Muscles Flashcards
Which are the three different types of muscle cells?
Muscle cells
- Skeletal muscle cells
- Cardiac muscle cells
- Smooth muscle cells
What are the functions of the skeletal muscles?
Skeletal muscles - 40-50% of total body weight
Voluntary
- Mostly movements of bone & body parts (produce body movements)
- Stabilizing body positions
- Store and move subtances
- Produce heat (shivering)
Explain the function of Cardiac muscle tissue.
Cardiac muscle tissue
Involuntary
- Heart only
- Develops pressure for arterial blood flow
What is the function of Smooth muscle tissue?
Smooth muscle tissue - grouped in walls of hollow organs
- Sphincters regulate flow in tubes
- Maintain diameter of tubes
- Move material in GI tract and reproductive organs
The Skeletal muscle tissue is well supplied with?
Skeletal muscle tissue
- Well-supplied with blood vessels and nerves
- Terminal of a neuron on each side of the muscle fiber.
Explain the following terms associated with skeletal muscle histology:
- Sarcolemma
- Transverse tubules
- Nuclei
- Sarcoplasm
Muscle histology
- Elongated cylindrical cells = muscle fibers
- Plasma membrane = sarcolemma
- Transverse tubules (T) tunnels from surface to center of each fiber
- Multiple nuclei lie near surface of cell
- Cytoplasm=Sarcoplasm
Explain the function of sarcoplasmic reticulum in skeletal muscle tissue.
Stores calcium ions.
Sarcoplasm contains … ( specific protein)?
Sarcoplasm contains Myoglobin
Red pigmented protein related to Hemoglobin that carries oxygen.
What are Myofibrils made of?
Myofibril consists of the proteins Actin (Thin filament) and Myosin (Thick filament).
Explain the mechanism of Sarcomeres.
Functional structure of Sarcomeres
- Thick filaments (myosin) have moveable heads (like “heads” of golf clubs).
- Thin filaments (actin) are anchored to Z discs.
- Contain myosin binding sites for myosin head
- Also contain tropomyosin & troponin
- Tropomyosin blocks myosin binding site when muscle is at rest.
Explain structure of Myosin in Skeletal muscle fibers.
See picture.
Explain the structure of Thin filaments in Skeletal muscle fibers.
See Picture.
Explain function of Tropomyosin in Skeletal muscle cells.
Troposin (in Thin filaments) blocks myosin binding site when muscle is at rest.
Explain the Sliding Filament Mechanism in Skeletal muscle cells.
Sliding Filament Mechanism
- During contraction Myosin heads Actin sites.
- Myosins pull and slide Actin molecules (and Z discs) toward H-zone.
- I-bands and H-zones become more narrow.
- Sliding generates force and shortens sarcomeres and thus fibers.
Explain the Neuromuscular interaction of Skeletal muscle tissue.
Neuromuscular interaction
- Nerve signal triggers muscle action potential
- Delivered by a motor neuron
- One neuron can trigger 1 or more fibers at the same time
- The more precise movements needed, the fewer fibers are activated
- Neuron plus triggered fibers = Motor unit
What is a Motor unit?
Motor Neuron plus triggered Skeletal muscle fibers.
Explain the action of NMJ.
Neuromuscular Junction (NMJ)
- Release of Acetylcholine (ACh)
- Diffuses across cleft
- Activation of ACh receptors
- Generation of Muscle Action Potential
- Repeats with each neuronal action potential
- Breakdown of Ach (Acetylcholinestras)
Explain Contraction Trigger associated with Skeletal muscle fibers.
Contraction Trigger
- Muscle action potential -> Ca2+ release from Sarcoplasmic Reticulum (SR)
- Ca2+ binds to troponin ->
- Moves tropomyosin off actin sites ->
- Myosin binds & starts cycle
Explain Relaxation associated with Skeletal muscle tissue.
Relaxation
- Breakdown of ACh to stop muscle action potentials
- Ca2+ ions transported back into SR lowering the concentration ->
- This takes ATP
- Tropomyosin covers actin binding sites.
What is Muscle Tone?
Muscle Tone
- Even at rest some motor neuron activity occurs = Muscle Tone.
- If nerves are cut fibers become flaccid (very limp)
Explain the production of ATP for muscle contraction.
See picture.
Explain Aerobic Cellular Respiration.
Aerobic Cellular Respiration
- Production of ATP in mitochondria.
- Requires oxygen and carbon substrate.
- Produces CO2 and H20 and heat
Explain muscular fatigue.
Fatigue
- Inability to contract forcefully after prolonged activity
- Limiting factors can include:
- Ca2+
- Creatine Phosphate
- Oxygen
- Build up of acid
- Neuronal failure
Explain oxygen use after exercise associated with skeletal muscles.
Oxygen use after Exercise
- Convert lactic acid back to glucose in liver
- Resynthesize creatine phosphate and ATP
- Replace oxygen removed from myoglobin
Explain different levels of contraction concerning skeletal muscles.
Myogram
Explain the terms agonist-antagonist.
Skeletal muscles are generally arranged in opposing pairs (agonist - antagonist)
- Flexors - Extensors; Abductors - Adductors.
Superficial Skeletal Muscles
See picture.
Muscles of the Head
Muscles of the Head
Facial expression = Precis movement
Muscles of the Eyeball
Muscles of Abdomen
Muscles of Abdomen
Muscles of Forearm
Muscles of Forearm
Two exampels of Muscular disorders and diseases.
Muscular disorders and disease
- Quite rare…
- Muscular dystrophy
- Myasthenia gravis - (Ach receptors)
What happens with the skeletal muscle tissue when we age?
Age
- As with bone there is a slow progressive loss of skeletal muscle
- Relative numbers of SO (slow twitch oxidative) fibers tends to increase.
