CENTRAL NERVOUS SYSTEM

• SPINAL CORD - Extends from foramen magnum to 2nd lumbar vertebra - Protected by vertebral column - Spinal nerves allow movement - If damaged paralysis can occur
• Gray Matter

  • center of spinal cord
  • looks like letter H or a butterfly Posterior horns: contain axons which synapse with interneurons Anterior horns: contain somatic neurons Lateral horns: contain autonomic neurons Central canal: fluid filled space in center of cord
• White Matter

  • outside of spinal cord
  • contains myelinated fibers
  • Contains 3 columns dorsal, ventral, lateral columns
  • Ascending tracts: axons that conduct action potentials toward brain
  • Descending tracts: axons that conduct action potentials away from brain
• Spinal Nerves - Arise along spinal cord from union of dorsal roots and ventral roots - Contain axons sensory and somatic neurons - Located between vertebra - Categorized by region of vertebral column from which it emerges - 31 pairs: Organized in 3 plexuses
• Cervical Plexus (Spinal Nerves) - Spinal nerves C1-4 - Innervates muscles attached to hyoid bone and neck - Contains phrenic nerve which innervates diaphragm
• Spinal Nerves

  Brachial Plexus

  • Originates from spinal nerves C5-T1
  • Supply nerves to upper limb, shoulder, hand

  Lumbosacral Plexus

  • Originates from spinal nerves L1 to S4
  • Supply nerves lower limbs
• Protective Layers of the Brain 8.5.1.1 Meninges - protective wrapping around brain and spinal cord
• 8.5.1.1.1 Dura Mater

  - superficial - thickest layer 8.5.1.1.2 Arachnoid Mater - 2nd layer 8.5.1.1.3 Pia Mater - 3rd layer - surface of brain
• CLINICAL CORRELATION: Meningitis: infection of meninges (bacterial or viral) Epidural space: - in vertebral column between dura and vertebra - injection site for epidural anesthesia Spinal block and spinal tap: - in subarachnoid space where cerebrospinal fluid can be removed or anesthetic inject: numbs spinal nerves
• Ventricles - cavities in CNS that contain fluid Fourth ventricle: - base of cerebellum - continuous with central canal of spinal cord
• Major Parts of the Brain 8.5.2.1 Brainstem Reticular Formation Location: scattered throughout brainstem Function: regulates cyclical motor function, respiration, walking, chewing, arousing and maintaining consciousness, regulates sleep-wake cycle
• 8.5.2.1.2 Pons Location: above medulla, bridge between cerebrum and cerebellum Function: breathing, chewing, salivation, swallowing
• Midbrain Location: above pons Function: coordinated eye movement, pupil diameter, turning head toward noise
• 8.5.2.2 Cerebellum Location: below cerebrum Characteristics: - means little brain - cortex is composed of gyri, sulci, gray matter Functions: controls balance, muscle tone, coordination of fine motor movement
• 8.5.2.3 Diencephalon Located between the brainstem and cerebrum Components: - Thalamus - Hypothalamus
• 8.5.2.3.1 Diencephalon Components Thalamus

  Characteristics: largest portion of diencephalon Function: influences moods and detects pain Epithalamus: Location: above thalamus Function: emotional and visceral response to odors
• Hypothalamus

  Location: below thalamus Characteristics: controls pituitary gland and is connected to it by infundibulum

  Function: controls homeostasis, body temp, thirst, hunger, fear, rage, sexual emotions
• 8.5.2.4 Cerebrum 8.5.2.4.1 Cerebrum Characteristics - largest portion of brain Divisions: - Right Hemisphere - Left Hemisphere -separated by longitudinal fissure Lobes: frontal, parietal, occipital, temporal
• Cerebrum Components Cerebral Cortex Location: surface of cerebrum, composed of gray matter Function: controls thinking, communicating, remembering, understanding, and initiates involuntary movements Gyri: folds on cerebral cortex that increase surface area

  Sulci: shallow indentations Fissure: deep indentations Left hemisphere: - controls right side of body
• Right hemisphere: - controls left side of body - responsible for music, art, abstract ideas Corpus callosum: - connection between 2 hemispheres
• .5.3 Lobes of the Brain 8.5.3.1 Frontal Lobe Location: front Function: controls voluntary motor functions, aggression, moods, smell 8.5.3.2 Parietal Lobe Location: top Function: evaluates sensory input such as touch, pain, pressure, temperature, taste 8.5.3.3 Temporal Lobe Location: sides Function: hearing, smell, memory 8.5.3.4 Occipital Lobe Location: back Function: vision
• SENSORY FUNCTION - CNS constantly receives sensory input - We are unaware of most sensory input - Sensory input is vital of our survival and normal functions
• Ascending Tracts - pathways in brain and spinal cord

  - transmit information via action

  potentials from periphery to brain

  - each tract has limited type of sensory

  input (temp, touch, pain, etc.)

  - tracts are named that indicated origin

  and termination

  - made of 2-3 neurons in sequence
• 8.6.2 Sensory Areas of the Cerebral Cortex Primary sensory areas: - where ascending tracts project -where sensations are perceived Primary somatic sensory cortex: - general sensory area in parietal lobe - sensory input such as pain, pressure, temperature
• MOTOR FUNCTIONS 8.7.1 Descending Tracts

  • Project from upper motor neurons in cerebral cortex
  • lower motor neurons in spinal cord and brainste
  • Control different types of movements
• 8.7.2 Motor Areas of the Cerebral Cortex

  • Primary motor cortex: - frontal lobe - control voluntary motor movement
• • Premotor area:
  • Frontal lobe
  • where motor functions are organized before initiation
  • Prefrontal area:
  • motivation and foresight to plan and initiate movement
• 8.7.3 Basal Nuclei - Group of functionally related nuclei - Plan, organize, coordinate motor movements and posture Corpus striatum: deep in cerebrum

  Substantia nigra: in midbrain
• 8.7.4 Cerebellum

  • Location: below cerebrum p
  • Characteristics: means little brain
  • cortex is composed of gyri, sulci, gray matter
  • Functions: controls balance, muscle tone, coordination of fine motor movement
• 8.8 OTHER BRAIN FUNCTIONS 8.8.1 Speech -Mainly in left hemisphere Sensory speech (Wernicke’s area): - parietal lobe - where words are heard and comprehended Motor speech (Broca’s area): - frontal lobe - where words are formulated
• CLINICAL CORRELATION - Receptive Aphasia - Expressive Aphasia - Global Aphasia
• 8.8.2 Brain Waves and Consciousness - used to diagnose and determine treatment for brain disorders
• Electroencephalogram (EEG) - electrodes plated on scalp to record brain’s electrical activity Alpha waves: person is awake in quiet state

  Beta waves: intense mental activity

  Delta waves: deep sleep Theta waves: in children
• 8.8.3 Memory Encoding - brief retention of sensory input received by brain while something is scanned, evaluated, and acted up also called sensory memory in temporal lobe lasts less than a second
• Consolidated: - data that has been encoded - temporal lobe - short term memory
• Storage: - long term memory - few minutes or permanently (depends on retrieval)
• Retrieval - how often information is used
• 8.8.3.1 Types of Memory Short-term memory - information is retained for a few seconds or minutes; bits of information (usually 7) Long-term memory - can last for a few minutes or permanently

  Episodic memory - places or events Learning - utilizing past memories