muscle tissue Flashcards
what are the three types of muscle tissue
skeletal, smooth and cardiac
what is skeletal muscle
> Long, cylindrical striated fibres, multiple nuclei
Voluntary
Slow to fast and non-rhythmic
Bone to bone or bone to skin
what is the smooth muscle
> Spindle shaped, unstriated, single nuclei
Involuntary, response to nervous, chemical or hormonal or stretch
Very slow some being rhythmical
Found in the walls of the GI tract, resp and reproductive systems. Other organs such as bladder and skin etc.
what is the cardiac muscle
> Branched chains, striated, single nuclei
Involuntary, affected through hormones/ neurotransmitters
Slow, rhythmical contraction
Heart walls
structure of a muscle
- Whole muscle (an organ) Epimysium
- Muscle fascicle (portion of the muscle) perimysium
- Muscle fibre (muscle cell) Endomysium
4.Myofibril (specialised intramuscular structure) - Sarcomere / Thick + Thin filaments (cytoskeletal element)
what happens in a muscle contraction
- Nerve impulse arrives at axon terminal of motor neuron and triggers release
of acetylcholine (ACh). - ACh diffuses across synaptic cleft, binds to its receptors in the motor end plate, and triggers a muscle
action potential (AP). - Acetylcholinesterase in
synaptic cleft destroys ACh so another muscle
action potential does not
arise unless more ACh is
released from motor neurone. - Muscle AP traveling along transverse tubule opens Ca2+ release channels in the
sarcoplasmic reticulum (SR) membrane, which allows calcium ions to flood into the sarcoplasm - Ca2+ binds to troponin on the thin filament, exposing
the binding sites for myosin. - Contraction: power strokes use ATP; myosin heads bind to actin, swivel, and release; thin filaments are pulled toward centre of sarcomere.
- Ca2+ release channels in SR close and Ca2+ active transport pumps use ATP to restore low level of
Ca2+ in sarcoplasm. - Troponin-tropomyosin complex slides back into position where it blocks the myosin binding sites on actin
- Muscle relaxes.
what are the 3 skeletal muscle fibre types
> Type I fibres, Slow twitch, Slow Oxidative (SO)
Type IIa fibres, Fast oxidative-glycotic (FOG)
Type IIb fibres, Fast glycolytic (FG)
what are type 1 fibres
> Mitochondria= most
Colour= red
ATP Capacity= high
Respiration Type= anaerobic
Speed of Contraction= slow
Fatigue Resistance= high
Primary Functions= maintaining posture, endurance exercise
what are type IIa fibres
> Mitochondria= many
Colour= pink
ATP Capacity= intermediate
Respiration Type= anaerobic & glycolysis
Speed of Contraction= fast
Fatigue Resistance= intermediate
Primary Functions= walking, sprinting
what are type IIb fibres
> Mitochondria= few
Colour= pale/white
ATP Capacity= low
Respiration Type= glycolysis
Speed of Contraction= fast
Fatigue Resistance= low
Primary Functions= rapid, intense movements, short duration
what are muscles spindles
> Muscle spindlesare stretch receptors within the body of amusclethat primarily detect changes in the length of themuscle
Each muscle spindle consists of several slowly adapting sensory nerve endings that wrap around 3 to 10 specialized muscle fibres.
Muscle spindles are plentiful in muscles that control fine movements and much more sparse in those that control course or forceful movements
When the muscle spindle is stretched and excited it sends impulses to the spinal cord more rapidly (increased frequency), which stimulate the muscle fibres of the stretched muscle to contract and resist further stretching.
what are Golgi tendon organs
> A proprioceptive sensory receptororganthat senses changes in muscle tension.
If excessive tension in the muscle occurs, stimulation of this golgi tendon organ will inhibit the muscle contraction via an interneuron
what are the properties of muscles
> Elasticity
Extensibility/plasticity
Contractility
Excitability
what does elasticity mean
> The ability to recoil to its resting length after stretching- resuming
its previous length and shape
Not limited to muscle, many structures are elastic
All muscle types (skeletal, cardiac and smooth) return to shape after contracting
what does extensibility mean
> The ability to stretch without damage
Although muscle cells shorten when contracting they can be stretched beyond their resting length when relaxed
We use stretching exercises (lengthening by applying a force) often as physiotherapists
Principle of muscle stretching => take muscle attachments further away from one another
