Chapter 9: Muscle Types Lecture

Overview

• Focus on different muscle types not covered earlier.
• No deep dive into physiology; only specific topics.

Smooth Muscle

• Involuntary Muscles: No conscious control; managed by the nervous system.
• Structure: Spindle-shaped; differs from skeletal muscles.
  • More actin than myosin (important for slow, organized contractions).
  • Not multinucleated like skeletal muscles.
• Contractions: Spiral or wave-like patterns, unlike parallel contractions in skeletal muscles.
  • Cross-bridging is less intense.
  • Calcium for contractions comes from both extracellular fluid and sarcoplasmic reticulum.
  • Uses calmodulin (vs. troponin in skeletal muscles).
• Functional Characteristics
  • Involved in internal organs (e.g., stomach, bladder, uterus).
  • Autorhythmic contractions (e.g., peristalsis in digestive tract).
  • Respond to stretching (e.g., food in esophagus).
  • Controlled by the autonomic nervous system (ACh and norepinephrine).

Cardiac Muscle

• Location: Found only in the heart.
• Structure: Striated like skeletal muscle but with branching fibers.
  • Adjacent cells connected by intercalated discs.

Effects of Aging on Muscles

• Sarcopenia: Age-related muscle atrophy.
  • Begins around 25 years old; up to 50% muscle mass loss by age 80 for inactive individuals.
• Importance of Activity
  • Gentle weightlifting and walking can reduce atrophy.
  • Exercise benefits muscles, tendons, and bones.
  • Posture and walking muscles are crucial as one ages to avoid falls.

Summary

• Recap important points using chapter outlines, review questions, and critical thinking exercises.
• Stay organized and use additional study material provided at the end of the chapter.