L21 NPB 101 - Lecture 21 •  SmartSite: – ...

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Unformatted text preview: Lecture 21 •  SmartSite: –  Lecture 21 Notes •  Review –  Endocrinology •  Announcements: –  Grades available this weekend •  Endocrinology –  Pineal –  Circadian Timing System •  Reading (Recommended): –  Relevant porAons Chapter 18 1 REV: Endocrine •  Hormone Mechanisms of AcAon –  Hydrophilic uAlizes a second messenger pathway –  Lipophilic uAlizes an intracellular pathway –  Signal AmplificaAon –  Posterior Hypothalamic Neuroendocrine SecreAon –  Anterior Endocrine controlled by Hypothalamic Releasing Factors •  Portal System •  NegaAve Feedback •  Pituitary Gland •  Growth Hormone –  Role in growth –  Role in metabolism 2 Pineal Gland 3 Pineal Gland •  Tiny, pinecone ­shaped structure •  Located in center of brain •  Secretes melatonin –  Hormone of darkness –  FuncAons •  SecreAon falls to low levels during light of day •  Helps keep body’s circadian rhythms in synchrony with light ­ dark cycle •  Promotes sleep •  Influences reproducAve acAvity, including onset of puberty •  Acts as anAoxidant to remove free radicals •  Enhances immunity 4 Circadian Timing System Circa Dies ~ About a Day 5 Spectrum of Frequencies in Physiology 6 Human Circadian Rhythms 7 Jean ­Jacques d'Ortous de Mairan, 1729 8 Circadian Rhythms •  Circadian rhythms are generated by an internal clock or pacemaker. •  They persist in the absence of cues indicaAng the Ame or length of the day. •  Circadian pacemaker located in the suprachiasmaAc nucleus (SCN), a paired structure located in the anterior hypothalamus. –  Body’s master biological clock –  Self ­induced cyclic variaAons in clock protein concentraAons within SCN bring about cyclic changes in neural discharge from SCN •  Cycle takes about a day •  Drives body’s circadian (daily) rhythms –  SCN must be set daily by external cues so body’s biological rhythms are synchronized with acAvity levels driven by surrounding environment 9 Circadian Rhythms •  The internal clock that regulates circadian rhythms is synchronized, or entrained to the daily Light ­Dark (LD) cycle and other social and environmental cues. •  Endogenous Period of the biological clock is ~ 24.2 hours •  The Aming of sleep usually bears a characterisAc relaAonship to the environment and to other circadian rhythms in the body. •  Daily changes in light intensity –  Major environmental cue used to adjust SCN master clock –  Photoreceptors in reAna pick up light signals and transmit them directly to SCN –  SCN relays message regarding light status to pineal gland 10 Visual System SCN 24-h LD Cycle Eye Retina Optic Chiasm Lateral Geniculate Visual Cortex 11 Human SCN 12 Melanopsin PhotosensiAve Ganglion Cell: A New ReAnal Photoreceptor 13 Sleep without a Biological Clock 14 Clinical Laboratory Values 15 SAmulus ­Response (SR): Time of Day Responses A. 100 75 50 25 Chemotherapeutic Agent 2 6 10 14 18 22 B. 100 75 50 25 Radiation C. 100 75 50 25 0 2 6 10 14 18 22 Bacterial Infection 2 6 10 14 18 22 Time of Day (hr) 16 Jet Lag 17 SR: Light and the RegulaAon of Melatonin Melatonin suppression  ­○ ­ Dim Light  ­○ ­ Bright Light 100 Melatonin (pg/ml) 80 60 40 20 PVH 16 18 20 22 0 2 4 6 8 10 12 0 Clock ?me (h) RHT = ReAno ­Hypothalamic Tract SCN = SuprachiasmaAc Nucleus PVH = Paraventricular Hypothalamus SC = Spinal Cord SCG = Superior Cervical Ganglion PG = Pineal Gland 18 Melatonin Afer 9 Hour Phase Shif (Berlin to San Francisco) Appropriate 40 35 30 40 35 30 Misalignment Rhythm 25 20 15 10 5 0 Rhythm 25 20 15 10 5 0 19 ...
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This note was uploaded on 11/07/2010 for the course NPB NPB 101 taught by Professor Weidner/wingfield during the Spring '08 term at UC Davis.

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