MUSCULAR SYSTEM

• What is one of the primary functions of the muscular system?

  Movement of the body
• How do skeletal muscles contribute to posture?


  It maintain tones of muscles for sitting and standing
• Which muscles are involved in respiration?


  Intercostal muscles
• What role do muscles play in body heat production?

  Muscles help regulate body temperature
• What are some forms of communication facilitated by the muscular system?

  Speaking, writing, gesturing, and facial expression
• How do smooth muscles contribute to the constriction of organs and vessels?


  It facilitate digestive mechanisms, proper secretions, and blood flow
• What is the primary function of cardiac muscle?

  Contraction of the heart
• What is a key structural feature of skeletal muscle fibers?


  They have multiple nuclei located in the peripheral system
• What distinguishes skeletal muscle from other muscle types?


  It contains striations and is under voluntary control
• What are the major functional characteristics of skeletal muscle?

  1. Contractility – ability to shorten with force
  2. Excitability – capacity to respond to a stimulus from the CNS
  3. Extensibility – ability to be stretched to their normal resting length
  4. Elasticity – ability to recoil to their original resting length
• What is the connective tissue sheath that surrounds a skeletal muscle called?

  Epimysium or muscular fascia
• What are muscle fasciculi?

  Bundles of fibers that make up the muscle
• What are the parts of a sarcomere?

  • Z-disk: Holds the actin myofilament
  • M-Line: Holds the myosin myofilaments
  • H-Zone: Location of myosin myofilaments only
  • A-band: Contains both actin and myosin myofilaments
  • I-Band: Contains the Z-disk and actin myofilament
• How do actin and myosin myofilaments interact during muscle contractions?

  They connect with each other, causing the sarcomere to shorten
• What are the three main parts of actin myofilaments?

  Tropomyosin filaments, troponin molecules, and actin strands
• What happens to tropomyosin during muscle contractions?


  it moves to expose attachment sites on actin myofilaments
• What is the role of calcium ions in muscle contractions?


  it binds to troponin, causing tropomyosin to move
• What is the neuromuscular conduction process for muscle movement?

  1. Electrical impulses from the brain/spinal cord interact with skeletal muscle fibers through motor neurons.
  2. Activation of many muscle fibers causes muscle contraction and movement.
• What is the resting membrane potential (RMP) of a cell?


  It is the state where there are no electrical charge differences across the membrane
• What ions are predominantly found outside and inside the cell during resting membrane potential?

  Sodium (Na) is predominant outside, and potassium (K) is predominant inside
• What are the types of ion channels in muscle cells?

  • Leak Channels: Transport ions based on diffusion and concentration gradient.
  • Voltage Gated Channels: Require energy and an electrical charge to activate.
• What occurs during depolarization of a muscle cell?


  Sodium enters the cell, making the intracellular area more positively charged
• What is repolarization in muscle cells?


  It is the process of returning to resting membrane potential after depolarization
• What is action potential in muscle cells?

  Rapid depolarization and repolarization of the cell membrane
• What is the role of motor neurons in muscle contraction?

  It stimulate muscle fibers to contract
• What is the neuromuscular junction?

  • It is the junction between a motor neuron and a muscle fiber.
  • It is where communication between motor neurons and muscle fibers occurs.
• What is a motor unit?


  It consists of a motor neuron and the muscle fibers it innervates
• Why is the neuromuscular junction important?


  It is essential for the communication between motor neurons and muscle fibers
• What is the junction between a motor neuron and muscle fiber called?

  Neuromuscular junction
• What is the role of the presynaptic terminal in the neuromuscular junction?

  It releases neurotransmitters to activate action potential in the muscle fiber
• What is contained within the presynaptic terminal that is crucial for muscle contraction?

  Neurotransmitters
• What is the function of acetylcholine in the neuromuscular junction?


  It binds to receptors in the muscle fiber to activate voltage-gated channels
• How does the binding of acetylcholine affect the muscle fiber?

  It creates an electrical gradient that triggers depolarization and contraction
• What happens to acetylcholine after it binds to the muscle fiber?

  It unbinds from the gated sodium channel, which then closes
• What enzyme breaks down excess acetylcholine to stop continuous depolarization?

  Acetylcholinesterase
• What initiates the action potential in muscle cells?

  Sodium diffusion into muscle cells
• What is the role of calcium in muscle contraction?

  It binds with troponin to allow muscle contraction
• How does tropomyosin affect muscle contraction?

  it moves to expose binding sites on actin for myosin heads
• What energy source do myosin heads use during muscle contraction?

  ATP
• What happens to myosin heads after they bind to actin during contraction?

  They release phosphate and pull actin towards the left