YR 1 - HUMAN PHYSIOLOGY CHPTR 20-21

Question 1

Briefly explain heart circulation

Answer 1

The right side of the heart pumps blood through the pulmonary circulation which carries blood to the lungs where CO2 diffuses from the blood into the lungs and O2 diffuses from the lungs into the blood.

The pulmonary circulation returns the blood to the left side of the heart. The left side of the heart then pumps blood through the systemic circulation, which delivers O2 and nutrients to all the remaining tissues of the body.

From those tissues, CO2 and other waste products are carried back to the right side of the heart.

Question 2

What are the functions of the heart?

Answer 2

1. Generating blood pressure - The contractions make sure that the blood flows, this is responsible for the blood to move through the vessels
2. Routing blood - Ensuring that the blood flowing to the tissues has adequate levels of O2
3. Ensuring one-way blood flow - the valves of the heart ensure a one-way flow of blood through the heart and blood vessels
4. Regulating blood supply - the rate and force of heart contractions change to meet the metabolic needs of the tissues, such as exercise, change in body position, and rest.

Question 3

How is the heart shaped?

Answer 3

An adult heart is shaped like a blunt cone and is approx the size of a closed fist.

(heart mass)
Females average mass is 250g
Males average mass is 300g

Question 4

Where is the heart located?

Answer 4

The heart is located in the mediastinum, a midline partition of the thoracic cavity that also contains the trachea, the esophagus, the thymus, and other associated structures.

Question 5

What is the pericardium?

Answer 5

The pericardium is a double-layered, closed sac that surrounds the heart.it consists of two layers:

1. the outer fibrous pericardium - this is a tough, fibrous connective tissue layer that prevents overdistension of the heart and anchors it within the mediastinum
2. the inner serous pericardium - this is a layer of simple squamous epithelium

Question 6

What three layers of tissue are the heart wall composed of?

Answer 6

1. The epicardium - this is the superficial layer of the heart wall. It is a thin serous membrane that constitutes the smooth outer surface of the heart.
2. The myocardium - this is the thick middle layer of the heart. it is composed of cardiac muscle cells and is responsible for the heart’s ability to contract.
3. The endocardium - this is deep into the myocardium. it consists of simple squamous epithelium over a layer of connective tissue. The endocardium forms the smooth, inner surface of the heart chambers, which allows blood to move easily through the heart.
   The endocardium also covers the surfaces of the heart valves.

Question 7

What are the 4 chambers that the heart consists of?

Answer 7

The heart consists of four chambers: two atria and two ventricles.

The thin-walled atria form the superior and posterior parts of the heart, and the thick-walled ventricles form the anterior and inferior portions.

Question 8

What are the 3 major right atrium openings?

Answer 8

1. An opening from the superior vena cava
2. An opening from the inferior vena cava
3. An opening from the coronary sinus

The openings from the superior vena cava and the inferior vena cava receive blood from the body and the opening of the coronary sinus receives blood from the heart itself.

The left atrium has 4 relatively uniform openings from the 4 pulmonary veins that receive blood from the lungs.

Question 9

Describe the blood flow through the heart

Answer 9

Blood flows through both sides simultaneously. Both atria contract at about the same time and both ventricles contract at about the same time, therefore blood is moving through both the pulmonary and the systemic circulations with each heartbeat.

Question 10

Describe the structure and function of the heart skeleton

Answer 10

The heart skeleton consists of a plate of fibrous connective tissue between the atria and the ventricles.

This connective tissue plate forms fibrous rings around the atrioventricular and semilunar valves and provides solid support for them, reinforcing the valve openings.

Question 11

What are the cardiac muscle cells?

+ their electrical properties

Answer 11

Cardiac muscle cells are elongated, branching cells that have one or occasionally two centrally located nuclei.

They contain actin and myosin myofilaments organised to form sarcomeres.

Cardiac muscle cells like other electrically excitable cells, such as neurons and skeletal muscle fibers have a resting membrane potential.

The resting membrane potential depends on a low permeability of the plasma membrane to Na+ and Ca2+ and a higher permeability to K+.

Question 12

Autorhythmicity of Cardiac muscle

Answer 12

The heart is said to be autorhythmic because it stimulates itself (auto) to contract at regular intervals (rhythmic).

If the heart is removed from the body and maintained under physiological conditions with the proper nutrients and temperature it will continue to beat autorhythmically for a long time.

Question 13

What are refractory periods of cardiac muscle?

Answer 13

Cardiac muscle like the skeletal muscle has refractory periods associated with its action potential.
The refractory period can be subdivided into the absolute refractory period and the relative refractory period.
During the absolute refractory period, the cardiac muscle cell is completely insensitive to further stimulation. The cell is sensitive to the stimulation but a greater stimulation than normal is required to cause an action potential.

Question 14

Talk about Electrocardiogram

Answer 14

Action potentials conducted through the myocardium during the cardiac cycle produce electrical currents that can be measured at the body surface.

Electrodes placed on the body surface and attached to an appropriate recording device can detect small voltage changes resulting from action potentials in the cardiac muscle.

The electrodes do not detect individual action potentials: rather they detect a summation of all the action potentials transmitted by the cardiac muscle cells through the heart at a given time.

The summated record of the cardiac action potentials is an electrocardiogram.

Question 15

What does a normal ECG consist of?

Waves and complex

Answer 15

• The P wave; which is the result of action potentials that cause depolarisation of the atrial myocardium, signals the onset of atrial contraction
• The QRS complex; composed of 3 individual waves- the Q, R, and S waves results from ventricular depolarisation and signals the onset of ventricular contraction
• The T wave; represents repolarisation of the ventricles and precedes ventricular relaxation. A wave representing repolarisation of the atria cannot be seen because it occurs during the QRS complex

Question 16

Describe the cardiac cycle

Answer 16

The cardiac cycle refers to the repetitive pumping process that begins with the onset of cardiac muscle contraction and ends with the beginning of the next contraction.

The right and left halves of the heart can be viewed as two separate pumps that work together.

Each pump consists of a “primer pump” which is the atrium and a “power pump” which is the ventricle.

Atrial primer pumps complete the filling of the ventricles with blood, ventricular power pumps produce the major force that causes blood to flow through the pulmonary and systemic arteries.

Blood moves from an area of higher pressure to an area of lower pressure. Pressure changes produced within the heart chambers as a result of cardiac muscle contraction and relaxation move blood along the previously described routes of the pulmonary and systemic circulations.

Question 17

What does systole and diastole mean?

Answer 17

Systole- means to contract

Diastole- means to dilate

Question 18

Describe the heart sounds

Answer 18

The pumping heart produces different sounds and this is revealed using a stethoscope. The sounds are best heard by applying the stethoscope at particular sites in relation to the heart valves.

The lubb sound (first heart sound)- this sound is a low pitched sound. It occurs at the beginning of ventricular systole and is caused by vibration of the atrioventricular valves and surrounding fluid as the valves close.

The dupp sound(second heart sound)- this sound is a high pitched sound. it occurs at the beginning of ventricular diastole and results from the closure of the aortic and pulmonary semilunar valves.

A third heart sound can be heard in some normal people, particularly those who are thin and young.

Systole is therefore approx the time between the first and the second heart sound.

Diastole which lasts somewhat longer is approx the time between the second heart sound and the next first heart sound.

Question 19

What is the Aortic pressure curve?

Answer 19

The elastic walls of the aorta are stretched as blood is ejected into the aorta from the left ventricle. Aortic pressure remains slightly below ventricular pressure during this period of ejection.

The pressure in the ventricles begins to decrease and so does the aortas. As ventricular pressure drops below that in the aorta, blood flows back toward the ventricle because of the elastic recoil of the aorta.

When the recoil has an increase in pressure it leads to a dicrotic notch which means double beating.

Question 20

What does mean arterial pressure, cardiac output, and peripheral resistance mean?

Answer 20

Mean arterial pressure- is slightly less than the average of the systolic and diastolic pressures in the aorta. It is proportional to cardiac output x peripheral resistance.

Cardiac output- is the amount of blood pumped by the heart per minute,

Peripheral resistance- is the total resistance against which blood must be pumped.

Question 21

What is cardiac output formula?

Answer 21

Cardiac Output = Heart Rate x Stroke Volume

CO = HR X SV

Question 22

What is intrinsic regulation?

Answer 22

Tissues and organs within the body are able to intrinsically regulate, to a varying degree, their own blood supply in order to meet their metabolic and functional needs. This is termed local or intrinsic regulation of blood flow.

Question 23

What are the pulmonary vessels?

Answer 23

Pulmonary vessels transport blood from the right ventricle, through the lungs, and back to the left atrium.

Question 24

What are the systemic vessels?

Answer 24

Systemic vessels transport blood from the left ventricle through all parts of the body and back to the right atrium.

Question 25

What are the circulatory systems 5 features?

Answer 25

1. Carries blood
2. Exchanges nutrients
3. Transports substances
4. Helps regulate blood pressure
5. Directs blood flow to tissues

Question 26

What are the 3 main types of blood vessels?

Answer 26

1. Arteries
2. Capillaries
3. Veins

Question 27

What are some general features of blood vessels?

Answer 27

Except for the capillaries and the smallest veins, called venules, the blood vessel walls consist of three relatively distinct tissue layers.

These tissue layers are most evident in the muscular arteries and least evident in the veins.

From the lumen to the outer wall of the blood vessels. the layers or tunics are the tunica intima, the tunica media, and the tunica adventitia.

Question 28

What is vasoconstriction?

Answer 28

Vasoconstriction results from smooth muscle contraction and causes a decrease in blood vessel diameter, thereby decreasing blood flow through the vessel.

Question 29

What is vasodilation?

Answer 29

Vasodilation results from smooth muscle relaxation and causes an increase in blood vessel diameter, thereby increasing blood flow through the vessel.

Question 30

What do arteries do?

Answer 30

Arteries carry blood away from the heart.

Question 31

What do the ventricles do?

Answer 31

Ventricles pump blood from the heart into large, elastic arteries that branch repeatedly to form many progressively small arteries.

Question 32

What are the elastic arteries?

Answer 32

Elastic arteries have the largest diameter and are often called conducting arteries.

These vessels are the first to receive blood from the heart, blood pressure is relatively high in the elastic arteries.

Due to the pumping action of the heart, blood pressure in the elastic arteries fluctuates between higher systolic and lower diastolic values.

Question 33

Describe muscular arteries

Answer 33

Muscular arteries include medium-sized and small arteries.

The walls of some muscular arteries are relatively thick, compared with their diameter, mainly because the tunica media contains 22-40 layers of smooth muscle.

Question 34

What are arterioles?

Answer 34

Arterioles are the smallest arteries in which the three layers can be identified.

They transport blood from small arteries to capillaries.

Question 35

What are capillaries?

Answer 35

Blood flows from arterioles into capillaries, the most common type of blood vessel.

Capillary walls are the thinnest of all blood vessels.

Tunica intima is an internal lining of simple squamous endothelial cells called the endothelium.

In the vessels associated with the heart, this endothelial lining is continuous with the endocardium of the heart.

Question 36

What are the types of capillaries?

Answer 36

When comparing the many capillaries of the body, it becomes apparent that these vessels show variation in size and permeability or the degree to which materials enter or leave the blood.

Based on these characteristics, capillaries are classified as continuous, fenestrated, or sinusoidal.

Question 37

what are continuous capillaries?

Answer 37

Continuous capillaries are approximately 7-9ym in diameter, and their walls exhibit no gaps between the endothelial cells.

Continuous capillaries are less permeable to large molecules than are other capillary types; they are in muscle, nervous tissue, and many other locations.

Question 38

What are fenestrae?

Answer 38

The fenestrae are areas approximately 70-100 nm in diameter in which the cytoplasm is absent and the plasma membrane consists of a porous diaphragm that is thinner than the normal plasma membrane.

Question 39

What are sinusoidal?

Answer 39

Sinusoidal capillaries are larger in diameter than either continuous or fenestrated capillaries, and their basement membrane is less prominent or completely absent.

Their fenestrae are larger than those in fenestrated capillaries, and gaps can exist between endothelial cells.

The sinusoidal capillaries occur in places where large molecules move into the blood, such as endocrine glands.

Question 40

What are sinusoids?

Answer 40

Sinusoids are large diameter, sinusoidal capillaries. Their basement membrane is sparse and often missing, and their structure suggests that large molecules and sometimes cells can move readily across their walls between the endothelial cells.

Sinusoids are common in the liver and bone marrow.

Macrophages are closely associated with the endothelial cells of the liver sinusoids.

Question 41

What are venous sinuses?

Answer 41

Venous sinuses are similar in structure to the sinusoidal capillaries but even larger in diameter.

They are found in the spleen and there are large gaps between the endothelial cells that make up their walls.