Structure Of Muscles Flashcards
How is muscle attached to bones?
Tendons
What supports nerves and capillaries in muscles?
Extensive connective tissue
What are muscle fibre bundles known as?
Fascicles - wrapped in Perimysium
What layers are there in muscle fibres?
Epimysium
Perimysium
Fascicles
Endomysium
What is Epimysium?
Dense collagenous sheath
Surrounds gross muscle
What is Perimysium?
Loose collagenous connective tissue
Surrounds fascicle
What’s Endomysium?
Separates muscle fibres
What’s a fascicle?
A group of elongated bundles of muscle fibres
What’s each muscle fibre surrounded by?
Endomysium
What forms gross muscle?
Fascicles coming together
What do tendons do?
Transmit force generated by muscle to bones
Stain used for muscles:
Haemotoxylin and Eosin (H&E)
What type of dye is haemotoxylin?
Basic
Stains purple/blue
WHat type of dye is Eosin?
Acidic
Red/pink
Why may there be white areas on histology stain?
Connective tissue that has been dehydrated while creating slides
Nuclei in skeletal muscle:
Multinucleated
What does skeletal muscle fibre as contain a lot of?
Mitochondria
What special structures does skeletal muscle fibres contain?
Transverse tubules (T tubules)
What repeating structure does skeletal muscle fibres have?
Sacromeres and myofibrils
Intracellular structures in muscle:
Sarcolemma
Sarcoplasm
Sarcoplasmic reticulum
What’s sarcolemma equivalent to?
Plasma membrane
What’s sarcoplasm equivalent to?
Cytoplasm
What’s sarcoplasmic reticulum equivalent to?
Smooth ER
What’s control is skeletal muscle under?
Voluntary and reflexive control
What are characteristic features of skeletal muscle fibres in longitudinal section?
Elongated, unbranded, cylindrical cells
Many flattened nuclei beneath sarcolemma
What bands make up striations in skeletal muscle fibres?
I and A bands
What are I bands?
Light colour in stain
Isotropic
What do I bands contain?
Actin - light filaments
What are A bands?
Dark colour in stain
Anisotropic bands
What do A bands contain?
Myosin - heavy filaments
What bisects I bands?
Z lines
Where is the nucleus found in skeletalmuscle fibres?
Periphery of cell
What does sarcoplasm in skeletal muscle contain?
Myofibrils and mitochondria
How are myofibrils oriented in sarcoplasm of skeletal muscle?
Parallel to long axis of cell
How are mitochondria oriented in sarcoplasm of skeletal muscle?
Rows
Parallel to long axis of cell
What are Z bands?
Electron-dense
Bisect I bands
What do Z lines do?
Divide each myofibril into sacromeres (contractile units)
What’;s found in the spaces between myofibrils in skeletal muscle?
Sarcoplasmic reticulum
What are tubules in sarcoplasmic reticulum of skeletal muscle important for?
Conducting electrical signal into centre of muscle fibre
Nuclei in cardiac muscle cells:
One nuclei in centre of each cell
Characteristics of cardiac muscle:
Striated
Gap junctions
Desmosomes
Intercalated discs
What mechanism does cardiac muscle use to contract?
Sliding filament mechanism
Role of desmosomes in cardiac muscle:
Mechanical connection between cells
Role of gap junctions in cardiac muscle:
Electrical connection between cells
Role of intercalated discs in cardiac muscle:
Mechanical and electrophysiological coupling
Why are gap junctions critical in cardiac muscle?
To allow heart to be electrically coupled
What other cells are found in cardiac muscle?
Nodal cells
What do nodal cells do?
Stimulate action potentials
Absolute refractory period in cardiac muscle:
250ms
What can tetanic contractions cause?
Interference of heart’s ability to pump
What are gap junctions constructed from?
Hexagonal array of protein subunits - connexins
What do gap junctions act as in cardiac muscle?
Communicating channels - connexon
What molecules pass through gap junctions?
Small molecules (Ions and glucose size)
What do gap junctions link?
Adjacent myocytes
What pathway do gap junctions provide?
Direct electrical and chemical communications
How can you measure current through gap junctions?
Whole-cell patch clamp
What does smooth muscle contain?
Actin and myosin filaments
What doesn’t smooth muscle have?
Z discs
No visible striations
How are acting and myosin filaments aligned in smooth muscle?
Along long axis of cells
How are filaments anchored in smooth muscle?
At dense bodies in sarcoplasm
What do dense bodies in smooth muscles contain?
a-actinin
How are contractile arrays anchored in smooth muscle?
To sarcolemma by dense plaques
What are smooth muscle cells connected by?
Focal adhesions (adherens junctions)
Shape of smooth muscle cells:
Elongated and spindle-shaped
What are the ends of smooth muscle cells like?
Tapered - occasionally bifurcated (divided into two branches)
Smooth muscle cells compared to skeletal muscle cells:
Shorter
Only one nucleus - located and central
How are individual smooth muscle fibres arranged?
Roughly parallel to each other
Why are smooth/visceral muscle cells unstriated?
Contractile proteins not arranged in myofibrils
Type of control in smooth muscle:
Involuntary and autonomic innervation
What are smooth muscle fibres surrounded by?
Network of collagen
Mechanism of contraction in smooth muscle cells:
Different to skeletal and cardiac
Shorten and broaden
What do smooth muscle fibres surround?
Blood vessels
GI tract
Bronchial airways
