bio chpt 4

ORGANISATION AND MAINTENANCE OF ORGANISMS

12.1 Gas Exchange Supplies Oxygen for Respiration

Objectives

• Comprehend the importance of oxygen for living organisms and the elimination of carbon dioxide.

• Identify the characteristics of an optimal gas exchange surface.

• Recognize the components of the human gas exchange system.

Gas Exchange Process

Respiration refers to a biochemical mechanism that employs oxygen to convert food, mainly glucose, into energy, carbon dioxide, and water vapor. This process can be summarized by the equation:

• Equation: glucose + oxygen → energy + carbon dioxide + water.

This operation is vital for organisms as it correlates the intake of oxygen with the expulsion of carbon dioxide, a method termed gas exchange, which is essential for sustaining pH balance and cellular operations.

Ideal Gas Exchange Surfaces

Effective gas exchange surfaces possess essential properties that enhance the efficiency of oxygen absorption and carbon dioxide removal:

• Thin: This quality promotes swift and effective gas diffusion, allowing gases to traverse minimal barriers.

• Large Surface Area: A more expansive area permits a greater volume of gases to be exchanged at once, maximizing the respiratory function.

• Moist: Gases need to be dissolved in a thin coat of water for optimal diffusion; moisture enhances the rate of gas passage through barriers.

• Well-Ventilated: Consistent airflow upholds concentration gradients, ensuring that oxygen levels remain elevated and carbon dioxide levels minimal in the exchange surfaces.

• Close to Blood Supply: Effective gas transportation occurs when exchange surfaces are closely linked to capillaries, ensuring rapid movement of oxygen and carbon dioxide.

Human Gas Exchange System

The human gas exchange system includes several distinct structures that work together:

• Respiratory Surface: The membranes lining the alveoli in the lungs serve as the primary site for gas exchange.

• Bronchial Tree: This extensive network of air passage tubes branches throughout the lungs, facilitating airflow and filtering inhaled air.

• Blood Supply: The pulmonary artery and pulmonary vein are responsible for circulating oxygen-rich blood and carbon dioxide-laden blood, respectively.

• Ventilation System: Comprising the intercostal muscles and diaphragm, this system actively drives airflow into and out of the lungs through muscular contractions.

12.2 Breathing Ventilates the Lungs

Objectives

• Identify the muscular actions necessary for lung ventilation.

• Assess and evaluate the effectiveness of breathing.

• Understand how exercise influences breathing dynamics.

• Explore supportive measures to enhance lung functionality when needed.

Breathing Mechanism

The mechanics of breathing include:

• Intercostal Muscles: These muscles contract to expand the rib cage, increasing lung volume and allowing air to be drawn into the lungs.

• Diaphragm: This dome-shaped muscle descends during inhalation, further augmenting lung volume and lowering pressure within the thoracic cavity.

• Pleural Membranes: These membranes create a 'stickiness' with pleural fluid, facilitating seamless expansion and contraction of the lungs.

• Atmospheric Pressure: The pressure differential between the atmosphere and the inside of the lungs drives air flow during inhalation.

Breathing Patterns

• Breathing In (Inhalation):

  • Intercostal muscles contract, causing the ribs to move upward and outward.

  • The diaphragm contracts and descends.

  • Decreased lung pressure allows air to flow in due to increased volume.

• Breathing Out (Exhalation):

  • Internal intercostal muscles contract, leading the ribs to move downward and inward.

  • The diaphragm relaxes, reverting to its dome shape.

  • Reduced lung volume raises pressure, expelling air from the lungs.

12.3 Smoking and Disease

Objectives

• Gain insight into the various health implications of smoking.

• Identify harmful substances found in tobacco and their negative health effects.

• Discuss the physiological and psychological challenges presented by quitting smoking.

Smoking Risks

• Chemical Analysis: Tobacco smoke contains more than 1000 harmful chemicals, such as tars, carbon monoxide, nicotine, and heavy metals, all contributing to health complications.

• Health Consequences: Smoking is associated with numerous health problems, including severe lung damage, elevated risks of various cancers (especially lung cancer), cardiovascular diseases, and chronic respiratory conditions like chronic obstructive pulmonary disease (COPD).

Nicotine Addiction

• Physical Addiction: Long-term exposure to nicotine leads to physiological dependence, causing withdrawal symptoms upon cessation of use.

• Psychological Addiction: Behavioral routines linked to smoking can evolve into psychological dependence, creating urges to smoke for comfort or stress relief, complicating the cessation process.

12.4 Evidence Linking Smoking to Disease

Objectives

• Cite statistical data establishing links between smoking and various diseases.

• Understand the construction and significance of epidemiological studies in this context.

Sir Richard Doll's Findings

• Key Studies: Pioneering research led by Sir Richard Doll involving doctors investigated disease patterns among smokers and non-smokers, revealing notable health disparities.

• Statistical Data: Findings from these studies underscored a strong association between smoking and increased early mortality rates, highlighting the public health implications of smoking-related diseases.

13.1 Excretion: Removal of Waste Products of Metabolism

Objectives

• Understand the importance of waste elimination in living cells to maintain homeostasis.

• Identify human waste products and the organs responsible for their excretion.

• Learn about kidney functions and the mechanisms involved in waste elimination.

Excretion Overview

The human body must eliminate toxic waste products resulting from metabolism, including carbon dioxide, urea, and excess salts.

• Kidneys: Principal organs responsible for blood filtration and waste excretion. Each kidney houses approximately one million functional units, called nephrons, which actively filter substances from blood, regulate electrolyte balance, and ensure proper fluid homeostasis.

13.2 Dialysis and Treatment of Kidney Failure

Objectives

• Grasp the principles of body water regulation and its significance.

• Explore various treatments for kidney diseases, especially focusing on dialysis.

Osmoregulation and Dialysis

• Osmoregulation: Refers to the regulation of solute concentrations and water balance in the body, a critical process for maintaining cell environment.

• Dialysis Treatment: This medical procedure artificially removes waste products from the blood when the kidneys can no longer function effectively, carefully managing fluid and electrolyte levels without disturbing normal physiological processes.

14.1 Homeostasis: Maintaining a Constant Internal Environment

Objectives

• Define homeostasis and explain its importance for the overall function of organisms.

• Understand how different organs collaborate to maintain homeostasis.

• Recognize the role of negative feedback mechanisms in achieving physiological stability.

14.2 Control of Body Temperature

Objectives

• Acknowledge the need for stable body temperature concerning enzymatic and metabolic processes.

• Understand how temperature fluctuations directly impact biological activities and cellular functions.

• Learn about the skin's function and various methods the body uses to regulate temperature.

14.3 Control of Blood Glucose

Objectives

• Explain the importance of controlling blood glucose levels to prevent hypoglycemia or hyperglycemia.

• Identify key organs, such as the pancreas, that are crucial for glucose regulation and the modulation of insulin.

14.4 Coordination: The Nervous System

Objectives

• Recognize the necessity for coordinated actions at both cellular and systemic levels.

• Compare the functions of the nervous and endocrine systems in regulating bodily operations and responses.

14.5 Neurones Can Work Together in Reflex Arcs

Objectives

• Explore the significance of reflex actions as essential protective mechanisms for survival in organisms.

• Understand how quick response adjustments aid in decision-making and reactions during stimuli.

14.6 Integration by the Central Nervous System

Objectives

• Describe the role of the central nervous system (CNS) in processing stimuli, enabling prompt responses, and regulating behavioral reactions.

• Differentiate between voluntary (conscious) and involuntary (reflexive or automatic) actions conducted by the body.

14.7 Receptors and Senses: The Eye as a Sense Organ

Objectives

• Investigate how sensory receptors detect stimuli and the functions of sense organs.

• Understand the structure of the eye and how its design supports its visual role, including specialized cells like rods and cones that facilitate visual perception.