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?
Be able to describe a series of contractions by indicating whether rate, strength or tone is changing. How can you tell if muscle tone is increasing or decreasing?
Although we performed a few other alterations on the tissues in lab, you are only responsible for understanding the ones listed on this site.
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
1. Contraction is upwards. Chart recorder speed was 1.0 cm/min. What differences
occur in tone, rate and contraction strength?
The temperature was changed by adjusting the water temperature in the water jacket. Instead of discreet recordings at each temperature, the recording was continuous. What happened? Describe the change in tone, contraction strength and contraction rate.
Fig. 2. Contraction is upwards.
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
3. Contraction is upwards in this figure. Toad.
Figure 4. Contraction is upwards in this figure. Gerbil.
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 5. Contraction is upwards in this figure. Toad.
Figure
6. Contraction is downwards in this figure. Gerbil.
Figure
7. Another good example. What is happening to a) tone b) contraction
strength and c) rate?
Contraction is downwards in
this figure. Gerbil.
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
8. Contraction is downwards.
Figure
9. Contraction is downwards.
Figure 10. Contraction is
upwards.
Figure 11. Contraction is upwards.
Nicotine is an agonist of acetylcholine. Nicotine fits into nicotinic cholinergic receptors better than it does into muscarinic cholinergic receptors. Interesting stuff...here's what happened when we put nicotine on the gut.
Figure 12. Contraction is upwards. Toad. The light blue line shows all the data;
for clarity, I've added the black line which samples only ever 200 points. Toad.
Thanks to all who contributed their data!
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St. Francis Xavier University
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