What are the components of the stretch reflex circuit?
- Muscle spindle
- Sensory neuron
- Motor neuron
- Same muscle from where sensory neuron originated
The circuit allows for a rapid response to muscle stretching.
How many synapses are involved in the stretch reflex?
Only one synapse
This allows the shortest pathway for the reflex.
What happens to the muscle spindle when a muscle is stretched suddenly?
The central region of the muscle spindle is also stretched
This stretching increases the firing rate of the sensory nerve endings.
Which type of fibers carry signals from the muscle spindle to the spinal cord?
Type 1a fibres
These fibers transmit information about muscle stretch.
In the stretch reflex, where do the sensory neurons make synapse?
Directly with the alpha motor neurone of the same muscle
This connection facilitates immediate muscle contraction.
What do alpha motor neurons do in response to sensory neuron excitation?
Take impulses to the extrafusal fibres of the same muscle
This results in muscle contraction.
What is the purpose of stimulating extrafusal fibers in the stretch reflex?
Causes muscle contraction
This prevents further stretching of the muscle.
What is reciprocal innervation?
A branch of the same sensory neuron innervates an inhibitory interneuron
This affects the motor neuron that supplies the antagonistic muscles.
What role does the inhibitory interneuron play in reciprocal innervation?
Releases inhibitory neurotransmitters that decrease excitation of motor neurons to antagonistic muscle
This leads to relaxation of the antagonistic muscle.
What is the effect of the alpha motor neurons on the agonist muscle?
Cause muscle contraction
This action is complemented by the relaxation of the antagonistic muscle.
How does reciprocal innervation affect the effectiveness of the stretch reflex?
Increases the effectiveness of the stretch reflex
By inhibiting the antagonistic muscle, it allows for smoother movement.
