Nervous System

• Major Functions of the Nervous System

  • Receiving sensory input
  • Integrating information
  • Controlling muscles and glands
  • Maintaining homeostasis
  • Establishing and Maintaining Mental Activity
• Two Major Divisions of the Nervous System

  • Central Nervous System
  • Peripheral Nervous System
• Central Nervous System - Contains of the brain and spinal cord
• Periperal Nervous System - Contains all the nervous tissue outside the CNS including nerves and ganglia
• Peripheral Nervous System - The communication link between the CNS and the various parts of the body
• Peripheral Nervous System - carries information about the different tissues of the body to the CNS and delivers commands from the CNS to other body tissues that alter body activities
• Parts of Peripheral Nervous System

  • Sensory Division / Afferent (toward) Division
  • Motor Division / Efferent (away) Division
• Sensory Neurons - Neurons that transmit action potentials from the Periphery to the CNS
• Sensory Division - Conducts action potentials from sensory receptors to the CNS
• Skeletal muscles are voluntarily controlled
• Effectors controlled by the motor division include muscle tissue and glands
• Cardiac and Smooth Muscle, aswell as glands are involuntarily controlled
• Subdivision of Motor Division based on the type of effector being innervated

  • Somatic Nervous System
  • Autonomic Nervous System
• Somatic Nervous System - Transmits action potentials from the CNS to Skeletal Muscles
• Autonomic Nervous System - Transmits action potentials from the CNS to cardiac muscle, smooth muscle, and glands
• Autonomic Nervous system is divided into:

  • Sympathetic - Fight or Flight System (awake)
  • Parasympathetic - Vegetative Functioning (asleep)
• Enteric Nervous System - A unique part of the peripheral nervous system
• Enteric Nervous System - found in the walls of the gastrointestinal tract
• Enteric Nervous System - has both sensory and motor neurons contained wholly within the digestive tract
• Enteric Nervous System - can function without input from the Central Nervous System or other parts of the Peripheral Nervous System, although it is normally integrated with the CNS by sensory neurons and ANS motor neurons
• Two types of cells that makes up th Nervous System:

  • Neurons (Nerve cells)
  • Glial Cells
• Neurons - receive stimuli, conduct action potentials, and transmit signals to other neurons or effector organs
• 3 parts of Neurons

  • Cell body
  • Dendrites
  • Axons
• Two types of processes in the neurons

  • Dendrites
  • Axons
• Cell body - part of the neuron that contains a single nucleus
• Nucleus of the neuron is the source of information for gene expression
• Dendrites - a part of neuron that is short, often highly brancing cytoplasmic extensions that are tapered from their bases at the neuron cell body to their tips
• Dendrites - Receive information from other neurons or from sensory receptors and transmit the information towards the neuron cell body
• Axons - A single long cell process extending from the neuron cell body
• Axon Hillock - Area where the axon leaves the neuron cell body
• Axons of sensory neurons conduct action potentials away from the CNS and also conduct action potentials from one parts of the brain or spinal cord to another part
• Types of Neurons

  • Multipolar Neurons
  • Bipolar Neurons
  • Pseudo-unipolar Neurons
• Multipolar Neurons - Have many dendrites and a single axon
• Bipolar Neurons - Have 2 processes; one axon and one dendrite
• Bipolar neurons are located in some sensory organs such as retina of the eye and nasal cavity
• Pseudo-unipolar neurons - Have a single process extending from the cell body. This process divides into 2 extensions periphery, and the other extends to the CNS
• The two extensions of the pseudo-unipolar neurons functions as a single axon with small, dendrite-like sensory receptor at the periphery
• IN the pseudo-unipolar neurons, the axon receives sensory information at the periphery and transmits that information in the form of action potentials to the CNS
• Most sensory neurons are pseudo-unipolar neurons
• Glial cells / Neuroglia - supportive cells of the CNS and PNS, meaning these cells do not conduct action potentials but still can transmit