C4 SYNAPSE

• difference in electrical charge between the inside and outside of cell

  membrane potential
• intracellular electrodes, tips are less than one-thousandth of a millimeter in diameter

  microelectrodes
• positively and negatively charged

  ions
• specialized pores where Na and K ions are maintained

  ion channels
• 2 pressure on Na ions

  electrostatic pressure

  pressure from random motion
• transporters performed by mechanisms in the cell membrane that continually exchange 3 Na ions inside the neuron for 2 K ions outside

  sodium-potassium pumps
• mechanisms in the membrane of a cell that actively transport ions or molecules across the membrane

  transporters
• decrease the resting membrane potential

  depolarize
• increase the membrane potential

  hyperpolarize
• postsynaptic depolarizations, increase the likelihood that the neuron will fire

  excitatory postsynaptic potentials
• postsynaptic hyperpolarization, decrease the likelihood that the neuron will fire

  inhibitory postsynaptic potential
• both EPSP and IPSP

  graded potentials
• once believed that action potentials were generated here, conical structure at the junction between the cell body and axon

  axon hillock
• actions potentials were actually generated in adjacent section of the axon

  axon initial segment
• sum of depolarization and hyperpolarization reaching the axon initial segment at any time is sufficient to depolarize the membrane to a level referred to as

  threshold of excitation
• massive but momentarily, lasting for 1 millisecond

  action potential
• they either occur to their full extent or do not occur at all

  all-or-none response
• adding or combining a number of individual signals into one overall signal

  integration
• neurons integrate incoming signals in 2 ways

  over space

  over time
• shows how local EPSPs that are produced simultaneously on different parts of the receptive membrane sum to form greater EPSP

  spatial summation
• shows how postsynaptic potentials produced in rapid succession at the same synapse sum to form a greater signal

  temporal summation
• roberto garcia d'orta referred to himself as a great lizard frozen in a dark, cold, strange world, he suffered from

  parkinson's disease
• substantia nigra produces chemical called

  dopamine
• the ___ is about -70mv

  resting potential
• 2 factors pressure Na ions to enter resting neurons: random ___ and electrostatic pressure

  motion
• when a neuron is in a resting state, there is a greater concentration of ___ ions outside the neuron

  sodium
• the ___ channels are open in a resting neuron

  potassium
• ions pass through neural membranes via specialized pores called ___

  ion channels
• the firing of neurons releases chemicals at their button terminals called ___

  neurotransmitters
• neurotransmitters typically have one of the 2 effects on postsynaptic neurons: they either depolarize them or ____

  hyperpolarize
• ion channels that open or close in response to changes in the level of the membrane potential

  voltage-activated ion channels
• brief period of about 1 to 2 milliseconds after the initiation of an action potential during which it is impossible to elicit a second one

  absolute refractory period
• period during which it is possible to fire the neuron again but only by applying higher-than-normal levels of stimulation

  relative refractory period
• action potentials do not grow weaker as they travel along the axonal membrane

  nondecremental
• if electrical stimulation of sufficient intensity is applied to the terminal end of an axon, an action potential will be generated and will travel along the axon back to the cell body

  antidromic conduction
• axonal conduction in the natural direction, from cell body to terminal buttons

  orthodromic conduction
• gaps between adjacent myelin segments

  nodes of ranvier
• transmission of action potentials in myelinated axons, to skip or jump

  saltatory conduction
• neurons that synapse on skeletal muscles

  motor neurons
• first proposed by Hodgkin and Huxley in 1950s

  Hodgkin-Huxley Model