Muscle Flashcards
How is force produced
Produced by movement of actin fibres over myosin fibres
With aid of a number of accessory proteins
What are the four muscle cell types
Skeletal/voluntary Cardiac Smooth invol Myoepthelial Myofibroblasts Pericytes
What are the non contractile cells in muscle
Myofibroblasts
Myoepthelial
Pericytes
What is myoepthelial
Found associated with the secretory units of some exocrine glands
They are flattened cells and hve contractile protein arrangement similar to smooth muscle
What are myofibroblasts
Characteristic of both fibroblasts (secrete collagen) and smooth muscle cells
Normally few in number and inconspicuous they enlarge and prolif in injury
Collagen for scaffold for repair they contract the wound
What are pericytes
Inconspicuous cells found in around capillaries and venules
Act as stem cells but also contractile
What is skeletal muscle
Skeletal
Voluntary
Straited
What is muscle tissue
Formed from muscle cells and associated connective tissue and forms nulk of muscles
What are the features of skeletal muscle
Striated Unbranched Multinucleate Fibres long cyclinders Nuclei at periphery sarcolemma
What are fascicles
Muscle fibres are grouped into bundles called fascicles
What are the different types of connective tissue associated with skeletal muscle organisation
Ct around muscle as a whole - epimysium
Ct around single fascicle - perimysium
Ct around single muscle fibre - endomysium
What are sarcomeres
Unit of contraction of muscle cell smallest contractile element
Hundreds arranged end to end form myofibril
What does striated mean
Fibres have a regular pattern bands running across
True for cardiac muscle
What is a motor unit
Motor neurone and all the muscle fibres that it innervates
What does a motor neurone end in
A motor end plate
What happens at the motor end plate
Neuromuscular junction where there is a synapse where the action of acetylcholine occurs and initiates an action potentioa in the sarcolemma
What are T-tubules
Within muscle fo the cell network of tubules
Extend from sarcolemma into cell surrounding myofibril
What is the sarcoplasmic reticulum
Muscle cell contains labyrinth of specialised cells sarcoplasmic reticulum
Contains very high conc of calcium
What is a triad
T tubule with sarcoplasmic reticulum form triad
What is the stimulus leading to contraction
Action potential arrives at neuromuscular junction acetylcholine released results in action potential in muscle cell
Muscle action potential travels along sarcolemma and invades t tubules at triads release calcium lead to action on myosin fibres shortening sarcomeres and contraction
What are the three types of skeletal muscle fibre
Type 1 - relatively slow contracting fibres that depend on oxidative metabolism, abundant mitochondria resist fatigue and produce relatively less force red fibres
Type 2A - intermediate between other two and these fibres relatively uncommon
Type 2B - relatively fast connecting fibres that depend on anaerobic metabolism, few mitochondria, fatigue easily and produced greater force called white fibres
What su the myotendinous junction
Specialised junction where collagen fibres of tendon attaches to end of muscle fibres
Here muscle fibres tightly anchored to collagen by complex interdigitations
How is feedback referred
Muscle has special sense organs
Muscle spindle contain special muscle fibres referred to as intrafusal fibres
Normal contractile muscle fibres termed as extrafusal fibres
What su smooth muscle
Involuntary or visceral
No striations
What is focal densities
Actin and myosin fibres do not go instant ions or organised like so but do converge on focal densities T periphery of cell
What is cardiac muscle
Forms major part of walls of heart etc Skeletal muscle, cardiac muscle has striations less prominent Fibres much shorter Single nucleus near centre of fibre Intercalated discs
What is a dyad
In cardiac muscle t tubule and sarcoplasmic reticulum
What are cardiac myocytes
Intrinsic rhythmic contraction
Gap junctions in intercalated discs allow for synchronisation of contraction between cells and allow wave of excitation to sweep through tissue
Rhythm independant of autonomic nervous system but modulated by it
What are satellite cells
Skeletal muscle retains population of myoblasts which are satellite cells
Small quiescent cells pressed to sides of sarcolemma under nasal lamina
Form new muscle fibres
How are cells specialised for contractile force
All cells contain contractile fibres in cytoskeleton
In muscle cells the cytoplasm packed with such fibres and cells highly specialised for contraction force
