Muscles exam2 Flashcards
Identify and describe briefly the functions of muscle
Skeletal muscles
These muscles are responsible for voluntary movement, posture, and energy metabolism.
Cardiac muscles
These muscles are found only in the heart and are responsible for pumping blood.
Smooth muscles
These muscles are found throughout the body and are responsible for shortening and propelling contents across organ systems.
energy, posture, birth, temperature, movement digestion, waste
▪ Describe gross anatomy of muscles (tendons, fascia & mysium layers [connective tissue],
fascicles, fibers (cells), myofibrils, myofilaments). Order - superficial to deep
Tendon:
muscle to bone, contraction
Epimysium:
The outermost layer of connective tissue that encloses muscle, support and movement
Fascicle:
A bundle of muscle fibers forming the visible “grain” of a muscle.
Perimysium:
The connective tissue sheath that surrounds each fascicle, separating them within the muscle.
Muscle Fiber (Cell):
surrounded by the endomysium, containing nuclei and myofibrils.
Endomysium:
The thin layer of connective tissue allowing for capillary blood supply.
Myofibril:
A long, cylindrical organelle within the muscle fiber, containing proteins actin and myosin.
▪ Formation of skeletal muscle cells (myoblasts to muscle cells + satellite cells)
through a process called myogenesis, which involves the fusion of myoblasts into multinucleated cells called myotubes:
Satellite cells are stem cells that are responsible for the growth, maintenance, and repair of skeletal muscle
▪ Compare and contrast the 3 types of muscles
Cardiac muscle
This involuntary muscle is found in the heart and is responsible for pumping blood throughout the body. Cardiac muscle cells are striated and have a single nucleus per fiber.
Skeletal muscle
This voluntary muscle is attached to the skeleton and is responsible for movement, posture, and energy metabolism. Skeletal muscle fibers are striated and have alternating dark and light bands.
Smooth muscle
This involuntary muscle is found in the walls of organs, blood vessels, and other areas of the body. Smooth muscle fibers are spindle-shaped and have tapered edges. They are not striated and are often wrapped around the organs they are associated with.
▪ Which muscle types are activated voluntarily vs involuntarily?
Skeletal muscles are activated voluntarily, while cardiac and smooth muscles are activated involuntarily;
▪ How are muscle fibers arranged? (circular A.K.A sphincter, convergent, parallel and pennate)
Parallel
The most common arrangement, with fascicles that run parallel to the muscle’s long axis. Parallel muscles shorten more than other types of muscles. The sartorius muscle in the thigh is an example of a parallel muscle.
Circular
Also known as sphincters, these muscles are arranged in a ring-like band around a body opening. They constrict and relax to control flow. The orbicularis oris muscle, which surrounds the mouth, is an example of a circular muscle.
Convergent
Also known as triangular muscles, these muscles have a broad origin and fascicles that converge on a single tendon. The pectoralis major muscle in the chest is an example of a convergent muscle.
Pennate
These muscles are shaped like feathers, with fascicles that attach at an angle to a central tendon. The deltoid muscle in the shoulder is an example of a pennate muscle.
▪ What are the terms describing the action of skeletal muscles (agonist, antagonist, synergist)
Agonist (Prime Mover):
The muscle that contracts to produce the main force for a specific movement.
Antagonist:
The muscle that opposes the action of the agonist, typically relaxing when the agonist contracts.
Synergist:
A muscle that helps the agonist by stabilizing the joint or adding additional force to the movement
▪ Compare and contrast the 3 types of levers (first class, second class, third class
First class lever
The fulcrum is between the input and output forces. The direction of the applied force changes. Example seesaws.
Second class lever
The output force is between the input force and the fulcrum. The direction of the applied force does not change. Examples bottle openers.
Third class lever
The input force is between the fulcrum and the output force. The direction of the applied force does not change. Examples brooms, hammers
▪ Define sarcolemma, sarcoplasm, sarcoplasmic reticulum, terminal cisternae, T-tubule
Sarcolemma
The cell membrane that acts as a barrier between the inside and outside of the muscle cell. The sarcolemma is selectively permeable to water and other substances.
Sarcoplasm
The cytoplasm of the muscle cell that contains elements of the sarcoplasmic reticulum and T-tubules. It plays a key role in muscle contraction by helping to concentrate calcium ions.
Sarcoplasmic reticulum (SR)
A membrane-bound structure that surrounds the sarcomere and stores calcium ions. The SR is made up of terminal cisternae, longitudinal SR, and corbular SR.
Terminal cisternae
An enlarged area of the SR that surrounds the T-tubules. The terminal cisternae contain RyR2 receptors and form the dyadic cleft with the T-tubules.
T-tubules
Extensions of the sarcolemma that run into the center of the muscle cell. The T-tubules are closely associated with the terminal cisternae and are responsible for propagating the action potential deep into the muscle fiber.
▪ Describe muscle contraction action using myofilaments and the 2 regulatory proteins (troponin
and tropomyosin). What needs to be present for contraction to take place?
Actin and myosin
Actin is the primary component of thin filaments, while myosin is the protein that makes up thick filaments. During contraction, the heads of myosin filaments attach to actin filaments and pull them past each other, shortening the sarcomere.
Tropomyosin and troponin
These proteins control cross-bridge formation. In a relaxed muscle, tropomyosin blocks the binding sites on actin filaments, preventing myosin from interacting with actin. When calcium binds to troponin, it moves the troponin complex away from the actin-binding site, freeing actin for myosin to bind to.
▪ Describe components of a sarcomere & muscle contraction (pull not push, why?)
Thick filaments: Made of myosin, these filaments have a diameter of 15 nanometers.
Thin filaments: Made of actin, these filaments have a diameter of 5 nanometers.
Regulatory proteins: Troponin and tropomyosin are regulatory proteins found in the sarcomere.
Z-line: Actin molecules are bound to the Z-line, which forms the borders of the sarcomere.
M-line: A specialized region in the center of each A-band.
Costamere: Connects the sarcomere to the sarcolemma.
they can’t extend beyond their resting state to push a bone away from them
▪ Understand the organization of thin and thick filaments from a microscopic view.
thin filaments (primarily composed of actin) appear as lighter strands, anchored at the Z-discs, and interdigitate with thicker, darker filaments called thick filaments (mainly made of myosin), which are centrally located within the sarcomere, creating a repeating pattern of light and dark bands characteristic of striated muscle; the thick filaments are connected to each other at the M-line, with the thin filaments extending into the space between them, allowing for the “sliding filament” mechanism of muscle contraction.
▪ Describe the neuromuscular junction
a chemical synapse that connects a motor neuron to a muscle fiber, allowing the motor neuron to signal the muscle to contract
▪ Describe motor units (motor neuron, neuromuscular junction & muscle fibers)
A motor unit is a functional unit within a muscle, consisting of a single motor neuron, its axon branches, and all the muscle fibers
Motor neuron:
A nerve cell located in the spinal cord that sends electrical signals to muscle fibers.
Neuromuscular junction (NMJ):
The specialized synapse where the motor neuron axon terminal meets the muscle fiber, allowing the transmission of the electrical signal to the muscle.
Muscle fibers:
The individual muscle cells that contract when stimulated by the motor neuron, with different types of muscle fibers (slow twitch, fast twitch) contributing to varying muscle functions.
▪ Identify & describe type of muscle contraction (isometric vs isotonic=concentric & eccentric)
Isometric
length remains constant, while muscle tension changes. This type of contraction occurs when you push against an immovable object or try to lift a weight that is too heavy.
isotonic muscular contraction occurs without significant resistance, with a marked shortening of muscle fibers, and without a great increase in muscle tone.
Concentric
muscle shortens, and the muscle tension is sufficient to overcome the load. This type of contraction occurs when you perform a biceps curl or stand from a squatting position.
Eccentric
The muscle lengthens, and the muscle works to decelerate a joint at the end of a movement. This type of contraction occurs when you walk.
