BIOL 112 1st Edition Lecture 25 Outline of Last Lecture I Intro to Nervous Systems II Neurons III Action Potential IV Initial Response Outline of Current Lecture V Communication between Neurons VI Types of Neurons VII Nervous Systems VIII Anatomy IX Somatic vs Autonomic Current Lecture I Communication between Neurons Action potential doesn t jump from one neuron to another Information gets from cell to cell at specialized regions called synapses info is communicated through a chemical signal not touch or fusion information only moves in one direction across a synapse Synaptic Structures Pre synaptic cell membrane These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Post synaptic cell membrane Synaptic Cleft Neurotransmitter packaged in secretory vesicles synthesized in the cell body moved down length of axon to site of use in synapse each neuron type makes only one type of neurotransmitter Synaptic Function Action potential propagates along axon of pre synaptic neuron to end at synapse action potential stimulates some of the neurotransmitter vesicles to fuse with plasma membrane releasing their contents into cleft Neurotransmitter chemicals diffuse across cleft and contact receptor molecules in post synaptic cell surface enzymes in cleft destroy neurotransmitter Post synaptic Summation Post synaptic cell receives input from many other cells both excitatory and inhibitory input Decision about whether or not post synaptic cell will initiate an action potential is made at the axon hillock Distance of synapses from the hillock influence how much depolarization or hyperpolarization affects decision spatial summation Timing of synapse activities influence decision in hillock temporal summation II Types of Neurons Three basic types sensory neurons input of chemical or physical information interneurons integrate information motor neurons output of response stimulate activity in muscles or glands combination of all three make nervous systems III Nervous Systems combinations of sensory inter and motor neurons detect stimuli integrate information about stimuli and produce appropriate response simplest arrangement Reflex Arc One of each neuron participates Sensory neuron detects stimulus e g pain Interneuron receives signal and communicates information forward to many other neurons Motor neuron receives signal from interneuron and stimulates muscle to contract Most of behavior from nervous systems consists of elaborations of these kinds of reflex arcs Brain stimulates or inhibits groups of reflexes to produce various kinds of motor behavior IV Anatomy Central Nervous System CNS Brain and spinal cord CNS cells are entirely within these structures high level integration of information input and output grey matter cell bodies axons dendrites white matter myelinated axons only Peripheral Nervous System PNS portions of neurons outside spinal cord or brain input and output Somatic and Autonomic sympathetic and parasympathetic V Somatic vs Autonomic Somatic Nervous System Sensory Neurons afferent nerves touch pain heat cold etc dorsal root ganglia on either side of spinal cord cell bodies located here motor neurons efferent nerves stimulate contraction of skeletal muscles conscious activities cell bodies are located in grey matter Autonomic Nervous System Visceral sensory neurons and motor neurons for involuntary activities in body heart beat rate muscles in digestion hormone secretion microcirculation etc Cell bodies may or may not be in spine many are located in sets of ganglia outside spinal cord not all synapses in spine Two parts Sympathetic and Parasympathetic Both connected to same structures Have antagonistic effects one stimulates the other inhibits Example heart beat rate sympathetic speeds heart up parasympathetic slows heart down Sympathetic Nervous System Epinephrine and Norepinephrine are usual neurotransmitters promotes activities that increase body energy and tension synapses in ganglia along ventral side of vertebra dilates pupils inhibits salivation accelerates heart rate relaxes bladder Parasympathetic Nervous System Acetyl choline is usual neurotransmitter Promotes activities that conserve body energy and relax body Synapses are in or near organs effected ganglia are in organs contracts pupils stimulates salivation decelerates heart rate contracts bladder