What causes jaw jerk reflex?

What causes jaw jerk reflex?

The jaw-closing reflex occurs when the jaw-closing muscles are suddenly stretched by a rapid downward tap on the chin. This tap causes stretching of specialized sensory receptors called muscle spindles that are stretch sensitive. They are present within all the jaw-closing muscles.

What are the 2 reflexes associated with the trigeminal nerve?

Clinical Significance

• As the trigeminal nerve supplies sensory and motor innervation to a plethora of features, clinical examination of CN V should evaluate the response of each structure.
• Nociception and light touch are the principal sensory modalities tested during the assessment of CN V sensory reflexes.

Which type of reflex is the jaw jerk reflex?

stretch reflex
This is a stretch reflex similar to the knee-jerk reflex. The muscle spindle is the sensory receptor and the reflex pathway goes via the trigeminal mesencephalic nucleus to jaw-closing motoneurones and the jaw-closing musculature (Fig. 6.2B). The reflex is usually monosynaptic, but a polysynaptic pathway also exists.

Why jaw jerk is exaggerated in pseudobulbar palsy?

Trismus: Acute pseudobulbar palsy can present with trismus due to the bilateral infarction of the internal capsule. On physical examination, there is a brisk jaw jerk. Other facial reflexes also become exaggerated. There are retained or increased palatal reflexes.

What is the masseter inhibitory reflex?

Masseter inhibitory reflex (MIR), also known as jaw-opening reflex (jaw jerk reflex), temporalis muscle exteroceptive suppression, and masseter silent period, manifests in reflex inhibition of the voluntary contraction of the muscles of mastication in response to intensive mechanical or electrical stimulation of the …

What nerve stimulates the masseter and temporalis muscles?

the masseteric nerve
Stimulation of the masseteric nerve evoked an M-response in the masseter and an H-reflex in both the masseter and the temporal muscles.

What is the pathway of the trigeminal nerve?

The Ophthalmic nerve (V1), passes forward in the lateral wall to the cavernous sinus. It then enters the orbit via the superior orbital fissure. The Mandibular nerve (V3), runs laterally along the skull base then exits the cranium by descending through the foramen ovale into the masticator space.

What cranial nerves are affected by bulbar palsy?

1 Bulbar Palsy. A bulbar palsy refers to disease affecting the glossopharyngeal, vagus, accessory and hypoglossal nerves and is due to lower motor neuron pathology. Typically, patients with a bulbar palsy present with signs and symptoms of the cranial nerves affected as mentioned.

What does the blinking reflex involve?

The corneal eye blink reflex is initiated by the free nerve endings in the cornea and involves the trigeminal nerve and ganglion, the spinal trigeminal tract and nucleus, interneurons in the reticular formation, motor neurons in the facial nucleus and nerve, and the orbicularis oculi.

What nerve innervates the masseter?

the trigeminal nerve
The masseter is primarily responsible for the elevation of the mandible and some protraction of the mandible. It receives its motor innervation from the mandibular division of the trigeminal nerve.

What is difference between bulbar and pseudobulbar palsy?

Overview. A bulbar palsy is a lower motor neuron lesion of cranial nerves IX, X and XII. A pseudobulbar palsy is an upper motor neuron lesion of cranial nerves IX, X and XII.

What is the difference between bulbar palsy and bulbar ALS?

Progressive bulbar palsy (PBP) is a classic phenotype of bulbar onset amyotrophic lateral sclerosis (ALS) with more rapid progression and worse prognosis. However, as an often under-understood variant of ALS, isolated bulbar palsy (IBP) appears to progress more slowly and has a relatively benign prognosis.

Is bulbar palsy lower motor neuron?

A bulbar palsy refers to disease affecting the glossopharyngeal, vagus, accessory and hypoglossal nerves and is due to lower motor neuron pathology. Typically, patients with a bulbar palsy present with signs and symptoms of the cranial nerves affected as mentioned.

Is blinking a spinal reflex?

The purpose of this reflex is to protect the eyes from foreign bodies and bright lights (the latter known as the optical reflex). The blink reflex also occurs when sounds greater than 40–60 dB are made….

Which nerve is responsible for blinking?

Anatomy. The afferent limb of the blink reflex is mediated by sensory fibers of the supraorbital branch of the ophthalmic division of the trigeminal nerve (cranial nerve V1) and the efferent limb by motor fibers of the facial nerve (cranial nerve VII).