student submission -- gen psych the nervous system

7/28/2019 Student Submission -- Gen Psych the Nervous System

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Emotion involves the entire nervous

system, of course. But there are two parts

of the nervous system that are especiallysignificant:

limbic system

autonomic nervous system



The limbic system is a complex set of structures that lies on both sides of thethalamus, just under the cerebrum. It includes

the hypothalamus, the hippocampus, theamygdala, and several other nearby areas. Itappears to be primarily responsible for our emotional life, and has a lot to do with the

formation of memories.



In this drawing, you are looking at the brain cut in half, but

with the brain stem intact. The part of the limbic system

shown is that which is along the left side of the thalamus

(hippocampus and amygdala) and just under the front of thethalamus (hypothalamus):



The hypothalamus is a small part of the brain located just below thethalamus on both sides of the third ventricle.

The hypothalamus is one of the busiest parts of the brain, and is mainly

concerned with homeostasis. Homeostasis is the process of returning

something to some “set point.” It works like a thermostat.

The hypothalamus is responsible for regulating your hunger, thirst, responseto pain, levels of pleasure, sexual satisfaction, anger and aggressive behavior,

and more.

It also regulates the functioning of the autonomic nervous system, which in

turn means it regulates things like pulse, blood pressure, breathing, and

arousal in response to emotional circumstances.



The hippocampus consists of two “horns” that curve back from the amygdala. It appears to be veryimportant in converting things that are “in your mind”at the moment (in short-term memory) into things that

you will remember for the long run (long-termmemory). If the hippocampus is damaged, a personcannot build new memories, and lives instead in astrange world where everything they experience justfades away, even while older memories from the time

before the damage are untouched!



The amygdalas are two almond-shaped masses of neurons on either side of the thalamus at the lower endof the hippocampus. When it is stimulated electrically,animals respond with aggression. And if the amygdalais removed, animals get very tame and no longer respond to things that would have caused rage

before. But there is more to it than just anger: Whenremoved, animals also become indifferent to stimulithat would have otherwise have caused fear and even

sexual responses.



The cingulate gyrus is the part of the cerebrum that lies closest to the limbic system, just

above the corpus collosum. It provides a pathway from the thalamus to the hippocampus,seems to be responsible for focusing attention on emotionally significant events, and for

associating memories to smells and to pain.

The ventral tegmental area of the brain stem (just below the thalamus) consists of dopamine

pathways that seem to be responsible for pleasure. People with damage here tend to have

difficulty getting pleasure in life, and often turn to alcohol, drugs, sweets, and gambling.

The basal ganglia (including the caudate nucleus, the putamen, the globus pallidus, and the

substantia nigra) lie over and to the sides of the limbic system, and are tightly connected with

the cortex above them. They are responsible for repetitive behaviors, reward experiences,

and focusing attention. If you are interested in learning more about the basal ganglia,

The prefrontal cortex, which is the part of the frontal lobe which lies in front of the motor

area, is also closely linked to the limbic system. Besides apparently being involved in

thinking about the future, making plans, and taking action, it also appears to be involved in

the same dopamine pathways as the ventral tegmental area, and plays a part in pleasure and

addiction.



The second part of the nervous system to havea particularly powerful part to play in our emotional life is the autonomic nervous

system. The autonomic nervous system iscomposed of two parts, which function primarily in opposition to each other.

sympathetic nervous system

parasympathetic nervous system



Activation of the sympathetic nervous system has the

following effects:

dilates the pupils

opens the eyelids

stimulates the sweat glands

dilates the blood vessels in large muscles

Constricts blood vessels in the rest of the body

increases the heart rate

opens up the bronchial tubes of the lungs

inhibits the secretions in the digestive system



Some of the details of parasympathetic arousalinclude...

pupil constriction

activation of the salivary glands

stimulating the secretions of the stomach

stimulating the activity of the intestines

stimulating secretions in the lungsconstricting the bronchial tubes

decreasing heart rate



The basal ganglia are a collection of nucleifound on both sides of the thalamus, outsideand above the limbic system, but below the

cingulate gyrus and within the temporallobes. Although glutamate is the mostcommon neurotransmitter here as everywherein the brain, the inhibitory neurotransmitter

GABA plays the most important role in the basal ganglia.

Th l f h l i ll d h



The largest group of these nuclei are called the corpus

striatum ("striped body"), made up of

the caudate nucleus ("tail"), the putamen ("shell"),

the globus pallidus ("pale globe"), and the nucleus

accumbens ("leaning"). All of these structures a double ones,one set on each side of the central septum.



The caudate begins just behind the frontal lobe and curves back towards the

occipital lobe. It sends its messages to the frontal lobe (especially the orbital

cortex, just above the eyes), and appears to be responsible for informing us

that something is not right and we should do something about it: Wash your

hands! Lock your door! As these examples are meant to suggest, obsessivecompulsive disorder (OCD) is likely to involve an overactive caudate. On

the other hand, an underactive caudate may be involved in various disorders,

such as ADD, depression, aspects of schizophrenia, and just plain

lethargy. It is also involved in PAP syndrome, a dramatic loss of

motivation only recently discovered.



The putamen lies just under and behind the

front of the caudate. It appears to be

involved in coordinating automatic behaviors

such as riding a bike, driving a car, or

working on an assembly line. Problems with

the putamen may account for the symptoms

of Tourette's syndrome.



The globus pallidus is located just

inside the putamen, with an outer

part and an inner part. It receivesinputs from the caudate and

putamen and provides outputs to the

substantia nigra.



The nucleus accumbens is a nucleus just

below the previous nuclei. It receives signals

from the prefrontal cortex (via the ventral

tegmental area) and sends other signals back there via the globus pallidus. The inputs use

dopamine, and many drugs are known to

greatly increase these messages to the nucleusaccumbens.



Another nucleus of the basal ganglia is the substantia

nigra ("black substance"). Located in the upper

portions of the midbrain, below the thalamus, it gets its

color from neuromelanin, a close relative of the skin

pigment. One part (the pars compacta) uses dopamine

neurons to send signals up to the striatum. The exact

function isn't known, but is believed to

involve reward circuits. Also, Parkinson's

disease is due to the death of dopamine neurons here.



As you can see, quite a few serious problems

are strongly associated with the basalganglia. Some, such as:

Parkinson's disease

Huntington's diseaseCerebral palsy

PAP ( or Athymhormic) syndrome

Schizophrenia

Obsessive Compulsive Disorder (OCD)



The cerebrum -- which is just Latinfor "brain" -- is the newest

(evolutionarily) and largest part of the brain as a whole. It is here thatthings like perception, imagination,

thought, judgment, and decisionoccur.



The surface of the cerebrum -- the cerebral cortex -- is composed

of six thin layers of neurons, which sit on top of a large collection

of white matter pathways. The cortex is heavily convoluted, so

that if you were to spread it out, it would actually take up about 2

1/2 square feet (2500 sq cm). It includes about 10 billion neurons,

with about 50 trillion synapses!

The convolutions have "ridges" which are called gyri, and

"valleys" which are called sulci. Some of the sulci are quite

pronounced and long, and serve as convenient boundaries between four areas of the cerebrum called lobes.

The furthest forward is the frontal lobe (from the Latin word for

forehead). It seems to be particularly important: This lobe is

responsible for voluntary movement and planning and is thoughtto be the most significant lobe for personality and intelligence.



At the back portion of the frontal lobe, along the sulcus that separates itfrom the parietal lobe, is an area called the motor cortex. In studies with

brain surgery patients, stimulating areas of the motor cortex with tinyelectrical probes caused movements. The lowest portions of the motor cortex, closest to the temples, control the muscles of the mouth andface. The portions of the motor cortex near the top of the head control thelegs and feet.

At the side of the head is the temporal lobe (from the Latin word for temple). The special area of the temporal lobe is the auditory cortex. Asthe name says, this area is intimately connected with the ears and

specializes in hearing. It is located near to the temporal lobe's connectionswith the parietal and frontal lobes.

At the back of the head is the occipital lobe. At the very back of theoccipital lobe is the visual cortex, which receives information from theeyes and specializes, of course, in vision.

The areas of the lobes that are not specialized are called associationcortex. Besides connecting the various sensory and motor cortices, this isalso believed to be where our thought processes occur and many of our memories are ultimately stored.



Behind the frontal lobe is

the parietal lobe (from a Latin

word meaning wall). It includes

an area called the somatosensory

cortex, just behind the sulcusseparating this lobe from the

frontal lobe. Again, doctors

stimulating points of this area

found their patients describing

sensations of being touched atvarious parts of their bodies. Just

like the motor cortex, the

somatosensory cortex can be

mapped, with the mouth and face

closest to the temples and the legs

and feet at the top of the head.



If you look at the brain from the previousslide, it becomes immediately obvious that

it is split in two from front to back. There

are, in fact, two hemispheres, almost as if we have two brains in our heads instead of

just one. Of course, these two halves are

intimately linked together with an arch of white matter called the corpus callosum.



The right hemisphere is the

one that relates to the left side

of the body.The right hemisphere has

more to do with things like

spatial orientation, face

recognition, and body

image. It also seems to govern

our ability to appreciate art and

music.

It is the left hemisphere that

relates to the right side of the

body (generally).The left hemisphere usually

has language, and seems to

be primarily responsible for

similar systems such as mathand logic.



If you would flash things on a

projection screen and ask the

patients with epilepsy to either say

what they saw or pick what they

saw with one hand or the other from a box full of things. So, if

he showed a ball on the left side

of the screen and a pencil on the

right, the person would say

"pencil" (using the lefthemisphere's speech centers) but

pick a ball from the box with his

or her left hand (using the right

hemisphere)!



So, speech is predominantly a function of the lefthemisphere. Actually, the right hemisphere does

have a little bit of speech, too: It has a good grasp of

names and curse words! In addition, if you have

brain damage to the left hemisphere early enough inchildhood, the right hemisphere will take over the

speech function. And it seems that there are some

people who have language on the right or even on

both sides.



Another area is Wernicke's area, which

is nearby Broca's area but in the temporal

lobe, right next to the auditory cortex.

This is were we understand the `meaning

of speech, and damage to this area will

leave you with raeceptive aphasia,meaning that you will be unable to

understand what is being said to you.

Occasionally, someone has damage to the

connections between Broca's and

Wernicke's areas. This leads

to conduction aphasia. Someone with

this problem can understand speech just

fine, and can produce it as well. They justcan't repeat something they just heard!

Another important area is the angular

gyrus, just above and behind Wernicke's

area. It serves as the connection between

the language centers and the visual

cortex. If this area is damaged, the person

will suffer from alexia (inability to read)

and agraphia (inability to write).

One of the earliest things discovered about

the brain were the speech centers. One is

called Broca's area, It is located at the

bottom of the left frontal lobe. A patient

who had damage to this area lost hisability to speak, which is

called expressive aphasia.

A f f th f t l t



Starting from the central sulcus and

working forward, we first have

the motor cortex, which sends its

signals down to the body to control

the skeletal muscles.

Just in front of the motor cortex there

is the premotor cortex, which is

where we compose and rehearse

movements before we engage in

them. Broca's area for speech

production is part of the premotor cortex.

And then we have the prefrontal

cortex, where some of the most

interesting things occur. Some say

that will power, our sense of reality,

and our sense of our own personalityreside there.

A few areas of the prefrontal cortexare at least partiallyunderstood. The dorsolateral area(high and to the sides) appears toallow us to hold ideas in awareness,focus on them, and even manipulate

them.The ventromedial area (low andclose to the midline) seems to beinvolved in emotional experience and provides us with the feeling thatthings make sense and have meaning.

The orbital area of the prefrontalcortex (just above the eyeballs) tellsus when something is wrong andrequires serious attention. It also hasthe ability to inhibit behaviors that areinappropriate, such as those that areharmful to us or are sociallyunacceptable. This includes the

ability to counteract the signals for aggression from the amygdala in thelimbic system.



Starting from the central sulcus and working forward, we first have the motor cortex, which sends

its signals down to the body to control the skeletal muscles.Just in front of the motor cortex there is the premotor cortex, which is where we compose andrehearse movements before we engage in them. Broca's area for speech production is part of the

premotor cortex.

And then we have the prefrontal cortex, where some of the most interesting things occur. Somesay that will power, our sense of reality, and our sense of our own personality reside there.

A few areas of the prefrontal cortex are at least partially understood. The dorsolateral area (highand to the sides) appears to allow us to hold ideas in awareness, focus on them, and even manipulate

them.The ventromedial area (low and close to the midline) seems to be involved in emotional experienceand provides us with the feeling that things make sense and have meaning. Low levels of activityhere are associated with depression: Nothing makes any sense. High levels, on the other hand, areassociated with mania: Every little thing is full of importance!

The orbital area of the prefrontal cortex (just above the eyeballs) tells us when something is wrongand requires serious attention. It also has the ability to inhibit behaviors that are inappropriate, suchas those that are harmful to us or are socially unacceptable. This includes the ability to counteract

the signals for aggression from the amygdala in the limbic system. It is believed that many violentcriminals have had damage to this area of the brain.



This lobe sits at the two sides of the head, under the temples. The upper partof the temporal lobe, along the Sylvian fissure that separates it from the

frontal lobe, is the primary auditory cortex, which receives input from

cochlea. The areas around it are devoted to interpreting sounds, and one of

these in particular (Wernicke's area, toward the boundary with the parietal

lobe in the left hemisphere) is known to be devoted to the understanding of

language.

Another area is called the fusiform gyrus, which sits low in the temporal

lobe near the occipital lobe. In the left hemisphere, it is responsible for word

and number recognition. In the right hemisphere, it is responsible for the

crucial human ability to recognize faces. Problems here leave one with a

disorder called prosopagnosia ("face blindness"), which makes social life

very difficult.



The furthest forward area of the parietal lobe,along the central gyrus nearest the frontal lobe, isthe somatosensory area, which collects signalscoming up from the body. Just behind that is the

somatosensory association area, which further analyzes these bodily sensations. Specific areasspecialize in locating and orienting us in three-dimensional space, and focusing on things in the

outside world.



The occipital lobe is the smallest of the lobes and sits at the very back of the head. It has no clear borders and is differentiated primarily by function,i.e. vision. The various parts of the occipital lobe are labeled with a V (for visual) followed by a number.

Theprimary visual cortex at the very back of the occipital lobe islabeled V1, and receives input from the optic tract. It has a clear map of

visual information that corresponds to the areas of the retina. The center of vision is greatly magnified. The individual neurons of V1 are extremelysensitive to very particular changes in input from the eyes.

If there is a lesion somewhere in V1, there will be a "hole" in your visioncalled a scotoma. Oddly, some of the information from that "hole" seemsto still be available, so that some people with scotomas can still react to

stimuli there even though they don't consciously perceive them! This iscalled blindsight.



The cingulate gyrus sits below the rest of the cerebralcortex, up against the corpus callosum and partiallycovering lower areas such as the basal ganglia, thelimbic system, and the thalamus. Many people see it asthe fifth lobe - others see it as part of the lobes above it,

particularly the frontal lobe. It is so intimatelyconnected with the limbic system that it is sometimescalled the limbic gyrus. One of its major jobs is to keepyour attention focused. When it isn't functioning

properly, as seems to happen in schizophrenia, you areunable to distinguish real voices from imaginary ones.

student submission -- gen psych the nervous system

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