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Chapter 3

PSYC 100 Chapter Notes - Chapter 3: Midbrain, Striatum, Enzyme


Department
Psychology
Course Code
PSYC 100
Professor
Russell Day
Chapter
3

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Psych 100
September 29
Chapter 3
Neurons: origin of behaviour
Neuron
Cells in the NS that communicate with each other, perform information processing tasks
Components of the Neuron
Three basic parts, disoered  “atiago Rao  Cajal i 88’s
Cell body (soma)
o Largest component
o Coordinated info-processing tasks, keeps cell alive
o Protein synthesis, energy production and metabolism here
o Contains nucleus
Houses chromosomes that contain DNA
o Surrounded by porous cell membrane to allow molecule flow
Dendrites
o Receive info from other neurons and relay to cell body
o Look like tree branches
Axon
o Carries info to other neurons, muscles and glands
o Can be very long
o Covered by myelin sheath
insulating layer of fatty material
composed of glial cells
o support cells found in NS
o 10-50 times more than neurons with many diff functions
Myelinated axon can transmit signals more efficiently
Demyelinating diseases (ie. MS)
Sheath deteriorates, slows transmission
Leads to loss of feeling in limb, partial blindness, cognition/ coordinated
movement problems
Aos/dedrites do’t touh
o Synapse
Small gap b/w axon of one neuron, dendrite/cell body of another
Trillions in our bodies
Major Types of Neurons
Sensory Neurons
Receive info from external world and convey to brain through spinal cord
Have specialized endings on dendrites
o to receive signals for light, sound, touch, taste and smell
ie. Sensory neurons in eyes have dendrites with ends sensitive to light
Motor Neurons
Carry signals from the spinal cord to muscle to produce movement
Long axons that can stretch to muscles
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Interneurons
Connect sensory/motor and other interneurons
most abundant in body
Some carry info from sensory into NS, other carry info from NS to motor
Neurons Specialized by Location
Ie. Purkinje cells are interneurons, carry info from cerebellum to rest of brain/spinal cord
o dense, elaborate dendrites that resemble bushes
Ie. Pyramidal cells are found in cerebral cortex, have triangular body and 1 long dendrite with many
smaller ones.
Ie. Bipolar cells are sensory neurons found in retina, have one axon and one dendrite
Electrochemical Actions of Neurons: Information Processing
Conduction
Movement of electric signal within neurons from dendrite to cell body, then throughout axon
Transmission
Movement of signal from one neuron to another over synapse
Electric Signaling
Resting potential
Difference in electric charge b/w inside and outside of cell membrane
Arises from difference in concentrations of ions inside and outside cell membrane
o height conc. of K and A inside, while high conc. of Na and Cl outside
negatives/positives cancel each other out
Conc. of K inside and outside is controlled by channels that allow it to flow in and out. In
resting state, channels open, while Na are closed. Some K leave neuron, giving it the
-70millivolts charge relative to outside
Action Potential
Eletri sigal that is oduted alog legth of euro’s ao to a sapse
o Only occurs when reached a certain threshold
action is all or none
stimulation below threshold does not produce signal, and stimulation much
higher tha threshold does’t irease stregth of sigal
o signal will produce with same characteristic and magnitude
Ours he there is hage i state of ao’s erae haels
o K channels get closed when charge raised to threshold
Na channels open, they flow inside neuron, increasing positive charge
pushes max action potential to +40 millivolts
Once max is reached, channels return to original state (K flows out until resting potential reached)
o in that period there is a lot of K outside and a lot of Na inside axon
called Refractory Period
Time following action potential when new action potential cannot be initiated
During ion imbalance period
o imbalance later reversed with active chemical pump that moves Na
outside axon and K inside axon
does not work during action potential
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Saltatory conduction
o Whe eletri urret passes do eliated ao, harge jups fro ode to ode
Myelin sheath has breaks in between
called nodes of Ranvier
Chemical Signaling
Terminal buttons
Knobs that branch out from axon
Neurotransmitters
Cheials that trasit ifo aross sapse to reeiig euro’s dedrites
Terminal buttons have vesicles filled with them
Receptors
Parts of cell membrane that receive neurotransmitters and initiate/prevent new electric signal
o Dendrites of receiving neuron have them
Presynaptic Neuron
Sending neuron
When K and Na flow across, they move it from resting to action potential
A.P moves to terminal buttons, stimulates release of neurotransmitters from vesicle to synapse
Postsynaptic Neuron
Receiving neuron
Neurotransmitters float through synapse and attach to receptors on dendrite
New A.P initiated, process continues to next neuron
Whole process called Synaptic Transmission, allowing neurons to communicate with each other
Once neurotransmitters do their jobs, they leave synapse in 3 processes
1. Reuptake
a. Neurotransmitter reabsorbed by terminal buttons of presynaptic neuron
2. Enzyme Deactivation
a. Neurotransmitters get destroyed in the synapse by enzymes
3. Autoreceptors
a. Receptor sites on presynaptic neurons that neurotransmitters bind to
i. receptors detect how much neurotransmitter released into synapse, signals stop
Types and Functions of Neurotransmitters
Acetylcholine (ACh)
o Voluntary motor control
Found in brain neurons and synapses of axons connecting muscle and body organs
Activates muscles to initiate motor behaviour
Also regulates attention, learning, sleeping, dreaming, memory
Alzheimer's is associated with deterioration of ACh producing neurons
Dopamine
o Regulates motor behaviour, motivation, pleasure and emotional arousal
Plays role in drug addictions
High levels linked to schizophrenia while low levels linked to Parkinson's
Glutamate
o Major excitatory neurotransmitter in the brain
Enhances transmission of info b/w neurons
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