the last section for chapter nine which I know has been many different parts but the last part is just going to focus on the different muscle types that we haven't really mentioned not going to go in the physiology sections for each of these so I'm just going to make mention of some specific topics for each of these so the first one is smooth muscle these are mostly um involuntary muscles so we have no control over them this is all taken care of by our nervous system um we have two parts of the nervous system we'll eventually get to we'll mention a little bit more about this but we'll just going and talk a little bit about smooth muscles being our involuntary muscles and they do function somewhat differently they are shaped differently than the skeletal muscles we've looked at they are more spindle shaped and they have different types of components that allow them to contract so in smooth muscles there's more actin than actually mein because these muscles are not for strength they're more for just slow organized relaxed contractions so that's a little bit about them so the probably the biggest characteristics you should know is that they are involuntary and they definitely contain a lot more actin than mein so the cross bridging is important but as I said it's more for um the the making of smooth controll Rel uh contractions of our muscles so here's a little picture for you what our muscle fibers will look like in a smooth muscle tissue these are the ones that are weaved around each other they still have nuclei they are not necessarily multinucleated like the skeletal muscles are um and they have very different patterns of um their sarom mirrors and their myofilaments are different so they have instead mein and actin filaments located throughout the muscle cell and they're not organized in those parallel um sort of like accordion likee sarom mirors it's very different the way they are because it's not Contracting like a Bendy straw or like an accordion not everything's Contracting in that way we have contractions happening throughout the cell as you can see here so they contract in a spiral like pattern or a WAV like pattern so between this image here if you look you can see the way the sarom mirors are set up they are not parallel but when they do start to contract we get contractions in all area of the cell so it's sort of very much in a WAV like pattern or spiral like pattern a twisting motion when each muscle cell contracts so that parallel nature needed for our skeletal and uh cardiac muscle is not seen here so smooth muscles definitely contract uh at a slower speed and that is due to um the way the calcium is released uh from the sarcoplasmic reticulum it also has to do um with the innervation with how the muscles are um stimulated by the nerves and it's also due to the fact that um the contraction has to enter the cell from extracellular fluid so the calcium comes from the outside as well as from the sarcoplasmic reticulum so the diffusion rate is different for the calcium um and then how the action comes from the action potential again is slightly different and our cross bridging that's going to occur is definitely more uh less less cross bridging than what we're look we're used to with what I've expressed in the skeletal muscle so here's a picture I'm not going to ask you the steps or anything like that but I did want you to see just an image of our uh smooth muscle fiber has a phospholipid by layer it does have calcium outside there are calcium channels and then we still have um molecules inside the cell that are going to act in similar ways to help it contract but they're not the same so in in order for calcium to function you will see there's something called calmodulin that's needed whereas in the skeletal muscle we use something called troponin so they have different molecules present but again there's their function is somewhat different and obviously when you see this picture here you're going to see a whole lot less mein and again way more actin especially the length of the actin for these so the cross in is different and how the process works is different as well but I'm not necessarily going over all those steps for you because it's not um something we want to focus on here functioning of the skeletal muscle is going to be much more important you can take a look at the scenario of desane muscular distrophy which is a genetic condition that starts to happen to muscles um of children and the muscle weakness where it starts where it ends and the things that are going to happen internally with their smooth muscles especially as the condition develops over time with Duan MUSC muscular DIY they do give you a chart here I like these charts so that you can see how all of the different systems of the body are impacted whether it's just from a genetic condition as this one is or when we did the very first one with the burns on the human body they do get you to start thinking about everything involved with the muscle contractions um for other conditions we have cramps whether they be in the skeletal muscle or they can be in the uterine muscles wherever those cramps come from we do have other things that happen to our muscular system from the hypertrophy to atropy to the diseases that we've mentioned um myasthenia gravis is one specifically I mentioned in the earlier part of this chapter in section 9.1 because that definitely impacts our skeletal muscle with the fact that it uh destroys our acetycholine receptors which will prevent an action potential from getting to a muscle fiber so functional properties of the smooth muscle just goes over and Recaps some of the things we've already mentioned um they are for your internal organs they do happen involuntarily and they have what we call autorhythmic contractions you many of you if you've ever heard of peristalsis which is the movement of this um muscles to help food go from your mouth to your stomach and from your stomach to your intestines that the esophagus contracts in an autorhythmic pattern and that is peristalsis and that's actually how food gets from one end of your digestive tract to the other is through this rhythmic Auto rythmic contractions called peristalsis smooth muscle tends to contract in responses to being stretched so think about when food is when you swallow food that's been chewed the esophagus is stimulated to start that peristalsis contraction because a bulkier object has stretched the esophagus same thing happens in the stomach and the intestines and so forth um smooth muscle exhibits what we call relatively constant tension it does have um some sort of minor contraction to it uh that all of our organs have they can be overstretched over time like with anything our urinary bladder can be overstretched over time um and in some cases they can actually even be controlled to some extent um learning to control your urinary bladder is something that is is learned over time and that has to do with the the nervous system stimulating it even though there is some smooth muscle present there uh the amplitude of the contractions produced by smooth muscle uh was generally constant um and but the length will vary um depending on what is being swallowed what is moving through the intestines or obviously what's in the uterus or the bladder for example so here are some examples for the smooth muscles and where they're found but they are pretty much found in all hollow organs um the stomach is there the urinary bladder is there the uterus can be in there as well um so lots of different organs will have these smooth muscles uh we have something called the autonomic nervous system we have not gotten to that yet but we will and that is the system the part of the nervous system that that's going to what we call inovate or stimulate smooth muscles um this is an involuntary um portion of the nervous system that will control your muscles very specifically the most important neurotransmitters that will be released from the nerves to stimulate muscle cells we still have acetylcholine which is the same one that was used um for the skeletal muscles and now we're adding in something called norepinephrine which is also very important for smooth muscles you can take a look at the rest of the section but I will move over to section 9.9 so we can take a look at our cardiac muscle cells 9.9 we'll just focus on the cardiac muscle just to go over some key uh characteristics about them and then we'll finish with the aging process cardiac muscle is found only in the heart is found nowhere else in the body it is very similar to muscle tissue uh the skeletal muscle tissue and the fact that it does have those striations it Sarco mirrors are very close together unlike the um smooth muscle we just covered they do join to each other which is different than skeletal muscle skeletal muscles run parallel to each other um like I said it's like grabbing a bunch of straws and holding together that's very much like skeletal muscle cardiac muscle is uh parallel but but they have branches so their adjacent cells do join so we say that they have what we call branching muscle fibers that is um very important for the way they communicate with each other so that they can beat or the heart can beat in a very rhythmic pattern um adjacent cells do join to each other um and the attachments are called intercalated discs the last section is about the effects of aging and skeletal muscle most muscles in the body whether they're skeletal smooth or cardiac they do age over time all right obviously our heart muscles are meant to last forever they start beating in utero and they will last till the day that you die same with all the other muscles but there is atrophy along the way especially if they're not taken care of or for some reason something happens to a person and they are their their ability to move or exercise or walk is somehow impacted then obviously everything else will shift and atrophy a lot quicker so the primary consequence of Aging is called sarcopenia which is muscle atrophy due to age so the age related reduction in muscle mass happens to everyone it does actually start happening as if you read at 25 years of age and then by 80 the muscle mass has been reduced by about 50% that is generally what happens to people who are not active so if you stay active with walking with gentle weightlifting e even as you age you don't have to be a bodybuilder any kind of gentle tension where your muscles have to still contract and then relax while lifting some sort of very light W weight is very important not just for your muscles but when you have your muscles Contracting with a little bit of weight that also puts tension on the tendon which then puts t uh tension on the bone and that keeps your bones actually re um Remodeling and keeps your bones healthy again keeping in mind that you need your calcium you need your Vitamin D you need all those other things as well but gentle working out can take place your whole entire life and it's very important to stay healthy and to keep muscle mass from being reduced by that about 50% so it's very important that people keep in mind that exercising at any age is incredibly important and the use of muscles throughout your life can be very important for staying healthy and for living a long life you cannot control what happens to you along that way but at least getting out exercising lifting light weights doing whatever it is that you do to stay healthy will keep you in overall great shape even as you age and the most important thing as you age is retaining your posture muscles and your walking muscles because most people as they age they become more sedentary and that is when they're going to be more susceptible to a fall when they do stand up and they do start to walk so keep that in mind as you're aging yourselves or getting older or or just because you're young doesn't mean you don't need to start thinking about how you're going to exercise and stay healthy as best you can throughout the rest of your life okay so this is the end of chap chapter 9 as always there is a great section at the end you can print out the highlighted notes of this section you'll have those so you can add to them but if you need a way to go back and organize this chapter visually for yourself all the parts are here again we did have separate recordings for this section but those separate sections were because they were so long so don't forget to take a look at this little outline that's at the end of the chapter for each section that will help you to recap everything we talked about there also are the review and comprehensive questions that are always there and as well as some critical thinking questions before we get to the next chapter