Muscles Flashcards
(29 cards)
What is cardiac muscle?
Short and branched muscles that contain striations. They have one or two nuclei on each fibre. They have branched fibres. They are also called myocardium. They function involuntarily.
What is smooth muscle?
These are found in hollow organs. They flex and contract involuntarily. They aren’t striated and have no nuclei.
What is skeletal muscle?
These are muscles attached to a bone or tendon, they are long, tubular, and striated. They are multinucleated, and you can choose how they move. They can only contract and relax. When contracted, they shorten, and when relaxed, they lengthen back to their original form. They can only pull (contract) so muscles work in pairs, where one contracts and the other relaxes. Muscles that bend joints are called flexor muscles, and muscles that straighten the joints are called extensor muscles. They also stabilize the joints and help maintain body heat.
What is muscle fibre?
A single long, cylindrical muscle cell, also called a myocyte. They’re the building blocks for skeletal, smooth and cardiac muscles. They are made up of myofibrils. They are multinucleated when found in skeletal muscles.
What does each type of muscle fibre do?
Skeletal muscle fibres are responsible for voluntary muscle movements. Smooth muscle fibres control involuntary movements such as those in the digestive system. Cardiac muscle fibres are responsible for the rhythmic contractions of the heart.
What are muscle fibre bundles?
This is when muscle fibres are organized into bundles called fascicles, which are surrounded by connective tissue.
What is myofibril?
This is an organelle composed of many myofilaments. It has many parts, such as the sarcolemma, sarcoplasmic reticulum, and others.
What is the sarcolemma?
The plasma membrane of the muscle cell, also the cell membrane of the muscle cell. It surrounds every muscle fibre.
What is the sarcomere?
This is the contractile unit of the muscle fibre. Each one is composed of two main elements, actin and myosin, which are responsible for muscle contraction. This relates to the sliding filament model.
What is thick myosin filament?
This is used during muscle contraction. It is myosin. The heads of the myosin filaments attach to the oppositely oriented thin actin filaments and pull them past one another, which is called the sliding filament mechanism. They are responsible for generating force during muscle contraction. The m-lines rest at the end of them and anchor them. They are located in the A-band.
What is thin actin myofilament?
These create a binding site for the myosin’s globular head. When they are pulled towards the center of the sarcomere by the myosin, this makes the muscles contract. They are anchored to the end of the sarcomere by the Z-lines. They are located in the I-band. Tropomyosin regulates their interactions. Troponin initiates its contraction with calcium ions. This is contained in the I-bands.
What are antagonistic pairs?
Groups of muscles that work in opposition to each other, with one contracting as the other relaxes and vice versa. The biceps and triceps are a good example. One flexes and the other relaxes to move the elbow. This is shown in the skeletal muscle section.
What are tendons?
Tough, fibrous cords of connective tissue that attach the muscles to the bones. They enable muscles to form bones and joints.
What are ligaments?
Bones are attached using ligaments. These are composed of stretchy strands of collagen fibres. They are slightly stretchy. They are connective tissues. They hold one bone to another, forming joints. They prevent joints from going the wrong way, such as how your elbow will not bend backwards.
What is the sarcoplasmic reticulum?
A specialized form of the endoplasmic reticulum of muscle cells that stores and releases calcium ions. It is necessary for muscle contraction and relaxation.
What are Z-lines?
This defines the border of the sarcomere, which is the fundamental unit of muscle contraction and anchors the actin muscle filaments. The muscles contract as the two edges of the Z-line are pulled together by the sliding filament model. They are also where the I-band connects.
What are the A-lines?
These are the thicker, darker lines of myosin that overlap parts of the actin. They attach to the M-line, which is a line in the center of the sarcomere.
What are the I-lines?
These are the lighter bands of actin that are part of the sarcomere. They attach to the Z-discs, which are on the outside of the sarcomere.
What is cartilage?
A tough, flexible and resilient connective tissue that cushions joints and provides structural support and helps with smooth movement.
What are synovial joints?
The most common joints in the body that are fully movable and allow for smooth movement between bones. They have joint cavities and synovial fluid that prevents friction.
What is sodium used for in muscles?
It transfers nerve signals throughout the body, enabling muscle contraction and relaxation.
What is calcium used for in muscles?
It is used for muscle function and regulates muscle contractions by triggering the actin and myosin filaments. Calcium ions are released from their storage in the sarcoplasmic reticulum when the muscle is signalled to contract, and they bind to the troponin on the actin filaments, exposing the binding sites for myosin heads to connect, forming a cross-bridge.
How does myosin work in the sarcomere?
They pull on the actin and shorten it, making the muscle contract. They have a head that is able to break ATP bonds, turning them into ADP and P, which is how they get energy to form the cross-bridge and power stroke.
What is the sliding filament model in steps?
- Resting muscle.
- Nervous signals from the brain cause calcium to be released from the sarcoplasmic reticulum.
- Calcium binds to the troponin.
- Tropomyosin is repositioned, revealing the actin sites.
- Cross-bridge forms as myosin heads bind to actin.
- Power stroke occurs as myosin slides and the Z-lines are pulled together, which makes them contract.
- ATP binds with the myosin.
- Calcium detaches from the troponin and is pumped back into the sarcoplasmic reticulum.
- The tropomyosin covers the actin’s binding sites again.
- Myosin lets go of the actin.
- The muscle relaxes again, and the myosin and actin slide and the z-lines move farther apart again.
- Hydrolysis breaks the ATP into ADP and a phosphate molecule.
- Myosin changes into a ready position to let it bind to the actin.
- The brain sends the nervous signals, restarting the cycle.
