Homeostasis and Physiological Systems

Structural Organization of the Human Body

Lecture outline

• Overview of course organization
• Introduction to human physiology
• Review of structural characteristics and body organization, important for human physiology
• Structure/Function Principles
• Tissue Types
• Organs
• Organ Systems
• Summary

Overview of Course Organization - Unit 1: Foundational Concepts

• The unit covers principles of homeostasis.
• Chemical composition of the body is discussed in Ch. 2. -Overview covers eukaryotic cells, the cell membrane & organelles in Ch. 3.
• Proteins & the human body covered in Ch. 3
• Energy to power biological activities explained in Ch. 3
• Cell Membrane: Regulator of Transcellular Transport & Communication (Ch. 4-5)

Overview of Course Organization - Unit 2

• This unit covers the nervous system in Ch. 6, including:
  • Autonomic NS
  • Somatic NS
• Sensory Systems covered in Ch. 7.
• Muscular System explained in Ch. 9.
• Nervous System Control of Movement (Ch. 10)
• Endocrine System (Ch. 11)

Overview of Course Organization - Unit 3

• Cardiovascular system explored in Ch. 12.
• Immune system discussed in Ch. 18.
• Respiratory System explained in Ch. 13.

Overview of Course Organization - Unit 4

• Renal System covered in Ch. 15.
• Digestive System explained in Ch. 16.
• Whole-Body Metabolism also discussed in Ch. 16.
• Reproductive Systems in Ch. 17.

Introduction to Human Physiology

• Physiology is the study of how living organisms function.
• Concept 1 focuses on the Hierarchy of Structural Organization (Levels of Structural Organization)
  • Molecules cells tissues organs (functional units) organ systems → organism
• Concept 2 explains Integrated Physiological Function.
  • to understand physiology, it is important grasp how changes in function at each level lead to whole- body responses.
• Concept 3 focuses on the Interrelationships between structure (anatomy) and function (physiology).
  • Review cell division and cell differentiation.
• Identify the four cell/tissue types:
  • Muscle cells
  • Neurons: cells of the Nervous System
  • Epithelial cells
  • Connective-tissue cells

Review of Structural Characteristics

• Muscle Tissue Function: Mechanical force generation.

Review of Structural Characteristics - Nervous Tissue

• Neuron Function handles Communication via generation of electrical signals.

Review of Structural Characteristics - Epithelial Tissue

• Epithelial Tissue Functions.
  • Barrier: covers internal, external surfaces.
    • Compartmentalization
    • Structures
      • Basement membrane
      • Basolateral side
      • Apical (luminal) side
      • Tight junctions
  • Selective secretion and absorption of ions, organic molecules
  • Protection
• Note Structure: Function relationships exist.
• Most epithelial tissues line or cover surfaces or body cavities

Review of Structural Characteristics - Connective Tissue

• Connective Tissue Functions.
  • To "connect", anchor, support different parts of the body.
  • Formation of the extracellular matrix: collagen and elastin (protein) fibers, polysaccharides - Scaffolding - Cell signaling

Structural Characteristics - Organs

• Organs are a discrete structure that performs a specific function.
• Organs are often comprised of all 4 cell/tissue types.
  • An example is the heart
• Functional Unit acts as the "working unit" of an organ
  • For example, nephrons act as functional units in kidneys
• Organ systems are a several organs working together to perform an overall function in an organism.
• Multiple organ systems will work cooperatively to maintain overall organismal function.
  • This 'organism' is the human body

Summary - Terms & Concepts

• Key items include:
  • Physiology
  • Organ
  • Functional unit of an organ
  • Organ system
  • Integrated physiological function
• Remember that Structural Organization/Hierarchy flows from cells to tissues, functional units within organs, and eventually to organ systems → organism (human body).
• There are 4 Tissue Types: muscle, neural, epithelium, and connective tissues.
• Epithelial Cell Structures include: basement membrane, basolateral side, apical (luminal) side, tight junctions.
• Understand that you should be able to:
  • Define physiology and describe the levels at which it can be studied.
  • Explain the concept of integrated physiological function, attributing the function to the whole body to numerous internal processes.
  • Describe the organizational (structural) hierarchy of humans: cells to tissues to organs to organ systems and ultimately to organism/whole-body.
  • Identify the four cell/tissue types and the primary functions of each, with specific attention given to epithelial cell characteristics.

Body Fluid Compartments

• Body fluids, or water plus the substances dissolved in it, are localized into 2 compartments.
  • Intracellular fluid compartment (ICF) which is ~2/3  body water.
  • Extracellular fluid compartment (ECF) which is ~1/3  body water. ECF contains:
  • Plasma
  • Interstitial fluid (and interstitium)
• Rule of 60-40-20

Body Fluid Compartments - Typical Values

• An average USA person will have the following traits:
  • F~170lbs 93.5lbs fluid 63lbs ICF 32lbs ECF.
  • M~200lbs 120lbs fluid 80lbs ICF 40lbs ECF.
• It depends on body composition

Body Fluid Compartments - Electrolyte Composition

• Key properties here include:
  • The major ions of the ECF.
  • The Major ions of the ICF.
  • Note distribution of positive, negative ions.

Body Fluid Compartments - Ion/Water Movement

• The key here is the Flux Across Fluid Compartments principle

Body Fluid Compartments - Ion/Water Movement

• The key here is the Steady-state vs. Equilibrium

Summary - Terminology

• Common terms include:
  • Fluid Compartments
  • intracellular (ICF)
  • extracellular (ECF): plasma, interstitium
• Concept of steady state values for physiological function, versus being in equilibrium

Summary - Learning Activities

• This section focuses on the concepts of:
  • Identifying the two main fluid compartments and describing the location of plasma and interstitial volumes.
  • Providing reasonable numbers for the proportion of body water within the intracellular fluid compartment and the extracellular fluid compartment, including the plasma volume
• Identifying the major ions located within the extracellular fluid. - Comparing the composition of the intracellular fluid compartment.  
• Explaining the concept of compartmentalization, recognizing the importance of barriers between compartments that maintain the differences in composition of the various body fluids.
• Knowing why steady-state is not synonymous with equilibrium.

Homeostasis & Homeostatic Control Systems -Definition

• Homeostasis is defined as the process by which physiological variables are kept relatively “stable" despite imposed challenges.
  • Examples of variables that are regulated, and  specific challenges to maintaining stability for each variable are key

Homeostasis & Homeostatic Control Systems -Definition

• Homestasis works by using the concept known as stable. -It must therefore be asked, "What does stable mean?"

Homeostasis & Homeostatic Control Systems - Example

• A good example to use is that of blood glucose regulation. What would happen if glucose not regulated? What are the Challenges to regulation?
• What are the components of the system that keeps blood glucose in homeostasis (Sect 1.5 & 1.6)?

Homeostasis & Homeostatic Control Systems- Example (Cont.)

• Some key things to remember include:
  • Set point: regulated physiological range.
  • steady state vs. equilibrium.
  • Steady-state is achieved by balancing inputs and outputs. In terms of blood glucose, what are the inputs? What about the outputs?

Homeostasis & Homeostatic Control Systems- Integrated Function

• Common aspects include:Regulated variables that can be regulated independently. Regulation of one variable may influence regulation of another.
• An example is temperature regulation, which can affect fluid balance

Feedback & Feedforward Control - Negative Feedback

• Remember that Homeostatic control systems utilize feedback or feed-forward control to regulate physiological variables around set point. A change in a variable away from its set point initiates a response bringing it back towards its set point. This Negative Feedback System
• Includes body temperature regulations

Feedback & Feedforward Control - Positive Feedback

• In contrast, the Positive Feedback System involves:
  • A change in a variable away from the set point causes a chain of events that further increase the change
  • An example is child birth. 
• It only serves homeostasis in a global sense.
  • Consider how?

Feedback & Feedforward Control - Feedforward Regulation

• Feedforward Regulation defined as when the body adjusts a variable prior to any actual change, in anticipation of future needs.
  • Examples are Ventilation at the onset of exercise, and the Salivation prior to a meal

Summary - Terminology

• Common terms include:
  • Homeostasis Dynamic constancy
  • Set Point Steady State (vs. Equilibrium)
  • Negative Feedback Positive Feedback
  • Feedforward Regulation

Summary - Learning Activities

-Key concepts covered here are: - Defining homeostasis, dynamic constancy of physiological variables, set point, steady state, and equilibrium. - Explaing the integrated nature of homeostatic control systems (regulation of one variable affect regulation of another) -Explaing how negative feedback, positive feedback, and feedforward systems are similar and h

Homeostatic Control Systems - Overview

• It's important to remember that:
• Homeostatic control systems regulate variables via reflexes and/or local responses. - Cells must communicate with one another in both instances.

I. Components of Control Systems -Homeostatic Reflexes

• Key point: unlearned control systems linking stimuli with one (or more) re¬sponses, mediated by a reflex arc. - Components of Reflex Arc: -Stimulus -Receptor -Afferent Pathway -Integrating Center -Efferent Pathway -Effector(s) -Response(s)
• Consider the case of remember when Homeostasis is integration" multiple stimuli, multiple effectors

I. Components of Control Systems - Local Homeostatic Responses

• Local Homeostatic Responses include that: - It is like a reflex, links a stimulus to a response -It is unlike a reflex, occurs entirely within a local area. -There is no afferent pathway, no integrating center, no efferent pathway. -Hyperemia for exampe.

II. Intercellular Chemical Messengers - Overview

• Both reflexes and local responses require cellular communication accomplished via intercellular chemical messengers. - What general process by which cells "talk" to one another? - It's important to keep categorized by which cells release them and where they are released. -Remembering that same messenger can play multiple roles are .

II. Concepts of Chemical Messengers - Hormones

• Hormones are categorized as a Class of Intercellular Chemical Messengers

II. Concepts of Chemical Messengers - Nerve Cells

• Neurotransmitters are categorize as a Class of Intercellular Chemical Messengers

II. Concepts of Chemical Messengers - Paracrine Agents and Autocrine Agents

• Paracrine agents are categorized as a Class of Intercellular Chemical Messengers
• Autocrine agents categorized as a Class of Intercellular Chemical Messengers

Summary of Cell Communication

• Key aspects:
• Homeostatic reflex
• Local homeostatic response
• Hormone
• Neurotransmitter
• Paracrine/autocrine agents
• It is important to remember all of these -Define a homeostatic reflex, identify the components of a reflex arc, and explain how reflex arcs contribute to homeostasis. -Compare and contrast reflexes and local homeostatic responses, describe the role that each plays in homeostasis of the organism -Explain how intercellular chemical messengers can contribute to homeostasis, identify and define the four different types.

Organism - Characteristics of Homeostatic Processes

• Homeostatic processes function at all physiological levels, but understanding how these process
• processes are integrated at the organismal-level is ultimately the key to understanding human physiology.

Organism. - Homeostatsis and the Evolutionary Processes

• Key points in evolution include:
• Different homeostatic control systems have been acquired through evolution
  • Different species have evolved different systems to deal with similar challenges/environments

Organism. - Adaptation and Acclimation of Evolved Systems

• These evolved systems possess the ability to change in response to chronic conditions Examples and Characteristics are useful parameters
• We will not get bogged down in the specific terminology (i.e. adaptation/acclimatization) that the textbook uses to describe this acquisition and change

Learning About Biological Rhythms

• The biological rhythm of the body is a feedforward regulation.
• Circadian rhythms cycle once every 24 hours.
  • Wakefulness, Body temperature, various hormones have a ryhtmic cycle
• Hypothalamusis the location of the primary pacemaker for these rhythms.

balancing subsantances in the body

• Key aspects involve: -Many systems balance addition and removal of a given substance from a pool within the body. -Focus on the net gain ,and net loss of materials. Also consider the examples of substances that area regulated
• This helps explain the flow and distribution within the body

Understanding Net Gain and Loss

-Consider that:

• Daily Na+ gain consists of roughly 8.5 grams from Food.
• Net loss is about the same.
• TOTAL ≈ 8.5 grams: -Sweat ≈ 0.25 g. -IOWA. -Feces ≈ 0.25 g. -Urine ≈ 8.0 g.

Understanding Net Gain and Loss Balance and Changes

-Loss> gain is a negative balance.

• Gain > loss  = positive balance.
• Loss = gain = stable balance.

Study Summary

• It helps to understand that the summary for this section involves:
  • Biological Rhythm (& Circadian Rhythms).
  • Hypothalamus(a body structure).
  • Substance Pool.
  • Negative Stability or positive net balance.
• You should be able to:
  • Understand that homeostatic control systems are acquired through evolution, and these systems can be modified due to chronic changes in stimuli/ environment
  • Explain the concept of biological rhythms and provide examples, identify the structure that typically coordinates biological rhythms.
  • Define the "pool" of a substance as the amount available for use and recognize that the substance can be added or removed from the pool.
  • Know how changing inputs and outputs of the substances can induce negative, positive, or stable balance

General Principles of Physiology

• Remember, Physiological processes are dictated by the laws of chemistry and physics.

Atoms and Elements

• The atom is the smallest freely existing unit of matter.
• Key chemistry properties include":
  • atomic Structure
  • Nucleus: protons (+), neutrons
  • Orbitals (shells): electrons (-) Atomic number
  • Atomic mass
• Key physiological traits include": -The human body is composed of elements -Atomic, variants can be measured and used clinically.
  • Electrons in orbitals are important in forming molecular bonds.

Atomic and Elements - Atomic Vatrima=ts

• The human body is composed of 24 essential elements
  • These include many major elements.
  • Mineral Elements
  • Calcium, potassium, and sodium. -Trace (mineral) Elements

Studying Variation in Atomic Compounds

• Variants of many elements exist based upon neutron #
  • Isotopes
    • ex: Examples:1Η, 2Η, 3Η
      • 12C, 13C, 14C
• Radioisotopes tend to be unstable - Used in Cancer treatments - Diagnostic medicine - ex: Examples: doubly-labeled water(2H₂18O), 18F-FDG
• If an atom gains or losses an electron, it becomes a ION. llon is when an atom that gains or loses one or more electrons in order to achieve a full outer shell, resulting in a net charge cations, anions. anolyte ion and solution.
• Ions affect the body - for example exercising = we sweat causing water electrolyte losses from the body (that distrupts homeostasis)

Understanding Molecules

• Two or more atoms bonded together is a Molecule. -Atomos within a molecule can be held together by covalent bonds or ionic bonds.
• Covalent bonds can either be non polar or polar covalent bonds. molecules that are non polar behave differently than ones that are polar. -Hydrogen bonds - attraction between a partially positive H in one molecule with a partially negative atom in another molecule (think DNA)

Ions in the Body

• Molecules, just like atoms, can gain or lose electrons to become ions
• Electron from a H can be captured releasing a H+ and forming an onion. alternately, a molecule can bind a H being becoming a cation. free radicals molecules with an unpaid electron in out most orbital formed naturally within body exposure to radiation to toxins or reactive oxygen species.
• ROS can lead to oxidative stress and damage to macromolecules but they also important signalling molecules.

Solutions and pH

• The majority of your body is made up of water, and physiology occurs within an aqueous environment.
• A solution is comprised of":
  • Solvent:liquid component of a mixture
  • Solute: substance dissolved in liquid
  • Example: blood glucose concentration
• A molecular solubility focuses on how well solute dissolves in a solvent
  • Polar and ionic molecules dissolve in water:hydrophilic, lipophobic.
• Non-polar compounds arc generally insolvable in water:hydrophobic, lipophilic.
  • Compounds with Polar region and non polar regions, arc aphipathic.
• The physiological implications of this affect transport in blood ,and molecule movement across cell membranes.
• In addition to being the solvent of the body, water is also involved in":making and breaking covalent bonds
• When a H atom loses an electron, it becomes a single, free proton. the "H plus" relates to acidity, is measured by pH. pH can have impacts in proteins and different parts of metabolic system
  • Example: acidosis during exercise alters enzyme activity of metabolic pathways to increase ATP production. this leads to disruption

Terms and Concepts

1. Atom. element. isotope electrolyte, isoton cat ion anton, 2. Molecule.covalent bond. ionic bond, polarity, non polar bond, polar bond .hydrogen bond free radical "ROS"oxidative.stress. 3.Solution:solute, solvent, solution, colubility, concentration, hydrophobic. lipophilic, hydrophilic, amphipathic, pH. 4. List the four major elements that comprise human body identify the major cations and onions that are found and the human body. 5. Identify the two types of chemical bonds that can form molecules

• The four major molecules in the body are:
  • carbon, oxygen, hydrogen and nitrogen.
  • The major catlions are: Ca++
  • The molecules in which the most frequently occurs ion forms of elements arc called the bodies and it can get from the polar as they get from the polar covalent bonds and the non-polar covalent bonds.

Understanding Organics

• What area we made of? What has a classification scheme?*: - Basic model - 2 compounds fat - Fat mass.
• What are the four categories in molecules in human body?*: 1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic acids

Carbohydrates

• Carbohydrates make up to only 1% of body weight ,and its Function helps cellular energy, and Production.
• In part they are made of adenosine triphosphate. these structures are important: - During exercise -As the primary energy substrate in certain tissues examples
• Nervous system, Retina, red blood cells
• Carbohydrates are part of their Extracellular matrix ,and its also aids in cell recognition, cell signalling.

Carbohydrates - Structure

• Structure includes Cₙ(H₂O)ₙ
• Most CHO contains hydroxyl. polar and non-polar?
• Subunits consist only of one type calledMonosaccharides. ex':
  1. Glucose
  2. Galactose
  3. fructose
• Disaccharides -2 monosaccharides which linked via then dehydration reactions and then hydrolysis reactions.
• Polysaccharides; Linked mono saccharides, CHO storage, plant starch, Primary animal polysaccharide, liver and skeletal muscle, note branching ,existance"

practical examples of a polysaccharide (glycogen):

• Daily gain. • Daily sodiem loss. • What happen with water is transferred into one body. • What is most frequently incurred in the body, (a) (b) • What is happening of sodium.

In contrast, other topics to keep in mind Include

• Lipids which are used as a solvent. - Solution which can be soluble as how well the solute will dissolve in the solvent. has to know those chemical reactions

Understand Functions in the Body

1. Understand that homeostatic control systems arc acquired through evalution. 2) Explain the can of bacterial rhythanus ,providing asamples, identify of 3) DEFINE of the pool of a substance are added to or removed from the pool . understand balance and subsistent at the bud body depends upon the relative rated of NET gain- and NET lows. :NEXT, identify make a substance can be increased.

Lipids

• Lipids mostly Cand H atoms and has to know how to covalent bonds
• Polar is not polar?
• water soulbiuity?
• The functions of Lipids has for classes:
• Fatty acids: collagen and at at one and.
• Collagen fiber has for
• Protein under the skin. Fat
•  And in
•  Under the water and for long water and for short molecules.

Lipids as Electrolytes

• Most important aspects here include. " What are the rules for electrolyte composition What are electrolytes and how do they work? What are the physiological importance of the terms as electrolyte composition
• The two types of electrical and central composition
• The main fluid for the electro composition .the next level as electrolyte and central canal.

Proteins

• Proteins are composed it can also be important signaling molecules and rose trees where pathways leading to many police adaptation within the body.
• Important is formation and extra matrix :collagen in protein fibers and for all saccharides
• Self selling. • What is the Scape filling?

Understand Functions in the Body

1. Detail the general roles played by proteins within physiology 2) Describe the structural compounds of amino acids bond together and form 0 polypeptides 3) Explain  how protein shape is  Determined by permanent secondary, tertiary and quaterray structure.

Nucleic Acids

• They’re are a collection of chemical messages through with they can can
• The functional role of electrolyte and chemical messages. important the different types.
• the two the major fluid in the body or plasma central the volume.

Summary : Terms to understand

• Fluid compartments in the body, Intracellular, ICF, extracellular, ECF. plasma, interstitium: -Cell in steady-state and not being in equilibrium.

Summary:

• Important terms include:

• Homeostatic reflex and Local homeostats

• Response. Herman in my transmitter

• Paracrine/autacoid

• Agents.

• Key terms to remember: Functional unit of an organ. Understand there is of the concept

Explore the concept of homeostasis, its regulation through negative feedback, and the critical role of physiological systems. Understand the importance of maintaining a stable internal environment, including blood glucose levels and pH balance. Investigate how impaired functions, such as thermoreceptors or RNA production, can disrupt homeostasis.