Exam 2

• parts of a neuron: cell body, dendrites, axon, axon hillock, axon terminal
• neurons detect a stimulus and transduce it into an electrical signal
• central nervous system consists of the brain and spinal cord
• the brain receives and processes sensory information, initiates responses, stores, memories, generates thoughts and emotion
• the spinal cord conducts signals to and from the brain, controls reflex activities
• neurons: the functional unit of the nervous system, generates electrical signals called action potentials or nerve impulses
• glial cells: non neuronal cells that support neurons but do not gnerate nerve impulses
• what cells form mylein sheaths in the PNS?

  schwann cells
• what are the gaps between regions of the myelin sheath called?

  Nodes of Ranvier
• the myelin sheath speeds up conduction of electrical signals along the axon and conserves energy
• synapses can be chemical or electrical and inhibitory or excitatory
• excitability is the ability of a cell to send and receive electrical signals across the plasma membrane
• concentration gradient is a difference in concentration of a substance between two compartments
• Na+ concentration is 145 extracellularly and 15 intracellularly
• Cl- concentration is 100 extracellularly and 7 intracellularly
• K+ concentration is 5 extracellularly and 150 intracellularly
• potential/potential difference


  the voltage difference between two points due to separated electrical charges of opposite sign
• membrane potential


  the voltage difference between the inside and outside of a cell
• equilibrium potential


  the voltage difference across a membrane that produces a flux of a given ion that is equal and opposite to the flux due to the concentration gradient of the same ion
• resting membrane potential


  the steady potential of an unstimulated cell
• graded potential


  a potential change of variable amplitude and duration, conducted decrementally; has no threshold of refractory period
• action potential


  a brief all-or-none depolarization of the membrane, which reverses polarity in neurons; has a threshold and refractory period and is conducted without decrement
• synaptic potential


  a graded potential change in the postsynaptic neuron in response to the release of a neurotransmitter by a presynaptic terminal

  • can be depolarizing or hyperpolarizing
• depolarizing can be an excitatory postsynaptic potential or EPSP
• hyperpolarizing can be an inhibitory postsynaptic potential or IPSP
• receptor potential


  a graded potential produced at the peripheral endings of afferent neurons in response to a stimulus
• pacemaker potential


  a spontaneously occurring graded potential change that occurs in certain specialized cells
• threshold potential


  the membrane potential at which an action potential is initiated
• what establishes concentration gradients and generates a small negative potential to help keep the resting potential at -70mV?

  the Na+/K+ ATPase pump
• graded potentials occur at the dendrite and the threshold is -55mV

  • ligand-gated channels mostly
  • transient change from resting membrane potential
  • can be decremental or summation
• decremental: potential change decreases as the distance from the site of the original event increases
• summation of several small potentials can aid in integration, and in reaching threshold potential, so an action potential will occur
• actions potentials are large alterations in membrane potentials (up to 100 mV)

  • generally very rapid, can repeat
• axons contain voltage-gated channels that respond to local electrical changes
• depolarization is when the membrane potential moves from rest to a more positive value
• repolarization is when the membrane potential moves back to resting value
• hyperpolarization is when the membrane potential moves from rest to a more negative value
• wider axons = faster action potential propagation
• myelin is produced by schwann cells and oligodendrocytes
• types of synapses

  chemical and electrical