Musculoskeletal - Muscles Flashcards
What does muscle do?
Converts energy, ATP, into mechanical energy
How do skeletal muscles convert mechanical energy into motion?
It pulls on bones, skin and organs
What are the key functions of skeletal muscle?
Movement, stability, communication, control of body openings and passages and heat production
How do muscles stabilise joints?
The muscles around the joints hold bones in the joints (especially in high mobility joints such as the shoulder)
How do muscles contribute to communication?
Control facial expressions, body language, writing and speech
How does skeletal muscle contribute to heat production? What percentage of body heat production is contributed by skeletal muscle?
Skeletal muscle is always slightly contracted and contraction uses energy and releases heat, contributes ~85% of body heat
What connects muscle to other tissue? What kind of tissue can skeletal muscle get attached to?
Tendons
Skin and bone
Label the diagram
What is junction that connects muscle to tendon?
Myotendinous junction
What is the junction that connects the tendon to the bone?
Osteotendinous junction
How can tendon attachments be classified? Explain them
Origin - The attachment site that moves the least/is stationary in space
Insertion - The junction which moves the most during contraction
What are the origin attachments normally closer to?
The axial joints
What is the cell of a muscle called?
Myocyte/myofibre
Label the diagram, what is this showing?
This is a myofibril
What is the cell membrane of a myocyte called? What is it very good at and why?
Sarcolemma
It is very good at conducting action potentials
What unique substance is found in the sarcoplasm of a myocyte? What does it do?
Myoglobin
Binds oxygen allowing the muscle cell to store oxygen
What is the basic contractile unit of myofibril?
Sarcomeres
What are the two bands that make up sarcomeres? What are their colours and locations in the unit?
A band - the dark band in the middle (FYI remember it as the dArk band)
I band - the light band on the ends and overlapping to the next sarcomere (FYI remember it as the lIght band in the mIddle of two bands)
Label the diagram, what is it showing? What is missing from this diagram? What is its function?
It is showing the myocyte
A thin basement membrane that surrounds the sarcolemma
Label the diagram, what is this showing?
This is showing a fascicle
What is the endomysium made of?
Losse irregular connective tissue
What does the endomysium do?
It contains the nerves and capillaries that supply the myocytes
Label the diagram of skeletal muscle
What are perimysium and epimysium made of?
Dense irregular connective tissue
What is the order of how deep the connective tissues are found in the skeletal muscle? Where are they found?
Endomysium (inside the fascicle)
Perimysium (inside the muscle)
Epimysium (Surrounding the muscle)
How does the orientation of the fascicles orientation determine muscle properties?
Impacts on muscle strength and contractile direction
What is subcutaneous fascia?
Fat under the skin
What is deep fascia?
A thin layer underneath subcutaneous fascia (i.e. fat) of regular and irregular dense connective tissue
Label the diagram
What are the walls that seperate compartments of the skeletal muscle called?
Investing fascia (ie intermuscular septa [septla between muscels] and interosseous membranes [membranes that are between the bones])
Within each seperate compartment of the skeletal muscle, what are some common characteristics?
They do the same action
Are supplied by the same artery/vein
Have the same nerve
What do the planterflexor and Dorsiflexor muscles do?
Planterflexor’s cause the foot to flex downwards (i.e. it is the calve muscle)
Dorsiflexor’s cause the foot to flex upwards
What is an advantage and disadvantage of the compartment structure of muscles?
Advantage - During contraction the muscles expand which aids venous return
Disadvantage - If there is infection/inflammation the muscles expand but the compartment doesn’t very much which causes the permanent compression of veins resulting in oedema –> causes nerves and arteries to compress = pain
What is hyperplasia? What kind of tissue can’t undergo this and why?
When tissue increase in size because of an increase in cell number (due to mitosis)
Muscle can’t do this because muscle cells are very large and have too much genetic material to undergo mitosis
What process allows for muscle to increase size? Explain how this can occur
Hypertrophy
1 - Muscle tissue is damaged and during repair more myofibrils are put into the myocytes causing an increase in muscle size
2 - Anabolic steroids which increases protein synthesis in the muscle and bones
What are anabolic steroids?
Synthesised variants of testosterone
What are some of the side effects of anabolic steroids?
Remember four
- Acne (overstimulates the pores on skin)
- Hair loss
- Hair in the wrong places (activates dormant hair follicles)
- Liver failure (liver is working hard to process these chemicals)
- Shrivelled testes (taking testosterone supplement causes leydig cells to stop working due to negative feedback loop)
- Infertility (lack of testosterone produced by leydig cells means there’s not enough for spermatogenesis and it also causes seminiferous tubules to close)
- Coronary artery disease (theses steroids are high in cholesterol)
- Mood swings (hormone inbalances)
What is the process of getting smaller muscles called? Explain why this occurs
Atrophy
When muscle isn’t used the body recycles the muscle material so it breaks down the myofibrils therefore cells get smaller
How does muscle mass change as we get older? What is happening that causes this trend?
As we get older muscle mass decreases because we become less able to repair muscle damage
What is severe atrophy called? What happens when this occurs?
Hypoplasia
This is when muscle cells die and are replaced with fat and connective tissue
What kind of cells are myocytes?
Syncytium cells (i.e. made from the fusion of many cells)
What kind of cells in the muscle tissues allow for the mitosis of cells that can then fuse with the existing myocyte?
Satellite cells/Myoblasts
How do satellite cells form? Where do they reside?
During the formation of myocytes not all of the myoblasts fuse and those that remain as individual cells become satellite cells
They reside beside the muscle fibres outside the sarcolemma but within the basement membrane
What do satellite cells do?
They (are the only cell in the muscle that can FYI) divide and fuse with each other and the myocytes to repair any damage that may occur to the myocyte (i.e. repair units of the myocyte that break down)
They also have a limited ability to replace muscle fibres that die from old age or injury
What are the connective tissues of the muscle?
Epimysium, perimysium and endomysium
What are the functions of the muscular connective tissue?
1 - Provide the organisation and scaffolding of muscle development
2 - Provide a conjugate for blood vessels and nerves (i.e. allow them to move through the muscle tissue)
3 - Prevent excessive stretching causing damage
4 - Distributes forces generated by muscle fibre contraction
How are sarcomeres connected to each other in a myofibril?
By their Z-lines
When a myofibril is cut or a sarcomere is non-functionion the muscle can still contract normally, how does this work?
The Z-lines of adjacent sarcomeres within a myocyte are held together by Desmin. This means that even if a single sarcomere is not working, the adjacent sarcomeres can still transfer contractile force through the fibre
Individual myofibrils do not contract evenly, how is the force evenly distributed evenly through the myocyte?
A protein complex (containing Dystrophin) connected the myofibrils to the myocyte and the endomysium transmitting contractile forces evenly
How does the protein complex contribute to the sarcolemma properties?
It helps to strengthen the sarcolemma
What is a condition that affects the strength of the sarcolemma? Explain how it occurs and its affects
Muscular dystrophy
This is where someone is unable to produce functional dystrophin resulting in myocytes with weaker sarcolemma that can tear easily
