Download pdf - PSY150 Ch03 Neuro 2012

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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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• Neuroanatomy


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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 Cell body: (Gray)

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ANATOMY OF A NEURON Dendrites

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ANATOMY OF A NEURON Axon (White)

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ANATOMY OF A NEURON Myelin

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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



• Neuroanatomy


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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



• Neuroanatomy


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ACTION POTENTIAL: ALL OR NONE SELF-PROPAGATING

Nodes of Ranvier

/Hyperpolarization

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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



• Neuroanatomy


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SYNAPSE

NEUROTRANSMITTER RELEASE

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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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•  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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• Neuroanatomy


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PARTS OF THE NERVOUS SYSTEM

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HINDBRAIN & MIDBRAIN

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FOREBRAIN

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CEREBRAL CORTEX

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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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• Neuroanatomy


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STUDYING THE BRAIN Neurosurgery

• Epilepsy • Wilder Penfield • Split brain - Sperry

EEG

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IMAGING

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MRI PET