Week 36- Lower Limb and Soft Tissue Flashcards
What are some haemodynamic changes in response to exercise?
- Increase –> HR, SV, CO
- Redistributed blood flow
- Blood mobilised from venous pools
What are some respiratory changes in response to exercise?
- Increase –> Tidal volume, respiratory rate and minute ventilation
- Bronchodilation
What is the change in the blood in response to exercise and why?
Blood glucose increased –> energy required by muscles
What is some renal changes in response to exercise?
Reduction in renal blood flow and GFR
Increased reabsorption of NaCl and water
What is some thermoregulation undertaken during exercise?
Increased dissipation of heat via sweat evaporation
What is Stroke volume? SV
Blood volume ejected from each ventricle (its equal for each) during a single cardiac contraction
At rest 60-80mL –> exercise can boost to 180mL
What is Cardiac output and its formula?
The amount of blood pumped per minute:
CO = HR x SV
Is heart rate and stroke volume altered by physical health training by athletes etc?
Stroke volume increases a lot with training
HR –> returns to rest quicker
How does muscle contraction shift venous pooled blood to the heart?
Contraction mechanically pushes blood through the veins
How does the increase in venous return lead to an increase in CO?
- Increase venous return
- Increased myocardial contractibility (frank starling law)
- Rise in stroke volume
- Rise in cardiac output
What can predispose someone to DVT?
Long periods of inactivity in sitting position –> slow blood flow –> pooling –> thrombus formation
How does blood pressure rise from rest during aerobic exercise vs heavy load exercise?
Aerobic –> moderate increase
Heavy load – large increase
What is the equation for blood pressure?
BP = CO x TPR (total peripheral resistance)
What is the exercise pressor reflex?
Pressor reflectory response triggered by contracting muscles. Can be triggered by both mechanically and metabolically sensitive muscle afferents.
What is the result of the mechanoreflex and metaboreflex within the exercise pressor reflex?
Mechano –> immediate rise of Arterial Pressure initiated by muscle deformation or stretch
Metabo –> delayed rise in Arterial Pressure following stimulation of muscle chemoreceptors by metabolites (eg lactate, K+, ATP, H+, prostaglandins)
What are the two key baroreflex receptors?
Glossopharyngeal nerve and vagus nerve
How does an increase in aterial pressure drive the baroreflex?
- AP rise
- Glossopharyngeal and vagus signalling
- Brainstem:
- activation of cardiac vagal neurons
- inhibition of cardiac and vascular sympathetic neurons - Increase in cardiac vagal activity and decrease in cardiac and vascular sympathetic activity.
- More vagus = more Acetylcholine release to cardiac sites
Less sympathetic means less NA release to cardiac sites and vascular sites
- HR falls and vasodilation occurs
- CO declines
- AP falls
What is the mechanism of the bainbridge (aterial) reflex?
- Increase in venus return (increased CVP and aterial pressure)
- Activation of atrial and pulmonary vein stretch receptors
- Signal sent to cardioregulatory and vasomotor centres of the medulla oblongata
- Cardiac vagus signal decreased
- Cardiac sympathetic signal increased - HR increases
What are some intrinsic autoregulatory mechanisms in exercising muscle?
- Exercise = increase in energy demand + increase in metabolite production
- Reduced pO2
- Decreased ATP
- Increased lactate
- Increased pCO2
- Reduced pH - All these factors result in local vasodilation
What is the main factor for autoregulation in coronary blood flow?
Hypoxia –> but other factors include CO2 increase and fall in pH
What is the mechanism driven by hypoxia in cardiac myocytes?
- Hypoxia
- Breakdown of ATP in cardiac myocytes
- Increased adenosine
- Adenosine activates A2 receptors on vascular smooth muscle
- Activation of K(ATP) channels
- Hyperpolarisation
- Smooth muscle relaxation
- Vasodilation
What is the equation for minute ventilation?
VE (total gas entering the lung per minute = TV (tidal volume = normal volume of air displaced in one breath) x FR (resp rate)
How does blood pH and pCO2 affect alveolar ventilation?
pCO2 has a much greater increase
Why must renal adjustments be made during exercise?
Exercising causes a rise in BP and sweating –> without renal compensation this increased fluid loss would lead to dehydration
What renal modifications are made during exercise?
- Fall in GFR
- Increase in NaCl and water reabsorption in kidneys
How does the renal system changes during exercise happen?
Reduced GFR:
1. Activation of renal sympathetic nerves and release of adrenaline from adrenals
- Drives constriction of renal arterioles and afferent arteriols
- Fall in renal blood flow (up to 25% of normal)
- Reduces GFR
Preservation of fluids:
1. Release of aldosterone from adrenals and release of ADH from the posterior pituitary
- Aldosterone = increased NaCl reabsorption
ADH = increased thirst and H2O reabsorption - Preservation of fluid and electrolyte levels
What thermoregulatory changes are done during exercise and how are they achieved?
- Increased sweating rate –> sympathetic control
- Increased cutaneous blood flow –> sympathetic control
Both of these dissipate heat
What is the aim of warming up before exercise?
Reduce likelihood of tendon and muscle injury
What is the physiological effects both primary and secondary?
Primary –> increase in muscle and core temperature and muscle blood flow
Secondary –>
- Faster muscle contraction/relaxation
- Lower viscous resistance in muscle tissues
- Facilitated O2 delivery
- Facilitate nerve transmission
- Increase muscle metabolism
- Coronary blood supply increases with a lag
What effects on the knee joint does collateral ligaments tears have?
Reduces the lateral stability of the joint
What effects does an ACL or PCL tear have on the knee joint?
Reduction in antero-posterior stability
What is the role of the ACL and how is it damaged?
ACL prevents drawing of tibia against femur anteriorly –> normally damaged with rotational force between tibia and femur
What is the role of the PCL and how is it damaged?
PCL prevents anterior displacement of femoral condyles on tibia plateau –> normally damaged by backwards force on tibia while there is forward momentum on femur
How to test for ACL and PCL damage?
ACL –> hip at 45 degrees, knee at 90 degrees –> apply explosive anterior force at the joint
PCL –> hip at 45 degrees, knee at 90 degrees –> apply explosive posterior force at the joint
Positive test for both if there is significant movement in the forced direction
What are the two common fractures of the femur?
Neck of femur fracture
Femoral shaft fracture
What demographic normally experience femoral neck fractures?
Common in elderly and young high energy
Why is one of the main complication of femoral neck fractures avascular necrosis?
Because the head is supplied mainly by the medial and lateral circumflex femoral arteries, which both run up the neck to supply the head. A fracture can interfere with this circulation leading to a cut off of blood and necrosis.
What demographic normally experience femoral shaft fractures?
High energy injuries or low energy elderly
Is a femoral shaft fracture life threatening? Why?
Yes. Receives large supple of blood. Can cause severe internal haemorrhage
What typically causes a patella fracture?
Direct blow to the patella
What is some examination findings of patella fracture?
Knee extension failure amount other obvious pain swelling etc
What demographics are at risk of knee dislocation (tibiofemoral joint)?
High energy and or high BMI
What are the different types of knee dislocation and their corresponding associated injury?
Hyperextension –> PCL tear
Dashboard –> popliteal artery injury
Varus/valgus force –> common peroneal nerve injury
What is the tibial plateau?
Flat surface of the distal tibia where the femur articulates
What demographics normally see tibial plateau fractures?
Males in 40s (high energy) and women in 70s (low energy)
What kind of fractures may be at the tibial plateau?
Lateral condyle (outer) Medial condyle (inner) Bicondylar (both)
What conditions may follow a tibial plateau fracture?
Post traumatic arthritis, lateral meniscus tear, ACL tear, compartment syndrome
How quickly does compartment syndrome need to be treated?
ASAP –> within 4-6 hours there is muscle and nerve death
What does the lateral and medial malleolus refer to?
Lateral –> the inner bone of the ankle joint –> fibula
Medial –> the outer bone of the ankle joint –> tibia