Brainstem, Cranial Nerves, and Autonomic Nervous System

Cranial Nerves

Nerves that emerge directly from the brain, primarily responsible for sensory and motor functions of the head and neck.

Brainstem

The part of the brain that connects the cerebrum with the spinal cord and controls vital functions.

Rule 1

There are 2 cranial nerves in the midbrain, 4 in the pons, and 4 in the medulla.

Rule 3

The 4 motor medially located nuclei in the brainstem are numbers that divide by 12.

Autonomic Nervous System

A part of the nervous system that controls involuntary bodily functions such as heart rate and digestion.

Sympathetic tract

Not modified.

Spinothalamic

Does not cross in the BS.

DCML

Decussates in medulla.

Spinocerebellar

Axons leave BS and enter Cerebellum via cerebellar peduncles.

Spinoreticular

Ends in the reticular formation.

Corticospinal

Lateral decussates in medulla.

Corticobulbar

Axons synapse with cranial nerves.

Reticulospinal

Originates in reticular formation.

Vestibulospinal

Originates in reticular formation.

Superior Cerebral Peduncles

Connect midbrain to cerebellum, efferent.

Substantia Nigra & PPN neurons

Basal ganglia circuit.

Red Nucleus

Part of cognitive motor circuit.

Periaqueductal gray

Coordinates somatic and autonomic reactions to nociceptive input, threats and emotions.

Cranial Nerve III: Oculomotor

Motor: eye up, down, medially, raises eyelid; Parasympathetic: constricts pupil, adjusts shape of lens.

Cranial Nerve IV: Trochlear

Motor: moves eye medially and down.

Middle Cerebral Peduncle

Connects pons to cerebellum, afferent.

Cranial Nerve V: Trigeminal

Motor: chewing; Sensory: somatosensation from face, eyeball, temporomandibular joint.

Cranial Nerve VI: Abducens

Motor: abducts eye.

Cranial Nerve VII: Facial

Motor: facial expression, closes eye, protects hearing; Sensory: taste; Parasympathetic: tears, salivation.

Cranial Nerve VIII: Vestibulocochlear

Sensory: sensation of head position relative to gravity and head movements; hearing.

Pyramids

Pyramidal motor pathway.

Olives

Inferior olivary nucleus.

Inferior Cerebral Peduncle

Connects medulla to cerebellum, afferent & efferent.

Cranial Nerve IX: Glossopharyngeal

Motor: constricts pharynx; Sensory: sensation from pharynx, posterior tongue, middle ear, taste, afferent for gag & swallowing reflex; Parasympathetic: salivation; Autonomic: blood pressure and chemistry from carotid.

Cranial Nerve X: Vagus

Motor: regulates swallowing and speech, efferent for gag and swallowing reflex; Sensory: sensation from pharynx, larynx, skin in external ear canal; Parasympathetic: regulates viscera; Autonomic: regulates viscera.

Cranial Nerve XI: Accessory

Motor: elevates shoulders, turns head.

Cranial Nerve XII: Hypoglossal

Motor: moves tongue.

Reticular Formation

Integrates sensory and cortical info, regulates somatic motor activity, autonomic function and consciousness, modulates nociceptive info.

Neurotransmitters

Dopamine, GABA, Serotonin, Glutamate, Acetylcholine, Norepinephrine.

Vertebral Arteries

Supplies blood to the brain.

Basilar Artery

Supplies blood to the brain.

Brainstem Lesions

Affect vital functions.

4 Ds

Dysphagia, Dysarthria, Diplopia, Dysmetria.

Cranial Nerve Disorders

Include Bell's Palsy and Facial Synkinesis.

Case Study

52 yr old, referred to therapy due to Bell's Palsy, 5 months onset of symptoms. Left facial paralysis, pain on left side of face and increased loudness of sound in left ear.

Left facial paralysis

Loss of muscle function on the left side of the face.

Pain on left side of face

Discomfort or pain experienced on the left side of the facial region.

Increased loudness of sound in left ear

Heightened perception of sound intensity in the left ear.

Gradual onset of paralysis

Progressive development of muscle weakness over a period of time.

Lack of nociceptive and temperature info from right side of body

Absence of pain and temperature sensation on the right side of the body.

Lack of somatosensation of left side of face

Inability to perceive sensory stimuli on the left side of the facial region.

Ataxia on the left side of body

Lack of voluntary coordination of muscle movements on the left side.

Paralysis of muscles of facial expressions on the left side

Loss of movement in muscles responsible for facial expressions on the left side.

Loss of corneal reflex on the left side

Inability to blink in response to stimulation of the cornea on the left side.

Nystagmus

Involuntary eye movement that can affect balance and coordination.

Vertigo

A sensation of spinning or dizziness, often related to inner ear issues.

Nausea and vomiting when turning head

Feeling sick and potentially vomiting as a result of head movement.

Cranial nerves

Nerves that emerge directly from the brain and brainstem.

CN IV- midbrain

Cranial Nerve IV, also known as the Trochlear nerve, is associated with the midbrain.

Vestibulocochlear- medulla

Cranial Nerve VIII, responsible for hearing and balance, associated with the medulla.

CN V- pons

Cranial Nerve V, known as the Trigeminal nerve, associated with the pons.

CN IX- medulla

Cranial Nerve IX, known as the Glossopharyngeal nerve, associated with the medulla.

Knowledge of intended movements

Information about planned movements that reach the cerebellum.

The superior cerebellar peduncle

A structure that carries information from the cerebellum to the midbrain.

The contralateral pons

The pons on the opposite side of the body that transmits information to the cerebellum.

Climbing fibers originating in the inferior olivary nucleus

Fibers that provide input to the cerebellum from the inferior olivary nucleus.

Proprioceptors traveling in the dorsal spinocerebellar tract and cuneocerebellar tract

Sensory receptors that convey information about body position to the cerebellum.

Bell's palsy

A condition characterized by damage to the facial motor nucleus or facial nerve resulting in ipsilateral facial weakness.

Difficulty raising the eyelid

Inability to lift the eyelid, often associated with facial nerve injury.

Absence of taste to the entire tongue

Loss of taste sensation across the whole tongue due to nerve damage.

Sympathetic Nervous System

Part of the autonomic nervous system responsible for the body's 'fight or flight' response.

Regulation of body temperature

Mechanisms that maintain the body's temperature within a normal range.

Regulation of blood flow to skeletal muscles

Control of blood distribution to muscles during physical activity.

Sympathetic control in the head

Regulation of physiological responses in the head region by the sympathetic nervous system.

Regulation of viscera

Control of internal organs' functions by the autonomic nervous system.

Metabolism

The chemical processes that occur within a living organism to maintain life.

Epinephrine increases metabolic rate

Epinephrine, a hormone, boosts the rate of metabolism in the body.

Norepinephrine stimulates precapillary sphincters

Norepinephrine causes contraction of precapillary sphincters, reducing heat loss.

Norepinephrine

Causes vasodilation of certain vessels.

Dilation of pupil

Effect of sympathetic nervous system on the eyes.

Elevating eyelid

Effect of sympathetic nervous system on the eyes.

Salivary glands

Affected by sympathetic nervous system.

Heart rate increase

Occurs due to norepinephrine, regulated by T1-T4.

Dilation of airways

: Caused by norepinephrine and epinephrine, regulated by T1-T4.

Slowing down GI

Involves contracting sphincters (L1-L2), decreasing blood flow, and decreasing peristalsis (T5-T12).

Decreasing bowel and bladder

Involves contracting internal sphincters and decreasing wall contractions (L1-L2).

Parasympathetic Nervous System

Functions to conserve energy, decrease cardiac activity, facilitate digestion, and increase secretions in lungs, eyes, mouth, and sexual organs.

Erection of reproductive organs

A function of the parasympathetic nervous system.

Brainstem

Area of the brain involved in the parasympathetic nervous system.

CN X

Cranial nerve involved in parasympathetic functions.

CN III: Oculomotor

Cranial nerve responsible for constricting the pupil.

Bradycardia

Slowed heart rate, a function of the parasympathetic nervous system.

Increased convexity of lens

Effect of parasympathetic nervous system on airways.

Increased peristalsis

Effect of CN VII: Facial & IX: Glossopharyngeal on the stomach.

Glycogen synthesis

Function of the liver, pancreas, and kidney in the parasympathetic nervous system.

Bowel and bladder emptying

Function regulated by the sacrum (S2-S4).

Wall contractions

Involved in bowel and bladder emptying.

Relaxation of sphincter

Facilitates bowel and bladder emptying.

Erection of penis or clitoris

Function of external genitals in the parasympathetic nervous system.

Voluntary Bladder Emptying

Involves three key centers: frontal cortex, pons, and sacral spinal cord.

Horner's Syndrome

A clinical correlation for the autonomic nervous system.

Trophic Changes in skin

A clinical correlation for the autonomic nervous system.

Autonomic regulation of the heart

Dependent on parasympathetic fibers of the Vagus nerve and sympathetic fibers from the Thoracic level.

Normal autonomic function of the urinary bladder

Sympathetic efferents maintain relaxation of bladder and facilitate contraction of internal sphincter while parasympathetic efferents control bladder contractions and relaxation of internal sphincter.

Sympathetic control of the bladder

Comes from spinal cord levels L1-L2.