control systems (pb lecture 17 – spring 2008 althoff ch. 34) nervous system
TRANSCRIPT
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Control Systems (PB Lecture 17 – Spring 2008 Althoff Ch. 34)
• Nervous system
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Systems of Control:ENDOCRINE & NERVOUS
• BOTH “SYNTHESIZE” MESSENGER CHEMICALS THAT ARE RELEASED INTO EXTRACELLULAR SPACES
Hormones Nerve cells
Distance to impact
Approach Target
Duration of impact
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Functions
• Messenger (receive stimuli)
• Communicator (process stimuli)
• The critical “network” for maintaining homeostasis…for advanced animals, this means they are “wired” for quick response
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Nervous System:
CNS = _____________________
(central nervous system)
vs.
PNS = all nerves & ganglia ________ the CNS
(peripheral nervous system)
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______ ______
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• Brain & spinal cord
• __________ sensory input, __________ response
• Nerves: carries sensory info to CNS and motor commands from CNS
• ______ to muscles & glands
CNS PNS
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Nerves
Bundles of nerve fibers outside the CNS, most notably the axon and dendrite(s) portion of neurons.
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Cell Types
• ___________--conducts nerve impulses
• ___________--supports and services neurons. Supplies nutrients, provides protection, and gets rid of waste
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Neuron Structure
CELL BODYDENDRITEAXONAXON ENDINGS (= axon terminals)MYELIN
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Neuron Structure
• CELL BODY --nucleus & most organelles• DENDRITE--receive incoming information
(i.e., stimulus)• AXON--carry information away from cell body• AXON ENDING --makes contact with other
neurons, muscles, glands • MYELIN--covering on some neurons
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3 Types of Neurons
__________ NEURON __________ NEURON _________________
(association neurons)
•Not all neurons look alike•Not all neurons carry the same
type of information
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Types of Neurons…con’t
• Consider types relative to CNS
• Collectively, they are the electronic communications network of the body….
…know these types as well as their relationship to one another!
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• Carry ________ info from periphery to CNS(i.e., PNS CNS)
• Both dendrite and axon are myelinated• ____________ is in the PNS• Examples: pain, pressure, touch, hot, cold,
light, sound, blood pressure, blood CO2, bladder stretch, etc.
SENSORY NEURON
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• Carry ___________________ from CNS to muscles or glands (i.e., CNS
PNS)• Skeletal muscles - causes contraction
Smooth muscles - “ “ Adrenal gland - secrete hormone
• Cell body is in the CNS, therefore, axon is usually ______
MOTOR NEURON
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• Found _____ inside the CNS
• Connects ___________ (sensory to motor and vise versa)
• Typically short dendrites and either long or short axons
INTERNEURONS(association neurons)
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PNS PNSCNS
Hand moves
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Nerve Impulse
A small ___________________ that occurs across the plasma membrane of neurons and then conducted along the axon/dendrite of the neuron
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RESTING POTENTIAL
NEURON AT REST
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RESTING POTENTIAL
NEURON AT REST
+40mV
-65mV
OUTSIDE
INSIDE
_____________________________________
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RESTING to __________________
During ACTION POTENTIAL, _____ channels open first, Na+ rushes in resulting in depolarization…then _____ channels open, K+ rushes out.
Na+
inK+
out
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Summary RESTING POTENTAIL
• Maintained at about -65mV by sodium-potassium pump (i.e., Na-K pump)
• _____ always diffusing back and forth because of ___________________
• Na+ higher outside an axon, K + higher inside the axon resulting in the axon having a negative charge
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ACTION POTENTIAL
• A rapid change in polarity across the plasma membrane as the nerve impulse occurs
• It is an “____________” phenomenon• If it causes depolarization to a certain
level, it is called a ____________ and an “action potential” occurs
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ACTION POTENTIAL…con’t
• Strength of an action potential does ____ change…
• …but an intense stimulus can cause the axon to fire at a ______________
• Requires two types of GATED CHANNELS: one for ____ and one for _____ . The Na+ channel opens first
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ACTION POTENTIAL…con’t
• During this process, Na+ moves to the inside of the axon during the depolarization phase (-65mV +40mV)
• K + moves to the outside of the axon during the repolarization phase. (+40mV -65mV)
• Review Fig. 34.5, pages 651 in Johnson and Losos
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Propagation of an Action Potential
• As action potential travels down the axon, each successive portion of the axon undergoes depolarization, followed by repolarization
• Like a _________________• As the action potential moves on, previous
portion goes through refractory period--Na+ channels are shut, then K + channels are shut
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Propagation of an Action Potential…con’t
• With refractory period (i.e., Na+ gate closed), the action potential _________________ ______________….just forwards
• At “nodes”, the action potentials jump from node-to-node. At nodes, voltage-sensitive Na+ channel gates are numerous. Speeds of _____ meters/second (_____ miles/hour) have been recorded along a motor neuron
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Synapse Structure & Function
• Where “signal” is transmitted from ____ _____________________
• Axon bulb synaptic cleft postsynaptic
neuron
• ___________________--molecules that transmit the signal across the synaptic cleft
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Presynaptic
neuronPostsynaptic
neuron
Synapse
(synaptic cleft)
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Neurotransmitters
• ____+ known substances or suspected to be neurotransmitters
• Acetylcholine (ACh) and Norephinephrine (NE) best known
• Acetylcholinestrease (AChE) is an enzyme that breaks down ACh
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Neurotransmitters
• Others include:dopamineserotoninopioids (endorphin)
• Many drugs either _________________ ________________________________
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Integration
• Neurons handle “excitatory” and “inhibitory” signals
• Each neuron sums up the two signal types in a process known as INTERGRATION
• Result: neuron either “fire” signal down axon…or not “fire signal
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