Week 5

Question 1

Structure/Layers of the heart? and basic function of heart and layers?

Answer 1

The heart is a muscular organ that is responsible for receiving blood supply via coronary arteries and pumping blood throughout the body to deliver oxygen and nutrients and remove waste.
It has a high oxygen and nutrient demand, especially in the myocardium

Heart wall layers:

Epicardium – Outer layer; protective membrane

Myocardium – Middle layer; thick muscular layer responsible for contraction and pumping action

Endocardium – Inner layer; smooth lining that reduces friction within chambers

Question 2

What is myocardial infarction?

Answer 2

blockage in coronary blood flow resulting in cell damage
Exercise training helps protect heart damage during MI

Question 3

The heart wall structure, characteristics and functions?

Answer 3

Epicardium - Serous membrane including blood capillaries, lymph capillaries and nerve fibres, lubricates outer covering

Myocardium - Cardiac muscle tissue separated by connective tissues and including blood and lymph capillaries, and nerve fibres, provides muscular contractions to eject blood

Endocardium - Endothelial tissue and a thick subendothelial layer of elastic and collagenous fibres, serves as a protective inner lining of the chambers and valves.

Question 4

Heart Muscle vs Skeletal Muscle – Key Comparison

Answer 4

Contractile Proteins: Actin & Myosin (both)

Fiber Shape: Heart – short, branching; Skeletal – elongated, no branching

Nuclei: Heart – single; Skeletal – multiple

Z-Discs: Present in both

Striations: Present in both

Cellular Junctions: Heart – intercalated discs; Skeletal – none

Connective Tissue: Heart – endomysium; Skeletal – epimysium, perimysium, endomysium

Energy Production: Heart – aerobic (primary); Skeletal – aerobic & anaerobic

Calcium Source: Heart – SR + extracellular; Skeletal – SR only

Neural Control: Heart – involuntary; Skeletal – voluntary

Regeneration Potential: Heart – none (no satellite cells); Skeletal – some (satellite cells present)

Question 5

Electrical activity of the heart - Conduction system?

Answer 5

Starts at Sinoatrial node (SA) - Pacemaker, initiates depolarization. Originates and travels across atrial wall from SA to AV

Then to Atrioventricular (AV) node - Passess depolarisation to ventricles, brief delay to all ventricle filling. Passes through AV bundle through fibrous skeleton into interventricular system

Bundle branches - connect atria to left and right ventricle. AV bundle divides into left and right bundle branches where AP descends to apex of each ventricle along branches

Finally purkinje fibres - spread wave of depolarisation throughout ventricles, AP carried by fibres from branches to ventricle walls.

Question 6

Electrocardiogram (ECG)

Answer 6

P Wave - Atrial depolarisation
QRS complex - Ventricular depolarisation and atrial repolarisation
T Wave - Ventricular repolarisation

Question 7

Rate of intrinsic pacemaker?

Answer 7

Around 100 bpm

Question 8

Diagnostic use of ECG during exercise?

Answer 8

Observing ECG and BP changes can evaluate cardiac function

ST segment depression suggests myocardial ischemia

Atherosclerosis which is fatty plaque narrows coronary arteries reducing blood flow to myocardium - myocardial ischemia

Question 9

How does exercise protect the heart?

Answer 9

Reduces incidence of heart attacks/reduces survival of them

Reduces amount of myocardial damage from HA improving antioxidant capacity and function of ATP sensitive potassium channels

Question 10

Evaluating collapsed athlete

Answer 10

Assess consciousness by checking for pulse which determines the next 1 of 2 paths.

If no pulse = cardiac arrest = life support measure such as CPR which articulates blood to tissues for them.

Time to initiation of chest compressions can determine factors for cardiac arrest

Question 11

Improving survival outcomes.

Answer 11

67% survival from SCA with immediate defibrillation.
Nearly 4x more neurologically intact survival rate

Question 12

Exercise stress test for diagnosis of Coronary heart disease?

Answer 12

Tests can detect restricted coronary flow

Question 13

Coronary Circulation?

Answer 13

• Heart muscle is highly oxidative (high O₂ demand)
• Adenosine is the key metabolic vasodilator- Also β-adrenergic vasodilation (via ANS)
• Blood flow mainly occurs during diastole
• At rest, 80% of coronary flow takes place during diastole because of vessel compression during systole.
• Heavy exercise: 40-50% of flow occurs in systole
• Chronotropic [heart rate increases]
  Inotropic [contractility increases]

Question 14

Coronary circulation in exercise?

Answer 14

• Abundant coronary blood supply to highly oxidative cardiac muscle
• High oxygen extraction
• Metabolic control principally via adenosine
• Flow mainly during diastole
• High potential for ischaemia

Question 15

Anatomy and role of circulatory system?

Answer 15

Arteries - Blood delivery
Small arteries/arterioles - flow regulation
Capillaries - fluid / nutrient exchange
Venules - collection
Veins - Return

Question 16

Anatomy of peripheral circulation in decreasing size?

Answer 16

Conduit arteries - several mm
Feed arteries - about 1 mm
Resistance arteries 150-300 um
Resistance arterioles - 30-15- arterioles
Terminal arterioles 10-30um
Capillaries 4-6 um

Resistance is higher the lower the radius

Question 17

Aspects that control vasodilation/constriction?

Answer 17

Neural - SNS = adrenaline
Hormonal = similar to above, norepinephrine
Myogenic = flow and pressure varies depending on what is needed eg exercise
Mechanical - Skeletal muscle pump/moving
Metabolic
Endothelial derived relaxing factors (EDRF)

Question 18

Metabolic regulation of resistance vessels?

Answer 18

Blood flow increases in relation to the metabolic activity of a tissue / organ –
HYPERAEMIA

such as
* Tissue hypoxia
* CO2 increase
* pH decrease
* lactate production
* breakdown products of ATP
- e.g. adenosine, inorganic phosphate
* potassium
* osmolality

Question 19

Endothelial derived relaxing factors (EDRFs)

Answer 19

Blood flow creates shear stress on endothelial cells, triggering the conversion of L-arginine to nitric oxide (NO). NO promotes vasodilation and supports vascular health. In many cardiovascular diseases, NO production is impaired, reducing vessel function.

Arachidonic acid is converted into prostaglandins (PGs), which cause inflammation.

Short-term: Beneficial—boosts blood flow and aids muscle recovery

Long-term: Harmful—leads to chronic inflammation increases blood flow which helps muscle recovery.

Question 20

Redistribution of Blood Flow During Exercise?

Answer 20

Increase blood flow to working skeletal muscle.
* At rest, 15 to 20% of cardiac output to
muscle.
* ↑ to 80 to 85% during maximal exercise.

Decrease in blood flow to less active organs.
* Liver, kidneys, GI tract.
* Redistribution depends on metabolic rate.
* Exercise intensity.

Question 21

Regulation of Local Blood Flow during Exercise?

Answer 21

Skeletal muscle vasodilation causes decrease vascular resistance
This is also known as Autoregulation (blood flow regulation) which controls based off of needs.
* Blood flow increases to meet metabolic demands of tissue.
* Magnitude of vasodilation in proportional to the size of recruited muscle
mass.
* Due to changes in local factors (Increase nitric oxide, prostaglandins, ATP and
adenosine).

Vasoconstriction to visceral organs and inactive tissues increases vascular resistance
* SNS vasoconstriction - due to release of hormones such as norepinephrine etc
* Blood flow reduced to 20 to 30% of resting values

Question 22

Redistribution of cardiac output aided by catecholamines?

Answer 22

Circulating levels of noradrenaline and adrenaline increase during
exercise and act to vasoconstrict in most organs.

‘Noradrenaline spillover’ from muscle represents SNS activation

Adrenaline:
* Dilates skeletal muscle blood vessels
via β receptors in light exercise
* Vasoconstricts via α receptors in heavy
exercise as more blood is needed

Question 23

Cardiac output redistribution during exercise?

Answer 23

Skeletal muscle can take up to 90% of cardiac output at maximal exercise

Other major users of cardiac output in exercise – skin, coronary circulation

Question 24

Circulation through ‘special’ regions during exercise

Answer 24

• Sympathetic vasoconstriction in inactive
  organs (resting skeletal muscle, skin,
  splanchnic, renal)
• Metabolic vasodilation in active organs
  (active skeletal muscle, coronary)
• Thermoregulatory vasodilation in skin
• BUT: In severe exercise – competing
  demands of active muscle and
  thermoregulation and need to maintain
  blood pressure

Question 25

What is Splanchnic circulation?

Answer 25

The splanchnic circulation supplies blood to the liver, GI tract, pancreas, and spleen. 30% of the blood comes via the hepatic artery (from the aorta) 70% via the portal vein (draining GI organs) This region holds about 20–25% of total blood volume

Question 26

Splanchnic circulation during rest vs during exercise?

Answer 26

Flow = 1500 ml/min, 25% of CO2 vs 350 ml/min 5% of CO2 O2 Consumption = 50-60ml/min vs 50-60ml/min O2 Extraction - 15-20% vs 75% Blood flow decreases through sympathetic vasoconstriction and circulating catecholamines Oxygen extraction increases to compensate

Question 27

Splanchnic Circulation & Exercise Response?

Answer 27

During exercise: Splanchnic blood flow decreases significantly Blood is redirected to muscles and the heart to meet increased metabolic demands Flow returns to baseline post-exercise Physiological effects: Vasoconstriction in splanchnic vessels helps increase venous return by shifting blood back to the heart Vasoconstriction is more intense during exercise in heat, allowing more cardiac output to be directed to the skin for cooling Temporary reduction in GI blood flow also limits digestive activity to prioritize active tissues

Question 28

Skin(cutaneous) circulation ?

Answer 28

Rest - 100-300ml/min per m^2 of body surface Max - 7-8 L/min per m^2 of body surface More during max to maintain thermoregulation eg sweating during exercise by redirecting blood to skin

Question 29

Sympathetic neural control of skin blood vessels?

Answer 29

1. Adrenergic vasoconstrictor (non-hairy skin e.g. palms, sole of foot, lips) Adrenergic: noradrenaline as neurotransmitter 2. Cholinergic vasodilator (hairy skin) Cholinergic: acetylcholine as neurotransmitter

Question 30

Skin (cutaneous) circulation – thermoregulation?

Answer 30

Cold stress leads to vasoconstriction (VC) Heat stress leads to vasodilation (VD) Vasoconstriction = sympathetic constrictor activity Increases (Adrenergic) Vasodilation = sympathetic constrictor activity decreases (non-hairy) = sympathetic dilator activity increases (hairy) (Cholinergic

Question 31

Skin circulation during exercise ?

Answer 31

During dynamic exercise, active vasodilation occurs at a higher threshold than during heating at rest Mechanism of active vasodilation in exercise (hairy skin) sympathetic cholinergic nerves and nitric oxide, peptides

Question 32

Skin (cutaneous) circulation – blood pressure regulation?

Answer 32

Skin circulation can determine the performance of the heart In heat, blood flow is shifted from core to surface Muscle pump cannot assist in aiding venous return Filling of heart is reduced. Vasoconstriction must occur to maintain BP. BUT – in extreme conditions, skin vasoconstriction compromises thermoregulation

Question 33

Skin (cutaneous) circulation – integrative control?

Answer 33

Reflex inputs: Thermoregulatory = internal, skin temp Non-thermoregulatory = baroreceptors, exercise Sympathetic controllers: Vasodilator and Vasoconstrictor Central modifiers: Circadian rhythm, hydration, acclimatization, menstrual cycle, training

Question 34

Summarised Skin circulation?

Answer 34

Use diagram. ABC In dynamic exercise - competing influences * Vasoconstriction at onset with sympathetic activation (A) * Active vasodilation occurs at a threshold core temperature to lose heat (B) * Vasoconstriction during prolonged exercise to maintain central blood volume and venous return (C)

Question 35

Renal blood flow Rest vs Exercise?

Answer 35

Flow: 1200 ml/min 20% of CO vs 360ml/min 4% of CO O2 extraction: 6% vs 18% Sympathetic neural control Vasoconstriction in exercise Potential for proteinuria in intense exercise

Question 36

Why is Brain blood flow (BBF) Vital? What are functional consequences and the continuum they fall on?

Answer 36

- Survival: Supplies oxygen and substrates to the brain. - High Demand: Brain is 2-3% of body mass but uses 20% of cardiac output. - If under/over perfused it can result in Strokes - Functional Consequences: - Performance and cognitive function. - Impairments linked with diseases (e.g., dementia, stroke, TBI). - Prognostic value for cardiovascular mortality - Continuum of Impairment: - Acute: Fainting, stroke. - Chronic: Hypertension, dementia, concussion/TBI

Question 37

Physical Activity, Ageing, and Brain Health?

Answer 37

- Ageing and Inactivity: Linked to a decline in BBF. - Habitual Exercise: - Offsets age-related decline in BBF (~10-year delay). - Positive correlation between aerobic fitness and BBF.

Question 38

Measurement of Brain Blood Flow?

Answer 38

1. MRI (Magnetic Resonance Imaging): - Structure and functional imaging. - High spatial resolution but limited use during exercise. 2. Doppler Ultrasound: - Measures blood velocity as an index of flow. - Advantages: Beat-to-beat changes, robustness, and ease of use. - Commonly used with the Middle Cerebral Artery (MCA). 3. NIRS (Near-Infrared Spectroscopy): - Measures oxygen supply and demand at the capillary level. - Assesses brain activation (neurovascular coupling). - Portable and robust for exercise studies. 4. Arterial Spin Labelling (ASL):Brain perfusion imaging technique - Measures cerebral perfusion at rest. - Region-specific cerebral blood flow (CBF) analysis. 5. Phase Contrast Angiography: Brain perfusion imaging technique - Analyzes flux and velocity across cardiac cycles. - High spatial resolution but challenging to use during exercise. - Should be chosen based on what question is being asked. Multimodal Approach: - Combining different imaging methods enhances assessment of brain health. - Accounts for both structural and functional aspects.

Question 39

Key Regulators of Brain Blood Flow?

Answer 39

1. Blood Pressure - Perfusion pressure 2. Neurogenic - Cerebral SNA 3. Metabolism - links to nerve cell activity 4. Chemical - Arterial PCO2 5. Cardiac Output

Question 40

Large changes in blood pressure can occur during and following exercise... - What are the consequences for brain blood flow and brain function?

Answer 40

Fainting

Question 41

Cerebral blood flow factors and link to exercise?

Answer 41

1. Arterial Blood Pressure (ABP) 2. Cerebral Autoregulation 3. Cardiac Output 4. Baroreflex 5. Sympathetic and Parasympathetic Nervous Activity 6. Cerebral Neural Activity 7. Metabolism: - Glucose, lactate, oxygen, and carbon dioxide. 8. Nitric Oxide (NO) Exercise affects these things at the same time, complex interactions. we can use this to look at processes such as chemoreflex, baroreflex etc

Question 42

Brain blood flow responsiveness to CO2?

Answer 42

BBF highly sensitive to changes in arterial partial pressure of carbon dioxide (PaCO2). During exercise it increases till about 65% vo2 max then declines due to increase hyperventilation and reduction in H+ ions so less Co2 produced in processes

Question 43

BBF Response to Exercises, intensities and modalities?

Answer 43

- Intensity: - Incremental increase in BBF with mild to moderate exercise (20-80% Wmax). - Maximal exercise (90-100% Wmax) may lead to a plateau or decrease due to hyperventilation-induced hypocapnia. - Modality: - Different patterns observed between rowing, running, and cycling. - Rowing and Running: - BBF patterns mirror blood pressure profiles. - Cycling: - Shows modality- and fitness-specific profiles at high intensities (>65% VO2max). - Aquatic Treadmill Exercise: - BBF changes similar to land running but influenced by hydrostatic pressure. - Mechanism: Increased venous return leading to higher cerebral perfusion

Question 44

High-Intensity vs. Moderate Exercise for BBF?

Answer 44

- High-Intensity Interval Training (HIIT): - BBF decreases during 30s sprints but rebounds immediately after. - Associated with enhanced neurotrophic factor circulation. - Moderate Intensity Continuous Training (MICT): - Maintains relatively stable BBF throughout. - Different BBF profiles could indicate varied adaptations from HIIT vs. MICT.

Question 45

Practical Implications for Brain Health?

Answer 45

1. **Regular Physical Activity**: - Counteracts age-related BBF decline. - Maintains cognitive function and reduces risk of neurodegenerative diseases. 2. **Exercise Modality and Intensity**: - Influence the magnitude and pattern of BBF responses. - Tailoring exercise prescriptions can optimize brain health benefits. 3. **Potential for Targeted Interventions**: - Utilizing exercise to improve neurovascular coupling and cognitive function. - Customizing interventions based on fitness levels and health conditions