Muscle Flashcards
What can left ventricle failure result in? How?
Pulmonary oedema
Blood accumulation in pulmonary veins, increased blood pressure in these vessels, fluid pushed into the alveoli
What is left ventricle hypertrophy usually in response to?
In response to high blood pressure or another condition where the heart has to work harder
Which test can be used to treat for heart failure?
BNP test
What does BNP stand for? Are there increased or decreased levels when heart is working hard (failing)?
Brain natriuretic peptide
Increased levels
What is muscle hypertrophy?
The increase in size of muscle fibres in response to increased muscle work
What is muscle atrophy? What can cause it?
The reduction in size of muscle fibres
Muscle inactivity, malnutrition etc.
What are three indicators of muscle injury in the body? In which parts of the body are they found?
Creatine kinase (all muscle/brain)
Myoglobinuria (skeletal muscle)
Troponin (cardiac muscle)
What are the disadvantages of using creatine kinase as an indicator for myocardial infarction?
Levels can increase after intense exercise, or a fall etc. - so replaced by troponin
Is the quantity of troponin or creatine kinase measured proportional to the degree of damage of the muscle?
Yes - creatine kinase
No - troponin
Troponin will be found in increased levels during which type of scan? When should troponin levels be measured to test for muscle injury?
MRI
Within 20 hours
What does myalgia mean?
What does myasthenia mean?
What does myoclonus mean?
Muscle pain
Muscle weakness
Sudden spasm of the muscles
What does sarcolemma mean?
What does sarcoplasmic reticulum mean?
What does sarcoplasm mean?
Plasma membrane of a muscle cell
SER of a muscle cell
Cytoplasm of a muscle cell
What are the 3 types of muscle?
Cardiac
Smooth
Skeletal
Muscle can be grouped into which 2 categories? Which muscle types are in which categories?
Striated (cardiac, skeletal)
Non-striated (smooth)
What is the structure of skeletal muscle?
Long parallel cylinders for forceful contraction
Skeletal muscle fibres ________ in their diameter
Differ
What are the different types of skeletal muscle fibre? Order them by diameter.
Narrow RED fibres
Intermediate fibres
Wide white fibres
What is the difference in vascularisation and myoglobin abundance between white and red muscle fibres?
White = poor vascularisation/myoglobin
Red= rich vascularisation/myoglobin
Are there more mitochondria in red or white muscle fibres?
More in red fibres
How do red and white muscle fibres contract differently? How do they fatigue?
Red = fatigue slowly, slow repetitive contractions
White = fatigue quickly, fast strong contractions
Where are red muscle fibres found in high abundance?
Postural muscles of the back
Where are white muscle fibres found in abundance?
Finger muscles
Myoglobin is present in which types of muscle?
Cardiac and skeletal
What connects skeletal skeletal muscle to bone?
Tendons
Muscle fibres are grouped into bundles called _______
Fascicles
Bundles of fascicles make up the muscle, what surrounds these bundles of fascicles?
A muscle sheath (EPIMYSIUM)
What surrounds individual muscle fibres?
Endomysium
What surrounds individual fascicles in skeletal muscle?
Perimysium
Give an example of a muscle that is not connected to bone but to connective tissue?
Intrinsic muscles in the tongue
How can skeletal muscle be recognised on a micrograph?
Multinucleate cells, peripheral nuclei in transverse section
What do muscle fibres consist of?
Myofibrils
What do myofibrils consist of?
Thin actin filaments
Thick myosin filaments
Replacement of contractile proteins in muscle fibres happens every…
2 weeks
What are two types of atrophy? Briefly describe each?
Disuse atrophy (through muscle inactivity - decreased contractile proteins - decreased fibre diameter - loss of power)
Denervation atrophy - where the nerve to the muscle is cut
When does atrophy related to age begin?
30 yrs old
What is the cause of hypertrophy?
Increased contractile proteins, increased fibre diameter
How can muscle length be adjusted?
Addition (Stretching) or removal (limb in plaster) of sarcomeres
The ______ of sarcomeres leads to contraction
Shortening
Which filaments make up the A band of a sarcomere? What bands exist within the A band?
Thick myosin filaments
Dark M band, Light H band
Which filaments make up the I band of a sarcomere? Which bands exist in the I band?
Thin actin filaments
Dark Z line exists
Which is darker in appearance the A band or the I band?
A band
What happens in muscle contraction after the action potential travels down t tubules?
Calcium released from the SER
Calcium binds to actin filaments
Tropomyosin is removed from the active sites of actin
Myosin forms cross bridges and pulls actin to the centre of the sarcomere (using ATP)
Removal of calcium ions —> tropomyosin blockage restored
What are t tubules?
Extensions of the sarcolemma that pass by every myofibril of a muscle fibre, allowing depolarisation, shortening of sarcomeres and contraction
What is fibrillation?
Contraction of individual muscle fibres
What is fasciculation? Which disease can this indicate?
Contraction of whole muscle fascicles
Motor neurone disease
How can cardiac muscle be recognised from a micrograph?
Centrally positioned nuclei
Branching
Intercalated discs between adjoining cells
Are there myofibrils in cardiac muscle fibres?
No distinct fibrils, continuous filament mass in cytoplasm
How are muscle fibres often connected?
Gap and tight junctions
What is cell hyperplasia?
Method of increasing tissue size by multiplication of the cells
What types of molecules are natriuretic peptides? What do they do?
Peptide hormones
Work to reduce blood pressure by reducing blood volume
Elevated levels of ANP are found in patients with…
Mitral valve disease
Left ventricle hypertrophy
ANP is released by…
Atrial myocytes
BNP is released by…
Ventricular myocytes and in the brain
pro-BNP is split into which two diagnostic markers for heart failure?
BNP and NT-pro-BNP
The specialised myocardial cells that carry impulses to the ventricles from the AV node are called…
Purkinje Fibres
What are features of purkinje fibres?
They have abundant glycogen
Sparse myofilaments
Extensive gap junctions
What appearance to smooth muscle cells show?
Spindle shaped with a central nucleus
Does smooth muscle have sarcomeres or t tubules?
No
How are actin and myosin filaments arranged in smooth muscle?
Arranged diagonally spiralling down intermediate filaments
Smooth muscle is involuntary. Does smooth muscle show fast or slow contraction?
Slow
What are two types of modified smooth muscle cell?
Myoepithelial cells
Myofibroblasts
What role do myoepithelial cells play?
Form around the secretory units of exocrine glands - contractions aids in secretion of substances into glands
What role do myofibroblasts play?
Found at sites of wound healing, help in wound contraction and tooth eruption
Smooth muscle cells are innervated by autonomic nervous system fibres. Where is neurotransmitter released from these nerve fibres?
At varicosities into a wide synaptic cleft
How do skeletal muscle cells repair themselves?
Cannot divide
Tissue regenerates through the division of satellite cells
How does cardiac muscle repair itself?
Cannot regenerate
Fibroblasts lay down scar tissue
How does smooth muscle repair itself?
Retains mitotic activity to form new smooth muscle when needed
