Human Physiology Quiz

Homeostasis

• Physiology is the study of how the body functions. It emphasizes the body's ability to maintain itself.
• Body functions at different levels of organization work together.
• There are 11 organ systems in the body.
• Body fluid compartments include intracellular fluid (67%) and extracellular fluid (33%), with plasma comprising 7% of body fluid and interstitial fluid 26%.
• Extracellular fluid has a high concentration of sodium and chloride ions. Intracellular fluid has a high potassium concentration.
• Regulation is continuous and responsive to changes.
• Chemical messengers such as hormones act on distant target cells. Paracrine substances act on neighboring cells and autocrine substances act on the same cell that released them.
• Chemical disequilibrium occurs across selectively permeable membranes.
• Homeostasis maintains a stable internal environment despite external changes. It's a dynamic condition, not equilibrium. A normal pH is 7.4.

Chemical Composition

• Major elements (hydrogen, oxygen, carbon, nitrogen) make up 99.3% of the body's atoms.
• Key minerals (7) and trace elements (13) make up 0.7% and <0.01% of the body's atoms, respectively.
• Molecular shapes result from the possibility of rotation around different C-C bonds.
• Amphipathic molecules have hydrophilic and hydrophobic parts.

Cells

• Embryogenesis is the process of an embryo developing from an egg.
• Spherical cell enlargement increases surface area by the square of cell size and volume by the cube of cell size.
• Plasma membranes are a mixture of membrane proteins that can move in the lipid bilayer.
• Three types of specialized membrane junctions include desmosomes (joining cells by strong proteins), tight junctions (impermeable membranes with no extracellular space) and gap junctions (protein channels that connect cytosols).
• Cell organelles include the nucleus (largest, storing genetic info), nucleolus (inside the nucleus, involved in ribosome production), rough ER (protein synthesis), smooth ER (fatty acid and steroid synthesis), ribosomes (in rough ER), Golgi apparatus (modifies and sorts proteins), and mitochondria (produces ATP).

Solutes and Water

• Water moves by osmosis, from low concentration to high solute concentration.
• Movement of water passively can be aided by aquaporins.
• Water movement depends on concentration gradients and requires no ATP.

Cells Signaling

• Cells communicate via:
  • Chemical signals
  • Receptors in target cells
• Ligands are secreted into extracellular fluid by cells.
• Target cells have specific receptors that bind to these signals.
• Responses vary depending on the target cell types.

Skeletal Muscle

• Muscle contraction involves electrical/chemical signals.
• Three types of muscles include skeletal, cardiac, and smooth muscle.
• Sarcomere structure (relaxed = 2.6 μm, contracted = 1.6 μm) and components (actin, myosin, titin) are crucial.
• Muscle fibers contract by the sliding filament theory. Interaction of actin-myosin filaments generates force.
• ATP is essential. Types include slow-oxidative, fast-oxidative-glycolytic, and fast-glycolytic.

Neuromuscular Signaling

• Neurons have dendrites, soma (cell body), axon (carries signals), axon hillock (generates action potentials), and axon terminals to release neurotransmitters.
• Myelin sheaths (Schwann cells in PNS) speed up conduction.
• Electrical and chemical synapses exist.
• Neurotransmitters bind to receptors on postsynaptic neurons, leading to the generation of graded potentials.
• Different types of neurons exist (e.g., sensory, motor, interneurons).
• Synapses: electrical (direct flow), and chemical (release of NT which binds to receptors).

Nervous System

• The CNS includes the brain (encephalon) and spinal cord. The PNS connects the CNS to the rest of the body.
• Neurotransmitters such as ACh, norepinephrine, dopamine, GABA, glutamate, serotonin and histamine are involved in various types of communication and responses. Different types of neurons and glial cells contribute to the function of the nervous system.

Endocrine System

• Hormones are secreted into the bloodstream by endocrine glands to target distant cells.
• Hormones act directly on cells in the body.
• Different hormones have different roles depending on the organs they affect.
• Various hormones and their functions are discussed in terms of their structure, production and effect on the cell or organism.

Cardiovascular System

• Blood contains erythrocytes for O2 transport and leukocytes for immune defense.
• Hematocrit (ratio of red blood cells to total blood volume) can vary.
• Cardiovascular system consists of a pump (heart) and a circulatory system for circulation of blood through the body.
• Blood pressure and heart function are explained.

Respiratory System

• Gases (O2, CO2) are exchanged between the air and blood in the lungs.
• The lungs have specialized structures.
• Pulmonary ventilation is measured. Factors influencing rate and volume include breathing rate and volume.
• Movement of air is explained based on pressure differences.