9 - Muscle Tissue Flashcards
What is myalgia?
Muscle pain
What is myasthenia?
Muscle weakness
What is myoclonus?
Muscle spasm
What is a sarcosome?
A mitochondrion of a muscle cell
What is myoglobin?
- Oxygen carrier protein similar to a single haemoglobin subunit
- Haemoglobin gives up oxygen to myoglobin in the muscle (especially at low pH - e.g. during exercise)
Which forms of muscle are striated?
Skeletal muscle
Cardiac muscle
Which forms of muscle contain myoglobin?
Skeletal muscle
Cardiac muscle
Which forms of muscle are under involuntary control?
Cardiac muscle
Smooth muscle
What is the cellular structural unit of striated muscle known as? Describe the ultrastructure of striated muscle.
Sarcomere
- Interlocking thin filaments (actin) and thick filaments (myosin)
- Actin filaments join at the Z disc
- Myosin filaments join at the M line
What 3 bands are seen in a sarcomere?
I band - only actin (contains the Z disc)
H band - only myosin (contains the M line)
A band - where actin and myosin overlap
Outline the mechanism of the sliding filament model of contraction.
- Myosin binds to actin (ADP + Pi bound)
- Power stroke (ADP + Pi released)
- Cross-bridge detaches (ATP binds)
- Myosin head prepares to reattach (ATP hydrolysed)
Each muscle cell (fibre) contains numerous …………………, fibres are multinucleated and are surrounded by plasma membrane (……………..)
Myofibrils
Sarcolemma
Muscle fibres are grouped into ………..
Fascicles
What 3 connective tissues are found within a muscle? Where is each one found?
Endomysium - lies between muscle fibres
Perimysium - wrapped around fascicles
Epimysium - surrounds the whole muscle
The point of origin of a muscle is where ………… is generated, the point of insertion of a muscle is where …………… is generated
Origin - tension
Insertion - movement
What is hypertrophy?
Increase in tissue size by enlargement of the cells
What is hyperplasia?
Increase in tissue size by multiplication of the cells (increase cell number)
Describe the repair mechanisms possible in skeletal muscle.
- Cells are unable to divide
- Regenerate by mitosis of satellite cells (hyperplasia)
- These can also fuse with existing cells to increase mass (hypertrophy)
Describe the repair mechanisms possible in cardiac muscle.
- Incapable of repair
- Fibroblasts invade, divide and lay down scar tissue
Describe the repair mechanisms possible in smooth muscle.
- Retain mitotic activity and can form new cells
- Particularly in pregnant uterus - becomes thicker by both hypertrophy and hyperplasia
What are the 3 different types of muscle fibre? How do their metabolic pathways for generating energy differ?
Type 1 (slow twitch) - oxidative Type 2A (fast twitch) - oxidative/glycolytic Type 2B (fast twitch) - glycolytic
How do the 3 types of muscle fibre differ in terms of number of mitochondria?
Type 1 (slow twitch) - many mitochondria Type 2A (fast twitch) - intermediate no. Type 2B (fast twitch) - few mitochondria
How do the 3 types of muscle fibre differ in colour?
Type 1 (slow twitch) - red Type 2A (fast twitch) - red-pink Type 2B (fast twitch) - white
How do the 3 types of muscle fibre differ in time to fatigue?
Type 1 (slow twitch) - fatigue resistant Type 2A (fast twitch) - moderate fatigue resistance Type 2B (fast twitch) - rapidly fatigue
How do the 3 types of muscle fibre differ in the type of activity they are used in?
Type 1 (slow twitch) - endurance/stamina Type 2A (fast twitch) - assists both 1 and 2B Type 2B (fast twitch) - strength/anaerobic
How do the 3 types of muscle fibre differ in source of energy?
Type 1 (slow twitch) - fatty acids Type 2A (fast twitch) - fatty acids and glycogen Type 2B (fast twitch) - glycogen
Cardiomyocytes communicate through …. ………… at their intercalated discs
Gap junctions
Where are Purkinje fibres found? What is their role?
In the heart, starting at the atrioventricular node as the bundle of His and branching down the ventricular septum into the ventricular wall
Rapid conduction of action potentials to enable the ventricles to conduct synchronously
Purkinje fibres are large cells containing lots of g…………., very few m………………. and many ……. junctions for electrical conduction
glycogen
myofibrils
gap
Smooth muscle cell contraction is ………. and requires less energy from ……..
They can remain contracted for ….. to …….
slower, ATP
hours, days
Smooth muscle membrane contains numerous …………. (cave-like invaginations).
What do these do?
Caveolae
Formed from caveolin proteins to sample the external environment so the cell can respond appropriately.
What does smooth muscle do (i.e. where is it distributed)?
What is the clinical significance of this?
Forms the contractile walls of passageways and cavities to modify the volume (e.g. vasculature, gut, respiratory and urinary tracts)
Can be involved in disorders such as high blood pressure, asthma, IBS, incontinence etc.
ANS fibres supplying smooth muscle release their neurotransmitters from …………… instead of having T tubules on the muscle membrane
Varicosities
