Medical Physiology: Human Body Functions

• This unit explains the mechanisms of the human body's functions in health and disease.
• Applied human physiology builds on knowledge from the Level 4 unit Human Anatomy & Physiology.
• This unit provides a basis for understanding the relationships between humans and the biosphere.

Learning Objectives

• Acquire in-depth knowledge of human physiology.
• Understand the significance of homeostasis.
• Study cardiovascular, respiratory, kidney, neurology, endocrine, gastrointestinal, and bone physiology.

Unit Information

• The course code is BHS026-2, titled Medical Physiology.
• The unit co-ordinator is Dr Ria Diakogiannaki.

Unit Overview

• Lecture 1 introduces the orientation and organization of the human body.
• Lectures 2 and 3 cover cardiovascular physiology.
• Lectures 4 and 5 focus on respiratory physiology.
• Lecture 6 discusses body fluid homeostasis.
• Lecture 7 is dedicated to bone physiology.
• Lectures 8 and 9 explore gastrointestinal physiology.
• Lecture 10 covers the endocrine system.
• Lecture 11 focuses on nervous system physiology.
• Lecture 12 covers kidney anatomy and physiology.

Timetable

• There are 12 lectures in weeks 39-49, plus 2 online.
• Friday lectures are from 1-3pm in G101.
• There are 5 tutorials in weeks 41, 43, 45, 47 and 49.
• Friday tutorials are from 3-4pm in G101.
• There are 2 practicals on Monday Oct 14th and Tue 15th; 10am-1pm or 2-5pm.
• Assessment 1 involves data analysis focusing on blood pressure and lung capacities.

Assessments

• All assessments are compulsory and must be submitted on time.
• The data exercise is worth 40% focusing on blood pressure and lung capacity.
• The exam is worth 60%, consisting of short essay questions in a 1-hour format, date is TBC.
• Assessment 1 requires submission by 10am Friday 1st November 2024.

Assessment 1 Details

• An assessment brief, protocol, data for analysis and written instructions will be provided.

BREO (Blackboard Resource Environment Online)

• This is a central online platform
• It provides unit information, lecture notes, assessment instructions, assessment submission links, announcements, and reading lists.
• The website address is www.breo.beds.ac.uk.

Physiology in the News

• The 2023 Nobel Prize in Physiology or Medicine went to Katalin Karikó and Drew Weissman.
• The prize recognizes their development of effective mRNA vaccines against COVID-19 dating back to as early as 2020.

Lecture Outline

• Major themes in physiology will be discussed.
• Body water and its distribution between compartments will be explained.
• The chemical composition of the body will be reviewed.
• Coordination of organ systems will be detailed.
• Homeostasis including both negative and positive feedback mechanisms.

Major Themes in Physiology

• Structure/function relationships are very important.
• Compartmentalization is essential.
• Communication within the body is key.
• Biological energy use is a major theme.
• Homeostasis and control systems are crucial.

Compartmentalization

• Compartments are biological structures and spaces within organisms.
• They can be either advantageous or disadvantageous.

Basic Cell Structure Basics

• Cells are composed of cytoplasm, the nucleus, a cell membrane, cytosol and organelles.
• Organelles are either membranous or nonmembranous.

Energy and Cellular Metabolism

• Growth, repair, and maintenance require energy.

Body Water

• Water is the primary solvent in cells.
• Hydrophilic molecules dissolve in water.
• Hydrophobic molecules do not dissolve in water.
• Amphiphilic molecules have both hydrophilic and hydrophobic parts.
• Body water includes intracellular and extracellular fluid.
• Extracellular fluid includes plasma and interstitial fluid.

Body Water Distribution

• Intracellular fluid comprises 67% (28 liters) of body water.
• Intercellular fluid makes up 27% (11.2 liters).
• Plasma accounts for 7% (2.8 liters).

Solutions

• Water is the physiological solvent in biological systems.
• Solutes dissolve in water.
• Solvents dissolve solutes
• Solutions have a solute dissolved in solvent.
• Solubility is the ease of dissolving.

Fluid Compartments

• Fluid distribution of solutes includes extracellular and intracellular fluid.
• Extracellular fluid makes up 33% of bodily fluids.
• Intracellular fluid makes up 67% of bodily fluids.

Chemical Composition

• The major elements in the body by weight are oxygen (65%), carbon (18%), hydrogen (10%), and nitrogen (3.4%).
• Mineral elements include sodium (0.17%), potassium (0.28%), chloride (0.16%), calcium (1.5%), magnesium (0.05%), phosphorus (1.2%), and sulphur (0.25%).
• Trace elements include iron (0.007%) and zinc (0.002%).
• Principal organic constituents are carbohydrates, fats, proteins and nucleic acids.
• Water accounts for 60% of adult male body weight and 50% of adult female.

Combination Biomolecules

• Lipoproteins transport molecules in the blood.
• Glycoproteins form membrane structures.
• Glycolipids are membrane receptors.

Coordination of Organ Systems

• The skin separates internal and external environments.
• Internal fluids bathe all cells and differ in composition from the external environment.
• The circulatory system transports materials to and from all parts of the internal environment.
• Some organs facilitate material exchange between internal and external environments.
• Cells of organs exchange materials with each other.

Integration of Body Functions

• Local control processes occur when cells in the vicinity initiate a response to a change.
• Reflex control processes occur when cells at a distant site control the response.

Homeostasis Definition

• Claude Bernard (1813-1878) called it "The fixity of the internal environment is the condition for free life."
• Walter Cannon (1929) coined the term Homeostasis.

Homeostasis

• The word is derived from the Greek words homeo (constant) and stasis (stable).
• Electrolyte balance depends on the integration of circulatory, excretory, and behavioral physiology.
• Water recycling and extracellular fluid/plasma balance relies on the loop of Henle and vasopressin regulation.
• Osmolarity regulation depends on aldosterone and angiotensin pathways.
• Respiration, proximal tubule, and collecting duct cells reabsorb or excrete H+ and HCO3- to balance pH.
• Hemostasis or haemostasis stops bleeding.

Homeostasis Details

• Homeostasis involves maintaining the internal body composition within strict limits.
• This includes ion concentrations, pH, osmolarity, and temperature.
• Regulatory mechanisms respond to external and internal environmental changes.
• Cardiac muscle cell contraction is an example, impacting intracellular and extracellular sodium, potassium, and calcium.
• Extracellular potassium levels must be kept within a narrow range for proper function.

Internal Homeostasis Components

• Requires maintaining the correct concentration of oxygen and carbon dioxide.
• Regulating the pH of the internal environment.
• Ensuring proper levels of nutrients and waste products.
• Regulating salt and electrolyte concentrations.
• Controlling the volume and pressure of extracellular fluid.

Homeostasis

• Involves the body's ability to maintain a relatively constant internal environment.
• This occurs despite changes in the external environment.
• It is a dynamic state where internal conditions vary within narrow limits.
• Virtually, all organ systems help maintain it.

Homeostatic Control Mechanisms

• Body temperature is influenced by the integumentary, muscular, cardiovascular, and nervous systems.
• Nutrient absorption, storage, distribution, and urine control are key.
• Organ Interaction - Oxygen, carbon dioxide, and cardiovascular systems are relevant.
• Blood pressure is influenced by cardiovascular, nervous, and endocrine systems.

Homeostatic Control Mechanisms - Required components

• Communication is essential for maintaining homeostasis and balance.
• The nervous and endocrine systems are major communication systems.
• These mechanisms need 3 components, a Receptor, Control Centre and Effector

Control Systems

• Open systems are linear and lack feedback.
• Closed systems have two components, involving a sensor and an effector.
• Physiological systems use feedback mechanisms to maintain internal environment.

Maintaining Normal Limits

• Receptors receive stimuli, send via nerve pulses to a control center.
• The control center issues commands to an effector to help manage responses.
• Control measures can be done either directly or indirectly.
• Negative feedback negates the stimulus
• Positive feedback reinforces the stimulus.

Homeostasis Achievement

• Regulatory mechanisms act to maintain a desired concentration range for each body chemical.
• Glucose is maintained through insulin secretion to help regulate blood glucose levels.
• The regulation is termed negative feedback.
• It involves maintaining a given variable (concentration, temperature, pressure) within a defined range.

Homeostatic Control Mechanisms

• Homeostatic control needs at least 3 interdependent components.
• These are namely, a receptor, a control centre and an effector (that releases product to bring variable back within range)
• The control centre determines an appropriate response for the variable that has fallen out of range

Mechanisms of Thermoregulation

• Example: Body temperature regulation at a human set point of 37°C.
• Hypothalamus senses body temperature and signals need for "heater".

Feedback Mechanisms

• Homeostasis is maintained through negative feedback mechanisms or positive feedback mechanisms.
• Negative feedback mechanisms oppose the response to the stimulus.
• Positive feedback mechanisms enhance the response to the stimulus.

Negative Feedback Systems

• Negative feedback mechanisms are predominant for homeostatic control, mainly to help maintain a range for functions.
• Includes events that need continuous adjustment eg: maintaining blood pressure.

Limitations of Negative Feedback

• Correction is initiated after a variable has been disturbed
• Correction amount depends on magnitude of the error signal i.e. incomplete correction if deviation from set point is too large
• Overcorrection can cause oscillations in the controlled variable.
• These disadvantages are overcome mostly by multiple regulatory mechanisms.

Positive Feedback Systems

• Positive feedback mechanisms control events that are self-perpetuating and explosive.
• These do not control events needing continuous adjustments to promote short-term well-being.
• Production of A encourages production of B, which produces even more of A.

Feedback Loop Examples

• Baby is delivered to decreases stretching of cervix thus breaking the loop.

Feedback Loops

• Positive feedback involves A producing more of B, which in turn produces more of A.
• Negative feedback: A produces more of B, which in turn leads to less of A.

Homeostatic Imbalance

• This results in aging, illness, or disorders to the body.
• It is more of a focus on disorders or diseases due to the breakdown of systems.

Successful and Unsuccessful Compensation

• Lack of homeostasis will result in either illness or death.
• If compensation succeeds we result in wellness, however, when it fails can result in negative effects.

Summary

• Physiology is the study of the normal functioning of parts of a living organism
• The levels of organization in living organisms vary from molecules to a population
• Its key themes are homeostasis, biological energy use, structure-function relationships, and communication among cells.