Glossary

Absolute Refractory Period– The period in which another action potential cannot be generated even if another stimulus is applied.

Adrenal Glands– hormone-producing glands that are located on the top of the kidney. They secrete epinephrine, aldosterone, and cortisol.

Afterload– The opposing pressure inside the aorta that keeps the aortic valve closed and works against the ejection of blood volume from the left ventricle.

Anatomical Position– A standard orientation, with the body upright and hands by sides.

Arteries– Vessel that carry oxygen-rich blood away from the heart.

Arterioles– Smaller vessel that branches off of arteries. moving blood to capillary beds.

Atrial and Ventricular Myocytes– a myocyte is a muscle cell, different types of myocytes can be found all around the body and even within the heart.

Atrial Reflex– Increased heart rate due to increased blood volume (stretch of the atria).

Atrium– The upper chambers of the heart which direct blood towards the ventricles.

Automaticity– the ability to spontaneously depolarize.

AV Node–  A cluster of spontaneously depolarizing nodal cells that are adjacent to the pulmonary artery. They transmit electrical signal from the SA node to the bundle of His.

Baroreceptors– Sensory receptor cell sensitive to changes in pressure (detected through stretch).

Cardiac Cycle– everything that takes place between one heart beat and the next.

Cardiac Output– The amount of blood pumped through the circulatory system in 1 minute. (L/min).

Chemoreceptors– Sensory receptor cell sensitive to changes in physiological chemical properties ie. pH.

Collagen– A protein which provides structural support to connective tissues, muscles and skin.

Conduction– Function of the electrical system of the heart.

Contractility– The ability of the heart muscles, otherwise known as cardiac myocytes to exert force by contracting.

Contraction– Outcome of the electrical system of the heart, ie. conduction causes contraction.

Depolarization– Charge within the cell becomes more positive (upward slope of the curve).

Diastole– The relaxation phase of the heart (no contraction).

Diffusion– Net movement from high concentration to low concentration.

Edema– swelling caused by tissue leakage.

End-diastolic volume (EDV) / Preload– The volume of blood in the ventricles following passive diastolic filling (high volume).

End-systolic volume (ESV)– The volume of blood in the ventricles that is “left over” following contraction (low volume).

Extrinsic Control– Regulation by factors originating outside the tissue.

Filling Time-How long the heart is in diastole. If the filling time is too quick there will be no blood to pump out, if it is too long blood will start to pool in the filling chamber.

Functional Compartmentalization– The breakdown of a system into a smaller more detailed sections or “compartments” that all work together to produce one main outcome or “function.”

G-proteins– Membrane protein required for neurotransmitter signalling by metabotropic receptors. Involved in regulation of ion channels and effector enzyme synthesis or breakdown.

Heart Rate– The number of cardiac cycles that are completed per unit time (in beats/minute).

Homeostasis- A state of relatively stable equilibrium in the body that is maintained by constant adjustment of biochemical and physiological pathways.

Hyperkalemia- Dangerously high potassium levels in the body.

Hyperpolarization– The change in a cell’s membrane potential that makes it more negative than the resting membrane potential

Hypoxia– Experiencing too little oxygen for proper function.

Interstitial Fluid– Extracellular fluid found throughout the whole body.

Intrinsic control– Regulation by a factor originating from within the tissue.

Iso-Volumetric– No change in volume despite large increase/decrease in pressure. We this phenomenon as pressure builds in the ventricles in preparation for systolic contraction.

Mean Arterial Pressure– The average arterial pressure during one cardiac cycle.

Nodal Cells– Heart cells found within the sinoatrial node. Considered the primary pacemaker of the heart because they do not have a resting membrane potential and have the ability to spontaneously depolarize.

Oncotic Pressure– the osmotic force generated by the presence of proteins in the blood that draws fluid from the intertitium into the vasculature.

Osmosis– the movement of water (or another solvent) from an area of higher water concentration to an area of lower water concentration (through a semi-perimeable membrane).

Pacemaker Cells– Control heart rate and blood flow by influencing rhythmic electrical impulses.

Pacemaker Rate– The speed that a pacemaker cell causes the heart to beat (beats/min).

Relative Refractory Period– The period during which a stimulus must be supermaximal to generate another action potential.

Re-polarization– A restoration of the membrane potential of a cell after the depolarization phase.

SA Node– A cluster of spontaneously depolarizing nodal cells that are located in the right atrium. They conduct action potentials at the fastest speed and therefore set resting heart rate.

Stroke Volume– Volume ejected from the heart each cardiac cycle. (mL).

Systole– The pumping or contraction phase of the heart.

Total Peripheral Resistance– The sum of vascular resistance in each vessel in the circulatory system.

Vasculature- The arrangement of blood vessels within an organ or body part.

Vasoconstriction– Contraction of smooth muscle cells and the tightening of blood vessels. This will allow for less blood flow through the vasculature.

Vasodilation– Relaxation of smooth muscle ells and the widening of blood vessels. This will allow for more blood flow through the vasculature.

Veins– Vessel that brings oxygen depleted blood back to the heart.

Venous Return– Blood flow back to the heart within a cardiac cycle. If VR does not = CO it could be evidence of blood pooling or blockage somewhere.

Ventricles– Larger lower compartments of the heart which pump blood out of the arteries.

Venules– Small blood vessel that allows blood to flow from capillary beds to veins.

resistance arterioles

venous pressure