chapter 6b

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

Calmodulin Other 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

Calmodulin Other 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

Calmodulin Other 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 environment2. Tonic control3. Antagonistic control4. 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

esponse loop

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 reflexes Simple endocrinereflex

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

KEYStimulus

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