Muscles Flashcards
3 types of muscle - which are striated?
Skeletal - striated
Cardiac - striated
Smooth - non-striated
Myoglobin
Protein with similar structure to a single subunit of Hb - an O2 storage molecule, providing O2 to working striated muscles.
Higher affinity for O2 than Hb - gives up O2 in muscles, especially in low pH.
Released into bloodstream (myoglobinaemia) when striated muscle dies or damaged (necrosis or rhabdomyolysis).
Can cause renal damage - removed by kidneys into urine (myoglobinuria) - tea coloured urine.
Rhabdomyolysis
Muscle damage
Myoglobinaemia
Myoglobin in blood.
Myoglobinuria
Myoglobin in urine.
Sarcolemma
Outer membrane of muscle cell.
Sarcophagi
Cytoplasm of muscle cell
Sarcosome
Mitochondrion
Sarcomere
Contraction unit in striated muscle
Sarcoplasmic reticulum
Smooth ER of muscle cell
Myofibril structure (sarcomere)
Dark A band - H zone in centre, M line in centre of this
Light I band - Z band in centre
Skeletal muscle structure
Many myofibrils make muscle fibre (sarcolemma).
- muscle fibres surrounded by endomysium
Many muscle fibres make fascicle.
- fascicle surround by perimysium
Many fascicles make muscle, as well as blood vessels.
- muscle surrounded by epimysium
Tropomyosin
Stabilises structure of contraction unit.
Muscle contraction speeds
Slow, fast, intermediate
Muscle fibre types
Type 1 - slow twitch fibres (slow oxidative)
Type 2a - fast twitch fibres (fast oxidative glycolytic)
Type 2b - fast twitch fibres (fast glycolytic)
Type 1 fibres:
Capillary supply?
Aerobic/anaerobic?
Myoglobin levels?
Number of mito?
Number of cytochromes?
Colour?
How fast do they fatigue?
What type of activities are they used in?
Examples of actions
Rich capillary supply
Aerobic
High myoglobin levels
Many mito
Many cytochrome
Red in colour
Fatigue resistant
Endurance type activities
Standing/walking
Type 2a:
Capillary supply?
Aerobic/anaerobic?
Myoglobin levels?
Number of mito?
Number of cytochromes?
Colour?
How fast do they fatigue?
What type of activities are they used in?
Examples of actions
Rich capillary supply
Aerobic
High myoglobin levels
Many to intermediate no. of mito
Many cytochromes
Red to pink
Moderate fatigue resistance
Assist type 1 and 2b activities
Standing/walking (recruited 2nd)
Type 2b:
Capillary supply?
Aerobic/anaerobic?
Myoglobin levels?
Number of mito?
Number of cytochromes?
Colour?
How fast do they fatigue?
What type of activities are they used in?
Examples of actions
Poor capillary supply
Anaerobic
Low myoglobin levels
Few mito
Few cytochromes
White (pale)
Rapidly fatigue
Strength/anaerobic type activities
Standing/walking - recruited last
Jumping/running/sprinting
What are cytochromes?
Haemoproteins that functions as an electron shuttle in ETC - therefore more mito = more cytochromes.
What ion does continued muscle contraction rely on? + what energy molecule also needed?
Ca2+ ions (and ATP)
How do cardiac muscles look under the microscope?
Striated
Centrally positioned nucleus (1 or 2 per cell)
Intercalated discs
Branching
ANP
Atrial natriuretic peptide
Released by atria during heart failure
Specifically congestive heart failure
BNP
Brain-type natriuretic peptide
Released by ventricles
Specifically left ventricular hypertrophy, mitral valve disease
Hypertrophy
Cells increase in size
Hyperplasia
Cells increase in number
Smooth muscle - histology
Spindle shaped
Single central large nucleus
Form sheets, bundles or layers
Multiple adjacent capillaries
Very tightly packed
How are smooth muscle cells joined?
Gap junctions
Where is smooth muscle found?
Contractile walls of passageways/cavities
Involuntary muscle
- means it can cause high BP; painful menstruation; lung disease; abnormal gut mobility; incontinence
Eg small intestine
Is muscle repair possible?
- skeletal, cardiac, smooth
Skeletal:
Cannot divide - regenerate by mitotic activity of satellite cells so that hyperplasia follows muscle injury.
Cardiac:
Adult tissue generally considered to be incapable of regeneration
Damage - fibroblasts invade, divide and lay down scar tissue
Smooth:
Retain mitotic activity and can form new smooth muscle cells - very good at repairing themselves
What does it mean for a muscle to act as a syncytium?
Which muscle types do this?
Means wave-like function
Cardiac and smooth muscle do this
Satellite cells
Precursor cells to skeletal muscle cells - responsible for ability of smooth muscle to regenerate.
Neuromuscular junction - what is it? What neurotransmitter is used?
How does its action work?
Small terminal swellings of the axons.
Acetylcholine
Nerve impulse releases acetylcholine; binds to receptors on sarcolemma; initiates an action potential which is propagated along the muscle.
What is a kranocyte?
A connective tissue cell that resides over the terminal Schwann cell.
Functions not fully known, thought to anchor the nerve to the muscle cell.
What is myosin?
