Structure of Skeletal, Cardiac and Smooth Muscle Flashcards
What enables body movement ?
Skeletal muscle contraction
What enables body posture ?
Continual adjustments of skeletal muscles
What enables support and protection ?
Skeletal muscles
e.g. surrounding joints and within the abdominal wall
What enables sphincter control ?
Skeletal and Smooth muscle - cardiac sphincter in stomach; bladder; anus
What enables movement of food along the GIT ?
Smooth muscle generates peristalsis
What enables regulation of blood flow ?
Cardiac muscle pumps blood
Smooth muscle in vessel walls regulate blood flow
What enables temperature regulation ?
Skeletal muscle - shivering
Smooth muscle - erection of hairs
Name the 4 characteristics of ALL muscle
Excitability
Contractility
Extensibility
Elasticity
What is meant by excitability ?
Responsive to stimuli
i.e. a chemical signal such as a neurotransmitter
What is meant by contractility ?
Ability to shorten forcibly when adequately stimulated
Concentric contraction
Muscle shortens
Eccentric contraction
Muscle is stretched
Isometric contraction
Muscle contracts but does not shorten
What is meant by extensibility ?
Can extend beyond their resting/relaxed length
What is meant by elasticity ?
Recoil and resume its resting length after stretching
State the common features of all muscle
Actin and myosin
Use of ATP
Calcium ions
Stimulation
Function of actin and myosin
Generate force for contraction
How is ATP generated ?
generated via respiration
- Aerobic oxidative respiration
- Anaerobic glycolytic respiration
Function of calcium ions
Needed for activation of contraction
Function of stimulation
Need an action potential from a neuron
What % of muscle protein does actin and myosin make up ?
around 90%
What are actin and myosin ?
They are both enzymes :
ATPases - hydrolyse ATP –> ADP + Pi
Describe some muscle cell components
Cell membrane - sacrolemma
Cytoplasm - sacroplasm
Nuclei, organelles …
Full of myofibrils - actin/myosin
Many mitochondria
Extensive sarcoplasmic reticulum
Function of transverse T tubules
Brings action potentials into interior of muscle fibre
Briefly describe skeletal muscle
640 muscles : 40% of body mass
Attached to the skeleton via tendons
Voluntary and reflexive control
Sporadic and continual contraction
Describe skeletal muscle cells
Large multinucleate cells (100micrometres - 60mm)
State the 3 layers that form the tendons
Epimysium - outer
Perimysium - middle
Endomysium - innermost
What in the function of the 3 layers ?
They are connective tissue which covers and supports muscle.
Maintains structural integrity
Myocyte
A single muscle cell, containing myofilaments
Myofilament
Contractile units called SARCOMERES
What are myofilaments composed of ?
Actin and Myosin
Fasicle
Grouping of elongated bundles of muscle fibres (cells)
Endomysium
Separates the muscle fibres
Perimysium
Loose collagenous connective tissue that surrounds fascicles
Epimysium
Dense collagenous sheath that surrounds gross muscle.
Briefly describe cardiac muscle
Can contract without stimulation - auto-rhythmic
Involuntary muscle : ANS
Branched cells
Describe cardiomyocytes
- Striated
- Small
- Uni or Bi-nucleated
- Large number of mitochondria (25-30% of cell volume)
- Aerobic respiration : can use multiple fuel sources
- Intercalated discs : gap junctions / desmosomes
What are GAP junctions ?
They are formed by connexions - 6 subunits/channel
Sites of low electrical resistance
They electrically connect cells
Function of GAP junctions in cardiac muscle
Electrically links cardiomyocytes - allows diffusion of ions
Cells of the myocardium contract as a unit (ALL or nothing)
State the 7 places where smooth muscle is found
Blood vessels
Digestive tract
Bladder wall / urinary tract
Respiratory tract
Reproductive tract
Eyes
Skin
Briefly describe smooth muscle cells
Small - 100-200 micrometers in length
Spindle shaped cells arranged into sheets
Less regularly organised
NO striations
Single nucleus
Involuntary - ANS, hormones and stretch
Describe the structural organisation of smooth muscle
Longitudinal and Circular layer
Difference between smooth muscle and cardiac/ skeletal muscle
Smooth muscle has a slower contraction rate and a longer duration than cardiac or skeletal muscle.
Describe actin and myosin in smooth muscle
Actin and myosin anchored via dense bodies throughout the sarcoplasm.
Focal adhesions structurally connect cells
Summary of skeletal muscle
Size - LARGE ( up to 60cm)
Shape - Regular parallel myofibres
Striations - Yes
Nuclear content - Multinucleated
Intercalated discs - NO
Gap junctions - NO
Control - Voluntary (via motor neurons and reflexive)
Metabolism - Aerobic and anaerobic
Summary of cardiac muscle
Size - Small (50-100 micrometers)
Shape - Branched
Striations - Yes
Nuclear content - 1/2 nuclei
Intercalated discs - Yes
Gap junctions - Yes
Control - Involuntary (via AND hormones and stretch)
Metabolism - Aerobic
Summary of smooth muscle
Size - Small (30-200 micrometers)
Shape - Spindle
Striations - No
Nuclear content - single nuclei
Intercalated discs - No
Gap junctions - Yes
Control - Involuntary (via AND hormones, local chemicals and stretch)
Metabolism - Mainly aerobic
