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Biol 216 4 Homeostasis 31-60.pdf

Biol 216 4 Homeostasis 31-60.pdf - How does your body...

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5/17/17 1 A. Endocrine signaling (e.g., hormones) B. Sensory transduction (involvingaction potential transmission) C. Signal transduction (molecular/cellular level) D. All of the above How does your body transmit signals? 31 Sensory transduction Stimulus (or change) is converted into an action potential (AP) Action potential is transmitted along axons towards the central nervous system (CNS) where it is integrated. Example: Sensory cells (rods and cones) in the retina convert the physical energy of light signals into electrical impulses (APs) that travelto the brain 32
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5/17/17 2 Other Sensors- Baroreceptor Baroreceptorsareneurons(or neuronalendings) in the wallsof theatria of theheart,theaorticarch,andthe carotidsinuses. are mechanical stress receptors which generate electrical impulses when stretched. Detect theamount ofstretchinvessel walls Sensitive tochangesin blood pressure Relaysignalsto thebrainstemtoelicit theappropriate response torestorehomeostasis 33 Baroreceptors Send signals (APs) to thebrainstem. Brainstem sends signals via autonomic nervous system (involuntary: heart rate, digestion, respiration rate, etc) to elicit changes Exampleof signals: Baroreceptors decrease their rateof firing (APs) when blood pressuredrops Example: When a person stands up, blood temporarily pools in the legs (particularly in the elderly due to varicose veins- enlarged/dilated ) causing a drop in venous return to the heart: causes blood pressure to fall (postural hypotension). As blood pressure falls (onstanding up) the baroreceptors are stretched less and their rate of impulse firing decreases. 34
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5/17/17 3 Baroreceptors Signals adjust the rate and force of the heartbeat Example: Sympathetic activity increases (and parasympathetic activity decreases) Sympathetic activity causes vasoconstriction of peripheral blood vessels and an increasein heart rate: causing blood pressureto increase.
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