Central nervous system | Neuromuscular system

Upper motor neuron units

Definitions

Upper motor neuron units: Network of neurons in which cell bodies originate in the cerebral cortex (brain), brainstem, and spinal cord. Characteristics of disease processes that are upper motor units are weakness, hyperreflexia, and hypertonia.

Anatomy of brain

Brain is divided into two (2) hemispheres divided externally by longitudinal fissure and internally by corpus callosum
- Right hemisphere:
  - Spatial awareness
  - Emotional processing
  - Facial recognition
  - Creativity
  - Abstract thought
  - Controls left side of body
- Left hemisphere
  - Language
  - Logic and reasoning
  - Analytical thinking
  - Controls right side of body

Brain is divided into six (6) lobes with distinct characteristics which work collectively to assist functional:
- Frontal lobe:
  - Executive function
  - Voluntary movement
  - Problem solving
  - Learning
  - Behavior
  - Impulse control
  - Personality
  - Social behavior
  - Expressive language (Broca’s area)
- Parietal lobe:
  - Awareness of somatic sense- touch, pain, temperature, pressure, vibration
  - Processing somatic sensation- analyzing, recognizing, and development of memory of somatic sense
  - Spatial and body awareness
  - Coordination of visual, auditory, and somatosensory stimuli
- Temporal lobe:
  - Hearing
  - Receptive language (Wernicke’s area)
  - Memory
    - Declarative: memory regarding names of person, places, or things
    - Procedural: memory of how to perform activities such as brushing teeth, putting on making-up, etc
- Occipital lobe:
  - Awareness of visual stimuli
  - Processing of visual stimuli
- Cerebellum:
  - Motor learning
  - Coordinate movement
  - Balance and equilibrium
  - Proprioception sense
  - Maintain posture
- Brainstem:
  - Ascending and descending tracts are located in brainstem
  - Heart rate and respiration rate
  - Sleep and wake cycles
  - Digestion
  - Body temperature
  - Vomiting
  - Swallowing

Other important brain structures

Thalamus
- Receives sensory information from the body
- Sends motor information to the body
- Assists with memory processing
Hypothalamus
- Maintains homeostasis within the body by regulation of hormones
Basal ganglia
- Initiation of movements
- Assists with maintaining posture and muscle tone
- Assists with controlling voluntary movements

Arterial circulation of the brain

Circle of Willis

Network of arteries that provide blood supply to the brain
Major arteries
- Anterior cerebral artery (ACA)
  - Supplies frontal, pre-frontal, and supplementary motor cortex as well as circulation to primary motor and sensory cortex
  - Injury to the ACA can cause hemiparesis with weakness of lower extremity > upper extremity with sparing of face, apraxia, abulia, akinetic mutism, urinary incontience
- Anterior communicating artery
  - Blood supply that connect the left and right ACA
  - Injury to anterior communicating artery can cause visual disturbances, memory deficits, cognitive impairment, severe headache, altered mental status, and impaired executive function
- Middle cerebral artery
  - Blood supply to the frontal, temporal, parietal, and deeper structures
  - Injury to the middle cerebral artery can cause hemiparesis with weakness of upper extremity >lower extremity; innervates both Broca’s area and Wernicke’s area, neglect
- Internal carotid artery
  - Provides oxygenation to the brain
  - Injury can lead to blurred vision, confusion, memory loss, hemiparesis, or sudden death
- Posterior cerebral artery
  - Supplies blood to occipital and temporal lobes
  - Injury can cause visual field loss, visual impairment, headache, confusion, and memory impairments
- Posterior communicating artery
  - Connects the internal carotid artery to the posterior cerebral artery
  - Injury can cause vi field loss, ptosis, diplopia, headache, confusion, memory impairment, hemiparesis

Other Important arteries of brain

Basilar artery
- Supplies: Brainstem, occipital lobe, cerebellum, thalamus, medial temporal lobes
- Functions: Supports autonomic regulation
- Injury Signs: Hemiparesis or quadriparesis, facial paralysis, dizziness, headache, dysarthria
- Involvement: Combines with vertebral artery → vertebrobasilar system → damage to both can cause locked-in syndrome
Vertebral artery
- Supplies: Brain and spinal cord
- Injury Signs: Headache, neck pain, dysarthria, dysphagia, seizures, impaired coordination, sensory/motor deficits to face and body
- Involvement: Joins basilar artery → vertebrobasilar system → dual injury may result in locked-in syndrome
Posterior inferior cerebellar communicating artery (PICA, Wallenburg syndrome, or Lateral medullary syndrome)
- Supplies blood flow to the medulla, fourth ventricle, and cerebellum
- Injury can cause diplopia, ptosis, facial pain, vertigo, slurred speech, hoarseness, balance deficits, sensory deficits on same side face and contralateral body

Definitions

Locked-in syndrome: Paralysis of all voluntary muscles with the exception of eye movement remains intact. The individual remains conscious but is unable to speak or move.