neurophysiology

• Nervous system


  • One of 2 major communication systems in the body
  • Coordinates body function - movement, thought, homeostasis, etc.
  • Utilizes electrical signals (graded potentials & action potentials)
  • Utilizes chemical signals (neurocrines)
• Branches & divisions of the nervous system


  • Central nervous system (CNS)
  • Peripheral nervous system (PNS) - Sensory (afferent), Efferent (motor), Somatic division, Autonomic division (Sympathetic, Parasympathetic)
  • Enteric nervous system

  
• Glia


  Non-neuronal cells that provide support for neurons
• Neurons


  The basic signaling units of the nervous system, specialized for receiving and transmitting information via electrical and chemical means
• Neuron types


  • Interneurons
  • Afferent (sensory) neurons
  • Efferent (motor) neurons
• Sensory receptors


  • Main sensory inputs for movement are vision and proprioception
• Proprioceptors


  • Vestibular receptors
  • Kinesthetic receptors (joint, cutaneous, muscle, tendon)
• Somatic division


  • 3 basic functions: sensory reception, integration of inputs, motor output/movement
  • Movement types: reflexive, rhythmic, voluntary
• Despite the complexity of the nervous system, there are only a few basic cellular principles: signaling within neurons, signaling between neurons, and mechanisms for neural modification by experience (neural plasticity)

  
• Graded potentials


  Local, decreasing-amplitude electrical signals that originate in the input region of a neuron
• Types of graded potentials


  • Receptor potential
  • Synaptic potential (PSP)
  • End-plate potential (EPP)
• Graded potential integration


  • Summation of graded potentials at the integrative region (trigger zone, spike initiating zone)
  • Threshold for generating an action potential
• Action potentials


  All-or-none, regenerative, long-distance electrical signals that originate at the integrative region
• Information about the original sensory stimulus is conserved as it is transduced and transmitted through the nervous system
• Neurocrine secretion


  Chemical signals including neurohormones, neurotransmitters, and neuromodulators
• Action potentials


  All-or-none, regenerative, long distance signals
• Action potentials


  • Originate at integrative region (trigger zone)
  • Have a threshold
  • Do NOT summate
• Action potentials travel at 1 - 100 m/sec
• Information coding


  Information about nature of original sensory stimulus is conserved at each step (as information changes forms – i.e., is transduced)
• Neurons coordinate body functions using electrical & chemical signals
• Chemical signals


  • Neurocrine secretion
  • Neurohormone
  • Neurotransmitter
  • Neuromodulator
• Synapses


  • Neurons communicate with other cells at synapses
  • Presynaptic neuron
  • Neurotransmitter (stored in vesicles; exocytosed)
  • Postsynaptic cell
  • Ligand-gated ion channels
• Agonists and antagonists


  • Agonists are chemical substances capable of activating a receptor to produce a typical response
  • Antagonists are chemical substances that neutralize or impede the action/effect of something else
• Many drugs (clinical & recreational) work by altering transmission of information (electrical, chemical) in the body
• Somatic (alpha) motor neurons


  • Receive ~50,000 to 80,000 inputs
  • Receive both excitatory & inhibitory inputs
  • Are always active at some level -> muscle tone
• Somatic motor neurons


  • Have TONIC control over skeletal muscle
  • More excitation = contract
  • Less excitation = relax
• For most movements, the actions of groups of muscles, as well as activity of individual muscles, must be coordinated by neural pathways
• Neurophysiology is a subdiscipline of the field of physiology and has to do with the function of the nervous system
• The nervous system is one of the 2 major communication networks in the body
• Understanding the brain and how it works is complex given the number of neurons in our brain, number of connections between neurons, and diversity of neuronal types
• The nervous system is also affected by a greater number and variety of diseases and conditions than any other in the body due to its complexity and diversity
• There are a number of techniques that aid in understanding nervous system function

  
• Neural function can be understood because we've learned that there are a few key principles
• Types of cells in the nervous system


  • Glia
  • Neurons

  
• Glia


  Act as support cells
• Neurons


  Are the basic signaling unit
• Main types of glia


  • Oligodendrocytes
  • Schwann cells
  • Astrocytes
  • Microglia
• Neurons are similar to other cells of the body in many ways, but also have specialized functions such as being able to receive and transmit information which is important to their function as one of the main communication systems of the body
• Functions of the somatic nervous system


  • Control of skeletal muscles
  • Generation of 3 basic types of movements: reflexive, rhythmic and voluntary
• Somatic (alpha) motor neurons


  Control skeletal muscles