Circuit of the Strength Reflex Muscle spindle Dorsal root Muscle fiber Tendon Ventral root a-mn
Circuit of the Strength Reflex Dorsal root Ventral root Muscle spindle Tendon Muscle fiber a-mn
The stretch reflex (A)Muscle spindle Motor o Exciting a muscle spindle neuron occurs in two ways Extrafusal Applying a force that fib bers lengthens the entire muscle neuron Activating the y motor Spindle neurons that stimulate the afferent (a distal ends of the intrafusal afferent) fibers to contact o thus stretching the mid-portion Intrafusal of the spindle(internal stretch) fibers
The Stretch Reflex ⚫ Exciting a muscle spindle occurs in two ways – Applying a force that lengthens the entire muscle – Activating the motor neurons that stimulate the distal ends of the intrafusal fibers to contact, ⚫ thus stretching the mid-portion of the spindle (internal stretch)
The stretch Reflex ● Whatever the Muscle Muscle during stretch during contraction stimulus. when the Muscle spindles are activated spindle Intrafusal muscle fiber ● their associated sensory neurons m transmit impulses at a sense nerve higher frequency to Extrafusal the spinal cord muscle fiber Time Time (a) Action potential frequency (b) Action potential frequency Increases during stretch declines during contraction SBENJAMIN/CUMMINGS
The Stretch Reflex ⚫ Whatever the stimulus, when the spindles are activated ⚫ their associated sensory neurons transmit impulses at a higher frequency to the spinal cord
(a)A monosynaptic reflex has a single synapse between the afferent and efferent neurons Stimulus Receptor Sensory neuron Spinal cord Integrating Skeletal muscle center Somatic motor neuron arget cell Efferent ne Response effector neuron synapse (b) Polysynaptic reflexes have two or more synapses 补s Spin Stimulus Receptor Sensory cord neuron Integrating center Interneuron Synapse 2 Efferent Response Target cell effector neuron
(a)A monosynaptic reflex has a single synapse between the afferent and efferent neurons Stimulus Receptor Sensory neuron Spinal cord grating Skeletal muscle center Somatic motor neuron Response Target cell Efferent One effector neuron o At spinal cord sensory neurons synapse directly (mono- synaptically) with the a motor neurons which rapidly excite the extrafusal muscle fibers of stretched muscle
The Stretch Reflex ⚫ At spinal cord sensory neurons synapse directly (mono- synaptically) with the a motor neurons which rapidly excite the extrafusal muscle fibers of stretched muscle