Cardiac output and regulation of cardiac function Flashcards
What is the cardiac output?
rate at which ventricle pump blood
What is cardiac output formula ?
Heart rate * stroke volume
What is extrinsic control?
regulation of heart by neural input, hormones
What is intrinsic control ?
within heart
How is neural control of cardiac output done?
by PNS
what 2 branches does PNS have?
Autonomic and Somatic
What is autonomic branches made of ?
Sympathetic
Parasympathetic
What is Afferent branch?
sensory signals via PNS Into CNS
What is Efferent branch?
Motor responses delivered to PNS FROM CNS
What does Somatic branch do?
control skeletal muscles
What is neural input from thoracic and lumbar regions?
Thoracolumbar
What is Parasympathetic innervation on heart?
Vagus nerve to SA/AV nodes so Reduce heart rate via Acetylcholine
What is Sympathetic innervation on heart?
Sympathetic nerves to AV/SA nodes and ventricles and Noradrenaline increase heart rate
What does acetylcholine act on?
from post ganglionic neurones on pace maker cells
Where is Adrenaline released from ?
adrenal medulla via blood stream
What increases heart contractions?
thyroid hormones, Glucagon & insulin
What does glucagon promote?
Increased Heart rate
What factors affect Stroke Volume?
1) Ventricular contractility
2) End diastolic volume
3) Afterload
What increases ventricular contractility?
- increased Sympa. activity so cardiac output increases
- increased Ca2+ and permeability
- adrenaline
What is End diastolic volume an example of ?
Starlings law
What is starlings law?
rate at which blood flows into heart from veins changes, the heart adjusts its output to match the inflow
What does increased EDV mean?
increased ventricular contractility so incr. SV and Cardiac output
What happens when increased EDV?
Myocytes in Vent/ myocardium stretch and lengthen
What does myocytes stretching mean?
greater affinity of troponin for Ca so greater force of contraction
What factors affect EDV?
End diastolic pressure = PRELOAD
What is Preload?
how much volume in ventricle at end of diastole
What is preload determined by?
filling time
atrial pressure
What is Afterload?
heart works against arterial pressure to pump blood
What does increased arterial pressure mean?
Stroke Volume Decreases
