Circulatory System

Circulatory System
The heart is a cone –shaped muscular organ located within the ___(1)__ of the thorax. Its apex rests on the __(2)__ and its superior margin lies at the level of the __(3)__ rib. Approximately two-thirds of the heart mass is seen to the left of the __(4)__.
The heart is enclosed in a serosa sac called the pericardium. The loosely fitting double outer layer consists of the outermost __(5)__ pericardium, lined by the parietal layer of the serous pericardium. The inner __(6)__pericardium, also called the __(7)__, is the outermost layer of the heart wall, called the __(9)__, is composed of __(10)__; it forms the bulk of the heart.
Connective tissue fibers that ramify throughout this layer construct the so-called __ (11)__ of the heart. The membrane that lines the heart and also forms the valve flaps is the __(12)__. This layer is continuous with the __ (13)__ linings of the blood vessels that enter and leave the heart. The heart has __ (14)__ chambers. Relative to the roles of these chambers, the __(15)__ are the receiving chambers, whereas the __(16)__ are the discharging chambers.
17. Draw and label the parts of the heart internally and exteriorly.
18. A number of characteristics peculiar to skeletal or cardiac muscle are listed below. Select which ones refer to each muscle type by writing S in the answer blanks preceding descriptions that apply to skeletal muscle and C in the answer blanks of those that identify characteristics of cardiac muscle.
___19. One centrally located ___25. Contains self-excitable cells.
___20. Mre mitochondria per cell ___26. Has well-developed terminal cisternae
___21. T tubules line up at the Z lines ___27. Wide T tubules
___22. Uses fatty acids more effectively for ATP harvest ___28. More distinct myofibrils
___23. Requires stimulation by the nervous system to contract. ____29. All-or-none law applies at organ level
___24 Has a shorter refractory period. ___ 30. Intercalated discs enhance intercellular Electrical communication
The nodal cells of the heart, unlike cardiac contractile muscle fiber, have an intrinsic ability to depolarize __(31)__. This reflects their unstable __(32)__, which drifts slowly toward the threshold for firing, that is, __(33)__. These spontaneously changing membrane potentials, called __(34)__, are probably due to reduced membrane permeability to __(35)__. However, __(36)__permeability is unchanged and it continues to diffuse __(37)__ the cell at a slow rate. Ultimately, when threshold is reached, gated channels called __(38)__ open, allowing, extracellular __(39)__ to rush into the cells and reverse the membrane potential.

The events of one complete heartbeat are referred to as the cardiac cycle. Complete the following statements that describe these events by writing the missing terms in the answer blanks.
The contraction of the ventricles is referred to as __(40)__ and the period of ventricular relaxation is called __(41)__. The monosyllables describing heart sounds during the cardiac cycle are __(42)__. The first heart sound is a result of closure of the __(43)__ valves; closure of the __(44)__ valves causes the second heart sound. The heart chambers that have just been filled when you hear the first sound are the __(45)__ and the chambers that have just emptied are the __(46)__. Immediately after the second heart sound, the __(47)__ are filling with blood and the __(48)__ are empty. Abnormal heart sounds, or __(49)__, usually indicate valve problems.
Circle the term that does not belong in each of the following groupings.
50. AV valves closed AV valves open Ventricular systole Semilunar valves open
51. No P wave SA node is pacemaker AV node is pacemaker Junctional rhythm
52. Ventricles fill Ventricles systole AV valves open Late diastole
53. Early diastole Semilunar valves open Isovolumetric relaxation Ventricular pressure drops
54. Stenotic valve Restricted blood flow High-pitched heart sound Heart sound after valve opens
55. Isovolumetric ventricular systole Blood volume unchanging AV valve open Semilunar valve closed