Muscle Tissue Flashcards
Sphincters are operated by what type of muscle?
Skeletal muscle
What is being described: Non-dividing cells surrounded by satellite cells and contained in a sarcolemma.
Muscle fibre
What are muscular satellite cells?
These arise from the myoblast cells that do not fuse to form myotubes. They remain as undifferentiated muscle stem cells/mesenchymal cells that can replace muscle fibres lost due to injury.
When a satellite cell is activated by injury, what happens?
The satellite cell undergoes asymmetric division - forming one satellite cell and one myoblast. The myoblast matures and fuses to the muscle fibre.
True or false: Skeletal muscle is striated
True,
True or false: Skeletal muscle is controlled by the autonomic nervous system
False, it requires somatic or voluntary input.
Fused myocytes/tubular cells formed from myoblasts form __1__ and are surrounded by __2___ (connective tissue around muscle cells). Bundles of 1 form muscle fascicle, surrounded by __3__. The __4__ covers all the fascicles.
1) Muscle fibres (cell)
2) Endomysium
3) Perimysium
4) Epimysium
What are the myofilaments inside a muscle fibre?
Thin: actin, tropomyosin, troponin Thick: myosin
Remember the muscle fibre is composed of many myofibrils and each myofibril which is also called a muscle cell is made up of myofilaments
What is a myofibril?
Any one of the contractile threads found in a muscle fibre.
What are transverse tubules (T-tubules) and what do they do?
‘Tunnels’ throughout muscle fibres that conduct action potentials from the sarcolemma to initiate contraction.
What is a sarcomere?
The smallest functional unit of muscle (not the smallest structural unit). Contraction happens here. Basically the area between 2 Z lines.
What forms the I band of the sarcomere?
Only thin bands of actin and it looks lighter because actin is isotropic/thin.
Think there’s only one Ishika
What forms the A bands of the sarcomere?
Thick bands of myosin (Anisotropic), overlapping with actin, therefore, appears dark.
Think A as in Alpa has 2 children
What is the Z line in the sarcomere?
Protein chain that supports the actin filaments (I bands). Z = zig zag
Remember Z at the end of the alphabet thus, at the end of the sarcomere
What is the M line in a sarcomere?
The middle line. (M for middle). Consists of proteins supporting the thick myosin filaments.
Where is the H zone on a sarcomere?
The central region that contains only myosin thick filaments.
Think, H for a house and only Maisuryas (Myosin) in the house
How is contraction achieved in the sarcomere?
Sliding of thick and thin filaments in the zone of overlap.
True or false: Striations can be found in cardiac muscle
True
Is cardiac muscle mononucleated or multinucleated?
Mononucleated. Cells are not fused.
Is skeletal muscle mononucleated or multinucleated?
Multinucleated. Myoblasts fuse together to form multinucleated fibres
Cardiac muscle contains intercalated discs at the ends of the cardiocytes. What structures are found here and why?
Gap junctions and desmosomes allow exchange of ions and molecules - allows spread of action potentials.
True or false: A sarcomere Z line appears zig zag shaped, and the M line appears straight
True z line = zig zag
True or false: cardiac muscle contraction is not reliant on the nervous system for stimulation.
True Pacemaker cells stimulate contractions; the nervous system can only alter the rate of activity.
True or false: Smooth muscle is incapable of regeneration
False. Smooth muscle cells can divide, therefore the tissue is capable of regeneration.
True or false: Cardiac muscle is incapable of regeneration
True
In which type of muscle will you NOT find sarcomeres?
Smooth muscle as it does not have striations
Describe the development of muscles.
- Myoblasts which are tiny cells combine together to form myotubes.
- Myotubes then form myofilaments/muscle fibres.
Describe skeletal muscle.
- Striated as it has actin and myosin as it is involved in moving and stabilising bones and needs to contract.
- Voluntary
- e.g. biceps
Describe cardiac muscle
- Only found in the heart
- Involuntary, because you don’t need to think about when your heart beats
- Striated because your heart needs to contract
Describe smooth muscle
- Found in walls of vessels and hollow organs e.g. stomach
- Non-striated as they don’t use actin and myosin to contract but their elastic walls and peristalsis.
What is the longest muscle in the body?
Sartorius (in leg- quads)
What is the smallest muscle in the body?
Stapedius
What is the biggest muscle in the body?
Gluteus maximum
What are the 2 attachments of the muscle?
Origin and Insertion
Origin is the attachment that moves ___1___ whilst the insertion is the attachment that moves ___2___.
- The least
- The most
How are skeletal muscles joined to the bones?
Via strong connective tissue called tendons
What are the 4 main functions of skeletal muscle?
- Movement
- Posture
- Support of soft tissues and stabilise joints
- Thermoregulation
Flat muscles are?
Have parallel fibres e.g. external oblique
(remember abs are flat and they are parallel)
Pennate muscles are?
Feather like e.g. deltoid
Fusiform muscles are?
Spindle-shaped with thick belly e.g. biceps brachii
Remember it is fussy so it eats what it likes and has a fat belly
Convergent muscles are?
Pectoralis major (converge from broad to single tendon)
Quadrate muscles are?
4 equal sides e.g. rectus abdominis
What is this structure? Label it
A) Blood vessels
B) Perimysium
C) Epimyisim
D) Muscle fibre
E) Fascicle (wrapped by perimysium)
F) Endomysium (between fibres)
G) Tendon
H) Bone
What is a prime mover? What is the difference between antagonist and synergist muscles?
- Prime mover - The muscle that has the major responsibility for a certain movement
- Antagonist - Muscle that opposes or reverses a prime mover
- Synergist - Muscle that aids a prime mover
What are type 1 muscle fibres?
- Known as slow-twitch oxidative
- Rich in blood supply
- low force but highly resistant to fatigue
- Aerobic respiration
- Red colour
What are type 2a fibres?
- Fast-twitch oxidative/glycolytic
- More force than type 1 but medium fatigue resistance
- Aerobic then anaerobic respiration
- White colour
What are type 2b muscle fibres?
- Fast-twitch fibres (glycolytic (breaks down glycogen))
- Anaerobic
- Lots of energy really quickly like when weightlifting but very low resistance to fatigue.
- White colour
What is an exception in the normal voluntary control of the skeletal muscle?
Respiratory movements such as the contraction of the diaphragm are automatic as well as the myotatic reflex (knee-jerk movement).
What is a tonic contraction?
This is a slight contraction of muscles even when relaxed, this provides the tone of muscles and maintenance of posture.
What is phasic contraction?
Two types
- Isotonic: muscle changes length in relationship to movement
- Isometric: Muscle remains the same length (isoMetric)
Where is smooth muscle found?
- Skin (controls the muscles of hair)
- Eyeball (controls pupils and lens)
- Cardiovascular system (blood vessels)
- Digestive system (stomach)
- Urinary system
Myositis is an __1___ inflammatory disease of the __2__, __3__, __4__ and __5__. Breathing and swallowing are affected. Primary treatment is DMARDs and steroids.
- Autoimmune
- Muscles
- Skin
- Lungs
- Heart
