IPHY 4440 1st Edition Lecture 2Outline of Last LectureI. Why Study Endocrinology?Outline of Current Lecture II. Patterns of Bioregulator secretionIII. Biological rhythms IV. Feedback Current LectureI. Patterns of Bioregulator secretiona. Tonic1) Steady overtime (example: thyroid hormone)b. Phasic 2) Fluctuations or pulsatile (example: LH and GnRH hormones) II. Biological Rhythms a. Diurnal or “diel” A rhythm driven by light/dark cycle (daily cycles= 24 hr)1) Day-active= diurnal (ex: sparrow >24 hr)2) Night active= nocturnal (ex. Hamster <24 hr) b. Circadian (approximately 24 hours)3) Actually a little more than or a little less than 24 hour period (>24 or <24) under constant conditions 4) Endogenous “internal” clock – must reset daily to stay with normalday-night cyclec. Ultradial (less than 24 hour) 1) Examples: breathing and heart rate (seconds)d. Lunar Cycles (28-day cycles)1) Menstrual cycles2) These cycles are not mutually exclusive e. Circannual (annual or seasonal)1) Endogenous?2) Ex: Elk seasonally reproducing 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.III. Feedback a. Negative Feedback 1) Drive system toward the set point to maintain homeostasis 2) Most important part for our systems to return back to normal3) Examples: Glucose to low in the blood increase glucose secretion glucose increases until sufficient amount stop secreting more glucose b. Positive Feedback 1) Drives system away from the set point so it disrupts homeostasis2) Long-term can be detrimental because things can spiral out of control3) Rapidly move from state x to state y4) Example: conducting a nerve signal = ion movement and an action potential open channels for more sodium to flow into cell faster depolarization when more channels open repeat process spike in action potential 5) Example: child birth with the birth being the stimulus to stop secretions and + feedback is turned off c. Feedforward1) Anticipates change2) Body is able to do things in advanced and looking for cues3) Protection of core body temperature ex: thermoreceptors in the skin 4) If likely to get really cold outside the skin thermoreceptors stimulate shivering to stay warm 5) Ex: insulin response to excess glucose in the blood, happens very quickly when glucose is detected in the lumen Clicker Question: If you inject testosterone into a male and the testosterone initially increases but eventually went back down to original level. This is an example of which feedback mechanism?Answer: Negative FeedbackClicker Question: Testosterone is produced by two testes. If you removed one testis from a man,testosterone initially decreases but eventually goes back up to its original level. This is an example of what feedback mechanism?Answer: Negative feedback because still returning system toward its set
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