Muscles Flashcards
Name the different level of muscle organisation from smallest to largest
myofilaments ( thick and thin protein filaments) –> myofibrils (individual fibres) —->along with Myocytes form muscle fibers)—>Muscle bundle (Fascicle)–> muscle tissue
Name the fibrous OUTER COVERINGS of muscle levels
Epimysium (over entirel muscle organ)
Perimysium (around a fascicle(bundle) of muscle fibers)
Endomysium (around individual cell/fibres)
Muscles can be …… OR ……
……. OR …….
Voluntary OR Involuntary
Striated (multinucleated) OR non striated (mononucleated )
What is a striated muscle
MULTI nucleated muscle cells (Striped appearance)
Skeletal and cardiac muscle
What is a non-striated muscle?
Smooth muscle
Name the types of muscles (3 main types) with an example
Skeletal-orbicularis iris
Cardiac-heart only
Smooth- vessel/gland linings eg ducts of glands
Describe a skeletal muscle and 5 important features
most common-found all over body limbs/head etc
Striated ( multinucleated ) muscle
Voluntary control- somatic nervous system
no gap junctions
Contractile unit = sarcomere
what is the contractile unit of a skeletal muscle
sarcomere
Describe a cardiac muscle and 5 distinguishing features
Found only in the heart
- Striated muscle (multinucleated)
involuntary control
Gap junctions between sarcomeres
self excitatory (syncytium ) -ie act as 1 muscle to allow coordinated pump
Describe a smooth muscle and 6 distinguishing features
Involuntary control
Non- striated
mono nucleated cells
No sarcomere structure
No t tubules
Calcium enters from OUTSIDE cell and binds CALMODULIN not troponin
2 types 1. single unit eg in gut lining
2. multi unit -eg pupil muscle
Myofilaments more free of movement (from lack of sarcomeric structure)
Name the 2 types of smooth muscle and differences
Single unit - eg lining gut
In sheets for peristalsis
self excitatory
Gap junctions - to allow impulse cell to cell
Multi unit ( pupil eye muscles)
Single units that act INDEPENDENTLY
NO Gap junctions
Not self excitatory -respond nervous stimuli
Name and describe 3 function of skeletal muscles
- Movement - by Muscle Contractions
- Heat production -e.g. shivering)
- Posture - continuous partial muscle contractions allow stability (e.g. standing, sitting)
What is the cell membrane of muscle called?
Sarcolemma
What is the cytoplasm of muscle called?
Sarcoplasm
What is the function of the Sarcoplasmic reticulum ?
Store calcium ions
Name the basic makeup of a skeletal muscle from start to the muscle tissue
Myofilaments - thin and thick protein filaments form a myofibril
1000s of myofibrils form a muscle fiber
Muscle fibers bundled to form a muscle fascicle (bundle)
Muscle bundles Form muscle tissue
Explain the basic contractile unit and its components
Think (Muscle alphabet (HIT ZAM)
A sarcomere is the basic contractile unit of a muscle fiber
Made up of myofilaments ( thin and thick filaments made up of 4 protein filaments
Thick filament = myosin
Thin filament - actin/troponin/tropomyosin
( troponin and tropomyosin are blocking proteins that stop when muscle relaxed the joining of the actin and myosin )
Heller (H )band - segment of the thick filament NOT overlapping the thin filament
Isotropic(I ) band - segment often filament NOT overlapping the thick filament
T tubules - infolding of the sarcolemma allowing impulse to travel - found between A and I band junction
Z disc - anchoring point t for myofilaments ( 1 sarcomere is from Z disc to next Z disc)
Anisotropic( A ) band - entire length of the thick filament
M line - middle line of thick filament ( m-orotein here anchors the thick filament )
What 3 requirements are needed for a skeletal muscle contraction
Nerve impulse
Calcium flooding
ATP ( energy ) from mitochondria
Explain how muscles are contracted.
- Nerve impulse travels down T tubule to sarcoplasmic reticulum
- Calcium channels open
- Calcium floods into the sarcolemma
- calcium binds to troponin unblocking the actin ACTIVE site
- Myosin ( thick filament ) and actin ( thin filament ) bind
- Actin “pulled along” past the thick filament
.(the muscle contraction) - Calcium Channels close up immediately
- Calcium ACTIVELY pumped back into Sarcoplasmic reticulum for storage
What is the sliding filament theory
Explains the mechanism of muscle contraction , the myosin (thick filaments) of muscle fibers slide past the actin (thin filaments) during muscle contraction, while the two groups of filaments remain at relatively constant length.- if need to can explain how the muscle contracts via Calcium etc
What is a sarcomere
The basic contractile unit of skeletal muscle
What is the T tubule and where is it found
T ( transverse ) tubule is an inward fold of the sarcolemma of a skeletal muscle ) and allows electrical impulses to travel deep into the muscle cell.
Found between the A and I band of the sarcomere
Name the four proteins that make up myofilaments and which filament they are found in
- Myosin (thick)
- actin (thin)
- Troponin (thin)
- Tropomyosin (thin)
Name the protein filament (s ) in thick filaments
Myosin
Name the protein filament in thin filaments
Actin
Troponin
tropomyosin
Which are the blocking proteins in myofilaments
Troponin and tropomyosin ( block myosin from binding to actin)
Are cardiac muscles non-striated / striated and voluntary / involuntary
striated and involuntary (smooth muscle)
Where are cardiac muscle found?
Only found in heart wall
What’s the primary function of cardiac muscles?
Pump blood
How do cardiac muscles maintain a coordinated pumping action?
Self-exciting and act as a whole continuous electrically-coupled muscle mass thru gap junctions between sarcomeres
In smooth muscles, calcium ions come from the outside of the cell/fibre and bind to what?
Calmodulin protein
What are the 2 types of smooth muscles and an example?
Single unit (visceral-intestine lining)
Multi unit (pupil muscles )
how are the smooth muscle cells/fibres connected?
By gap junctions
In single unit smooth muscles, how is contraction initiated?
By nerve fibres and nerve impulses which pass through gap junctions from muscle to muscle
Is the single unit smooth muscle self excitatory?
Yes (like cardiac muscles)
And acts as a single contractile unit
Are multi unit smooth muscles self excitatory?
NO
Respond to nervous stimulation
Describe a muscle related genetic DISORDER. (Cause and symptoms)
Duchenne Muscular Dystrophy (DMD)
In males only -genetic
Cause: faulty dystrophin protein- fails to anchor cytoskeleton to sarcolemma (membrane) in muscle cells
Symptom: Muscle wasting, motor skill difficulty, skeletal deformities, death in 20s
No cure
Describe a muscle related INFECTION.
Tetanus (lockjaw )
Toxin produced by bacterium clostridium tetani
Overstimulates nervous system
Causes painful muscle spasms -ususally starts in the head
What is the treatment tetanus
Antibiotics but there is also a vaccination of inactive toxin
