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Lecture 5

EXSC 224 Lecture 5: Lecture 5 - 9/1 (+Quiz)

5 Pages
84 Views
Fall 2016

Department
Exercise Science
Course Code
EXSC 224
Professor
Thompson
Lecture
5

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G Protein-linked receptors - second messenger systems
Sits next to the membrane, inside the cell
Activation of g protein causes events, that activates a second messenger, which
opens a channel
These cause formation of an intracellular second messenger (cyclic AMP in this
case) that brings about the cell’s response
1. Neurotransmitter (1st messenger) binds and activates receptor
When neurotransmitter binds to a receptor, the receptor changes shape
2. Receptor activates G protein
G protein gets its name from GTP
GTP can be used as an energy source
This is what powers the G protein
This causes G protein it to move
3. G protein activates adenylate cyclase
Adenylate cyclase is an enzyme that uses ATP
Causes the molecule to form a circle
Cyclic AMP
4. Adenylate cyclase converts ATP to cAMP (2nd messenger)
cAMP stimulates things to happen inside the cell
5a. cAMP changes membrane permeability by opening or closing ion channels
5b. cAMP activates enzymes
5c. cAMP activates specific genes
Does this system require energy to activate it?
YES!! GTP and ATP!!
Neural Integration: Neuronal Pools
Functional groups of neurons that:
Integrate incoming information
Forward the processed information to other destinations
One presynaptic fiber synapses onto several post synaptic fiber
Simple neuronal pool
Single presynaptic fiber ranches and synapses with several neurons in
the pool
Facilitated zone
Discharge zone
Presynaptic (input) fiber
Types of Circuits in Neuronal Pools
Diverging circuit
One incoming fiber stimulates an ever-increasing number of
fibers, often amplifying circuits
May affect a single pathway or several
Common in both sensory and motor systems
Divergence to multiple pathways
Divergence in same pathway
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Goes for 1>>2>>more
Converging circuit
Opposite of diverging circuits, resulting in either strong stimulation
or inhibition
Also common in sensory and motor systems
When there are a bunch of neurons synapsing onto one
Convergence from multiple sources
Convergence from a single source
Reverberating (oscillating) circuit
Chain of neurons containing collateral synapses with previous
neurons in the chain
Helps regulate things like breathing
Parallel after-discharge circuit
Incoming fiber stimulates several neurons in parallel arrays to
stimulate a common output cell
A variation of converging circuit, this one just has multiple steps,
but has same basic outcome
Something in series means you have something in STEPWISE order
Something in parallel is 2 series following a different path, but going to the same location
Patterns of neural processing
Serial processing
Something in series means you have something in STEPWISE order
Something in parallel is 2 series following a different path, but going to the
same location
Nearly all pathways have series
Example: reflexes - rapid, automatic responses to stimuli that
always cause the same response
Reflex arcs (pathways) have 5 essential components
○ Stimulus
1. Receptor
2. Sensory neuron
3. Integration center (interneuron)
4. Motor neuron
5. Effector
○ Response
Parallel processing
More complex than series
Allows you to receive different info coming into the same input
Input travels along several pathways
One stimulus promotes numerous responses
Important for higher-level mental functioning
Example: a smell may remind one of the odor and associated
experiences
You send info to different regions of the brain -
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Description
● G Protein-linked receptors - second messenger systems ○ Sits next to the membrane, inside the cell ○ Activation of g protein causes events, that activates a second messenger, which opens a channel ○ These cause formation of an intracellular second messenger (cyclic AMP in this case) that brings about the cell’s response ○ 1. Neurotransmitter (1st messenger) binds and activates receptor ■ When neurotransmitter binds to a receptor, the receptor changes shape ○ 2. Receptor activates G protein ■ G protein gets its name from GTP ■ GTP can be used as an energy source ● This is what powers the G protein ■ This causes G protein it to move ○ 3. G protein activates adenylate cyclase ■ Adenylate cyclase is an enzyme that uses ATP ■ Causes the molecule to form a circle ● Cyclic AMP ○ 4. Adenylate cyclase converts ATP to cAMP (2nd messenger) ■ cAMP stimulates things to happen inside the cell ○ 5a. cAMP changes membrane permeability by opening or closing ion channels ○ 5b. cAMP activates enzymes ○ 5c. cAMP activates specific genes ○ Does this system require energy to activate it? ■ YES!! GTP and ATP!! ● Neural Integration: Neuronal Pools ○ Functional groups of neurons that: ■ Integrate incoming information ■ Forward the processed information to other destinations ■ One presynaptic fiber synapses onto several post synaptic fiber ○ Simple neuronal pool ■ Single presynaptic fiber ranches and synapses with several neurons in the pool ■ Facilitated zone ■ Discharge zone ■ Presynaptic (input) fiber ○ Types of Circuits in Neuronal Pools ■ Diverging circuit ● One incoming fiber stimulates an ever-increasing number of fibers, often amplifying circuits ● May affect a single pathway or several ● Common in both sensory and motor systems ● Divergence to multiple pathways ● Divergence in same pathway ● Goes for 1>>2>>more ■ Converging circuit ● Opposite of diverging circuits, resulting in either strong stimulation or inhibition ● Also common in sensory and motor systems ● When there are a bunch of neurons synapsing onto one ● Convergence from multiple sources ● Convergence from a single source ■ Reverberating (oscillating) circuit ● Chain of neurons containing collateral synapses with previous neurons in the chain ● Helps regulate things like breathing ■ Parallel after-discharge circuit ● Incoming fiber stimulates several neurons in parallel arrays to stimulate a common output cell ● A variation of converging circuit, this one just has multiple steps, but has same basic outcome ● Something in series means you have something in STEPWISE order ● Something in parallel is 2 series following a different path, but going to the same location ○ Patterns of neural processing ■ Serial processing ■ Something in series means you have something in STEPWISE order ■ Something in parallel is 2 series following a different path, but going to the same location ■ Nearly all pathways have series ● Example: reflexes - rapid, automatic responses to stimuli that always cause the same response ● Reflex arcs (pathways) have 5 essential components ○ Stimulus ○ 1. Receptor ○ 2. Sensory neuron ○ 3. Integration center (interneuron) ○ 4. Motor neuron ○ 5. Effector ○ Response ■ Parallel processing ● More complex than series ● Allows you to receive different info coming into the same input ● Input travels along several pathways ● One stimulus promotes numerous responses ● Important for higher-level mental functioning ● Example: a smell may remind one of the odor and associated
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