Muscles Flashcards
What are the 3 types of muscle?
-Skeletal
-Cardiac
-Smooth
Functions of the muscular system (i.e., of all 3 types of muscle)?
-Locomotion (movement)
-Posture maintenance & muscle tone
-Heat generation
-Joint Stability
-Vasoconstriction & vasodilatation
-Peristalsis
-Cardiac motion/contractility
Features of muscles x5 - & which of the 3 types of muscles they are in?
*Striation - only skeletal & cardiac (NOT smooth)
*Nucleus - smooth & cardiac = uni-nucleated (cardiac can be bi-nucleated)
skeletal = multinucleated
*Transverse/T tubules - only in skeletal & cardiac (NOT smooth)
*Intercalated disk - only in cardiac
*Control - skeletal = voluntary
smooth & cardiac = involuntary (autonomic NS)
Role of T tubules?
Transport Ca2+
What are intercalated disks (only cardiac)?
Specialised intercellular junctions
Fact relating to skeletal muscle shape?
Every skeletal muscle has a unique shape that determines its function
Describe the structure of skeletal muscle - components, layers - order of these?
1 - Muscle = EPIMYSIUM covering
2 - Fascicle (bundle of muscle fibres) = PERIMYSIUM covering
3 - One muscle fibre (from a fascicle) = ENDOMYSIUM covering
4 - One Myofibrils (from muscle fibre)
5 - Myofilaments (actin & myosin) - within sarcomeres
What is epimysium?
-CT sheath - dense irregular CT
-Overcoat surrounding whole muscle
What is perimysium?
-CT sheath - dense irregular CT
-Surrounds fascicles (groups of muscle fibres)
-Fine sheets of fibrocollagenous support tissue
What is endomysium?
-CT sheath
-Surrounds each individual muscle fibre
How do epimysium, perimysium, endomysium link?
Continuous with each another & with tendons joining muscles to bones
Structure of skeletal muscle?
-Nuclei @ periphery = purple dots (basophilic)
-Nuclei beneath cell memb
-Striations
-Multinucleated
-Fibrocollagenous septa (separates muscle fibres) contains blood vs (skeletal muscle NEEDS blood)
-Muscle cells = pink (eosinophilic as shows cytoplasm)
-Hexagonal shaped muscle cells
What view of skeletal muscle is this & why?
Cross-sectional/transverse/horizontal view
–> as can see:
-Hexagonal muscle cells
-Peripheral nuclei
-Multinucleated
-Fibrocollagenous septa
What view of skeletal muscle is this & why?
Longitudinal/vertical view
-Peripheral nuclei
-Multinucleated
-Striations
How to identify from a histological image, what type of muscle something is?
-No. nuclei per muscle cell - uni/bi/multi
-Where are nuclei - periphery/central?
-Striations?
What causes the striations seen in skeletal (& cardiac) muscle?
Repeating dark (A) bands & light (I) bands - along length of each myofibril
What are dArk bands in muscles?
A bands = actin & myosin overlap
What are lIght bands in muscles?
I bands = actin only
Actin & myosin - which is the thick & which is the thin filament?
-Actin = thin myofilament
-Myosin = thick myofilament
What are on the boundaries of a sarcomere?
Between 2 successive Z discs = a sarcomere
What is the H zone?
-Only myosin
-Bisected vertically by a dark line called The M line (M for middle)
Label.
Label.
What would cross-sectional views of a sarcomere cut at different locations show for:
-I band
-H zone
-M line
-A band
Describe the motor end plate - process.
-Sarcoplasmic memb in mot endplate conatins recs which are activated
–> causing release of ACh (for muscle depolarisation to occur) - exocytosis - out of vesicles/storage granules in presynaptic neurone
-ACh diffuses across synaptic cleft
-ACh binds to special memb recs (nicotinic recs) on muscle fibre = initiates contraction
-AChE breaks down/hydrolyses ACh in synaptic cleft = acetic acid + choline
-Nerve fibres controlling voluntary movement, specialised motor axons - innervate fibres in muscle spindle
What is myasthenia gravis?
-Autoimmune disease
-Antibodies produced by own imm syst bind to ACh recs - prevents ACh interacting w/ recs = NO depolarisation!!!
–> so nerve impulses not transmitted effectively to muscle
-Causes - muscle weakness - muscle fatigue, can’t lift arms, can’t maintain upright posture of head, eyelid drooping
What is Duchenne Muscular Dystrophy (DMD)?
-Genetic disorder = caused by deficient dystrophin gene (produces dystrophin prot - memb-assoc cytoskeletal prot)
-Gene = on short arm of X chromosome = Xp21
-Linked to cytoplasmic side of sarcolemma of muscle fibre
-Rapid degeneration of skeletal muscle
-Mainly boys effected
-Shortened life expectancy
-Muscle weakness, muscle wasting, heart problems, Gower’s sign, hypertrophic calf muscles - progresses w/ age
Histopathology of DMD?
Lack of dystrophin protein causes:
-Damage to skeletal muscle memb –> then cell death of muscle fibres (eosinophilic - pink)
-Dead muscle fibres replaced by adipose/fat cells (white)
What view of cardiac muscle is this?
Longitudinal view
What view of cardiac muscle is this?
Cross-sectional/transverse/horizontal view
Where are the intercalated disks in the longitudinal image here?
What view of smooth muscle is on the left & right?
-Left = longitudinal view
-Right = cross-section/transverse view
What view of smooth muscle is this?
Longitudinal view
Complete this summary.
-Satellite cells = myogenic SCs repair damaged muscle cells
-Heart - cardiac muscle cannot regenerate to replace damaged cells!
