Muscular System Flashcards
Musculoskeletal System (22 cards)
What is the purpose of the muscular system?
Movement, Posture & Stability
How does the muscular system provide movement?
Muscles work with the skeletal system to produce voluntary movements like walking, running, and jumping as well as involuntary movements like the beating of the heart or movement of food through the digestive system
How does the muscular system provide posture and stability?
Muscles help maintain body posture and stabilise joints even when you’re still standing.
What is posture?
Posture refers to the position in which the body holds itself while standing, sitting, or lying down
How is the muscular system organised to maintain posture?
Contractions of the skeletal muscles bring about movement at the joins.
They also give the body its form and contours and allow it to maintain posture.
How do we maintain posture?
Maintaining posture involves holding body parts in alignment, resisting the force of gravity, and keeping joints stable achieved through muscle tone
What is muscle tone?
The partial contraction of the skeletal muscles, even when not actively moving.
What are skeletal muscles?
Muscles that move bones and enable us to walk, run and carry out a wide range of voluntary physical activities.
These muscles are under conscious control and are attached to the bones of the skeleton.
How do skeletal muscles bring about movement?
Contractions of the skeletal muscles bring about movements at the joints.
They also give the body its form and contours and allow it to maintain posture.
What are smooth muscles?
These muscles are not under conscious movement (involuntary muscle).
Where is smooth muscle located?
It is found in the walls of internal organs such as the stomach and intestines
How do smooth muscles bring about movement to the alimentary canal?
When the smooth muscles that wrap around the alimentary canal contract, the diameter of the canal narrows, pushing the contents along.
What is the cardiac muscle?
A heart muscle
How does the cardiac muscle bring about movement?
When cardiac muscle contracts, it reduces the space in the chambers of the heart and pushes the blood from the heart into the blood vessels.
What happens when muscles contract?
The sarcomeres shorten.
The theory suggests that this occurs because the actin and myosin filaments slide over each other.
Describe muscle fibre contractions using the sliding filament theory
As the thin actin filaments slide over the thick myosin filaments, the Z lines are drawn closer together and the sarcomere is shortened.
This result in a shortening of the muscles fibres and, hence, a shortening of the whole muscle.
The myofilaments remain the same length in the contracted positions as they were before contraction.
The fibril has shortened because the myofilaments overlap more.
At any given time, some muscle fibres can be contracted, while others are relaxed.
Energy is required for the shortening of muscle fibres. This comes from the breakdown of ADP and a phosphate group.
When energy is available again, the ATP molecule is reformed, and energy is transferred to processes such as muscle contraction.
How are skeletal muscle cells held together?
Muscle cells are held in bundles surrounded by perimysium - a sheath of connective tissue that surrounds each bundle so it can function as an individual unit.
This allows adjacent bundles to slide easily over one another as they contract
How are skeletal muscle cell bundles held together?
Sheaths of connective tissue called epimysium also hold bundles together, and towards end of muscle they taper/blend to form tendon.
Describe the structure of muscle fibres in skeletal muscle.
Composed of muscle cells that lie parallel to each other.
Each muscle fibre is an elongated cylinder with many nuclei.
Around the cell is a thin, transparent plasma membrane, the sarcolemma, contain the sarcoplasm (cytoplasm).
Cells are between 10-100 mm in diameter and vary in length from a few millimetres to several centimetres.
Where are the myofibrils located?
Within the sarcoplasm of each fibre are thread-life myofibrils.
These lie parallel to each other and run the length of the fibre.
There may be anywhere from hundreds to several thousands of myofibrils in each fibre.
What is storage site for calcium ions
A tubular network the sarcoplasmic reticulum surrounds the myofibrils.
This is a storage site for calcium ions, which are released during muscle contractions.
Describe the structure of a myofibril
Each myofibril is composed of many smaller myofilaments made of protein, which are the actual units involved in contraction of muscle.
Thick myofilaments, composed mainly of the protein myosin.
Thin myofilaments, composed mainly of the protein actin.
The arrangement of thick and thin filaments within a myofibril gives a banded effect to the muscle.
It is these bands that give skeletal and cardiac muscle fibres their striated appearance when viewed under a microscope.
These striations allow myofibrils to be divided into sarcomeres.
