physiology

• Central nervous system (CNS)


  Includes brain and spinal cord

  
• Brain


  • Made up of billions of nerve cells or neurons
  • Protected by bones of skull
• Spinal cord


  • Begins at foramen magnum and continues through vertebral foramina of first cervical to first or second lumbar vertebra
  • Made up of millions of neurons
  • Enables brain to communicate with most of body below head and neck

  
• Peripheral nervous system (PNS)


  Consists of all nerves in body outside protection of skull and vertebral column

  
• Nerves


  • Consist of axons of neurons bundled together with blood vessels and connective tissue
  • Carry signals to and from CNS
  • Classified based on origin or destination

  
• Nerves


  • 12 pairs of cranial nerves traveling back to or from brain
  • 31 pairs of spinal nerves traveling back to or from spinal cord

  
• Neurons


  • Have three main functional regions: receptive region, conducting region, secretory region

  
• Neuron types


  • Multipolar neurons
  • Bipolar neurons
  • Pseudounipolar neurons

  
• Brain


  • Soft, whitish-gray organ, anatomically continuous with spinal cord
  • Resides in cranial cavity and directly or indirectly controls most of body's functions
  • Weighs between 1250 and 1450 grams
  • Made of mostly nervous tissue, contains epithelial and connective tissues
  • Internal cavities called ventricles, filled with cerebrospinal fluid
  • Receives about 20% of total blood flow during periods of rest
• Divisions of the brain

  • Cerebrum
  • Diencephalon
  • Cerebellum
  • Brainstem

  
• Cerebrum

  • Four lobes in each hemisphere: frontal, parietal, temporal, occipital

  
• Diencephalon


  • Composed of four components: thalamus, hypothalamus, epithalamus, subthalamus
• Cerebellum


  • Structure of the cerebellum
• Brainstem


  • Structure of the brainstem
• Cranial meninges and dural sinuses

  • Structure of the cranial meninges and dural sinuses

  
• Spinal cord


  • Long tubular organ enclosed within protective vertebral cavity
  • Blends with inferior portion of brainstem
  • Ends between first and second lumbar vertebrae
  • Central canal - internal cavity continuous with brain's ventricles, filled with cerebrospinal fluid
• Major nerves


  • Cervical plexus
  • Brachial plexus
  • Lumbar plexus
  • Sacral plexus
• Major nerves of the cervical plexus

  • Phrenic nerve
• Major nerves of the brachial plexus

  • Axillary nerve
  • Musculocutaneous nerve
  • Radial nerve
  • Ulnar nerve
  • Median nerve
• Major nerves of the lumbar plexus

  • Femoral nerve
  • Obturator nerve
  • Saphenous nerve
• Major nerves of the sacral plexus

  • Gluteal nerves
  • Sciatic nerve
• Broca's area


  • Responsible for speaking ability
• Wernicke's area


  • Functions for language comprehension
• Language disorders


  • Localized in different regions of the cerebral cortex
  • Damage to these areas can explain the origin of these disorders
• Damage to Broca's area


  • Results in a failure of word formation
• Lesions in Wernicke's area

  • Lead to a failure in understanding words seen or heard
• Prefrontal association cortex


  • Its functions include planning for voluntary activity, decision-making, creativity, and developing personality traits

  
• Parietal-temporal-occipital association cortex


  • Integrates somatic, auditory, and visual sensations from these three lobes

  
• Limbic association cortex


  • Involved with motivation, emotion, and memory
• Left cerebral hemisphere


  • Excels in performing logical, analytical, sequential, and verbal tasks
• Right cerebral hemisphere


  • Excels in spatial perception and artistic and musical talents
• Electroencephalogram

  A record of postsynaptic activity of cortical neurons
• Electroencephalogram


  • Consists of various wave patterns
  • Used as a clinical tool in diagnosis of cerebral dysfunction
  • Can distinguish various sleep stages
  • Used for legal determination of brain death

  
• Basal nuclei


  • Have an inhibitory role in motor control
  • Inhibit muscle tone throughout the body
  • Select and maintain purposeful muscle activity while inhibiting useless movement
  • Monitor and control slow, sustained contractions
• Thalamus

  • A relay station
  • A synaptic integrating center for processing sensory input on its way to the cerebral cortex

  
• Hypothalamus


  • Regulates many homeostatic functions
  • Controlling body temperature
  • Controlling thirst and urine production
  • Controlling food intake
  • Controlling anterior pituitary hormone secretion
  • Production of posterior pituitary hormones
  • Controls uterine contractions and milk ejection
  • Serves as an ANS coordinating center
  • Plays a role in emotional and behavioral patterns
• Limbic system


  • Functions with the higher cortex
  • Plays a key role in emotion
  • Works with the higher cerebral cortex to control behavioral patterns
  • Has reward and punishment centers
• Neurotransmitters in pathways for emotional behavior

  • Norepinephrine, dopamine, and serotonin
• Memory


  The storage of acquired knowledge for later recall
• Memory trace


  • A neural change responsible for retention or storage of knowledge
  • Present in multiple regions of the brain