Topic 3 – HomeostasisThe ability of the body is to maintain relatively stable internal conditions even though there is continuous change in the outside world (Quote by Walter Cannon)Homeostasisis not unchanging, but rather a dynamic state of equilibrium involving many systems-Adequate blood levels of vital nutrients-Heart activity/blood pressure monitored and adjusted as needed-Wastes must not accumulate-Core body temperature must remain within range3 Essential Characteristicsof a Homeostatic Control Mechanism-ReceptoroSenses change (Stimulus) and sends info (ViaAfferent Pathway) to control center-Control CenteroDetermines set point for variable maintenanceoAnalyzes info and determines correct response-EffectoroProvides means for response (Gives Outputalong Efferent Pathway)oFeedback(Negative or Positive) allows for regulation within a range/enhanced responseNegative Feedback Mechanisms-Output reduces or shuts off stimulus (2 options)o1 hormone or neural pathway regulating a process (Negative feedback decreases secretion)oProcess regulated in opposite directions by 2 different hormones or neural pathways (Ex:Blood glucose)-Goal of negative feedback is to prevent sudden, severe changesPositive Feedback Mechanism-Response of mechanisms enhances original stimulus (Output will be further stimulated)oChange occurs in the same direction as the original response-There is a goal to be attained-Ex: Blood ClottingHomeostatic Imbalance-Most disease seen as a disturbance of homeostasis (A Homeostatic imbalance)
-Aging is associated with progressive decrease in our ability to maintain homeostasis (Greater riskfor illness)Auto= SelfNom= GovernAutonomic Nervous System (ANS)-A system of motor neurons to smooth and cardiac muscle and glands to allow response usually withoutour awareness-They can shunt blood to more needy areas-They can speed/slow heart and respiratory rates-They adjust blood pressure and body temperature-They can increase or decrease gastric secretionsEffectors-Somatic = Skeletal Muscle-ANS = Smooth Muscle, Cardiac Muscle, GlandsPathways and Ganglia-SomaticoThick, myelinated axon from spinal cord to skeletal muscleoRapid conduction of impulses (No Ganglia)-ANSo2 neuron chain
Preganglionic Neuronthat originates in brain or spinal cordTheir axons synapses with 2ndmotor neuron (Postganglionic) in ganglion outside CNSPostganglionic Neuronfound in ganglion outside CNSTheir axons sends signal to effector organ-The conduction is slowoPreganglionic axons are thin and lightly myelinatedoPostganglionic axons are thinner and unmyelinatedParasympathetic Nervous System (PNS)-Active in non-stressful situations (Rest and Digest)-Keeps body’s energy use low while regulating housekeeping activities (Digestion, Excretion)-AKA the D System (Digestion, Defecation, Diuresis) Sympathetic Nervous System (SNS)-Fight or flight systemoAlso important during exercise (Increases hear rate, Gives rapid and deep breathing, Cold sweaty skin, and dilated eye pupils)-AKA the
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- Fall '18