Biology Chapter: Maintaining Life and Homeostasis

Maintaining Life

• Maintaining boundaries: The internal environment remains distinct from the external environment.
• Movement: Includes both external and internal movement.
• Responsiveness: Ability to react to stimuli.
• Digestion: Breakdown of food substances.
• Metabolism: All chemical reactions in the body.
• Excretion: Elimination of waste products.
• Reproduction: Production of new cells or organisms.
• Growth: Increase in size.

Survival Needs

• Nutrients: Used for energy and cell building.
• Oxygen: Required for chemical reactions.
• Water: Most abundant chemical in the body.
• Normal body temperature: Essential for chemical reactions.
• Atmospheric pressure: Needed for breathing.

Homeostasis

• Homeostasis is the ability to maintain a relatively stable internal environment despite external changes.
• It is important for maintaining normal body function.

Anatomical Position

• Body erect, feet slightly apart, palms facing forward.
• Important for directional terms, referring to the body.

Body Cavities

• Dorsal Body Cavity: Contains the brain and spinal cord.
• Ventral Body Cavity: Contains the thoracic and abdominopelvic cavities.

Plasma Membrane

• Composed of a phospholipid bilayer with embedded proteins.
• Controls what enters and exits the cell.

Cell Structure

• Nucleus: Contains DNA, the cell's genetic material.
• Cytoplasm: The fluid inside the cell, where the organelles reside.
• Organelles: Specialized structures that perform specific functions within the cell.

Membrane Transport

• Passive processes: Movement of substances across the membrane without cellular energy input.
• Active processes: Movement of substances across the membrane requiring cellular energy input.

Sodium-Potassium Pump

• An active transport mechanism that pumps sodium ions (Na+) out of the cell and potassium ions (K+) into the cell.
• Important for maintaining cell membrane potential.

Body Tissues

• Epithelial tissue: Covers surfaces, lines cavities, and forms glands.
• Connective tissue: Supports and protects, binds together tissues.
• Muscle tissue: Responsible for movement.
• Nervous tissue: Transmits impulses.

Connective Tissue

• Bone: Most rigid connective tissue.
• Cartilage: Supporting tissue with a flexible matrix.
• Dense connective tissue: Strong, fibrous tissue found in tendons and ligaments.
• Loose connective tissue: Contains more cells with less dense matrix.
• Blood: Fluid connective tissue.

Matter and Energy

• Matter: Anything that takes up space and has mass.
• Energy: The ability to do work.
• Kinetic energy: Energy in motion.
• Potential energy: Stored energy.

Forms of Energy

• Chemical energy: Stored within bonds of molecules.
• Electrical energy: Movement of charged particles.
• Mechanical energy: Energy associated with movement.
• Radiant energy: Energy that travels in waves.

Composition of Matter

• Elements: Fundamental units of matter.
• 96% of the body is made from four elements: oxygen, carbon, hydrogen, and nitrogen.
• Atoms: Smallest unit of an element.
• Molecules: Two or more atoms joined together.
• Compounds: Two or more different atoms joined together.

Inorganic Compounds

• Lack carbon.
• Tend to be small and simple molecules.
• Include water, salts, and many acids and bases.

Organic Compounds

• Contain carbon.
• Large, covalent molecules.
• Include carbohydrates, lipids, proteins, and nucleic acids.

Bone Markings

• Surface features that serve as points of attachment for muscles, tendons, and ligaments, or mark the passage of blood vessels and nerves.

Synovial Joints

• Freely movable joints that contain synovial fluid.
• Types: plane, hinge, pivot, condylar, saddle, ball-and-socket.

Skeletal Muscles

• Responsible for all types of body movement.
• Types: skeletal, cardiac, and smooth.

Skeletal Muscle Activity

• Five golden rules of skeletal muscle activity:
  • All skeletal muscles cross at least one joint.
  • The bulk of a skeletal muscle lies proximal to the joint crossed.
  • All skeletal muscles have at least two attachments: the origin and the insertion.
  • Skeletal muscles can only pull; they never push.
  • During contraction, a skeletal muscle insertion moves toward the origin.

Interactions of Skeletal Muscles

• Prime mover/agonist: The muscle primarily responsible for a movement.
• Antagonist: The muscle that opposes or reverses a prime mover.
• Synergist: The muscle that aids a prime mover in a movement or reduces undesirable movements.
• Fixator: Specializes synergists that hold a bone still or stabilize the origin of a prime mover.

Motor Units

• Consists of a motor neuron and all the muscle fibers it stimulates.

Events at the Neuromuscular Junction

• Motor neuron releases acetylcholine (ACh), a neurotransmitter, which diffuse across the synaptic cleft and bind to receptors on the sarcolemma.
• Sodium ions enter the muscle cell, causing depolarization and generating an action potential.
• Acetylcholinesterase breaks down ACh, ending the muscle contraction.

The Cross Bridge Cycle

• A series of events that allow muscle contraction to occur.
• Steps: cross bridge formation, the power stroke, cross bridge detachment, reactivation of myosin head.

Contraction of a Skeletal Muscle as a Whole

• Graded responses are different degrees of skeletal muscle shortening.
• Muscle fiber contraction is “all-or-none.”
• Graded responses can be produced by changing the frequency or number of muscle cells being stimulated.

Types of Muscle Contractions

• Isotonic: Muscle shortens and movement occurs (“same tone”).
• Isometric: Muscle tension increases without muscle shortening (“same measurement / length”).

Muscle Tone

• State of continuous partial contractions.
• Results from different motor units being stimulated in a systematic way.

Effect of Exercise on Muscles

• Aerobic exercise: Strengthens, more flexible, and more resistant to fatigue.
• Resistance exercise: Increases muscle size and strength - individual muscle fibers enlarge.