BL- Muscle Tissue strcuture, function and dysfunction Flashcards
What is myasthenia
Weaknes of muscles
What is the myocardium
Muscular component of the heart
What is myopathy
Any diseases of the muscles
What is myoclonus
A sudden spasm of the muscles
Skeletal muscle
Myoglobin present
Voluntary control
Striated
Direct nerve to nurse communication
Cardiac muscle
Myoglobin present
Striated
Involuntary control
Indirect nerve-muscle communication
Smooth muscle
No myoglobin
Involuntary control
No direct nerve-muscle communication
What is myoglobin?
A red protein similar in structure to haemoglobin
It provides oxygen to working striated muscle
Haemoglobin gives up oxygen to myoglobin at low pH
What does myoglobin in the blood indicate
That striated muscle has died-muscle necrosis
This is because myoglobin is released into the bloodstream and into the urine
Can causerenal damage
What is the sarcolemma Sarcplamsm Sarcosome Sarcomere Sarcoplasmic reticulum
- outer membrane of muscle cells
- cytoplasm of a muscle cell
- Mitochondrion
- contraction unit in striated muscle
- smooth endoplasmic reticulum of a muscle cell
What causes movement in skeletal muscle
When the point of origin and the point of insertion of a muscle cross a joint
Movement is dependant on direction of muscle fibre
Tension is created at the origin tendon point
Movement is created at the insertion tendon point
What is a myofibroblasts
Contractile unit that sits within the single cell
Where are the nuclei in skeletal muscle
Peripheral
What are the here types of muscle contraction speeds
Slow fast intermediate
Each fasciae has at lease one of each
Intermediate sometimes classed as fast twitch
What causes the red colour in sow twitch fibres
Myoglobin and cytochrome
What colour are fast twitch fibres
White
What is endomysium
Perimysium
Epimysium
Group myofibrils
Group fascicles
Group muscles
Where is the nucleus positioned in cardiac cells
In the centre
What is hypertrophic
Enlargement of their individual cells
What is hyperplasia
Multiplication of their cells
What is atrophy/ hypertrophy
Cells gets smaller/bigger
What is the sarcomere like in cardiac cells and what is the contractile unit called
Not so developed
Only one type- cardiomyocyte
How do cardiomyocyes communicate
Gap junctions.
Structure of smooth muscle cels
Single central large nucleus
Not striated
No sarcomere
No T tubules
Contraction of smooth muscle cells
Slower and more sustained and require less ATP
Can remain contracted for hours or days
Can skeletal muscle be repaired
Cant divide but can be regenerated by mitosis activity of satellite cells so that hyperplasia follows muscle injury
Can adult cardiac muscle regenerate
No following damage fibroblast invade, divide and lay down scar tissue
Can smooth muscle be regenerated
They can retain their mitotic activity and can form new smooth muscle cells
Evident in pregnant uterus where muscle wall becomes thicker by hypertrophy
What do cardiac and smooth muscle have in common
Nuclei are central not peripheral
Only one contractile unit
Act as syncytium- wave-like function
Myocytes communicate through gap junctions
What are the differences in cardiac and smooth muscle
Smooth muscle does not contain sarcomeres
Electrical conduction - specialised cells/ routes in cardiac muscle
No troponins in smooth muscle
What is myasthenia gravis
Autoimmune disease
Antibodies block ACh receptor
Endplate ‘invaginations’ in synaptic clefts reduced
Reduced synaptic transmission
Intermittent muscle weakness
What is the structure of myosin
Rod like structure with 2 heads protruding
What does the thick filament consist of
Many myosin molecules
What is the protein components of actin
F-actin fibres
G-actin globules
What forms the thin filaments of skeletal and cardiac muscle
Actin
Tropomyosin
Troponin
What is the role of calcium in contraction
As Ca2+ binds to TnC to tropinin a conformational change moves tropomyosin away from actins binding sites
This allows myosin to bind actin and contraction begins
The tropomyosin sits in the cleft of G-actin spheres
What remains the same during contraction, shorten and com closer
Actin and myosin lengths
Filaments
Sarcomere
Z line
What is the point of origin and insertion for muscles
Bone- typically proximal
The structure the muscle attaches to- distal- may be bone, connective tissue, or tendon (mostly tendon)
What are agonists
Prime movers- main muscles responsible for a particular movement
What are antagonists
Oppose prime moves
What are synergists
Assist prime movers
What are neutralisers and fixations
Neutralisers- prevent the unwanted actions that an agonist can perform
Fixators- act to hold a body part immobile whilst another body part is moving
What is myalgia
Muscle pain
