Anatomy Physiology II Exam 1 Study Guide Muscles 1 What are the different types of muscle a Cardiac muscle only found in the heart involuntary muscle Contraction of this muscle propels blood from the ventricles of the heart to the rest of the body Uni nucleated and striated under a microscope you can see the clearly defined repeating segments b Smooth muscle involuntary also contains one nucleus like cardiac muscle However unlike cardiac muscle it is not striated Surrounds most organs and is used to transport material An example is the large intestine moving food by peristalsis c Skeletal muscle however it has many nuclei Plays the defining role in any human movement the only voluntary muscle type in the body Striated like cardiac muscle 2 Define and Identify the anatomy of a sarcomere within skeletal muscle and explain the sliding filament theory leading to muscle contraction The sarcomere is the contractile unit of the muscle The muscle is arranged in layers and to understand the sarcomere we must understand the layers of the muscle o Outer layer is the epimysium surrounds the muscle o Perimysium is the middle layer which surrounds a group of muscle fibers packaged into groups called fascicles o the endomysium is the innermost layer and it surrounds each individual muscle fiber of a muscle fiber Now that we are down to the individual fibers we can talk about the sarcomere o Each muscle fiber contains smaller units called a myofibril a basic rod like unit o Each myofibril is composed of a sarcomere proteins organized into thick myosin and thin actin filaments which repeat along the length of the myofibril If we go even deeper to an individual sarcomere you can see that it s separated into different segments made up of different myofilaments or proteins I band contains just actin A band contains both actin and myosin o In the middle of the a band is the H zone which is just myosin The Z Disks separate each sarcomere since they are composed of hundreds millions of fibers Muscle Fasicles Fibers myofibril Sarcomere myofilaments Now let s talk about the physiology of muscle contraction o Normally the actin is covered by a protein called tropomyosin This needs to be moved in order for contraction to occur o Contraction starts with an action potential which depolarizes the sarcoplasmic reticulum The AP travels down the neuron to the neuromuscular junction o Eventually the AP reaches the center of the muscle terminal cisternae and causes it to release Ca2 into the muscle Calcium binds to troponin another protein in the way of the actin This binding signals the other protein tropomyosin to move from the actin so the myosin head can bind o Once attached the myosin head pulls the filaments together excitation contraction coupling The Z disks are literally pulled closer together contract and the I band will decrease in size and length The H zone will disappear as it is covered during the sliding action 3 Define and distinguish between the types of muscle fibers and explain the possibilities or lack thereof of hyperplasia and fiber type morphology As we just learned earlier the sarcomere is the smallest contractile unit of the muscle We mentioned the roles of actin and myosin however there can be three different types of myosin that can be formed o Type 1 aka slow twitch fibers fatigue resistant for endurance Large amount of mitochondria to supply energy and a high capillary density for increased bloodflow which means more oxygen Few mitochondria since they don t supply energy as long as type 1 an intermediate between type 2b and type 1 aka fast twitch fibers used for power and short bursts of energy o Type 2b 2x o Type 2a Hyperplasia is defined as an increase in the number of cells This does NOT happen in muscle tissue in humans Muscle tissue grows through hypertrophy an increase in the size of each muscle fiber not an increase in number of fibers However you can LOSE muscle fibers with age sarcopenia In terms of morphology type 2b is only found in animals and type 2x is found in humans 4 State the different types of skeletal muscle contraction and the functions and characteristics of skeletal muscle All muscles share the same characteristics excitability contractility elasticity and extensibility These are to produce movement heat stabilized and maintain posture There are a few different types of skeletal muscle contraction the muscle is shortening Muscle is overcoming the load placed on o Concentric o Eccentric it so it contracts the force the muscle generates o Isometric o Isotonic o Isokinetic the muscle lengthens because the load placed on it is greater than muscle stays same length i e pushing against a wall tension on muscle is same as the load i e lifting free weights muscle moving at same velocity as load i e biodex machine 5 What is a motor unit and how are motor units recruited according to the size principle made up of a motor neuron and the skeletal muscle fibers that are motor unit innervated by that neuron o Whenever this neuron sends an action potential it causes all of the fibers it innervates to contract The size principle simply means that no matter what the activity is the motor unit with the fewest fibers fires first As the intensity of the action potential increases you first recruit slow twitch fibers then fast twitch fibers 6 What are the different types of fascicle arrangements Also what determines a muscle s The different types of fascicles refer to the arrangement of the muscle in the body They power and ROM are o Convergent broad origin fascicles converge toward a single tendon of insertion triangular or fan shaped muscle pectoralis major o Parallel fascicles run parallel to the long axis of the body sartorius o Pennate refers to muscles which have short fascicles attaching to a central tendon that runs the length of the muscle Unipennate insert into only one side of muscle extensor digitorium longus Bipennate insert from opposite sides of the tendon rectus femoris Multipennate arrangement looks like many feathers side by side deltod Depending on how the fascicles are arranged the ROM and power will be affected ROM stands for range of movement Basically the muscle with the most fibers will be the strongest 7 Describe the 3 classes of levers and apply the knowledge to uses of mechanical advantage and muscle insertions to determine lever classes in the body Every skeletal movement in the human body is performed by a lever system with bones There are 3 different
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