3. MUSCULAR SYSTEM Flashcards
Structure and function of different types of muscles in the human body. Major skeletal muscles and their functions. Signs, symptoms, investigation procedures and some orthodox treatments of muscular system pathologies.
List four functions of the muscular system
- Movement
- Maintaining posture
- Heat production
- Storage of substances (glycogen and oxygen)
- Movement of substances (heart muscle - blood; Digestive tract - food; Urinary system - urine; Diaphragm - draws air in)
Describe the difference between striated and non-striated muscle
Striated muscle contains cells that are aligned in parallel bundles, their different regions forming stripes that are visible under a microscope. (e.g. skeletal and cardiac muscle)
Non-striated muscle contains cells that are randomly arranged (no stripes visible) e.g. smooth muscle
Define the following properties of muscles:
a. Contractability
b. Excitability
c. Extensibility
d. Elasticity
a. Contractability - ability to contract
b. Excitability - ability to conduct an electrical current
c. Extensibility - ability to stretch without damage
d. Elasticity - ability to return to its original length and shape after contraction/extension
Name the three types of muscle in the body
Skeletal
Cardiac
Smooth
Which types of muscles are voluntary and which are involuntary?
Involuntary: Cardiac (heart); Smooth (blood vessels, walls of the gut, iris)
Voluntary: Skeletal
List two functions of skeletal muscle
motion
posture
speech
breathing
Explain the role of ‘fascia’
Fascia is a dense sheet of connective tissue that:
- organises muscle
- secures it to skin
- provides stability
What are ‘myocytes’?
The long cells that muscles are made up of (muscle fibres) are called myocytes.
How many skeletal muscles are there in the body?
640
What is the cell membrane of a myocyte called?
sarcolemma
Which organelle in the myocyte stores calcium and what is it used for?
The sarcoplasmic reticulum (smooth ER) stores calcium needed for muscle contraction
What is myoglobin?
A red coloured, iron and oxygen-binding protein contained within muscle cells (fibres/myocytes). It stores oxygen.
Why are the many mitochondria within muscle cells located close to myoglobin?
Mitochondria have great need of oxygen in order to produce ATP, and myoglobin stores oxygen which it can then easily access.
What are transverse tubules?
They are tubes that extend from the cell membrane into the cells, and helps to ensure that electrical impulses get into the cell.
Why are we born with a set number of skeletal cells?
Muscle fibres are formed from the fusion of cells called myoblasts in the embryo. This is why skeletal muscle cells contain many nuclei.
Once mature muscle cells are formed (becoming ‘myocytes’), they can no longer undergo mitosis.
Since muscle fibres do not undergo mitosis, how is it possible for damaged muscles to regenerate?
Through ‘satellite cells’ there is limited regenerative capacity. These are multipotent stemcells found in skeletal muscle between the sarcolemma and the basement membrane. They are quiescent in most healthy adult muscle tissue and are only activated in response to muscle injury.
Where is a) oxygen and b) calcium stored in a muscle fibre?
a) myoglobin
b) sarcoplasmic reticulum
Define ‘myofibrils’
Myofibrils are cylindrical columns formed of bundles of protein filaments within the muscle fibre. They are contractile threads arranged in a striated pattern. They are basically the cytoskeleton of the muscle cell.
Describe the two myofilaments that make up myofibrils
Actin are the thin filaments and Myosin are thicker filaments that are shaped like golf clubs.
What is meant by the term ‘sarcomere’?
A sarcomere is the basic unit of striated muscle and contains the following areas:
H zone = myosin filaments only
A band = dark area where actin and myosin overlap
I band = light area of only actin filaments
Z discs = filaments of actin that are arranged at 90degree angles at each end of the sarcomere