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Chapter 6b

Chapter 6b. Communication, Integration, and Homeostasis. Novel Signal Molecules: Calcium. Calcium as an intracellular messenger . Extracellular fluid. Electrical signal. Voltage-gated Ca 2+ channel opens. released from intracellular Ca 2+ stores. Ca 2+ in cytosol increases.

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Chapter 6b

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  1. Chapter 6b Communication, Integration,and Homeostasis

  2. Novel Signal Molecules: Calcium • Calcium as an intracellular messenger Extracellular fluid Electrical signal Voltage-gated Ca2+ channel opens. released from intracellular Ca2+ stores Ca2+ in cytosol increases. Ca2+ binds to proteins Chemical signal Other Ca2+- binding proteins Calmodulin Intracellular fluid Alters protein activity Exocytosis Movement Figure 6-15

  3. Novel Signal Molecules: Calcium Extracellular fluid Electrical signal Voltage-gated Ca2+ channel opens. Intracellular fluid Figure 6-15 (1 of 5)

  4. Novel Signal Molecules: Calcium Extracellular fluid Electrical signal Voltage-gated Ca2+ channel opens. released from intracellular Ca2+ stores Chemical signal Intracellular fluid Figure 6-15 (2 of 5)

  5. Novel Signal Molecules: Calcium Extracellular fluid Electrical signal Voltage-gated Ca2+ channel opens. released from intracellular Ca2+ stores Ca2+ in cytosol increases. Chemical signal Intracellular fluid Figure 6-15 (3 of 5)

  6. Novel Signal Molecules: Calcium Extracellular fluid Electrical signal Voltage-gated Ca2+ channel opens. released from intracellular Ca2+ stores Ca2+ in cytosol increases. Ca2+ binds proteins Chemical signal Other Ca2+- binding proteins Calmodulin Intracellular fluid Figure 6-15 (4 of 5)

  7. Novel Signal Molecules: Calcium Extracellular fluid Electrical signal Voltage-gated Ca2+ channel opens. released from intracellular Ca2+ stores Ca2+ in cytosol increases. Ca2+ binds proteins Chemical signal Other Ca2+- binding proteins Calmodulin Intracellular fluid Alters protein activity Exocytosis Movement Figure 6-15 (5 of 5)

  8. Novel Signal Molecules: Gases • Nitric oxide (NO) • Activates guanylyl cyclase • Formation of cGMP • Acts as neurotransmitter and neuromodulator in brain • Produced by endothelial cells • Diffuses into smooth muscle and causes vasodilation

  9. Novel Signal Molecules: Gases • Carbon monoxide (CO) • Also activates guanylyl cyclase and cGMP • Targets smooth muscle and neural tissue • Hydrogen Sulfide (H2S) • Targets cardiovascular system • Garlic is major source of precursors

  10. Novel Signal Molecules: Lipids • The arachidonic acid cascade produces lipid messengers Figure 6-16

  11. Novel Signal Molecules: Lipids • Leukotrienes • Role in asthma and anaphylaxis • Prostanoids • Prostaglandins • Sleep, inflammation, pain, fever • Thromboxanes • Nonsteroidal anti-inflammatory drugs (NSAIDs) help prevent inflammation by inhibiting cyclooxygenase (COX)

  12. Modulation of Signal Pathways • Specificity and competition • Agonist versus antagonist • Multiple receptors for one ligand • Alpha receptor • Vasoconstriction • Beta receptor • Vasodilation

  13. Modulation of Signal Pathways • Agonist versus antagonist An agonist also activates the receptor. An antagonist blocks receptor activity. The primary ligand activates a receptor. No response Response Figure 6-17

  14. Modulation of Signal Pathways • Target response depends on the target receptor -Receptor response 2-Receptor response -Receptor 2-Receptor Intestinal blood vessel Skeletal muscle blood vessel Epinephrine + 2-Receptor Epinephrine + -Receptor Vessel constricts Vessel dilates Figure 6-18

  15. Modulation of Signal Pathway • Up-regulation • Down-regulation • By decreasing the number of receptors • By decreasing the binding affinity • One explanation for drug tolerance • Termination mechanism • Disease and drugs

  16. Modulation of Signal Pathway • Disease and drugs target signal transduction proteins Table 6-3

  17. Control Pathways: Overview • Physiological control systems keep regulated variables within a desired range during homeostasis Regulated variable influence Within desired range Outside desired range Effectors CONTROL SYSTEM alters No action required Sensor is activated sends signal to Integrating center Figure 6-19

  18. Control Systems: Cannon’s Postulates • Nervous regulation of internal environment • Tonic control • Antagonistic control • One chemical signal can have different effects in different tissues

  19. Control Systems: Tonic Control • Tonic control of blood vessel diameter Tonic control regulates physiological parameters in an up-down fashion. Electrical signals from neuron Time Change in signal rate Increased signal rate Decreased signal rate Time Time Figure 6-20

  20. Control Systems: Antagonistic Control Antagonistic neurons control heart rate: some speed it up, while others slow it down. Parasympathetic neuron Sympathetic neuron Stimulation by parasympathetic nerves decreases heart rate. Stimulation by sympathetic nerves increases heart rate. Heart beats Heart beats Figure 6-21

  21. Control Pathways • Comparison of local and reflex control Brain evaluates the change and initiates a response. Brain Systemic change in blood pressure sensed here. LOCAL CHANGE Blood vessels REFLEX RESPONSE is initiated by cells at a distant site. LOCAL RESPONSE KEY Stimulus Integrating center Response Figure 6-22

  22. Control Pathways: Reflex Control Feedback loop STIMULUS • Steps in a reflex control pathway SENSOR or RECEPTOR AFFERENT PATHWAY Response loop INTEGRATING CENTER EFFERENT PATHWAY TARGET or EFFECTOR RESPONSE Figure 6-23

  23. Control Pathways: Receptors • Multiple meanings of the word receptor RECEPTORS can be Specialized cells or structures that convert various stimuli into electrical signals Cell membrane or intracellular receptor proteins Central receptors are in or close to the brain. Peripheral receptors lie outside the brain. Tongue (taste) Eyes (vision) Ears (hearing, equilibrium) Nose (smell) Other mechanoreceptors (pain, vibration, touch) Chemoreceptor (pH, gases, chemicals) Proprioceptor (body position) Osmoreceptor (osmolarity) Thermoreceptor (temperature) Baroreceptor (pressure) Figure 6-24

  24. Control Pathways: Response Loop • A nonbiological response loop Reflex steps 1 Water temperature is below the setpoint. STIMULUS 1 2 SENSOR or RECEPTOR Water temperature is 25° C Thermometer senses temperature decrease. 3 Signal passes from sensor to control box through the wire. AFFERENT PATHWAY 2 4 Control box is programmed to respond to temperature below 29 degrees. INTEGRATING CENTER Thermometer 7 Water temperature increases 3 Wire 5 Signal passes through wire to heater. EFFERENT PATHWAY 4 Control box 5 6 TARGET or EFFECTOR 6 Heater turns on. Wire to heater Heater 7 Water temperature increases. RESPONSE Figure 6-25

  25. Control Pathways: Response Loop Reflex steps 1 Water temperature is below the setpoint. STIMULUS 1 Water temperature is 25° C Figure 6-25, step 1

  26. Control Pathways: Response Loop Reflex steps 1 Water temperature is below the setpoint. STIMULUS 1 2 SENSOR or RECEPTOR Water temperature is 25° C Thermometer senses temperature decrease. 2 Thermometer Figure 6-25, steps 1–2

  27. Control Pathways: Response Loop Reflex steps 1 Water temperature is below the setpoint. STIMULUS 1 2 SENSOR or RECEPTOR Water temperature is 25° C Thermometer senses temperature decrease. 3 Signal passes from sensor to control box through the wire. AFFERENT PATHWAY 2 Thermometer 3 Wire Figure 6-25, steps 1–3

  28. Control Pathways: Response Loop Reflex steps 1 Water temperature is below the setpoint. STIMULUS 1 2 SENSOR or RECEPTOR Water temperature is 25° C Thermometer senses temperature decrease. 3 Signal passes from sensor to control box through the wire. AFFERENT PATHWAY 2 4 Control box is programmed to respond to temperature below 29 degrees. INTEGRATING CENTER Thermometer 3 Wire 4 Control box Figure 6-25, steps 1–4

  29. Control Pathways: Response Loop Reflex steps 1 Water temperature is below the setpoint. STIMULUS 1 2 SENSOR or RECEPTOR Water temperature is 25° C Thermometer senses temperature decrease. 3 Signal passes from sensor to control box through the wire. AFFERENT PATHWAY 2 4 Control box is programmed to respond to temperature below 29 degrees. INTEGRATING CENTER Thermometer 3 Wire 5 Signal passes through wire to heater. EFFERENT PATHWAY 4 Control box 5 Wire to heater Figure 6-25, steps 1–5

  30. Control Pathways: Response Loop Reflex steps 1 Water temperature is below the setpoint. STIMULUS 1 2 SENSOR or RECEPTOR Water temperature is 25° C Thermometer senses temperature decrease. 3 Signal passes from sensor to control box through the wire. AFFERENT PATHWAY 2 4 Control box is programmed to respond to temperature below 29 degrees. INTEGRATING CENTER Thermometer 3 Wire 5 Signal passes through wire to heater. EFFERENT PATHWAY 4 Control box 5 6 TARGET or EFFECTOR 6 Heater turns on. Wire to heater Heater Figure 6-25, steps 1–6

  31. Control Pathways: Response Loop Reflex steps 1 Water temperature is below the setpoint. STIMULUS 1 2 SENSOR or RECEPTOR Water temperature is 25° C Thermometer senses temperature decrease. 3 Signal passes from sensor to control box through the wire. AFFERENT PATHWAY 2 4 Control box is programmed to respond to temperature below 29 degrees. INTEGRATING CENTER Thermometer 7 Water temperature increases 3 Wire 5 Signal passes through wire to heater. EFFERENT PATHWAY 4 Control box 5 6 TARGET or EFFECTOR 6 Heater turns on. Wire to heater Heater 7 Water temperature increases. RESPONSE Figure 6-25, steps 1–7

  32. Control Pathways: Setpoints • Oscillation around the setpoint • Acclimatization refers to natural adaptation • Acclimation refers to induced adaptation Setpoint of function Negative feedback turns response loop off Normal range of function Response loop turns on Figure 6-26

  33. Control Pathways: Feedback Loops Initial stimulus • Negative and positive feedback • Feedforward control refers to anticipatory responses • The response counteracts the stimulus, shutting off the response loop Response Response loop shuts off Stimulus (a) Negative feedback Figure 6-27a

  34. Control Pathways: Feedback Loops • The response reinforces the stimulus, sending the varible farther from the setpoint Initial stimulus Response An outside factor is required to shut off feedback cycle. Feedback cycle Stimulus (b) Positive feedback Figure 6-27b

  35. Control Pathways: Feedback Loops Baby drops lower in uterus to initiate labor Cervical stretch causing stimulates Push baby against cervix Oxytocin release Positive feedback loop causes Uterine contractions Delivery of baby stops the cycle Figure 6-28

  36. Control Pathways: Setpoints • Circadian rhythms (a) Figure 6-29a

  37. Control Pathways: Setpoints 9:00 A.M. (b) Figure 6-29b

  38. Control Systems: Speed and Specificity Table 6-4

  39. Control Pathways: Review A simple endocrine reflex A simple neural reflex A complex neuroendocrine reflex Internal or external change Internal or external change Internal or external change Receptor Receptor Afferent path: sensory neuron Afferent path: sensory neuron Neural system integrating center Neural system integrating center Endocrine system sensor- integrating center Efferent neuron or neurohormone Efferent signal: hormone Efferent neuron Effectors Effectors Endocrine integrating center Response Response Efferent signal # 2: hormone Effectors Response Figure 6-30

  40. Control Pathways: Review • Some basic patterns of neural, endocrine, and neuro-endocrine control pathways Neurohormone reflex Simple endocrine reflex Simple neural reflex Neuroendocrine reflexes 1 2 3 4 6 5 Stimulus Stimulus Stimulus Stimulus Stimulus Stimulus Receptor Afferent neuron Neurotransmitter Efferent neuron Neuro- transmitter Neurohormone Response Target cell Blood vessel Endocrine cells Response Hormone Response Response KEY Efferent pathways Stimulus Hormone #2 Receptor (sensor) Efferent neuron Response Sensory neuron (afferent pathway) Neurotransmitter Neurohormone CNS integrating center Classic hormone Figure 6-31 Endocrine integrating center Response Target cell (effector)

  41. Control Pathways: Review Simple neural reflex 1 Stimulus Receptor Afferent neuron Efferent neuron Neuro- transmitter Target cell Response KEY Efferent pathways Stimulus Efferent neuron Receptor (sensor) Sensory neuron (afferent pathway) Neurotransmitter Neurohormone CNS integrating center Classic hormone Endocrine integrating center Target cell (effector) Figure 6-31, step 1

  42. Control Pathways: Review Neurohormone reflex Simple neural reflex 1 2 Stimulus Stimulus Receptor Afferent neuron Efferent neuron Neuro- transmitter Target cell Blood vessel Response Response KEY Efferent pathways Stimulus Efferent neuron Receptor (sensor) Sensory neuron (afferent pathway) Neurotransmitter Neurohormone CNS integrating center Classic hormone Endocrine integrating center Target cell (effector) Figure 6-31, steps 1–2

  43. Control Pathways: Review Neurohormone reflex Simple neural reflex Neuroendocrine reflexes 1 2 3 Stimulus Stimulus Stimulus Receptor Afferent neuron Efferent neuron Neuro- transmitter Target cell Blood vessel Response Response Response KEY Efferent pathways Stimulus Efferent neuron Receptor (sensor) Sensory neuron (afferent pathway) Neurotransmitter Neurohormone CNS integrating center Classic hormone Endocrine integrating center Target cell (effector) Figure 6-31, steps 1–3

  44. Control Pathways: Review Neurohormone reflex Simple neural reflex Neuroendocrine reflexes 1 2 3 4 Stimulus Stimulus Stimulus Stimulus Receptor Afferent neuron Neurotransmitter Efferent neuron Neuro- transmitter Neurohormone Target cell Blood vessel Endocrine cells Response Hormone Response Response KEY Efferent pathways Stimulus Efferent neuron Receptor (sensor) Response Sensory neuron (afferent pathway) Neurotransmitter Neurohormone CNS integrating center Classic hormone Endocrine integrating center Target cell (effector) Figure 6-31, steps 1–4

  45. Control Pathways: Review Neurohormone reflex Simple neural reflex Neuroendocrine reflexes 1 2 3 4 5 Stimulus Stimulus Stimulus Stimulus Stimulus Receptor Afferent neuron Neurotransmitter Efferent neuron Neuro- transmitter Neurohormone Target cell Blood vessel Endocrine cells Response Hormone Response Response KEY Efferent pathways Stimulus Hormone #2 Efferent neuron Receptor (sensor) Response Sensory neuron (afferent pathway) Neurotransmitter Neurohormone CNS integrating center Classic hormone Endocrine integrating center Response Target cell (effector) Figure 6-31, steps 1–5

  46. Control Pathways: Review Neurohormone reflex Simple endocrine reflex Simple neural reflex Neuroendocrine reflexes 1 2 3 4 6 5 Stimulus Stimulus Stimulus Stimulus Stimulus Stimulus Receptor Afferent neuron Neurotransmitter Efferent neuron Neuro- transmitter Neurohormone Response Target cell Blood vessel Endocrine cells Response Hormone Response Response KEY Efferent pathways Stimulus Hormone #2 Efferent neuron Receptor (sensor) Response Sensory neuron (afferent pathway) Neurotransmitter Neurohormone CNS integrating center Classic hormone Endocrine integrating center Response Target cell (effector) Figure 6-31, steps 1–6

  47. Control Pathways: Review Table 6-5

  48. Summary • Cell-to-cell communication • Electrical signals • Chemical signals • Four methods

  49. Summary • Signal pathways • Signal transduction • Amplification • Second messengers • Receptor-enzymes • G-proteins • Integrin • Ligand-gated ion channels

  50. Summary • Novel signal molecules • Calcium • NO • CO • H2S • Lipids • Modulation of signal pathways • Agonist versus antagonist • Up-regulation and down-regulation

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