9/10) Muscle Tissue Structure, Function & Disease Flashcards
Define myalgia
muscle pain
Define myasthenia
muscle weakness
Define myopathy
diseases of the muscle
Define myocardium
muscle component of the heart
Define myoclonus
sudden muscle spasm
What are the different muscle types?
Striated - skeletal muscle, cardiac muscle
Non-striated - smooth muscle
What is the function of myoglobin?
Store O2 and provide it to striated muscle
What is a sarcolemma?
the outer membrane of the muscle
What is sarcoplasm?
cytoplasm in muscle cells
What is the sarcoplasmic reticulum?
Smooth endoplasmic reticulum in the muscle
What is the sarcosome?
mitochondria in the muscle
What is the sarcomere?
the STRIATED muscle contration unit
What is the structure of skeletal muscle?
Epimysium - dense connective tissue surrounding the whole muscle
Perimysium - dense connecting tissue surrounding the fasicle
Endomysium - loose connective tissue surrounding the individual muscle fibres
Where is the point of origin?
the muscle attachment site that does NOT move during muscle contraction
Where is the point of insertion?
the muscle attachment site the DOES move during muscle contraction
What is the function of skeletal muscle?
contraction in the direction of the muscle fibres
What are extrinsic muscles?
muscle connected to BONE via tendons or cartilage
What are intrinsic muscles?
muscles connected to other muscles
Where are the nuclei located in skeletal muscle?
peripheral nuclei
Describe the capillary netweork in skeletal muscle
Capillaries run parallel to the muscle then break through into the muscle fibre
thicker fiber = thicker capillary = more blood
Describe the structure of myofibrils
Z bands - determine the size of the sarcomere
I band - only actin filament
A band - contains myosin filament (and actin)
H band - contains myosin ONLY
M line - centre of sarcomere
What colour does myosin appear?
Dark
What colour does actin appear?
light
What happens to the sarcomere during contraction?
Z and I bands mover closer together as the actin slides over the myosin
What are the 2 types of skeletal muscle fibres?
Slow twitch
Fast twitch
State 8 characteristics of slow twitch fibres
Red colour Carry out aerobic respiration Many cytochromes Many mitochondria Rich capillary network High mnyoglobin levels Long distant exercise/fatigue resistant Involves fatty acids
State 8 characteristics of fast twitch muscle fibre
White in colour anaerobic respiration few cytochromes few mitochondria poor capillary network few myoglobin uses glycogen sprinting/rapdly fatigue
What 2 factors allow muscle contration to occur?
Ca2+ ions
ATP
What is the role of titin in muscle contraction?
Titin pulls the actin back to its original position once muscle contraction has occured
What is the contraction unit in cardiac muscle?
Cardiomyocytes
What is hypertrophy?
the enlargement of cardiomyocytes
What is atrophy?
the shrinking of cardiomyocytes
What is hyper plasia?
The multiplication of cardiomyocytes
Where are the nuclei in cardiac muscle fibres located?
Centrally suurounded by glycogen (white)
How do impulses travel through the heart?
1) AP generated in the sinoatrial node
2) AP travels through the wall of the atria
3) AP reaches the atrioventricular node , causing a delay in the AP to allow the atria to contract
4) AP travels down the bundle branches to the purkinje fibres
5) AP travels to the walls of the ventricals to allow the heart to contract in unison
What are purkinje fibres?
modified cardiomyocytes that conduct APs rapidly allowing the ventrical walls to contract in sync
Give 3 characteristics of purkinje fibres
abundant glucose - good conductor of electricity
sparse myofibrils - function quickly
extensive gap junctions - function quickly
What shape is smooth muscle?
fusiform (spindle shaped)
Where are the smooth muscle nuclei located?
1 centrally located nuclei
Why do smooth muscle tear less easily than other muscle?
It undergoes hypertrophy after hyperplasia
What are the 3 types of tears?
mild
moderate
severe
How do skeletal muscles repair muscle damage?
Satellite cells fuse with existing muscle mass to increase their muscle mass (hypertrophy)
Hyperplasia caused by satellite cells dividing
How does cardiac muscle repaitrmuscle damage?
It cant
Fibroblasts invade damaged cells, divide and lay down scar tissue
How does smooth muscle repair muscle damage?
Hyperplasia
How can nerves cells impact skeletal muscle contration?
Varicosities!
contain vesicles and mitcohondria. Mitochondria activated and releases Ca2+ which causes the vescile to fuse withthe membrane and release its neurotransmitter
How does the body slow down your heart rate?
Parasympathetic NS
Signal sent from the cranium through the vegas nerve to the atria. 2 nerves, 1 to each atrium
How does your heart rate increase?
Sympathetic NS
Signal sent from spinal cord through sympathetic fibres to the ventricals, causing heart to beat faster.
Sends a nerve close to a cardiomyocyte which releases a neurotransmitter which acts on the sarcolemma of the cell membrane, inducing an electrical signal which acts on the t tubules which interacts with a calcium channel filled with DHP, causes shape change, then shape cahnge in adjacent protein. Allows Ca2+ out of SR into the cytoplasm where it interacts with actin by binding to troponin C, allowing contraction to occur
Describe the events leading to skeletal muscle contraction?
1) Nerve impulse travels along the motor neurone to the neuromuscular junction
2) This activates vesicles causing them to fuse with the cell membrane, releasing acetylcholine into the synaptic cleft and depolarise the sarcolemma
3) The Ach bind to nicotinic acetylcholine receptors
4) This opens voltage gates Na+ channels to open, causing an influx of Na+
5) This causes general depolarisation over the sarcolemma and into t tubules
6) T tubule changes its confirmation
7) gated Ca2+ channels are opened and Ca2+ is released into the sarcoplasm
8) Ca2+ binds to troponin C, beginning contraction cycle
9) Ca2+ ions are returned to the terminal cisternae of the SR by SERCA
What is myasthenia gravis?
An autoimmune disease caused by auto-antibodies binding to nicotinic Ach receptors and blocking them
What symptoms are associated with myasthenia gravis?
Ptosis - droopy eye
Larger end plate terminal
What makes up the troponon complex?
Troponin I
Troponin C - binds calcium
Troponon T
How does a powerstroke occur?
1) ATP binds to myosin head, (conf change)brings it closer to actin
2) ATP hydrolysis occurs, ADP + Pi formed (stays attached to myosin head), brings myosin head even closer to actin (conf change)
3) Myosin head binds to actin
4) ADP + Pi unbind from myosin (conf change), pulls actin towards M line
What is an agonist?
The prime mover (main muscle responsible for a movement)
What is an antagonist?
Oppose agonist
What is a synergist?
Assist agonists
What is a neutraliser?
prevent the unwanted actions that an agonist can perform
What are fixators?
Act to hold a body part immobile whilst another body part is moving
What causes compartment syndrome?
Trauma in one compartment could cause internal bleeding which exerts pressure on blood vessels and nerves
State 3 symptoms of compartment syndrome
- deep constant poorly localised pain
- bruising and swelling
- parasthesia (pins and needles)
How is compartment syndrome treated?
Fasciotomy - open one compartment, let fluid out, repair with skin graft
What is muscle tone?
The tension in the muscle at rest
What is muscle strength?
The muscles ability to contract and create force is response to resistance
What is Duchene muscular Dystrophy?
An X linked recessive gene that causes a mutation in the dystrophin gene
What occurs in Duchene Muscular Dystrophy?
Excess calcium enters the cell Calcium taken up by mitochondria Water taken in with calcium Mitochondria burst Muscle cell bursts (Rhabdomyolysis) Muscle cell replaced with adipose
What in the blood indicated Rhabdomyolysis has occurred?
`Extremely high levels of:
- creatine kinase
- myoglobin
What markers are used to diagnose Cardiac Ischaemia?
Troponin I and T
