Muscles Flashcards
What are muscles?
Effectors which enable movement to be carried out
Name the three types of muscles
Smooth muscle
Cardiac muscle
Skeletal muscle
Describe smooth muscle
- made from fusiform cells
- one nucleus per cell
- non straited
- involuntary
- slow wave-like contractions
- fatigue very slowly
Where are smooth muscles found and explain their function and each location
Circulatory system: helps in the circulation of the blood
Digestive system: controls digestive
Respiratory system: controls breathing
Urinary system: controls unrination
Describe cardiac muscles
- branched cells (interconnected)
- one/two nuclei per cell
- striated
- involuntary
- medium speed contractions
- found only in the heart
- contractions of the heart muscles pumps blood throughout the body and account for heartbeat
- healthy cardiac muscle never fatigues
Describe skeletal muscle
- long, cylindrical cells
- many nuclei per cell
- striated
- voluntary
- rapid contractions
- attached to skeleton by tendons
- causes movement of bones at the joint
- fatigue
What are voluntary muscles?
Muscles that can be moved at will
What are involuntary muscles?
Muscles that cannot be move intentionally
What are striated muscles?
Muscles that have stripes across the fibre
What are non-striated muscles?
Muscles that have no stripes across the fibre
Name the functions of muscles
Create movement
Maintains posture and muscle tone
Heat production
Protects the bones and internal organs
Movement of substances in the body
Explain how muscles produce movement
Muscles move bones by pulling not pushing as skeletal muscles can only shorten
What is synergist?
Any movement is generally accomplished by more than one muscle. All of the muscles responsible for the movement are synergists.
What is the agonist?
The muscle responsible for movement
(prime mover)
Contracts
What is the antagonist?
The muscle that opposes movement.
Relaxes
What are levators?
Muscles that raise a body part
Name the skeletal muscle actions
Extensor
Flexor
Adductor
Abductor
Levator
Depressor
Rotator
Sphincter
Describe extensor
Increasing the angle at a joint
Describe flexor
Decreasing the angle at a joint
Describe abductor
Moving limbs away from midline of the body
Describe adductor
Moving limbs towards midline of the body
Describe levator
Moving insertion upwards
Describe depressor
Moving insertion downwards
Describe rotator
Rotating a bone along its axis
Describe sphincter
Constricting an opening
What is the origin?
The location where the tendon joins a relatively stable skeletal (generally the proximal end)
What is the insertion?
The point of distal muscle attachment to the moving bone
What is proximal?
Closer to the midline or closer to the point of attachment
What is distal?
Further away from midline or further away from point of limb attachment
What sort of pattern does a myofibril have?
Cross-striated pattern
What is the I band?
Represents the lighter actin filaments
What is the A band?
Represents darker myosin filaments and lighter actin filaments overlapping each other
What is the Z line?
Bisects I band and adheres to sarcolemma to provide structural stability
What is the M band?
Bisects H zone and consists of protein structures that support arrangement of myosin filaments
What is the H zone?
Only dark myosin filaments
What does the sliding filament theory propose?
A muscle shortens or lengthens because thick myosin and thin actin slide past each other without changing length.
Explain the process of the sliding filament theory
- Myosin cross bridges cyclically attract, rotate and detach from actin filaments with energy from ATP hydrolysis.
- Produces change in relative size within sarcomere’s zones and bands and produces force at Z bands.
- I band decreases as the Z bands are pulled towards the centre of each sarcomere.
What affects muscle’s force and power generating capacity?
Differences in sarcomere alignment
Describe fusiform fibres
Spindle shaped fibres.
Run parallel to muscle’s long axis and taper at its tendinous attachment.
Fibre length equals muscle length.
Facilitates rapid muscle shortening.
Describe pennate fibres
Contain shorter fibres
Possess more individual fibres.
Exhibits less range of motion
Generate considerable power
Pennate fibres lie at oblique pennation angle; what does this allow?
Packing of large numbers of fibres into a smaller cross sectional area,
Allows individual muscle fibres to remain short while overall muscle attains considerable length.
Name type 1 muscle fibre types
Slow twitch
Slow oxidative
Name type 2a muscle fibre types
Fast twitch a
Fast oxidative glycolytic
Name type 2b muscle fibre types
Fast twitch x
Fast glycolytic
Describe the features of type 1 fibres
Contraction time: slow
Size of motor neuron: small
Force production: low
Resistance to fatigue: high
Mitochondrial density: high
Capillary density: high
Oxidative capacity: high
Glycolytic capacity: low
Describe the features of type 2a fibres
Contraction time: moderately fast
Size of motor neuron: medium
Force production: medium
Resistance to fatigue: moderate
Mitochondrial density: intermediate
Capillary density: intermediate
Oxidative capacity: intermediate
Glycolytic capacity: high
Describe the features of type 2b fibres
Contraction time: fast
Size of motor neuron: large
Force production: high
Resistance to fatigue: low
Mitochondrial density: low
Capillary density: low
Oxidative capacity: low
Glycolytic capacity: high
Describe a concentric contraction
The force generated is sufficient to overcome the resistance.
Muscle shortens as it contracts.
Describe an eccentric contraction
The force generated is insufficient to overcome the external load on the muscles and the muscle fibres lengthen as they contract.
An eccentric contraction is used as a means of decelerating a body part or lowering a load gently.
Describe an isometric contraction
The muscle remains the same length whilst contracting.
Describe an isotonic contraction
The tension in the muscle remains constant despite a change in muscle length.
Can only occur when a muscle’s maximal force of contraction exceeds the total load on the muscle.
Describe an isokinetic contraction
The muscle contraction velocity remains constant whilst force remains constant.
Primarily an analysis method used in experiments on isolated muscles.
What is the fulcrum?
Moving joint
What is resistance?
Gravity pulling on the body
What is effort?
Muscle contraction
