Regulation of Heart Activity
All events occurring during cardiac activity (cardiac cycle) are regulated by:
Autonomic Regulation
The heart rate, ventricular contractility and diameter of blood vessels are regulated by the cardiovascular centre. The cardiovascular centre consists of a collection of neurones and is located in the medulla oblongata. Functionally, these neurones are classified into four groups:
The cardiovascular centre gets impulses from the cerebral cortex, limbic system (a part of the brain that is responsible for olfaction, feeding behaviour, motivation, sexual behaviour and generation of emotions) and hypothalamus. It also receives stimulations from baroreceptors (which monitor blood pressure in major arteries and veins), chemoreceptors (which monitor the chemical changes in the blood) and properioceptors. Properioceptors are receptors found in joints and muscles. They send impulses to the cardiovascular centre during physical exercises which in turn sends a response to cope with the condition.
The output from the cardiovascular centre is through the sympathetic and parasympathetic autonomic nervous system to the heart. The sympathetic innervation of the heart is from the spinal nerves via the cervical and upper thoracic (T1-T4) ganglia. The sympathetic fibres reach the SA node (node which generates the cardiac impulses, located in the right atrial wall), AV node (part of the impulse conducting system of the heart, located in the lower part of the interatrial septum) and most portions of the myocardium.
Stimulation of the sympathetic fibres results in the release of norepinephrine at their cardiac synapses, which in turn binds to beta-1 receptors in the cardiac muscle. This binding leads to certain effects. First, it increases the rate of spontaneous depolarisation on the SA and AV, accelerating the heart rate. Second, on the cardiac muscle fibres, it enhances calcium ions inflow causing an increase in the contractility and a greater ejection of blood. In maximal sympathetic stimulation, the heart rate becomes very high; the stroke volume will be low due to the very short filling time and a low preload.
The parasympathetic innervation of the heart is via the vagus nerves which innervate the SA node, AV node and atrial myocardium. The parasympathetic stimulation of the heart releases acetylcholine, which decreases the heart rate and slows the rate of spontaneous depolarisation (an inhibitory effect).
Chemical Regulation
Certain conditions such as hypoxia (low O2 level), acidosis (low pH), and alkalosis (high pH), affect the heart rate and contractility due to changes in the blood level of certain chemicals. Two major types of chemicals affect the physiology of the heart:
Other Factors
Age: the heart rate in newborn babies is higher than in children and for children is higher than in adults.
cardiac muscle
Yes
Cardiac Arrest
Positive cardiac activity means the doctor observed the baby's heart beating.
Cardiac.
Blood pressure can be regulated by counteracting fluctuations in the blood pressure by the cardiovascular system. This is done by altering the cardiac output and the peripheral resistance.
cardiacheart, the activity is co ordinated via myogenic cells, and also by the nerves going to the sino atrial node.
GLUT4 is the insulin-regulated glucose transporter found in adipose tissues and striated muscles (skeletal and cardiac) that is responsible for insulin-regulated glucose disposal."Allows equilibrium with blood-bidirectional".
Cardioplegia is the intentional and temporary cessation of cardiac activity. cardio meaning the heart and plegia meaning paralysis therefore" cardiac paralysis"
No, cardiac muscles do not work in pairs. They are arranged in a network within the heart and work together in a coordinated manner to contract and pump blood throughout the body. The contraction of cardiac muscles is regulated by electrical signals from the heart's pacemaker cells.
During cardiac arrest, asystole is a state of no electrical activity in the heart. Shocking is not effective for asystole because there is no organized electrical activity to reset. Instead, CPR and medications are used to try to restart the heart.
The cardiac cycle timing is primarily regulated by the sinoatrial (SA) node, which serves as the heart's natural pacemaker. It generates electrical impulses that initiate each heartbeat, causing the atria to contract. These impulses then travel to the atrioventricular (AV) node, which introduces a slight delay before transmitting signals to the ventricles, ensuring coordinated contractions. Additional factors, such as autonomic nervous system inputs and hormones, can influence heart rate and the timing of the cardiac cycle.