Human Physiology

Daily water needs

Factors affecting daily water needs

• Climate

• Clothing

• Activity levels

Body water balance

• Fluid balance exists when total h2o intake and total h2o loss are equal

• Body controls homeostatic mechanisms to maintain h2o balance

• This maintains normal hydration

movement of body water between compartments

• Water moves between these compartments via osmosis

• Osmosis is the net movement of solvent molecules through a partially permeable membrane from a region of low solute concentration to a region of high solute concentration

• Passive transport to equalize the solute concentrations on the 2 sides

Measuring Body Water Status

• Quantified by measuring solute concentration

• OsmolaLity: number of osmoles (Osmol) of solute per kg of solution 

• OsmolaRity: number of osmoles (Osmol) of solute in a litre of solution

• Measures the body’s electrolyte-water balance 

• Determined on a plasma, saliva or urine sample 

• Cryoscopic osmometer: freezes saliva sample

Effects of exercise - Performance consequences (hydration)

• Physical work performance is usually decreased when dehydration exceeds about 1-3% of body weight. 

• Decline in running velocity during a 10 km trial with dehydration of 2% of body weight.

Dehydration

• Physical work performance is usually decreased when dehydration exceeds about 1-3% of body weight. 

• Decline in running velocity during a 10 km trial with dehydration of 2% of body weight.

Function of the respiratory system

The primary function of the respiratory system is to supply oxygen to the tissues of the body and to remove carbon dioxide and to regulate acid base balance

Pulmonary respiration

• Process of ventilation

• Exchange of o2 and co2 in the lungs

Cellular respiration

O2 utilisation and CO2 production

Main Purposes of the Respiratory System

• Gas exchange

• Acid-base balance regulation

• Homeostatic regulation of body pH

• Vocalisation

• Protection from inhaled pathogens and irritating substances

ventilation

mechanical process of moving air in and out of the lungs

diffusion

 movement of molecules from area of high pressure to low pressure

Major Functions of the Respiratory System

➢Pulmonary ventilation – moving air into and out of the lungs 

➢External respiration – gas exchange between the lungs and the blood

➢Transport – transport of oxygen and carbon dioxide between the lungs and tissues 

➢Internal respiration – gas exchange between systemic blood vessels and tissues

Lung anatomy

respiratory system anatomy

Pulmonary Ventilation/Breathing 

▪ Inhalation and Exhalation 

▪ Exchange of air between atmosphere and alveoli

External (Pulmonary) Respiration 

▪ Process of gas exchange between alveoli and blood

Internal (Cellular) Respiration 

▪ Systemic capillaries transport to tissue cells (muscles) 

▪ Supplies cellular respiration

Boyle’s law

➢ “Pressure of a gas in a closed container is inversely proportional to the volume of the container at a constant temperature

➢Pressure in lungs must be lower than atmospheric pressure

Exhalation - rest

▸ Pressure lungs greater than atmospheric pressure

 ▸ Passive process 

▸ Elastic recoil 

▸ Relaxation of diaphragm and external intercostals

Volume of air remaining in the lungs after maximal exhalation 

▸ Less energy to exhale than inhale. 

▸ Intrapulmonic pressure >761 mmHg

intrapulmonary and intrapleural pressure relationships

measuring ventilation

▸Air moved in and out of lungs 

▸ Minute ventilation (VE) - amount per minute 

▸ Tidal volume (VT)- amount per breath 

▸ Breathing frequency (f) - number of breaths 

▸ VE = VT x f 

▸ Alveolar ventilation (VA) - 70% of VT reaches respiratory zone 

▸ Dead space ventilation - 30% VT conducting zone

measuring airway resistance

ventilatory parameters

purpose of the CV system

• Controls blood transport around the body  

  • Transport O2 and nutrients to tissues  

  • Removal of CO2 from tissues  

  • Transport of hormones  

• Regulation of body temperature  

• Support of immune function

components of the CV system

• Heart

• Arteries and arterioles 

• Veins and venules 

• Capillaries

heart anatomy

• 4 chamber (2 atria 2 ventricles)

  • Septum

• 4 valves

  • 2 atrioventricular (AV)

    • Mitral valve (bicuspid)

    • Tricuspid valve

  • 2 semilunar valves (SV)

    • Aortic valve  

    • Pulmonary valve

Diastole  

• Relaxation phase  - pressure is low 

  • Filling with blood from atria 

  • 75% of blood enters during relaxation

systole

• Contraction phase: pressure in ventricles rise

• Blood ejected in pulmonary and systemic circulation

• Ejection of blood

heart sounds

• “Lub” - closing of AV valves 

• “Dub” - closing of SL valves

Electrical Components of the Heart - Sinoatrial node

• Anterior internodal tract

• Middle internodal tract

• Posterior internodal tract

• Bachmann's bundle

electrical components of the heart - atrioventricular node

• Buncle brunch

• Conduction pathways

Electrical activity of heart

• 3 main recognisable waves  

  • P Wave 

    • Atrial Depolarisation  

• QRS Complex 

  • Ventricular Depolarisation  

  • Hides Atrial Repolarization 

• T Wave 

  • Ventricular Repolarization  

• Abnormalities may indicate disease, events etc

depolarisation repolarisation cycle

Electrical activity of heart

• Electrocardiogram  

  • Composite record of electrical events

• 12 lead ECG  

  • 10 leads  

    • Vectors (V1-V6)  

    • Left Arm (LA), Left Leg (LL)

    • Right Arm (RA), Right Leg (RL)

HR functional parameters

• ~70 BPM (Untrained females and males)  - resting

• ~50 BPM (Trained females and males) - resting

• BRADYCARDIA  Resting ≤ 60 BPM 

• TACHYCARDIA  Resting ≥ 100 BPM

Stroke Volume (SV)

• Amount of blood pumped per heart beat (ml)

• Difference between EDV and ESV (End Diastolic volume/End Systolic Volume)

• Resting values for untrained:

  • Females 50 ml

  • Males 70 ml

• Resting values for trained:

  • Females 80 ml 

  • Males 110 ml

Ejection Fraction (EF)

• Proportion of blood pumped out the left ventricle with each beat (%)

• EF (%) = (SV/EDV)*100

• Resting Values: Average 60 % (~2/3) at rest

Cardiac output (Q)

• Total volume of blood flow from the heart per minute (L/min)

• Interaction between heart rate and stroke volume  

• If we can increase the volume per beat we can beat less

• Resting Q values for trained and untrained females and males:

  • Untrained females: HR 70 BPM x SV 50 ml = 3.5 L/min  

  • Trained females: HR 50 BPM x SV 80ml = 4.0 L/min  

  • Untrained males: HR 70 BPM x SV 70ml= 4.9 L/min  

  • Trained males: HR 50 BPM x SV 110ml = 5.5 L/min

• Q (L/min) = HR x SV

Blood Pressure

• The force exerted by blood against arterial walls during cardiac cycle (mmHg)

• Systolic Blood Pressure  

  • Force exerted during ventricular systole  

  • Highest pressure within the vascular system

• Diastolic Blood Pressure  

  • Force exerted during ventricular diastole  

  • Lowest pressure within the vascular system

• Normal Values  

  • SBP = 120 mmHg  

  • DBP = 80 mmHg

• Expressed as a ratio: SBP/DBP

rate-pressure homeostasis

• An estimation of myocardial workload and resulting O2 consumption

• Index of relative cardiac work relates closely to directly measured myocardial oxygen consumption and contrary blood flow

• RPP = SBP x HR

blood pressure homeostasis

define thermoregulation

thermoregulation is the ability of an organism to keep its body temperature within certain boundaries

Thermoregulation types

• Homeotherms: constant internal body temperature regardless of external stimuli

• Endotherms 

  • Generate heat internally  

  • Maintain high basal heat production 

• Ectotherms  

• Depend on external heat sources  

• Temperature changes with the environment

how hot are we?

• Internal (core) body temperature  36.5-37.5oC  

• Optimal function  36.5-40.0oC

Hypothermia

• Low body temperature  <35.0oC (internal core temperature)  

• Lowest survivable = ~14.4oC

hyperthermia

• High body temperature  >38.0oC (internal core temperature)  

• Damage to cells > 42.0oC  

• Highest survivable = ~46.5oC

Symptoms of hypothermia

symptoms of hyperthermia

factors influencing core body temperature

The “balancing act“

Body temperature is a simple balancing act between: 

• Heat gain  

• Heat loss

specific heat capacity

The amount of energy required to raise the temperature of a given substance by 1 C

• Different substances have different heat capacity  

  • Water = 4.186 (kJ.kg-1 . oC-1 )  

  • Human body tissue = 3.48 (kJ.kg-1 . oC-1)

The law of conservation of energy

Energy can neither be created nor destroyed, it can only be transferred from one state to another

Heat production

• Liberate chemical energy in food we eat  

• Use it to resynthesize ATP  

• But the process is inefficient as the energy release is not equal to ATP resynthesis  

• Releasing energy in the form of heat

voluntary vs involuntary heat production

• Voluntary  

  • Exercise  

    • 70-80% EE appears as heat

•  Involuntary  

  • Shivering  

  • Action of hormones  

    • Thyroxine  

    • Catecholamines

Heat production during dynamic exercise

• To contract the muscles  

  • Chemical energy as ATP  

  • Exothermic reaction convert to mechanical energy  

  • 25-30% converted to mechanical work (rest is heat)

oxygen consumption

• VO2 as an indicator of energy expenditure (heat production)  

  • 1 litre of O2 consumed produces ~20kJ of heat  

  • Resting VO2  

  • ~0.25 L/min  

  • 0.25 x 20  

  • 5kJ/min of heat

Measuring core body temperature

• Thermometer probe at an accessible site:

• Hypothalamus        

• Intestinal           

• Ear drum

• Oesophagus          

• Oral

• Rectum              

• under tongue

Measuring skin temperature

• Skin temperature depends on:  

  • Ambient temperature  

  • Distance from core  

  • Skin blood flow

external heat gain

• Sky thermal radiation  

• Solar radiation  

  • Reflected  

  • Air temperature and humidity  

• Ground thermal radiation

thermal gradient

heat transfer is always from higher to lower temperatures

Heat loss

• Evaporation - VAPORISATION OF SWEAT FROM WATER TO VAPOUR

• Radiation 

• Conduction 

• Convection

evaporation

• Evaporation of sweat from water to vapour

• ~25% heat loss at rest and ~85% during exercise

• Sweat evaporation - Water to Vapour 

•  1g sweat = 2.41kJ of heat

sweating

• Sweat is released from sweat glands  

• Stimulated by Sympathetic Nervous System (SNS)  

• Increased SNS activity when exercising, anticipation or nervous

Factors influencing evaporation

• Air Temperature (humidity)  (↓)

• Convection currents (wind)  (↑)

• Skin exposure (surface) (↑)

Quantifying Sweat Loss & Rate

sweat rate

• Depends on:

  • Body Size  

  • Absolute VO2  (ra)

  • Aerobic Fitness  

  • Heat Acclimatisation  

  • Environment

radiation

transfer of heat in the form of electromagnetic waves

conduction

• heat transfer from the body to an object with direct contact

• 3% heat loss at rest at room temperature

convection

• heat transfer from one place to another by the movement of fluids (air or water)

• ~12% heat loss at rest at room temperature

convection - skin blood flow

• conduction of heat to or from air or water

• dependent on skin blood flow

• during exercise heat dissipation by convection is reduced

vasoconstriction and vasodilation