Is the stretch reflex excitatory or inhibitory?
The Ia afferent directly causes excitation of the stretched muscle, and the inhibitory Ia interneuron mediates inhibition of the antagonist muscle. This impulse is also modulated by descending motor tracts, including the corticospinal tracts.
What is hyperactive stretch reflex?
Hyperactive stretch reflexes are seen when there is interruption of the cortical supply to the lower motor neuron, an “upper motor neuron lesion.” The interruption can be anywhere above the segment of the reflex arc. Analysis of associated findings enables localization of the lesion.
What type of reflex is a stretch reflex?
The stretch reflex is also referred to as the deep tendon reflex or myotatic reflex. It is a simple pre-programmed response by the human body in response to the muscle being passively stretched e.g. by a tendon hammer, or a sudden change in the ground surface.
Is a stretch reflex a Polysynaptic reflex?
The stretch reflex is a monosynaptic reflex that regulates muscle length through neuronal stimulation at the muscle spindle. The alpha motor neurons resist stretching by causing contraction, and the gamma motor neurons control the sensitivity of the reflex.
Is stretching a reflex?
The stretch reflex (myotatic reflex), or more accurately “muscle stretch reflex”, is a muscle contraction in response to stretching within the muscle. The reflex functions to maintain the muscle at a constant length….Clinical significance.
Is stretch reflex somatic or autonomic?
Somatic reflexes are involved in the reflex control of skeletal muscles and as such there are many different types of somatic reflexes including scratching reflexes, withdrawal reflexes and stretch reflexes and tendon reflexes.
What is reflex contraction?
The stretch reflex (myotatic reflex), or more accurately “muscle stretch reflex”, is a muscle contraction in response to stretching within the muscle. The reflex functions to maintain the muscle at a constant length. When a muscle lengthens, the muscle spindle is stretched and its nerve activity increases.
Are brisk reflexes good or bad?
A brisk response to tapping the trapezius, pectoralis major, and the finger flexors in the context of a tetraparesis suggests high cervical cord damage. Reflex spread (the fingers flex when eliciting the brachioradialis reflex) is also an indication of an upper motor neurone lesion.
What causes a stretch reflex?
The stretch reflex is activated (or caused) by a stretch in the muscle spindle. When the stretch impulse is received a rapid sequence of events follows. The motor neuron is activated and the stretched muscles, and its supporting muscles, are contracted while its antagonist muscles are inhibited (relaxed).
What is inverse stretch reflex?
The Golgi tendon reflex (also called inverse stretch reflex, autogenic inhibition, tendon reflex) is an inhibitory effect on the muscle resulting from the muscle tension stimulating Golgi tendon organs (GTO) of the muscle, and hence it is self-induced.
Why do we have a stretch reflex?
The stretch reflex is designed as a protective mechanism, to prevent strain and tear injuries to the muscles and tendons. When the muscle spindle is excited an impulse is immediately received to contract the muscle, thereby protecting it from being pulled forcefully or stretched beyond a normal range of motion.
Why is the stretch reflex important?
The stretch reflex is very important in posture. It helps maintain proper posturing because a slight lean to either side causes a stretch in the spinal, hip and leg muscles to the other side, which is quickly countered by the stretch reflex. This is a constant process of adjusting and maintaining.
What is the monosynaptic stretch reflex?
The monosynaptic stretch reflex, or sometimes also referred to as the muscle stretch reflex, deep tendon reflex, is a reflex arc that provides direct communication between sensory and motor neurons innervating the muscle. This reflex begins inside the muscle spindle of the muscle, which detects both the amount and rate of muscle stretch.
What is the difference between static stretch reflex and threshold?
This static stretch reflex response is the physiological basis of maintaining muscle tone [8,10,11]. On the other hand, there is a threshold, when the stronger a muscle is stretched, stronger is the reflex contraction. After crossing the threshold, contraction stops, and the muscle relaxes.
What is the function of the alpha efferent fibers in reflexes?
This alpha efferent fiber then exits through the ventral root and courses back sends an action potential to the neuromuscular junction of the original muscle that initiated the reflex to the synapse to cause contraction. This contraction allows the muscle to resist the force that initially caused the reflex.
What are γ motor and Ia sensory fibers?
A muscle spindle, with γ motor and Ia sensory fibers. A type Ia sensory fiber, or a primary afferent fiber is a type of afferent nerve fiber. It is the sensory fiber of a stretch receptor found in muscles called the muscle spindle, which constantly monitors how fast a muscle stretch changes.