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

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University of South Carolina
Exercise Science
EXSC 224

● 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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