Body Organization and Function Concepts

Body Organization and Function

• Organs: Combinations of two or more tissues forming a structure with a specific function.
• Intracellular Fluid: Compartment containing most body water.
• Nervous Tissue: Conducts signals primarily via electrical impulses.
• Potassium: Ion found in greater concentration inside cells than outside.
• Mitochondria: Organelle synthesizing most cellular ATP.
• Phospholipids: Most abundant plasma membrane component.
• Hydrophobic Molecules: Phospholipids makeup a portion of the plasma membrane bilayer.
• Negative Feedback Mechanism: A process where a sensor detects a change, sends info to an integrating center, which in turn signals an effector (e.g., muscle or gland) to counteract the change.

Membrane Transport and Communication

• Transmembrane Protein: Integral protein spanning the membrane, facing both cytosol and extracellular fluid (ECF).
• Passive Transport (Ex: Ion Channels): Movement of sodium through ion channels is passive.
• Direction of Passive Transport: From higher to lower concentration.
• Intracellular Fluid Charge: Negative relative to the outside of the cell.
• Anions: Negative ions (e.g., chloride).
• Active Transport: Requires energy (e.g., ATP).
• Active Transport Carrier Affinity: Higher affinity on the lower concentration side for the molecule being transported.
• Gap Junctions: Allow direct communication between cells in contact.
• Receptor Binding: Intracellular communication through chemical messenger binding to specific receptors.
• Down Regulation: Decreased receptor number leads to reduced target cell response.
• Autocrine Messengers: Bind to receptors on the same cell that released them.
• Hormones: Chemical messengers released into the bloodstream by endocrine glands, affecting remote target cells.

Membrane Potential and Action Potentials

• Membrane Potential: Voltage difference across a membrane.
• Threshold Potential: Membrane potential triggering voltage-gated sodium channels to open.
• Force of Sodium and Potassium Ions: Sodium ions force moves into the cell, while the force on potassium ions to move out of the cell.
• Second Messenger System: Amplifies the response of a first messenger (e.g., hormone).
• Depolarization Phase (Action Potential): Rapid opening of sodium channels.
• Myelin Sheath in CNS: Oligodendrocytes provide myelin sheath in the central nervous system.
• Neurotransmitter Storage: Within synaptic vesicles in axon terminals.
• Synapse Types: Axosomatic synapse occurs between axon terminals and cell bodies.

Nervous System (Autonomic)

• Sympathetic Preganglionic Neuron Origin: Thoracic and lumbar regions of the spinal cord.
• Sympathetic and Parasympathetic Preganglionic Neurotransmitters: Acetylcholine for both.
• Adrenal Medulla Innervation: Innervated by sympathetic preganglionic neurons.

Sensory Systems

• Retina: Neural tissue in the eye including photoreceptors, bipolar cells, and ganglion cells.
• Rods and Cones: Rods are more light-sensitive than cones, crucial for vision in low light.
• Fovea: Area of the eye with highest concentration of cones and highest visual acuity.
• Hair Cells Location: Located in the basilar membrane of the cochlea.
• Sound Wave Transduction: Occurs in the organ of Corti.

Brain and Homeostasis

• Hypothalamus: Regulates homeostasis, involved in thirst, hunger, and thermoregulation.
• Cerebellum: Maintains equilibrium/balance.

Muscle Contraction

• Cross-Bridges: Formed between myosin heads and actin during skeletal muscle contraction.
• Voltage Sensor (Skeletal Muscle): DHP receptor.
• Smooth Muscle Calcium Binding Protein: Calmodulin.

Heart

• Pacemaker Cells: Located in the SA node and AV node.
• Electrical Signal Transmission (Heart): Gap junctions.
• ECG P Wave: Represents atrial depolarization.

Acid-Base Balance

• Fast Acid/Base Compensation: Chemical buffers.
• Most Effective pH Compensation: The kidneys.

Respiratory System

• Intra-Alveolar Pressure and Air Movement: Air moves out of the lungs when intra-alveolar pressure exceeds atmospheric pressure.
• Gas Exchange: Simple diffusion facilitated by alveoli.

Fluid Balance

• Hypersomatic Fluid and Cells: Consumption of a hypersomatic solution causes cells to shrink due to an increase in extracellular fluid osmolarity.

Endocrine System

• Posterior Pituitary Hormone: Oxytocin.
• Active Thyroid Hormone: T3.
• Childbirth and Oxytocin: Cervical stretching releases oxytocin, stimulating uterine contractions.
• Progesterone in Pregnancy: Maintains uterine endometrium during pregnancy.
• ADH and Plasma Volume: Decreasing plasma volume increases ADH secretion.
• ADH and Collecting Duct Water Reabsorption: ADH causes the insertion of water channels, increasing water reabsorption.

Digestive System

• Gastric Acid Secretion: Parietal cells.
• Pepsinogen Secretion: Chief cells.
• Glucose Storage: Glycogen.
• Amino Acid Storage: Proteins.
• Fatty Acid Storage: Triglycerides.

Blood Pressure

• High Blood Pressure Prevalence: Approximately 25% of Americans.

Renal System

• Tubules and Excretion: Material entering renal tubules is excreted unless reabsorbed.
• Glomerular Filtration: Non-selective renal process.

Other

• Endocrine Glands: Ductless glands secreting hormones into the bloodstream.
• Smallest Living Units: Cells.
• Homeostasis: Maintaining the internal environment for life primarily through negative feedback.
• Force Determining Ion Movement: Electrochemical gradient.
• NA+/K+ Pump: Primary active transporter.
• Passive Transport Mechanism: Movement of a molecule down its concentration gradient with the aid of a protein carrier.
• Heroin Overdose Treatment: Opioid antagonist, such as naloxone (Narcan).
• Enzyme for Starch Breakdown: Amylase.
• Enzyme for Fat Breakdown: Lipase.
• First Mobilized Nutrient: Glucose.