neurologic controls of swallowing

Is swallowing reflexive, voluntary, or both?

Both reflexive and voluntary

Which neural systems regulate swallowing?

Central and peripheral nervous systems

What levels of the nervous system are involved in swallowing?

Cranial nerves, brainstem, cerebellum, subcortex, cortex

What are the four major components of neural control of swallowing?

Cortical and midbrain fibers, efferent motor fibers, afferent sensory fibers, paired brainstem swallowing centers

Primary role of the cortex in swallowing?

Evoking and facilitating initiation of swallowing (volitional control)

Which three cortical regions are most important for swallowing?

Premotor cortex, precentral cortex (primary motor), and anterior insula

Primary role of the premotor cortex in swallowing?

Planning swallowing movements within the motor cortex network

Why is the premotor cortex important for swallowing?

Contains motor representations of the mouth and connects with cranial nerves (motor and sensory)

If the premotor cortex is damaged, what swallowing problem is most likely?

Poor planning and initiation of voluntary swallowing movements (oral phase difficulty)

Which cortical areas induce the oral phase of swallowing?

Lower and posterior precentral gyri and posterior frontal gyri of the motor cortex

If the lower and posterior precentral gyri are damaged, which swallowing phase is most affected?

Oral preparatory and oral transport phases

Which cortical areas induce the pharyngeal and esophageal phases of swallowing?

Antero-inferior and middle frontal gyri of the motor cortex

If the antero-inferior and middle frontal gyri are damaged, what swallowing deficit may occur?

Impaired initiation or coordination of pharyngeal and esophageal swallowing

For a normal swallow, which cortical regions must remain intact?

Inferior and posterior regions of the motor cortex and supplementary cortical regions

If multiple motor cortex regions are damaged bilaterally, what swallowing outcome is expected?

Severe dysphagia, especially oral phase impairment

Primary function of the anterior insula in swallowing?

Coordinates oral musculature, taste, and autonomic functions

If the anterior insula is damaged, what swallowing changes may occur?

Reduced coordination of taste, oral motor control, and autonomic swallowing responses

What swallowing behaviors can the cortex modify?

Eating faster, spitting out food, and talking while chewing

Which hemisphere is more active for volitional swallowing activities?

Right hemisphere

Which hemisphere is more active for reflexive swallowing activities?

Left hemisphere

Primary role of the basal ganglia in swallowing?

Integrates sensory information about bolus properties with internal motor plans

What bolus characteristics are adjusted by the basal ganglia?

Viscosity, texture, and size

If the basal ganglia is damaged, what swallowing issue is common?

Poor adjustment of force and timing, often affecting oral phase control (Parkinson's disease)

Which brainstem structure contains the central pattern generator (CPG) for swallowing?

Medulla

What is the central pattern generator?

A neural network that produces sequential and rhythmic swallowing patterns

What is the role of the pons in swallowing?

Provides sensory and motor input from CN V (trigeminal) and VII (facial) but does not initiate or sequence swallowing

Does the pons stimulate the swallow reflex?

No

Does the pons control the swallow sequence?

No

If the pons is damaged, what swallowing issue may appear?

Sensory or motor disruption affecting oral structures but not the swallow reflex itself

Primary role of the medulla in swallowing?

Sequential control of pharyngeal and esophageal phases

Primary function of the nucleus tractus solitarius (NTS)?

Sensory component of the swallowing central pattern generator

If the NTS is damaged, what swallowing deficit is expected?

Delayed or absent swallow reflex due to impaired sensory input

Primary function of the nucleus ambiguus?

Motor component of the swallowing central pattern generator

If the nucleus ambiguus is damaged, what swallowing risk increases?

Aspiration due to reduced laryngeal closure

Primary role of the dorsal motor nucleus of the vagus?

Motor control of smooth muscle in the esophagus

If the dorsal motor nucleus is damaged, what swallowing problem occurs?

Esophageal dysmotility and impaired peristalsis

Which cranial nerve controls mastication, bolus control, and oral sensation?

Trigeminal nerve (CN V)

If CN V is damaged, what swallowing problem is likely?

Poor chewing and reduced oral bolus control

Which cranial nerve is responsible for lip seal and buccal tension?

Facial nerve (CN VII)

If CN VII (facial) is damaged, what oral preparatory issue may occur?

Anterior bolus loss and buccal pocketing

Which cranial nerve provides key sensory input for the pharyngeal swallow? (swallow trigger)

Glossopharyngeal nerve (CN IX)

If CN IX (glossopharyngeal) is damaged, what swallowing deficit may occur?

Reduced pharyngeal sensation and delayed swallow initiation

Which cranial nerve provides primary motor control for the pharynx and esophagus? (and airway protection)

Vagus nerve (CN X)

If CN X (vagus) is damaged, what swallowing risks increase?

Aspiration, poor airway protection, and esophageal dysmotility

Which cranial nerve controls bolus propulsion and tongue movement/strength?

Hypoglossal nerve (CN XII)

If CN XII (hypoglossal) is damaged, what swallowing problem is expected?

Poor bolus propulsion and oral residue

Sensory limb of the gag reflex?

Glossopharyngeal nerve (CN IX)

Motor limb of the gag reflex?

Vagus nerve (CN X)

Afferent limb of the cough reflex?

Superior laryngeal nerve branch of Vagus Nerve (CN X)

Which nerves innervate the upper esophageal sphincter (UES)?

Superior laryngeal nerve and recurrent laryngeal nerve branches of Vagus Nerve (CN X)

If UES innervation is impaired, what swallowing issue occurs?

Reduced UES opening and pyriform sinus residue

Which nerve controls esophageal peristalsis?

Vagus nerve (CN X)

What neurotransmitter mediates smooth muscle relaxation in the esophagus?

Nitric oxide

If nitric oxide signaling is disrupted, what happens to swallowing?

Impaired peristalsis and bolus transport

How does a unilateral cortical stroke typically affect swallowing?

Usually mild oral phase impairment with potential for recovery

How does a bilateral cortical stroke affect swallowing?

Severe oral phase dysphagia

How do brainstem lesions affect swallowing severity?

More severe dysphagia affecting pharyngeal and esophageal phases

Swallowing pattern commonly seen in dementia?

Intact swallow reflex with difficulty initiating the oral phase