nervous system

• Nervous system


  A very complex organ system

  
• Nervous system


  • Includes brain, the nervous tissue contained within the cranium, and spinal cord, the extension of nervous tissue within the vertebral column
  • Can be divided into two major regions: Central nervous system (CNS) and Peripheral nervous system (PNS)

  
• Central nervous system (CNS)


  Brain and Spinal cord
• Peripheral nervous system (PNS)


  Nerves and ganglia outside of the brain and spinal cord

  
• Brain


  • Contained within the cranial cavity of the skull

  
• Spinal cord


  • Contained within the vertebral cavity of the vertebral column
• Dendrites


  Responsible for receiving most of the input from other neurons
• Gray matter


  Regions with many cell bodies and dendrites
• White matter


  Regions with many axons, white because axons are insulated by a lipid-rich substance called myelin
• Nucleus


  (in the CNS) A localized collection of neuron cell bodies, the center of some functions
• Ganglion


  (in the PNS) A cluster of neuron cell bodies
• Tract


  (in the CNS) A bundle of axons or fibers
• Nerve


  (in the PNS) A bundle of axons or fibers
• Basic functions of the nervous system

  • Sensation
  • Integration
  • Response

  
• Functional divisions of the nervous system

  • Somatic nervous system (SNS)
  • Autonomic nervous system (ANS)
  • Enteric nervous system (ENS)

  
• Somatic nervous system (SNS)


  Responsible for conscious perception and voluntary motor responses

  
• Autonomic nervous system (ANS)


  Responsible for involuntary control of the body, usually for the sake of homeostasis
• Enteric nervous system (ENS)


  Responsible for controlling the smooth muscle and glandular tissue in the digestive system
• Basal Nuclei


  • Initiating muscle tone in slow and coordinated activities. If control is inadequate or absent, movements are jerky, clumsy and uncoordinated.
• Thalamus


  • Sensory input from the skin, viscera and special sense organs is transmitted to the thalamus before redistribution to the cerebrum.
• Hypothalamus


  • Linked to the posterior lobe of the pituitary gland by nerve fibers and to the anterior lobe by a complex system of blood vessels. Through these connections, the hypothalamus controls the output of hormones from both lobes of the gland. Also control appetite and satiety, thirst and water balance, body temperature, emotional reactions, biological clocks or circadian rhythms.
• Midbrain


  • The upper part of the brain stem, measures about 0.8 inch (2cm) in length and connects the pons and cerebellum with the forebrain. It consists of groups of cell bodies and nerve fibers (tracts) which connect the cerebrum with lower parts of the brain and with the spinal cord. Centers for visual reflexes and control reflex movements of eye, head and neck for visual stimuli, lower auditory stimuli.

  
• Medulla oblongata


  • The most vital part of the brain since it is the control center for breathing, blood pressure and heart beat among other involuntary body functions.
• Pons

  • Contains nuclei that relay signals from cerebrum and cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expression/ sensation and posture. 2nd largest part of the brain and located near the base of the brain, towards the posterior region of the brain above the pons and medulla.

  
• Cerebellum


  • Roughly globular in shape, layered by a cerebellar cortex, contains a vermis which separates the 2 cerebral hemispheres. The anterior and posterior lobe subdivided by the primary fissure. The posterior and flocculonodular lobes are separated by the posterolateral fissures. The cerebellum is involved in balance, coordination of voluntary motor movements, mental function, vision, and motor learning.

  
• Spinal cord


  • Functions of cerebrospinal fluid: It supports and protects the brain and spinal cord, maintains a uniform pressure around these delicate structures, acts as a cushion and shock absorber between the brain and the cranial bones, keeps the brain and spinal cord moist and there may be interchange of substances between CSF and nerve cells, such as nutrients and waste products.