Heartbeat Flashcards
MYOGENIC:
Heart generates its own beat
Contraction is called:
Systole
Relaxation is called…
Diastole
The atria and ventricles contract at different times during a single beat -
Cardiac cycle
Order of contraction is:
Diastole
Atrial systole
Ventricular systole
Diastole is:
Heart chambers relax, allowing atria to fill with blood
Atrial systole is…
Atria contract forcing blood into ventricles
Ventricular systole…
Ventricles contract forcing blood out of the heart to lungs or body
SAN sends an electrical impulse through atria - first - systole, then…
Down septum
then from top of ventricular systole
Heart rate changes via 2 nervous systems:
Parasympathetic (vagus nerve)
Sympathetic
SAN sets heart rate at about…
120bpm (too high, when at rest 60-80bpm)
Nerves act as…
Brakes and accelerators.
Cause of change in heart rate:
Exercise - more CO2 in blood
Increased acidity - decrease in pH
Increase in CO2 is detected by…
Chemoreceptors (found in blood vessels)
Impulses sent to medulla oblongata (situated in cardiac control centre)
Changes to HR via para- and sympathetic nerves
Regulation of HR (exercise)
Blood CO2 levels rise (detected by chemoreceptors)
Impulse to medulla
Decreased parasympathetic impulses to SAN lets heart beat faster
Increased sympathetic - heart beats even faster
Regulation of HR after exercise:
Blood pressure rise detected by baroreceptors
Sent to medulla
Increased parasympathetic - let’s heart beat slower
Decreased sympathetic - allows HR to slow
Mechanoreceptors:
Receptors in muscle fibres tell if heart is contracting or relaxing
Controlled by 2 mechanisms:
Neural control
Hormonal control
Neural control -CCC
Receives information from…
Sensory receptors - mechanoreceptors
Chemoreceptors
Baroreceptors (blood pressure)
- sense for stretch
- heart and blood vessels
- increase in blood flow/pressure
Hormonal control:
Adrenalin - the anticipatory rise cause adrenaline to be released from adrenal glands into the blood stream
Adrenalin prepares body by:
Increasing hr
Strength of ventricular systole
Increases blood glucose levels by stimulating breakdown of glycogen in the liver
Adrenalin forms part of the:
Sympathetic nervous system
Acetylcholine released by…
Parasympathetic nerves
Causes a decrease in heart rate
Chemoreceptors detect acidity causes by CO2 and lactic acid during exercise
Sends message to medulla oblongata
Sends a signal via the sympathetic (accelerating nerve)
Stimulates the…
SAN in the right atrium to contract the heart more forcefully and quickly
Therefore pumping more blood
Chemoreceptors detect acidity causes by CO2 and lactic acid during exercise
Sends message to medulla oblongata
Sends a signal via the parasympathetic (decelerating nerve)
Reduces stimulation of the…
SAN in the right atrium to contract the heart less forcefully therefore reducing amount of blood being pumped
Happens gradually
