NERVOUS SYSTEM

• A major regulatory system that detects sensations and controls movements, physiologic processes, and intellectual functions

  Nervous System
• The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS)
• Central Nervous System (CNS): Consists of the brain and spinal cord.
• Peripheral Nervous System (PNS): Consists of Nerves and Ganglia
• Two subdivisions of PNS are: Sensory Afferent Division and Motor Efferent Division
• From Sensory Receptors to the CNS via sensory neurons

  Sensory Afferent Division
• From CNS to effector organs like muscles and gland via motor neurons

  Motor Afferent Division
• Two Subdivisions of the Motor Efferent Divisions

  Somatic and Autonomic Nervous Sytems
• Transmits action potentials form CNS to skeletal muscles

  Somatic Motor Nervous System
• Transmits action potentials from CNS to cardiac muscle, smooth muscle, and glands.

  Autonomic Nervous System
• mononucleated; rough ER, Golgi apparatus, mitochondria, neurofilaments, microtubules, Nissl bodies (rough ER concentrated areas)

  Cell body
• It is a short, branching cytoplasmic extensions; receive information from other neurons & transmit information toward the cell body

  Dendrites
• – a long cell process; conducts action potentials away from CNS if in motor neuron; conducts action potentials toward the CNS if in a sensory neuron

  Axon
• part of cell body where axon leaves; without Nissl bodies.

  Axon Hillock
• neuroglia surrounding an axon w/c forms a highly insulating layer called myelin sheath

  Schwann Cells
• Types of Neurons include: Multipolar, Bipolar, and Unipolar Neuron
• • Neuroglia • They account for over half of the brain’s weight • Major supporting cells in the CNS

  Glial Cells of CNS
• • major supporting tissue of CNS; forms a layer around blood vessels, contributes to blood-brain barrier

  Astrocytes
• • line ventricles of the brain, produce and circulate cerebrospinal fluid

  Ependymal
• • help remove bacteria & cell debris from CNS

  Microglia
• form myelin sheaths around axons, or enclose unmyelinated axons in the CNS

  Oligodendrocytes
• – form myelin sheaths around axons, or enclose unmyelinated axons in the PNS

  Schwann Neurolemma Cells
• Rests in indentations of the oligodendrocytes in the CNS and the Schwann cells in the PNS

  Unmyelinated Axon
• With specialized sheaths called myelin sheaths wrapped around it and is an excellent insulator that prevents almost all electric current flow thru cell membrane

  Myelinated axon
• gaps in the myelin sheath where current flows easily between extracellular fluid & axon

  Nodes of Ranvier
• a junction where the axon of one neuron interacts w/ another neuron or an effector organ such as a muscle or gland

  Synapse
• Membrane of Dendrite

  Postsynaptic membrane
• end of the axon having synaptic vesicles filled w/ neurotransmitters

  Presynaptic Terminal
• space separating the presynaptic & postsynaptic membranes

  Synaptic Cleft
• an involuntary reaction in response to a stimulus applied to the periphery and transmitted to the CNS

  Reflex
• the neuronal pathway by which a reflex occurs; the basic functional unit of the nervous system because it is the smallest, simplest pathway capable of receiving a stimulus and yielding a response

  Reflex Arc
• simplest; muscles contract in response to a stretching force applied to them

  Stretch Reflex
• which determines if the higher CNS centers are functional

  Knee-jerk Patellar
• functions to remove a limb or other body part from a painful stimulus

  Withdrawal Flexor Reflex