Week 4

Question 1

Structure & Function of the Autonomic Nervous System (ANS)?

Answer 1

• Two branches:
  
  1. Sympathetic Nervous System (SNS)– “Fight or flight”
  2. Parasympathetic Nervous System (PNS)– “Rest and digest”
• Controls involuntary functions such as heart rate, blood pressure, digestion.
• Regulates cardiovascular variables including:
  
  • Heart rate (HR)
  • Stroke volume (SV)
  • Cardiac output (Q)
  • Arterial blood pressure (BP)
• Neurotransmitters of ANS
  
  • SNS:Releasesnorepinephrine(NE) → Increases HR & contractility
  • PNS:Releasesacetylcholine(ACh) → Decreases HR
  • ACh = Cholinergic, NE = adrenergic

Question 2

Nervous System Regulation of Heart Rate?

Answer 2

• Low resting heart rate (HR) is due to parasympathetic tone.
• HR increases at the onset of exercise:
  
  1. Initial increase→ Due to withdrawal of PNS activity (~up to 100 bpm).
  2. Later increase→ Due to increased SNS activation.

Question 3

Factors Affecting SV?

Answer 3

1. End-Diastolic Volume (EDV) “Preload”
   
   • More blood in ventricles = stronger contraction.
   • Governed byFrank-Starling Mechanism(greater stretch = stronger contraction).
   • Depends on venous return.
2. Average Aortic Blood Pressure “Afterload”
   
   • Pressure the heart must overcome to eject blood.
   • Higher afterload = Lower SV.
   • Mean arterial pressure (MAP) contributes.
3. Strength of Ventricular Contraction (Contractility)
   
   • Increased by:
     
     • SNS stimulation (epinephrine & norepinephrine).
     • Direct sympathetic activation of the heart.

Question 4

Factors Affecting Venous Return (Key for SV)?

Answer 4

1. Venoconstriction (SNS-driven)
2. Skeletal muscle pump(muscle contractions push blood back to the heart).
3. Respiratory pump(breathing mechanics assist venous return).

Question 5

Cardiac Output (Q)?

Answer 5

Definition:Amount of blood pumped per minute.

Equation:

Q=HR×SV

Q=HR×SV

• Cardiac Output Regulation:
  
  • Increased byhigher HR & SV.
  • Higher in trained athletes.
  • Directly related toVO2max(~6:1 ratio between Qmax and VO2max).
• Factors that regulate Q:
  
  • Preload = EDV, Afterlod = Mean arterial pressure, contraction strength, links to frank starling law.

Question 6

Arterial Blood Pressure (BP)?

Answer 6

• Systolic BP (SBP):Pressure during ventricular contraction.
• Diastolic BP (DBP):Pressure during relaxation.
• Pulse pressure: Difference between systolic and diastolic
• Mean Arterial Pressure (MAP):MAP=DBP+0.33(SBP−DBP)MAP=DBP+0.33(SBP−DBP)

Question 7

Factors Influencing BP?

Answer 7

1. Cardiac output (Q)
2. Total vascular resistance (TVR)MAP=Q×TVRMAP=Q×TVR

Question 8

Mean Arterial Pressure equation?

Answer 8

Cardiac output x Total vascular resistance

Question 9

Regulation of BP?

Answer 9

• Short-term:
  
  • Controlled bybaroreceptorsin aorta & carotid arteries.
  • ↑ BP→↓ SNS activity
  • ↓ BP→↑ SNS activity
• Long-term:
  
  • Kidneysregulate blood volume.

Question 10

Cardiovascular Responses to Exercise?

Answer 10

• Increased metabolic demand → Adjustments in Q & blood flow.
• Mechanisms:
  
  1. Increased cardiac output (Q)
  2. Redistribution of blood flow to active muscles

Question 11

Exercise & Stroke Volume (SV)?

Answer 11

• In most individuals,SV plateausat40-60% of VO2max.
• Elite runners:SVmay not plateau→ Likely due tohigher venous return & EDV.
• Body position matters!
  
  • Supine exercise =Higher SVdue to improved venous return.
  • Upright exercise =Lower SVdue to gravity reducing venous return.

Question 12

What are Circulatory Responses to Different Exercise Types influenced by?

Answer 12

• Type, intensity, and durationof exercise.
• Environmental conditions(hot/humid vs. cool).
• Emotional influence(SNS activity increases HR before exercise)

Question 13

Different to Responses to Different Exercise Types? HR, SV, Q, BP

Answer 13

Rest > Exercise: Rapid ^ x 3, Slight ^

Recovery: Gradual decrease x 4

Incremental: linear ^ HR, Q, SV plateau at 50-60% Vo2 max, SBP ^, DBP constant

Intermittent: HR and Q flux, SV recovers between bouts, Bp affected by temp

Prolonged: HR drifts, SV gradual decrease, Q maintained, BP risk of CV drift

Question 14

Recovery Dynamics After Exercise