Response to exercise

• What type of muscle contracts spontaneously without external stimulation?

  Myogenic
• Cardiac muscle is myogenic.
• The heart starts to contract rhythmically in the 6th week of embryonic development.
• What electrical signals maintain the rhythm of the heart?

  Electrical impulses
• Specialized cells in the heart that generate electrical signals are called pacemaker cells.
• Where are pacemaker cells located in the heart?

  SAN
• What is cardiac output measured in?

  dm³min⁻¹
• Cardiac output (CO) is calculated as Stroke Volume (V) × Heart Rate R.
• The cardiac output of a typical adult at rest is between 4 and 6 dm³min⁻¹.
• What is the cardiac output during hard exercise approximately?

  30 dm³min⁻¹
• The cardiac output is controlled by the autonomic nervous system.
• Which part of the brain coordinates nervous responses to changes in blood demand?

  Cardiovascular control centre
• The anticipation of exercise leads to the release of adrenaline.
• Where are baroreceptors located in the body?

  Carotid arteries
• When blood pressure falls, the stretch on baroreceptors reduces.
• Steps in the response to falling blood pressure

  1️⃣ Baroreceptors detect reduced stretch

  2️⃣ Cardiovascular control centre sends signals via the sympathetic nerve

  3️⃣ Noradrenaline is released at the SAN

  4️⃣ Heart rate increases
• What type of neurotransmitter is noradrenaline?

  Excitatory
• Stimulation from the sympathetic nerve increases stroke volume.
• What chemical change in blood during exercise is detected by chemoreceptors?

  Increased carbon dioxide
• When exercise stops, the cardiovascular control centre sends signals via the parasympathetic nerve.
• What neurotransmitter is released by the parasympathetic nerve at the SAN?

  Acetylcholine
• The parasympathetic stimulation reduces heart rate after exercise.