Nervous system

• Nervous System


  • Command post of the body
  • Has control over all other organs of the body
  • Major regulatory system
  • Has connections to the rest of the body parts
  • Able to detect sensations or stimuli either inside or outside
  • Received thru sensory receptors/sense organs
  • It controls movements, specifically the part of the brain that innervates thru skeletal muscle
  • Has control over physiological processes of the body
  • Store info in form of memory
• Structures Involved


  • Brain
  • Spinal cord
  • Nerves
  • Cranial nerves (12 pairs)
  • Spinal nerves (31 pairs)
  • Ganglia
  • Sensory receptors
• Central Nervous System (CNS)


  • Brain
  • Spine
• Peripheral Nervous System (PNS)


  • Cranial nerves
  • Spinal nerves
  • Ganglia
  • Link between CNS and the rest of the body
• Functions Of The Nervous System

  • Sensory input
  • Integration
  • Homeostasis
  • Mental activity
  • Control of muscles and glands
• Sensory input


  • Sensory receptors detect numerous external and internal stimuli
  • Vision, hearing, taste, smell, touch pain, body position, and temperature
  • Any change outside or inside the body that makes us respond
  • Sensory receptors equipped with neurons
• Integration


  • Different info being processed and joined in the brain so that a response will be manifested
  • The brain and spinal cord are the major organs for processing sensory input and initiating responses
  • Responses may be immediate, stored as a memory, or ignored
• Homeostasis


  • Keeping things at equilibrium or balanced
  • Depends on the nervous system's ability to detect interpret, and respond to changes in internal and external conditions
• Mental activity


  The brain is the center of mental activity, including consciousness, memory, and thinking
• Control of muscles and glands

  • Nervous system controls the major movements of the body
  • Skeletal muscles normally contract when stimulated by the nervous system
• Neurons


  The cells that compose a nervous tissue
• CNS


  • Gray matter: Groups of cell bodies with their dendrites
  • Cortex: Gray matter on brain surface
  • Nuclei: Gray matter deep within the brain
  • White matter: Bundles of parallel axons with myelin sheaths
  • Conduction pathways and nerve tracts formed by white matter
• The brain has more gray matter content than white matter
• PNS


  • Ganglion: Counterpart of the gray matter; groups of cell bodies
  • Nerves: Counterpart of white matter; axons bundled up and their connected tissue sheaths
• Sensory or Afferent Division

  • Afferent means toward CNS
  • Receives the stimuli or information through sensory neurons
  • Conducts action potentials from sensory receptors to CNS via sensory neurons
  • No response manifested
• Motor or Efferent Division

  • Efferent means away from CNS
  • Manifests a response
  • Conducts action potential from CNS to effector organs like muscles and glands via motor neurons
• Somatic Motor Nervous System


  • Deliver action potential from the CNS to skeletal muscles
• Autonomic Nervous System (ANS)


  • Deliver action potentials from CNS to cardiac muscle, smooth muscle and glands
  • Auto moving
• Sympathetic Division


  • Fight or flight
  • Increased physical activities
• Parasympathetic Division


  • Rest and digest
• Enteric nervous system (ENS)


  • Associated with digestive tracts
• Neurons/Nerve cells


  • Basic primary cells that comprise the nervous system
  • 3 basic parts: Cell body/soma, Dendrites, Axon
  • Cell membrane, Cytoplasm, Mitochondrion, Golgi bodies, Smooth and rough ER, Ribosome, Lysosome, Nucleus, Nucleolus
  • Dendrites: Processes extending from the body, Shorter processes, Move the action potential toward the soma
• Axon


  • Longer processes
  • Relay the signal away from the body
  • The info will be directed from another neuron
  • Linked like chains
• Axon hillock


  • Where the axon is attached to
  • Part of the cell where the axon leaves
• Neurons can be attached to muscle fibers
• Neuromuscular junction


  Point of contact of a neuron to a muscle fiber
• Nissl bodies


  Clusters of rough ER within the cytoplasm of the soma
• Schwann cells


  • One of the neuroglia cells found surrounding an axon
  • It forms an insulating layer called the myelin sheath
• Myelinated axon


  When myelin sheath is present
• Multipolar neurons


  • Many dendrites
  • One axon
  • Found in the CNS
  • How motor neurons appear
  • CNS to effector organs (muscles and glands)
• Bipolar neurons


  • One axon and one dendrites
  • Some sensory neurons (retina and nasal cavity)
  • Sensory organs to CNS
• Unipolar neurons


  • One axon
  • Found in most sensory neurons
• Neuroglia/Glial cells


  • Assists neurons
  • Doesn't conduct action potentials
• Astrocytes


  • Major supporting tissue of CNS
  • Form a layer around blood vessels
  • Contribute to blood-brain barrier
• Ependymal cells


  • Line ventricles of brain
  • Produce and circulate Cerebrospinal fluid (CSF)
• Microglia


  • Help remove bacteria and cells debris from CNS
• Oligodendrocytes


  • Form myelin sheaths around axons in the CNS
  • Enclose unmyelinated axons in the CNS
• Schwann cells/Neurolemmocytes/Neurolemma Cells


  • Form myelin sheaths around axons or enclose unmyelinated axons in the PNS
• Unmyelinated axons


  Rests in indentations of oligodendrocytes in the CNS and the Schwann cells in the PNS
• Myelinated Axons


  • Specialized sheaths called myelin sheath wrapped around it
  • An excellent insulator that prevents almost all electrical current flow through the membrane