Biology: Homeostasis and Body Systems

Course Information

• Course Title: Human Physiology
• Course Code: BIOL 2052
• Instructor: Dr. Cristina V Dieni
• Email: [email protected]
• Phone: 942-4291, ext. 2248
• Office: BGSC213
• Office Hours: Tuesday 10-12, Thursday 13-15, by appointment

Homeostasis

• Homeostasis is the dynamic maintenance of the internal environment, ensuring survival and proper function.
• Defined as the relatively constant internal conditions despite external fluctuations.
• It's a necessary prerequisite for organism survival.

Organism and Homeostasis

• All body tissues and organs contribute to maintaining homeostasis.
• Stable conditions are maintained through balanced functions of organ systems.

Organ Systems Interrelationships

• Cells depend on organ systems to meet their needs.
• Organ systems work together to perform essential life functions.

Homeostatic Regulation

• Homeostatic regulation involves a receptor, afferent pathway, control center, efferent pathway, and effector.
• A receptor detects a change, sends information to a control center, which processes the info and sends instructions through an efferent pathway to an effector.
• Effectors cause a response that either opposes or enhances the initial stimulus.

Feedback

• Feedback is the signal sent by the effector.
• Negative feedback opposes a stimulus.
• Example: Decrease in blood glucose and blood pressure
• Positive feedback reinforces a stimulus.
• Example: Uterine contractions during childbirth, blood clotting, and protein digestion.
• A body temp of 100.2°F causes further increase

Negative Feedback - Temperature Regulation

• Thermoreceptors in skin detect changes in temperature and send messages to the hypothalamus.
• Hypothalamus responses include sweating, vasodilation, piloerection and shivering to regulate body temperature.

Positive Feedback - Childbirth

• Hypothalamus triggers the release of oxytocin, leading to uterine contractions during childbirth.
• Positive feedback strengthens the stimulus, amplifying the contractions until delivery occurs.

Metabolism

• Metabolism encompasses all chemical reactions within the body.
• Catabolism: breaking down complex molecules.
• Anabolism: building complex molecules from simpler molecules.
• Example reactions are given.

Energy

• Chemical reactions involving energy changes.
• Two principal forms: kinetic (energy of motion), and potential (stored energy).
• Chemical energy is potential energy stored in chemical bonds.

Conservation of Energy

• Energy is neither created nor destroyed but transferred from one form to another.
• Chemical reactions release or absorb energy.
• Exergonic reactions release more energy than they absorb, catabolic processes.
• Endergonic reactions absorb more energy than they release, anabolic processes.

Enzymes

• Enzymes are protein catalysts essential to many living processes.
• Enzymes are highly specific and highly efficient, catalyzing specific reactions.
• Enzyme activity is affected by temperature, substrate concentration, pH, and other factors.

Enzymes as Catalysts

• Enzymes have an active site where substrates interact and catalyze the reaction.
• Reaction rate, factors influencing enzyme activity.

Enzyme Activity

• Various factors, like substrate concentration and other modulators (both competitive and allosteric), affect enzyme action.

General Physiology: How Cells Communicate

• Different types of cell communication, such as gap junctions, paracrine and autocrine signals, nerve transmission (neurotransmitters), hormonal transmission (hormones), and neuro-hormonal transmission.

Cell Membrane

• The cell membrane plays a critical role in maintaining cellular environment and communication.
• The composition and structure of the cell membrane are important factors for cell function.

Fluid Composition

• Intracellular and extracellular fluids differ significantly in ion composition, including sodium, potassium, and other electrolytes.