Muscles Flashcards
What are the three main types of muscle tissue?
Skeletal: allow movement by pulling and pushing on the skeletal bones. Cells are long, cylindrical, striated and multinucleated. Combined with nervous and connective tissue. New muscle cells can be produced by stem cells in adult skeletal muscle, these cells are called satellite cells. Meaning that skeletal muscles can partially repair after injury. (Striated voluntary muscle).
Cardiac: pushes blood through the circulatory system. Cells are short branched and striated, usually with a single nucleus. Cells are connected by intercalated discs, that are locked together via desmosomes, intercellular cement and gap junctions. Ions move through the gap junctions helps coordinated the contraction of the cardiac muscle. Does not rely on nerves input for contractions. (striated involuntary muscle).
Smooth: pushes fluids and solids through the digestive system and regulates the diameter of small arteries, amongst other functions. Cell are short and spindle shaped, nonstriated (as actin and myosin are arranged differently) and with a single central nuclease. Smooth muscle cells can divide and so can regenerate after injury. Smooth muscle cells can contract on their own with gap junctions between adjacent cells coordinating contractions. It is controlled by the nervous system under involuntary control. So is know as nonstriated involuntary muscle.
What are the five main functions of skeletal muscles?
Produce skeletal movement: muscles contract and pull on tendons that result in skeletal bone movement.
Maintain posture and body position:
Support soft tissue: act to protect and support internal organs.
Guard entrances and exits: The openings of the digestive tract and the urinary system are encircled by skeletal muscle and allow the voluntary control of swallowing, defecation and urination.
Maintain body temperature: some of the energy used for muscle contracts is released as heat and this helps to keep the body temperature within its normal limits.
What is the structure of skeletal muscles
There are 3 types of connective tissue that form part of the muscle tissue. The epimysium (cover the whole muscle tissue and separates it from surrounding tissues and organs. The perimysium divides skeletal muscles into a series of bundles. The endomysium surrounds the individual skeletal muscle fibers. The last two have a blood, nerve supply. They all connect up at the end of the muscle tissue as tendons and attach to bone.
The conduction through the muscle fibers in via T tubules so that the conduction is quick and all muscle fibers can contract simultaneously. Electrical activity travels from the sacrolemma to the T tubles to the muscle fibers. Inside the muscle fiber there are high quantities of mitochodria and nuclei. Mitochrondia produces the ATP required for muscle contraction.
Inside muscle fibers there are circular structures called myofibrils. Each skeletal fiber contains hundreds of thousand of myfibrils. They are composed of acin and myosin. Actin forms thin filaments and myosin forms thick filaments. These make up repeating functional units sacromeres.
There are specilized ion pumps in the myofibrils that keep the intracellular Ca2+ ion concentration very low.But there is a high concentration within the terminal citernae.
ACh is released at the neuromuscular junction (NMJ).
Organisation of skeletal muscle fibers
Bundles of muscle fibers are called fascicles . The muscle fibers in the fascicles are parallel, but the organisation of fascicles in the skeletal muscles can vary, as can the relationship between the fascicles and the tendons. There are four main types of fascicles organisation: parallel, covergent, pennate and circular.
Parallel: Most skeletal muscles are parallel for example in the arm the bicep. When contracting all fascicles move parallel to one another. So the muscle shortens and increases in width.
Covergent: the muscle fibers spread over a broad area spreading out like a fan and attach at a common point tendon (aponeurosis) at the apex. Connvergent muscles pull in different directions and so when all the muscle is contracting it is not as strong as a parallel muscle. Additionally separate parts of the muscle can be contracted independently. Example of this type of muscle is the chest muscle the pectoralis.
Pennate: contains more muscle fibers than a parallel muscle of the same size and so produces more tension. It pulls a tendon at a common angle. Pennante muscles can be unipennate, bipennate and multipennate. This referes to the position of the fibers on the side of the tendons. The triangular deltoid muscle of the shoulder is multipennate.
Circular: the fibers are concentrically arranged around an opening or recess. When the muscle contracts the diameter of the opening decreases. Found in digestive and urinary tract and mouth,
What are the different types of levers and their role?
First class: found in the neck the fulcrum (joint) lies between the applied force and resistance.
Second class: the resistance is between the applied force and the fulcrum. A small force can balance a larger weight. Example is plantar extension where the calf muscle is the applied force. Speed and distance are reduced.
Third-class: Most common levers in the body here the force is applied between the resistance and the fulcrum. Speed and distance are increased. seen in the biscep.
Discuss origins and insertions
Origin is where the fixed end of the muscle attaches to the bone, cartilage, CT. The site where the free moveable end attaches to another structure is called the insertion of the muscle.
The agonist is the prime muscle responsible for the movement of the joint/bone. Antagonist is the muscle that opposes the force from the agonist muscle. One flexes while the other extends.
A synergist helps the agonist to work more efficiently. They can also be described as fixators as they can stabilise other joints by preventing their movement.
