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My approach to this is to start with the whole organ-- the brain-- and introduce the parts and what they do followed by the things that make up the brain and make it work (the neurons and neurochemicals). Once we've established these pieces, we will then work through how emotions work in relation to these systems.

Nervous system (SLIDE 1):

(Click on this thumbnail to see a larger version of this picture)

As Slide 1 (above) shows, the nervous system is made up of several parts. The greenish areas represent the Central Nervous System (CNS), which is made up of the areas encased by bone-- the brain and spinal cord. The purplish areas represent the Peripheral Nervous System (PNS), which includes the rest of the nervous system ("peripheral" referring to the body outside the CNS). As you can see, the PNS contains the somatic nervous system (associated with sensation and movement) and the autonomic nervous system, which is yet broken further into the sympathetic and parasympathetic nervous systems.

The CNS and autonomic systems will be what we will focus on the most.

Let's look at the brain-- organizing system; interpreter

We will now take a brief tour of the brain. Although I include pictures and diagrams, I am not interested in your being able to point out the structures on a diagram. I will be interested in your knowing different structures' functions. (The diagrams can help you determine functions. You should note that more basic functions (e.g., breathing) are controlled by lower areas of the brain whereas more complex activities are governed higher up. Also, neighboring brain structures will relate to each other.)

Overview slide:
(click to enlarge)

See the brain part descriptions in the text (pp. 85-92).


Slide 2 This diagram shows the locations of the major brain areas. Look at this in relation to the functions described in the text and in the overview slide.	Slide 3 This close-up of the hindbrain and midbrain areas shows the areas that control vital functions such as breathing, cardio- vascular function, and balance.	Slide 4 In the center of this diagram is the hypothalamus. It's the brain part responsible for maintaining the body's homeostasis-- by controlling basic drives related to eating, drinking, sexual activity, etc. Look at it in relation to the hindbrain and the limbic system in the next diagram. It's the link between emotions (limbic system) and bodily responses (e.g., medulla).	Slide 5 The Limbic System is several brain areas that are geared toward controlling emotions. The inclusion of the hippocampus shows the importance of memory with emotion-- strong emotions facilitate memory and important memories stir emotions. Both emotion and memory shape motivations. Motivations are drives to engage in a behavior-- again, you should note the role of the hypothalamus in making this type of drive state occur.

Let's work with the Autonomic Nervous System (pp. 101-102 in text).

The two branches of the Autonomic Nervous System-- the sympathetic and parasympathetic branches-- work in opposition to each other in order to keep the body's vital systems (e.g., cardiovascular, metabolic) working in balance. (Another term for that internal balance is homeostasis.)

	The sympathetic branch is geared toward energy expenditure-- getting the body ready to respond (the "fight or flight" response) by moving blood to the muscles and releasing stored energy. This system not only becomes activated physical need demands is (e.g., exercise), but also during strong emotions (fright, joy, anger, lust, excitement).
	The parasympathetic branch is geared toward energy conservation and "refueling" by stimulating digestion while decreasing blood flow to the muscles. While not associated with emotion as much as the sympathetic branch is, fainting is a symptom of an over-reaction by the parasympathetic system.

See the images below to get a sense of how the branches of the autonomic nervous system are organized and how they act on the body:

Slide 6	Slide 7	The image on the left shows the basic set-up of the two branches of the Autonomic Nervous System (the Sympathetic and Parasympathetic nervous systems). The second slide shows more clearly the effects of the two opposing systems on some of the body's functions.
(Click on images to enlarge)

So what does the autonomic nervous system have to do with mental states?

Strong emotions involve changes in the way the body feels. For example, could you imagine riding a roller coaster and not feeling the heart pounding, sweating, etc.? Or a much-anticipated date? The emotional impact is blunted without the physical feedback. Likewise, drugs manipulate these feelings as well as brain activity.

Several of the most-used or abused drugs are described as "sympathomimetics"-- that is, they mimic, or copy, the effects of the sympathetic nervous system. These would include all the stimulants (cocaine, amphetamine, caffeine, nicotine). Others work to reduce sympathetic activity, such as the antianxiety drugs (e.g., Valium).

This means, that these drugs push the body out of homeostasis (balance)-- and that people deliberately take these drugs for that reason (hence the popularity of coffee shops).

Similarly, our emotional states push our bodies out of homeostasis, in part as a way to prepare for the whatever it is that has caused the emotion (e.g., a dog barking at us leads to startle or fear responses that require the body to prepare to move!) Stress can be seen as an emotional response of this type. Where problems exist is when this push from homeostasis persists over time-- requiring extra work on the part of the body.

Neuotransmitters (see pp. 96-98)

The brain is made up of over a trillion nerve cells (neurons) that communicate through the release and reception of chemical messengers. As described in the text, one type of messenger is called neurotransmitters, which are chemical substances that are stored in the terminal end of a neuron (see diagram on p. 97 and another one below), that are released when the storing neuron "fires," and have the potential to influence the activity of a receiving cell (either increasing or decreasing its likelihood of action).


Slide 8 This image shows two neurons, their structures, and where neurotransmitters are stored and released (at the synapse).	Slide 9 This slide is a close-up of one synapse. The box inside this picture shows where two neurons meet-- the upper one releasing neurotransmitters into the synapse; the lower one receiving those chemicals at receptors.

While there may be over fifty neurotransmitters, up until recently only a handful have been recognized and the majority of research and focus has been on those. The following table summarizes the main ideas about the neurotransmitters:

Summary of transmitters

PRIMARY TRANSMITTERS:

Transmitter	Primary Locations and Actions	Health Issues	Drugs Associated with Transmitter
Acetylcholine	Peripheral: � All neuromuscular junctions � Released by parasympathetic system CNS: � Memory, sensory processing, motor coordination	Paralysis if levels too low; muscle spasms if too high; Alzheimer�s disease with undersupply in CNS.	Nicotine Atropine (belladonna) Curare
Dopamine	� Regulation of hormonal balance � Voluntary movement � Reward	Schizophrenia (with high levels); Parkinson�s (if levels too low)	Cocaine Amphetamines
Gamma-amino butyric acid (GABA)	Primary CNS inhibitory transmitter	Seizures (if levels too low); Huntington�s disease destroys GABA cells, causes tremors, personality changes	Depressants
Glutamate	Primary CNS excitatory transmitter	Possible role in schizophrenia, learning disorders; Excess levels can produce cell death	PCP
Norepinephrine	Periphery: � Released by sympathetic n.s., �fight or flight� response. CNS: � Positive mood and reward � Orienting and alerting responses � Basic instincts (sex, eating, thirst).	High levels: Anxiety; high blood pressure Low levels: Depression; lethargy	Amphetamines; Anti-depressants (e.g., MAO inhibitors); Drugs to control blood pressure (e.g., beta-blockers)
Serotonin	CNS: � Sleep and emotional arousal � Impulse control � Cognition � Pain processing � Dreaming � Homeostatic processes	Depression, sleeping, eating disorders (if levels low); Obsessive-compulsive disorder (if levels high)	LSD and similar hallucinogenic drugs; SSRIs (e.g., Prozac) for depression;
SECONDARY TRANSMITTERS:
Transmitter	Primary Locations and Actions	Health Issues	Drugs Primarily Associated with Transmitter
Epinephrine	Peripheral: � Sympathetic n.s. effects CNS: � Uncertain	High blood pressure	Used as an emergency treatment for shock or allergic responses; Stimulant drugs
Opioid peptides (Endorphins)	CNS: � Pain control � Mood and memory Also, various effects on temperature, digestion, immune activity, cardiovascular and pulmonary systems.	___	Opiates (e.g., morphine, heroin)

For nice interactive exercises clarifying the brain and nervous system, I recommend the textbook's web page and their Sylvius Interactive Brain Anatomy Dictionary. Also look at other brain links at: Brain web links

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The views and opinions expressed in this page are strictly those of the page author. The contents of this page have not been reviewed or approved by the University of Minnesota.

Summary of transmitters

PRIMARY TRANSMITTERS:

SECONDARY TRANSMITTERS: