Download - Central Nervous System
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Central Nervous System
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Central Nervous System (CNS) Consists of the brain and spinal cord Integrates and processes information
by nerves
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Peripheral Nervous System (PNS) Divided into Somatic and Autonomic
systemsSomatic Nervous System (Voluntary) Consists of sensory receptors Nerves that carry sensory information or
instructions to the CNS to the skeletal muscles
Autonomic Nervous System (Involuntary) Controls glandular secretions Sympathetic and parasympathetic
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Autonomic Nervous System (Involuntary)
Autonomic Nervous System
• Sympathetic nervous systemallow body to function under stressfight or flight
• Parasympathetic nervous systemcontrols vegetative functionsfeed or breed or restconstant opposition to sympathetic system
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The Organization of the Brain
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Cells of the Nervous System Two main cells:
1) Neurons Specialized cells to respond to
physical and chemical stimuli Release chemicals that regulate
various body processes Individual neurons are organized
into tissues called nerves
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Cells of the Nervous System Cont…
2) Glial Cells Supports the nervous system tissue Removes waste Defend against infections
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The structure of a neuron Specialized cell structures that enable
them to transmit nerve impulses Features:
1) Dendrites Receive nerve impulses from other
neurons and sends back to the cell body 2) Cell body Site of metabolic reactions Processes input from dendrites and
sends to the axon
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The structure of a neuron cont…3) Axon Conducts impulses away from the
cell body Releases chemical signals to the
receptors and dendrites Myelin sheath protects the neuron
and speeds up the rate of nerve impulse transmission
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Classifying Neurons
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Nerve Impulse Generation and Resting Membrane Potential
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Nerve Impulses Galvani and Volta performed experiments using
leg muscles Muscles contracted after experiencing
stimulation from electric currents Resting neuron: the outside of the cellular
membrane is negative, relative to the inside This causes a potential difference between the
inside and outside of the neuron
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More on Resting Potential
Potential difference across the membrane of a resting neuron
Remains relatively constant for all neurons, approximately -70 mV
Controlled by electrochemical gradients, protein presence and active transport
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Electrochemical Gradient Large, negatively charged proteins cause
the inside of the membrane to be charged
Potassium and sodium ions control the electrochemical gradient
Gradient is adjusted, maintained and controlled through active transport
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Blue – SodiumYellow – ChlorineOrange – AnionsPurple - Potassium
Controlled by various channel proteins such as the one used for potassium shown in the diagram
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Action Potential
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What Is It?
Movement of electrical impulse
Rapid change in polarity
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html
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History
Discovered by 2 British Scientists Used giant squid Revealed that action potential is
dependant on voltage gated Na and K channels
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When does this occur?
Occurs when Threshold Potential occurs
Threshold Potential Varies
Strength of stimulus does not = strength of Action Potential
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Events
Action Potential triggered by Threshold Potential
Voltage gated Sodium channels open Sodium channel closed Potassium
Channels open Potassium Channels closes after
hyperpolarization Membrane Potential brought back to
-70mV
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Does natural = safe? Natural and synthetic neurotoxins work by
blocking the “action potential” Tetrodoxin (pufferfish) blocks sodium
channel Dendrotoxin (black mamba) blocks
potassium channel Applications: chemical weapons?
Insecticides?
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Extended Information
Tetraodontidae (Pufferfish)
Contains Tetrotoxin (1200x more poisonous than cyanide)
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Synaptic Transmission
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Synaptic Transmission
Postsynaptic neuron
Presynaptic neuron
Synaptic cleft
(protein)http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__chemical_synapse__quiz_1_.html
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Reflex Arc
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Reflex Arc and Feedback
Reflex arc: simple connection of neurons that results in a reflex action in response to a stimulus
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Your nervous system reacts to sensory input through a basic impulse pathway
Reflexes: Sudden involuntary responses to certain stimuli
Requires 3 neurons (sensory input, integration, motor output)
Reflex Arc and Feedback
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Sensory Input Neuron
Sensory receptors such as those in the skin, receive stimuli and form a nerve impulse
Sensory neurons transmit impulses from the sensory receptors to the central nervous system
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Integration Neurons
Interneurons are found entirely within the central nervous system
They act as a link between the sensory and motor neurons
They process and integrate incoming sensory information and relay outgoing motor information
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Motor Output
Motor neuron transmits information from the central nervous system to effectors
Effectors include muscles, glands and other organs that respond to impulses from motor neurons
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Putting it all together
1. receptors in skin sense the pressure or temperature change
2. Impulse is carried by the sensory neurons then activates the internuron in the spinal cord
3. The interneuron signals the motor neuron to instruct the muscle
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Loss of Homeostasis
What can be seen through synaptic transmission? Parkinson’s Dopamine▪ Controls body movements▪ Sensations of pleasure
Serotonin▪ Regulates temperature and sensory
perception ▪ Depression
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Deep Brain Stimulation
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Take Home Message
Synapse = connection between neurons or neuron and effector
Impacts homeostasis through neurotransmitters Movement Temperature Natural painkilling Danger/stress reactions