Biology 30 The Nervous System Flashcards

• Axons transmit electrical signals away from the cell body to target tissues.
• CNS (central nervous system)

  brain and spinal cord
• PNS (peripheral nervous system)

  the sensory and motor nerves that connect the CNS to the rest of the body
• Autonomic Nervous System


  A subdivision of the peripheral nervous system. Controls involuntary activity of involuntary muscles in internal organs and glands.
• Somatic Nervous System


  A subdivision of the peripheral nervous system. Enables voluntary actions to be undertaken due to its control of skeletal muscles.
• Sympathetic Nervous System


  the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations. It is a quick response.
• Parasympathetic Nervous System


  the division of the autonomic nervous system that calms the body, conserving its energy. It also deals with hormone response. It is a slow response.
• Norepinephrine

  A neurotransmitter released from sympathetic motor neurons.
• Acetylcholine


  neurotransmitter released from parasympathetic and somatic motor nerves.
• Dendrite


  a short branched extension of a nerve cell, along which impulses received from other cells at synapses are transmitted to the cell body.

  
• Cell Body


  contains the major cell organelles. Acts as a bridge allowing conduction of information between dendrites and axons.

  
• Node of Ranvier


  tiny spaces located between the areas of myelin. Impulses jump from one node to the next increasing speed.

  
• Axon Terminal (synaptic knob)


  End of axon containing neurotransmitter chemicals that allow conduction across the synapse.

  
• Schwann Cell

  insulating glial cell that wraps around the axon of a peripheral neuron, creating a myelin sheath.
• Myelin


  a fatty substance that helps insulate neurons and speeds the transmission of impulse transmissions.

  
• Axon


  a long thin extension of the cell body responsible for conducting nerve impulses away from the cell body.

  
• Nucleus


  control center of the cell.
• Neurilemma

  additional membrane on myelinated neurons (living part of the Schwann cell) coating the axon that promotes the regeneration of damaged axons.
• Sensory Receptors


  specialized cells that detect stimulus in the environment and transmit it to sensory neurons.
• Sensory Neurons (afferent neurons)


  neurons that carry incoming information from the sensory receptors to the interneurons
• Interneurons

  neurons within the brain and spinal cord that act as the connection between sensory neurons and motor neurons.
• Motor Neurons (efferent neurons)


  transmit information from the interneurons to the muscles, glands, and other organs (effectors)
• Myelinated


  axons with a myelin sheath, and therefore with increased transmission speed
• Unmyelinated


  axons without a myelin sheath, and therefore with decreased transmission speed for processing
• Synapse


  a gap that permits a neuron to pass a chemical signal to another neuron
• Reflex Arc


  simplest nerve pathway, that is interpreted by the spinal cord and therefore much quicker.
• Inhibitory Neurotransmitters


  chemical that hyperpolarizes the membrane and therefore decreases the action potential.
• Excitatory neurotransmitter

  opens sodium ion channels on the post synaptic neuron to create an action potential
• Cholinesterase


  an enzyme that breaks down acetylcholine and other neurotransmitters.
• Presynaptic Neuron


  conducts impulses toward the synapse.
• Postsynaptic Neuron


  transmits impulses away from the synapse.
• Synaptic Cleft

  the gap that separates the presynaptic neuron from the postsynaptic neuron.
• Potassium Ion Channels


  a protein channel in the axon membrane that controls movement of potassium ions out of the cell. Passive transport.
• Sodium Ion Channels


  a protein channel in the axon membrane that controls the movement of sodium ions into the cell. At rest, no sodium is flowing into the nerve cell. Passive transport.
• Action Potential


  a nerve impulse; a brief electrical charge that travels down an axon.
• Threshold


  the level of stimulation required to trigger an action potential. (-55mV)
• Resting Potential


  the state of the neuron when not firing a neural impulse. (-70mV)

  
• Sodium Potassium Pump

  a carrier protein that uses ATP to actively transport 3 sodium ions out of an axon and 2 potassium ions into the axon.
• Depolarization


  the first step once the action potential is fired where the sodium potassium pump is turned off, and sodium is rushing into the axon through sodium channels, causing the interior to become more positive (~ +40mV)

  
• Maximum Potential Reached


  the point in a nerve impulse where the interior axon charge is about +40mV. The sodium channel closes and the potassium channels open allowing potassium to diffuse out of the axon.