Thorax Overview Flashcards
Elements of Circulatory Control
- Ability to sense changes in blood pressure
- Ability to sense changes in cardiac output
- Ability to relay above information to the brain
- Ability to activate effector mechanisms to adjust pressure and CO
Systemic vascular resistance
The total resistance to flow of the circulatory system
Baroreceptors
Nerve endings embedded in the walls of the carotid artery and the aorta. These locations allow the receptors to sense the mural stretch associated with blood pressure.
Information from baroreceptors is relayed to ___.
Information from baroreceptors is relayed to the medulla.
The medulla responds to sensory input from baroreceptors via. . .
. . . activation of sympathetic and parasympathetic nervous systems.
If baroreceptors detect increasted mural stretching. . .
. . . they send a signal to the medulla saying that blood pressure is too high, and the medulla activates the parasympathetic nervous system to reduce pressure.
If baroreceptors detect reduced mural stretching, . . .
. . . . . . they send a signal to the medulla saying that blood pressure is too low, and the medulla activates the sympathetic nervous system to raise pressure.
The Controller diagram
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chemoreceptors and their interaction with baroreceptors
Chemoreceptors that detect blood oxygen, CO2, and pH sit next to the baroreceptors in the aorta and carotid and regulate the respiratory system in a similar manner.
____ has been shown to lead to a sustainable increase in blood pressure.
Psychological stress has been shown to lead to a sustainable increase in blood pressure.
The cardiac conduction system is made up of. . .
. . . specialized cardiomyocytes. That’s right, they are NOT nerves, but they are connected similarly.
Rough cardiac conduction system diagram
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Special characteristics of conduction system cardiomyocytes
- Connected by gap junctions (moreso than most cardiomyocytes)
- Have a larger diameter than most cardiomyocytes, a feature that facilitates rapid conduction
When cardiac myocytes within each chamber contract, they do so. . .
. . . concurrently, but first the atria and then the ventricles.
“Great vessels”
Just those that directly supply and drain the heart
When thinking of the heart as a functional unit, you should include. . .
. . . the heart itself, the pericardial sac, the great vessels, and the thoracic cavity (which may control pressure and orientation)
Changes in pleural pressure
As the chest moves, pleural pressure differentials are created and transmitted to the great vessels and to the heart itself.
Situation of heart and great vessels (diagram)
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Murmurs are the sound resulting from ___.
Murmurs are the sound resulting from turbulent bloodflow.
Superior and inferior vena cava drainage
The SVC drains the head and arms
The IVC drains. . . everywhere else
Fibrous pericardium
Attaches to the diaphragm and sternum and helps the heart stay in its anatomical position. Attached directly to the parietal pericardium.
Changes in thoracic pressure affect. . .
. . . heart and lung function
During inhalation, pleural pressure. . .
. . . drops below atmospheric pressure. This increases venous return to the right heart, and a set of baroreceptors also transiently increases heart rate.
During exhalation, pleural pressure. . .
. . .rises above atmospheric pressure. This restores heart rate to normal by deactivating baroreceptors.
Sinus arrhythmia
Describes the changes in heart rate associated with respiration due to changes in thoracic pressure. Heart rate increases when breathing in and decreases when breating out. This may be observed by monitoring a pulse of yourself while taking an exaggerated breath in.
Heart top view diagram
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Heart conduction system diagram
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Heart coronary artery diagram
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Myocardiocyte diagram
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Myocardiocyte tubular systems diagram
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Aortic arch and trachea
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Area surrounding the mediastinum
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Trachea cross section
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Bronchi and bronchioles
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Hylar/Mediastinal lymph nodes
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Inspiration requires a ___ pressure in the alveolus, while expiration requires a ___ pressure in the alveolus.
Inspiration requires a negative pressure in the alveolus, while expiration requires a positive pressure in the alveolus.
Role of muscles of inspiration vs muscles of expiration
Muscles of inspiration must be utilized to breathe in.
In contrast, expiration is usually a passive process resulting from the relaxation of these muscles. Rather, our expiratory muscles are utilized only actively or passively when airway resistance is high.
Muscles of inspiration and associated nerves
- Diaphragm (C3 to C5)
- External intercostals (T1 to T12)
Accessory muscles of inspiration and associated nerves
- Scalenus (C4, C5, C6)
- Sternocleidomastoid (C2, C3)
- Sometimes pectoralis major (only when the arms are in a fixed position) (dual motor innervation: C7, C8, T1 at sternal head and C5, C6 at clavicular head)
Why do people who are having trouble breathing assume the “tripod” position?
Because in this position the arms are fixed and thus the pectoralis major may be used as an accessory breathing muscle
The energy that is utilized to passively exhale comes from . . .
. . . the energy stored in the gas-filled lungs due to the work by the inspiratory muscles.
Ventilation
The volume of air going in and out of the lungs each minute
Tidal volume
The size of the breath
How the body tunes ventilation
- For small changes in ventilation, changes in tidal volume suffice
- For larger changes, a change in the rate of gas flow is necessary, and this necessarily entails having muscles work on the system, since baseline exhalation is a passive process for the body. This is where the accessory expiration muscles come in: to supply that energy.
C fibers
Positioned in airways and pulmonary capillaries. Play a role in sensing fluid buildup in the lungs and adjusting behavior. This information is conveyed to the brain via the vagus nerve.
Bronchi vs bronchioles
Bronchi contain cartilage, glands, and the goblet cells and ciliated epithelia that make up the mucocilliary escalator.
Once you reach the bronchioles, these additional features are no longer present.
The sum of the cross-sectional area of the two new airways at each branch point is. . .
. . . greater than that of the parent branch.
Conducting airways
Airways through which no gas exchange takes place
Transitional zone
Separates the conducting airways from the alveoli or respiratory zone, where gas exchange takes place.
This zone consists of the respiratory bronchioles
“Dead space”
Regions of lung that receive air but do not participate in gas exchange.
The central problem of the respiratory system
The tradeoff between dead space and airflow resistance
Since the cross-sectional area of the airways increases as air progresses into the lung, . . .
. . . the velocity of the air greatly decreases by the time it reaches the bronchioles. This is also probably why dust and debris tends to settle in the alveoli and far bronchioles.
Emphysema pathology
Destroys the connective tissue support for bronchioles, making them more susceptible to collapse.
Compliance
Measure of the stiffness of an object and is equal to the change in volume that occurs in an object due to a given change in pressure applied across the object’s wall.
Compliance = ΔV / ΔP
Pores of Kohn
Pores that connect the alveoli within a lobe of the lung. Function to minimize collapse of lung units if a more central airway is obstructed
Pores of Kohn diagram
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