Heart Control Flashcards
Cardiac output
Volume of blood pumped by one ventricle of the heart in one minute (dm3min-1)
Cardiac output depends upon
1) heart rate (bpm)
2) stroke volume
Cardiac output
Heart rate x stroke volume
Increasing cardiac outputs
Strong heart muscles with a higher stroke volume
Pulse
- wave of pressure that pass along the arteries
- causes them to expand & recoil rhythmically
- not always same as heart rate, if heartbeat becomes irregular
Myogenic contractions
When cardiac muscles are provided with O2, nutrients and mineral salts, they contract spontaneously (without nervous or hormonal stimulation)
Sinoatrial node
Small patch of tissue which has its own inherent rhythm of contraction
Cardiac impulses
Electrical impulses generated by the SA
Chemoreceptors
- sensory receptors that detect changes in the concentration of chemicals in the blood (pH)
- found in the carotid and aortic sinuses and arteries
- act as transducers, transferring chemical energy into electrical energy; can be conducted as an action potential along a neurone
Stretch receptors
- detect movement of the limbs
- located in the muscles
- transduce kinetic energy to electrical energy
- informs brain that more O2 may soon be needed
Baroreceptors
- a type of stretch receptor
- detect changes in blood pressure that affect stretch of artery walls
- found in the walls of the carotid sinus
Medulla oblongata
Contains the cardiorespiratory (cardiovascular) centre
Autonomic nervous system
• responsible for controlling involuntary motor activities
• two divisions
i) sympathetic
ii) parasympathetic
Sympathetic system
- excitatory
- accelerans nerve
- most active at times of stress
- uses noradrenaline
- increases heart rate
- dilates pupils
- increases ventilation rate
- reduces digestive activity
Parasympathetic system
- inhibitory
- vagus nerve
- most active during sleep or relaxation
- uses acetylcholine
- opposite effects