oh sorry there just uh stretching out my facial muscles so i don't pull a muscle during this video which isn't about facial muscles but it is about muscles we have over 600 muscles in the body in this video we're going to look at 15 of those 15 common superficial muscles that control the movement of different joints like our elbow and shoulder joint we're going to look at these muscles in terms of antagonist pairs how pairs of muscles working against each other help us control each of the joints in our body we'll learn some movement terms such as flexion extension abduction adduction rotation we'll learn some origins and insertions basically the points where the muscles attach to bones that they're moving and we'll learn the difference between isometric and isotonic contractions so we're only learning a small fraction 15 out of the over 600 muscles but we're going to learn a lot of concepts that go with these as we go through all these 15. so let's jump to the white board and get started all right before we get into the muscles themselves there's several terms that we need to learn we'll start with some movement terms the first one is flexion now flexion is any time you're taking a joint and you're decreasing the angle of it so for example whenever you contract the bicep muscle and that bends the elbow that would be an example of flexion if you do the opposite movement and you extend the elbow or increase the angle of that joint then we call that extension so flexion and extension are opposites of each other flexion is whenever you decrease the angle of a joint extension is whenever you increase the angle of that joint and they're kind of opposite movements for most of our joints and this idea of opposite movements gets into one of the big ideas of this video which is antagonist pairs in that example of bending and extending the elbow joint we have an antagonistic pair of muscles the biceps will flex the joint or decrease the angle the triceps have to do the opposite movement and extend the elbow joint if your bicep is contracting then your tricep is relaxing and vice versa and so we call those an antagonist pair it allows the joint to move one way and then back the other way and it's controlled by two different muscles these two diagrams demonstrate those terms if you have extension you're going to increase the angle between the humerus bone here and the radius and the ulna by moving the arm down this way but if you flex that elbow joint you're going to decrease the angle by moving your radius and ulna or your lower arm up this way and therefore decreasing that angle between those bones so those are flexion and extension but we have other motions that our joints could do as well one of those is rotation rotation is just going to be turning a joint and usually when we talk about rotation we need to indicate a direction such as i'm going to rotate my shoulders medially or i'm going to rotate my shoulders laterally so we usually pair the word rotation with a directional term to indicate which direction we're rotating that joint next we have the terms abduction abduction is movement away from the midline so to abduct my arm i'm going to take my arm and move it away from my midline i think of this like being abducted by aliens like you're getting taken away from something it's taken away from the midline and the opposite of that is a very similar sounding word adduction and i just think of addition i'm adding it back to my torso so when i add duct to my arm i return it back to my side or back to the midline so i abduct the arm but i can also adduct the arm so even though those terms are pretty similar i think there's a good way to remember them abduct and adduct those aren't all the movement terms but those will be the main five that we'll use in the muscles that we're looking at in this video now all muscles in your body connect to at least two points usually those are bones and all the examples we look at here these muscles will connect to different bones in the body to pull on them and cause us to move the two bones that the muscles connect to have names we have the origin and this is going to be whatever bone the muscle attaches to that doesn't move the opposite of that is the insertion the insertion is going to be the bone that does move so if i think of bending my elbow as an example my biceps brachii muscle connects from my scapula up here down to my radius down here and whenever that contracts it's going to move the radius the radius is the bone that actually moves so that would be the insertion the origin is going to be the bone that doesn't move and that was the scapula whenever i bend my elbow my scapula isn't really moving right here my radius is therefore my scapula is the origin and my radius is the insertion whenever i'm trying to identify origins and insertions i find it helpful to identify the insertion first because it's easiest to tell what's moving and then to go back and say okay what would the origin be that this could be pulling on to cause that movement to happen so origin doesn't move insertion does move finally there's two types of contractions that we're going to look at those are isometric and isotonic that prefix iso just means same so let's look at isometric first iso means same metric means length so isometric means same length and this is whenever you're contracting a muscle but no movement happens so for example if i try to lift up on my desk right now i promise you this muscle is contracting right now but nothing's happening there's no movement happening right so that would be an isometric contraction i'm straining really hard but there's no movement happening so it's isometric same length or in other words no movement the opposite type of contraction is isotonic and we're going to look at more isotonic contractions throughout this video isotonic means the same force and this is going to be when there is movement happening so for example if i'm lifting up this book and i can track my bicep to do that i'm applying the same force onto this book as i lift it up now if this book were really heavy and i tried to lift it and there was no movement happening well then i would be changing the amount of force that i'm trying to push up with but if there is movement happening that's happening with about the same force the whole length of the contraction so we call it isotonic or same force the main thing to remember though is that isotonic contractions are with movement isometric contractions are with no movement so with all that terminology out of the way let's actually look at some muscles whoa this person looks intense muscle diagrams always look super intimidating am i right we'll move from the arms to the shoulder to the torso and then down to the legs so we'll start off with this this is the biceps brachii muscle the action of the biceps brachii is to flex the elbow and we've seen that in an example already the origin of the biceps brachii is up in the scapula and the insertion is going to be the radius so it's going to pull between the scapula and the radius in order to flex the elbow joint now its antagonist is the triceps brachii the action of the triceps brake guy is to extend the elbow joint or to straighten it back out the triceps brachii originates at the proximal end of the humerus and it attaches to the proximal end of the ulna and it's going to pull on that ulna to straighten the elbow out or extend the elbow so biceps brachii triceps brachii up next we have the deltoids and the deltoids are your shoulder muscles and their purpose is going to be to take your arms and raise them now raising your arms like that is an example of abduction so abducting the arms is the function of the deltoids the deltoids originate in the clavicle and the sternum and they insert to the humerus so they're going to pull like this to lift up the arm now the antagonist of the deltoid is actually two different muscles which we'll look at now first we have the pectoralis major muscle the pectoralis is going to rotate your shoulders anteriorly so whenever you can track these muscles right here it pulls your shoulders forward an example of a workout you can do here is a pec fly on a machine or it could be a bench press and you're rotating your shoulders forward whenever you push the weights out so the pectoralis major rotates the shoulders anteriorly the antagonist of the pectoralis major is the latissimus dorsi muscle the latissimus dorsi is found in your lower back on both sides its origin is actually your lumbar spine down here as well as your ribs and it's going to connect to the humerus up here in the arm and what it does is it's going to pull on that humerus back so it acts as an antagonist to the pectoralis major pectoralis major rotates your shoulder forward latissimus dorsi rotates your shoulder backwards and sort of down or you could say it rotates it posteriorly now both of those muscles pull your shoulders down a little bit either down and forward or down and back so together they work as the antagonist to the deltoids which abduct the arm so deltoids can abduct the arm pectoralis major and latissimus dorsi together adduct the arm bring it back down to the midline now another important muscle to the shoulders is the trapezius muscle the trapezius muscle is kind of in the neck and the shoulders back in this region right here its origin is the thoracic and cervical spine as well as the base of the skull and its insertion is the clavicle in the scapula and the trapezius is all about moving your scapula so if you move your scapula which is back here around like this you're using your trapezius in order to do that okay that feels good i need to stretch out my trapezius a little bit all right from there let's move down to the abdominal muscles we have the rectus abdominis muscle and that's going to be when you think of abs you're thinking of the rectus abdominis this is your six pack your eight pack your 10 pack your 12 pack bro the movement of the rectus abdominis is going to be to bend the spine actually think about doing a sit up and your and your spine sort of bends that's the action of the rectus abdominis and that's why doing an ungodly amount of sit-ups could potentially maybe give you that six-pack abs that you're hoping for it connects from the anterior part of the pelvis right here to the costal cartilage of the ribs right here and pulls those together which is how it bends the spine so rectus abdominus flexion of the spine or bending of the spine laterally to the rectus abdominus are the external abdominal obliques they're called obliques because they're not parallel or vertical like this they kind of run a diagonal so we call those obliques and the external abdominal obliques do vary similarly but they can also contract either one at a time which can bend you down like this so it's kind of like doing a sit up but kind of to the side they have similar origin insertions which are the pelvis and the ribs so we've looked at muscles that control the elbow joint the shoulder joint the spine now let's look at the hip joint the two prime movers here are the gluteus maximus the gluteus maximus extends the hip joint or straightens the hip joint out it originates on the pelvis and inserts on the femur so it's going to bend that femur back or bend it posteriorly now the antagonist of the gluteus maximus we don't see in our diagram because it's an internal muscle that muscle is called the iliopsoas it's the antagonist of the gluteus maximus whereas the gluteus maximus extends the hip joint this is going to flex the hip joint and here's a picture of that muscle so you can see a little bit what it looks like so gluteus maximus extends the hip joint iliopsoas flexes the hip joint now we'll look at muscles that control knee movement the first one we have is the biceps femoris not to get confused with the biceps brachii your biceps femoris are also called the hamstrings so these are your back leg muscles and their job is going to be to flex the knee joint the biceps femoris or hamstrings are going to originate in the pelvis and the femur and their insertion or the movement part is the tibia and the fibula so they're going to pull on the tibia and the fibula to cause those to move or to flex the knee to bend the knee bend the knee game of thrones reference probably not i'll edit that out the antagonists of the hamstrings or biceps force are the quadriceps now the quadriceps are really four muscles we have the rectus femoris right here the vastus lateralis down here the vastus medialis and between those deep or underneath all of this is the vastus intermedius those four muscles make up the quadriceps or your quads the quads are in charge of extension of the knee are straightening your knee joint back out and their origin includes the pelvis and the femur and their insertion is going to be the patella and the tibia so they're going to pull up on that kneecap and the tibia whenever you straighten out the leg now we've got another muscle here that maybe doesn't belong on this list but i think it's a cool muscle and that's called the sartorius the sartorius is actually the longest muscle in the body and it's going to connect from the lateral part of the pelvis right here down to the medial part of the tibia and i always think of this as the stinky leg muscle if you do the stinky leg you got to use your sartorius do the stinky leg do the do the stinky leg is that how it goes i don't know music so the sartorius will rotate the knee laterally if you sit cross-legged you have to use your sartorius to sit that way it's a way to get your knees to the side last but not least let's take a look at two muscles that control the ankle joint the first one is the gastrocnemius and that prefix gastro means stomach and it has nothing to do with your stomach except for the fact that whoever discovered this muscle said hey this looks kind of like the shape of the stomach and now we'll call it gastroenterous forever the gastrocnemius connects from the femur right here down to the calcaneus in the heel it's going to pull the heel up which will extend the ankle now technically we call this plantar flexion of the ankle because it moves the foot in the plantar direction which is the downward direction or towards the the base of the foot but i also like to think about it as extending or increasing the angle of the ankle joint its antagonist is the tibialis anterior which is named because it's connected to the tibia and it's on the anterior side the tibialis anterior connects the tibia up here to the tarsal bones down here and that's going to pull your foot upward i think about this as flexion of the ankle but to be technically accurate we need to call this dorsal flexion because it's flexing the ankle toward the dorsal side or the top side of the foot so the gastrocnemius does plantar flexion of the ankle joint and the tibialis anterior does dorsiflexion of the ankle joint this has been a lot let's recap all these muscles but not worry too much about the origins and insertions and just focus on where is the muscle and what is its movement we have the biceps brachii which are going to flex the elbow joint we have the triceps brachii which will extend the elbow joint we have the deltoids which will abduct the arm or move the arm away from the midline or raise the arm we have the pectoralis major which will rotate the shoulders anterior and the latissimus dorsi which will rotate the shoulders posterior and a little bit down we have the trapezius which will move the scapula up and down and rotate the scapula and all that we have the rectus abdominus which will bend the spine like doing a crunch or a sit-up and we have the external abdominal obliques which do the same thing but it'll help you bend down to one side or the other we have the gluteus maximus which will extend the hip joint or move your leg backward or posterior and the antagonist of the gluteus maximus is the iliopsoas muscle it's an internal muscle that's going to be a hip flexor that flexes or bends the hip muscle like whenever you kick a ball you're using your iliopsoas muscle controlling the knee joint we have the biceps femoris which will flex or bend the knee and we have the quadriceps muscle which will extend or straighten out the knee we have the sartorius or the stinky leg muscle which rotates the knee to the side or laterally we have the gastrocnemius which is going to bend your foot down or plantar flexion of the foot and we have the tibialis anterior which will raise the foot or dorsiflexion of the foot all right here's a blank diagram now take a moment pause the video see if you can identify all of these 15 muscles as well as the action of each muscle what movement does it cause all right here are those muscles again so you can check and see how many you got right this is going at the end of the video look like you're gonna be a really big [Music] slug