5/27/2018 Cell Cell Communication

1/14

Figure 6.19-7 ESSENTIALS Simple and Complex Reflex Pathways

E

S

T

KEY

Output PathwaysStimulus

Sensor

Sensory neuron(input pathway)

CNS integratingcenter

Endocrineintegrating center

Efferent neuron

Neurotransmitter

Neurohormone

Classic hormone

Target cell (effector)

Simple EndocrineReflex

Stimulus

Response

E

T

Example:Insulin releasewhen bloodglucose increases

5/27/2018 Cell Cell Communication

2/14

Figure 6.1-1 ESSENTIALS Communication in the BodyLOCAL COMMUNICATION

Gap junctionsformdirect cytoplasmicconnections betweenadjacent cells.

Contact-dependent signalsrequire interaction betweenmembrane molecules ontwo cells.

Autocrine signalsact on the same cellthat secreted them. Paracrine signalsare secreted by one cell and diffuse to

adjacent cells.

Receptor

5/27/2018 Cell Cell Communication

3/14

Figure 6.1-2 ESSENTIALS Communication in the BodyLONG-DISTANCE COMMUNICATION

Endocrine System Nervous System

Long-distance signaling may be electrical signals passingalong neurons or chemical signals that travel through thecirculatory system.

Endocrinecell

Cellwithoutreceptor

Cellwith

receptor Targetcell

No response

Response

Blood

Hormonesare secreted by endocrine glands or cells into theblood. Only target cells with receptors for the hormone respondto the signal.

Neurohormonesare chemicalsreleased by neurons into the bloodfor action at distant targets.

Neurotransmittersare chemicals secreted by neurons that diffuseacross a small gap to the target cell.

No response

Response

Response

Cellwithoutreceptor

Cellwith

receptor

Targetcell

Blood

Neuron

Neuron

Electricalsignal

5/27/2018 Cell Cell Communication

4/14

Figure 6.3 Target cell receptors may be located on the cell surface or inside the cellIntracellular Signal Receptors

Four Categories of Membrane Receptors

Cell Membrane Receptors

Extracellular signalmolecule binds to acell membranereceptor.

Bindingtriggers

Rapid cellularresponses

Receptorin nucleus

Receptor in cytosol

Lipophilic signalmolecules diffuse

through the cellmembrane.

Binding tocytosolicor nuclearreceptorstriggers

Slower responsesrelated to changes

in gene activity

Channel Receptor Receptor

ECF

Extracellularsignal

molecules

ICF

Enzyme G protein

Cell

membrane

Anchorprotein

Cytoskeleton

Ligand binding tointegrin receptorsalters the cytoskeleton.

Integrin receptorG proteincoupled receptorReceptor-enzyme

Ligand binding to a G proteincoupled receptor opens an ionchannel or alters enzyme activity.

Ligand binding to areceptor-enzyme activatesan intracellular enzyme.

Ligand bindingopens or closesthe channel.

Receptor-channel

5/27/2018 Cell Cell Communication

5/14

Figure 6.5a Biological signal transduction (1 of 2)

Basic Signal Transduction

Firstmessenger

Transducer

Secondmessengersystem

Targets

Signalmolecule

Membranereceptor protein

Intracellularsignal molecules

Targetproteins

binds to

activates

alter

create

Response Response

5/27/2018 Cell Cell Communication

6/14

Figure 6.6c ESSENTIALS Signal Transduction

Second messenger pathways

ATP

GTP

Membranephospholipids

Adenylyl cyclase(membrane)

Guanylyl cyclase(membrane)

Guanylyl cyclase(cytosol)

Phospholipase C(membrane)

GPCR*

GPCR

Receptor-enzyme

Nitric oxide (NO)

Activates proteinkinases, especially PKA.Binds to ion channels.

Activates proteinkinases, especially PKG.

Binds to ion channels.

Releases Ca2+fromintracellular stores.

Activates proteinkinase C.

Binds to calmodulin.Binds to other proteins.

Phosphorylatesproteins. Alterschannel opening.

Phosphorylatesproteins.

Alters channelopening.

See Ca2+effectsbelow.

Phosphorylatesproteins.

Alters enzyme activity.Exocytosis, musclecontraction, cyto-skeleton movement,channel opening.

*GPCR G proteincoupled receptor. IP3 Inositol trisphosphage. DAG idacylglycerol

Ca2+

IP3

DAG

cGMP

cAMP

Ions

Lipid-derived*

Nucleotides

SECONDMESSENGER MADE FROM

AMPLIFIERENZYME LINKED TO ACTION EFFECTS

5/27/2018 Cell Cell Communication

7/14

Figure 6.7

Tyrosine Kinase Receptor

Tyrosine kinase (TK) transfers a phosphate group fromATP to a tyrosine (an amino acid) of a protein.

Signal molecule bindsto surface receptor

Tyrosine kinase oncytoplasmic side

Phosphorylatedprotein

ADP

ATP

ICF

Protein Protein

Active binding site

Cellmembrane

ECF

TK

R

L

5/27/2018 Cell Cell Communication

8/14

Figure 6.8a (1 of 2)

GPCR-adenylyl Cyclase Signal Transduction and Amplification

One signalmolecule

GPCR

G protein

ATP

Adenylyl

cyclase

cAMP

Proteinkinase A

Phosphorylatedprotein

Cellresponse

Using the pattern shown in Fig. 6.6a,create a cascade that includes ATP, cAMP,adenylyl cyclase, a phosphorylatedprotein, and protein kinase A.

Protein kinase A phosphorylatesother proteins, leading ultimatelyto a cellular response.

cAMP activates protein kinase A.

Adenylyl cyclase converts ATP tocyclic AMP.

G protein turns on adenylyl cyclase,an amplifier enzyme.

Signal molecule binds to G proteincoupled receptor (GPCR), whichactivates the G protein.

FIGURE QUESTION

5/27/2018 Cell Cell Communication

9/14

!"#$% '()(*+,' -)./-+(0 1234512 3()'(.,2 6',7 *-2)'(-.)

8$)(5539 7():-2137 -20 ;54),3( 0(*(20(2)(

GLP-1 = glucagon-likepeptide 1

5/27/2018 Cell Cell Communication

10/14

Figure 6.8b (2 of 2)

GPCR-phospholipase C Signal Transduction

Signal

molecule

ReceptorG protein

ERCa2+ Ca2+stores

PLC

IP3

PKC

DAG

Membrane phospholipid

Cellularresponse

Phosphorylatedprotein

Protein Pi

KEY

PLC phospholipase C

DAG diacylglycerolPKC protein kinase C

IP3 inositol trisphosphate

ER endoplasmic reticulum

Cellmembrane

Intracellularfluid

Extracellular

fluid

IP3causes releaseof Ca2+fromorganelles, creatinga Ca2+signal.

DAG activates proteinkinase C (PKC), whichphosphorylatesproteins.

PLC converts membrane phospho-lipids into diacylglycerol (DAG), whichremains in the membrane, and IP3,which diffuses into the cytoplasm.

G protein activatesphospholipase C(PLC), an amplifierenzyme.

Signal moleculeactivates receptorand associatedG protein.

5/27/2018 Cell Cell Communication

11/14

Figure 6.10 ESSENTIALS Summary Map of Signal Transduction

5/27/2018 Cell Cell Communication

12/14

Figure 6.13

Target response depends on the target receptor.

-Receptor Response 2-Receptor Response

-Receptor 2-Receptor

Epinephrine -Receptor Epinephrine 2-Receptor

Vessel constricts.

Vessel dilates.

Intestinal

blood vessel Skeletal muscleblood vessel

Epinephrine can bind todifferent isoforms of theadrenergic receptor.

In this example, blood vesselsdilate or constrict dependingon their receptor type.

5/27/2018 Cell Cell Communication

13/14

Figure 6.15b Tonic and antagonist control of regulated variables (4 of 6)

ANTAGONISTIC CONTROL

Stimulation by sympathetic nerves increases heart rate.Antagonistic controluses different signalsto send a parameter in opposite directions. Inthis example, antagonistic neurons control heartrate: some speed it up, while others slow it down.

Sympatheticneuron

Parasympatheticneuron

Heartbeats

Heartbeats

Time (sec)

Time (sec)

0 1 2 3

Stimulation by parasympathetic nerves decreases heart rate.

What heart rates (in beats/min)are shown on the two ECGtracings?

FIGURE QUESTION

0 1 2 3

5/27/2018 Cell Cell Communication

14/14

Figure 6.19-1 ESSENTIALS Simple and Complex Reflex PathwaysComplex Neuroendocrine Reflexes Simple EndocrineReflexSimple NeuralReflex NeurohormoneReflexStimulus Stimulus Stimulus Stimulus Stimulus Stimulus

Sensor

Sensory

neuron

Efferentneuron

Neuro-transmitter

Targetcell

Example:The knee jerk reflex

Bloodvessel

Response

Response

Response

Response

Response

Neurotransmitter

Neurohormone

Endocrinecells

Hormone

Hormone #2

T

T

T

T

T

T

E

E

E

E1

E2

Example:Release of breastmilk in responseto suckling

Example:Insulin secretion inresponse to a signal

from the brain

Example:Secretion ofgrowth hormone

E

S

T

KEY

Output PathwaysStimulus

Sensor

Sensory neuron(input pathway)

CNS integratingcenter

Endocrineintegrating center

Efferent neuron

Neurotransmitter

Neurohormone

Classic hormone

Target cell (effector)

Example:This pattern occurswith hormonesreleased by theanterior pituitary.

Response

CNS CNS CNS CNS CNS