Anatomy and Physiology 2 Exam 1 1 1 What are the different types of muscles Cardiac muscle is only found in the heart thus the name and it is an involuntary muscle Contraction of this muscle propels blood form the ventricles throughout the body It is uninucleated and it is also striated meaning if you are viewing it from a microscope there are clearly defined repeating segments These are the sacromeres contractile unit Smooth muscle is also involuntary and has one nucleus like cardiac muscles It differs in that it is not striated Smooth muscle surrounds most organs and is used to transport material For example the esophagus propelling food or the large intestine moving food by peristalsis Skeletal muscle is the only voluntary muscle type in the body and it is also striated like the cardiac muscle It has many nuclei unlike cardiac and smooth muscle Skeletal muscle plays the defining role in locomotion force and power production and any form of human movement 2 Define and identify the anatomy of a sarcomere within skeletal muscle and explain the sliding filament theory leading to muscle contraction The sacromere is the unit of the muscle that is involved in the contraction There are three types of muscles in the human body and they are cardiac smooth and skeletal So everything is in layers for example the outside covering of the muscle is called the epimysium Then the perimysium surrounds a group of muscle fibers which are packaged into bundles called fasicles and the endomysium surrounds an individual fiber Now that we got down to the fiber we look further at it and it contains repeating units called myofibrils The saromere is another name for the myofibril and it is the smallest contractile unit of the fiber and it repeats many times along the muscle and this gives origin to the striated patterns o Looking at an individual sarcomere you will see proteins called the myofilaments These are the actin thin band and myosin thick band that you will hear so much about The sarcomere is separated into different segments depending on the presence of different myofilaments The I band contains just actin and the A band contains both actin and myosin Now in the middle of the A band is the H zone which is just myosin Then the Z disks separate each Tony Berardi 2 sarcomere since the fiber is composed of hundreds to millions Now to the mechanism of the contraction For contraction to occur the myosin protein head attaches to the actin and essentially pulls the actin to contraction Normally though the actin is covered by another protein called tropomyosin and this has to be moved for the myosin to do its job The process of contraction starts with an action potential and this propagates and depolarizes the sacroplasmic reticulum stores Ca 2 The action potential AP will travel down the neuron to the neuromuscular junction synapse to the muscle then it will travel down a structure called the t tubule and it will spread the AP to the terminal cisterea which lie next to the t tubule The purpose of all this is to get the AP to the center of the muscle thus it travels down the t tubule The terminal cisterea will release Ca 2 into the muscle and this binds with troponin which is another protein on the actin Once it binds to troponin tropomyosin is signaled to move from the actin so the myosin head can bind Once attached the head pulls the filaments together This is called excitation contraction coupling The Z disks on the sarcomere are literally pulled closer together they contract and thus the I band will decrease size in length since being pulled together The H zone will disappear as it is covered via the sliding action 3 Define and distinguish between the types of muscle fibers and explain the possibilities or lack there of of hyperplasia and fiber type morphology So the sarcomere is the smallest contractile unit of the muscle fiber and there are three types of fibers which differ in the proteim form on the myosin Type 1 is what is called the slow twitch fibers meaning they are fatigue resistant for endurance In order to have the endurance they have a lot of mitochondria to supply all its energy and a high capillary density because more capillaries mean more blood and more blood means more oxygen for energy Type 2a is an intermediate of both types Type 2x is the fast twitch fiber and is used to power and shorts bursts of energy They would have few mitochondria since they don t supply energy as long as type 1 Type 2x 2b is the fast twitch fiber and is used to power and shorts bursts of energy They would have few mitochondria since they don t supply energy as long as type 1 Now muscle gain is due to hypertrophy which is an increase in the size of the fiber Hyperplasia means muscle fibers grow in number and this DOES NOT happen in humans The only Tony Berardi hyperplasia that happens in the body is with adipose tissue You can lose muscle fibers with age and it s called sarcopenia Now type 2x is found in humans and 2b is found in animals not humans though Not sure which nomenclature he used 3 4 State the different types of skeletal muscle contraction and the functions and characteristics of skeletal muscle All muscles share the same characteristics and these are excitability contractility elasticity and extensibility The functions are obviously to produce movement heat to stabilize and to maintain posture Now for the different functions that a muscle can produce There is concentric movement which means the muscle is shortening Think of it as the muscle is overcoming the load placed on it so it contracts There is also Eccentric movement which is when the muscle lengths or the load is greater than the force that the muscle generates so it will lengthen Some other terms are isometric pushing a wall meaning same length isotonic such as free weights meaning same tension and isokinetic biodex machine expensive ass machine meaning same velocity Occlusion training is a technique to train that involves cutting off the blood flow to the muscle so it gets fatigued faster Highly effective with hypertrophy If you want to know more email me 5 What is a motor unit And how are motor units recruited according to the size principle A motor unit is a neuron that and all the muscle fibers it is innervated to so when that neuron sends its action potential to the fibers they all contract Now to go over the size principle This just means that no matter what the activity is the motor unit with the fewest fibers fires first So
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