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Unit 3: Physiological Systems
Nervous System Endocrine System
ReproducAve System CELLS TISSUES ORGANS
ORGANISMS POPULTIONS COMMUNITIES
ECOSYSTEMS
Cellular communicaAon
CELLS TISSUES ORGANS
ORGANISMS POPULTIONS COMMUNITIES
ECOSYSTEMS Each step requires
communicaAon and/or interacAon
Cellular communicaAon
CELLS TISSUES ORGANS
ORGANISMS POPULTIONS COMMUNITIES
ECOSYSTEMS Ecosystems WILL NOT funcAon
without cell-‐cell communicaAon!
• Cell-‐cell communicaAon is one of
the most important evoluAonary
advancement of life.
HOW DOES IT HAPPEN?
Cellular communicaAon
Signaling: cells “talking” to one
another
Transmission: How the signals are
moved or passed between cells
Control systems
NERVOUS SYSTEM • Fine, rapid movements
– Muscle control
• Neurons • Synapses
ENDOCRINE SYSTEM • Slow movements, wide
temporal range – Metabolic processes
• Hormones
• Physiological systems that detect
changes and respond accordingly
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Control systems
NERVOUS SYSTEM • Fine, rapid movements
– Muscle control
• Neurons • Synapses
ENDOCRINE SYSTEM • Slow movements, wide
temporal range – Metabolic processes
• Hormones
SENSORY SYSTEM • How body
receives/sends sensory signals
Control systems
NERVOUS SYSTEM • Fine, rapid movements
– Muscle control
• Neurons • Synapses
ENDOCRINE SYSTEM • Slow movements, wide
temporal range – Metabolic processes
• Hormones
SENSORY SYSTEM • How body
receives/sends sensory signals
• Most Assues under control of
both nervous and endocrine systems
Cell Signaling
1. Ch. 11: Neurons – Structure –
CommunicaAon • AcAon potenAals
2. Ch. 2: Synapses – Structure –
CommunicaAon • NeurotransmiWer
Nervous system: Tissues and cells
Nervous system
Neural Assues
Nerve cells (neurons)
Glial cells
Neurons • Cell that is adapted to
generate an electrical signal – AcAon
potenAal: a short, self-‐propagaAng
impulse
• Signals from other cells received
at synapses – Contact points between
cells
Neuron structure • 4 main parts:
1. Dendrite 2. Cell body (soma) 3.
Axon 4. PresynapAc terminal
• Label these 4 parts on your
sheet – Include funcAon of
each
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Neuron structure • 4 main parts:
1. Dendrite – Site of synapAc
input à Receives signals from
other neurons
– Conveys informaAon to the cell
body
Neuron structure • 4 main parts:
1. Dendrite 2. Cell Body (soma) –
Signals received
and impulses generated
Neuron structure • 4 main parts:
1. Dendrite 2. Cell Body (soma) 3.
Axon – Carries
informaAon away – ConducAon of
impulse via acAon potenAal (AP)
– Axon hillock: Where AP starts
Neuron structure • 4 main parts:
1. Dendrite 2. Cell Body (soma) 3.
Axon 4. PresynapAc
terminals – Output of neuron –
NeurotransmiWer
secreted
• Cell body composed of normal
cell organelles
• # axons and dendrites/neuron
determines the type and funcAon
of neuron
Neuron structure • Some axons covered
in myelin sheaths – Increase speed
of impulse
– Physical and metabolic support for
neurons
– Made up of Glial cells
Neuron structure
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• Glial cells: 1. Schwann Cells (PNS)
2. Oligodendrocytes
(CNS) – Insulate and
increase impulse transmission velocity
along axons
Neuron structure Neuron structure •
Glial cells: 1. Schwann Cells (PNS)
2. Oligodendrocytes
(CNS) 3. Astrocytes • Line capillaries
• Aid communicaAon
between circulatory and nervous systems
Neuron structure • Glial cells: 1.
Schwann Cells (PNS) 2. Oligodendrocytes
(CNS) 3. Astrocytes 4. Microglial cells
• Mediate immune
system response • May consume
pathogens and cellular debris caused
by injury
Neurons • Neurons that ‘end’ as
synapses on another neurons are
innervated
• All neurons connected in vast
web à Nervous System
Neuron Structure Video
Chapters 11 and 12
1. Neurons – Structure – CommunicaEon •
AcAon potenAals
2. Synapses – Structure – CommunicaAon •
NeurotransmiWer
Neurons generate acAon potenAals
• Neurons: Cell that are adapted
to generate an electrical signal
• AcAon potenAal: a short,
self-‐propagaAng impulse – VERY fast
(0.4-‐3 ms!)
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AcAon potenAals
AcAon PotenAal Video
Change in membrane permeability to
specific ions
Membrane potenAal: occurs when there
is an ion concentraAon gradient
across membrane
Change in membrane potenAal
ACTION POTENTIAL
• VOLTAGE-‐DEPENDENT: Caused by change
in membrane potenAal (ion
concentraAon gradient)
• VOLTAGE-‐DEPENDENT: Caused by change
in membrane potenAal (ion
concentraAon gradient)
• ALL-‐OR-‐NONE: only occur when
voltage threshold is reached
AcAon potenAals
AcAon potenAals • Caused by increased
ion permeability – Na and K
• Four phases: 1. ResAng membrane
potenAal (start) 2. Rising phase 3.
Falling phase 4. Recovery
AP Phases: ResAng membrane potenAal
• K+ leak channel always open
– K+ diffuses in/out in small
amounts according to electrochemical
gradient
• SAmulus à membrane depolarized above
threshold – Voltage-‐gated channels
open à more permeable to Na+
– Na+ rushes into cell due to
concentraAon gradient
AP Phases: Rising Phase
1. Na+ channel inacAvaAon: decreased
permeability to Na+
2. Voltage-‐gated K+ channels open –
K+ exit cell towards equilibrium
AP Phases: Falling Phase
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• Voltage-‐gated K+ channel stays open
briefly • Na+ channels close (no
ion concentraAon gradient)
AP Phases: Recovery
• VOLTAGE-‐DEPENDENT: Caused by change
in membrane potenAal
• ALL-‐OR-‐NONE: only occur when
voltage threshold is reached
• PROPAGATION: UnidirecAonal
AcAon potenAals
AcAon PotenAal Video
and FAST
AP propagaAon: Velocity 1. Greater axon
diameter à faster impulse
AP propagaAon: Velocity 1. Greater axon
diameter à faster impulse
2. More insulaAng myelin (Schwann cells
or Oligodendrocytes)à faster impulse
– APs only occur at Nodes of
Ranvier
– APs “jump” past myelinated internodes
AP propagaAon: Velocity 1. Greater axon
diameter à faster impulse
2. More insulaAng myelin (Schwann cells
or Oligodendrocytes)à faster impulse
More myelin
APs can travel faster travel along
skinnier axons
Can pack more axons into smaller
spaces
More complex organisms possible
AP propagaAon: Velocity 1. Greater axon
diameter à faster impulse
2. More insulaAon (more myelin) à
faster impulse
3. Higher temperature à faster
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3 types of neurons 1. Spiking
1. SAmulus triggers acAon potenAal
2. AP travels train-‐like down axon
• Frequency of AP
determines amplitude (strength)
1. Sensory sAmulus
2. AcAon potenAal
3. NeurotransmiWer released at
axon
terminal
4. SynapAc Input
3 types of neurons 1. Spiking 2.
Non-‐spiking – Impulse spread
electronically (No AP generated)
– Short neurons • Photoreceptors • ReAna
cells • Olefactory cells
3 types of neurons 1. Spiking 2.
Non-‐spiking 3. Spontaneous – Impulses sent
at
regular intervals without sAmulus •
Cardiac Assues • Pacemaker cells
Chapters 11 and 12
1. Neurons – Structure – CommunicaAon •
AcAon potenAals
2. Synapses – Structure – CommunicaAon •
NeurotransmiWers
Synapses • Specialized site of contact
between two neurons or between
effector-‐neuron
• SynapEc cleI: Any space between
neurons
SynapAc transmission • “CommunicaAon” from
presynapAc to postsynapAc cells
across synapAc clem – Very fast
• Electrical or chemical
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SynapAc transmission: Electrical • Charge
moves across gap juncAon
– Low-‐resistance pathway for current
flow across protein channels
• Connexons • PROBLEM: Loss of
amplitude!
SynapAc transmission: Chemical • Slower
• Excitatory: raises probability of
cell generaAng
AP or increases AP frequency •
Inhibitory: lowers probability of AP
or
frequency
SynapAc transmission: Chemical • Chemical
transmission
involves the release of a
neurotransmi+er – 1 neuron produces
1 type
of neurotransmiWer – Receives many (may
be
connected to > 1 synapse)
• Dozens have been IDed • HUGE
diversity in funcAon
Diversity of neurotransmiWers
SynapAc transmission: Chemical • To be
considered a neurotransmiWer, a
chemical
must: 1. Be present in
presynapAc terminal 2. Be released
when neuron is sAmulated 3. Cause
changes in membrane potenAal when
in
synapAc clem 4. Include a mechanism
for removal/uptake 5. Drugs should
induce the appropriate response
DON’T WRITE THESE DOWN!!!
SynapAc transmission: Chemical 1.
NeurotransmiWers released from synapAc
vesicles at acAve zone 2. Diffuse
across clem 3. Bind to
receptor sites on postsynapAc cell
• Driven by electrochemical and
concentraAon
gradients
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SynapAc transmission: Chemical
1. AP opens voltage-‐gated Ca+ channels
2. Ca+ rushes in (due to
concentraAon gradient) à synapAc
vesicles release Ach into synapAc
clem
• AP arrives at presynapAc terminal
SynapAc transmission: Chemical
3. Ach diffuses through clem à
postsynapAc membrane
4. Ligand-‐gated Ach receptor channels
open à
5. Na+ and K+ rush into cell
6. Cell is excited à starts new
AP
• AP arrives at presynapAc terminal
SynapAc transmission: Chemical
7. Remainder of Ach inhibited by
enzyme – Enzyme not always
necessary 8. Re-‐uptake back
into presynapAc terminal by transporter
protein
• SynapAc funcAons won’t proceed while
Ach present in synapAc clem
SynapAc transmission: Chemical
• AnimaAons of synapses and
neurotransmiWer release:
Video 1 – Synapse Video 2 –
Synapse Video 3 – NeurotransmiWer
Video 4 – NeurotransmiWer release
Psychiatric condiAons treated with
neurotransmiWer
• Manipulate synthesis and/or reuptake
of specific neurotranmsiWers
• EXAMPLE: SelecAve serotonin reuptake
inhibitors (SSRIs) – Depression
treatment
Less serotonin uptake
More serotonin available to postsynapAc
neurons
More “happy hormone” moving through
your body