Histology of Muscle Flashcards
What are the 3 types of muscle classification?
- striated (skeleton)
- cardiac
- smooth
Define Skeletal Muscle
- moves muscle attached to bone, voluntary & striated
Define Cardiac Muscle
- heart muscle, involuntary, striated, auto-rhythmicity
Define Smooth Muscle
- non-striated, involuntary, elements of auto-rhythmicity (peristalsis)
What are some basic muscle functions?
- body movement
- postural stabiltiy
- storage & movement of substances
- heat generation
What are some properties of muscular tissue?
- excitability
- contractility
- extensibility
- elasticity
Define excitability
- action potentials via innervartion of muscle
- triggered by autorhythmic nature of the heart & chemical stimuli via neutrotransmitters
Define Contractility
- generation of force as an output from an action potential
- contraction generates tension as the muscle pulls on its attachment points
Define Extensibility
- Stretch without being damaged, smooth muscle experiences this in the stomach as it fills
Define Elasticity
- ability to return to original shape & conformation following contraction of the muscle
What is the skeletal muscle organisation?
muscle = epimysium
fascicle = perimysium
muscle fibre = plasma membrane/sarcolemma
myofibril = sarcomere
myofilaments = actin & myosin
Describe the microscopic anatomy skeletal muscle
- diameter 10-100 um
- length - 10-30 cm
- multi-nucleated - myonuclear domain
- fibre number is set at birth
Define Sarcolemma
plasma membrane of the muscle cell
Define T-tubules
Invagination of the sarcolemma, involved in AP propagation
Define Sarcoplasm
cytoplasm of the muscle fibre
Define Myofibrils
- contractile machinery of muscle,
- 2mM in diameter, comprised of actin & myosin
Define the Sarcoplasmic Reticulum
- network of ER
- specialised for skeletal muscle in Ca2+ handling
Describe a sarcomere
- each myofibril has a striated pattern = sarcomere
- repeating unit between two Z discs
- ends of actin filaments are attached to a Z disc
- thick & thin filaments - compartmentalised into a sarcomere
- length of sarcomere change upon contraction
Describe Skeletal Muscle Histology
- stripy appearance - striations
- repeating structure of muscle
- repeating unit = sarcomere
- light stripe ‘Z’ lines & darker ‘A’ bands
- sarcomere is the repeating unit between two Z-lines
What are the components of the sarcomere ?
- contractile proteins = actin & myosin
- regulatory proteins = troponin & tropomyosin
- structural proteins = alpha-actinin, Titin, myomesin
What are some functions of smooth muscle ?
- vascular tone
- peristalsis
- pupil constriction/dilation
What is general structure of smooth muscle?
- single, centrally placed nucleus
- spindle (fusiform) shape
- non-striated
Describe Multi-unit smooth muscle
- control mainly by nerve signals
- each fibre can contract independently of others
- examples = ciliary muscle & iris muscle of eye
Describe Unitary Smooth Muscle
- cell membrane joined by many gap junctions
- ions to flow easily from 1 muscle cell to the next
- action potential can travel from one fibre to the next, allowing fibres to contract together
- found in walls of most viscera of body; GI tract, bile ducts, uterus
Describe cardiac muscle
- fibres arranged in latticework
- fibres dividing, recombining & spreading
- striated appearance
- myofibrils contain actin & myosin
- dark areas crossing cardiac muscle fibres = intercalated discs
Describe Intercalated discs
- cell membranes that separate individual cardiac muscle cells
- at each disc cell membranes fuse together
- permeable ‘communicating’ junction formed
- gap junctions = allow rapid diffusion of ions
