Review

1
(No Transcript)
2
Medical Imaging
3
X-Rays

• X-rays directed from source into the anatomy to
  be imaged
• Some energy absorbed, some x-rays are
  scattered/deflected
• Image formed by detecting x-rays as they exit the
  body
• Grayscale depending on energy of emerging x-ray
• More energydarker image

4
Ultrasonic Imaging

• High-frequency pulses are reflected and scattered
  as they travel through the tissues
• Transducer/Probe is both a transmitted and
  receiver
• Detects strength of echo and time delay
• Distance of an object from transducer (½)tc
• t time delay of echo
• c speed of sound in tissue
• 1450-1520 m/s
• A-mode displays amplitude of echos along a
  single line
• M-mode displays amplitude of echos as light
  /dark pixels

5
(No Transcript)
6
Doppler Ultrasound

• The Doppler Effect change in frequency of a wave
  due to the motion of its source or receiver
• Flowing blood reflects soundwaves and shifts the
  frequency of received wave
• ?f proportional to v
• ?f 2fvcos(?)/c

7
Magnetic Resonance Imaging (MRI)

• Provides detailed evaluation of soft tissue
  contrast of muscle, tendons, ligaments,
  cartilage, and bone marrow
• Normal anatomy and injured tissue
• Most important modality behind physical exam and
  plain radiographs

8
The Basics

• Conventional imaging modalities density of
  tissue and reflection/absorption of beam/wave
• MRI number of free water protons in tissue
• Protons precess at a rate directly proportional
  to the strength of magnetic field
• Magnetic field gradient applied to patient
• Distinguishes slices to be imaged

9
The Basics

• Series of radiofrequency (RF) pulses applied to
  tissue
• Protons change their alignment relative to
  external magnetic field
• RF pulse stops, then protons realign with
  external magnetic field
• Releases energy which creates the MRI image
• Tissues distinguished by speed of re-alignment

10
Muscle Physiology
11
The Motor Unit

• Motor Unit a motor neuron and all the fibers it
  innervated
• Axon
• Long fiber extending from cell body
• Bundles of axons nerve
• Can be several feet long (spinal cord to
  hand/foot)
• Carries electrical impulses
• Action potential

12
Myofibrils

• Individual sarcomeres bounded by fibrous z-lines
• A-bands width of thick filaments
• I-bands non-overlapped actin chains
• Ususally at the end of sarcomere
• H-bands non-overlapped portion of thick filament

13
Sliding Filament Theory of Muscle Contraction

• Myosin filaments bind to Actin filaments via
  cross-bridges
• Complex process
• Ca and ATP needed

14
Sliding Filaments

• ATPase cleaves ATP into ADP Pi on cross-bridge
  head
• Ca binds and moves tropomyosin
• Cross-bridge binds to actin
• ADP and Pi released
• Head tilts and pulls actin filament
• new ATP binds releases head resets head back
  to 1)

2
1
3
6
4
5
15
Heres the Whole Process

• Stimulus excites neuron
• AP travels down axon
• At terminal, AP triggers release of Ca
• Ca triggers release of neurotransmitters
• Neurotransmitters diffuse across synapse
• AP created at muscle fiber membrane

• AP triggers release of Ca into myofibril
• Ca moves tropomyosin
• Cross-bridge cycle begins
• Muscle contracts
• Cross-bridges detach
• AP stops Ca reabsorbed

16
Length-Tension Relationship

• Force generating capacity of muscles depends on
  length of fibers

17
Type I Muscle Fiber

• Slower to reclaim Ca
• Slow conduction velocity
• Small fibers
• Few fibers per motor unit
• Responsible for fine movements, posture

18
Type I Muscle Fiber

• Aerobic metabolism
• Converts glycogen into ATP in the presence of O2
• Many mitochondria, myoglobin
• Many capillaries
• Large supply of energy
• Relatively slow, but efficient ATP production
• Resistant to fatigue

19
Type II Muscle Fiber

• High conduction velocity
• Relative to Type I still slow compared to nerve
• Large fibers
• Many fibers per motor unit
• Responsible for gross movements

20
Type II Muscle Fiber

• Anaerobic Glycolysis
• Fastest way to derive energy
• O2 not needed
• Not very efficient
• Only a small supply
• Produces lactic acid
• Fatigues easily
• Type IIb Fast Twitch Hybrid

21
Biomechanics
22
Static Analysis
Fm ? Fcx ? Fcy ?
23
The Circulatory System
24
The Heart

• Two pumps in series
• Pulmonary circuit
• Sends/receives blood to/from lungs
• Systemic circuit
• Sends/receives blood to/from rest of body
• Unidirectional flow through each circuit
• Due to unidirectional flap valves

25
The Cardiac Cycle

• Systole ventricular contraction
• Isovolumic contraction time between ventricular
  systole and opening of the semilunar valves
  rapid incr. in pressure
• Ejection opening of semilunar valves blood
  squeezed out of ventricle
• Diastole ventricular relaxation elastic recoil
  of large arteries blood propulsion
• Isovolumic relaxation time between the closing
  of the semilunar valves and opening of the AV
  valves rapid decr in pressure
• Rapid filling LV pressure lt LA pressure blood
  drawn into ventricle
• Diastasis slow filling from RA and LA
• Atrial systole atrial contraction

26
Performance Measurements

• Stroke Volume amount of blood pumped by LV in
  one contraction EDV-ESV
• Ejection Fraction SV/EDV
• Portion of EDV that is pumped out
• Ventricle not completely emptied

27
Pressure-Volume Relationship
28
Force Generation

• Na, K and Ca are essential for contraction
• Force ? w/ extracellular Ca
• Force ? w/ ? preload and/or ? afterload
• Preload the amount of stretch in the muscle
  fiber ? EDV
• Stroke Volume also ? - Frank-Starling Law
• Afterload resistance to ventricular ejection ?
  aortic pressure
• SV ?

29
Cardiac Output

• CO HR x SV
• HR regulated through pacemaker activity
• SV related to cardiac performance
• Main Goal maintain blood flow to vital organs,
  e.g. maintain appropriate BP
• Not independent of each other
• Changing one will produce a change in the other
• Sympathetic and parasympathetic influences

30
Hemodynamics
31
Poiseuilles Law

• In steady, laminar flow, Q is influenced by many
  factors
• Q directly proportional to pressure difference
  and tube radius
• Q inversely proportional to length of tube and
  fluid viscocity
• Q ?(Pin Pout)r4 /8?L

32
Resistance

• Q ?(Pin Pout)r4 /8?L
• Resistance to flow 8?L/?r4
• Just like a circuit
• In series R R1R2R3
• In parallel 1/R 1/R11/R21/R3

33
Mean Arterial Pressure

• Mean arterial pressure (MAP)
• Average BP during a single cardiac cycle
• Measure of the perfusion pressure to the organs
• MAP Pd (Ps-Pd)/3

34
The Respiratory System
35
Basic Gas Laws

• Partial pressure
• Total pressure of all species in a gas mixture is
  the sum of the individual pressures that each
  species would exert if alone
• Concentration of each species in the mixture is
  equal to the ration of the partial pressure and
  the total pressure
• Partial pressure of a gas dissolved in a liquid
  is equal to the partial pressure of that gas in a
  gas mixture in equilibrium w/ the liquid

36
Alveolar Ventilation

• Alveolar ventiliation amount of fresh air that
  reaches the alveoli w/ each breath (VA) always lt
  total ventilation
• Some does not reach and stays in the airways
• Anatomic Dead Space (Vd) about 2 ml/kg

37
Relating VA to Metabolic Rate (VO2, VCO2)

• VO2 VE x (O2I O2E)
• VCO2 VE x (CO2I CO2E)
• In terms of VA
• VO2 VA x (O2I O2A)
• VCO2 VA x (CO2A CO2I)
• Expressing as partial pressures
• PAO2 PIO2 (VO2/VA) x P
• PACO2 PICO2 (VCO2/VA) x P

38
Into the bloodstream

• If PACO2 (or PaCO2)is known, PaO2 can be
  calculated
• PaO2 FIO2 x (PB-PH2O) PaCO2 x (FIO2
  (1-FIO2))/R
• Alveolar Gas Equation

39
O2 Transport in the blood

• Mainly in RBCs
• Hematocrit volume of blood that contains
  RBCs (normal 35 50)
• Altitude adaptations
• Blood doping
• Once in the blood, O2 binds to hemoglobin in the
  RBCs
• Hemoglobin enhances O2 carrying capacity of blood
• Low O2 solubility in plasma
• Hb 150 g Hb/L blood
• O2 capacity of Hb 1.34 ml O2/g Hb
• Only 25 of bound O2 dissociates thru systemic
  circulation
• Keeps PO2 difference betw capillaries and tissues
• Holds some O2 in reserve for emergencies

40
O2 Saturation (SO2)

• The amount of O2 bound to Hb for a given partial
  pressure of O2 in the blood
• In arterial blood (PO2 90 to 100 mmHg), SO2
  97
• Remaining 3 dissolved in blood
• Total conc. O2 (O2 bound to Hb) (O2 dissolved)

41
Ficks Principle Revisited

• Concentration of O2 can be estimated from SO2
  curve
• VO2 q2
• CO VO2 / (O2pv-O2pa)

42
Tissue Oxygenation

• Oxygen transported in 2 steps
• From alveolar gas to RBCs
• From RBCs to mitochondria in cells
• Transport occurs by simple diffusion
• Ficks Law

43
Carbon Dioxide Transport

• CO2 is a chief product of cellular metabolism
• Eliminated in the lungs gas exchange
• Carried in the blood in three forms
• As dissovled CO2 in the blood
• As bicarbonate ion HCO3-
• Bound to Hb and proteins carbamino CO2

44
(No Transcript)
45
Exercise Physiology
46
Immediate Energy - PCr

• PCr ADP ? ATP Cr
• PCr stored in the muscle tissue
• Provides energy for short, maximal efforts
• 100m sprint, weight lifting, etc.
• Cannot be sustained very long

47
Short-term Energy - Glycolysis

• Glycogen ? ATP no O2
• Lactate accumulates after 60-180 sec of maximal
  exercise
• Oxidized/neutralized in muscle fibers
• Remains stable at low intensity exercise, ? w/
  higher intensity
• Blood lactate threshold
• Occurs at 55 VO2max

48
Long-term Energy - Aerobic System

• Glycogen O2 ?ATP CO2 H2O
• Provides most of the energy when exercising over
  a few minutes
• Energy needs and energy expenditure are in steady
  state
• No accumulation of lactate
• Some oxidized some converted to glucose in the
  liver

49
(No Transcript)
50
The Wingate Test 30 sec. of hell

• Anaerobic power test on a cycle ergometer
• Resistance set to 7.5 of body mass
• 30 sec. max. effort
• Peak power max power generated
• Anaerobic fatigue - power decline during test
• Rate of Fatigue rate of decline
• Anaerobic capacity total work done during test

51
VO2max Maximal Aerobic Capacity

• Measures VO2 with increasing work rate
• VO2max point where VO2 does not increase w/
  work rate
• Done on treadmill or bike
• Quantitative assessment of an athletes maximal
  capacity for aerobic ATP synthesis

52
Ventilation and Metabolism

• Ventilation in steady state ? linearly w/ VO2
• Mostly ? tidal volume at higher intensity ?
  freq.
• In non-steady state, ventilation ?
  disproportionately - ventilatory threshold
• Not purely aerobic exercise Lactate removal

53
CO Distribution
54
? O2 Extraction w/ Exercise

• More O2 removed
• Greater a-v O2 difference
• Results in ? VO2
• Ficks Eqn
• Central and peripheral factors
• Redirction of CO
• Ratio of muscle fibers to capillaries
• ? size and of mitochondria