Spring 09 Neuroscience Notes 102
The nervous systems are responsible for taking, interpreting, and acting on information
Several divisions of the overall nervous system-Central CNS and Peripheral PNS are the main divisions.
Primarily a geographic division, but a little functional.
Central is mainly 2 divisions- brain and spinal cord. Like a cpu, while peripheral is more like mouse, keyboard, printer, etc. Peripheral is the nerves that take info to and from the brain.

Peripheral split into Somatic SNS vs Autonomic ANS systems. Primary difference is functional
Somatic- nerves connected to muscles that voluntarily control parts of the body. Conscious control.

Autonomic- automatic, responses not under direct control.
Autonomic is divided into Sympathetic vs Parasympathetic. Difference is in the direction of the response.
Sympathetic is the responses that rev one up, get ready for whatever action. Fight or flight arousal response.
Parasympathetic responses get the person back under control, bring the nervous system back down. Becoming calm and control is not just the sympathetic part slowing down; the parasympathetic part gets more active in that time.  Typically, these 2 parts work as antagonists to each other. When one of them gets more active, the other usually decreases.
Sometimes they can both be going, like in a ritual behavior that causes excitement or elation. Meditation, etc. They stimulate the Parasympathetic area enough to cause excitement in the sympathetic area.

CENTRAL NERVOUS SYSTEM

Spinal cord connects brain and PNS. Spinal cord consists of cell bodies and axons that carry messages.
Afferent- carries info toward the brain- sensory function
Efferent- carries info away from brain- motor function

The BRAIN- is the main processing unit in the body. The brain is made of billions of neurons linked together. Neurons are cells that transmit information.  3 main parts-
Dendrites-receive information from other neurons and areas. These messages are typically coming from other neurons. This is almost always true in the brain, but sometimes it's coming from skin and other areas.
Soma or main cell body. As far as psyc goes, the cell body supports the cell and passes info on to the-
Axon carries the cell's message to other neurons and body areas. It has numerous terminal ends that link to a dendrite of another cell. Most axons have a myelin sheath- a fatty substance that covers the axon and helps speed neural impulses. It also protects it, as it insulates the electric currents going through the axons. Some diseases will degrade the myelination in the NS. Like multiple sclerosis- which leads to decreased motor function as it kills the myelin of the spinal cord.
A cell will usually have lots of dendrites and 1 long axon.

A SYNAPSE is where an axon and another cell's dendrite meet. They do not physically touch; the synapse is this gap.

RESTING POTENTIAL-
Sodium ions are concentrated on the outside of the the axon membrane. SON-sodium outside neuron.
Potassium ions are concentrated on the inside. PIN-potassium inside neuron.
Ion channels are closed. And the inside is more negative.

JAN  21st

Chemicals that transmit info are called Neurotransmitters. Stored at the end of an axon. The message gets to the end of the axon, the axon then releases the NTs into the synapse opening. Most of them find receptor sites on the next dendrite. A slot where the molecule fits in perfectly.
This is an adaptable system, since various Nts can be used to transmit different messages. There are about 30 Nts in the brain. Roughly divided into 2 types.
2 types are-
Excitatory type- Starts some sort of action. A neuron is usually at a resting state, where it is not really processing info, but it stays at a baseline firing rate. It fires up when it has to send stuff. The membrane of the neuron becomes more permeable. Starts in one area and a positive charge starts coming in; then it spreads across the neuron. The neuron starts getting a more positive charge. This is called Depolarization.
Inhibitory type- they send messages that inhibits or stops some reaction. In an inhibitory message, the same thing happens but in reverse basically. The membrane gets less permeable and the neuron gets more negative. This is called hyperpolarized. And firing rate decreases from the baseline.
 
Some neurotransmitters-
Serotonin-has got lots of attention lately- associated with processes that regulate emotional states and arousal. Deficiencies are associated with depression. Prozac affects this. Its an SSRI- selective serotonin reuptake inhibitors.
Acetylcholine- important for voluntary muscle control. We know this because to tranq animals, those drugs interrupt and block this NT.  Also poisoned arrows sometimes block this.
Dopamine- has many important functions- for perception, regulated certain thought processes too. When dopamine isnt functioning properly, you get schizos when there is too much. Delusions and hallucinations. If there's too little, you get parkinson's symptoms. Regulates feelings of reward, or accomplishment.
Norepinephrine
Epinephrin
GABA
Endorphins

Jan 23rd

The BRAIN all made of neurons put together in different ways.
How do you divide up the brain? Cut right down the middle into 2 categories-
CORTICAL STRUCTURES- top areas
 -Cerebral Cortex- is newer structures, so we share this structure with fewer animals, the higher ones.
 -proportionally, we have a lot more of this area than we should for body size. This leads to assume that at some point, there was significant evolutionary pressure to evolve this.
 -corpus collosum- a thick band of axons that connects the hemispheres of the CC. Split-brain patients have this thing severed.
 -Limbic System- big ring of structures that sits around the corpus collosum. Separate structures, but they mostly govern emotion and motivation. Emotion is relatively old, evolutionarily. Fear of danger is very important for survival. More basic and primitive than deep thought.
 -Some of these are-
Amygdala-a big ball of nerve cells, appears to be the seat of negative emotions in an organism. Fear, anxiety, caution, anger. We know this cause in cases of damaged amygdala, there are deficits in these emotions and the processing of them. Like- they can identify facial expressions of happiness, etc, but negative faces confuse them.
 - Hippocampus- important for memory function. Seems to be a processing station between short term info processing and the long term storing of that info. Tied to emotion-because the things that give the biggest emotion responses, are the ones which are stored most deeply in memory. So emotion governs what is remembered, and also how and when certain memories are remembered. When strong emotions are invoked, that brain knows that what caused them is important to survival.
 -Hypothalamus- has a few various divisions that handle different functions. But still deal with emotions. Basically urges you do do something and rewards when you do. Feeding- hunger and satiation. Fleeing emotions. Mating and sexual urges. Fighting. Homeostasis.
 -Thalamus- almost perfectly centered in the brain. Its the grand relay station for all incoming sensory information. It decides what info coming in is important, what gets priority.

SUB CORTICAL structures- stuff below that. Is older evolutionary speaking, so lots of other beasts have the same structures. More primitive and fundamental.
 -Brain Stem made up of 3 structures. Sits right atop the spinal cord. The Medulla, Reticular Formation, Pons. Take care of basic metabolic functions, like regulating body temp, goose bumps, arousal-sleeping and waking. Respiration and heart rate.
 -reticular formation- fibers that run down the middle of the brain stem. Connects to many different areas of the Cerebral cortex. Primarily serves an arousal function. If there's a part of the CC that needs to speed up, or slow down, the RF tells it to. If the RF gets damaged, accident, drugs, tumor, you can get a coma. Or other consciousness issues.
 -cerebellum- sits right under the CC. Important in orchestrating and coordinating muscle movements throughout the body. Too much drugs or alchohol affects the cerebellum. And diseases that affect muscle control usually affect this area. The human cerebellum is larger than expected due to body and head size. Probably to control speech; speech uses lots of complicated muscle groups.
 

JAN 26-----quiz on friday jan 30

CEREBRAL CORTEX
Divided into 4 Cortical Lobes by fissures.
Frontal Lobe- The frontal lobe is where most of humans' brain expansion took place. It's huge for our size. Probably the area that is most responsible for what we would consider uniquely human cognitive abilities. Capable of the highest, most advanced forms of thought. Responsible for what we call “Executive” functions. Future planning- the ability to regulate current behavior to attain long term goals. The inhibition of immediate or prepotent responses. Abstract thinking-thoughts that are unrelated to anything going on right now. The case of Phineas Gage- a RR worker supervisor with a stellar reputation for working hard, etc. He got a steel rod through the skull, took out a big chunk of his frontal lobe. He had a tremendous personality change. He became very argumentative and hard to control. Couldn't restrain responses, very aggressive.

JAN 28 start here
A uniquely human skill is speech- an important area for this is Broca's area- Paul Broca- a Dr in late 1800s worked with some patients with speech impediments. They could understand spoken language, but if he asked a question that required a verbal response, they had trouble- severe stuttering and such. A lot of them could still sing, and swear if hurt or surprised. Which indicates that the more emotional responses were governed by a more limbic area. Today we call it Broca's Aphasia-cant produce real language but can understand it. After they died, he autopsied the brains and identified this part as the common factor.
The very back area at the border of the frontal lobe is the Motor Cortex. So called because its important for directing muscle movements throughout the body. It basically has a map of the entire body laid out on the cortex. Different parts of it govern different parts of the body. Certain parts of the body get smaller areas of the MC. The torso, from toes to shoulders, is crammed in together because they mostly just do large or gross movements. Arms, head, face, hands, lips and tongue and throat make much more precise movements so they get a larger area.
But how'd we find this map? When one gets brain surgery, ,they usually are kept conscious. Wilde, is famous for experimenting on people in surgery. He'd stimulate different parts of the brain to see what body part responded.

Parietal Lobe- on top, behind the frontal lobe. It is in the middle, it borders every other lobe. The “brainlocked” nature of the PL is a clue to its function. It takes info from all the other lobes and integrates all that info together. Responsible for Integrated Functions-  Spatial orientation, wayfinding ability, mental manipulation functions.
The PL contains the twin to the motor cortex, across the front of the PL is the Sensory Cortex. It also has a body map laid out on it, similar to that on the motor cortex. It handles incoming sensory info from parts of the body.
Occipital Lobe- the very back part of the brain. Vision and visual perception. Also is active when we dream, in REM sleep. This lobe is rather small, compared to our brain size. We have evolved smarts, more than keen eyesight.
Temporal Lobe- auditory info processing. Hearing, language comprehension, memory, contains Wernicke's area- processes spoken language. Contains primary auditory cortex.