HUBS191_Lect8_2025

HUBS 191 Lecture Materials

• This material is not a substitute for attending lectures.

• Use provided content alongside live lectures for better understanding.

Copyright Notice

• All resources for the course are copyrighted, covering video/audio recordings, PowerPoints, lecture notes, and handouts.

• Access is granted for private study; redistribution is prohibited.

Example Exam Question (Page 3)

• Question: If the cell was moved to a hypotonic solution, what would likely occur?

• Options:

  • A. Solute moves in, increases cell weight.

  • B. Water moves in, causing swelling.

  • C. Solute moves out, disrupting function.

  • D. Water moves out, causing shriveling.

Objectives and Study Guide (Page 4)

After lecture, be able to:

• Describe the three main types of muscle in the body.

• Explain key elements of skeletal muscle structure.

• Describe skeletal muscle excitation.

• Related Reading: Martini et al. Modules 9.2, 9.3, 9.8.

Types of Muscle in the Body (Page 5)

• Smooth Muscle: Lines hollow organs; involuntary.

• Cardiac Muscle: Found in the heart; involuntary, pumps blood.

• Skeletal Muscle: Attaches to bones; mostly voluntary, controls movement and posture.

• All muscle types generate force through contraction.

Skeletal Muscle Overview (Page 6)

• Skeletal muscles are under voluntary control.

• Main job: develop force through contraction.

• Additional functions include:

  • Support for organs.

  • Control openings for substance passage.

  • Heat production for core temperature maintenance.

Whole Muscle Structure (Page 7)

• Muscle cells called muscle fibers, grouped into fascicles, making muscles.

• Composed of blood vessels, nerves, surrounded by connective tissue.

• Connective tissue forms tendons attaching muscles to bones.

Individual Muscle Fiber Structure (Page 8)

• Muscle fiber consists of bundles of myofibrils; myofibrils are formed from sarcomeres.

• Sarcomeres are made of actin (thin) and myosin (thick) myofilaments.

• These myofilaments create a striated appearance of muscle.

Cellular Structures in Muscle Fibers (Page 9-10)

• Sarcolemma: Membrane of muscle fibers.

• T-tubules: Extensions of sarcolemma conducting electrical signals.

• Sarcoplasmic Reticulum (SR): Stores calcium; releases calcium to aid contraction.

Example Exam Question (Page 11)

• Which statement about muscle fiber structure is NOT correct?

• Options:

  • A. Sarcomeres consist mainly of actin and myosin.

  • B. T-tubules extend from the sarcolemma.

  • C. Skeletal muscle's striated appearance is due to myofilament organization.

  • D. SR houses muscle cell DNA.

Excitation-Contraction Coupling (Page 12)

• EC-coupling links signaling with contraction

• Key proteins:

  • DHPR: Voltage sensor; interacts with t-tubules.

  • Ryanodine Receptor (RyR): Passive calcium channel.

  • SERCA: Calcium pump returning calcium to the SR.

Process of EC-Coupling (Page 13-14)

• Signal transmission from nerves to muscle via T-tubules.

• Activates DHPR, opening RyR and releasing calcium to trigger contraction.

Muscle Relaxation (Page 15)

• To relax, calcium is pumped back into SR by SERCA, ending the signaling and allowing relaxation.

Summary of Muscle Types and Structure (Page 17)

• Three muscle types: smooth, cardiac, skeletal; similar yet distinct.

• Skeletal muscle organized in fascicles; structured at the cellular level with sarcomeres.

• EC-coupling pairs signaling events with muscle contractions, involving DHPR, RyR, and SERCA.

Example Exam Question (Page 18)

• What event contributes to muscle relaxation?

• Options:

  • A. Signal through t-tubules.

  • B. SERCA moves calcium into SR.

  • C. DHPR activation.

  • D. RyR releases calcium from SR.

Copyright Warning (Page 19)

• Course materials for educational use only; redistribution or reproduction is prohibited without permission.