Muscle Tissue Flashcards
What are muscle tissues specialised for? (3)
Moment of body by skeleton.
Movement of blood by cardiac.
Movement of gases, fluids, solids through hollow organs by smooth muscle.
What is voluntary muscle control?
Mediated by somatic motor via motor neurons
Ie. Send signals to muscles from brain telling them to contract
What is involuntary muscle control?
Unconscious
Regulates heart breathing etc.
What type of cells have voluntary muscle control?
Somatic
What system involuntary muscle control?
Autonomic
Describe the classification of skeletal muscle cells?
Somatic, voluntary, striated
Describe the classification of cardiac muscle cells?
Autonomic, involuntary, striated
Describe the classification of smooth muscle cells?
Autonomic, involuntary, non striated
What is the function of smooth muscle cells?
Propel contents of organs through the organ
Where are smooth muscle cells found?
Line hollow organs
What are skeletal muscle cells specialised for?
Contractions that produce movement
What do skeletal muscle cells do and where are they found?
Attacked to skeleton
Voluntary movement of skeleton
Subconscious movement of balance and posture
What are skeletal cells mediated by?
Somatic branch of nervous system.
Describe structure of skeletal muscle fibres.
- Elongated, cylindrical cells
- Multiple peripherally located nuclei under plasma membrane
What are skeletal muscle fibres packed full of?
packed full of myofibrils which contains repeating units of myofilaments
What is an individual skeletal muscle composed of?
Skeletal muscle tissue
Nervous tissue
Blood vessels
Connective tissues
How are muscle fibres arranged?
In fascicles composed of skeletal muscle cells
Encased in endomysium - innermost later of connective tissue
What are individual muscle fibres separated by?
Endomysium
How are muscle fibres grouped together?
Fasciculi
What is the perimysium?
Each fascicle surrounded by loose connective tissue.
What is the epimysium?
Dense connective tissue that externally surrounds the entire fascicle.
What are tendons formed of?
Endomysium, perimysium, and epimysium blend together at tapered ends.
What do tendons do?
Have a strong attachment to bone that helps to transfer force of contraction to bone.
What gives rise to the striated appearance in skeletal cells?
Repeating Myofibrils arranged parallel
What forms the cytoskeleton of all cells?
Actin and myosin
What is the difference between actin and myosin?
Actin is a thinner filament (light band)
Myosin thicker filament (dark band)
What are Z lines?
Light bands of actin bisected by dark lines
Anchors actin
How do skeletal muscles contract?
The sarcomeres contract by the sliding filament mechanism.
What causes the sliding filament mechanism?
Conformational change causes the filaments to slide over each other causing the sarcomere to shorten
What does it mean by “somatic motor neurons innervate skeletal muscle”
Tell them to contact.
What makes a motor unit?
A motor neuron and muscle fibres
What happens at the neuromuscular junction?
The neuronal action potential is converted to chemical messenger (acetylcholine)
This is detected by receptors on muscle fibres
Stimulating action potential in muscle fibres
What is excitation contraction coupling?
Signal detected by receptors in plasma membrane of muscle cell
Stimulates action potential
Causes contraction
Name to adaptations of skeletal muscle cells?
Sarcolemma and sarcoplasmic reticulum
What do adaptations of muscle cells do?
Help distribute and coordinate signals required to initiate contraction.
Describe features of the sarcolemma?
- plasma membrane of skeletal muscle cells
- modified to contain pores that connect directly to T tubules
(Wraps around myofibrils and interacts directly with sarcoplasmic reticulum.
What is the sarcoplasmic reticulum?
- modified from of SER
- calcium is concentrated when muscle cell is relaxed
- calcium required for actin to interact with myosin
Interacts with t tubules and wraps around myofibrils
What happens when calcium is released from the sarcoplasmic reticulum?
Actin slides across myosin stimulating contraction
What do you do when you don’t want cell to contract from release of calcium?
Calcium is sequestered away from myofibrils within sarcoplasmic reticulum.
What is the function of cardiac muscle cells?
Only found in heart
Pump blood through cardiovascular system
Specialised for continuous autonomous contractions
Describe the structure of a cardiac muscle cell?
-elongated and branched cylindrical cells
- striated
- one or two cent really located nuclei
What is the heart encased in?
Pericardium - layer of tough fibrous connective tissue
What is the myocardium?
Thick layer where cardiac muscle tissue is located.
What is the endocardium?
Single layer of endothelial cells
- simple squamous lining
What is a cardiomyocyte?
Individual cardiac muscle cell
What does the reticular connective tissue support in cardiac cells?
Rich capillary network
What do intercalated discs do?
Anchor cardiac cells together
What do intercalated discs contain?
Desmosomes
Gap junctions
Where are intercalated discs found?
Adjoining end of cardiac muscle cells
Describe the similarities between skeletal muscle cells and cardiac muscle cells?
Identical arrangement of sarcomeres
Contain t tubules and sarcoplasmic reticulum
Both have numerous mitochondria
Have stores of glycogen and lipid granules
Contract by sliding filament mechanism
What are the differences between cardiac muscle cells and skeletal muscle cells?
Skeletal has voluntary and cardiac has autonomous contraction
skeletal the sarcoplasmic reticulum sequesters all the calcium away from myofibrils until they recieved the depolarisation signal —— in cardiac muscle tissue the SR slowly leaks calcium for heart to generate own action potentials
Why are specialised cardiac muscle cells known as conducting system?
Important in initiating and coordinating action potentials that generate cardiac contractions
What is a syncytium made up of?
Intercalated discs, gap junctions and desmosomes working together to allow cardiac muscle cells to be a single unit.
Where are pacemaker cells found?
Sinoatrial node
Where is the cardiac muscles autonomous contraction initiated?
Sinoatrial node (pace maker cells)
What happens when pacemaker cells undergo spontaneous depolarisation?
Sets basic heart rhythm.
Signal to contract then travels to atrioventricular node which triggers the atria to contract
Pushes blood out and into aorta
What makes pace maker cells undergo spontaneous depolarisation.
Happens due to slow leaking calcium from sarcoplasmic reticulum
What is the function of smooth muscle cells?
Found lining hollow organs
Specialised for continuous contraction
Peristalsis- to propel lumen contents
What is peristalsis?
Wave of contraction in GIT followed by relaxation
Waves move along lumen to move contents forward
What is the structure of smooth muscle cells?
Elongated spindle shaped cells with tapered ends
Single centrally located nuclei
No sarcomeres hence no striations
What are the layers like in the GIT?
Entire GIT lined internally by epithelium
2 muscle layers
Inner layer is epithelial cells (mucosa)
Under this is connective tissue (submucosa)
What surrounds the sub mucosa?
2 layers of smooth muscle (muscularis propria)
What is the orientation of layers in smooth muscle and why is it important?
Inner layer = circular
Outer layer = longitudinal
Orientation produces waves of contraction to push contents of lumen along.
What does the inner circular layer of the GIT do?
Constructs lumen diameter
What does the outer longitudinal layer of the GIT do?
Shortens length
What modulates the intensity of peristalsis?
Parasympathetic nervous system
What is the parasympathetic ganglia?
Between outer and inner layer of GIT
Has parasympathetic nerve cell bodies that regulate and control intensity of peristalsis contraction
What does smooth muscle cells not contain?
No t tubules
No myofibrils therefor no sarcomeres
How does the sarcoplasmic reticulum differ in smooth muscle cells?
Forms loose network throughout cells as no myofibrils to interact with
This is why muscle cells appear nonstriated
How are actin and myosin arranged in smooth muscle cells and what are they important for?
Crisscross lattice
- generate contractile ability of cells by sliding over each other
How is smooth muscle cell anchored to cytoplasm and cell membrane?
Dense bodies
What are actin and myosin attached to in smooth muscle cells?
Actin attached to dense bodies which attach to sarcolemma and bind muscle cells together
Myosin distributed around cytoplasm
When a contraction occurs in a smooth muscle cell what is the 3rd filament?
Desmin
What shape do smooth muscle cells adapt when contraction happens?
Globular structure
What type of muscle cell uses the least energy during contraction?
Smooth muscle cells
