neurophys

• 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
• 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
• Neurocrine secretion


  Chemical signals that include 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
• 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
• 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
• Neurophysiology is a subdiscipline of the field of physiology and has to do with the function of the nervous system
• Key principles of neural function


  • The nervous system is comprised of 2 basic types of cells: glia and neurons
  • Neurons are the basic signaling unit
  • Neurons coordinate body functions using electrical and chemical signals
  • Nervous system serves 3 basic functions: sensory reception, integration, and motor output
• Glia

  • Act as support cells
  • Myelin-producing glial cells: oligodendrocytes and Schwann cells
  • Other types of glia serve important functions (e.g., astrocytes and microglia)
• 3 basic types of neurons

  • Sensory (afferent)
  • Interneurons
  • Motor (efferent)
• Excitatory and inhibitory effects

  • Sensory neurons & somatic motor neurons have excitatory effects
  • Interneurons may have excitatory or inhibitory effects, depending on the neurotransmitter released and the receptor present in the target cell
• Excitatory and inhibitory signals

  • Excitatory signals are ones in which the target cell depolarizes
  • Inhibitory signals are ones in which the target cell hyperpolarizes
• Antagonist and agonist

  • Antagonist: something that neutralizes or impedes action/effect of something else
  • Agonist: a chemical substance capable of activating a receptor to produce a typical response
• The somatic nervous system controls skeletal muscles and generates 3 basic types of movements: reflexive, rhythmic and voluntary
• 2 main types of sensory information important for movement

  • Vision
  • Proprioception
• Main proprioceptors

  • Muscle spindle
  • Golgi tendon organ
• Muscle spindle afferent

  • Ia afferent
  • Detects changes in muscle length (e.g., stretch)
• Golgi tendon afferent

  • Ib afferent
  • Detects changes in muscle force
• Electrical signals convey information within neurons about the amplitude (magnitude) and duration of sensory stimuli
• Graded potentials convey information about amplitude based on their amplitude, and about duration based on their duration
• Action potentials convey information about amplitude based on their frequency, and about duration based on the duration of the spike train
• Electrical signals are due to ion flow which changes the membrane potential in excitable cells
• Excitable cells


  • Have electrical properties that influence ion flow and changes in membrane potential
• Potential difference (V)


  Measure of potential energy, exists when positive & negative charges are separated, stored energy can be used to do work (e.g. ion flow = current)
• Current (I)


  Produced when charged particles (ions) move, requires a potential difference, defined relative to movement of positive charges (cations)
• Conductance (g)


  Capacity to transmit a current - allows flow, reciprocal (1/g) is resistance (R) - hinders flow
• Ion channels act as conductors, allowing rapid ion flow and being ion-selective
• Leakage ion channels


  Contribute to resting membrane potential