Bio212 Worksheet 8

• Neuron is a cell that transmits nerve impulses
• Brain vs. ganglia:

  • Brain is the central organ of the nervous system in vertebrates
  • Ganglia are clusters of nerve cell bodies in the peripheral nervous system
• Components of a vertebrate's central nervous system:

  • Brain and spinal cord
• Nervous system processing to kick a ball:

  • Sensory input: receiving information from the environment
  • Sensory neurons: transmit sensory input to the central nervous system
  • Integration: processing sensory input in the brain
  • Interneurons: connect sensory and motor neurons
  • Motor output: signal sent to muscles
  • Motor neurons: transmit signal to muscles
  • Effector cells: muscle cells that carry out the response
• Membrane potential is the voltage across a cell membrane

  • Resting potentials for mammalian neurons range from -40mV to -90mV
  • Cytosol is more negative for a cell at resting potential
• Resting potential of a neuron is controlled by chemical forces through ion pumps and by electrical forces through ion channels
• Cytosol becomes more negative during hyperpolarization and less negative during depolarization
• Voltage-gated ion channels open and close in response to changes in membrane potential, while ligand-gated ion channels open and close in response to specific molecules binding to them
• Graded potential is a small change in membrane potential, while action potential is a large change that allows for long-distance signaling
• Steps for generating an action potential:

  • Resting state
  • Depolarization
  • Repolarization
  • Hyperpolarization
• Action potentials move along an axon through depolarization of adjacent regions

  • Action potential travels in one direction due to the refractory period
• Myelin sheaths increase conduction speed by insulating the axon and forcing the action potential to jump between nodes of Ranvier (saltatory conduction)
• Chemical synapse works by releasing neurotransmitters from the presynaptic neuron to the postsynaptic neuron, leading to excitatory or inhibitory postsynaptic potentials
• EPSP must reach the threshold potential to produce an action potential
• Nerve is a bundle of axons in the peripheral nervous system

  • Functions of glial cells include supporting and protecting neurons
• Cephalization is advantageous to bilaterally symmetrical organisms as it concentrates sensory organs and nervous tissues at the anterior end
• Cerebrospinal fluid cushions the brain and spinal cord and is found in the ventricles of the brain and the central canal of the spinal cord
• Knee-jerk reflex is a monosynaptic reflex that involves sensory neurons from the knee joint synapsing directly with motor neurons to produce a quick response
• Optic nerves are examples of cranial nerves
• Motor system (somatic nervous system) controls voluntary movements, while the autonomic nervous system controls involuntary actions

  • Sympathetic division prepares the body for action, while the parasympathetic division conserves energy and promotes rest
• Difference between ocellus, compound eye, and single-lens eye:

  • Ocellus: simple eye found in invertebrates like flatworms
  • Compound eye: found in insects like bees
  • Single-lens eye: found in vertebrates like humans