Exam 4 Study Guide LECTURES 26 30 The Nervous System Name the 2 major divisions of the nervous system o Central Nervous system Brain and spinal cord control center o Peripheral Nervous system Includes all neural tissue outside of CNS sensory division motor division Includes ANS autonomic nervous system o Involuntary regulation o Smooth muscle cardiac muscle glands and adipose tissue SNS somatic nervous system o Voluntary o Controls skeletal muscle contractions BOTH ANS SNS ARE APART OF MOTOR DIVISION PART OF PNS Describe the general process of the nervous system from stimuli to motor response o Afferent Association Efferent neurons pathways Receptors Effectors Sensory information with afferent division information processing motor commands within efferent division SNS ANS Name the two primary types of cells in the nervous system Which cells are the basic unit of the nervous system Name the 3 types of supporting cells in the nervous system o Conducting Cells o Supporting cells o Conducting cells o Schwann Cells o Satellite cells o Neuroglia What is the general function of supporting cells o Provide support for neurons Framework What are the 2 Functions of Schwann cells Assist segregate insulate neurons o Form myelin sheath around peripheral axons One schwann cell myelinates one internode o Participate in repair of damaged nerves Discuss the repair mechanism for a damaged nerve o Myelin and axon are damaged o Schwann cells do not degenerate and proliferate along original path of o Macrophages move in and remove degenerating debris distal to injury axon site o Axon grows into site of injury and distally o Schwann cells wrap around axon and re myelinates What is the function of Satellite cells o Surround cell body of neuron o Act to regulate environment surrounding neuron Where are Satellite cells found o PNS What are the 4 types of neuroglia o Astrocytes o Microglia o Ependymal o oligodendrocytes o Structure and function of each Astrocytes Largest of neuroglia Most numerous Maintains blood brain barrier Control chemical environment around neruons Form scar tissue after CNS injury Microglia Mobile cells Clean up crew o Scavengers of CNS Numbers increase with injury Ependymal Oligodendrocytes Small cells Provide structural framewok Form epithelium known as ependymal Assist in producing monitoring and circulating CSF Stabilizing positions of axons Produce myelin o Membranous wrapping that surrounds axon Approximately how many neurons are in the body Name the 3 functional classes of neurons o 200 billion o Afferent Sends signals from receptors to CNS o Association Within CNS o Efferent Sends signals from CNS to effectors Describe the general structure of a neuron o Cell body Usually located in CNS Protected by bones o Processes Extend out from cell body Can be very long o Cell body Nuclus Cytoplasm surrounding nucleus is called PERIKARYON Cytoskeleton o Dendrites Short and thick with many brances Many per neuron Sensory process Dendritic spines Extensions like thorns Surface area o Axon Carries information away from cell body Axolemma Plasma membrane of axon May be myelinated Arise from axon hillock Generally unbranched until distal end o Telodendria Branching filaments at the end of axon Terminate in bulbous ends called SYNAPTIC TERMINALS which are part of synapse Describe a synapse o Synapse Specialized site where neuron communicates with another cell Each synapse involves a pre and post synaptic cell Neurontransmitter chemicals are released into synaptic cleft Generally pre synaptic cells is always a neuron Post synaptic cell can vary Other neurons Muscles Glands May be multi branched Describe the structure and function of myelin o Segmented sheath covering some nerves Breaks called nodes of Ranvier o Protects and electrically insulates fibers o Conduction speed o PNS Schwann cells o CNS oligodendrocytes What is the transmembrane potential o The unequal charge distribution cytosol has a slight negative charge while the slight excess of positive charges attracted just outside the plasma membrane What property of the plasma membrane is critical to a transmembrane potential o Selectively permeable portion Describe the resting potential of a cell o Extracellular fluid contains high concentrations of Positively charged sodium ions Negatively charged chloride ions o Cytosol contains high concentrations of Positively charged potassium ions Negatively charged proteins o Ions cannot freely cross plasma membrane Can only cross through channel proteins or by active transport What is the resting potential of a neuron in millivolts What are two factors that influence a neurons resting potential value o 70 mV o NA K balance o Greater abundance of Pr in cytosol o What common ions are found within the cytoplasm at resting potential What common ions are found in the extracellular fluid Which structures are crucial for the development of a graded potential K Cr o Na o Cl o The channels Chemically gated Voltage gated Mechanically gated Describe process of depolarization during a graded potential o Any decrease in resting potential 1 at normal resting potential Na gated channels are closed 2 when membrane is exposed to binding chemical Na gates 3 Na rush into cell 4 influx of positively charged ions changes transmembrane open potential Describe how a depolarization spreads along the plasma membrane o Na spreads out across inner surface of the membrane What is hyperpolarization What causes this o Degrease in resting potential K channels open Positive charges leave cytoplasm What are 4 factors that are important to remember when talking about graded potentials Transmembrane potential is most affected at site of stimulation Change in transmembrane potential is spread passively through o Site o Spread local currents o Change Graded change may involve either depolarization or hyperpolarization depending on gated channel involved o strength the stronger the stimulus the greater the change in transmembrane potential and larger is the area affected Discuss the process of an action potential o Depolarization to threshold Initially at resting potential All action potentials begin with a graded potential Depolarization be sufficient to open voltage gated channels o Activation of Na channels Coltage gated Na channels open Na rush into cytoplasm Rapid depolarization Inner membrane now contains more positive ions than negative o Inactivation of Na channels and activation of K channels Transmembrane potential