Physiology 206 Lecture 8 Outline of Last Lecture I Hypothalamus II Cerebral cortex III Memory IV Cerebellum V Brain stem VI Spinal cord VII Peripheral nervous system Outline of Current Lecture I Sensory receptors II Pain III Sympathetic and Parasympathetic NS IV Ganglions ganglionic cells Current Lecture 1 31 14 Receptors respond to different stimuli When a receptor that is attached to a neuron but is not a neuron itself is stimulated it undergoes a change in potential receptor potential o i e touch receptor generator potential receptor is a specialized neuron o i e pain receptor 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 When you stimulate a sensory receptor it becomes leaky to sodium the membrane potential is less negative o If it s significantly leaky it fires an action potential Label line coded o Sensory information is going to the brain is labeled to correspond to different parts of the body Referred pain o You perceive pain in a different part of the body than where it actually is Ex heart attack feel pain in left arm Pain pathways for the heart and the left arm are the same Ex appendicitis feel pain in the surface of the abdomen Sensory amplitude can tell the difference between strong and weak signals o Frequency coding strength of stimulus increases frequency of action potential increases Ex bright light and dim light o Population coding as stimulus intensity increases the number of neurons that fire increases Adaptation If you continue to stimulate a stimulus for a long time at the same intensity the stimulus stops responding o Usually occurs 30sec 1minute Phasic receptors change in stimulus strength results in rapid stimulation increase big increase in activity and then it fades back to normal rapid decrease Tonic response responses continue to be elicited even if the stimulus continues o Ex joints in body Receptive field o Area over which a stimulus can be detected o Ex touch receptive fields differ over body small in finger large in back Acuity ability to discriminate between several 2 stimuli that are very close together o High acuity able to discriminate small receptive field o Low acuity not able to discriminate large receptive field Pain o Pain receptors nociceptors o A Delta fiber 1st flash of brief intense localized pain Fast fiber pain Naked nerve endings o C fiber non adaptive throbbing pain Slow second pain Naked nerve endings Perception of pain o Analgesia not feeling pain o Endorphins similar effects to morphine Endogenous to brain Leave you insensitive to pain when released Released by drugs running etc o Battlefield analgesia in combat participants can receive injuries and not realize it till later Athletes contact sports experience this as well Nervous system o Autonomic sympathetic and parasympathetic and somatic o Efferent branch Sympathetic arousal Fight or flight In response to perceived threat danger stress Heart rate breathing vision increase o Parasympathetic Vegetative state Become sleepy blood flow to muscles decrease Sympathetic o Ganglion bundle of cell bodies o Pre ganglionic cell originates in CNS sends impulse to ganglion short o Post ganglionic cell synapses with pre ganglionic cell long o Spinal trunk ganglia sympathetic short Parasympathetic o Pre ganglionic fibers long brain organ o Post ganglionic fibers short reach from the target cell to the organ tissue
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