Biology 304
Biology 304
Smooth muscle can be found in a wide range of organs. These organs tend to be tubular, soft tissue organs designed for transporting stuff. Stuff can be blood, air, sperm, food, lymph, babies, venom etc. Name a non-tubular organ that has smooth muscle. What is the function of the smooth muscle in that organ? How can you tell if muscle tone is increasing or decreasing? Be able to describe a series of contractions by indicating whether rate, strength or tone is changing.
Although we performed a few other alterations on the tissues in lab, you are only responsible for understanding the ones listed on this site.
WARNING!
All tracings in this lab should be more-or-less sinusoidal. If the machine is drawing a straight line, or a series of waves with the top or bottom flat, then something is wrong!
Usually, this is because the transducer is set too high or low on the retort stand. The lever arm of the transducer should be pivoting around the horizontal position, so adjust the height of the transducer to make this so. The problem may also be that the offset is incorrectly adjusted.
The tracing above is a classic example. Note the flat lines between peaks...this is not natural!
Uterus
Tension: Adding plasticene to the free end of the transducer lever caused a stretch in the uterus. What does this mimic in life? What was the response?
Figure 1. This isn't a grand example
(the bottoms of the contractions appear cut off), but note the change in size of the contractions. Contraction is upwards.
Figure 2. Relaxation is upwards in this figure. Plasticene was added at the
line, note the initial lengthening of the tissue (tone is decreasing) but the
contraction strength does eventually increase.
Oxytocin: What were the effects of adding oxytocin to the uterus preparation? Note that oxytocin typically causes deeper contractions as well as the effect illustrated. Which ion is responsible for the depolarization of the muscle membrane? Where is oxytocin synthesized? From where is it released?
Figure 3. Contraction is downwards in this figure.
Figure 4. Contraction is downwards in this figure.
Progesterone tends to give the opposite effect on the uterus as does oxytocin. Progesterone injections are used clinically to prevent premature labour.
Figure 5. Contraction is downwards in this figure. Note the decrease in rate, normally, strength decreases, too.
Figure 6. Contraction is downwards in this figure. Describe the change
in the contraction.
Insecticide: Chlorpyrofos is an acetylcholinesterase inhibitor. What is the mode of action, and what other pharmaceutical does it mimic?
Figure 7. Contraction is downwards.
Intestine
Normal, rhythmic contractions of the gut. It is not unusual to see all contractions of the same strength, rather than this pattern.
Aeration was stopped until an irregular contraction regime was noted. In general, smooth muscle can last without air for quite awhile, though that is not always true. How do the results here compare with the skeletal muscle lab in which we did not supply air at all? What is in the air that is necessary for long term function of the smooth muscle?
Figure 6. Contraction is downwards in this figure. A very
nice example of perturbation and recovery.
Figure 7. Contraction is upwards in this figure.
Figure 8. Contraction is upwards.
Temperature was changed by adding cold Tyrode's PS. We were doing the experiment at 37 °C, why? What was the effect of decreasing the temperature?
Fig. 19. Contraction is downwards.
Epinephrine (=adrenaline) is secreted from the adrenal glands whereas norepinephrine (=noradrenaline) is a neurotransmitter. These are the substances responsible for the fight or flight syndrome. Epinephrine suppresses activity in the gut and enhances activity in several other places of the body (where?) to prepare you for action. We also used adrenaline in the lab dealing with the heart. How did the reactions differ?
Figure 8. Contraction is downwards in this figure.
Figure 9. Contraction is upwards in this figure.
In general, acetylcholine (ACh) has opposite effects to adrenaline on any given organ. Did you find this? How do adrenaline and ACh work? Which part of the action potential is affected? Which ions? Atropine is to muscarinic receptors as curare is to nicotinic receptors.
Figure 10. Contraction is downwards in this figure.
Figure 11. Another good example. What is happening to a) tone b) contraction
strength and c) rate?
Contraction is downwards in
this figure.
Both eserine and atropine (belladonna) are drugs derived from plants. Atropine is a muscarinic cholinergic blocker, while eserine is an anticholinesterase. In other words, atropine blocks the receptor sites for ACh; eserine blocks acetylcholinesterase (AChase) from working. If AChase does not prevent the neurotransmitter ACh from working, then its effect is prolonged. Both are dependant on ACh being in the tissue if they are to show there effects. If no ACh was added prior to either atropine (fig. 5) or eserine (fig. 6), how could they have had their effects?!?
Figure 12. Contraction is downwards.
Figure 13. Contraction is downwards.
Figure 14. Contraction is
upwards.
Figure 15. Contraction is upwards.
Nicotine is an agonist of acetylcholine, but (supposedly) only fits into nicotinic cholinergic receptors; the gut is supposed to only contain muscarinic cholinergic receptors. Interesting stuff...here's what happened when we put nicotine on the gut.
Figure 16. Contraction is downwards in this figure. Note that there is a transient increase in tone and contraction strength, followed by a marked decrease in tone.
Figure 17. Contraction is downwards.
Every chemical process (and therefore every tissue, organ or organism) works best at an optimum temperature. The effectiveness of the tissue will be lower the farther away from this optimum temperature you get. Being warm blooded, gerbils work best at a core temperature of 37 °C. In general, a general increase in tension was seen with the addition of cold Tyrodes.
Figure 18. The cold Tyrodes was added just prior to recording (baseline contractions are not available). However, this tracing does show the effect of gradually warming up the tissue. Contraction is downwards.
Thanks to all who contributed their data!
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St. Francis Xavier University
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