Transcript Mod 3 Part 2

NEURAL COMMUNICATION
How does one neuron communicate with another?
 Original belief was that axons and dendrites were fused
 Cajal noticed gaps between nerve cells
 Sherrington noticed interruptions in the neural pathways
 Synapse (Synaptic gap, synaptic cleft)
 Space between sending axon and receiving dendrite
 “Protoplasmic kisses”
 Neurotransmitters (chemical messengers)
 Released by axon
 Attach to receptor sites in the dendrite
 Lock and key
 Unlocks channels to send ions into the axon, thus sending signal to the next
 Excess neurotransmitters are reabsorbed into the sending neuron (reuptake)
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SYNAPSE
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ACHETYLCHOLINE AND ENDORPHINS
Acetylcholine
 Key role in learning and memory
 Messenger between every motor neuron and muscle
 causes muscle contraction
 Poisons that affect Ach
 Curare can block reception of Ach and in effect paralyze an animal
 Botulin stops release of Ach from sending neuron
 Black widow spider venom causes synaptic flood of Ach
Endorphins
 Discovery of opiates attaching to receptors in areas linked to mood and pain
(Snyder 1973)
 Endorphins are the key to the opiate lock (endogenous morphine)
 Adrenaline
 Runners’ high
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HOW DRUGS AND OTHER CHEMICALS AFFECT
NEUROTRANSMITTERS
Drugs often mock neurotransmitters
 Neurons are flooded
 Body shuts down production
 Detox problems
 Lingering side effects
 Addiction
 Agonists excite the neuron
 Antagonists inhibit the neuron
Some scientists attempt to create drugs that mimic neurotransmitters that are out of
balance
 Blood-brain barrier keeps most unwanted chemicals out
 L-dopa as a treatment for Parkinsons
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THE NERVOUS SYSTEM
The Nervous Sytem: The body’s primary information system
 Central nervous system: the brain and spinal chord
 The peripheral nervous system: links central nervous system with sense receptors,
muscles, and glands
 Nerves: the motor axons that carry the information
 Optic nerve: million axons bundled together into a single cable carrying
information from each eye (Mason and Kandel (1991)
 Three types of neurons
 Sensory neurons: sends information from the body’s tissues and sensory
organs to the brain
 Interneurons: allow internal communication for the central nervous system
 Motor neurons: sends information from the central nervous system to the
body’s tissues
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THE PERIPHERAL NERVOUS SYSTEM
Somatic Nervous System: Controls the movement of skeletal muscles
Autonomic Nervous System: controls the glands and the muscles of internal organs
Sympathetic Nervous System: arouses people for defensive action
 Accelerate heartrate
 Slow digestion
 Raise blood sugar
 Dilate arteries
 Cool with perspiration
Parasympathetic Nervous System: opposite of sympathetic nervous system
 Slows heartrate
 Speeds digestion
 Lowers blood sugar
 Dilate arteries
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THE CENTRAL NERVOUS SYSTEM
Spinal cord and Brian
 Information superhighway
 Reflexes: automatic responses
 Simple pathway is one motor and one sensory neuron
 Knee-jerk
 pain (often felt AFTER the reflex)
 Effects of severing spinal cord
 No feeling below the point of injury
 Reflexes still occur without the brain registering the pressure sensor
 Sexual response
 Genitals are still reflexive (Goldstein 2000)
 No reaction to sexual imagery (Kennedy and Over 1990, Sipski et al 1999)
Neural Networks
 Brian receives information, interprets it, and decides responses
 300 trillion cortical-synaptic connections (Rachmachadran and Blakesly 1998)
 Neural networks: clustered work groups
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THE ENDOCRINE SYSTEM
Endocrine System: the body’s second communication system
Hormones originate in one tissue and use the bloodstream to affect other tissues
 Glands secrete hormones (another form of chemical messenger)
 Much slower than the nervous system
 Adrenal glands (top of kidneys
 Produce epinephrine and norepinephrine to control arousal
 Provide surge of energy when needed
 Pituitary Gland
 Controlled by the hypothalamus
 Releases hormones that influence growth
 Influences release of other hormones from other glands
 “master gland”
 Triggers release of sex hormones
Feedback loop: Brain -> pituitary -> other glands -> hormones -> brain
Distinction often fuzzy, as sometimes neurotransmitters can act like hormones (Agnati et al 1992,
Pert 1986
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EXIT TICKET AND HOMEWORK
Exit Ticket
 What are neurons and how do they transmit information?
 How does a neuron communicate with other cells to influence behavior?
 What are the elementary components of our nervous system?
 What are the functional divisions of our nervous system?
 How does the endocrine system deliver its messages?
Homework:
 Complete diagram packet
 Read Pages 68-75
 Be prepared for Quiz
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