Second exam second recording

Introduction to Movement without Muscles

  • Some organisms (bacteria, algae, protozoa, sponges) move without muscles.

    • Use alternative mechanisms of movement.

Role of the Nervous System in Movement

  • Messages sent through the nervous system facilitate body movements.

    • Example: Reflexes send messages quickly from the hand to the brain and back.

  • Reflexes occur in fractions of a second and involve multiple pathways in the nervous system.

  • Everyday activities like walking, running, and dancing rely on nervous system function.

Muscle Contraction

  • Myosin and actin are key proteins for muscle contraction.

  • Muscles are associated with the skeletal system, providing support and facilitating movement.

Muscular Arrangement in the Body

  • Muscles are arranged antagonistically.

    • One muscle contracts while another relaxes to return to original position.

    • Example: Earthworms have longitudinal and circular muscles.

Types of Muscles in Humans

Types of Movements:

  • Flexion and Extension

    • Extensors increase angles between bones (e.g., triceps).

    • Flexors decrease angles between bones (e.g., biceps).

Muscles Attachments:

  • Tendons: Dense connective tissues attaching muscles to skeletal bones.

  • Origin and Insertion: Points of attachment on bones; the belly of the muscle is between these points.

Muscle Types

  1. Skeletal Muscles

    • Striated and voluntary, allowing for conscious control (e.g., muscles of hands and legs).

  2. Cardiac Muscles

    • Involuntary, found in the heart, controlling heartbeats.

  3. Smooth Muscles

    • Involuntary, found in digestive, urinary, and reproductive systems.

Muscle Structure

  • Skeletal Muscles consist of:

    • Muscle fibers (long cylindrical cells), striated appearance due to myofibrils arranged in a pattern of light (I bands) and dark (A bands).

    • Myofilaments made up of actin and myosin generate muscle force.

    • Sarcomere: Basic unit of muscle contraction.

Muscle Contraction Process

  • Relaxed sarcomeres are elongated, contracted ones are shorter due to sliding action of actin over myosin.

  • Cardiac muscles contain intercalated discs for rapid electrical impulse transmission essential for heartbeats.

Skeleton Types

  • Hydrostatic Skeleton: Water-filled cavity providing support for creatures like earthworms.

  • Exoskeleton: External hard covering (like in insects). Consists of chitin, provides structural support but limits growth.

  • Endoskeleton: Internal skeletal structure made of bones and cartilage, found in vertebrates, facilitating growth and movement.

Endoskeleton Features

  • Axial Skeleton: Includes skull, vertebral column, ribs, and sternum.

  • Appendicular Skeleton: Comprises limbs and girdles (pectoral and pelvic) connecting limbs to the axial skeleton.

  • Bone Structure: Includes proximal and distal epiphyses, diaphysis, and both compact and spongy bone regions.

  • Growth plates (epiphyseal plates) determine bone length and fuse at maturity.

Joints and Movement

  • Types of joints in the body allow varying ranges of movement (e.g., hinge, ball-and-socket).

  • Girdles connect axial and appendicular systems and support limb attachment:

    • Pectoral Girdle: Connects arms to the body (clavicle and scapula).

    • Pelvic Girdle: Connects legs to the body and comprises ilium, ischium, and pubis.

Bone Terminology

  • Carpals: Bones in the wrist.

  • Metacarpals: Bones in the hand.

  • Tarsals: Bones in the ankle.

  • Metatarsals: Bones in the foot.

  • Understanding the types and arrangements of bones assists in the comprehension of skeletal movement and support functions in various organisms.