL Thalamus
- 3rd order neurons synapse in CONTRALATERAL Cortex (Responsible for conscious awareness of limb position)
2) Two IPSILATERAL pathways to the Cerebellum:
- Posterior Cerebellar Tract from the LOWER body
- Cuneocerebellar Tract from the UPPER body.
3) Anterior Spinocerebellar Tract.
- Appears to carry information relating to joint position, remains active when the dorsal roots are cut!!
- Not purely sensory, probably relays info about spinal motor neuron activity.
