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Chapter 3

PSY BEH 11A Chapter Notes - Chapter 3: Functional Magnetic Resonance Imaging, Axon Terminal, White Matter


Department
Psychology and Social Behavior
Course Code
PSY BEH 11A
Professor
Donald Hoffman
Chapter
3

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CHAPTER 3: BIOLOGY & BEHAVIOR
โ— multiple sclerosis: disorder of nervous system that is typically diagnosed between
the ages 20-40
โ—‹ affects brain & spinal cord โ†’ movements become jerky & lost
coordination
โ—‹ help us understand how nervous system is critical in our ability to think &
behave normally
3.1 HOW DOES THE NERVOUS SYSTEM OPERATE?
โ— nervous system: responsible for everything people think, feel, do
โ—‹ basic unit: nerve cells (๎€neurons๎€): receive, integrate, transmit info in NS
โ—‹ communicate selectively with other neurons to form circuits, ๎€neural
networks
THE NERVOUS SYSTEM HAS TWO BASIC DIVISIONS
โ—central nervous system (CNS)๎€: consists of brain & spinal cord
โ—‹ organizes & evaluates info โ€”> directs PNS to perform specific behaviors
โ—peripheral nervous system (PNS)๎€: consists of al the other nerve cells in rest of
body
โ—‹ sends info to CNS
โ—‹ somatic nervous system: voluntary behavior
โ—‹ autonomic nervous system: less voluntary actions
NEURONS ARE SPECIALIZED FOR COMMUNICATION
โ— excitable: powered by electrical impulses & communicate with other nerve cells
through chemical signals
โ—‹ reception phase: take in chemical signals from neurons
โ—‹ integration: incoming signals are assessed
โ—‹ transmission: pass their own signals to yet other receiving neurons
โ— 3 types of neurons
โ—‹sensory๎€: detect info from physical world & pass info along to brain,
through spinal cord
โ–  provide info from skin and muscle: ๎€somatosensory nerves
โ—‹motor๎€: direct muscles to contract/ relax
โ—‹interneurons๎€: communicate within local or short-distance circuits
โ–  integrate neural activity within single area rather than transmitting
info to brain structures or body organs
โ—‹ reflexes: auto motor responses; occur before we even think about those
responses

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โ— 4 structural regions of neuron
โ—‹dendrites๎€: short, branch-like appendages that detect chemical signals
from neighboring neurons
โ—‹cell body๎€ (soma): info received via the dendrites from thousands of other
neurons is collected & integrated
โ—‹axon๎€: vary in length
โ–  longest: from spinal cord to big toe
โ–  end of axon: ๎€terminal buttons
โ—‹synapse๎€: site where chemical communication occurs between neurons
โ–  send chemicals into synapse
โ— neuron covered with ๎€membrane๎€: fatty barrier that does not diesel e in watery
environment inside/ outside neuron
โ—‹ semipermeable
โ—‹ ion channels: allow ions to pass in/ out of cell
โ—‹ important role in communication between neurons: regulates
concentration of electrically charged molecules that are basis of neuronโ€™s
electrical activity
THE RESTING MEMBRANE POTENTIAL IS NEGATIVELY CHARGED
โ—resting membrane potential๎€: difference in electrical charge occurs bc ratio of
negative to positive ions is greater INSIDE than outside
โ—‹ inside: -70 mV
โ—‹ polarized: inside > outside in negativity
โ— ions that contribute to resting membrane potential: ๎€sodium๎€ & ๎€potassium ๎€ions
โ—‹ ions pass through neuron membrane at ion channels
โ–  controlled by gating mechanism. when open: ions flow in/ out
โ–  also affected by selective permeability (allows some to pass
more easily โ†’ K > Na inside neuron)
โ—‹sodium-potassium pump๎€: increases K and decreases Na inside neuron
ACTION POTENTIALS CAUSE NEURAL COMMUNICATION
โ—action potential๎€ (neural firing): electrical signal that passes along axon
โ—‹ causes terminal buttons to release chemicals that transmit signals to other
neurons
โ— neuron receives chemical signals from other neurons. affecting polarization โ€”>
whether to fire
โ—‹excitatory signals๎€: depolarize membrane (decrease polarization by
decreasing negative charge)
โ–  increase neuron firing

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โ—‹inhibitory signals๎€: hyperpolarize cell (increase polarization by increasing
negative charge)
โ–  decrease neuron firing
โ—‹ if amount surpasses threshold (-55 mV), action potential generated
โ— if neuron fires, Na gates open โ†’ Na goes in (more positive) โ†’ K channels open
to go out
โ—‹ during process, electrical charge inside cell starts out slightly negative in
resting state โ†’ becomes positive
โ— when fires, depolarization moves along axon like wave
โ—‹myelin sheath๎€: encases & insulates many axons like plastic tubing
around wires
โ–  made up of ๎€glial cells (glia)
โ–  grows along axon in short segments. gaps in between: ๎€nodes of
ranvier๎€. action potential skips thru axon, recharging at each node
โ–  without it, Na channels of membrane must open (speed is slower
though)
โ—all-or-none principle๎€: dictates that a neuron fires with the same potency each
time
โ—‹ the stronger the stimulation (how often it fires), he more frequently it fires
action potentials
NEUROTRANSMITTERS BIND TO RECEPTORS ACROSS THE SYNAPSE
โ—presynaptic neuron๎€: neuron that sends the signal
โ—postsynaptic neuron๎€: receives signal
โ—neurotransmitters๎€: inside terminal button. chemicals that are made in axon &
stored in vesicles
โ—‹ when released, convey signals across synapse to postsynaptic
โ— action potential โ†’ terminal button, causes vesicles to attach to presynaptic
membrane & release NT into synapse โ†’ travel across & bind to receptors on
postsynaptic
โ—‹receptors๎€: specialized protein molecules located on postsynaptic
membrane that specifically respond to chemical structure of NT available
โ–  causes ion channels to open/ close โ†’ excitatory/ inhibitory
โ— once NT released, continues to bind/ blocks new signals until influence is
terminated
โ—‹ 3 major events that terminate NTโ€™s influence
โ–  1. ๎€reuptake๎€: when NT is taken back into presynaptic terminal
buttons
โ–  into synapse & back for recycling
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