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An ongoing conversation on brain and behavior, associated with Biology 202, spring, 2000, at Bryn Mawr College. Student responses to weekly lecture/discussions and topics.


TOPIC 8:

Corollary discharge ... not just a motor function. And negative feedback loops with variable set points? Our discussion of the motor side of the nervous system is beginning to suggest that there are lots of different parts of the nervous system, each getting input from a subset of other parts and each having its own "purposes", which may or may not be the same as those of the "I-function". Is this a useful way to think about behavior? Generalizations? Concerns/criticisms? New questions?

Name: amse
Username: amseh@yahoo.com
Subject: sorry - i'm late
Date: Fri Mar 24 00:04:05 EST 2000
Comments:
wow! so many interesting comments this week. i see i have missed much. mridula's comments about emotional templates are ones i have often wondered about myself. the earlier comments from this past week are of real interest to me (as they seemed to be to most of us). since i feel that the topic of CPG's and word association may have been thoroughly covered for the week, i'd like to discuss the results of seemingly "random" word associations and the role they play in social interactions. when i was younger, my parents were work-aholics that never really spoke with me. i was supposed ot be so quiet around them when they were home, that when i spoke in school, i made whatever associations i wanted and did not realize that my word associations in school were not "normal." i was the "scary" girl in grade and middle school. my free associations bought me a one way ticket to intensive therapy where i had to painstakingly learn how to make appropriate associations. by appropriate, i mean that i couldn't say whatever was on my mind, and my thoughts had to pertain to the event, not whatever i was thinking about (which in grade school was usually peter pan). when did everyone else learn to make associations that are "normal?" the earlier comments discussed lack of sleep and an active attempt at freeing up the CPG pathways to make free word combos. i have to work at making the associations you all make regularly. In denmark, though, my htought processes fit in. our culture promotes certain modes of thinking that limit the kinds of connections we make. why? what effect, if any, do you all think this has on people, relations, etc.? for myself, i hope things change in the future. i don't think such outlined thought connections are things i would wnat to teach my children. everyone would be so much more interesting if their interactions weren't so limited by the "norm" and we could all see what really goes on in one anothers' heads. sure, there would be alot of chaos, but we'd probably never be bored.


Name: Vandana
Username: vandnam@yahoo.com
Subject: negative feedback
Date: Fri Mar 24 11:46:48 EST 2000
Comments:
i agree with amse that these past few discussions in class have really opened up my eyes, or should i say my brain, to what seemingly usual everyday events really are. some examples that we did not touch upon in class yet, that would fit into the category of (-) feedback loops are, hunger (when you feel hungry, you eat and then you feel full, so you stop eating), exercise (you exercise, then get tired, so you rest and feel less tired) and sometimes even smelling (when someone bakes cookies, it tends to smell good but after after awhile, you get used to the smell and it does not smell as strong as before. maybe this is a type of negative feedback loop.)

i have also found that in other cultures, people are more accepting of acts that are different from the norm. for example, when i visit people in india, i tend to be able to open up more easily and feel at home with them. maybe it's because i feel like i am more used to them and they are more open about things. also, when i visit my aunt in france, i have noticed that people on the street greet you differently. i guess this is similar to what someone was discussing in class on March 16 about different ways that she greeted and was greeted in France. in some ways, i think it is pretty normal to feel out of the norm (if that makes sense?)


Name: Maria
Username: mvasilia@brynmawr.edu
Subject: Negative-Feedback Loops
Date: Sun Mar 26 15:10:45 EST 2000
Comments:
Surfing the web this weekend, in preparation for our next web paper, I came across some interesting topics about negative feedback loops and ideas on reflexes and the idea of fevers and how what the I-function wants to do can be in conflict with what we actually want to do. This idea of another system in control brings to my attention the idea of sneezing. Sneezing: a behavior with a purpose.

So what really is sneezing? Is it something that happens when we smell pepper, or does it happen when we have allergies? Sneezing is a sudden and violent, in some cases that Iíve experienced, rush of air (among other things) out through the nose and mouth. A person usually has no control over sneezing. Sometimes I think I can control sneezing. For example if Iím at a lecturer and I donít want to make to much noise or be a distraction I try to control a sneeze. This usually works the first time, but then I find that the sneeze sneaks up on me and comes out anyway when Iím not prepared. So there goes that method. Just like with fever, doing something to benefit our bodies, sneezing happens because our body takes this action to get rid of irritating or harmful objects in the nose. Sensitive nerve endings that line the nose react to these objects by causing the sneeze. Sneezing occurs when we have hay fever. Plant pollens lodge in the nose of people who have allergies and cause then to sneeze. But did you guys know that sneezing also occurs with bright sunlight? This happens because the eye nerves are closely connected with nerve endings in the nose hence causing the sneeze. Also have you ever wondered why we donít sneeze when we are asleep? Hay fever and allergies donít go away at night, so why donít people wake up from their sleep and sneeze? Well, in my web surfing I found out that sneezing is the protective reflex in response to stimuli from your nasal mucosa. The stimulus has to reach the brainstem center before the brain's neurons trigger a response from the neurotransmitters. When we sleep the activity of many of the brain's systems declines and the reflex arc is not completed because the neurotransmitters are not activated. So sneezing doesn't occur despite the stimulus. But if the stimuli was very intense, just like if someone burned you or pinched you really hard when you are asleep then of course you could wake up, and immediately there could be a withdraw from the particular part disturbed, i.e. leg.

So I think sneezing can be categorized as a negative feedback loop. And just like fevers it a behavior that is benefiting the body.


Name: Ann Mitchell
Username: amitchel@haverford.edu
Subject: emotional setpoints
Date: Sun Mar 26 16:13:59 EST 2000
Comments:
The first thing I thought of as an example of "set points" were moods or emotions. Maybe this is not the most obvious example if we are trying to consider ďset pointĒ systems that are independent of I-functions, but nonetheless I think one could make an arguments that emotions are a good example. For instance, someone has a particular set point for the chemical balance in their body that contributes to their particular affective style. So, say an event occurs like exercise that could raise the set point. Letís say that the effect of this raise is increased positive affect, so that the person has the subjective experience of feeling better after they ran than before they ran. This would then make it very difficult for a person to have an experience that was high enough in positive affect for them to feel the subjective experience of being happy because their set point is so high. (Just like the person with a fever who shivers because their set point for ďbeing warmĒ is so high that other temperatures automatically seem cold to the body in comparison.)

Perhaps I am not understanding the negative feedback system, and perhaps this is not a good example. Yet, this example becomes more complicated when we begin to think about set points that are changed by exogenous as opposed to endogenous substances, or the environment. (the endorphins released by running are endogenous, correct?) For instance, things like a piece of news like getting a new job, or being rejected from a job. Or something nice or bad people say about us-entirely environmental influences. Another example of an exogenous substance could be something like prozac or any other drug(even though all of these interact with endogenous substances).

This issue becomes more complex when we begin to think of the I function as an exogenous substance/environmental influence and how much I function contributes and can contribute to set point. At first, I thought that this argument would pose problems for people who believe in things like the power of prayer or cognitive healing of any kind. But, as this model goes, if praying or using a different cognitive style changes a set point, then their really isnít a problem. One would have to be able to show that praying and cognitive therapy change levels of endogenous chemicals, which is a large linking step that I think some of the web papers have already addressed. If evidence from this linking step seems to suggest that everyday things like compliments or getting rejected for a job can effect endogenous chemicals, one might be able to then argue that the I function really has more power over our behavior than we are willing to admit. So, while this function may seem very independent for certain examples like hunger and temperature, it seems theoretically possible that there are also examples where the I function can have a significant impact on set point.

One problem with the previous paragraph that I noticed after reading through this is that I presented that theory under the assumption that your I-function and your body are separate from each other-which is kind of funny because the presentation of brain and behavior in this class is by no means dualist. So, it seems that I categorize the I function as somewhere in-between a completely separate environmental influence and a completely automatic biological function. I think it is possible to have both the environment and an I- function interacting to change a set point at the same time.


Name: Richard
Username: rcruz@haverford.edu
Subject: Feeding Back
Date: Sun Mar 26 18:32:33 EST 2000
Comments:
Here's another system that is often referred to as a "reflex." Usually when you touch something hot, you immediately pull your hand away, or drop it. However, if its your dinner plate, a big serving plate, or something else really important you will think twice before you drop everything crashing to the floor. There's got to be an inhibitory circuit in there somewhere.

Related to this is the work that Wendy Sternberg and her seniors (hi MW) does on stress related analgesia. If you are under stress, not only do you not report feeling the pain, it also takes longer for you to flinch to what is usually a painful input.


Name: Mridula Shrestha
Username: mshresth@brynmawr.edu
Subject: re: setpoints
Date: Sun Mar 26 20:07:36 EST 2000
Comments:
I missed last thursday's class, so forgive me if my comments are redundant with regards to your discussion. Ann's comments about setpoints make sense in a very important sense: drugs. Don't most drugs have varying effects on different people? Don't the drugs that have calming effects on people with ADHD actually make most "normal" people more active? And on a perhaps easier-to-relate-to level, we as college students see a lot of differing effects of alcohol--I mean, we see all kinds of drunk people--happy, mellow, angry, etc. and they're all drinking the same cheap beer, so we can't just blame it on alcohol quality:) Of course I'm sure doses, etc. make a difference, but it also seems to imply that something about our internal states somehow affects, in a very major way, the way our body reacts to even "exogenous" substances. We can probably call those somethings our setpoints.

These setpoints, ironically, are probably not "set"--i.e., they are subject to change. But this is hardly surprising, as it makes intuitive sense that our internal states are also subject to change. I figure they must be relatively stable within a certain range at least, though. But how wide is this range, and how does that affect how our body reacts to drugs?


Name: Melissa
Username: mwachter@haverford.edu
Subject: drug withdrawal and other stuff
Date: Sun Mar 26 22:46:53 EST 2000
Comments:
In reading over the postings, I have several comments and hopefully a new piece to add. I was very interested in Ann's discussion about the role of exogenous and endogenous chemicals in altering mood related set points and how this can affect mood. First I want to make a clarification about one of the examples Ann gave. Ann-correct me if I am not understanding you, but with the exercise example, wouldn't it follow that it would be that exercising releases endorphins which have the effect of LOWERING the set point needed in order to have positive affect. That way, as you said, someone would come back from a run to find herself in a better mood than before she went because the same quantity of dispositional positive affect would now put her over the threshold for her normally neutral affect (since the set point/threshold was lowered). Does that make sense? Here's where I am going- I definitely find that in my own life if I get into the habit of running for a couple of weeks fairly consistently I first sense an increasing level of happiness, then it kind of levels off a little bit, but then if I stop running, I find myself in a bad mood. So here is my, admittedly oversimplified hypothesis: when I begin running, my set point for neutral emotion is lowered (lets say it started at 5, now its at 3) so lets say that I had been just at the standard set-point for neutral emotion (5)...without changing anything that would affect my emotion, i am now 2 contentedness points above the new set point of 3 so I experience EXTREME HAPPINESS...

So now here is my new part...the addition of some form of a compensatory responce...by this I mean that perhaps now the body is willing to be at 4 since with the lowered set point, that is now above the neutral emotion threshold (and thus gives contentment)...well that's all well and good except that when I stop running, then the set point is shifted back to 5 and now a 4 is BELOW


Name: anonymous
Username:
Subject: Weekly Essay #8
Date: Sun Mar 26 23:10:13 EST 2000
Comments:
I think Vandana brought up an interesting topic about how when you first smell something, it's strong but then once you get used to the smell, it doesn't smell as strong anymore. Why is that? I mean, I have this clock in my bedroom at my parents' house which makes a very loud ticking sound but I've had it since I was in like 7th grade so I've grown so accustomed to the sound that I don't hear it anymore. I literally have to concentrate on it to hear it whereas it drives my friends crazy. I mean, I must be "hearing" in the sense that the sound waves are reaching my ear but why and how does my brain choose to block it out of my consciousness? How does the brain know to inhibit the AP's so that I'm not constantly aware of the ticking? This is a very interesting topic that I'd like to learn more about...
Name: Soo Yi
Username: syi@brynmawr.edu
Subject: not too bright
Date: Sun Mar 26 23:11:17 EST 2000
Comments:
That above post was by me. Yeah, it's late...well, for me anyway.
Name: hiro
Username: htakahas@haverford.edu
Subject: sleep paralysis and hallucination
Date: Mon Mar 27 00:06:23 EST 2000
Comments:
I have a question about phantom limb. A person with a missing limb can feel the position of the missing limb. He often reports discomfort or pain. I now understand that the pain results from the mismatch of sensory input and internal expectation, but in which part of his body does he claim the pain is? In his missing limb? How can he feel the pain, not the position, of the missing limb if he does not have sensory input from the limb?

The mismatch of sensory input and internal expectations made me think of hallucinations triggered by sleep paralysis. Some people have hallucinations during sleep paralysis, but no one knows why hallucinations start. Could this be the result of mismatch, too? During this event, the brain, I-function, sends a signal to move the body. The other part of the brain also receives corollary discharge signal and senses what the body is told to do. However, for the body is under total inhibition and cannot move. Hence, the brain does not receive the sensory input from the muscles, which tells the brain what they are doing. As a result, the mismatch between the internal expectations and sensory input occurs, and maybe, this somehow causes a change in membrane potential of optic neurons, and thus hallucinations.


Name: christina
Username: cpili@haverford.edu
Subject: web paper #2 help
Date: Mon Mar 27 01:05:25 EST 2000
Comments:
Sorry to break the flow of the conversation and chat, but this is the only topic that plagues my brain. Ok, so I decided to take Professor Grobstein's suggestion in looking up motor imagery. I was at loss for a topic and as we all know, any topic is more interesting if it directly relates to our lives.

This topic arose when I wondered why I can have successful dance rehearsals in my head and then physically perform the number. Anyhow, when I searched the web for my topic, I found an overwhelming amount of material. So, I'm asking for any kind of feedback from my last paper so that I could successfully create a focused paper. Any tips on narrowing and weeding out the useful material from the junk?

With regards to my last paper, I'd really appreciate it if anyone had any constructive criticism? I had trouble zooming in on just one aspect and I'm sure that came across to any of my readers. Do you think it would help if I related motor imagery directly to dance or should I keep this topic more as an overview and merely refer to different examples on how motor imagery is used. Basically, I'm just intimidated by all of the possible material out. Any suggestions on how I can improve my writing style, content, format would be greatly appreciated.


Name: hillary bobys
Username: hbobys@haverford.edu
Subject:
Date: Mon Mar 27 01:33:33 EST 2000
Comments:
ok, i am very confused about the last example given in class on thursday. can any one explain this concept of negative feedback in dieting to me? i didn't quite follow prof. grobstein's explaination of why we are able to keep weight off when we think about it and regain weight when we stop concentrating? how does this work with the negative feedback?

as someone mentioned earlier, alcohol is an interesting example to apply to this idea of a thermostat. alcohol affects things like body temperature and must affix a new set point in this domain. also, the sickness resulting from too much alcohol is a means to regain homeostsis (is this the right word?) in the body. in addition, we must think about tolerance from this perspective as well. tolerance for drugs increases with use, setting new set points. how then does withdrawal play into this concept?


Name: Elissa Braitman
Username: ebraitma@brynmawr.edu
Subject: recalling sights and smells
Date: Mon Mar 27 13:24:00 EST 2000
Comments:
This doesn't really have anything to do with what we're talking about but it's something that I've been wondering about for a while.

This weekend I went to the PMA's exhibit on Rome with some visiting friends I met while studying in Rome in fall 1998. Looking at paintings of places I had visited many times, I often had the sense that I was back there for a second. My friends experienced the same thing. Even though it has been over a year since we last saw these places, for a brief period of time, we were transported back there. It felt like we'd never left. This same sort of thing happens with smells. Sometimes if look at a picture of a place I haven't been to in a while, I can smell it for a few seconds. The image of the place is associated with a particular smell and that is part of the memory, I guess. It's strange but also comforting (usually it happens with places I like or good smells that I miss).

So, I was just wondering if anyone has an explanation for this phenomenon. Trying to relate this back to this week's discussion, if people can get used to a smell, sound, feeling that is present for a long time and forget that it's there (as Vandana said), I suppose that the reverse might occur in the same way. Being so used to something that the feeling, smell, and (maybe) sounds associated with it can be recalled anytime, anywhere (with the right sort of stimulus).


Name: Andrew
Username: aholland@haverford.edu
Subject: set points
Date: Mon Mar 27 14:05:57 EST 2000
Comments:
Someone questioned earlier if it was possible that the set point could be too high and thus be unreachable. I also had a question along these lines. First, what exactly is setting these points? Also, is it possible that to maintain the "happiness" higher set points are made? If higher and higher set points were made, wouldn't it eventually be impossible to reach them? Take running for an example, does a runner need to run more and more to maintain the happiness, or is there a place where, if they keep the running at a constant amount, the person will maintain their happiness? Maybe I do not totally understand set points. Are they made from the results of a negative feedback loop?
Name: Sarah Kim (sskim)
Username: sskim@brynmawr.edu
Subject: CPG and CD
Date: Mon Mar 27 16:32:46 EST 2000
Comments:
Reading over the posted comments, I was also interested in what Vandana said about how when you first smell something, the smell is strong, but then becomes not as strong. Isn't this the same principle as 'practice makes perfect?' For example, when we are learning to play a piece on the piano, initially playing the notes and the right keys at the same time require thought and practice. But after awhile, the playing becomes automatic and requires no thought. This is due to continually using the specific CPG's and corollary discharges in your brain to generate playing the piano -- continually using a certain pathway in your brain will enable you to become more accurate and 'perfect' in generating the output. Now back to the question. When we smell a new smell, the brain has never used that pathway before in order for you to smell that smell. But after a while, continued use of that smell enables the brain to use that pathway more and thus enables you to smell without thinking, or smell without noticing. Even if we don't use a certain used pathway in our brain for awhile, it can still be recalled easily. This exaplains Elissa's phenomenon at the PMA. I don't think I understand negative feedback either.
Name: Laurel Edmundson
Username: ledmunds@brynmawr.edu
Subject: hot tamale
Date: Mon Mar 27 19:05:36 EST 2000
Comments:
Iím surprised no one brought up the hot coal scenarioÖam I the only one who was bothered by that? How can it really be possible not to experience pain when traversing burning embers? I understand that the brain is a powerful tool, but this seems to be pushing it. Iíd like to know more about how your thinking can negate pain. I donít think I want to develop a web paper to such an unusual example, but I am interested. Does anyone have any ideas or concrete information?

This issue of setpoints is not one I know much about, but that I find intriguing all the same. I am ok with the setpoints being changed when a) an animal goes into hibernation and b) when a person has a feveróthese make sense. But I too missed the boat on the dieting example. Thatís also an instance in which the way you think about it affects your success?

About runnersí setpoints...I believe that during serious training, runners usually do have to run longer and/or harder to experience the mystical ďrunnersí highĒ. But I think for us average Joes and Josephinas that since our physical progress is gradual, we can get the same energized feeling from relatively constant distances/durations. Personally, I almost always have the same good, refreshed feeling after a runÖitís the before-mood that varies widely.


Name: Cameron
Username: cbraswel@brynmawr.edu
Subject: game, SETPOINT, match
Date: Mon Mar 27 20:05:49 EST 2000
Comments:
This evening I think I shall jump on the setpoint bandwagon. I too have been thinking about the effects of alcohol and tolerance ( I suppose it is a hot topic) Some people do seem to observe that the increase in frequency of drinking builds such a tolerance to the drug and they can drink more without feeling all the effects such as numbing, silliness, etc that were once experienced on one drink. Does a tolarance for this particular drug result from the brain moving the setpoint of how much alcohol it takes to start shutting down nerve systems or is the alcohol just simply killing the nerve cells that regulate the setpoint function a little at a time allowing for more to enter the system before shutdown occurs. And even though tolerance builds in the brain (definetely a negative feedback loop, the more you drink the higher the tolerance becomes)it does not build in the body and the same amount of alcohol can do massive damage on all systems regardless of how high your "tolerance" is. This has implications that the same setpoints in the brain are not the same for those controling body functions and organs.

Along these notes, the setpoint for sleep deprivation is an extremely relevant topic for college students. I do believe that the setpoint for how much sleep one needs to function in a societal or academic setting can be moved at least temporarily. If one gets used to staying up late and getting up early and learns to live on 5 hours of sleep or 4 hours of sleep a night that person has a very different functioning setpoint than someone who needs 8 hours of sleep to even get out of bed the next day. Obviously this set point relates to how much time the body needs to replinish and restore itself and grow which is why really young and really old people need more sleep to function in the same world. But if you normalize the sample and just look at college students there is much variety in what septpoints of sleep levels make people tick. And they are changeable. If over the summer one gets used to sleeping 10 hours a night a rude awakening comes in the fall when you fall back into a routine of 6 hours and it takes a while for your mind and body to readjust to a changing setpoint. Once a routine is back in place those same people find it perfectly normal to only get 6 hours a night and can perform at daily tasks just as well as if they had had 10 hours. I do believe this setpoint, for the body's sake, has its limits becuase I as one of those people can carry on like that for only so long until I am just exhausted and have to catch up somehow (hence I sleep most of the first part of every break)


Name: Emily Hollister
Username: ehollist@brynmawr.edu
Subject: Re: Soo Yi's post
Date: Mon Mar 27 21:36:31 EST 2000
Comments:
The experience of gradually being able to tune out a loud, repetitive sound is used in some therapies for autistic individuals. One of the symptoms of autism is extremely sensitive sensory perception. For example, loud noises are annoying to most people, but are excruciating for people with autism because they are unable to tune it out and it become magnified and they can only focus on the sound to the exclusion of all other sensory input. Part of the therapy is to expose patients to sounds for periods of time, with gradual increases in intensity. Eventually, people can learn to tune out the sound to a tolerable level. I live right next to the train tracks and a block from the fire station. If anyone has ever been near the fire station when the whistle (an old air raid siren) goes off, they know the aggravation that it can cause. After about a week or so, though, I hardly paused when it would go off. The fact that it was sounding barely registered in my brain. There would be a slight pause, especially if I was talking to someone, and then I could barely remember that it even happened. It doesn't wake me, either.
Name: anonymous
Username:
Subject:
Date: Mon Mar 27 21:37:20 EST 2000
Comments:

Name: Susan
Username: sslee@brynmawr.edu
Subject: deja vu
Date: Mon Mar 27 21:43:44 EST 2000
Comments:
I wonder if what Elisa and her friends experienced at the art museum was anything like deja vu. My experiences with deja vu have been that during an event such as a conversation I get the erie feeling that this exact sequence of events has already occurred. Yet I know that it is nearly impossible for everything to have happened in the exact same way. Its weird because you are taking part in a situation yet at the same time you are able to remove yourself from the situation. I have read literature before that suggests there might be connections between visual triggers and events. For instance one might recognize a pattern on a piece of clothing from a different interaction and associate it with the current event, thinking that the event has previously occurred.

This theory brings up some interesting questions that pertain to our discussions in class. Does deja vu have anything to do with CPGs? Do some activities activate CPGs that have been established previously, which in fact require a new CPG?


Name: Sangeeta
Username: siyer@brynmawr.edu
Subject: Setpoint Dilemma
Date: Mon Mar 27 23:03:52 EST 2000
Comments:
As I read Cameron's posting on setpoint, I began thinking of a recent physiology lab that I had to do for my introduction to biology class. In this exercise, my group and I tested the effect of different variables like temperature, caffeine and distraction upon touch response. Now, when we were talking about setpoint, I began to think of my discussion of the temperature data. Our group placed a cold ice pack over our arms for about five minutes and then tested touch response latencies. What we found was that our responses after icing did not vary greatly from our control data (no icing). Why? Well, we had hypothesized that the greater our body temperature varied from the set point body temperature, we would see greater differences in results. Our metabolisms are very dynamic, and it takes something really strong to push them over the edge. When we were talking about alcohol, I was thinking whether small drinks now and then increase set point tolerance or alot of drinks at one time for a period of time. (What an interesting experiment!). Also, wouldn't a lapse in time reset the body's original set point tolerance? This can apply to not only alcohol but also to sleep. I know that I will get three hours of sleep for like a week and then over the weekend, I will suddenly sleep until noon. My body is compensating, so it's not as though it has adapted to three hours of sleep a night.

Like Sarah, I'm somewhat confused by negative feedback so a quick little summary would be awesome. And like Christina, anyone who can offer me any suggestions on how to perfect my web paper or what questions you ask yourself in working through the paper, would be greatly appreciated.


Name: shigeyuki ito
Username: sito@haverford.edu
Subject: set point
Date: Tue Mar 28 00:00:53 EST 2000
Comments:
On thursday after class, I thought I understood about the setpoint and the dieting example but after I thought of it, and also read one of the comments, I realized.. yes I too am confused. If it isn't hard to lose weight if we "think" about it then how come so many people have trouble doing it?? and what do you mean by "think"?? And if we don't think why does it bounce back?? also perhaps this is a little off the topic but don't people actually gain weight if they rebound? also if raising the termperature of our body is something we control, then how come there comes a time when it gets out of hand?? What other set points do we have??
Name: Anna
Username: aarnaudo@brynmawr.edu
Subject: More on Setpoints
Date: Tue Mar 28 00:49:55 EST 2000
Comments:
Wow there is a lot of chat about set points. I find Cameron's post particularly interesting about sleep. Lets say that we have a set point of sleep that tells us how much sleep is optimal. Then you get above the set point. I find that the more sleep I get the more tired I am. Is that a case of the set point continually increasing? Or am I trying to compensate? Or is that unrelated? As for the diet set point- the way I understood it is that the body likes to maintain a certain weight and we can change that weight by monitoring what we eat. If we go back to our normal diet, our body will go back to its normal set point and we will gain back all the weight we lost. Perhaps I am off but that is how I understood it.

I agree with Laurel- the walking on hot coal example is quit disturbing!! It is also quit amazing- I always wondered how they did that. I was also thinking of how that could relate to the power of positive thinking paper. Is it possible that people can will pain away during surgeries (supposedly) due to the fact that they are actually equalizing the amount of pain they expect with the amount of pain that is actually be sensed?


Name: Laura
Username: lchivers
Subject: setpoints and phantom limb
Date: Tue Mar 28 01:13:13 EST 2000
Comments:
I too am intrigued by the idea of variable set poits. I like Cameron's idea about sleep. During the school year, I usually only sleep 5 hours and am fine with that. But during the summer, getting up after only 8 hours seems impossible. It would seem that the amount of sleep that I need changes depending on what I need to get done. I have noticed also that even after one week of break and sleeping a little longer I have trouble sleeping only 6 hours for a few days. It seem sthat these set-points can be changed rather quickly.

I too was thinking about setpoints in relation to drugs. At the methadone clinic whenere I externed over winter break, there seemed to be a ot of people who felt that people who used drugs for a long tme may have changed their brains in some way that now required them to have more opiate-like substances in their brains in order to function properly. PErhaps, as was suggested, drug use causes tolerance to develop due to a change in setpoints. Perhaps though, in the case of herion addicts, the setpoint that has been pushed up is unable to return to its original level and the brain doesn't function the way it should. I have no idea if this is true, but it is an interesting thought. Maybe I'll look nto it for a web paper.

Finally, last week's classes have moved me further in the direction that brain is behavior. I am continualloy suprised at the "reality" that is created by our brains, as in the case of the phantom limb. If we can feel limbs that aren't even there and can even describe the position it is in, how can we be sure that anything qwe have felt, seen, heard, expereinced was "real" and not just the reality of our brains?


Name: Yun-Wen Shaw
Username: yshaw@brynmawr.edu
Subject: set points again
Date: Tue Mar 28 04:07:38 EST 2000
Comments:
Personally, I donít know about the idea of being able to lose weight easier if you think harder about it. To me, that doesnít sound realistic. Is it similar to the choo-choo train that thought he could? I donít think that it is that simple to readjust your set point, simply by mentally conceiving it because that thought occurs on such a conscious level that it does seem as if it should have any subconscious effect. Also because something such as dieting seems to consist of so many other factors that come into play. For example, the mental preparation that we discussed was necessary to walk on coals seems so unbelievable. It seems that the concept of set points that we have learned about so far is not even close to the entire story. There has to be so much more to it Ė it cannot possibly be a concept standing alone. The last example that we went over in class was that squirrels have a lower body temperature set point in order to survive the cold outdoor winters. In introductory biology, we were taught that this change in body temperature and weather tolerance is based on the hypothalamus in the brain, which is the control center for body temperature regulation. Unfortunately I donít remember how the hypothalamus goes about doing this. But my point, or rather question is, that just saying that the set point is variable seems altogether too general. Does the same part of the brain that controls body temperature also regulate body weight and hunger? How? Maybe we will continue discussion on it this week.
Name: anonymous
Username:
Subject: questions
Date: Tue Mar 28 07:24:53 EST 2000
Comments:

Name: rebecca
Username: rjones@brynmawr.edu
Subject:
Date: Tue Mar 28 07:38:30 EST 2000
Comments:
I think I understand the body weight question. As far a I know the reason you lose weight when you are thinking about it is an I-function task, you are regulating the amount of food that enters your body. When you eat less food you lose weight but the body 'wants' to be at the set point of body weight and will change teh metabolism set point to a lower value to try to acomodate the lower intake. Thus if you want to continue to lose weight you must eat even less or find a way to increase the metablism such as exercise or stimulants. The reason you gain the weight back or even get a higher weight than ever before, when you stop concentrating on it is becuase the metabolism set point remains low for a while after you return to eating more food. The combination of a slow metabolism and a lot of food causes weight gain.

As for the smell issue I always thought that was not a brain related thing. I think that what happens is that have chemoreceptors in the nose and when there is a lot of a chemical in the air (smell) for a while the receptors for that particular odor get bound up and can not pick up any more of the compound which is why if you leave the area for a while and return the smell seems strong again.

There are similar but not as exstream things related to the hot coals. During the summer roads get very hot normally when people walk barefoot on a very hot road they limp and are in pain. I have found that by repeating the line 'pain into pleasure' I can walk on hot pavement or glass or snow barefoot and rather than hurting it actually feels kind of nice but you have to really think about it the second you stop concentrating it will start to hurt again. I wonder if athletes go through similar things when they are in the middle of competition and dont feel the pain until later.


Name: amse hammershaimb
Username: amseh@yahoo.com
Subject: hmmm...
Date: Tue Mar 28 20:36:15 EST 2000
Comments:
are set points gone awry the cause for hypersensitivity and/or reduced sensation? or is it the result of "firing" from the initial motor neuron that causes such things? the right side of my body has reduced sensitivity to the point that i have days wherein all topical feeling is gone. conversely, when there is someting sharp poking into me, i feel an intense pain, but as a generalized pressure rather than an acute poke. maybe these things are just chemicals gone awry in synapse and have nothing to do with set points. i just wonder about set points and my physialogical issues being connected because of the consistency of the thing.
Name: amse
Username: amseh@yahoo.com
Subject: hot coals
Date: Tue Mar 28 20:39:34 EST 2000
Comments:
just a thought about the hot coals ... has anyone considered fire eaters? tricks such as passing the flame and relighting versus the common extinguish require the eater to keep a lit flame on his/her tongue for whatever amount of time.


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