Cellular Homeostasis

• Physiology is the study of how living organisms function
• It explores the mechanisms operating at different organizational levels, including molecular, cellular, tissue, organ, and system levels
• Physiology emphasizes the dynamic nature of living organisms. It addresses questions of how the body responds to challenges and adapts to changing conditions

Homeostasis

• Homeostasis refers to the maintenance of a stable internal environment
• It is essential for cell function and survival
• Claude Bernard introduced the concept of the "milieu intérieur," highlighting the importance of a constant internal environment
• Walter Cannon coined the term "homeostasis" to describe the regulatory processes that maintain this stability
• Homeostatic control systems regulate various internal parameters, including body temperature, blood glucose, blood pH, and blood pressure

Components of Homeostatic Control Systems

• A receptor detects changes in the internal environment
• An integrating center processes the information and initiates a response
• An effector carries out the response to restore the internal environment
• Negative feedback is the primary mechanism. It reverses the initial change and restores homeostasis
• Positive feedback amplifies the initial change, leading to a rapid change in the system. It is less common than negative feedback

Cell Physiology

• Cells are the basic structural and functional units of the body
• Studying cell physiology is essential for understanding tissue, organ, and system physiology
• Key aspects of cell physiology include membrane transport, cell signaling, and metabolism

Membrane Transport

• The plasma membrane regulates the movement of substances into and out of the cell
• Passive transport does not require energy, including diffusion, osmosis, and facilitated diffusion
• Active transport requires energy (ATP) to move substances against their concentration gradients, including primary and secondary active transport

Cell Signaling

• Cells communicate with each other through chemical signals
• Signals bind to receptors on the cell surface or inside the cell
• Receptor activation triggers intracellular signaling pathways that lead to cellular responses

Metabolism

• Metabolism refers to all the chemical reactions that occur within a cell
• Catabolism breaks down complex molecules to release energy
• Anabolism uses energy to synthesize complex molecules

The Plasma Membrane

• The plasma membrane surrounds the cell and separates the intracellular fluid (ICF) from the extracellular fluid (ECF)
• It is composed of a lipid bilayer with embedded proteins
• The lipid bilayer is primarily composed of phospholipids, cholesterol, and glycolipids
• Membrane proteins have diverse functions, including transport, signaling, and cell adhesion

Membrane Potential

• The membrane potential is the electrical potential difference across the plasma membrane
• It arises from the unequal distribution of ions between the ICF and ECF
• The resting membrane potential for most cells is negative, typically around -70 mV
• Ion channels and ion pumps play critical roles in establishing and maintaining the membrane potential

Ion Channels

• Ion channels are transmembrane proteins that allow specific ions to diffuse across the membrane
• They can be voltage-gated, ligand-gated, or mechanically gated
• Voltage-gated channels open or close in response to changes in membrane potential
• Ligand-gated channels open or close in response to the binding of a specific chemical messenger

Ion Pumps

• Ion pumps are active transport proteins that use ATP to move ions against their concentration gradients
• The Na+/K+ ATPase pump is a primary active transporter
• It maintains the Na+ and K+ concentration gradients across the plasma membrane

Principles of Neural and Hormonal Communication

• The nervous and endocrine systems coordinate and regulate body functions
• The nervous system uses electrical and chemical signals for rapid communication
• The endocrine system uses hormones for slower, longer-lasting communication

Neural Communication

• Neurons are the basic functional units of the nervous system
• Action potentials are electrical signals that travel along the axon of a neuron
• Neurotransmitters are chemical messengers that transmit signals between neurons at synapses

Hormonal Communication

• Hormones are chemical messengers secreted by endocrine glands
• They travel through the bloodstream to target cells throughout the body
• Hormones bind to receptors on or in target cells, triggering specific cellular responses

The Central Nervous System (CNS)

• The CNS consists of the brain and spinal cord
• It integrates sensory information and coordinates motor responses
• The brain is responsible for higher-level functions, including cognition, emotion, and memory
• The spinal cord transmits information between the brain and the peripheral nervous system (PNS)

Brain Regions

• The cerebrum is the largest part of the brain
• It is responsible for conscious thought, sensory perception, and voluntary movement
• The cerebellum coordinates movement and balance
• The brainstem controls basic life functions, such as breathing and heart rate

Spinal Cord

• The spinal cord is a long, cylindrical structure that extends from the brainstem
• It transmits sensory information from the body to the brain
• It transmits motor commands from the brain to the body

Explore the mechanisms maintaining cellular homeostasis. Questions cover the plasma membrane, sodium-potassium pump, feedback mechanisms, hormone receptors, and the role of the medulla oblongata in central nervous system function.