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Questions and Answers
Who is considered the father of modern Medicine?
Hippocrates
What did William Harvey correctly describe in 1628?
Emphasis on the internal environment of the body was a discovery of William Harvey.
False
_______ is the term used for the dynamic steady state of the internal environment in living systems.
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Match the following individuals with their contributions:
- Hippocrates
- William Harvey
- Claude Bernard
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Which term describes the regulatory mechanism that operates within a desired set point or rate of function?
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What term is used to describe the mechanism that reflects the strength of regulation?
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______ is the cost of adaptation to a stressful environment that leads to wear and tear of the body.
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Match the following adaptation types with their descriptions:
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What are the two main types of proteins found in the cell membrane?
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Which type of proteins account for about 30% of the membrane proteins?
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Which type of proteins account for about 70% of the membrane proteins?
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The lipid bilayer portion of the cell membrane is permeable to water-soluble substances.
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______ are examples of lipid-soluble substances that can cross cell membranes easily.
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What are the typical components of an average adult human body by weight?
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Which of the following hormones show changes at high altitudes?
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At high altitudes, GH levels remain the same in individuals with no change in body weight. Is this statement true?
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High altitudes lead to a decrease in ________ and ________.
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Match the neurological response to high altitude with its effect:
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What are the main sources of water in the body?
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What is the primary reason for the unidirectional conduction of action potentials?
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Which type of fibers have faster conduction speed of action potentials?
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Myelination of nerve axons decreases the speed of action potential conduction.
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Action potentials are propagated from node-to-node rather than conducting along the whole nerve membrane because voltage-gated __ channels are only expressed at nodes of Ranvier.
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Match the neurotransmitter with its effect:
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What is the primary function of Ca2+ ATPase?
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How many Na+ ions are pumped outward by the Na+-K+ Pump?
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Secondary active transport involves carrier proteins that consume energy directly from ATP.
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Endocytosis may include two types, pinocytosis, and __________.
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Match the following terms with their descriptions:
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What are the two major subtypes of beta receptors?
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What are the components of a reflex arc?
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Hormones are secreted into the blood stream to act on nearby tissues directly.
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Baroreceptors located in some major systemic arteries monitor __________.
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Match the hormone with its action: Hormone - Catecholamines, Action - Glycogenolysis
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How many cranial nerves are there?
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What are the two divisions of the autonomic nervous system?
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The ANS transmits impulses to smooth muscles and glands involuntarily.
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The __________ division is often called the fight-or-flight division.
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Match the neurotransmitters with their ANS divisions:
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Study Notes
Course Overview
- Medical Physiology course for PC1 students
- Module: Introduction to Medicine
- Module Code: INMD 2011
- Instructor: Dr. Kumlachew Mergiaw
Objectives
- Apply knowledge of ethical, legal, and professional values in medicine
- Describe the benefits of homeostasis for the survival of organisms
Course Contents
- Definition and approach to studying physiology
- Functional organization of the human body and control of internal environment
- Introduction to cell physiology
- Body fluid compartments and composition
- Plasma membrane and transport mechanisms
- Introduction to electro-physiology
Teaching-Learning Methodology
- Interactive lectures
- Integrated biomedical laboratory
- E-learning
- Self-directed learning
Required Reference Books
- List of 13 reference books, including:
- Antony, Cathesine Parker, Textbook of Anatomy and Physiology
- Fredric H. Martini, Fundamentals of Anatomy and Physiology
- Ganong, Review of Medical Physiology
General Introduction
- Physiology: the study of the functions of living organisms
- History of physiology:
- Aristotle (384-322 B.C.): coined the term "physiology"
- Empedocles (504-433 B.C.): hypothesized about the universe and human body
- Hippocrates (460-370 B.C.): father of modern medicine
- Claudius Galen (130-201): began modern experimental physiology
- William Harvey (1628): correctly described blood circulation
- Claude Bernard (1813-1878): discoverer of internal environment
- W.Cannon (1929): coined the term "homeostasis"
Physiological Processes
- Extend from physical and chemical processes in cells to whole organism
- Include:
- Chemical reactions in cells
- Transmission of nerve impulses
- Contraction of muscles
- Mechanisms of vision, movement, digestion, etc.
- Reproduction
- Transformation of energy
Fields of Physiology
- Human physiology
- Relationship between physiology and other sciences (anatomy, biochemistry, pathology, pharmacology, etc.)
Homeostasis
- Dynamic steady state of the internal environment
- Process that maintains the internal environment in a stable state
- Negative feedback regulation
- Importance of homeostasis in maintaining health and wellness
Levels of Physiological Regulation
- Sub-cellular autoregulation
- Cellular autoregulation
- Local (tissue) level regulation
- Distant (organ/system) regulatory mechanisms
Negative Feedback
- Response to a stimulus results in the opposite effect
- Examples:
- Temperature regulation
- PaCO2 regulation
- Blood pressure regulation
- Regulation of plasma volume
- Regulation of acute hemorrhage
- Regulation of hormonal secretion
- Regulation of blood glucose
Positive Feedback
- Response to a stimulus results in the same effect
- Examples:
- Nerve impulse
- LH secretory surge in mid-cycle
- Uterine contraction during labor
- Viral infection
- Severe shock
- Blood clotting
Feedforward
- Anticipatory response to a stimulus
- Examples:
- Exercise
- Picking up an object
Allostasis
- Adjustment of the body to resting and active states
- Introduced by Sterling and Eyer (1988)
- Addresses basic regulatory systems
- Examines behavior of bodily regulation under constraint
Allostatic Load
- The cost of adaptation to a stressful environment
- Repeated cycles of allostasis lead to wear and tear on the body
- Manifestations:
- Decreased cognitive function
- Abdominal obesity
- Increased risk of hypertension
- Cardiovascular disease
- Type one diabetes
- Decreased immune responses
Heterostasis
- Concept of adaptation
- External world → problems to be solved → structural evolutionary changes
- Bilateral adaptation: organism adapts to environment, and environment is modified
- Examples:
- Grazing animals vs. herbs
- Trees vs. soil
- Birds adapting to high altitudes### Cultural Adaptations
- The Eskimos: Live in the Arctic Zone
- Housing: Low roof and nearly round to prevent heat loss and ensure perfect ventilation
- Clothing: Skins and fur consisting of two layers to imprison heat
- Food: Walrus soup which is mainly fat
Long-term Adaptation to Heat
- Genetic
- Body shape: Long limbs and protruding organs
- Physiological
- All sweat glands become active in hot climate
- Some sweat glands are inactive in temperate climate
- Cultural
- E.g. Clothing of Arabian Bedouins (white, loose, and long garments) to evaporate heat
- Insulating protection
- Circulation of air
Adaptation to High Altitude
- Homeostatic: e.g. CVS, Resp. System
- Adaptive:
- Hyperhaemoglobinaemia
- Hypervascularization
- Hyperactivity of cell enzymes ↑O2 utilization
Respiratory Responses to High Altitude
- MV and VC, FVC:
- Native highlanders: RR of sea level man +25-35%
- New comer to high altitude: RR of highlanders +20%
- After acclimatization, there will be only small differences in ventilation between highlanders and lowlanders
- MV at different altitudes:
- 4.8 L/min at sea level
- 6.6 L/min at 4330m
Regulation of Ventilation at High Altitude
- This is environmental rather than genetic
- Initial increase in ventilation at high altitude is triggered mainly by stimulation of peripheral chemoreceptors by hypoxemia
- Hypoxia depresses cortical neurons and individuals ascending to >3000m feel sleepy
- With higher altitude, judgement may be impaired, and convulsion may occur
Highlanders and Lowlanders
- Highlanders: ↑DPG and ↑PaO2, ↓A-a difference
- Lowlanders: ↓DPG and ↓PaO2, ↑A-a difference
- High altitude → shift of oxyhaemoglobin dissociation curve to the right
- Pulmonary Hypertension (hypoxia-induced pulmonary vasoconstriction)
Haematologic Responses to High Altitude
- Hb increases linearly up to 3660 m and stops at 6000 m asl
- Several weeks following ascent, RBCs and Hb increase significantly due to the rise in the level of Epo and the stimulant action of hypoxia on bone marrow
Haematologic and CVS Responses to High Altitude
- ↓SV, ↓CO keeping on falling for about 10 days
- ↑HR compensates for the above fall
- ↑Total blood volume
- ↓Plasma volume → 15-20%
- Initial rise in BP followed by vasodilatation secondary to chronic hypoxia → ↓Systemic BP
- But in Ethiopians exposed to high altitude, the trend is an increasing pattern, i.e. cardiovascular adaptation varies in different regions of the world
Coronary Circulation
- Increase in coronary vascular resistance → ↓Coronary BF
- Intense vascularization of myocardium
- ECG sinus tachycardia with ventricular ectopic beat
- Right axis deviation
Endocrine Responses to High Altitude
- Changes in hormone release play a part in acclimatization to high altitude
- High-altitude anorexia leads to a hormonal response pattern modulated by both hypoxia and caloric restriction (CR)
- Generally, high altitude leads to:
- Elevated levels of glucocorticoids, thyroid hormones, catecholamines, and rennin
- Growth hormone in persons with body wt loss
- Insulin sensitivity and rate of glucose utilization
- Diuretic effect of the hypobaric atmosphere causing change in secretion of aldosterone, antidiuretic ADH, and ANP
- Decrease in progesterone and estrogen
- ↓Testosterone secretion in urine (early); more at 3rd day
Reproductive Responses to High Altitude
- Men:
- Normal spermatogenesis
- Oligospermia, azoospermia
- Women:
- Menstrual abnormalities
- ↑Duration of menstrual flow
- Dysmenorrhea
- Irregular periods
Neural Responses to High Altitude
- Acute hypoxia of high altitude (6100m) impaired sensory, perceptual, and motor performance
- Effect of highest altitude → a condition similar to acute organic brain syndrome
- SaO2 of 85% ↓capacity for mental concentration and abolishes fine muscular coordination
Composition of Human Body
- The approximate composition of an average adult human body weight is:
- Water: 60%
- Proteins: 18%
- Fats: 15%
- Minerals: 7%
Body Fluid Compartments
- Extra-cellular Fluid (ECF):
- Contains about 20% of body weight (14 L)
- Fluid in vascular system: 25% of ECF
- Fluid in interstitium: 75% of ECF
- Total blood volume: 8% of body weight
- Intra-cellular Fluid (ICF):
- Contains 40% of body weight (26-28 L)
Importance of Water in the Body
- As a solvent: to electrolytes and dissolve nutrients
- Digestion and absorption require fluid medium
- Transportation of materials
- Temperature regulation
Measurement of Body Fluids
- Direct and indirect methods
- The commonly used method is: Indicator (dye) dilution method
- Known quantity of dye is injected into a compartment
- Time is allowed for mixing
- Concentration of sample is determined
- Characteristics of the dye:
- Non-toxic
- Inert (inactive)
- Confined to a compartment
- Not metabolized
- For TBW: Use D2O to measure it
- For ECF volume: Use inulin, mannitol, raffinose, radioactive Br-, Cl-
- For Plasma volume: Use Evans blue or radioactive iodide serum albumin (RISA) or 125I-labelled albumin
- Interstitial fluid (IF) = ECF - Plasma vol
- IF cannot be measured directly because it cannot be sampled
- Intra-cellular fluid (ICF) volume: TBW-ECF
- It cannot be measured directly
- Total blood volume = Volume of RBC X 100 = 2.5L x 100 = 5.5L
- OR
- Total blood volume = Plasma volume x 100 = 3.05 L x 100 = 5.5L
Osmolality and Osmolarity
- Osmolality:
- Is the concentration of osmotically active particles per kg of water
- To prepare a standard one osmolal solution, one osmole of a solute and one kg of the solvent are added together
- Osmolarity:
- Is the concentration of osmotically active particles per liter of solution
- To prepare a standard one osmolar solution, one osmole of a solute is added to one liter of solvent### Cell Membrane Structure
- The cell membrane consists of an organized arrangement of proteins, lipids, and carbohydrates (CHOs)
- The major lipids are phospholipids (e.g. phosphatidyl choline and phosphatidyl ethanolamine) and cholesterol
- Lipids form the basic structure of the membrane, arranged in a lipid bilayer
- Globular proteins are embedded in the lipid bilayers and participate in the transport of lipid-insoluble particles
Cell Coat (Glycocalyx)
- The cell coat is made up of glycolipids and glycoproteins
- It is the site of hormonal receptors and antigenic activity in ABO blood groups
Phospholipid Organization
- Phospholipids are organized into a double layer with their hydrophobic (tail) directed toward the center of the membrane and polar heads directed outward, facing the ECF and ICF
Lipid Bilayer Permeability
- The lipid bilayer portion of the cell membrane is impermeable to water and water-soluble substances (e.g. ions, glucose, urea)
- Fat-soluble substances (e.g. O2, CO2, alcohol, and drugs) can penetrate this portion of the membrane
Transport Function of the Cell Membrane
- Includes forces causing movement of water and solutes across the cell membrane
- Types of transport mechanisms:
- Passive (leak): simple and facilitated diffusion
- Active (pump): biochemical and biological processes using metabolic energy
Factors Affecting Transport
- Lipid solubility: lipid-soluble molecules cross cell membranes more easily
- Electrical charge and electrical gradient: charged molecules move faster in the direction of the opposite charge
- Non-ionic diffusion: unionized molecules diffuse rapidly in the direction of low concentration
Types of Transport
- Simple diffusion: free movement of a substance from one part of a solution to another
- Osmosis: movement of water from higher to lower concentration through a semi-permeable membrane
- Facilitated diffusion: carrier-mediated transport down an electrochemical gradient
- Active transport: pump mechanisms that use metabolic energy
- Vesicular transport: transport of substances through vesicles
Facilitated Diffusion
- Carrier-mediated transport down an electrochemical gradient
- Characteristics:
- Occurs down an electrochemical gradient
- Does not require metabolic energy
- Is more rapid than simple diffusion
- Is carrier-mediated and therefore exhibits stereo-specificity, saturation, and competition
- Examples: transport of glucose, proteins (macromolecules)
Active Transport
- Pump mechanisms that use metabolic energy
- Types:
- Primary active transport: ATPase pumps (e.g. Na+-K+ pump, Ca2+ pump)
- Secondary active transport: electrogenic cotransport (e.g. Na+-glucose co-transport)
Carrier Hypothesis
- Carrier-mediated transport: uniport and symport
- Carrier-mediated exchange: solute carrier cannot return from trans to cis side unloaded
Ion Channels
- Occur across integral membrane proteins called channels
- Types:
- Open
- Gated (e.g. voltage-gated, ligand-gated)
Vesicular Transport
- Types:
- Endocytosis: engulfing of materials by invagination of the outer part of a cell membrane
- Exocytosis: release of materials from the cell through the fusion of vesicles with the cell membrane
Membrane Potentials
- Resting membrane potential (RMP): the stable voltage difference across the cell membrane
- Ionic basis of membrane potentials: the equilibrium potential is a function of the size of the ion concentration gradient
- Measured membrane potential (Vm): the weighted average of ion equilibrium potentials for permeable ions
Action Potential
- The electrical signal that occurs in excitable tissues (e.g. neurons and muscle) in response to a stimulus
- Phases:
- Depolarization: rapid increase in membrane potential
- Overshoot: peak voltage that exceeds 0 mV
- Repolarization: return of membrane potential towards Vm
- After-hyperpolarization: transient decrease in membrane potential below Vm
- Characteristics:
- All-or-none impulse
- Propagated over long distances without decay
- Depolarization beyond a threshold voltage
Refractory Periods
- Absolute refractory period: the time during which an excitable cell cannot respond to a new stimulus
- Relative refractory period: the time after the absolute refractory period during which the cell is less excitable
- Caused by closure of inactivation gates of Na+ channels and increased K+ conductance
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This quiz is designed for first-year medical students at Debre Berhan University, covering the introductory module of medical physiology, including ethics and legal methods in the medical profession.
