chapter 6b communication, integration, and homeostasis
TRANSCRIPT
Chapter 6b
Communication, Integration,
and Homeostasis
Figure 6-15
Novel Signal Molecules: Calcium
• Calcium as an intracellular messenger Extracellular
fluid
Intracellularfluid
Electricalsignal
released fromintracellularCa2+ stores
Ca2+ binds toproteins
CalmodulinOther Ca2+-
binding proteins
Alters proteinactivity
Exocytosis Movement
Chemicalsignal
Ca2+ in cytosolincreases.
Voltage-gated Ca2+ channelopens.
Novel Signal Molecules: Calcium
Figure 6-15 (1 of 5)
Extracellularfluid
Intracellularfluid
Electricalsignal Voltage-gated
Ca2+ channelopens.
Novel Signal Molecules: Calcium
Figure 6-15 (2 of 5)
Extracellularfluid
Intracellularfluid
Electricalsignal
released fromintracellularCa2+ stores
Chemicalsignal
Voltage-gated Ca2+ channelopens.
Novel Signal Molecules: Calcium
Figure 6-15 (3 of 5)
Extracellularfluid
Intracellularfluid
Electricalsignal
released fromintracellularCa2+ stores
Chemicalsignal
Ca2+ in cytosolincreases.
Voltage-gated Ca2+ channelopens.
Novel Signal Molecules: Calcium
Figure 6-15 (4 of 5)
Extracellularfluid
Intracellularfluid
Electricalsignal
released fromintracellularCa2+ stores
Ca2+ binds proteins
CalmodulinOther Ca2+-
binding proteins
Chemicalsignal
Ca2+ in cytosolincreases.
Voltage-gated Ca2+ channelopens.
Novel Signal Molecules: Calcium
Figure 6-15 (5 of 5)
Extracellularfluid
Intracellularfluid
Electricalsignal
released fromintracellularCa2+ stores
Ca2+ binds proteins
CalmodulinOther Ca2+-
binding proteins
Alters proteinactivity
Exocytosis Movement
Chemicalsignal
Ca2+ in cytosolincreases.
Voltage-gated Ca2+ channelopens.
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
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
Novel Signal Molecules: Lipids
• The arachidonic acid cascade produces lipid messengers
Figure 6-16
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)
Modulation of Signal Pathways
• Specificity and competition• Agonist versus antagonist• Multiple receptors for one ligand• Alpha receptor• Vasoconstriction
• Beta receptor• Vasodilation
Modulation of Signal Pathways
• Agonist versus antagonist
Figure 6-17
The primaryligand activates
a receptor.
An agonistalso activatesthe receptor.
An antagonistblocks receptor
activity.
ResponseNo
response
Modulation of Signal Pathways
• Target response depends on the target receptor
Figure 6-18
Intestinalblood vessel Skeletal muscle
blood vessel
-Receptor response 2-Receptor response
Epinephrine + -Receptor
2-Receptor-Receptor
Epinephrine + 2-Receptor
Vessel constricts
Vessel dilates
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
Modulation of Signal Pathway
• Disease and drugs target signal transduction proteins
Table 6-3
Control Pathways: Overview
• Physiological control systems keep regulated variables within a desired range during homeostasis
Figure 6-19
Regulatedvariable
Withindesired
range
Noaction
required
Outsidedesiredrange
Sensoris
activated
Effectors
Integratingcenter
CONTROLSYSTEM
sends signal to
influence
alters
Control Systems: Cannon’s Postulates
1. Nervous regulation of internal environment
2. Tonic control
3. Antagonistic control
4. One chemical signal can have different effects in different tissues
Control Systems: Tonic Control
• Tonic control of blood vessel diameter
Figure 6-20
Time
Electricalsignals
fromneuron
Change in signal rate
TimeTime
Tonic control regulates physiological parameters in an up-down fashion.
Increased signal rate Decreased signal rate
Control Systems: Antagonistic Control
Figure 6-21
Antagonistic neurons control heart rate: some speed it up, while others slow it down.
Stimulation by parasympathetic nerves decreases heart rate.Stimulation by sympathetic nerves increases heart rate.
Heart beats Heart beats
Sympatheticneuron
Parasympatheticneuron
Control Pathways
• Comparison of local and reflex control
Figure 6-22
Brain
Blood vessels
Brain evaluates the change andinitiates aresponse.
LOCALCHANGE
LOCALRESPONSE
REFLEXRESPONSE
is initiated by cellsat a distant site.
Systemicchange in blood
pressure sensed here.
Stimulus
Integrating center
Response
KEY
STIMULUS
SENSORor
RECEPTOR
AFFERENTPATHWAY
INTEGRATINGCENTER
EFFERENTPATHWAY
TARGET orEFFECTOR
RESPONSE
Feedback loopR
espo
nse lo
op
Control Pathways: Reflex Control
• Steps in a reflex control pathway
Figure 6-23
Chemoreceptor(pH, gases,chemicals)
Eyes (vision)
Nose (smell)
Tongue (taste)
Ears (hearing,
equilibrium)
Osmoreceptor(osmolarity)
Thermoreceptor(temperature)
Baroreceptor(pressure)
Proprioceptor(body position)
Othermechanoreceptors
(pain, vibration,touch)
RECEPTORS
Specialized cells or structures that convert various stimuli into electrical signals
Cell membrane orintracellular
receptor proteins
Peripheral receptorslie outside the brain.
Central receptorsare in or closeto the brain.
can be
Control Pathways: Receptors
• Multiple meanings of the word receptor
Figure 6-24
Thermometer
WireWater temperatureincreases
Heater Wire to heater
Water temperatureis 25° C
Control box
Water temperature isbelow the setpoint.
Thermometer sensestemperature decrease.
Signal passes throughwire to heater.
Water temperatureincreases.
Heater turns on.
Signal passes fromsensor to controlbox through the wire.
Control box is programmedto respond to temperature below 29 degrees.
STIMULUS
SENSORor
RECEPTOR
AFFERENTPATHWAY
INTEGRATINGCENTER
EFFERENTPATHWAY
TARGET orEFFECTOR
RESPONSE
Reflex steps
1
1
2
3
4
5
6
7
2
3
4
56
7
Control Pathways: Response Loop
• A nonbiological response loop
Figure 6-25
Control Pathways: Response Loop
Figure 6-25, step 1
Water temperatureis 25° C
Water temperature isbelow the setpoint. STIMULUS
Reflex steps
1
1
Control Pathways: Response Loop
Figure 6-25, steps 1–2
Thermometer
Water temperatureis 25° C
Water temperature isbelow the setpoint.
Thermometer sensestemperature decrease.
STIMULUS
SENSORor
RECEPTOR
Reflex steps
1
1
2
2
Control Pathways: Response Loop
Figure 6-25, steps 1–3
Thermometer
Wire
Water temperatureis 25° C
Water temperature isbelow the setpoint.
Thermometer sensestemperature decrease.
Signal passes fromsensor to controlbox through the wire.
STIMULUS
SENSORor
RECEPTOR
AFFERENTPATHWAY
Reflex steps
1
1
2
3
2
3
Control Pathways: Response Loop
Figure 6-25, steps 1–4
Thermometer
Wire
Water temperatureis 25° C
Control box
Water temperature isbelow the setpoint.
Thermometer sensestemperature decrease.
Signal passes fromsensor to controlbox through the wire.
Control box is programmedto respond to temperature below 29 degrees.
STIMULUS
SENSORor
RECEPTOR
INTEGRATINGCENTER
Reflex steps
1
1
2
3
42
3
4
AFFERENTPATHWAY
Control Pathways: Response Loop
Figure 6-25, steps 1–5
Thermometer
Wire
Wire to heater
Water temperatureis 25° C
Control box
Water temperature isbelow the setpoint.
Thermometer sensestemperature decrease.
Signal passes throughwire to heater.
Signal passes fromsensor to controlbox through the wire.
Control box is programmedto respond to temperature below 29 degrees.
STIMULUS
SENSORor
RECEPTOR
INTEGRATINGCENTER
EFFERENTPATHWAY
Reflex steps
1
1
2
3
4
5
2
3
4
5
AFFERENTPATHWAY
Control Pathways: Response Loop
Figure 6-25, steps 1–6
Thermometer
Wire
Heater Wire to heater
Water temperatureis 25° C
Control box
Water temperature isbelow the setpoint.
Thermometer sensestemperature decrease.
Signal passes throughwire to heater.
Heater turns on.
Signal passes fromsensor to controlbox through the wire.
Control box is programmedto respond to temperature below 29 degrees.
STIMULUS
SENSORor
RECEPTOR
INTEGRATINGCENTER
EFFERENTPATHWAY
TARGET orEFFECTOR
Reflex steps
1
1
2
3
4
5
6
2
3
4
56
AFFERENTPATHWAY
Control Pathways: Response Loop
Figure 6-25, steps 1–7
Thermometer
WireWater temperatureincreases
Heater Wire to heater
Water temperatureis 25° C
Control box
Water temperature isbelow the setpoint.
Thermometer sensestemperature decrease.
Signal passes throughwire to heater.
Water temperatureincreases.
Heater turns on.
Signal passes fromsensor to controlbox through the wire.
Control box is programmedto respond to temperature below 29 degrees.
STIMULUS
SENSORor
RECEPTOR
AFFERENTPATHWAY
INTEGRATINGCENTER
EFFERENTPATHWAY
TARGET orEFFECTOR
RESPONSE
Reflex steps
1
1
2
3
4
5
6
7
2
3
4
56
7
Control Pathways: Setpoints
• Oscillation around the setpoint • Acclimatization refers to natural adaptation• Acclimation refers to induced adaptation
Figure 6-26
Setpointof function
Negative feedback turnsresponse loop off
Response loopturns on
Normalrange of function
Control Pathways: Feedback Loops
• Negative and positive feedback
• Feedforward control refers to anticipatory responses
• The response counteracts the stimulus, shutting off the response loop
Figure 6-27a
(a) Negative feedback
Response
Stimulus
Response loopshuts off
Initialstimulus
(b) Positive feedback
Response
Stimulus
Feedback cycleAn outside factor is required to shut off feedback cycle.
Initialstimulus
Control Pathways: Feedback Loops
• The response reinforces the stimulus, sending the varible farther from the setpoint
Figure 6-27b
Control Pathways: Feedback Loops
Figure 6-28
Baby drops lower in uterusto initiate labor
Cervicalstretch
stimulatescausing
Oxytocinrelease
causes
Uterinecontractions
Pushbaby against
cervix
Positive feedback loop
Delivery of babystops the cycle
(a)
Control Pathways: Setpoints
• Circadian rhythms
Figure 6-29a
Control Pathways: Setpoints
Figure 6-29b
(b)
9:00 A.M.
Control Systems: Speed and Specificity
Table 6-4
Control Pathways: Review
Figure 6-30
A simpleendocrine reflex
A simple neuralreflex
A complexneuroendocrine reflex
Internal or external
change
Internal or external
change
Internal or external
change
Receptor Receptor
Afferent path:sensory neuron
Afferent path:sensory neuron
Endocrinesystem sensor-
integratingcenter
Neuralsystem
integratingcenter
Neuralsystem
integratingcenter
Endocrineintegrating
center
Efferent signal:hormone
Efferent signal# 2: hormone
Efferent neuronor
neurohormone
Efferentneuron
Effectors Effectors
Effectors
Response Response
Response
Control Pathways: Review
• Some basic patterns of neural, endocrine, and neuro-endocrine control pathways
Figure 6-31
Neuroendocrine reflexesSimple endocrine
reflex
Endocrinecells
Response
Response
Response
Hormone
Neurohormone
Neurotransmitter
Hormone #2
Stimulus Stimulus Stimulus
Simple neuralreflex
Neurohormonereflex
Receptor
Afferent neuron
Efferentneuron
Neuro-transmitter
Targetcell
Bloodvessel
Response
Response
Response
Stimulus Stimulus Stimulus
KEY
Stimulus
Neurotransmitter
Neurohormone
Classic hormone
Endocrine integrating center
Receptor (sensor) Efferent neuron
Sensory neuron(afferent pathway)
CNS integrating center
Target cell (effector)
Efferent pathways
1 2 3 4 5 6
Control Pathways: Review
Figure 6-31, step 1
Simple neuralreflex
Receptor
Afferent neuron
Efferentneuron
Neuro-transmitter
Targetcell
Response
Stimulus
KEY
Stimulus
Neurotransmitter
Neurohormone
Classic hormone
Endocrine integrating center
Receptor (sensor) Efferent neuron
Sensory neuron(afferent pathway)
CNS integrating center
Target cell (effector)
Efferent pathways
1
Control Pathways: Review
Figure 6-31, steps 1–2
Simple neuralreflex
Neurohormonereflex
Receptor
Afferent neuron
Efferentneuron
Neuro-transmitter
Targetcell
Bloodvessel
Response
Response
Stimulus Stimulus
KEY
Stimulus
Neurotransmitter
Neurohormone
Classic hormone
Endocrine integrating center
Receptor (sensor) Efferent neuron
Sensory neuron(afferent pathway)
CNS integrating center
Target cell (effector)
Efferent pathways
1 2
Control Pathways: Review
Figure 6-31, steps 1–3
Neuroendocrine reflexesSimple neural
reflexNeurohormone
reflex
Receptor
Afferent neuron
Efferentneuron
Neuro-transmitter
Targetcell
Bloodvessel
Response
Response
Response
Stimulus Stimulus Stimulus
KEY
Stimulus
Neurotransmitter
Neurohormone
Classic hormone
Endocrine integrating center
Receptor (sensor) Efferent neuron
Sensory neuron(afferent pathway)
CNS integrating center
Target cell (effector)
Efferent pathways
1 2 3
Control Pathways: Review
Figure 6-31, steps 1–4
Neuroendocrine reflexes
Endocrinecells
Response
Hormone
Neurohormone
Neurotransmitter
Stimulus
Simple neuralreflex
Neurohormonereflex
Receptor
Afferent neuron
Efferentneuron
Neuro-transmitter
Targetcell
Bloodvessel
Response
Response
Response
Stimulus Stimulus Stimulus
KEY
Stimulus
Neurotransmitter
Neurohormone
Classic hormone
Endocrine integrating center
Receptor (sensor) Efferent neuron
Sensory neuron(afferent pathway)
CNS integrating center
Target cell (effector)
Efferent pathways
1 2 3 4
Control Pathways: Review
Figure 6-31, steps 1–5
Neuroendocrine reflexes
Endocrinecells
Response
Response
Hormone
Neurohormone
Neurotransmitter
Hormone #2
Stimulus Stimulus
Simple neuralreflex
Neurohormonereflex
Receptor
Afferent neuron
Efferentneuron
Neuro-transmitter
Targetcell
Bloodvessel
Response
Response
Response
Stimulus Stimulus Stimulus
KEY
Stimulus
Neurotransmitter
Neurohormone
Classic hormone
Endocrine integrating center
Receptor (sensor) Efferent neuron
Sensory neuron(afferent pathway)
CNS integrating center
Target cell (effector)
Efferent pathways
1 2 3 4 5
Control Pathways: Review
Figure 6-31, steps 1–6
Neuroendocrine reflexesSimple endocrine
reflex
Endocrinecells
Response
Response
Response
Hormone
Neurohormone
Neurotransmitter
Hormone #2
Stimulus Stimulus Stimulus
Simple neuralreflex
Neurohormonereflex
Receptor
Afferent neuron
Efferentneuron
Neuro-transmitter
Targetcell
Bloodvessel
Response
Response
Response
Stimulus Stimulus Stimulus
KEY
Stimulus
Neurotransmitter
Neurohormone
Classic hormone
Endocrine integrating center
Receptor (sensor) Efferent neuron
Sensory neuron(afferent pathway)
CNS integrating center
Target cell (effector)
Efferent pathways
1 2 3 4 5 6
Control Pathways: Review
Table 6-5
Summary
• Cell-to-cell communication• Electrical signals• Chemical signals• Four methods
Summary
• Signal pathways• Signal transduction• Amplification• Second messengers• Receptor-enzymes• G-proteins• Integrin• Ligand-gated ion channels
Summary
• Novel signal molecules• Calcium• NO• CO
• H2S
• Lipids
• Modulation of signal pathways• Agonist versus antagonist• Up-regulation and down-regulation
Summary
• Control pathways• Cannon’s postulates• Local control• Reflex control• Feedback loops• Negative feedback• Positive feedback• Feedforward control• Circadian rhythms