Biology of behavior

This is the biological basis of behavior, the whole unit. It corresponds to Chapter 3 in the book- packed with information. Today we are doing the nervous system. The nervous system is very simple. It is broken down into the central- brain/spinal cord and the peripheral nervous system, which means it's all the nerves on the outside of the spinal cord and brain. It's a very simple brakedown.

Peripheral:



The nervous system

The central nervous system is encased by the meninges tissue structure. That tissue protects the brain and spinal cord from pollution from the body. It's also called the blood-brain barrier. That whole tissue's job is to stand between the blood and fluid systems of the brain and the blood/fluid systems of the body. The brain is more sensitive. The barrier protects transfer from the body's blood vessels to the brain's. Materials would pass through meninges through osmosis- good things pass, bad things don't. This is very important. It keeps things from attacking your brain. You've heard of meningitis, right? It is the swelling of this tissue, which causes fatality in the brain. It's extremely contagious and can be fatal.

The blood-brain barrier manages your response to drugs. Alcohol is able to pass through that barrier. It attacks the cerebellum, which effects things like balance. Ectasy, by itself, does not cross that barrier, so ectasy effects the peripheray nervous system, and thus not as deeply effectant as alcohol. Ectasy+alcohol will mean that alcohol carries it across the barrier, it does not increase your high, but it will help ectasy to attack the brain and make it stop responding as it should. You start having a reaction where your metabolic rate changes, your body has a fever, and part of your body starts to burn up as many fluids in your body as possible. People who have alcohol+ectasy will be very thirsty and will probably die from a stroke. Get a lot of water in them, and they need to be getting fluids quickly or else it will kill them. Ectasy is a big party drug, and the fatalaties are mostly from lack of fluid.

The role of the meninges is to help block stuff. Alcohol tollerance builds up because you've killed so many of the cells that they are not responding. Suppose that you were all neurons, and we put alcohol here, so that means that some of the students would be killed, and there'd be fewer neurons that would be effected.

Your peripheral nervous system connects your CNS to the muscles: smooth muscles (organs) and your body muscles or skeletal striated muscles. Striated means striped. Smooth muscles are things like your heart, your heart is a smooth muscle and therefore involuntary. Your bicep is a voluntary striated striped muscle that you must consciously control in order to move.

How a reflex works

Reflex arc

Reflex = reaction. In this case, a reflex means an entire pathway that starts at say, a sharp pen, and you touch it, and you poke yourself. The normal reaction is to pull away from it. YOu don't have to go touch it and start thinking "Hmm, it's starting to touch the epithelial layer, and now the epidermis, and now my sensory neurons are starting to fire," but actually first you have a skin receptor that recognizes "sharp" and it shoots up your arm and into your spinal cord and into your brain, and is processed in the somatasensory cortex that laughs at sharp and then fires a sequence of move messages down through the spinal cord to the muscles required to move your finger. The reflex is the entire process from when it gets sensed, to being processed and shot back for the response.

It's both voluntary and involuntary. The first half is involuntary, the second half is voluntary. That loop has three basic nerves in it that you need to know


Afferent -> interneuron -> efferent

ANNs

Your nervous system is brilliant. It is adaptive. We would be in a world of hurt if our nerves just communicated like a link in a chain, because communication would stop. It's a mesh or net in our body. If a nerve is used to sending information, and it's normal channel is to go one way, and if there is some nerve damage and the channel is unavailable, the nervous system adapts and uses another node. Nerve damage hurts. You can adapt, and you will build different networks. They are not like a chain- it's a net. The longest nerve in your body goes from your big toe to your brain. That's one nerve, one cell. When we first started studying nerves, we started with giant squids, and they can be up to 50 feet long, if you got one that big. The average is about 9 feet long. The one for your big toe is just a heat sensor.

Nerves, even though are one cell, nerves themselves can be extremely long, because of the part known as the axon, that stretches for communication, like a telephone line. The ANNs are able to have analogous reasoning skills somehow, so it's much more flexible than simply going through a chain of associations.

The peripheral


Your peripheral nervous system, has very basic responses, very basic chain of commands. There's one thing that makes it slightly different. You go from your sensory nerves to your motor neurons for an interneuron and then to an efferent neuron or motor neuron. There are parts of your body that are nodes. The nodes are like minicomputers. Instead of having to send that information all the way to your brain, the node can process real basic stuff. For instance, if you step on something sharp, the information from the foot can be processed in the lower back, and it can be processed, and it can move your foot really quickly, and so there are shortcuts for simple processes. Or, when the doctor tests your knee-jerk response, that's just tapping a node, to see how fast that immediate response is. You can test the speed of your nervous system. They hook you up to an electrical machine that generates an electrical current where-ever they are testing, and sometimes they can't just tap to find muscle density, they have to find if information is really being sent, so they will hook up a shocking electrode, and then an electrode on the other part of the arm, to see if the shock is making it, and it hurts. When they generate the shock, it feels like a very sharp electrical zap, but they test to see how far that goes, and they can clock speed it, and tell you if it goes through where it should go and how long it should take or if you are having the strength of response that you should have, i.e. whether or not you have to crank up the voltage before you replied. Your nerve generates electricity, it's a very simple machine. If you have damage, like in your legs or arms, they can detect the impingement on the nerve and sometimes do some neurosurgery. Nerves do not regenerate. That's as far as we can tell. The stem cell researchers are looking for ways to regenerate nerve cells.

Once an axon is damaged in a nerve, the nerve is useless. Can they do nerve graphs? They try to do this, but nerve tissue is really hard, and they can't do much surgery on it yet, and it has not shown any flexibility outside of the human body. They have been working on brain tissue graphs, and brain tissue can regenerate but really slowly and not directly in the way that we would like it to. Nerves in the CNS are different from the peripheral nervous system neurons.

Autonomic system

- You can influence the autonomic system through thought and emotion, but it requires incredible focus. Meditation and lowering blood pressure through meditation, or people who can change their heart rate, that, that can be done, but it takes massive effort.
Involuntary functions in the autonomic system:
- heart beat
- perspiration
- cell division
- repair
The autonomic system is not being rewired, but they can begin to control it, and it's lots of study time, lots of focus on breathing patterns, etc. Could be used in scifi, maybe. You can stop the heart- consciously. "Hey, I'm going to start my heart." That's like "Jackass" to the extreme. "Dude, stop your heart." And then what happens when it will not start immediately??

Sympathetic

Your sympathetic system has sympathy for how you feel, so that's how it is going to respond. Sympathetic system ramps you up. It usually immediately releases adrenaline. It's a big rush. Stage fright, of any kind, is also an adrenaline response. In stage fright, you get sweaty hands, your muscles get tense, your heart starts to pound, your eyes will dilate, and there's actually a survival reason for that- it sharpens your peripheral vision and so you would want to get more information from your visual field. When you talk about parasympathetic, you're thinking like caveman days, like running from a bear. Our modern life is really weird for our nervous system. For example, caffeine tells your body that you're about to be killed by a large bear, and so that's why caffeine is bad for you- you will burn up your systems. Your liver is required to release all of the glucose it has so that you have a glucose rush into your blood system, and then you start burning the glucose pretty quickly, and if you stay in stress, your energy is going down and the body starts to break down the organ tissues and your muscle tissues after that, in order to make that response work. Caffeine is addicting because you just want more, and then you have a sympathetic response and it could be an emotional response- "I have a hard time getting up in the morning and if I have caffeine in the morning it'll be better."

You start getting into burnout while remaining in sympathetic mode, and parasympathetic has the goal of responding to your environment and bringing you back down to normal so that you would not burn down your system. Sympathetic mode is like rocket mode going at 500 mph all the time. We burn too much when in rocket mode. Sympathetic raises you, parasympathetic brings you back down, always working in the hopes of achieving normal. There's also a backlash response where you have time to repair due to the burning mode. This could be depressing. Then there's something known as the sugar loop where you go all the way up and then all the way down.

Sympathetic system

Eyes dilate. Saliva glands shut down, you get dry mouth, your lungs are filled to more capacity, your liver releases glucose, your stomach shuts down so that blood can be used in the muscles, adrenal glands release adrenaline, you need to pee badly, your body is trying to get rid of any extra weight you might have so that you may run. You're going to let go and then go on.

Parasympathetic system