Anatomy, Physiology, and Homeostasis

• Physiology studies how a normal body functions, describing how various systems work to maintain life and health.
• Anatomy studies the body's structure and the physical relationships between body parts.

Homeostasis

• The maintenance of constant conditions in the body's internal environment is called homeostasis.
• Internal environment is equal to extracellular fluid (ECF).
• ECF composition is the same throughout the different parts of the body because of:
  • Rapid exchange of solutes and water between blood and interstitial fluid.
  • Rapid blood circulation.
  • Proximity of almost every cell to a capillary.
• Factors regulated homeostatically include:
  • Nutrient molecule concentration
  • Oxygen and carbon dioxide concentration
  • Waste product concentration
  • pH
  • Water, salt, and electrolyte concentration
  • Volume and pressure
  • Temperature
• Homeostatic regulation involves:
  • A receptor (receives information about environmental changes)
  • A control/integration center (receives and processes information)
  • An effector (responds to commands from the control center, opposing or enhancing the stimulus)
• Interdependent cell relationships, body systems, and homeostasis are important.
• Homeostasis is essential for cell survival.
• Body systems maintain homeostasis, and cells make up body systems.
• This relationship serves as the basis for contemporary understanding of physiology.

Homeostatic Control Systems and Body System Contributions

• Circulatory System:
  • It transports materials from one part of the body to another.
• Digestive System:
  • Dietary food is broken down into smaller molecules for use in the body.
  • It transfers water and electrolytes to the external environment.
  • It eliminates undigested food residues to external environment in faces.
• Respiratory System:
  • It obtains O2 and eliminates CO2 to the external environment.
  • It is responsible for the maintenance of proper internal pH.
• Urinary System:
  • It removes excess water, salt, acid, and other electrolytes from plasma and eliminates them in urine.
• Skeletal System:
  • Provides support and protection for soft tissues and organs.
  • Acts as a storage reserve for calcium.
  • Allows the movement of the body and its parts when used with the muscular system
  • Bone marrow is the main source of all blood cells.
• Muscular System:
  • Moves bones
• Integumentary System:
  • Acts as a protective barrier.
  • Regulates body temperature.
• Immune System:
  • Defends against foreign invaders of the body and against cancerous body cells.
  • Paves way for repairing or replacing injured or worn-out cells.
• Nervous System:
  • Controls and coordinates bodily activities that need quick responses.
  • Detects and triggers reactions to changes in the external environment.
• Endocrine System:
  • Secretory glands of the endocrine system regulate activities.
  • Controls the concentration of nutrients by modulating kidney functions.

Homeostatic Control Systems

• Reproductive System:
  • Not essential for individual survival of the body or cells
  • Essential for survival of the human species as a whole

Control Systems

• Intrinsic Controls:
  • Local controls that are inherent in an organ.
  • Operate in all cells to help control intracellular function as well as extracellular function.
• Extrinsic Controls:
  • Regulatory mechanisms initiated outside an organ.
  • Operate throughout the entire body to control interrelations between organs.
  • Accomplished by the nervous and endocrine systems.

Control of Homeostasis

• Nervous Mechanisms:
  • Rapid regulatory mechanism that regulates body functions through nerve impulses carried by nerve fibers.
  • ABP (arteriol blood pressure) is regulated by vasomotor center
• Hormonal Mechanisms:
  • Slow regulatory mechanism
  • Regulates body functions by hormones released from the endocrine glands.
  • Plays a part in maintain glucose level constant.

Feedback Control

• Negative Feedback:
  • The resultant effects of a function inhibits that function.
  • Oppose an initial change
  • Regulation of CO2 in blood by lung occurs, arterial blood increases and pulmonary ventilation increases.
  • ABP is regulated by VMC, increased ABP inhibits VMC, inhibits heart + vasodilatation of the blood vessels.
  • With increased above normal blood glucose, insulin hormone is secreted to maintain its normal level.
• Positive Feedback:
  • The resultant effects of a function increases its effect.
  • Amplifies change
  • During childbirth (parturition), the baby's descent stretches the uterine cervix, leading to uterine contraction and further descent.

Disruptions in Homeostasis

• Lead to illness and death.
• Pathophysiology results from abnormal functioning associated with disease.

Levels of Organization

• The basic living unit of the body is the cell.
• Each cell type is specially adapted to particular functions.

Total Body Water (TBW)

• TBW = 60% of total body weight.
• Divided into:
  • Intracellular fluid (ICF) 40%.
  • Extracellular fluid (ECF) 20%.
  • Interstitial fluid (ISF) which is 15%.
  • Plasma which is 5%.
• Physiological variations in TBW:
  • Higher ~75% in young infants.
  • Lower ~50% in females due to higher fat content.
  • Lower in obese individuals.
  • Lower in old age.

Effects of Water Loss

• 1% loss of TBW leads to thirst sensation
• 5% loss of TBW leads to dehydration
• More than 20% loss of TBW leads to death

Explore the relationship between anatomy and physiology, and the importance of homeostasis in the human body. Learn about homeostatic control systems, the role of effectors, and how body systems maintain balance. Understand negative feedback mechanisms and hormonal regulation in maintaining homeostasis.