Comprehensive Neuroanatomy and Neurophysiology: Spinal Cord, Brainstem, Cranial Nerves, and Autonomic System

What is an upper motor neuron?

A neuron with its cell body located in the cerebral cortex, whose axons synapse in the brainstem or spinal cord, essential for voluntary motor control and modulating muscle tone.

What is a lower motor neuron?

A neuron with its cell body located in the brainstem or anterior horn of the spinal cord, whose axons innervate skeletal muscles.

What are the signs of an upper motor neuron lesion?

Hyperreflexia, spasticity, paresis, paralysis, spastic paralysis, clonus, and abnormal Babinski reflex.

What are the signs of a lower motor neuron lesion?

Flaccidity, paresis, paralysis, flaccid paralysis, muscle atrophy, hyporeflexia, areflexia, fasciculations, and fibrillations.

What is the blood supply for the anterior spinal arteries?

Receives blood from vertebral arteries, PICA, and branches of intercostal arteries; supplies blood to anterior 2/3 of spinal cord.

What is the blood supply for the posterior spinal arteries?

Receives blood from vertebral arteries, PICA, and branches of intercostal arteries; supplies blood to posterior 1/3 of spinal cord.

What are the essential dermatomes for testing myotomes?

C2 (back of head), C5 (tip of shoulder), C6 (thumb), C7 (middle finger), C8 (small finger), T4/T5 (nipple line), T10 (umbilicus), L1 (inguinal ligament), L4/L5 (big toe), S1 (small toe), S5 (perianal region).

What are the myotomes associated with C5 to S1?

C5 (elbow flexion), C6 (wrist extension), C7 (elbow extension), C8 (finger flexion), T1 (finger abduction), L2 (hip flexion), L3 (knee extension), L4 (ankle dorsiflexion), L5 (toe extension), S1 (ankle plantarflexion).

What is spinal shock?

A condition where functions below a lesion are depressed or lost, including reflexes, beginning immediately after traumatic spinal cord injury.

What are the symptoms of spinal shock?

Paralysis/loss of sensation, loss of somatic reflexes, loss of autonomic reflexes affecting blood pressure.

What is chronic spinal cord injury?

A condition that occurs after recovery from spinal shock when neurological deficits are stable.

What is tetraplegia?

A condition that impairs all four limbs, trunk, and pelvic organs, with lesions above C4 preventing independent breathing.

What is paraplegia?

A condition resulting from a lesion of the cord below the cervical level, preserving upper limb movement.

What is complete spinal cord injury?

Absence of all motor and sensory functions, including sacral roots, distal to the site of injury.

What is incomplete spinal cord injury?

Some retained motor or sensory function below the site of injury.

What are common complications of spinal cord injuries?

UTI, decubiti (bed sores), autonomic dysreflexia, contractures, heterotrophic ossifications, pneumonia.

What is decussation?

The crossing of nerve fibers from one side to the other, occurring between the pyramids in the medulla.

What is the function of the substantia nigra?

Movement control and dopamine production.

What is the function of the red nucleus?

Upper extremity movement control.

What is the function of the periaqueductal gray matter?

Pain processing and behavioral response to fear and anxiety.

What is the function of the inferior olivary nucleus?

Motor learning, timing, and control of ongoing movements.

What is the ascending reticular activating system?

Regulates consciousness, governs alertness, sleep, sleep-wake transitions, and attention.

What is dysesthesia?

A distorted sense of touch that is painful, burning, or itching.

What is paresthesia?

An abnormal tingling or pins-and-needles feeling.

What is allodynia?

Pain in response to stimuli that do not typically provoke pain.

What is hyperalgesia?

Excess pain in response to stimuli that typically cause pain.

What are the four functions of the cranial nerves?

1. Supply motor innervation to face, eyes, tongue, jaw, and neck muscles; 2. Transmit somatosensory information from the face; 3. Transmit special sensory information; 4. Provide parasympathetic regulation.

What regulates pupil size, lens curvature, heart rate, blood pressure, breathing, and digestion?

The autonomic nervous system.

Which cranial nerves are extensions of the CNS?

CN I and II.

Which cranial nerves are part of the PNS?

CN III to CN XII.

What is the function of CN I?

Smell/olfaction.

What is the function of CN II?

Vision.

What is the function of CN III?

Movement of extraocular muscles.

What is the function of CN IV?

Movement of extraocular muscles.

What is the function of CN V?

Both sensory and motor functions.

What is the function of CN VI?

Movement of extraocular muscles.

What is the function of CN VII?

Muscles of facial expression and taste from the anterior 2/3 of the tongue.

What is the function of CN VIII?

Hearing and balance.

What is the function of CN IX?

Taste from the posterior 1/3 of the tongue and swallowing.

What is the function of CN X?

Control of the larynx and pharynx.

What is the function of CN XI?

Movement of trapezius and sternocleidomastoid muscles.

What is the function of CN XII?

Movement of intrinsic and extrinsic muscles of the tongue.

What is anosmia?

Inability to smell.

What causes blindness and visual field abnormalities?

Lesions in CN II.

What is orthostatic hypotension?

Serious decrease of BP or HR during the first 3 minutes of standing.

What are the symptoms of orthostatic hypotension?

Dizziness, light-headedness, faint feeling, syncope.

What is postural orthostatic tachycardia syndrome (POTS)?

A condition characterized by an increase in heart rate of >30 bpm within the first 10 minutes of standing.

What is autonomic dysreflexia?

An abnormal, overreaction of the ANS to stimulation, often seen in individuals with spinal cord injuries above T6.

What are the symptoms of autonomic dysreflexia?

Elevated BP, decreased HR, pounding headache, pallor below the lesion, sweating and flushing above the lesion.

What is the role of the sympathetic nervous system?

Fight or flight response.

What is the role of the parasympathetic nervous system?

Rest and digest.

What is the enteric nervous system?

The intrinsic nervous system of the gut tube.

What is the function of the vagus nerve (CN X)?

Control of heart rate, gastrointestinal peristalsis, and sweating.

What is the afferent limb of the pupillary reflex?

CN II.

What is the efferent limb of the pupillary reflex?

CN III.

What is the function of the corneal reflex?

Protective blink response.

What is the role of the somatic nervous system?

Voluntary control of skeletal muscles.

What is the role of visceral afferent pathways?

Transmit sensory information from visceral receptors to the CNS.