Transcript Chapter 6 powerpoint file

POWERPOINT® LECTURE SLIDE PRESENTATION
by LYNN CIALDELLA, MA, MBA, The University of Texas at Austin
Additional material added by J Padilla for Physiology 31 at ECC
UNIT 1
6
PART A
Communication,
Integration,
and Homeostasis
HUMAN PHYSIOLOGY
AN INTEGRATED APPROACH
DEE UNGLAUB SILVERTHORN
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FOURTH EDITION
Cell-to-Cell Communication: Overview
 Physiological signals
 Electrical signals
 Changes in cell’s membrane potential
 Chemical signals
 Secreted by cells into ECF
 Responsible for most communication within the body
 Target cells, or targets, receive signals
 Four basic methods of communication
 Gap junctions- direct transfer from cell to cell
 Contact-dependent signals- ligand bound to cell attaches to
receptor
 Local Communication- autocrine and paracrine signals
 Long-distance communication- nerve impulses and hormones
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Cell-to-Cell Communication: Methods
Direct contact and local cell-to-cell communication
Gap junctions transfer both chemical and electrical signals
found in any cell type, they are the only means of direct electrical
signal transfer
CAMs transfer signals in both directions- CAMS= cell adhesion
molecules linked to cytoskeleton and intracellular enzymes
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Figure 6-1a
Cell-to-Cell Communication: Methods
Paracrine and autocrine are chemical signalsuse interstitial fluid to travel to adjacent cells but do not go
a long distance
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Figure 6-1c
Cell-to-Cell Communication: Methods
Long distance cell-to-cell communication
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Figure 6-2a
Cell-to-Cell Communication: Methods
Neurotransmitters have a rapid effect
Neuromodulators
act as paracrine or
autocrine signals
and have a slower
effect.
All cells are exposed to
hormones and
neurohormones but
only target cells
respond to them.
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Figure 6-2b
Signal Pathways: Receptor locations
Target cell
receptorsLocated in any area of
the cell. Lipophilic
signals(mostly
hormones) bind
intracellularly.
Lipophobic singals stay
in the ECF and bind
receptor proteins.
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Figure 6-4 (1 of 2)
Control of Cells by Chemical Messengers
How hormones and other signals work
Communication requires:
signals (ligands) and receptors (binding proteins).
The chemical properties of a ligand predict its binding site:
• Hydrophobic/lipid-soluble: cytosolic or nuclear receptors,
typically change gene expression, leading to slow but
sustained responses
examples: steroid hormones, thyroid hormones
• Hydrophilic/lipid-insoluble: membrane-spanning receptors
typically activate rapid, short-lived responses that can
be of drastic impact.
examples: epinephrine, insulin,…
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Epinephrine
binds here
Receptors on the
surface of a cell
are typically
proteins that
span the
membrane.
Figure 5-1
… cellular response begins …
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Only Cell A has the
matching receptors
for this chemical
messenger, so it
is the only one
that responds.
Figure 5-2
Cells B & C lack the matching receptors
for this chemical messenger, so they
are not directly affected by the signal.
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Signal Pathways: Overview
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Figure 6-3
Signal Pathways: Membrane Receptors
Four categories of membrane receptors
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Figure 6-5
Signal Pathways: Signal Amplification
Transducers convert extracellular signals into
intracellular messages which create a response
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Figure 6-7
Signal Pathway: Biological Signal Transduction
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Figure 6-8
Signal Pathway: Signal Transduction
Steps of a cascade
Steps of signal
transduction
pathway form a
cascade
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Figure 6-9
Signal Pathway: Receptor Enzymes
Tyrosine kinase, an example of receptor-enzyme
Ligands include growth factors, cytokines,
insulin.
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Figure 6-10
Signal Pathway: GPCR- G protein coupled
receptors
 Membrane-spanning proteins  Cytoplasmic tail linked to G protein, a three-part
transducer molecule – changes from GDP to GTP to
become activated
 When G proteins are activated, they  Open ion channels in the membrane  Alter enzyme activity on the cytoplasmic side of the
membrane – they link to amplifier enzymes
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GPCR: Adenylyl Cyclase-cAMP ********
The G-protein
coupled
adenylyl
cyclasecAMP
system
G proteincoupled
receptor
1
One signal
molecule
2
Adenylyl
cyclase
2 G protein turns on adenylyl
cyclase, an amplifier enzyme.
3
ATP
3 Adenylyl cyclase converts
ATP to cyclic AMP.
G protein
cAMP
4
4 cAMP activates protein
kinase A.
5
5 Protein kinase A
phosphorylates other
proteins, leading ultimately
to a cellular response.
Protein
kinase A
Phosphorylated
protein
G-protein
receptors
are the most
abundant
type
1 Signal molecule binds to
G protein-linked receptor,
which activates the G protein.
Cell
response
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Figure 6-11
GPCR: The Phospholipase C System *********
Includes second
messengers molecules
Signal
molecule
Extracellular
fluid
1
Membrane phospholipid
Cell
membrane
3
2
PL-C
4
DAG
PK-C
Receptor
Protein + Pi
IP3
G protein
Intracellular
fluid
5
Ca2+ stores
Phosphorylated
protein
Ca2+
ER
Cellular
response
1 Signal molecule 2
activates receptor
and associated
G protein.
G protein activates 3 PL-C converts membrane 4
phospholipase C
phospholipids into
(PL-C), an amplifier
diacylglycerol (DAG), which
enzyme.
remains in the membrane,
and IP3, which diffuses
into the cytoplasm.
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KEY
PL-C
DAG
PK-C
IP3
ER
=
=
=
=
phospholipase C
diacylglycerol
protein kinase C
inositol
trisphosphate
= endoplasmic
reticulum
DAG activates protein 5
kinase C (PK-C), which
phosphorylates
proteins.
IP3 causes release
of Ca2+ from
organelles,
creating a
Ca2+ signal.
Figure 6-12
Signal Pathway: Receptor-Channel *********
Gated
channels
control the
flow of ions
and influence
the
concentration
gradient
contributing to
changes in
membrane
potential.
Ions
Extracellular
signal
molecules
1
1 Receptor-channels open or
close in response to signal
molecule binding.
Ion
channel
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Figure 6-13, step 1
Signal Pathway: Receptor-Channel
Ions
Extracellular
signal
molecules
1
Ion
channel
2
G proteincoupled
receptor
G protein
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1 Receptor-channels open or
close in response to signal
molecule binding.
2 Some channels are directly
linked to G proteins.
Figure 6-13, steps 1–2
Signal Pathway: Receptor-Channel
Binds to
molecules
dissolved
in the ECF,
or to Gprotiens,
or to
second
messenge
rs.
Ions
Extracellular
signal
molecules
1
Ion
channel
2
G proteincoupled
receptor
G protein
3
Intracellular
signal molecules
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1 Receptor-channels open or
close in response to signal
molecule binding.
2 Some channels are directly
linked to G proteins.
3 Other ligand-gated channels
respond to intracellular
second messenger.
Figure 6-13, steps 1–3
Signal Pathway: Receptor-Channel
Found in
areas
where
quick
changes
are
necessary
like in
nervous
and
muscle
Ions
Extracellular
signal
molecules
1
Ion
channel
G proteincoupled
receptor
2
G protein
Change in membrane
permeability to
Na+, K+, Cl–
3
Intracellular
signal molecules
1 Receptor-channels open or
close in response to signal
molecule binding.
2 Some channels are directly
linked to G proteins.
3 Other ligand-gated channels
respond to intracellular
second messenger.
Creates electrical
signal
Voltage-sensitive
protein
Cellular
response
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Figure 6-13
Signal Pathway: Signal Transduction
Summary map of signal transduction systems
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Figure 6-14
Novel Signal Molecules: Calcium*********
 Calcium as an
intracellular
messenger:
 Most versatile ion;
enters ICF through
gated channels
 Stored in the ER
or moved in by
active transport
Rapid increases of
Ca2+ in the ICF
triggers other
chemical reaction
cascades initiated
by binding
proteins
Extracellular
fluid
Ca2+
Electrical
signal
Voltage-gated
Ca2+ channel
opens.
Ca2+ released from
intracellular
Ca2+ stores
Ca2+
Ca2+ binds to
proteins
Chemical
signal
Calmodulin
Intracellular
fluid
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Ca2+ in cytosol
increases.
Alters protein
activity
Other Ca2+-binding
proteins
Exocytosis
Movement
Figure 6-15
Control Systems: Tonic Control
Physiological control systems keep regulated variables
within a desired range during homeostasis
Tonic control of blood vessel diameter
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Figure 6-20
Control Systems: Cannon’s Postulates
 Nervous regulation of internal environment –
maintain conditions that allow normal function
 Tonic control – continous monitoring that changes a
condition with increased or decreased signalingprimarily done by NS
 Antagonistic control – NS or endocrine send
separate signals for increasing or decreasing a
response
 One chemical signal can have different effects in
different tissues – the effect is based on the type of
receptor the molecule binds
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Control Systems: Antagonistic Control
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Figure 6-21a
Control Pathways
Comparison of local and reflex control
Steps in a reflex control pathway – two alternate routes
Integrating centers determine whether the incoming signal is
within setpoint range
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Figure 6-22
Control Pathways: Receptors
Multiple meanings of the word receptor
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Figure 6-24
Control Pathways: Response Loop
A nonbiological response loop
Reflex steps
1 Water temperature
is 25˚ C
2
Thermometer
7 Water temperature
increases to 30˚ C
Wire
3
1 Water temperature is
below the setpoint.
STIMULUS
2 Thermometer senses
temperature decrease.
SENSOR
or
RECEPTOR
3 Signal passes from
sensor to control
box through the wire.
AFFERENT
PATHWAY
4 Control box is
programmed
to respond to
temperature below
29 degrees.
5 Signal passes through
wire to heater.
4 Control
box
6
Heater
5
INTEGRATING
CENTER
EFFERENT
PATHWAY
6 Heater turns on.
TARGET OR
EFFECTOR
7 Water temperature
increases.
RESPONSE
Wire to heater
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Figure 6-25
Control Pathways: Setpoints
Oscillation around the setpoint  Acclimatization refers to natural adaptation – natural
conditions
 Acclimation refers to induced adaptation – often in a
lab setting
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Figure 6-26
Control Pathways: Feedback Loops
Negative and positive
feedback
Feedforward control
refers to anticipatory
responses
Negative feedback
maintains
homeostasis by
opposing or
removing the signal
but cannot prevent
an initial stimulus
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Figure 6-27a
Control Pathways: Feedback Loops
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Figure 6-27b
Control Pathways: Setpoints
Circadian rhythms
Pre-set homeostatic changes
based on environmental
conditions- helps to predict and
prepare for changes.
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Figure 6-29a
Control Systems: Speed and Specificity
Property
Neural
Specificity
Single target
Nature of signal Electrical 
chemical
Speed
Rapid
Duration
Very short
Coding for
Intensity =
stimulus
frequency
intensity
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Endocrine
Most cells
Chemical
Slower
Longer
Intensity =
amount of
hormone
Control Pathways: Review
Simple neural
reflex
1
Some basic patterns
of neural,
endocrine,
and neuroendocrine control
pathways
Neurohormone
reflex
2
3
4
5
Stimulus
Stimulus
Stimulus
Stimulus
R
R
R
R
Stimulus
Simple endocrine
reflex
6
Neuroendocrine reflexes
Stimulus
Receptor
R
R
E
Afferent
neuron
CNS
integrating
center
Neurotransmitter
T
Efferent
neuron
Endocrine
integrating
center
Neurotransmitter
T
Neurohormone
Response
E
Target
cell
Blood
vessel
Response
E
T
Endocrine
cells
E1
Hormone
T
Response
KEY
Response
S
Stimulus
Efferent pathways
T
Efferent neuron
R
Receptor (sensor)
Neurotransmitter
Sensory neuron
(afferent pathway)
Endocrine cell
Hormone #2
Response
Neurohormone
CNS or endocrine
integrating center
E
E2
Classic hormone
T
T
Target cell(effector)
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Response
Figure 6-31