Gen ana

• Nervous system


  Composed of specialized cells whose function is to receive sensory stimuli and to transmit them to effector organs, whether muscular or grandular

  
• Components of the nervous system

  • Central nervous system
  • Peripheral nervous system
  • Autonomic nervous system
• Central nervous system (CNS)


  The brain and the spinal cord are the main centers where correlation and integration of nervous information occur

  
• Central nervous system (CNS)

  • Both the brain and spinal cord are covered with meninges and are suspended in cerebrospinal fluid
  • Composed of excitable cells called neurons
  • With specialized tissue called neuroglia
  • Gray matter consists of nerve cells embedded in neuroglia
  • White matter consists of nerve fibers embedded in neuroglia
  • White color is due to lipid material in myelin sheath of nerve fibers

  
• Peripheral nervous system


  The cranial and spinal nerves conduct information to and from the central nervous system

  
• Components of the peripheral nervous system

  • Cranial nerves: 12 pairs
  • Spinal nerves: 31 pairs

  
• Autonomic nervous system


  Concerned with the innervation of involuntary structures such as the heart, smooth muscle and glands
• Components of the autonomic nervous system


  • Sympathetic
  • Parasympathetic
• Sympathetic


  Its activities prepare the body for an emergency
• Parasympathetic


  For conservation and restoring energy
• Spinal cord


  Cylindrical structure, located within the vertebral canal
• Spinal cord


  • Begins in foramen magnum of the skull, where it is continuous with medulla oblongata of the brain
  • Terminates inferiorly in the lumbar region, upper border of L2; at birth is L3
  • Tapers off into conus medullaris
  • Has prolongations of the pia mater: filum terminale
  • Surrounded by 3 Meninges: Dura mater, arachnoid mater, pia mater
  • Has two (2) enlargements: Cervical enlargement, lumbar enlargement
  • With an inner core of Gray matter, surrounded by an outer covering of White matter

  
• Principles of the brain

  • Brain stem
  • Cerebellum
  • Diencephalon
  • Cerebrum

  
• Brain stem


  Continuous with spinal cord and consists of medulla oblongata, pons and midbrain
• Cerebellum


  "Little brain," located posterior to the brain stem
• Diencephalon


  Located superior to the brain stem, it consists of thalamus and hypothalamus

  
• Cerebrum


  Spread over the diencephalon like a mushroom cap and occupy most of the cranium
• Protective coverings of the brain

  • Dura mater: Outer, has three extensions that separate the brain
  • Arachnoid mater: Middle
  • Pia mater: Inner

  
• Falx cerebri


  Separates the two hemispheres of the cerebrum
• Falx cerebelli


  Separates the two hemispheres of the cerebellum
• Tentorium cerebelli


  Separates the cerebrum from the cerebellum
• Brain blood flow


  • Blood flows to the brain mainly via blood vessels that branch from the Circle of Willis, at the base of the brain
  • Adult: Brain represents only 2% of the total body weight but consumes about 20% oxygen and glucose used at rest
  • Interruption of blood flow for 1-2 minutes impairs the neuronal function
  • Total deprivation of O2 for 4 minutes causes permanent injury
  • The blood brain barrier - protects the brain cells from harmful substances and pathogens by preventing passage of many substances from the blood to brain tissue
• Cerebrospinal fluid (CSF)


  A clear colorless liquid that protects the brain and spinal cord against the chemical and physical injuries

  
• CSF contributes to homeostasis

  • Mechanical protection: serves as a shock absorbing medium
  • Chemical protection: provides an optimal chemical environment for accurate neuronal signaling
  • Circulation: medium of exchange of nutrients and waste products
• Circulation of CSF


  1. CSF from choroid plexus in lateral ventricles

  2. Flows through 3rd ventricle through foramen of monro; more CSF added

  3. Flows through the aqueduct of Sylvius

  4. Passes the midbrain

  5. Fourth ventricle; more CSF added

  6. CSF enters the subarachnoid space through 3 openings in the 4th ventricle: median aperture of Magendie and paired internal aperture of Luschka

  7. CSF circulates in subarachnoid space of the brain and the spinal cord
• Brain stem


  Part of the brain between the spinal cord and the diencephalon

  
• Medulla oblongata


  • Continuation of the superior part of the spinal cord
  • Behind the foramen magnum and extends to inferior pons
  • Within it are all ascending (sensory) and descending (motor) tracts
  • Contains nuclei that receive sensory input from or provide motor output to five of the 12 cranial nerves
• Pons


  • Lies directly superior to the medulla and anterior to the cerebellum
  • 2-5 cm in length
  • Consists of nuclei and tracts
  • It is a bridge that connects the parts of the brain with one another
  • It has longitudinal axons, which are parts of ascending sensory tracts and descending motor tracts
  • It has transverse axons within paired tracts that connect the right and left sides of the cerebellum
  • Has important nuclei that help control breathing: Pneumotaxic area and Apneustic area
  • Contains associated with 4 pairs of cranial nerves

  
• Midbrain


  • Extends from pons to diencephalon
  • About 2.5 cm long
  • Like medulla it contains both tracts and nuclei
• Reticular formation


  • Also contained in the brainstem
  • Net-like arrangement of small areas of gray matter interspersed among threads of white matter
  • Main sensory function: alerting the cerebral cortex to incoming sensory signals
  • Responsible for maintaining consciousness and for awakening from sleep
• Cerebellum


  • The second largest part of the brain
  • Shaped like a butterfly
  • Has central constricted areas, "vermis"
  • Occupies the inferior and posterior aspect of the cranial cavity
  • It is posterior to the medulla and pons and inferior to the posterior part of the cerebrum
  • Separated from cerebrum by: Transverse fissure, Tentorium cerebelli

  
• Cerebellum


  • Main function: evaluate how well movement initiated by motor areas in the cerebrum are carried out
  • Has cerebellar hemispheres: Anterior lobe - for conscious movement of skeletal muscle, Posterior lobe - for conscious movement of skeletal muscle, Flocculonodular lobe - for sense of equilibrium
• Diencephalon


  Extends from the brain stem to the cerebrum and surrounds the 3rd ventricle
• Components of the diencephalon


  • Thalamus
  • Hypothalamus
  • Epithalamus
  • Subthalamus
• Thalamus


  • Principal relay station for sensory impulses
  • Allows crude perception of sensation such as pain, temperature, and pressure
  • Plays a role in awareness and acquisition of knowledge termed as cognition

  
• Thalamus


  • Medial geniculate nucleus: relays auditory impulses
  • Lateral geniculate nucleus: receives visual impulses basal ganglia
  • Anterior nucleus: concerned with emotions and memory

  
• Hypothalamus


  Controls body activities and a major regulator of homeostasis
• Regions of the hypothalamus


  • Mammillary region
  • Tuberal region
  • Pre optic region
  • Supraoptic region
• Functions of the hypothalamus

  • Control ANS: it integrates activities of ANS which regulates contraction of smooth muscle and cardiac muscle and secretions of glands
  • Control of pituitary gland: regulates release and storage of hormones
  • Regulates emotional and behavioral pattern: regulates feelings, aggression, pain and pleasure and behavioral pattern related to sexual arousal
  • Regulates eating and drinking: it has a feeding center and thirst center
  • Control of body temperature
  • Regulates circadian rhythm and states of consciousness: regulates patterns of sleep
• Epithalamus


  Small region superior and posterior to the thalamus