Muscle Tissue Flashcards
What are muscles specialised for?
contraction
What are the types of muscle tissue and what is their role?
skeletal - movement of body
cardiac - movement of blood
smooth - movement of gases, fluids and solid through visceral organs
How is skeletal muscle classified?
somatic (voluntary) & striated
How is cardiac muscle classified?
autonomic (involuntary) & striated
How is smooth muscle classified?
autonomic (involuntary) & non striated
What is a striated appearance?
banded
What is the name of the outer connective tissue that encases entire muscles?
epimysium
What is the name given to the connective tissue layer that surrounds bundles of muscle fibres, known as fascicles?
perimysium
What is the name given to the connective tissue layer that surrounds individual skeletal muscle fibres?
endomysium
What name is given to the structure formed by the coming together of the 3 connective tissue layers in skeletal muscle, at the tapering ends?
tendon
What is each skeletal cell packed full of?
myofibrils which create the striated appearance
What are myofibrils made from?
repeating proteins units called myofilaments made from actin and myosin
What are the dark bands in electron-microscopy?
myosin
What are the light bands in electron-microscopy?
actin
What are the contractual units called?
sarcomeres
How do they contractual units contract?
actin and myosin slide over each other, overlapping due to a conformational change in the sarcomere
Describe which organelles are specialized for skeletal muscle
plasma membrane called sacrolemma
cytoplasm called the sacroplasm
sarcoplasmic reticulum
multinucleated
What a motor unit?
A single motor neurone together with all the muscle fibres it innervates
What is the process of muscle contraction called?
Excitation-Contraction coupling
What is the chemical messenger converted from neuronal action potential that simulates the action potential in skeletal muscle cells?
acetylcholine
What structural feature of skeletal muscle fibres propagates action potentials into the interior of the cell?
T tubules
What happens at the action potential?
When the muscle is stimulated, calcium ions are released from its store inside the sarcoplasmic reticulum, into the sarcoplasm (muscle )
What structural feature of skeletal muscle fibres sequesters calcium away from myofibrils during relaxation?
sarcoplasmic reticulum
What is the function of cardiac muscle?
Specialized for continuous autonomous contractions
Pump blood through the cardiovascular system
What is the structure of cardiac muscle?
elongated, branched cylindrical cells
1 or 2 centrally located nuclei
similar arrangement of contractile proteins as in skeletal muscle causing striated appearance
What are the layers of cardiac muscle?
Pericardium (P): Outer supporting tissue layer
Myocardium (M): Cardiac muscle tissue
Endocardium (E): Single layer of endothelial cells
What do the intercalated discs at the end of cardiomyocytes contain?
desmosomes, gap junction
What are the cells of cardiac muscle?
cardiomyocytes
What are the similarities between cardiac and skeletal muscle?
identical arrangement of sacromeres
both have t tubules and sarcoplasmic reticulum
contraction happens by sliding -filament mechanism
What are the differences between cardiac and skeletal muscle?
In cardiac muscle cells the SR slowly leaks Ca so that the heart can generate its own action potential instead of only releasing at an action potential
no motor neuron needed in cardiac muscles as single travels through gap junctions at the end of intercalated discs
All cells in cardiac muscle work as a single unit, what is this called?
syncytium
What is a ‘conducting system’?
The conducting system is a group of cells that can initiate the contractions without any outside stimulus
What can undergo spontaneous depolarisation?
pacemaker cells
Describe the conducting system of cardiac muscle
Signal to contract will travel from sinotrial node (pacemaker cells) to atrioventricular node
– this movement will trigger the atria to contract and push blood from atria to the ventricles.
- from the node the signal to contract will travel to the bundle of his to the purkinje fibres where they reveal that signal to the cardiac muscle cells
Where is smooth muscle found?
lining hollow organs
What is the structure of smooth muscle?
Elongated, spindle-shaped cells with tapered ends
Single centrally located nuclei
No sarcomeres hence no striations
What is peristalsis?
Peristalsis is a wave of contraction in the gastrointestinal tract followed by relaxation
What only exists in smooth muscle?
desmin
What does the smooth muscle look like contracted?
globalar
What does the smooth muscle look like relaxed?
elongated
What does the smooth muscle not have?
no myofibrils or sarcomeres
What is the adventitia referred to in the abdominal cavity?
serosa
What name is given to the innermost layer (luminal surface) that is composed predominantly of epithelium in the intestine?
mucosa
Name the section directly beneath the mucosa
submucosa
Name the section directly beneath the submucosa
muscularis propria
Name the section directly beneath the muscularis propria
serosa
What are mucus-secreting cells called?
goblet cells
How many nuclei does smooth muscle have?
one
What is the position of the nuclei in cardiac muscle cells?
Central
What is the zigzag portion called that forms the boundary ends of each sarcomere?
z line
What are the thick filaments in sarcomeres?
myosin
What are the thin filaments in sarcomeres?
actin
What do T tubules do?
they also transmission of the action potential across the sarcoplasm
Where is calcium concentrated?
sarcoplasmic reticulum
What is the M line?
the middle of the sarcomere
What is the I line?
where actin filaments are (no overlapping)
Why are intercalated discs present in cardiac muscle?
for rapid transmission of stimuli between cells and points of anchoring
How are actin and myosin arranged in smooth muscle?
criss-cross lattice
In smooth muscle, calcium binds to what molecule to create contraction?
calmodulin
What is the band that contains only myosin filaments?
H band
What is the band where myosin and actin filaments overlap?
A band
