Muscles Flashcards
General Function of Muscles
Muscle tissue is specialized to convert CHEMICAL ENERGY into KINETIC ENERGY - energy of MOVEMENT
All muscles can contract (SHORTEN)- when they contract some part of the body or the ENTIRE body moves
Smooth Muscle Cells
- Long & tapered at each end
- Have one nucleus
- Usually arranged in parallel lines forming sheets
- Found in many parts of the body such as walls of certain blood vessels, the iris of the eye, walls of internal organs
- Contracts INVOLUNTARY
- Slower to contract than skeletal muscle, it can sustain prolonged contractions & does not fatigue easily
3 Types of Muscle Cells
Smooth Muscle
Cardiac Muscle
Skeletal Muscle
Cardiac Muscle Cells
- Forms the wall of the heart
- Cells are tubular and striated (Have bands of light & dark)
- Have ONE nucleus
- Branched- create a net-like structure
- Contracts INVOLUNTARY
Controlled by the nerves of the autonomic nervous system
Skeletal Muscle Cell
- Are tubular and striated
- “Meat” (Flesh) of animal bodies in skeletal muscle
- Contraction is VOLUNTARY- consciously controlled by the nervous system
- Humans have over 600 skeletal muscle
- Very long cells with many nuclei- length need for energy & materials require them to be controlled by many nuclei
- Usually referred to as fibres rather than cells
Tendon
Attaches each end of a muscle to a different bone
Skeletal Muscle Functions
- Supports the body contraction of skeletal muscle opposes the force of gravity & enables us to stand
- Allows body to move- allows for movement of bones, arms, legs, eyes, facial muscles, breathing
- Helps maintain body temperature- muscle contraction causes ATP to break down which releases heat that can be distributed throughout the body
- Helps to protect internal organs
- Stabilizes joint
Cooperation of Skeletal Muscle
- When muscles contract, they SHORTEN this means muscles can only PULL not PUSH
- When a muscle contracts, there needs to be a force available to later stretch it back to its returned state- to do this muscles work in pairs each performing the opposite action
- Ex. in your arm the bicep muscle causes the arm to flex (bend) as the muscle shortens and the triceps muscle, causes the arm to extend (straighten). When the triceps muscle contracts, this stretches the relaxed bicep muscle.
Skeletal Muscle Consists of bundles of fibres
Each skeletal muscle in the body lies along the length of a bone
- Muscle fibres can be up to 20 cm long and are organized into many longer bundles making up the muscle
- A layer of connective tissue wraps around each fibre, another layer wraps around each bundle of fibres, and another wraps around the whole muscle itself
- Blood vessels & nerves run between the bundles of muscle fibres
- Rich blood supply provides muscle fibres with nutrients & oxygen to power contraction & remove cell waste
- Nerves trigger & control muscle contractions
- Most of the volume of a muscle fibre consists of hundreds of thousands of cylindrical subunits called myofibrils
- Each myofibril is made of even finer myofilaments, which contain protein structures that are responsible for muscle contractions
- The rest of the volume of muscle fibre consists of numerous mitochondria & other organelles common to cells
Myosin
Protein that makes the muscle contracts
Thick myofilaments
Actin
Protein that makes the muscle contracts
Thin myofilaments
Myofilament
A thread of contractile proteins found within muscle fibres
Actin & Myosin are a type of myofilaments
Organization of Skeletal Muscle fibres
Muscle–> Muscle fibre bundles –> Muscle fibres –> Myofibrils –> Myofilaments
Tropomyosin
Prevents myosin from binding to actin
Steps of Muscle Contractions
- Calcium ions flood into sarcoplasm (cytoplasm of muscle cell)
- Calcium binds to the protein troponin which causes tropomyosin to shift position & expose the binding site on the actin molecule
- Myosin uses ATP
- Myosin head binds to the binding site on actin with the help of the protein tropomyosin
- Myosin pulls actin towards the center of the sarcomere (Muscle fibre)
- ATP causes detachment of the myosin head from actin
- Calcium releases & dissolves
- Troponin/ Tropomyosin release (Goes back to normal spot)
