BPK 142 2nd part after first midterm

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Anthropometry

• quantitative measurement of body size and proportions

Transport of oxygen

98 percent of oxygen is carried by hemoglobin

He+O2→ HbO2

Other 2 percent in plasma

One gram of hemoglobin saturated with O2 when combined with 1.34 ml of O2

Hemoglobin concentration equals 15.0 grams per 100ml of blood

O2 carrying capacity 15.0g x 1.34ml/g=20.1 ml of O2 per 100ml of blood

Percent saturation of O2 related the amount of O2 combined with hemoglobin to max O2 capacity of hemoglobin

Arterial blood at sea level

Hemoglobin is 97.5 percent saturated with O2

Venous blood at rest at sea level:

75 percent saturated with O2

Arteriovenous oxygen difference

Reps how much oxygen is extracted or consumed by the tissue for each 100ml of blood perfuming them

Oxyhemoglobin dissociation curve

• hemoglobin act as tissue oxygen buffer system

• Level or alveolar oxygen varies from 60 to more than 500 mm Hg but saturation is maintained

• Due to flat shape of the curve

• PO2 in tissue doesn’t vary more than a few mm Hg but saturation varies widely due to steep portion of curve

Bohr effect

• increased body temperature

• Increases PCO2

• Decreased PH

• Shift oxyhemoglobin curve right which releases more oxygen at tissue level for given PO2

PO2 levels at lungs and tissues

Total O2= dissolved O2 + HbO2

• in tissues, PO2 is low

  • drives O2 exchange out of plasma

  • Low plasma PO2 drives O2 release form Hb

• in lungs, PO2 is high

  • drives O2 exchange into plasma

  • Hugh plasma PO2 drives O2 binding to Hb

Stroke volume

Amount of blood pumped by either left or right ventricle per beat

Cardiac output

Amount of blood pumped by either the left or right ventricle of the heart per MINUTE

• both left and right ventricles must have SAME cardiac output so that blood flow through pulmonary and systemic circuits is maintained equally

• Cardiac output= heart rate x stroke volume

• When cardiac output increase, more O2 transported to working muscles

Fick equation

• When cardiac output increase, more O2 transported to working muscles

• Expressed in VO2=HR x SV x (a-vO2) diff

• VO2= oxygen uptake or utilization by tissues in body

• (a-vO2) diff= arterial mixed venous oxygen difference- amount of O2 extracted at tissue capillary beds

• To increase O2 uptake, increase cardiac output and or extract more O2 from arterial blood

• Cardiac output rises with work rate

• CARDIAC OUTPUT required for a given workload is reasonably similar for trained and untrained subjects

• Heart rates increases linearly with work rate and O2 consumption

• Max HR= 220 - Age (standard deviation is plus or minus 12 bpm)

• For any given workload

  • trained subjects have a lower exercise heart rate

  • Trained subjects have higher stroke volume than untrained (cardiac output HR x SV)

Stroke volume

• stroke volume= end diastolic volume minus end systolic volume

• Diastole= resting phase of cardiac cycle between heart rates

• Systole= contraction phase of cardiac cycle when ventricles pump out their stroke volume

• End systolic volume; volume of blood remainsing in ventricle after ventricles have finished contracting

  • 50 ml in an untrained person at rest

• End diastolic volume: volume of blood in each ventricle at end of diastole ( after heart fills up)

  • 120 ml in an untrained person at rest

Ejection fraction

• percent of end diastole volume ejected with each contraction

• Ejection fraction= stroke volume/ end diastolic volume

• Ejection fraction increases with exercise

Mechanism of increase in stroke volume during exercise

• greater systolic emptying= greater ejection fraction

• Heart has functional residual volume

  • rest in upright, 50-60 percent of blood in ventricle is pumped out of ventricle during contraction- 50-80ml of blood remains in ventricle

  • During graded exercise, heart progressively increases stroke volume by means of a more complete emptying during systole due to sympathetic hormones

Distribution of blood flow during exercise (also talk about increase blood flow)

• At rest 15-20 percent of systemic blood flow goes to skeletal muscles

• During maximal exercise 85 percent of cardiac output can be diverted to working skeletal muscles

• Increases blood flow is caused by

  1. Increased blood pressure

  2. Constriction of arterioles in gut area( liver, intestines, stomach, kidneys) and non working muscles due to sympathetic nervous system stimulation

  3. Dilation of arterioles in working muscles due to relaxation of smooth muscle in walks of arterioles

     • release local factors as result of muscle contraction

Poiseuille’s law

• resistance to flow= (fluid viscosity x tube length )/ radius of tube

• Decreasing tube radius by factor of 2 increases resistance flow by factor of 16, decreasing flow by factor of 16

• 33 percent decrease in radius of arterioles will produce 40p percent increase in resistance to flow

• Small change in blood vessel radius will DRAMATICALLY ALTER BLOOD FLOW

Physiological determinants of VO2 max (WHAT DOES IT SAY ABOUT UR BODY)

• VO2 max provides an integrated measurement of capacity of your physiological systems that contribute to O2 transport and utilization

• Including cardiovascular

• Respiratory

• Neural

• And muscular systems

• While maintaining body homeostasis

Important factors that determine VO2 max

• as duration of event requiring continuous energy expenditure becomes longer, aerobic metabolism will contribute higher percentage of ATP regeneration

1. Ability to ventilate lungs and oxygen the blood passing through lungs

2. Ability of heart to pump blood- cardiac output

3. Oxygen carrying capacity of blood

4. Ability of working muscles to accept large blood supply

5. Ability of muscle fibres that extract oxygen from capillary blood and she it produce energy- oxidative enzyme levels

VO2 max test protocols

1. Test protocol should exceed 6 minutes but be less than 15 minutes

2. Incorporate a warm up period- first stage of test

3. The test protocol should be arranged in stages, with each stage progressively increasing intensity until termination criteria is reached

Criteria of attainment of VO2 max

1. Oxygen consumption ceases to increase linearly with increasing work rate and approach plateau as at some point body switches from aerobic to anaerobic, last 2 values differ with plus 2 ml/kg/min

2. Heart rate should be close to age predicted max (220 - age). Test is protocol dependent

3. Blood lactate levels should be 8millimoles/litre or greater 3-5 minutes post exercise

   indicates significant contribution from anaerobic metabolism

4. Respiratory exchange ratio (VCO2 divided by VO2) should be greater than 1.15

   • indicates anaerobic metabolism

   • Metabolic acidosis

5. Subjective observations- is subject exhausted at end

Mode of exercise

• most subjects, highest VO2 max values obtained during uphill treadmill running-5-7 percent higher due to activation of larger muscle mass on treadmill

• But competitive athletes able to achieve VO2 max values equal to or higher than their treadmill scores doing their sport

• Due to muscle capillarization and aerobic enzyme levels are important determinants of VO2 max

• Athletes should ideally be tested in mode of exercise used in their sport

Types of bicycle ergometers

Bicycle ergometers are of 2 types

1. Mechanical- monarch ergometers

2. Electrically braked bicycle ergometers- resistance is provided by moving a conductor through a magnetic field

Pros to ergometers to treadmill for exercise testing

1. Cheaper

2. Portable

3. Doesn’t require electricity

4. Patient more stable and body weight supported- easier to collect physiological data during exercise- heart rate, blood pressure, oxygen uptake, blood samples

5. Easier to quantify work rate

Cons to bicycle ergometers

1. Can’t obtain as Hugh VO2 max as on treadmill

2. Cycling not common mode of movement for individuals. Walking more common

Heredity

• identical and fraternal twins, current evidence indicates that VO2 is 40-50% genetically determined

• Improvements in aerobic capacity with training normally range between 6 and 20%

Age and sex

• VO2 max (litres/min) increases with age

• Peaks between 18 and 25 years old

• VO2 max declines 1% per year

• By 55, VO2 max on average 25-30% lower than 20 year olds

• Before puberty, no significant difference in VO2 max between boys and girls

• After puberty, average male has VO2 max that is 20-25 percent higher than average female

• There are many females who have VO2 max scores higher than less fit males

  reasons for sex difference

• Differences in body composition- male has more muscle and less fat- muscle is metabolically a more active tissue

• Average male has 10-14% higher hemoglobin concentration

Reasons for decrease in VO2 with age

1. Decrease in max heart rate, stroke volume and cardiac output in addition to negative changes in other components of oxygen uptake and transport systems

2. As person grow older, less physically active

   active individual maintain higher VO2 max as they age compared to sedentary individuals

   endurances trained 60 year olds can have higher VO2 max then sedentary 20 yr old

Why predictive tests for VO2

1. Cheaper and less specialized equipment required

2. Test can be submaximal-safety

3. Some test can be administered to large groups

4. Less motivation is required

Predictions based on heart rate during exercise

• VO2 max predicted from submaximal HR within 10-20% of persona’s actual value for normal subjects

• Type of subject for whom these tests are poor predictors are those in very high or low VO2 max categories

• Error is 4-5%

• procedures which use sub max exercise heart rate to predict VO2 max are based one:

  1. linear relation heart rate and oxygen uptake

     • true over wide range of exercise intensities but in some at heavy work rate VO2 increases relatively more than heart rate

  2. Similar max heart rate for all subjects- standard deviation is approx plus or minus 10 beats/min about the average max heart rate for ppl of same age group

     • max HR declines with age- must use age correction factor. Estimate HR with 220-Age

  3. in cases where VO2 is predicted from work rate. A fixed mechanical efficiency is assumed

     • Mechanical efficiency may vary 6% on bike ergometer

  4. Day to day variation in HR- even under highly standardized conditions (temperature, time of day, diet etc.) the variation in sub maximal HR is approx plus or 5 beats/min with day to day testing at same work rate

Efficiency of muscular work

• efficiency of muscular work is percentage of chemical energy converted to mechanical energy, with remainder lost as heat

• Computation of mechanical efficiency

  %EFF= (work performed (kcal)/energy expended (kcal)) x 100

• Efficiency of large muscle activities such as walking, running and cycling is usually 20-25 percent.

Parts of respiratory system

Nose, pharynx, larynx, trachea, bronchi(includes primary, secondary and tertiary), lungs, terminal and respiratory bronchioles, alveolar ducts, and alveoli

anatomy of the respiratory system

• with branching, supportive cartilage is gradually replaced by smooth muscle

• Contraction and relaxation of this smooth muscle constricts or dilates the bronchioles which majorly affects airway resistance

• Conducting airways lead inspired air to alveoli

• Volume of conducting airways= anatomic dead space around 150mL

Alveoli

• thin small walled sacs that have capillary beds in their walls

• Sites of gas molecule (O2 and CO2) exchange between air and blood

• Millions of alveoli

Respiratory membrane

• Very large surface area

  • 70 square meters in the normal adult-size of one side of a tennis court

• separates the air molecules in the alveoli from the blood in the capillaries

  • average thickness is 0.6 micrometers

  • Very thin- optimized for diffusion

Pulmonary ventilation

• movement of air into and out of the lungs

Mechanics of breathing

• pulmonary ventilation: movement of air into and out of lungs

• Molecules move from high pressure to areas of low pressure

• Boyle’s law: pressure of gas is inversely proportional to its volume ie: as one increase other decreases, pressure increase, volume decrease

  • P1V1=P2V2

• Movement of air in and out of lungs results from pressure difference between pulmonary air and atmospheric air

• Compliance: the amount of volume change in the lung for a given change in alveolar pressure

• During exercise, mouth breathing tends to replace nasal breathing-less resistance to airflow

• Air that enters either through nose or mouth is quickly saturated with vapour and warmed to body temperature, 37 degrees centigrade, even under conditions where very cold air is inspired

Tidal volume

• volume of gas inspired or expired with each breath at rest or during any stated activity

• 500 mL per inspiration or expiration at rest

• Look at slides week 8 slide 21

Stages of breathing

At rest: diaphragm is relaxed

Inspiration: thoracic volume increases

Expiration: diaphragm relaxes, thoracic volume decreases

Inspiration

• diaphragm descends and external intercostal muscles contract which increases volume of thoracic cavity which decreases pressure in thoracic cavity

• Pressure moves relative to gradient which is high to low pressure

• Decreases pressure in thoracic cavity which is 1-2 mm Hg decrease in intraalveolar pressure at rest vs atmospheric pressure

  • pressure drop during hard exercise can produce -30 mm Hg below atmospheric pressure

Expiration(passive)

• passive process at rest

• Diaphragm and external intercostal muscles relax which decreases volume of thoracic cavity

• Pressure in thoracic cavity increases above atmospheric pressure

• Air molecules move out of the lung following pressure gradient

Expiration( active)

• secondary muscles such as abdominal muscles and internal intercostals become involved in exercise

• Forced expiration can produce intra-alveolar pressure as great as +50mm Hg above atmospheric pressure

Breathing frequency

-12-16 breaths per minute

Minute ventilation

• Gas volume inspired or expired (not both) per minutes

• tidal volume x breathing frequency

• Max exercise

  • (Vt x Fr)

  • (3 L x 60breaths/min)

  • 180 litres/min

• Rest

  • (Vt x Fr)

  • Ex: .5L x 12-16 breaths/min

  • 6-8 litres/min

Expiratory reserve volume

• maximal volume that can be exhaled from resting end expiratory position

• Approx 25% of vital capacity at rest

Inspiratory capacity

• maximal volume of gas that can be inspired from resting end expiratory position

• Approx 75% of vital capacity at rest

Vital capacity

• greatest volume of gas that can be expelled by voluntary effort after maximal inspiration

• Vital capacity is the sum of inspiratory capacity and the expiratory reserve volume

Residual volume

• volume of gas remaining in the lungs after forced expiration

Functional residual capacity

• volume of gas remaining in the lungs at the end of a quiet exhalation

• Composed of expiratory reserve volume plus residual volume

Total lung capacity

• total lung capacity= vital capacity plus residual volume

Forced vital capacity

• subject is instructed to expire as hard and fast as possible for 4 seconds

Forced expiratory volume in one second (fev1.0)

• volume of air expired during the first one second of forced vital capacity manoeuvre

Alveolar ventilation (Va)

• volume of air that reaches alveoli per minute

• Only air that participates in gas exchange with the blood

• Anatomical dead space(Vd) is subtracted from tidal volume (Vt ) to obtain Va

• Rest

  Va= Fr x Vt-Vd

• = 12x(500-150ml)

• =4200 ml/min

• Max exercise

  Va= Fr x Vt-Vd

• =60 x (3000 ml - 150 ml)

• = 170000 ml/min = 170L/min

Lung volume (decrease)

• most volumes and capacities decrease when a person lies down and increase when standing

• Reasons:

  1. Abdominal contents push up against diaphragm

  2. There is an increase in intrapulmonary blood volume in horizontal position which decreases the space available for pulmonary air

Ventilation during incremental exercise

• during exercise, minute ventilation increases linearly with increasing exercise intensity (oxygen consumption) until approx 50%-60% of VO2 max in untrained subjects

• 75%-80% of VO2 max in endurance athletes

• Ventilatory threshold- point at which minute ventilation increases disproportionately with oxygen consumption during graded exercise

Ventilators threshold

• point at which minute ventilation increases disproportionately with oxygen consumption during graded exercise

Respiratory disorders

1. Obstructive disorders- blockage or narrowing of airways caused by increased airway resistance

   • more difficult to move air in and out

   • Blockage due to inflammation and Edelman, smooth muscle contraction or bronchioles secretion

   • Asthma, bronchitis, emphysema

2. Restrictive disorders: damage to lung tissue

   • loss of elasticity and compliance limiting expansion of lung

   • Pulmonary fibrosis, pneumonia

Obstructive disorders

• difficulty moving air rapidly in and out of lungs

• FEV1.0

• FEV1.0/VC much less than 80%

• Decreased MBC (maximal breathing capacity)

Restrictive disorders

• all lung volumes are reduced- VC, RV, FRC, TLC

• Lung tissue is stiff and can’t be expanded very far

• FEV1.p and MBC are reduced

• But FEV1.0/VC ratio is frequently 90% or greater

function of circulatory system

Composed of heart, blood vessels and blood

• transports essential materials throughout the body to cells

  • oxygen

  • White blood cells

  • Nutrients

  • Signaling molecules

• Collects waste materials from body’s metabolic activity

Sections of circulatory system

1. Pulmonary circuit

   • blood vessels going to and from lungs

2. Systemic circuit

   • blood vessels going to and from the rest of the tissues of the body

Heart

• a 4 chamber muscular pump which propels blood through the blood vessels

• Atria- 2 upper chambers of heart

• Ventricles- 2 lower chambers

• Septum: divides left and right sides of the heart

• Right ventricle pumps blood through pulmonary circuit

• Left ventricle pumps blood through systemic circuit

• Wall of LEFT VENTRICLE THICKER THAN WALL OF RIGHT VENTRICLE

• Direction of blood flow through the heart is controlled by unidirectional valves

• Heart murmur: valve is damaged or doesn’t close properly causes blood regurgitate which causes noise

• Heart muscle (myocardium) is specialized type of muscle = cardiac muscle

• Unlike skeletal muscle, all fibres or cells in cardiac muscle are anatomically interconnected which means when one finer contract, all contract

• Fibers of atria are electrically separated from fibres of ventricles

Heart murmur

• valve is damaged or doesn’t close properly which causes blood to be regurgitate causing noise

Cardiac muscle

• also known as myocardium

• All fibres are interconnected, so when one fibre contracts, all fibres contract

• Fibres of atria are electrically separated from fibres of ventricles

Electrical conduction in myocardial cells

• auto rhythmic cells spontaneously fire action potentials

• Depolarization then spreads through gap junctions

• Action potentials in contractile cells

Conduction system of heart

• heart inherent contractile rhythms originates in an area of specialized tissue located in the posterior wall of the right atrium

• Sino atrial mode is S.A. node

  process

  1. Sino atrial node

  2. Internode, pathways spread across both atria

  3. Atrio ventricular (AV) node lies in the inter atrial septum

     • only pathway for electric, conduction across connective tissues between atria and ventricles

  4. ventricular conduction system: AV node then AV bundle then left and right bundle branches then 2 bundles branch to many strands of purkinje fibers (spread through ventricles)

electrocardiography (ecg)

• records the wave of depolarization as it passes across the heart using electrodes on the surface of the body

• P wave= atrial depolarization

• QRS= atrial repolarization and ventricular depolarization

• T wave= repolarization of ventricles

• PR interval= time between onset of atrial and ventricular depolarization

• QT= duration of ventricular depol and repol

• PR segment= conduction through AV node and bundle

• ST segment= ventricular contraction

Arrhythmia

• irregularity in rhythm of heartbeat

• To diagnose looke at heart rate, amplitude and shapes of components of the ecg waveform and time intervals

• Tachycardia- hr faster than norm

• Over 100 bpm at rest

• Bradycardia-hr slower than normal

• Lower than 60 bpm at rest

• Fibrillation- electrocardiography is disorganized

  • atrial fibrillation heart still functions as a pump

  • Upside down regular ecg ie QRS peaks are on the bottom

  • Ventricular fibrillation- heart does not function as effective pump

  • Messy ecg

Blood supply to the heart

• heart muscle supplied by 2 major arteries which originated from aorta just above the aortic valve

• Left coronary artery and right coronary artery

• Large veins of the heart converge and empty into the right atrium

• Cardiac muscle is highly dependent on aerobic metabolism, it requires a rich blood supply.

• At rest, normal blood flow to the myocardium is 4% of total cardiac output

• During exercise, blood flow to heart stays about the same 4% of cardiac output. Cardiac output increases substantially with exercise, increasing flow of blood to the heart

• Approx 70-80% of oxygen is extracted from blood flowing in the coronary vessels compared to average 30% of other tissues

Blood vessel types

• artery

• Arterioles

• Capillary

• Venue

• Vein

Artery

• muscular and highly elastic

• Receives and propel high pressure blood flow

Arterioles

• muscular and well innervatee

• Vary resistance to blood flow

• Arteries under 0.5mm in diameter

• Through constriction or relaxation of the thick layer of smooth muscle in walls of arterioles, blood flow can be increased or decreased to various capillaries

• Arteries and arterioles constitute the High pressure part of circulatory system

Capillary

• thin walled and highly permeable vessels

• Exchange of materials such as nutrients/wastes and gases between blood and tissues

• All other organs of circulatory system exist to serve capillary beds

Venule

• thin walled and some fibrous tissue

• Collect blood from capillaries

• Small vessels that conduct venous blood from capillaries to veins

• The venules and the veins constitute the low pressure part of the circulatory system.

Vein

• fairly muscular and highly distensible

• Easily collapse or expand to maintain venous return

• Convey blood towards the heart

• Greater in diameter but thinner walled than arteries with which they travel

• Superficial and deep veins

• Have smooth muscle in their walls which allow them to change their diameter.

• Veins and venules constitute the low pressure of circulatory system

Pulse pressure

• difference between systolic and diastolic pressure readings in arteries

Valves

• found in those veins which carry blood against the force of gravity especially the veins of the legs

Mechanisms involved in return of blood to the heart

1. pressure difference between left and right atrium-120 mm Hg - 3mm Hg= 117mm Hg driving pressure

2. skeletal muscle pump: active muscles squeeze the veins and push blood towards the heart

3. Respiratory pump: decreased in thoracic cavity during inspiration which allows for easier blood return from lower portions of body via inferior vena cava to thoracic cavity then to right atrium of heart

Blood

• composed of red blood cells, white blood cells and platelets

• Suspended in a liquid plasma which makes up 50-60% of body volume

• Blood volume of average adult with a normal body composition is approx 8% of body mass

• Therefore, a person with a body mass of 70kg has a blood volume of approx 5.6 litres

• Blood volume is greater for larger, more endurance trained and heat acclimatized people

Plasma

• composed of 90% water and 10% solutes

Red blood cells(erythrocytes)

• biconcave discs about 7 microns in diameter

• Hematocrit: ratio of volume of blood cells to total volume of blood

• Expressed as percentage

• Usually 37-47% in females and 42-52% in males

• Red blood cells are made in red bone marrow in ends of long bones and flat bones

• Lifespan of RbC is 120 DAYS

• Contains hemoglobin which transport O2 and Co2

• Hemoglobin consists of 4 subunits, each contains one molecule of iron

• Normal values for hemoglobin

  • male: 140-160 grams per 1000 ml blood

  • Female: 120-140 grams per 1000 ml blood

Blood doping

• increasing RBC count and/or oxygen carrying capacity of blood

• Types

  • blood transfusion

  • EPO (or synthetic hormones)

  • Synthetic oxygen carriers

    alternative ways to increase RBC count

  • Hypoxia tents

  • Altitude training

• polycthemia vera= too many rbcs which lead to increased blood viscosity and clotting

Diffusion

• molecules go from high concentration to low concentration

• Movement of molecules across respiratory membrane are driven by diffusion

• Rate of diffusion can be increased by:

  • higher concentration gradient

  • Shorter diffusion distance

  • Higher temperature

  • Greater surface area

Sites of gas exchange

1. Alveolar capillary membrane in lung

   • net diffusion of O2 from alveoli to blood

   • Net diffusion of CO2 from blood to alveoli

2. Tissue capillary membrane in tissue

   • net diffusion of O2 from blood to tissue

   • Net diffusion of CO2 from tissue to blood

Partial pressure of gas in gas mixture

• partial pressure of a gas- pressure of a gas in a gas mixture is dependent on

  • total (barometric) pressure

  • Fractional concentration of that gas

• Example: at sea level, total pressure of all dry a,Brent atmospheric gas is 760mm Hg which equals to the barometric pressure

• Most important factor in determining gas exchange is the partial pressure (concentration) gradients of gasses involved

• Ambient air vs tracheal air vs alveolar air- partial pressure differences

• Functional residual capacity (frc) serves as a damper so that each incoming breath of air has only a small effect on the composition of the alveolar air

• Partial pressure of gasses in alveoli remains relatively stable

Henry’s law

• amount of gas that dissolves in a fluid is a function of 2 factors:

  1. Pressure of the gas above the fluid which is given by the gas concentration times the barometric pressure

  2. Solubility coefficient of gas-CO2 is 20.3 times more soluble in water than O2

Lung diffusing capacity

• diffusing capacity for oxygen is volume of oxygen that crosses the alveolar capillary membrane per minute per might between the alveolar air and pulmonary capillary blood

• Aside partial pressure gradients, diffusing capacity can be affected by other factors

  1. The thickness of respiratory membrane- length of the diffusion path

     • diffusing capacity is decreased in restrictive lung diseases such as pulmonary fibrosis or pneumonia

  2. Number of red blood cells or their hemoglobin concentration or both

  3. Surface area of respiratory membrane available for diffusion- diffusing capacity is decreased in emphysema

• Diffusing capacity can increase up to 3 times during heavy aerobic exercise

• Mechanisms:

  1. Increased lung volumes during exercise which increased surface area for diffusion

  2. Opening up of more capillaries in the lung and greater volume flowing through the lung

Transport of oxygen by blood

• 98% of oxygen in blood is carried by rbcs in chemical combination with hemoglobin

• Hb+O2= HbO2 (oxyhemoglobin)

• Other 2 percent in plasma

• One gram of hemoglobin saturated with 1.34 ml of O2

• In lungs PO2 is high

  • drives O2 exchange into plasma

  • High plasma PO2 drives O2 binding to Hb

• In tissues, PO2 is low

  • drives O2 exchange out of plasma

  • Low plasma PO2 drives O2 release from Hb

• Hemoglobin concentration equals 15.0 grams per 100ml of blood

• O2 carrying capacity would be 15.0 × 1.34ml/g= 20.1 ml of O2 per 100 ml of blood

• Percent saturation of hemoglobin with O2 relates the amount of O2 actually combined with hemoglobin to the maximum O2 capacity of hemoglobin

• Arterial blood at rest at sea level

  • hemoglobin is 97.5% saturated with O2

  • 97.5% × 20.1= 19.5 ml O2 per 100ml blood

• Venous blood at rest at sea level

  • hemoglobin is 75% saturated with O2

  • 75% x 20.1=15.1 ml O2 per 100ml blood

• Arteriovenous oxygen difference- (a-v)O2

• Represents how much oxygen is extracted or consumed by the tissues for each 100ml of blood perfusing them

• At rest

• (a-v)O2=19.5-15.1= 4.4 ml O2 per 100ml blood

• Hemoglobin acts as tissue oxygen buffer system

• Level of alveolar oxygen may vary greatly, from 60 to more than 500 mm Hg but saturation is maintained

• Due to the flat shape of oxyhemoglobin dissociation curve

• PO2 in tissue doesn’t vary more than a few mm Hg but saturation can vary widely due to steep portion of curve

Bohr effect

• increased body temperature

• Increased PCO2

• Decreased pH

• Shift oxyhemoglobin right which releases more oxygen at the tissue level for a given PO2

Divisions of nervous system

Central nervous system-brain and spinal chord

Peripheral nervous system-after ent and efferent divisions

Spinal chord

• long cylinder of nerve tissue which extends down from brain stem to second lumbar

• 45cm long and 2cm in diameter

• Protected by vertebral column and associated ligaments and muscles

• Spinal meninges (consists of Dura mater(outer layer), arachnoid membrane (middle layer) and pia mater (inner layer))

• The cerebrospinal fluid

• Provide 2 way conduction pathway to and from brain and its major reflex Center

• Paired spinal nerves arise from spinal chord

• 31 pairs of spinal nerves are attached to spinal chord

• 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal

• Enlarged in 2 regions

  • cervical enlargement which extends from C4 through T1 segments of spinal chord

  • Lumbosacral enlargement which extends from T11 through L1 segments of spinal cord

• Plexus= network of converging and diverging nerve fibers or blood vessels.

• Brain and spinal chord are composed of gray matter and white matter

• Nerve cell bodies lie and constitute the gray matter

• Interconnecting tracts of nerve fibers (axons) form white matter

• Each spinal nerve has a dorsal root and a ventral root connected to spinal chord

• Dorsal roots contain Afferent (sensory) fibers that carry info from periphery to spinal chord and brain

• Central roots contain efferent (motor) fibers to skeletal muscle

• Cell bodies of motor axons making up the ventral roots are located in ventral gray horns of spinal cord

• Cell bodies of sensory axons making up dorsal roots are outside of spinal cord in dorsal root ganglia

• Ganglion: collection of nerve cell bodies located outside of CNS

Spinal cord injury

• often result of trauma to spinal cord but can also be associated with congenital or degenerative disease

• Causes include

  • Motor vehicle accidents

  • Violence

  • Falls

  • Recreational activities

• Transecting (complete cut) of spinal cord

  • results in loss of all sensation and voluntary movement inferior below point of damage

• Quadriplegic- if cord transected superior to C5

• If transaction above C4, patient may die of respiratory failure

• Patient paraplegic

  • paralysis of both lower limbs- transaction occurs below cervical segment of spinal chord

• Deficiency of blood supply to spinal chord caused by fractures, dislocations, atherosclerosis affect its function and can lead to muscle weakness and paralysis

• When brain or spinal cord damages, most cases injured axons don’t recover

Muscle sense organs

• proprioceptors

  • conduct sensory information to the CNS from muscles, tendons, ligaments and joint - kinesthetic sense

  • Kinesthetic sense: gives info about location of parts of our body in relation to environment

• Types

  • muscle spindles- change in length

  • Golfi tendon organ- change in tension

  • Joint receptors- change in angle

Muscle spindles (ex: patellar tendon tap)

• structure- several modified muscle fibers

• Spindle fibers lie parallel to regular muscle fibers

• Function: sends info to CNS regarding degree of muscle stretch- activation of exact number of motor units to overcome a given resistance

• With increasing degrees of stretch of muscle spindle, frequency of impulse transmission up the Afferent neuron to spinal chord increases

• 3 methods of activating alpha motor neurons to contract muscles

  1. Tonic stretch: concerned with final length of muscle

  2. Physic stretch: spindle responded to velocity of change of length

  3. Gamma system- gamma efferent fibers innervate contractile ends of intramural fibers

     • when alpha motor neurons activated, gamma motor neurons also activated (coactivation)

     • Gamma system provides mechanism for maintaining the spindle at peak operation at all muscle lengths

     • Help maintain muscle spindle sensitivity

• Stretch reflex

  • muscle spindles distributed throughout muscle. Densities vary with degree of control required by muscle

  • Reflex Arc- reflex pathway

    • 5 components

    • Receptors(muscle spindle)

    • Afferent neuron

    • Integrating Center(spinal cord)

    • Efferent neuron (both gamma and alpha)

    • Effector (muscle contraction)

Stretch reflex

• muscle spindles distributed throughout muscle. Densities vary with degree of control required by muscle

  • Reflex Arc- reflex pathway

    • 5 components

    • Receptors(muscle spindle)

    • Afferent neuron

    • Integrating Center(spinal cord)

    • Efferent neuron (both gamma and alpha)

    • Effector (muscle contraction)

Golgi tendon organs

• Location- encapsulated in tendon fibers near junction of muscle and tendon fibers

• In series with muscle fibers rather than in parallel as are muscle spindles

• When muscle contracts, GTO is stretched

• Functions- firing rate if GTO is very sensitive to changes in tension of muscle

  1. Sensory input from GTO about tension produced by muscles is useful for variety of motor acts such as maintaining a steady grip on an object

  2. When stimulated by excessive tension or stretch-send sensory information to CNS which cause the contracted muscle to relax( reflex inhibition)

     • protect muscle and it’s connective tissue harness from damage due to excessive loads

Joint receptors

• supply information to CNS concerning joint angle, acceleration of joint, pressure and pain

Control of motor functions

• cerebral cortex and cerebellum are main centres employed in learning new motor skills. These areas of brain initiate voluntary control of movement patterns

Primary motor cortex

located at the rear of the frontal lobe of the cerebral cortex.

• Stimulation of different areas of the primary motor cortex brings about movement in different, specific areas of the body.

• Contains the motor homunculus. However, no coordinated movement can be elicited.

• The motor cortex on each side of the brain primarily controls muscles on the opposite side of the body.

• The primary motor neurons cross over in the pyramids of the medulla

Cerebral cortex

• motor homunculus

• Parts of the body that are affected by cerebral cortex

• Corticospinal tract

• long axons which carry impulses from the primary motor corteX where their cell bodies are located directly to lower motorneurons in spinal cordàspinal nerves

• The corticospinal system primarily mediates performance of fine, discrete, voluntary movements of the hands and fingers.

Premotor cortex

• One of the three higher areas that command the primary motor cortex.

• Located on the lateral surface of each cerebral hemisphere in front of the primary motor cortex.

Somatosensory cortex

The site for initial cortical processing of pressure, touch, heat pain and proprioceptive input

• Located in the anterior section of the parietal lobe, immediately behind the central sulcus.

• Each region within the somatosensory cortex receives sensory input from a specific area of the body.