Muscle Flashcards
What does myalgia mean?
Muscle pain
What does myasthenia mean?
Weakness of muscles
Define myocardium
Muscular component of the heart
Define myopathy
Any disease of the muscles
Define myoclonus
A sudden spasm of the muscles
Define sarcolemma
Outer membrane of muscle cell
Define sarcoplasm
Cytoplasm of muscle cell
What are the two main classifications of muscle tissue?
Striated and non-striated
What are the two types of striated muscle?
Skeletal and cardiac
What is a type of non-striated muscle?
Smooth muscle
Where can red skeletal muscle typically be found?
Limb muscles
Postural muscles in back
Breast muscle of migrating birds
Where can white skeletal muscle be found?
Extraocular muscles
Muscles controlling fingers
Breast muscle of domestic hen
True or false: myoglobin is present in skeletal, cardiac and smooth muscle
FALSE - not present in smooth muscle
Which type of mammals have high amounts of myoglobin in their muscles and why?
Diving mammals to allow them to remain submerged for longer than air-breathing mammals
What is a perimysium?
Connective tissue carrying nerves and blood vessels
When does muscle atrophy occur?
Destruction > replacement
When does muscle hypertrophy occur?
Replacement > destruction
What are the symptoms of disuse atrophy?
Limb immobilisation
Sedentary behaviour
Bed rest
What causes disuse atrophy?
Loss of protein -> reduced fibre diameter -> loss of power
How can muscle loss be resisted?
Exercise
How is muscle length increased?
Frequent stretching
Complete the sentence:
Skeletal muscles are composed of _________, composed of muscle fibres, composed of ___________, composed of myofilaments (______ and ______).
Fascicles
Myofibrils
Actin and myosin
Which three molecules make up the thin filaments of skeletal and cardiac muscle?
Actin
Tropomyosin
Troponin
What are troponin assays used as a marker for?
Cardiac ischaemia
What is an important enzyme in metabolically active tissues like muscle?
Creatine kinase (CK)
CK used to be measured to diagnose what?
Myocardial infarction
CK is an enzyme released into the blood by damaged skeletal muscle and the brain. What can a rise in plasma CK result from? (6)
Intramuscular injection Vigorous physical exercise A fall (elderly) Rhabdomyolysis (severe muscle breakdown) Muscular dystrophy Acute kidney injury
Describe the structure of a thin skeletal muscle filament
Actin filament forms a helix
Tropomyosin molecules coil around the actin helix, reinforcing it.
Troponin complex is attached to each tropomyosin molecule
Which troponin subunit does ionic calcium bind to in order to result in muscle contraction?
TnC
What is rigor configuration?
Myosin head tightly bound to actin molecule
Complete the sentences:
Hydrolysis of ___ causes the uncoupled myosin head to bend and advance a short distance (___). The myosin head bends weakly to the _____ filament, causing release of _________ _________ which strengthens the binding and causes myosin head to return to its former position. ___ binds to myosin head and causes detachment from actin.
ATP 5nm Actin Inorganic phosphate ATP
What are the two ways in which muscle tissues can increase in size?
- Enlargement of their individual cells = hypertrophy
2. Multiplication of cell = hyperplasia
What does ANP stand for?
Atrial natriuretic peptide
What are natriuretic peptides?
Peptide hormones that are synthesised by the heart, brain and other organs.
What stimulates the release of natriuretic peptides by the heart?
Atrial and ventricular distension/swelling (in response to heart failure)
What are the main physiological actions of natriuretic peptides?
Reduce arterial pressure by decreasing blood volume and systemic vascular resistance.
When is ANP released?
When the heart is stretched
Where is ANP synthesised, stored and released?
Atrial myocytes
When are elevated levels of ANP found?
During hypervolemic states which occur in congestive heart failure
What does BNP stand for?
Brain-type natriuretic peptide
Where is BNP synthesised?
Ventricles (also brain)
What does NT-pro-BNP stand for?
N-terminal pro-BNP
BNP and NT-pro-BNP are sensitive diagnostic markers for which condition?
Heart failure
What role do natriuretic peptides play in the kidneys?
Promote the release of Na
Complete the sentence:
Natriuretic peptides serve as a counter-regulatory system for the _____-___________-___________ system
Renin-angiotensin-aldosterone
Purkinje fibres are large cells with what? (3)
- Abundant myoglobin
- Sparse myofilaments
- Extensive gap junction sites
What are smooth muscle cells shaped like?
Spindle-shaped (fusiform) with a central nucleus
True or false: smooth muscle contraction relies of actin-myosin interactions
TRUE
True or false: smooth muscle cells may remain contracted for hours or days
TRUE
Complete the sentence:
Smooth muscle often forms ___________ _____ of passageways or cavities
Contractile walls
Where can smooth muscle be found?
Gut
Respiratory tract
Genitourinary system
True or false: smooth muscle is voluntary
FALSE - involuntary
Which disorders can smooth muscle be of clinical significance in?
High BP (primary hypertension) Dysmenorrhea Asthma Atherosclerosis Abnormal gut mobility (IBS) Detrusor muscle instability
Which two types of cells can modified smooth muscle cells occur singly as?
Myoepithelial
Myofibroblast
Where can myoepithelial cells be found?
Form a basket work around secretory units of some exocrine glands (sweat, salivary and mammary glands). Also in ocular iris and they contract to dilate the pupil
Where can myofibroblasts be found?
Sites of wound healing and tooth eruption
Complete the sentence:
Most smooth muscle cells are innervated by __________ nervous system fibres that release their neurotransmitters from ____________ into a wide ___________ ______.
Autonomic
Varicosities
Synaptic cleft
True or false: skeletal muscle cells can divide
FALSE - cannot divide but tissue can regenerate by mitotic activity of satellite cells so hyperplasia follows muscle injury
What happens when cardiac muscle is damaged?
Cardiac muscle is incapable of regeneration and following damage, fibroblasts invade, divide and lay down scar tissue
True or false: smooth muscle cells retain their mitotic activity and can form new smooth muscle cells
TRUE
Where is the ability of smooth muscle cells being able to retain their mitotic activity evident?
In the pregnant uterus where the muscle wall becomes thicker by hypertrophy and by hyperplasia of individual cells