Human Anatomy and Physiology : Help with Inspiration and Expiration Physiology

Study concepts, example questions & explanations for Human Anatomy and Physiology

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Example Questions

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Example Question #1 : Help With Inspiration And Expiration Physiology

Which of the following muscles does NOT assist in forced inhalation?

Possible Answers:

External intercostals

Diaphragm

Sternocleidomastoid

Rectus abdominis

Correct answer:

Rectus abdominis

Explanation:

Normal inspiration typically involves the flattening (contraction) of the diaphragm in order to increase the volume of the thoracic cavity, and can be done unconsciously. In order to increase the amount of inhaled air, other muscles such as the external intercostals and the sternocleidomastoids are included by conscious control. Both of these muscles aim to raise and expand the thoracic cavity in order to assist in inhalation.

The rectus abdominis is involved in the opposite action of forced exhalation. The rectus abdominis aims to decrease the volume of the thoracic cavity by contracting. This assists in forced exhalation.

Example Question #2 : Help With Inspiration And Expiration Physiology

Which section of the brain controls unconscious breathing?

Possible Answers:

The hypothalamus

The cerebral cortex

The thalamus

The pons

Correct answer:

The pons

Explanation:

Unconscious breathing is controlled by the pons and the medulla oblongata, both of which are parts of the brain stem. This unconscious breathing can be consciously controlled by using the cerebral cortex, which manages most voluntary actions.

It helps to remember that the brain stem is responsible for unconscious control of the body: breathing, heart rate, blood pressure, etc. It is the addition of the cerebral cortex that allows humans to have conscious control over actions, such as breathing, and override the unconscious controls. For example, the cerebral cortex is used to consciously stop breathing when diving underwater.

Example Question #3 : Help With Inspiration And Expiration Physiology

What happens during inspiration?

Possible Answers:

The diaphragm curves superiorly, the external intercostals contract, and there is a negative pressure in the thoracic cavity

None of these answers are correct

The diaphragm contracts, the external intercostal muscles contract, and there is a negative intrapleural pressure

The diaphragm relaxes, the internal intercostal muscles contract, and there is a positive intrapleural pressure

The abdominal muscles contract, creating a negative pressure in the thoracic cavity

Correct answer:

The diaphragm contracts, the external intercostal muscles contract, and there is a negative intrapleural pressure

Explanation:

At rest the diaphragm is slightly curved superiorly such that it makes this sort of shape:      When it contracts, it flattens out, with the middle of the muscle being pulled down until the muscle is roughly horizontal. Remembering that the diaphragm separates the thoracic and abdominal cavities, if it contracts, it physically increases the volume of the thoracic cavity. Now, remembering your fluid physics, an increase in volume is accompanied with a decrease in pressure. We know that high pressure flows to low pressure spontaneously. The atmospheric pressure is now higher than the intrapleural (or thoracic cavity) pressure, causing air to flow into the lungs.

Note that the external intercostals aid in inspiration and the internal intercostals aid in expiration.

Example Question #4 : Help With Inspiration And Expiration Physiology

Which of the following describes tidal volume?

Possible Answers:

The volume of air inspired or expired during normal breathing

The volume of air still in the lungs after a maximal expiration

The maximum volume of air that can be expired after a maximal inspiration

The maximum volume of air that can be inspired after a normal expiration

The maximum volume of air that can be inspired after a normal inspiration

Correct answer:

The volume of air inspired or expired during normal breathing

Explanation:

Tidal volume is, by definition, the amount of air inspired/expired during normal breathing. The maximum volume of air that can be inspired after a normal expiration is the inspiratory capacity. The maximum volume of air that can be expired after a maximal inspiration is the vital capacity. The volume of air still in the lungs after a maximal expiration is the residual volume. The maximum volume of air that can be inspired after a normal inspiration is the inspiratory reserve volume.

Example Question #5 : Help With Inspiration And Expiration Physiology

When the diaphragm contracts (is pulled downward), __________ occurs. 

Possible Answers:

exhalation

a hiccup

inhalation

a pneumothorax

Correct answer:

inhalation

Explanation:

During a respiratory cycle, the diaphragm contracts and moves downward. When this occurs the pressure in the alveoli falls. This pulls air into the lungs. At the same time external intercostals muscles contract, raising ribs and sternum and enlarges the cavity even more. During exhalation the diaphragm relaxes (moves up) and air is foced out of the body. A hiccup is a muscular spasm of the respiratory muscles including the diaphragm. A pneumothorax is a "hole" in the lungs that causes air to accumulate in the pleural space.

Example Question #6 : Help With Inspiration And Expiration Physiology

While breathing, the diaphragm alternately contracts and relaxes to change the pressure of the lungs. Which of the following is correct during expiration?

Possible Answers:

Zero pressure in the lungs

Atmospheric pressure in the lungs

Decreased pressure in the lungs

Increased pressure in the lungs

Pressure does not affect how humans breathe

Correct answer:

Increased pressure in the lungs

Explanation:

When exhaling, the lungs elasticity compresses the walls increasing the pressure within so that it exceeds atmospheric pressure and forces air out. Humans, despite how it might feel, do not suck in air. Rather pressure differences allow air to rush in and out. During expiration, the diaphragm relaxes, bowing up into the thoracic cavity, thereby decreasing the volume of the thoracic cavity. This results in a corresponding increase in pressure (Boyle's law), and thus the movement of air from the lungs out of the body through the upper respiratory structures.

Example Question #7 : Help With Inspiration And Expiration Physiology

Which of the following best describes the physiological mechanism used by the human body during a normal inspiratory phase of breathing?

Possible Answers:

Positive-pressure

Idiopathic pulmonary fibrosis

Frank-Starling mechanism

Glomerular filtration

Negative-pressure

Correct answer:

Negative-pressure

Explanation:

During the normal inspiratory phase of breathing, in other words, when a human is "breathing in," the physiological mechanism used is called "negative-pressure" breathing. Negative-pressure refers to the pressure in the chest cavity as compared to the surrounding environment. The body generates negative-pressure in the chest cavity during breathing by the contraction of the diaphragm muscle (it pulls downward, expanding the thoracic cavity size and space for the lungs to fill), and the outward expansion of the ribcage (which also expands the thoracic cavity size and provides more space for the lungs to fill). With the increased volume of the thoracic cavity generated, this creates the negative pressure that is needed to draw air into the lungs down its gradient of higher pressure (outside the body/thorax) to lower pressure (into the lungs/thorax). Positive-pressure is an incorrect choice because it is the opposite of what occurs during normal human inspiration.

Positive-pressure is sometimes artificially used in the medical setting with machines in patients with obstructive sleep apnea, or in patients who cannot breathe on their own, but is not a part of standard physiological respiration. The Frank-Starling mechanism describes the mechanism by which the heart pumps blood, but does not describe respiration. Glomerular filtration describes the mechanism by which the glomeruli of the kidneys initially filter blood, but does not describe respiration. Idiopathic pulmonary fibrosis is a disease of the interstitium of lung tissue, but does not describe the physiological mechanism used during inspiration.

Example Question #8 : Help With Inspiration And Expiration Physiology

Which nerve is responsible for innervating the diaphragm during respiration?

Possible Answers:

Vagus nerve

Phrenic nerve

Musculocutaneous nerve

Sympathetic trunk

Hypogastric nerve

Correct answer:

Phrenic nerve

Explanation:

The phrenic nerve is the nerve responsible for innervation of the diaphragm. The term phrenic is often associated with descriptions of the diaphragm (i.e cardiophrenic ligament is a ligament associated with connecting the diaphragm to the pericardium of the heart)

Example Question #9 : Help With Inspiration And Expiration Physiology

You are a physician taking care of a patient with Chronic Obstructive Pulmonary Disease (COPD), a disease that results in difficulty expiring air from the lungs, but generally does not affect the ability to inspire air. You measure the amount of  that the patient expires in a single breath. What do you expect the  readings to be during this expired breath?

Possible Answers:

None of the other answers are correct.

The patient's expired  content will be higher than that of a healthy person.

The patient's expired  content depends on their gender.

The patient's expired  content will be lower than that of a healthy person.

The patient's expired  content will be the same as that of a healthy person.

Correct answer:

The patient's expired  content will be higher than that of a healthy person.

Explanation:

In this patient with Chronic Obstructive Pulmonary Disease (COPD), which is a disease that results in difficulty expiring air (and generally does not affect one's ability to inspire air), we would expect to see an increased level of  in the air that he/she expires, as compared to someone without COPD. Although this is a medically-oriented question, this does not require you to know anything about COPD that is not already supplied in the question. By stating that the ability to expire air is impacted but that the ability to inspire is generally not affected, this calls upon your knowledge of pulmonary physiology, telling you that if inspiration is not affected,  levels are probably not significantly affected, and that if expiration is affected,  levels are probably affected. 

Once you identify that  levels are affected in COPD, the question now is, how exactly are they affected? In a COPD patient, it is stated in the question stem, that they have a decreased ability to expire air. When a healthy person expires air, they remove  from the body. In a COPD patient, who therefore has a decreased ability to remove  from the lungs, if we measured the amount of a  in a single breath, we would expect it to be elevated as compared to a healthy individual. At first glance, this may seem counter-intuitive, since we are stating that COPD patients have trouble removing  from the body. However, the air that they expire is the same air that is coming from their lungs, which contains the elevated levels of . Thus, to answer the question, we expect the  reading for the expired breath to be elevated as compared to that of a healthy person. 

Example Question #10 : Help With Inspiration And Expiration Physiology

The contraction of the abdominal muscles taking place is important in __________.

Possible Answers:

none of the answer choices

forced (maximum) inspiration

normal (quiet) inspiration

normal (quiet) expiration

forced (maximum) expiration

Correct answer:

forced (maximum) expiration

Explanation:

During forced maximum expiration, the lungs are trying their best to push air out of the lungs with the most force. This cannot be accomplished by the lungs alone, so the additional contraction of the abdominal muscles aid to help push air out of the lungs with maximum force.

This is different from normal (quiet) expiration, where only the elastic recoil of the lungs are needed with no additional muscle contractions. Normal expiration does not require pushing air out of the lungs with force.

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