Table of Contents
How is the muscle spindle stimulated in the patellar reflex?
When the patellar tendon is tapped with a reflex hammer, the muscle spindles are stimulated, which causes an immediate concentric contraction of the quadriceps muscle group.
Is muscle spindle involved in knee jerk reflex?
A simple example of muscle spindle activity is the knee jerk reflex (Patellar reflex), sudden kicking movement of the lower leg in response to a sharp tap on the patellar tendon, which lies just below the kneecap.
What does the muscle spindle reflex do?
Muscle spindles are sensory receptors that are located in muscle. Their job is to detect changes in muscle length and the speed of change in muscle length.
Where are the muscle spindles located?
extrafusal fibers
The Muscle Spindle is a proprioceptive receptor composed of intrafusal fibers that are located within the extrafusal fibers of skeletal muscle. The intrafusal fibers of the muscle spindle run parallel to the extrafusal fibers of the muscle, attaching to them along short segments.
What nerve is responsible for the patellar reflex?
Purpose. The patellar tendon reflex tests the function of the femoral nerve and spinal cord segments L2-L4. The absence or decrease of this reflex is known as Westphal’s sign.
Where are muscle spindles located?
Muscle spindles are found within the belly of a skeletal muscle. Muscle spindles are fusiform (spindle-shaped), and the specialized fibers that make up the muscle spindle are called intrafusal muscle fibers. The regular muscle fibers outside of the spindle are called extrafusal muscle fibers.
Which nerve is responsible for patellar reflex?
What type of reflex is the patellar stretch reflex?
The knee-jerk reflex, also known as the patellar reflex, is a simple reflex that causes the contraction of the quadriceps muscle when the patellar tendon is stretched.
What is muscle spindles?
Functionally, muscle spindles are stretch detectors, i.e. they sense how much and how fast a muscle is lengthened or shortened [19]. Accordingly, when a muscle is stretched, this change in length is transmitted to the spindles and their intrafusal fibers which are subsequently similarly stretched.
What causes absent knee jerk reflex?
An absent or diminished patellar tendon reflex may be due to PNS pathology affecting either the afferent sensory neurons or the efferent motor neurons. If the reflex is absent or diminished combined with sensory loss, the lesion is likely in the afferent sensory nerves.
What causes loss of patellar reflex?
[1] Many additional causes of peripheral neuropathy can yield an absent or diminished patellar tendon reflex, including diabetes, alcohol use disorder, amyloidosis, vitamin deficiencies, toxins, and remote cancer.
What nerve is tested in patellar reflex?
The patellar tendon reflex tests the function of the femoral nerve and spinal cord segments L2-L4. The absence or decrease of this reflex is known as Westphal’s sign.
What is muscle spindle?
Definition of muscle spindle : a sensory end organ in a muscle that is sensitive to stretch in the muscle, consists of small striated muscle fibers richly supplied with nerve fibers, and is enclosed in a connective tissue sheath. — called also stretch receptor.
How does a reflex hammer stretch the patella?
Striking the patellar tendon with a reflex hammer just below the patella stretches the muscle spindle in the quadriceps muscle. This produces a signal which travels back to the spinal cord and synapses (without interneurons) at the level of L3 in the spinal cord, completely independent of higher centres.
What is the mechanism of action of the patellar muscle?
Mechanism. Striking the patellar tendon with a reflex hammer just below the patella stretches the muscle spindle in the quadriceps muscle. This produces a signal which travels back to the spinal cord and synapses (without interneurons) at the level of L3 in the spinal cord, completely independent of higher centres.
What is a monosynaptic reflex Quizlet?
A monosynaptic reflex, such as the knee jerk reflex, is a simple reflex involving only one synapse between the sensory and motor neurone. The pathway starts when the muscle spindle is stretched (caused by the tap stimulus in the knee jerk reflex). The muscle spindles are responsible for detecting the length of the muscles fibres.
What is an example of muscle spindle activity?
A simple example of muscle spindle activity is the knee jerk reflex (Patellar reflex), sudden kicking movement of the lower leg in response to a sharp tap on the patellar tendon, which lies just below the kneecap.