Lecture 20 Flashcards
What provide afferent information essential for controlling muscle activity
Muscle spindles and the Golgi tendon organs
What are the proprioceptors in muscles
– Golgi Tendon Organs • Present in tendons • Report muscle tension development – Muscle Spindles • Embedded within muscle • Report muscle position, “Stretch”
How are the information for control of muscle activity use
- Appraisal of motor areas of the brain about
muscle length and tension. - Control of muscle length and tension in a
negative-feedback fashion by means of local
spinal reflexes
How are the motor neuron influenced
- Local reflex circuitry
- Descending pathways
from the brain stem
and cerebral cortex
What are the components of a simple reflex
-Integration centre (interneuron) -Efferent arm (output) -Response element -Sensor (receptor) -Afferent arm (input)
What are interneurons
the central nodes of neural circuits, enabling communication between sensory or motor neurons and the central nervous system (CNS)
Why most descending synaptic input does not go
directly to motor neurons
because information have to return to interneuron
• Synapse with interneurons which synapse
with motor neurons
• 90% of spinal cord neurons
• Integrate input from higher centres,
peripheral receptors and other interneuronshe interneuron first
Afferent fibres carry information from sensory
receptors in three sources
- In skeletal muscles controlled by motor
neurons - In other nearby muscles, especially
antagonists - In the tendons, joints, and skin of body parts
affected by muscle action
What are muscle spindle located at
located within fleshy part of
muscle
• Intrafusal fibers parallel to
extrafusal fibers
Are muscle spindle contractible
• Noncontractile central portion
What do the muscle spindle detect
- rate of change at which the
muscle fibers are stretched - changes in length of muscle fibers
What is the role on muscle spindle
• aids in coordination and
efficiency of muscle contraction
What are the types of muscle spindle fibres
- Nuclear bag fibres
* Nuclear chain fibres
What is a Nuclear bag fibres
– Large number nuclei
packed into mid-portion
– Sense onset of stretch
What is a Nuclear chain fibres
– Nuclei in longitudinal
row
– Sense sustained stretch
How are the muscle spindles activated
Both are activated with
rapid stretch
What is the Efferent neuron which
innervates intrafusal
fibres
gamma (γ)
motor neuron
What is the Extrafusal fibres
alpha
(α) motor neuron
How are muscle spindle attached
by connective
tissue in parallel to the
extrafusal fibres.
Can external force activate the muscle spindle
yes, External force stretching the muscle also stretches the intrafusal fibres activating their receptor endings
How are the information sent
in frequencies, the more stretched or faster is it, the higher the frequency in signals. The more or the faster the muscle is stretched, the greater the rate of receptor firing
What does sudden stretch of a muscle result in
- Muscle spindles detect stretch of the muscle
- Sensory neurons conduct action potentials to the spinal cord
- Sensory neurons synapse direct with alpha motor neurons
- Alpha motor neurons conduct action potential to the muscle, causing it to contract and resist being stretched.
What happen during The stretch, or myotactic, reflex
– Produces rapid corrections of motor output in the
moment to moment control of movement
– Forms the basis for postural reflexes to maintain
body position.
What is the Golgi Tendon Organs located at
located at junction of tendon and
muscle
what does the Golgi Tendon Organs detect
• detects:
- force of muscle contraction
- tension applied to tendon
What is the role of golgi tendon organ
• protects tendon and muscle from excessive tension • Muscle contraction stretches the GTO and generates AP • Greater the force of contraction higher firing rate
What is Golgi Tendon Organs made of
A large diameter myelinated type
1b axon arises from each GTO
What is the tendon reflex like
- increased tension stimulates sensory receptor (tendon)
- Sensory neuron excited
- Within intergrating center (spinal cord), sensory neuron activates inhibitory interneuron
- Motor neuron inhibited
- effector (muscle attached to same tendon) relaxes and relieves excess tension
What is the main role of a tendon organ
monitor tension
what is Reciprocal Innervation
where sign sent of no reponse to the opposite muscle to not counteract it
