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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