Transcript Myers Module Four

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Neural and Hormonal Systems
Everything psychological is simultaneously biological.
Phrenology, although seriously misguided, was a tentative
step in this direction.
Wrong-headed theory (m4.1p46,c2.1p48) in your text.
But! These areas in the brain are all interconnected,
making the brain the most complex structure in the known
universe.
The brain is not a computer! This is a common
misconception.
Neural and Hormonal Systems
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Neuron: the basic building block of the nervous
system.
Each consists of a cell body and branching fibres.
The dendrites are the bushy, branching
extensions that receive messages and conduct
impulses toward the cell body. For the biology
students: dendrites are complex microtubules,
proof that neurons are specializations from
simpler cell structures.
Axon: the neuron extension that passes
messagesthrough its branches to other neurons.
Neural and Hormonal Systems
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Myelin sheath: a layer of fatty tissue which insulates the
axon and speeds up the tranmission of neural impulses.
After age 25, this sheath deteriorates, leading in extreme
cases to multiple sclerosis.
Your brain is vastly more complex than a computer, but
slower at executing simple responses.
Commit Figure 4.2 p48 (c2.2p50)to memory; it is crucial to
understanding further material in this course.
This will need to be integrated with Web Article 1,
because of our new understanding of dendrites.
Neural and Hormonal Systems
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Figure 4.3(mp49, c2.3p51) Action potential.
Neurons generate electricity from chemical events:
electrically charged ions pump in and out of the axon.
The best way to understand how action potential works is
to do the Wave, in class, right now!
The change in charge is what travels down the axon, not
the chemicals themselves.
Google [“action potential animation”]
Eg: https://www.youtube.com/watch?v=iDgKqJbdiDk
Action Potential
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Neuron stimulation causes a brief change in
electrical charge. If strong enough, this produces
depolarization and an action potential.
This depolarization produces another action
potential a little farther along the axon. Gates in
this neighbouring area are now open, and sodium
ions rush in. The sodium/potassium pump in the
cell membrane transports the sodium ions back
out of the cell.
Action Potential
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As the action potential continues speedily down
the axon, the first section has now completely
recharged.
Each neuron is a miniature decision-making
device performing complex calculations as it
receives signals from hundreds, even thousands
of other neurons.
Excitatory signals push the message forward;
inhibitory signals stop it cold.
All-or-none. Neurons either fire, or they don't.
Synaptic Gap
Fig. 4.4 mp50, (c2.4p52)to memory;
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Action potentials travel down the axon until reaching a
tiny junction, the synapse.
Then, the action potential stimulates the release of
neurotransmitter molecules. They cross the synaptic gap
and bind to receptor sites on the receiving neuron. This
allows ions to enter the recieving neuron and excite or
inhibit a new action potential.
The sender neuron reabsorbs excess neurotransmitters.
This is reuptake.
https://www.youtube.com/watch?v=TevNJYyATAM
Serotonin & Dopamine
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Serotonin and dopamine are of the most interest to
psychologists, because they have the greatest effects on
high brain functions, primarily mood and language.
Serotonin is an endogenous opiate, or an endorphin.
Morphine, heroine, (and after a conversion at the bloodbrain barrier) alcohol are agonists to serotonin.
Dopamine also has several agonists, the best known
being lysergic acid diethylamide 25, or LSD.
Commit to memory: Fig 4.5 (mp51, c2.5p53)
Agonists & Antagonists : Acetylcholine
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Acetylcholine (Ach) plays a role in learning and memory.
In addition, it is the messenger at every junction between
motor neurons and skeletal muscles.
When Ach is released, the muscle contracts.
Curare is an antagonist of Ach, and is used to paralyze
fish, and the lips of Hollywood starlets, the wonder of
Botox.
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Commit to memory: Table 4.1 (mp52, c2.1p54)
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Commit to memory: Fig. 4.6 (mp53, c2.6p55)
Hormones are Thoughts Too
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Fig. 4.8 (mp55, c2.8p57)will be on the exam.
The autonomic nervous system controls our glands and
the muscles of our internal organs, influencing such
functions as glandular activity, heartbeat, and digestion. It
may be consciously overridden.
The sympathetic nervous system arouses and expends
energy. Heartrate, blood pressure, digestion, blood sugar,
and perspiration are controlled by it.
The parasympathetic system does the opposite.
Brains are not Computers
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The brain has some 40 billion neurons, each
connecting with 10,000 other neurons. That
creates 400 trillion synapses. And each synapse
is its own symphony orchestra of
neurotransmitters.
No modern, silicon-based microprocessor (like
the one in your smart phone) can come close to
this level of networking complexity.
The best analogy is to consider your brain as a
super-Internet.
The study of this complex connectivity is called
neural networking.
Back to Hormones!
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The endocrine system is the body's slow communications
system; a set of glands that secrete hormones into the
bloodstream.
Hormones are chemical messengers that are
manufactured by the endrocrine glands.
An example are the corticosteriods, which travel through
the bloodstream, and rebuild muscle tissues. After a
heavy workout, your hormonal system shifts into high
corticosteroid production.
For psychologists, the most important gland is the
hypothalamus, located in the middle brain.
Commit to memory: Fig. 4.11 (mp58,c2.11p60)