Exam 2 lecture 2

Lab Overview

• Upcoming lab is focused on cat muscle anatomy, particularly Figures 7.17 and 7.18.

  • Figure 7.19 provides an additional view but does not introduce new content.

• This muscle lab is lighter compared to future labs on shoulder, arm, hip, and leg muscles.

• Emphasis on understanding prior lab content before proceeding to more complex topics.

Muscle Functions

• Key muscle actions include:

  • Adduction and Abduction: Movement toward or away from the midline.

  • Flexion and Extension: Changes in angle at joints — flexion decreases angle, and extension increases angle.

  • Supination and Pronation: Rotational movements, often related to the forearm.

  • Protraction and Retraction: Forward and backward movement of structures.

• Importance of recognizing these actions as they relate to muscle function, especially concerning joints and angles.

Muscle Contraction

• Muscles contract by shortening, pulling on bones via tendons connected to the skeletal system.

• The contraction is a crucial mechanism by which muscles generate movement.

• Skeletal muscles are designed specifically to facilitate bone movement based on leverage mechanics.

• Lever systems play a vital role in muscle dynamics:

  • The involvement of input length (the distance the muscle pulls) versus output length (distance the bone moves).

  • Short input length with long output length results in fast movement but lower strength.

  • Long input length with short output length produces greater force but slower movement.

Lever Mechanics

• Class of levers in the human body:

  • Leverage is a principle seen in tools (e.g., screwdrivers, tire irons) and biological systems (muscles).

  • Example: Long input length (tire iron) allows easier lifting of heavy weights than short input length (fingers).

  • The fulcrum (pivot point of lever) influences the mechanical advantage in lifting.

Comparative Examples in Anatomy

• Differences in muscle placement (insertion points) on bones affect strength vs. speed in limb motion:

  • Muscle positioning evolves in species based on ecological needs (e.g., digging vs. sprinting).

  • Example of teres major muscle varies in location to optimize function for different species such as armadillos and cheetahs.

Abdominal and Jaw Muscles

• Abdominal muscles consist of three layers: external oblique, internal oblique, and rectus abdominis (visible as a six-pack).

• Muscles for jaw movement include temporalis (enables jaw clenching).

• **Sternocleidomast