CNS

CENTRAL NERVOUS SYSTEM - STUDY NOTES

Presentor: Megan Nichols, MOT, OTR/L

OBJECTIVES

  • Identify area & function of parts of the CNS.

  • Recognize functional impact related to damage to CNS.

  • Identify signs and symptoms of CNS dysfunction.

WHAT IS THE ROLE OF THE CNS?

  • The Central Nervous System (CNS) plays a crucial role in various bodily functions:

    • Receive sensory information: The CNS collects sensory data from the environment and the body.

    • Process information: It interprets and evaluates the sensory data it receives.

    • Send messages to muscles & glands: The CNS instructs muscles and glands to respond appropriately.

  • Overall, it coordinates and controls all bodily functions including:

    • Movement

    • Sensation

    • Emotion

    • Vital functions

    • Cognition

WHAT MAKES UP THE CNS?

  • The CNS is primarily composed of:

    • Brain:

    • Cerebrum

    • Cerebellum

    • Spinal Cord:

    • Ends at L2 with the Cauda Equina.

BIG BRAIN VS. LITTLE BRAIN

  • Cerebellum: Small brain responsible for coordination and balance.

  • Cerebrum: Large brain responsible for higher cognitive functions.

  • Brainstem: Connects brain to spinal cord, regulates vital functions.

PARTS OF THE BRAIN

  1. Frontal Lobe

    • Functions:

      • Executive functioning

      • Voluntary movement (primary motor cortex)

      • Speech production (Broca's area - typically in the left hemisphere)

      • Influences personality, social behavior, emotional regulation, behavior control, and decision-making.

  2. Parietal Lobe

    • Functions:

      • Sensation processing (touch, pain, temperature, proprioception)

      • Spatial awareness and perception

      • Eye-hand coordination

      • Mathematical reasoning, reading/writing

  3. Occipital Lobe

    • Functions:

      • Visual processing (primary visual cortex)

      • Interpretation of color, movement, and shape

      • Depth perception

  4. Temporal Lobe

    • Functions:

      • Left hemisphere: processing of language

      • Right hemisphere: non-verbal processing

      • Both hemispheres are involved in hearing and auditory processing, memory (hippocampus), and emotion processing (amygdala).

  5. Cerebellum

    • Composed of two hemispheres and a midline structure (vermis)

    • Functions:

      • Coordination of voluntary movements

      • Balance and posture

      • Gait regulation

      • Muscle tone regulation

      • Eye movements

      • Movement precision & timing

BRAIN STEM

  • The brain stem connects the brain to the spinal cord and is responsible for controlling vital functions such as:

    • Heart rate

    • Breathing

    • Blood pressure

    • Eye movements, pupil dilation, and facial expressions

    • It contains motor and sensory pathways between the brain and body, and is responsible for reflexes.

CRANIAL NERVES

The diagram mentions the following cranial nerves:

  • CN I Olfactory

  • CN II Optic

  • CN III Oculomotor

  • CN IV Trochlear

  • CN V Trigeminal

  • CN VI Abducens

  • CN VII Facial

  • CN VIII Vestibulocochlear

  • CN IX Glossopharyngeal

  • CN X Vagus

  • CN XI Accessory

  • CN XII Hypoglossal

CIRCULATION OF THE BRAIN

  • Major arteries serving the brain include:

    • Anterior Circulation:

    • Middle cerebral artery

    • Anterior cerebral artery

    • Internal carotid artery (supraclinoid and cavernous segments)

    • Posterior Circulation:

    • Posterior cerebral arteries

    • Basilar artery

    • Vertebral artery (intracranial and extracranial)

    • Circle of Willis: A critical arterial circle that provides blood flow to the brain from multiple sources.

SOMATOSENSORY CORTEX AND MOTOR CORTEX

  • Homunculus: A visual representation of body parts and their respective areas in the motor and sensory cortices:

    • Motor Cortex (Precentral gyrus): Controls voluntary movements for various body regions such as fingers, hand, neck, face, and tongue.

    • Sensory Cortex (Postcentral gyrus): Processes sensory information from the entire body, including facial areas, genitals, and limbs.

SPINAL CORD

  • The spinal cord is a cylindrical bundle of nerves with 31 segments:

    • Cervical: 8 nerve pairs

    • Thoracic: 12 nerve pairs

    • Lumbar: 5 nerve pairs

    • Sacral: 5 nerve pairs

    • Cauda Equina: The collection of nerve roots at the lower end of the spinal cord.

  • Functions:

    • Transmits motor signals from the brain to the body.

    • Transmits sensory signals from the body to the brain.

CNS DYSFUNCTION

  • Dysfunction in the CNS can impact:

    • Motor functions

    • Sensory functions

    • Cognitive functions

    • Autonomic functions

  • Signs associated with different areas of dysfunction:

    • Frontal lobe dysfunction may present as difficulties in executive functions and emotional regulation.

    • Cerebellar dysfunction may affect coordination and balance.

    • Occipital dysfunction may lead to visual processing issues.

  • Common Causes of CNS Dysfunction:

    • Stroke (CVA)

    • Traumatic brain injury (TBI)

    • Multiple sclerosis (MS)

    • Neurodegenerative diseases (e.g., Parkinson's, ALS)

    • Tumors or infections

    • Spinal Cord Injury (SCI)

DYSFUNCTION SYMPTOMS

  • Dysmetria:

    • Defined as the inability to perform accurate, smooth movements.

    • Causes: Damage to the cerebellum.

    • Types of dysmetria:

    • Hypermetria: Overshooting movements when directed at a target.

    • Hypometria: Undershooting movements when directed at a target.

    • Functional Impact: Poor accuracy in goal-directed tasks.

    • Testing Methods:

    • Finger-to-nose test

    • Heel-to-shin test

    • Point-to-point reaching tasks

DYSFUNCTION SYMPTOMS CONTINUED

  • Dysdiadochokinesia:

    • Defined as the inability to perform rapid, alternating movements smoothly.

    • Causes: Cerebellar dysfunction.

    • Functional Impact: Impaired coordination in tasks requiring quick alternating motions (e.g., buttoning, writing, speaking).

    • Diagnostic Methods:

    • Patient flips hand quickly on a surface

    • Patient taps foot quickly

    • Movement of turning a doorknob

OTHER MOVEMENT SIGNS & SYMPTOMS

  • Akinesia: Loss of voluntary movement.

  • Bradykinesia: Slowness of movement.

  • Chorea: Involuntary, unpredictable body movements.

  • Athetosis: Involuntary movements that are slow and writhing.

  • Dystonia: Sustained or repetitive muscle contractions.

  • Ataxia: Lack of voluntary coordination of muscle movements.

  • Apraxia: Inability to execute learned movements despite having the desire and physical capability to perform them.

VISUAL SYMPTOMS

  • Hemianopia: Loss of vision in half of the visual field.

  • Quadrantanopia: Loss of vision in a quarter of the visual field.

  • Diplopia: Double vision.

  • Nystagmus: Involuntary eye movement, often resulting in reduced vision.

APHASIA

  • Wernicke's Aphasia (Fluent):

    • Speech: Fluent with normal rate and intonation, but nonsensical speech (often referred to as "word salad").

    • Comprehension: Impaired.

    • Repetition: Impaired.

    • Awareness: Usually poor insight into deficits.

  • Broca's Aphasia (Non-Fluent):

    • Speech: Disfluent, effortful, and broken phrases with decreased vocabulary.

    • Comprehension: Relatively preserved.

    • Repetition: Impaired.

    • Awareness: Good insight, often frustrated by difficulty speaking.

AGNOSIA

  • Defined as the inability to recognize or interpret sensory information despite intact sensory function.

  • Types include:

    • Visual Agnosia: Inability to recognize objects by sight.

    • Prosopagnosia: Inability to recognize familiar faces.

    • Auditory Agnosia: Inability to recognize sounds (e.g., phone ringing, voices).

    • Tactile Agnosia: Inability to recognize objects by touch.

    • Anosognosia: Lack of awareness of one's own deficits.