Musculoskeletal 5 Flashcards
What is muscle tissue designed for?
Contraction
What does muscle convert?
Chemical energy (ATP) into mechanical energy
What is muscle tissue designed specifically to move?
Different parts of the body by pulling on another tissue.
What are 5 functions of muscle?
Movement Stability Communication Control of body openings and passages Heat production
Describe the movement function of muscle
Movement isn’t confined to the movement of bones in the skeletal system. Other examples of movement include; moving gut contents and lymph transportation (smooth muscle) and circulating blood (cardiac muscle)
Describe the stability function of muscle?
Muscle plays an important role in stabilising joints and maintaining posture and is especially important in stabilising joints that have a wide range of movement- in these joints, stability (normally provided by the ligaments and/or the articular capsule) has been replaced with active contraction of surrounding muscles
Describe the communication function of muscle
Muscles are used for facial expression, body language, writing and speech
Describe the function of control of body openings and passages in muscle
Ring-like muscle (spinchters) help control the admission of light (eyelid and pupils) and food and drink (muscles around the mouth) that enter our bodies. The elimination of waste is also controlled by the urethral and anal sphincters (smooth and skeletal muscle)
What is the passage of food and liquid through the gut normally controlled by?
Smooth muscle
Discuss the hear production function of muscle?
Skeletal muscle can produce as much as 85% of body heat and is used to maintain the body as 37 degrees for normal function
What is origin?
The attachment that moves the least during muscle contraction
What is insertion?
The attachment that moves the most during muscle contraction
What is the epimysium?
Dense irregular connective tissue surrounding the perimysium and the entire muscle
What is the perimysium?
Dense irregular connective tissue surrounding the fascicles
What is endomysium?
Loose irregular connective tissue surrounding myocytes. Contains the nerves and capillaries that supply the myocytes
What is the thin basement membrane between the myocytes and the endomysium?
A thin, specialised sheet of connective tissue that surrounds muscle fibres and blends with the endomysium
What is the sarcoplasm?
Cell cytoplasm in the area between myofibrils
What is the sarcolemma?
The fast-conducting cell membrane
Is the deep fascia part of the muscle?
No
What is a myofibril?
Many sarcomeres
What is a myocyte/myofibre?
A muscle fibre/cell- a bundle of myofibrils
What is a fascicle?
A bundle of myocytes
What is a muscle?
A bundle of fascicles
Is a myofibril an organelle?
Yes
What is a deep fascia?
A wrapping of dense connective tissue (regular and irregular) which covers the deep structures of the body
Where is the deep fascia?
It underlies skin and the subcutaneous tissue (also known as superficial fascia)
What are compartments?
Muscles that are supplied by the same nerves (innervation) or have a similar action can sometimes be found grouped together in regions
What are the outer sleeve and wall of compartments made of?
Deep fascia
What are investing fascia?
The walls or septa of compartments (eg intermuscular septa or interosseous membranes)
What happens to investing fascia when it comes into contact with bone?
It fuses with the periosteum
In most areas, can the outer layer of a muscle (epimysium) move and glide under the deep fascia?
Yes
In other areas, what is the deep fascia part of?
The muscle tendon and can act as an attachment point for the muscle
What is hypertrophy?
An increase in muscle size due to the increase in size of fibres
What is hyperplasia?
An increase in muscle size due to an increase in muscle fibres
What happens in hypertrophy?
The myocytes will increase in diameter with more myofibrils packed into each muscle cell and typically, the effect will be an increase in overall muscle size and strength but the same number of cells will contribute to contraction
What can stimulate skeletal muscle hypertrophy?
Various factors such as repetitive contraction of muscles to near maximal tension (heavy resistance training) and the use of anabolic steroids
What are anabolic steroids variants of?
The male sex hormone testosterone, which has been synthesised by pharmaceutical companies
What do anabolic steroids do?
Increase protein synthesis through their interactions with specific target tissues that include skeletal muscle and bone
Can anabolic steroids target other tissue besides muscle and bone tissue?
Yes
What are side effects of anabolic steroids when they affect other tissues?
Acne Hair loss Excessive hair gain in wrong places Liver failure Shrivelled testes Infertility Increased susceptibility to coronary artery disease Extreme mood swings "roid rage"
What is atrophy?
Decrease in the size of myocytes
When does muscular atrophy occur?
When muscles are not used or stimulated by motor neurons
What’s an example of atrophy?
When a limb is immobilised in a cast for a period of time or if a muscle is paralysed
What’s diseases is atrophy part of the complex pathology of?
Heart failure
Diabetes
Cancer
AIDS
What age does the normal loss of muscle mass start?
20
When is the rate of loss of muscle mass accelerated?
After the age of 50
By the time we reach 80, approximately how much of our muscle mass will be lost?
40%
What is muscle replaced by?
Fat and connective tissue
What is muscle mass loss often attributed to?
Individual fibre shrinkage (atrophy) and some is due to fibre loss (hypoplasia)- if atrophy is not permitted to proceed too far, it can normally be reversed
What are myoblasts?
Satellite cells
Where do satellite cells lie?
Beside muscle fibres outside the sarcolemma but within the same basement membrane
What are myocytes?
Large multinucleated cells, created when many myoblasts fused together (syncytium)
Can myocytes divide by mitosis?
No
What are satellite cells?
The only cells in muscle that can divide and fuse with other satellite cells and myocytes to repair any damage that may have occurred
Which cell has a number more or less set at birth?
Muscle fibres
Which cells have a limited ability to replace muscle fibres that die from old age or injury?
Satellite cells
What are the connective tissue layers of muscle like?
Epi, peri and endomysium, and they’re continuous and blend with each other at the appropriate level
What are the functions of of the fibrous connective tissue layers in muscle?
- Provide organisation and scaffolding upon which the muscle is contracted
- Provide a medium for blood vessels and nerves to gain access to myocytes
- Prevent excessive stretching and therefore damage to myocytes
- Distribute forces generated by muscle fibre contraction
What happens when sarcomeres in a myofibril are stimulated to contract?
All the Z lines are pulled together by the filaments that make up the A and I bands (sliding filament theory) in
What would happen if myofibrils acted independently?
Damage to one sarcomeres in the chain could render the entire myofibril useless (however this is not the case)
What can myocytes cut in “vivo” still do?
Exert a pulling force on the muscle tendons
What holds together the z lines of adjacent sarcomeres within a myocyte?
A number of structural proteins eg desmin
What do structural proteins do?
Help align sarcomeres between the myofibrils
What do proteins result in?
Sarcomeres that shorten together and pull in unison (which is believed to explain why skeletal muscle fibres (myocytes) have a uniform striated appearance under the microscope)
What is a protein complex (group of proteins) responsible for?
At the surface of a myocyte the Z lines of the outermost myofibrils are attached to the sarcolemma and to the surrounding basement membrane and endomysium
What does the protein dystrophin do?
It helps form the bridge between the myocyte and surrounding connective tissue, and is thought to contribute to the strengthening of the sarcolemma while transmitting contractile forces generated
What is muscular dystrophy?
A disease where the protein dystrophin is not transcribed correctly, or is missing which results in myocytes that have a weaker sarcolemma that can tear easily, eventually causing the death of the cell
