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BIOLOGICAL PROCESSES
CHAPTER 3
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LEARNING GOALS Discuss how the nervous system communicates internally.
• Describe the structure and function of neurons • Describe how the neuron transmits information • Describe the action potential, the neurotransmitters, and the synapse • Describe how drugs and other substances affect transmission and
alter behavior Discuss how the nervous system initiates and coordinates behavior efficiently
• Describe the basic organization of the nervous system • Describe the major structures of the brain and their related functions
Discuss how growth and internal functions are regulated in the body through the endocrine system (book)
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BIOPSYCHOLOGY/ NEUROSCIENCE Biopsychology – interaction between behavior, brain, and environment Neuroscience – several sciences interested in brain function
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OUTLINE • Genetics • Communication in the nervous system
• Resting Potential • Action Potential • The Synapse
• Neuroanatomy
• Studying the Brain
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GENETICS AND THE BRAIN How did we get these brains? Brain is the product of a biological heritage Evolution
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Environmental pressure (changes in the environment)
Competition (for resources)
Selection of fittest phenotype (from among a variety of phenotypes)
Reproductive success (genotype corresponding to fittest
Phenotypes passed to next generation)
Frequency of that genotype increases (in next generation)
GENETICS IN PSYCHOLOGY Behavioral genetics
• Intelligence, personality, abnormal behavior – schizophrenia
• Very complex, with multiple factors that interact
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OUTLINE • Genetics • Communication in the nervous system
• Resting Potential • Action Potential • The Synapse
• Neuroanatomy
• Studying the Brain
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FUNCTION OF A NEURON Reception - take info from neighboring neurons Conduction (integrate signals) Transmission (pass on to other neurons)
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ANATOMY OF A NEURON Synapse
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4 COMMON COMPONENTS OF A NEURON
Dendrites – input, receives neurotransmitters Soma – processing Axon – transmits signal Terminal Buttons – output, release neurotransmitters to target Myelin Sheath – insulates axon Synapse - junction between neuron and target
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TRANSMISSION and Neurotransmitter RELEASE
INPUT and PROCESSING Transmitter-gated receptor channels
EPSP / IPSP produced by ion entry & exit
Temporal & Spatial summation occurs in the soma
OVERVIEW OF NEURON COMMUNICATON
COMMUNICATION IN THE NERVOUS SYSTEM • Electrical Signals
– Discrete on/off signal – Fast over long distances – Caused by movement of
positive (Na+, K+) or negative (Cl-) salt ions in or out of the neuron
– 2 types: synaptic potentials action potentials
• Chemical Signals between neurons:
– Neurotransmitters – Slower but only used for
short distance (synapse) – Chemicals provide
selectivity that electricity does not have due to lock and key binding
as hormones: – Sustained effects
throughout body
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ANATOMY OF A NEURON Nodes of Ranvier Salutatory Action video
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http://www.youtube.com/watch?v=pnB_Hc-Qfs0&feature=related 18
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STRUCTURE OF THE AXON
Semi-permeable cell membrane: 10nm thick Ion channels are selectively permeable Ions inside and outside membrane
OUTLINE • Genetics • Communication in the nervous system
• Resting Potential • Action Potential • The Synapse
• Neuroanatomy
• Studying the Brain
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RESTING POTENTIAL • -70mV • Outside positive (+) relative to inside • Primary ions involved
• Na+
• K+
• Cl - • Ca++ (axon terminals)
RESTING POTENTIAL • Resting potential (charge inside the cell) is maintained at -70mV (this makes for an easy and quick response) • This in an active process with Na+ and K+ pumps in the cell wall constantly moving ions to maintain the concentration imbalance
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RESTING POTENTIAL
http://www.youtube.com/watch?v=YP_P6bYvEjE
http://www.youtube.com/watch?v=YP_P6bYvEjE
OUTLINE • Genetics • Communication in the nervous system
• Resting Potential • Action Potential • The Synapse
• Neuroanatomy
• Studying the Brain
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FACTORS THAT PRODUCE THE RESTING POTENTIAL
Ion channels with voltage-sensitive gates
ION FLOW DURING THE ACTION POTENTIAL
• Sodium channels open • Threshold passed? • Depolarization: Moves from –70mV to +50 mV • Potassium channels open • Sodium channels close • Potassium channels close
Threshold -55 mV
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ACTION POTENTIAL
http://www.youtube.com/watch?v=ifD1YG07fB8&NR=1
OUTLINE • Genetics • Communication in the nervous system
• Resting Potential • Action Potential • The Synapse
• Neuroanatomy
• Studying the Brain
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SYNAPTIC EVENTS
CHEMICAL SIGNALING Chemical messengers – lock and key Action depends on the lock Allows:
• Two neurons to send different signals to the same target (heart muscle under NE and ACh).
• Two synapses can be very close and not interfere with each other (no cross-talk)
Different neurotransmitters are used in different locations for different purposes
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COMMUNICATION AT THE SYNAPSE
http://www.youtube.com/watch?v=HXx9qlJetSU
NEUROTRANSMITTER • Acetylcholine (ACh): Parasympathetic nervous system. Induces calm, stimulates muscles, involved in Alzheimer’s dementia • GABA: main brakes in the brain. Involved in anxiety (low levels associated with panic-like feelings, higher levels involved in relaxation). • Dopamine (DA): Involved in movement and attention. Low levels in Parkinson’s disease, higher levels associated with schizophrenic like behaviors. • Serotonin (5-HT): Mood and arousal. High levels with sedation, low levels with depression • Glutamate (GLU): Memory • Endorphins: Pain and pleasure
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COMMON DRUG ACTIONS
Agonist increases the effect of a neurotransmitter Antagonist decreases the effect of a neurotransmitter Ways drugs can be Agonists:
• Mimic the neurotransmitter and artificially activate the receptors • Increase the production of neurotransmitter • Inhibit metabolism or enzymatic breakdown of neurotransmitter • Inhibit or block neurotransmitter reuptake from synapse • Increase the release or amount of neurotransmitter in vesicles
Ways drugs can be Antagonists • Block access to the receptor • Inhibit production of the neurotransmitter • Breakdown or inactive neurotransmitter (speed metabolism) • Cause neurotransmitter leakage from vesicles
DRUGS WORKING AT DOPAMINE SYNAPSE
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POST-SYNAPTIC MEMBRANE EFFECTS
Presynaptic Neuron
Postsynaptic Neuron
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EPSP VS IPSP
http://www.youtube.com/watch?v=LT3VKAr4roo 40
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OUTLINE • Genetics • Communication in the nervous system
• Resting Potential • Action Potential • The Synapse • Overview
• Neuroanatomy • Studying the Brain
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TRANSMISSION and NT RELEASE
INPUT and PROCESSING Transmitter-gated receptor channels
EPSP / IPSP produced by ion entry & exit
Temporal & Spatial summation occurs in the soma
OVERVIEW OF NEURON COMMUNICATION
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SYNAPTIC POTENTIAL (INPUT) • Function: Turns a chemical signal (neurotransmitter) into an electrical signal • Location: Primarily in the dendrites • Resting potential (charge inside the cell) is maintained at -70mV (this makes for an easy and quick response) • This in an active process with Na+ and K+ pumps in the cell wall constantly moving ions to maintain the concentration imbalance • Excitatory post synaptic potential = more positive, depolarization • Inhibitory post synaptic potential = more negative, hyperpolarization
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SIGNAL PROCESSING (PROCESSING) Function: Decision to send an action potential or not based on strength of synaptic potential Location: Axon soma (axonal hillock) The decision is based on whether the synaptic potential reaches -50mV Temporal summation: enough signals arrive in short time that it leads to a decrease in the synaptic potential (move faster than the pump) Spatial summation: enough signals arrive from different neurons that the sum exceeds the threshold
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ACTION POTENTIAL (TRANSMISSION) Function: Output transmission Location: Axon to terminal buttons All-or-nothing, like a gun
Unlike the synaptic potential that is regulated by chemicals, the action potential is voltage regulated Na+ opens and enters
K+ opens and enters
Na+ closes and K+ stays open Pump works
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OUTLINE • Genetics • Communication in the nervous system
• Resting Potential • Action Potential • The Synapse
• Neuroanatomy
• Studying the Brain
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CEREBRAL CORTEX
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CLINICAL OBSERVATIONS
Paul Broca • Observed brain lesion in
left hemisphere of patient with aphasia
Carl Wernicke • Observed man whose
language made no sense
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CLINICAL OBSERVATIONS Phineas Gage
• Famous case • Railroad worker • Localized brain
damage • Inappropriate social
and moral behaviors • Attention and memory
fine
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EVIDENCE OF LATERALIZATION SPLIT BRAIN PATIENTS
Some types of epilepsy start in one area of the brain (focus) and spread to other areas. Today, 90% of epilepsy cases are treated with drug therapy. Surgery to remove the epileptic focus or cutting the corpus callosum is rarely used as a last resort.
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OUTLINE • Genetics • Communication in the nervous system
• Resting Potential • Action Potential • The Synapse
• Neuroanatomy
• Studying the Brain
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STUDYING THE BRAIN Neurosurgery
• Epilepsy • Wilder Penfield • Split brain - Sperry
EEG
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