Physiology 206 Lecture 5 Outline of Last Lecture I Neurons II Glia cells III Action potentials IV Voltage Gated Ion channels Outline of Current Lecture I Axons II Action potentials III Myelin sheath IV Neurotransmitters V Presynaptic cells postsynaptic cells VI Central nervous system VII Peripheral nervous system Current Lecture 1 24 14 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 Node of Ranvier part of the axon that is directly exposed to ECF Rate of Action Potentials o Travel faster with myelinated axons then non myelinated axons Myelinated axons 0 1 seconds for a message to travel from toes to spinal cord Non myelinated axons messages travel 3 feet second o Axons with larger diameters transmit action potentials faster and axons with smaller diameters transmit action potentials slower Salutatory conduction o Action potentials jump from one nod to another Myelin sheath limits interaction of axons with ECF o Prevents large concentration difference between the inside of the axon and ECF o Allows messages to travel down an axon more efficiently Interneurons CNS are non myelinated o Have very small amount of space to transmit messages don t need speed of myelin sheath Neurotransmitters o Most common is acetylcholine Stored in axon terminals in vesicles Ach crosses synapse Reached acetylcholine receptors on target cell o Presynaptic cell sends the message o Postsynaptic cell receives the message Chemical synapse uses Ach Electrical synapse o Cells next to each other frequently have connections between the cytoplasm via gap junctions allowing ions to pass through o These cells can pass messages to each other o Occurs in many tissues In periphery the target of the message can be muscle tissue or glands Inhibited cells o It s harder to fire action potentials o Usually because the distance of the synapse is too great o Ex postsynaptic cell goes from 75mV to 80mV Excitatory synapse o When presynaptic cell make postsynaptic cell more negative to make it closer to the threshold o This way a weaker action potential is needed to send a message o Ex postsynaptic cell goes from 75mV to 65mV Cells can be presynaptic to multiple postsynaptic cells creates an extensive network Central Nervous System o Brain o Spinal Cord Peripheral Nervous System o Autonomic controls internal organs involuntary actions respiration heart rate Sympathetic Parasympathetic o Somatic controls skeletal voluntary muscles
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