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Lecture

PSYCH101 Lecture Notes - Electric Charge, Neurotransmitter, Endorphins


Department
Psychology
Course Code
PSYCH101
Professor
Richard Ennis

Page:
of 2
25 September 2012
NEUROPSYCHOLOGY
THE NEURON
A single cell that is responsible for much of what happens in our brain (thoughts, feelings, and actions).
Three parts:
1) Soma The nucleus of the cell body.
2) Dendrites Branch-like fibres that come out of the cell body and between neurons.
3) Axon Elongated part that comes out of cell body; varies in size. Ends of them have terminal endings.
Information comes into the neuron from the dendrites (this process is called
afferent
).
Information leaves the neuron through the axon (this process is called
efferent
).
Three kinds:
1) Sensory neurons Carry messages from tissues/sensory organs inwards to brain and spinal cord.
Sensation process (taking the environment in) is an afferent process
Its dendrites are outside the central nervous system while axons are inside it
2-3 million sensory neurons
2) Motor neurons Efferent process information leaves the neuron through the axon
Allows us to perform actions by sending message to muscles
Dendrites are in the central nervous system while axons are in the muscles and glands
2-3 million
3) Interneurons Between sensory input and motor output, information is processed in brain's internal
communication system via interneurons
Exist entirely the central nervous system
Have no connections to sensory processes or muscles; only have contact with other neurons
10-100 billion
Neuronal Conduction
THE ELECTRICAL COMPONENT
Electrical charge travels down neuron's axon to transmit messages (called
action potential
).
Opposition said that a slight electrical charge would activate all the neurons instead of sending a
message to one specific neuron.
THE CHEMICAL COMPONENT
The way neurons communicate is solely chemical.
Galvani
: Italian physicist believed in electrical theory
o Experimented using a dead frog, attached a wire to its legs and passed direct current through
frog's legs and saw that it would jump.
Loewi
: tried to do an experiment to prove it was only chemical.
o Filled a beaker with distilled water, took a freshly removed heart from a frog and put it in the
water, attached electrode to heart and passed electrical stimulus through it, and the heart
started beating.
o In a second beaker, he had a second heart without water or electricity; he poured the water
from the first beaker into the second one and that one began beating (chemicals in distilled
water).
After Transmission
- 1950s: British neurologists theorized neuron communication is both electrical and chemical.
Neurotransmitters
The meeting point between neurons is called a synapse; dendrites and axons don't quite touch, but are
separated by synapses.
When action potential reaches the terminals at the end of an axon, chemical messengers are released
(neurotransmitters).
o These messengers close the gap for a split second, and then the sending neuron reabsorbs the
excess neurotransmitters (this process is called reuptake).
Excitatory signals must overtake inhibitory signals to trigger an action potential.
25 September 2012
Neurotransmitters can control depression, euphoria, hunger, addiction, etc.
Our brain naturally produces opiates in response to pain and vigorous exercise these are called
endorphins.
The problem with flooding our brain with unnatural opiates (heroin, morphine) is that our brain may
stop producing natural opiates, thus leading to a need for artificial opiates.
Drugs can also affect brain chemistry at synapses by amplifying or blocking a neurotransmitter's activity.
o Agonist molecules can be similar enough to a neurotransmitter to mimic its effects or block its
reuptake.
o Antagonist molecules block a neurotransmitter's functioning.
Neurotransmitter
Function
Examples of Malfunctions
Acetylcholine (Ach)
Enables muscle action, learning, memory
With Alzheimer's, Ach-producing neurons
deteriorate.
Dopamine
Influences movement, learning, attention,
emotion
Excess dopamine -> schizophrenia
Serotonin
Affects mood, hunger, sleep, arousal
Too little is linked to depression.
Norepinephrine
Helps control alertness / arousal
Too little can depress mood.
GABA (gamma-amino butyric acid)
Major inhibitory neurotransmitter
Too little linked to seizures, tremors,
insomnia.
Glutamate
Major excitatory neurotransmitter; involved
in memory
Oversupply can overstimulate brain
migraines and seizures.
THE NERVOUS SYSTEM
The body's electrochemical communication network
Brain and spinal cord form the central nervous system while the body's sensory receptors, muscles, and
glands form the peripheral nervous system.
The Peripheral Nervous System
Made up of two components: somatic and autonomic.
SOMATIC NERVOUS SYSTEM enables voluntary control of our skeletal muscles
AUTONOMIC NERVOUS SYSTEM controls glands and muscles of internal organs; operates on its own
o Have two functions:
sympathetic nervous system
(arouses/expends energy) and
parasympathetic nervous system
(conserves energy and calms you down).
The Central Nervous System
The brain's neurons cluster into work groups called neural networks that communicate with each
other.
The spinal cord connects the peripheral nervous system to the brain; ascending neural fibers send up
sensory information while descending fibers send back motor-control information.
o Example: the neural pathways that control our reflexes.
Some reflexes involve very simple neural pathways, which is why you jerk your hand away from a flame
before your brain receives the message that the fire is painful.
The Endocrine System
Interconnected with nervous system; secretes hormones which travel through our bloodstream and
affect other tissues.
Nervous system and endocrine system are similar in all aspects EXCEPT the signals from hormones
travel slowly through our bloodstream while the nervous system's messages are much faster.
Most influential endocrine gland is the pituitary gland which is located in the core of the brain and
releases chemicals that affect growth, release of hormones by other glands, etc.
The nervous system direct endocrine secretions which then affect the nervous system.