respiratory

Question 1

mediastinum

Answer 1

The mediastinum is a central compartment within the thoracic cavity, situated between the left and right pleural cavities (which house the lungs). It acts as a divider and a container for various vital organs of the chest (heart, trachea, vessels and more).

Question 2

define lungs.
what lung is bigger? (number of lobes of R/L lung)

Answer 2

The lungs are a pair of spongy, air-filled organs that reside within the chest cavity, also known as the thoracic cavity. They are the centerpiece of the respiratory system, responsible for the vital process of gas exchange.

• right lung → 3 lobes - upper, middle, and lower.
• left lung → 2 lobes - upper and lower ( smaller than right )

Question 3

what’s the diaphragm? what does it do while breathing?

Answer 3

The diaphragm is a dome-shaped sheet of skeletal muscle that plays a critical role in breathing. It separates the chest cavity (thorax) from the abdominal cavity (abdomen).

During inhalation the diaphragm contracts and flattens downward. This increases the volume of the chest cavity, creating a lower pressure inside the lungs compared to the atmospheric pressure outside. Air rushes into the lungs to equalize the pressure differential.
(The diaphragm works in conjunction with the intercostal muscles between the ribs)

During exhalation (breathe out), the diaphragm relaxes and returns to its dome-shaped position.
The elastic recoil of the lungs and the downward movement of the rib cage due to relaxed intercostal muscles naturally push air out of the lungs.
The diaphragm doesn’t actively contract during exhalation in healthy individuals. However, forceful exhalation, such as coughing or singing, might involve some diaphragm activity.

Question 4

define hilum of the lungs.

Answer 4

A part in each lung where the bronchus (airway), blood vessels, and nerves enter and leave the lung tissue.

Question 5

what does the upper respiratory tract include?
what does the lower respiratory tract include?

Answer 5

upper- nasal cavity, Pharynx (throat) and larynx
lower - Trachea, Bronchi, Bronchioles, Alveoli and Lungs.

Question 6

define pleural cavity. what are its 2 layers?

Answer 6

The pleural cavity, also known as the pleural space or intrapleural space, is the potential space that exists between the two layers of a membrane called the pleura, which surrounds each lung. It’s filled with a small amount of serous lubricating fluid called pleural fluid.

Visceral pleura: The inner layer that closely adheres to the surface of the lungs.
Parietal pleura: The outer layer that lines the inner wall of the chest cavity (thoracic cavity).

Question 7

define nasal cavity

Answer 7

The nasal cavity, also sometimes called the nasal fossa, is the air-filled space inside your nose. It’s the very first chamber that inhaled air enters.

Question 8

define larynx
and define epiglottis

Answer 8

The larynx, also commonly referred to as the voice box, is a hollow, tube-shaped organ located in the upper part of the throat. It plays a critical role in both breathing and communication.

The epiglottis is a small, leaf-shaped piece of elastic cartilage located in the throat, specifically at the upper opening of the larynx (voice box).
When swallowing, the epiglottis reflexively folds down over the opening of the larynx. This action briefly seals the airway, preventing food or liquids from entering the trachea (windpipe) and lungs. Once the swallow is complete, the epiglottis returns to its upright position, allowing air to pass through the larynx freely for breathing.

Question 9

define nasopharynx

Answer 9

The nasopharynx, also sometimes referred to as the pharyngeal tonsil cavity is the uppermost section of the pharynx (throat) located behind the nasal cavity. It acts as a crossroads for air, food, and even sound, connecting several important structures.

Question 10

define oropharynx

Answer 10

The oropharynx, also sometimes referred to as the mid-pharynx, is the middle section of the throat located behind the mouth. It serves as a common pathway for both air and food, connecting several important structures.

Question 11

define trachea (layers and size)

Answer 11

The trachea, also widely known as the windpipe, is a tube-shaped organ in the respiratory system. It’s a vital conduit for air traveling between the larynx (voice box) and the lungs.

The trachea is a hollow, cylindrical tube measuring roughly 10-15 centimeters in length and about 2.5 centimeters in diameter.

-Mucosa: The innermost layer, also known as the mucous membrane. This layer is further divided into sub-layers:
Epithelium: This is the innermost surface lining, containing ciliated pseudostratified epithelium. These cells have tiny hair-like projections called cilia that move mucus upwards towards the pharynx.
Lamina propria: A connective tissue layer containing blood vessels, nerves, and glands. The glands within this layer produce mucus, which helps to trap dust, allergens, and other airborne particles.
-Submucosa: A layer of connective tissue containing blood vessels, nerves, and lymphatic vessels. It provides support and flexibility to the trachea.
-Hyaline cartilage: Crucially, the most distinctive feature of the trachea is a series of 16-20 incomplete C-shaped rings made of hyaline cartilage.
-Adventitia: The outermost layer, composed of loose connective tissue that anchors the trachea to surrounding structures in the chest. It also contains blood vessels and nerves.

Question 12

define thyroid cartilage

Answer 12

The thyroid cartilage, often referred to as Adam’s apple, is the largest cartilage structure within the larynx (voice box) and a key component of the respiratory system in terms of Protection, Voice production and Maintaining airway patency.

Question 13

what’s the pharynx?

Answer 13

The pharynx, also commonly referred to as the throat, is a muscular tube-shaped passageway that sits at the back of the nose and mouth and extends down the neck.
consists of: nasopharynx, oropharynx, laryngopharynx.

Question 14

define esophagus (and size)

Answer 14

The esophagus, also sometimes referred to as the gullet or food pipe, is a hollow, muscular tube that forms part of the digestive system. It serves as the passageway for food and liquids traveling from the pharynx (throat) to the stomach.
The esophagus is a muscular tube measuring roughly 25-30 centimeters in length in adults.

Question 15

define primary bronchi

Answer 15

The primary bronchi, also sometimes referred to as the main bronchi, are a pair of large tubes that branch off from the trachea (windpipe) at the carina (a ridge-like structure) in the lower part of the chest. They act as the initial pathways for air entering and exiting the lungs.

Question 16

define secondary lobar bronchi and tertiary segmental bronchi.

Answer 16

The secondary lobar bronchi, also simply called lobar bronchi, are the first major branches arising from each primary bronchus.
The tertiary segmental bronchi, also known as segmental bronchi, are the next level of branching after the secondary lobar bronchi.

Question 17

define bronchioles (and size)

Answer 17

Bronchioles are the finer airways within the lungs that form after the tertiary segmental bronchi.
diameter of about 1 millimeter or less.

Question 18

define terminal bronchioles (and size)

Answer 18

are the last branching point before the alveoli. They are even smaller than the initial bronchioles and have minimal smooth muscle.
0.5 mm

Question 19

define respiratory bronchioles

Answer 19

are even smaller airways that arise from terminal bronchioles and are directly connected to the alveoli. Their walls are lined with the specialized epithelium for gas exchange.

Question 20

define goblet cells

Answer 20

Goblet cells, also sometimes referred to as mucous cells, are specialized epithelial cells found throughout the lining of your respiratory system and digestive tract. Their primary function is to produce and secrete mucus.

Question 21

define alveoli (size, surface area)

Answer 21

are tiny, balloon-shaped air sacs located at the end of the bronchial tree in the lungs. They are the essential workhorses of the respiratory system, where the vital process of gas exchange takes place between inhaled air and your bloodstream.

• Air sacs - each with 200-300 alveoli
• surface area of ~ 100m^2
• Alveoli are microscopic, with a diameter of around 0.2-0.3 millimeters.
• extremely thin walls ( single layer of squamous epithelial cells ~ 0.5 micrometer thick )

Question 22

define mucus escalator

Answer 22

The mucus escalator, also referred to as mucociliary clearance or mucociliary transport, is a self-cleaning mechanism within the respiratory system. It’s a remarkable system that constantly works to remove dust, debris, mucus, and even pathogens inhaled into the airways.

Question 23

define alveolar duct

Answer 23

The alveolar duct is a tiny tube within the lungs that serves as a critical connection between the respiratory bronchioles and the alveolar sacs, the areas where gas exchange (oxygen and carbon dioxide) takes place.

Components:
Mucus: A sticky, wet secretion produced by goblet cells lining the airways. It traps dust, allergens, and pathogens inhaled with air.
Cilia: Tiny hair-like projections on the surface of cells lining the airways. They beat in a coordinated wave-like motion.

Question 24

do alveoli have cilia?

Answer 24

no

Question 25

what are alveolar macrophage cells?

Answer 25

Alveolar macrophages, also known as pulmonary macrophages or dust cells, are specialized immune cells residing within the alveoli of the lungs. They act as the first line of defense in the alveoli, safeguarding them from inhaled debris, pathogens, and harmful substances by phagocytosis.

Question 26

What is pneumocytes?
(type 1 cells and type 2 cells)

Answer 26

Pneumocytes, also sometimes referred to as pneumonocytes, are the cells that make up the lining of the alveoli (the epithelial layer).

Type I Pneumocytes are the most abundant type of pneumocyte, covering around 95% of the alveolar surface area. They are extremely thin and flattened squamous epithelial cells, with a central nucleus and a cytoplasm that extends very thinly. The primary function of type I pneumocytes is gas exchange. Their thinness allows for the efficient diffusion of oxygen from inhaled air in the alveoli into the bloodstream, and carbon dioxide in the opposite direction.

Type II Pneumocytes are cuboidal-shaped cells, less numerous than type I cells, covering about 5% of the alveolar surface area. They are larger and contain numerous organelles, including lamellar bodies that store components for surfactant production. The primary function of type II pneumocytes is the production and secretion of pulmonary surfactant. This special fluid reduces surface tension within the alveoli, preventing them from collapsing during expiration (breathing out). Additionally, type II cells have the ability to differentiate into type I cells, which is crucial for repair and renewal of the alveolar lining.

Question 27

what are blood capillaries in the alveoli wall doing?

Answer 27

Blood capillaries in the alveoli serve as the bridge between the respiratory system and the circulatory system, enabling gas exchange.
Blood capillaries form a dense network surrounding the alveoli, the tiny air sacs in the lungs.
These capillaries are microscopic blood vessels with walls composed of a single layer of thin endothelial cells. This thinness is crucial for efficient gas diffusion.

Question 28

What compose pulmonary surfactant?
What is the function?

Answer 28

Pulmonary surfactant is a complex mixture of substances that coats the inner surface (alveolar surface) of the alveoli in the lungs. It plays a vital role in maintaining lung function during respiration. The primary function of pulmonary surfactant is to reduce surface tension at the air-liquid interface within the alveoli.

Composition:
Phospholipids (around 80%): The major component is a specific phospholipid called dipalmitoyl phosphatidylcholine (DPPC). This phospholipid has a unique structure with a hydrophilic head group and two hydrophobic (water-hating) tail chains.
Proteins (around 10%): There are four main surfactant proteins (SP-A, SP-B, SP-C, and SP-D) that perform various functions like spreading the phospholipid layer and regulating the immune system in the lungs.
Neutral Lipids (around 10%): Cholesterol and other neutral lipids help maintain the stability and function of the surfactant layer.

Question 29

define respiratory membrane
(and its layers)

Answer 29

The respiratory membrane, also sometimes called the respiratory surface, is a thin barrier within the lungs where the crucial gas exchange between inhaled air and the blood takes place.

layers:
1. a thin layer of fluid lining the alveolus
2. the alveolar epithelium (simple squamous)
3. the basement membrane of the alveolar epithelium
4. a thin interstitial space
5. the basement membrane of the capillaries
6. the capillary endothelium (simple squamous)

Question 30

what are the functions of the respiratory system?

Answer 30

1. Gas Exchange: This is the primary function of the respiratory system. It involves the exchange of oxygen and carbon dioxide between inhaled air and the bloodstream.
2. Filtration:
   The respiratory system filters and prepares inhaled air before it reaches the delicate alveoli.
   Filtration: The hairs in the nose and mucus trap dust, pollen, and other debris from entering the airways.

3.Warming and moisten: The nasal cavity and paranasal sinuses warm and humidify inhaled air, making it more comfortable and suitable for gas exchange in the alveoli.

3. Voice Production:
   The larynx (voice box) plays a crucial role in voice production. The vocal cords within the larynx vibrate when air passes through them, producing sound. The shape of the oral and nasal cavities further modifies the sound to create speech.

Question 31

Explain the mechanics of breathing

Answer 31

Inspiration (Breathing In):
Diaphragmatic Contraction: The diaphragm contracts and flattens, increasing the volume of the chest cavity. This creates more space for the lungs to expand.
Ribcage Expansion: The external intercostal muscles contract, pulling the ribs upward and outward. This further expands the chest cavity volume.
Pressure Change: As the chest cavity volume increases, the pressure within the lungs decreases (becomes more negative) relative to atmospheric pressure. Think of it like creating a vacuum.
Airflow: Due to the pressure difference, air rushes from the atmosphere into the lungs through the airways. The lungs inflate to fill the increased space in the chest cavity.

Expiration (Breathing Out):
Diaphragmatic Relaxation: The diaphragm relaxes and returns to its dome-shaped position, decreasing the chest cavity volume.
Ribcage Relaxation: The external intercostal muscles relax, and the internal intercostal muscles contract, pulling the ribs downward and inward. This further reduces the chest cavity volume.
Pressure Change: As the chest cavity volume decreases, the pressure within the lungs increases (becomes less negative) relative to atmospheric pressure.
Airflow: Due to the pressure difference, air passively flows out of the lungs and up the airways to the atmosphere. The lungs deflate as the chest cavity volume shrinks.

Question 32

explain negative pressure breathing

Answer 32

Negative pressure breathing refers to techniques that utilize negative pressure, created externally, to assist ventilation (breathing). Unlike natural breathing, where the muscles actively contract and expand the chest cavity to draw air in, negative pressure breathing creates a vacuum around part of the body, typically the chest and abdomen, to achieve inhalation.

Question 33

define boyle’s law

Answer 33

Boyle’s law states that for a fixed amount of an ideal gas at a constant temperature, the pressure (P) of the gas is inversely proportional to its volume (V). Mathematically, this can be expressed as:
P * V = k

Question 34

What is the function of the external intercostal muscles?

Answer 34

The external intercostal muscles pull the ribs upward and forward during inhalation, helping to expand the chest cavity and draw air into the lungs.

Question 35

What is the function of the internal intercostal muscles?

Answer 35

The internal intercostal muscles assist with exhalation by depressing the ribcage. They help to breathe out by pulling the ribs down and inwards.

Question 36

inhalation and exhalation - what is passive and what is active?

Answer 36

Inhalation - Active
Exhalation - can be Passive (natural breathing) or active (forceful exhalation like coughing and exercise).

Question 37

define lung compliance

Answer 37

Lung compliance refers to the ease with which your lungs can stretch and expand during inhalation. It’s a measure of lung elasticity and how much they resist inflation.

Question 38

define vital capacity

Answer 38

Vital capacity (VC) refers to the maximum amount of air a person can forcefully exhale after taking the deepest possible breath. It’s a measure of the total lung volume a person can expel and is an indicator of lung function.

Question 39

define total lung capacity

Answer 39

Total lung capacity (TLC) refers to the total volume of air a person’s lungs can hold after the deepest possible inhalation. It’s a comprehensive measure that encompasses all the air compartments within the lungs.

Question 40

How much air can the lungs hold ?

Answer 40

4 to 6 liters

Question 41

define tidal volume

Answer 41

Tidal volume (TV), denoted by VT or TV, refers to the amount of air that moves in and out of the lungs with each breath during normal respiration at rest.

Question 42

define inspiratory reserve volume

Answer 42

Inspiratory reserve volume (IRV), refers to the extra amount of air a person can forcefully inhale.

Question 43

define expiratory reserve volume

Answer 43

Expiratory reserve volume (ERV), denoted by ERV, refers to the extra amount of air a person can forcefully exhale.

Question 44

define residual volume

Answer 44

Residual volume (RV) refers to the volume of air remaining in the lungs even after a forceful exhalation. It’s the air that cannot be expelled from the lungs and is essential for maintaining lung structure and preventing them from collapsing.

Question 45

define partial pressure.
What is the partial pressure of oxygen?

Answer 45

In a mixture of gases, each constituent gas exerts its own pressure, independent of the other gases present. This individual pressure of a gas component within a mixture is called its partial pressure. It’s denoted by the symbol p followed by a subscript representing the specific gas (e.g., pO2 for oxygen partial pressure).

In air, oxygen makes up about 21% of the total volume. The partial pressure of oxygen (pO2) at sea level is approximately:
pO2 = 0.21 ATM (atmospheres)
This can also be expressed as pO2 = 160 mmHg (millimeters of mercury)

Question 46

define atmospheric pressure
וwhat is the pressure at sea level. what does happen when you rise?

Answer 46

Atmospheric pressure, also known as barometric pressure, refers to the force exerted by the weight of the atmosphere pressing down on the Earth’s surface. It’s caused by the immense weight of air molecules in the atmosphere pushing inwards due to gravity.
At sea level, the average atmospheric pressure is about 1.013 bar = 760mmHg = 1ATM.

when you rise - the air thins out, meaning there are fewer air molecules pressing down. This results in a decrease in atmospheric pressure.

Question 47

what are the kinds of transport of oxygen in the blood? (what is the ratio between them?)

Answer 47

O2:
-dissolve in plasma (2%) - A small portion of both gases is directly dissolved in the blood plasma, similar to how a carbonated beverage holds CO2 bubbles. However, this method is inefficient for significant transport.
- bound to Hb (98%) - Most oxygen binds to hemoglobin that acts like a carrier for oxygen, attaching to four O2 molecules per hemoglobin molecule (HbO2). This creates a strong bond that allows for efficient transport of large amounts of oxygen throughout the body.

Question 48

define Hemoglobin
What is the structure of hemoglobin?

Answer 48

Hemoglobin (Hb) is an iron-containing protein found within red blood cells (erythrocytes). It plays a critical role in the respiratory system by acting as the primary carrier of oxygen (O2) from the lungs to tissues throughout the body. It also plays a role in transporting carbon dioxide (CO2) away from tissues back to the lungs for exhalation.

Structure of Hemoglobin:
-Each hemoglobin molecule has four globin chains, which are protein subunits (polypeptides). There are two main types of globin chains found in adult human hemoglobin:
Alpha (α) chains: Two alpha chains are present in each hemoglobin molecule.
Beta (β) chains: Two beta chains are also present, but there can be slight variations in their structure depending on the specific type of hemoglobin.
-4 Heme Groups: Each globin chain is tightly bound to a heme group, a prosthetic group containing iron. The iron atom within the heme group is central to oxygen binding.
Quaternary Structure: The four globin chains (two alpha and two beta) are arranged in a specific spatial configuration, with each heme group located within a pocket formed by the globin chains. This structure allows for cooperative oxygen binding.

primary -amino acids to chain
secondary - a and b subunits
tertiary - how it bends in space (only one)
quaternary - all the 4 together with the heme groups.

Question 49

oxygenated blood/deoxygenated blood? what is darker?

Answer 49

Deoxygenated blood is darker than oxygenated blood.
When hemoglobin binds to oxygen (oxygenated blood), it gives the blood a brighter red color. This form of hemoglobin is called oxyhemoglobin.
When hemoglobin releases oxygen in tissues (deoxygenated blood), it has a darker red appearance.

Question 50

how the ability to bind to O2 is influenced by the partial pressure?

Answer 50

the greater the pO2 in the blood the more easily O2 can bind to Hb.

Question 51

what affect the hb affinity for O2?

Answer 51

• O2 reach areas (such as lungs) promotes O2 loading = high affinity = high saturation of Hb.

Higher pO2 (more oxygen) in the lungs promotes oxygen binding to hemoglobin, increasing its affinity. This ensures efficient loading of oxygen for transport.
Lower pO2 (less oxygen) in tissues triggers the release of oxygen from hemoglobin, as the affinity decreases. This allows oxygen delivery to tissues with lower oxygen demands.

Question 52

define cooperative binding

Answer 52

Cooperative binding refers to a specific type of interaction between a molecule and multiple ligands (binding molecules) where the binding of one ligand influences the affinity of the remaining binding sites for subsequent ligands.

When the first oxygen molecule binds to one of the four heme groups in hemoglobin, it triggers a conformational change in the molecule.
This change increases the affinity of the remaining heme groups for oxygen, making it easier for them to bind subsequent oxygen molecules.
As a result, hemoglobin can efficiently load up to four oxygen molecules at its binding sites in the lungs.

Question 53

what is the dissociation curve and what are the factors affect the dissociation curve?

Answer 53

The oxygen-hemoglobin dissociation curve (HbO2 dissociation curve) is a graphical representation of the relationship between the partial pressure of oxygen (pO2) and the percentage of hemoglobin (Hb) saturated with oxygen. Several factors can influence the shape and position of this curve, affecting how readily hemoglobin binds and releases oxygen.

1. Partial Pressure of Oxygen (pO2):
   This is the main factor influencing oxygen binding.
   Higher pO2 (more oxygen) in the lungs promotes oxygen binding to hemoglobin, shifting the curve to the left. This ensures efficient loading of oxygen for transport.
   Lower pO2 (less oxygen) in tissues triggers the release of oxygen from hemoglobin, shifting the curve to the right. This facilitates oxygen delivery to tissues with lower oxygen demands.
2. pH :
   Blood pH affects the shape of the hemoglobin molecule, influencing its binding sites for oxygen. This is known as the Bohr effect.
   lower pH decreases hemoglobin’s affinity for oxygen, favoring release. This is crucial for efficient oxygen delivery to tissues that produce CO2, which lowers blood pH. This shift is represented by a rightward shift of the curve.
   higher pH increases hemoglobin’s affinity for oxygen, hindering release. This shift is a leftward movement of the curve.
3. Increased pCO2 (higher carbon dioxide levels) leads to a decrease in blood pH (acidosis). that weakens hemoglobin’s affinity for oxygen. the Bohr effect triggered by it causes a rightward shift of the curve.
4. Temperature:
   Higher body temperature can slightly decrease hemoglobin’s affinity for oxygen, promoting oxygen release at the tissue level. This may aid in supplying oxygen during exercise or fever. This shift appears as a rightward shift of the curve. and vice versa.
5. 2,3-Diphosphoglycerate (2,3-DPG):
   This molecule, produced by red blood cells, binds to hemoglobin and affects its oxygen affinity.
   Higher levels of 2,3-DPG decrease hemoglobin’s affinity for oxygen, facilitating release in tissues. This shift is a rightward movement of the curve.
   Lower levels of 2,3-DPG (e.g., due to certain medical conditions) can increase hemoglobin’s affinity for oxygen, potentially hindering its release at the tissue level. This shift appears as a leftward shift of the curve.
6. Carbon Monoxide (CO):
   CO has a much higher affinity for hemoglobin than oxygen. If CO is inhaled (e.g., from cigarette smoke or car exhaust), it readily binds to hemoglobin, displacing oxygen and significantly reducing oxygen-carrying capacity. This shift appears as a leftward movement of the curve, but with a reduced overall oxygen-binding capacity.

Question 54

define carbon monoxide

Answer 54

Carbon monoxide (CO) is a colorless, odorless, and tasteless gas.
the CO acts as competitive inhibitor
It binds to hemoglobin (carboxy-Hb) in red blood cells with an affinity much higher than oxygen (over 200 times stronger). This displaces oxygen from hemoglobin, significantly reducing the blood’s capacity to carry oxygen throughout the body.

Question 55

what does a rightward shift in the dissociation curve mean?

Answer 55

decrease in affinity of Hb for O2 - it’s harder for Hb to bind to O2.

Question 56

what is fetal Hb? (explain about the affinity for O2 and how does it affect the dissociation curve?)

Answer 56

Fetal hemoglobin (HbF) is the primary hemoglobin type present in red blood cells of a developing fetus during the latter half of pregnancy (from around 10-12 weeks of gestation) and the first few months after birth. It gradually transitions to the adult form of hemoglobin (HbA) over the first 6-9 months of life.

Compared to adult hemoglobin, fetal hemoglobin has a higher affinity for oxygen at lower oxygen concentrations (pO2). This is crucial in the environment of the placenta, where oxygen levels are lower than in the mother’s lungs. The higher affinity allows HbF to effectively capture oxygen from maternal blood. The HbF dissociation curve is shifted to the left compared to the adult hemoglobin curve.

Question 57

define myoglobin.
how does it affect the dissociation curve?

Answer 57

Myoglobin is a single-chain protein with a heme group similar to hemoglobin. The heme group contains iron, which binds to oxygen molecules.
Myoglobin is a protein found in muscle cells that plays a crucial role in oxygen storage and diffusion within muscles.

Since myoglobin has only one heme group and doesn’t exhibit cooperative binding, its dissociation curve is a simple hyperbola. Myoglobin has a higher affinity for oxygen compared to hemoglobin at rest. it is more to the left.

Question 58

what are the kinds of transport of carbon dioxide in the blood? (what is the ratio between them?)

Answer 58

-Dissolved in plasma (5%) - Similar to oxygen, a small amount of CO2 dissolves directly in blood plasma.
- Bicarbonate conversion ( 75%) - The majority of CO2 reacts with water (H2O) inside red blood cells in the presence of an enzyme called carbonic anhydrase. This reaction converts CO2 to bicarbonate (HCO3-). Bicarbonate then diffuses out of red blood cells and into the blood plasma for transport. This conversion is important because CO2 is not very soluble in blood, but bicarbonate is much more soluble, allowing for efficient transport of larger quantities of CO2.
- Carbaminohemoglobin (20%) - A smaller portion of CO2 binds directly to hemoglobin molecules (carbaminohemoglobin= HbCO2), forming a weaker bond compared to oxygen-hemoglobin binding.

Question 59

define carbonic anhydrase (and functions)

Answer 59

Carbonic anhydrase is an enzyme found in various tissues throughout the body, but especially in red blood cells.

1. Conversion of Carbon Dioxide (CO2) to Bicarbonate (HCO3-):
   Carbon dioxide, a waste product of cellular respiration, needs to be efficiently removed from the body. In red blood cells, carbonic anhydrase facilitates the rapid conversion of CO2 to bicarbonate ions (HCO3-). This reaction occurs according to the following equation:
   CO2 + H2O -> HCO3- + H+ (hydrogen ion)
   The presence of carbonic anhydrase significantly accelerates this reaction, ensuring efficient CO2 conversion for transport in the blood.
2. Bicarbonate Conversion Back to CO2:
   In the lungs, where the blood gets rid of CO2, the process needs to be reversed. Carbonic anhydrase again plays a crucial role by facilitating the conversion of bicarbonate back to CO2, which can then be exhaled.

Question 60

define bohr effect
how does it affect the dissociation curve?

Answer 60

The Bohr effect describes the way red blood cells adjust their oxygen-carrying capacity based on their environment.
decrease in pH is causing a rightward shift of the curve.

the binding affinity of hemoglobin for oxygen decreases under two conditions:
-Increased CO2 Concentration: As CO2 levels rise in tissues (a sign of increased cellular activity), hemoglobin releases more readily bound oxygen. This ensures oxygen delivery to tissues that need it most.
-Increased Acidity (Lower pH): When tissues become more acidic due to the buildup of metabolic byproducts, hemoglobin’s affinity for oxygen weakens. This again facilitates oxygen unloading in those areas.

Question 61

how does CO2 affect the pH of the blood?

Answer 61

as CO2 levels increase, the pH decrease (more acidic).

Question 62

what is HHb?

Answer 62

When a heme group in hemoglobin does not have an oxygen molecule attached, it’s called deoxyhemoglobin (HHb).
This form arises in tissues where oxygen is released for cellular respiration.

Question 63

what is basic rhythm of breathing?
how is it controlled?

Answer 63

The basic rhythm of breathing is an involuntary process controlled by a complex interplay between the brainstem and respiratory centers (medulla oblongata).
In a healthy adult at rest, the normal breathing rate is around 12-20 breaths per minute.

Question 64

define pontine respiratory group. is it the main respiratory center?

Answer 64

The pontine respiratory group (PRG) is a cluster of neurons located in the pons, a region of the brainstem involved in various functions like sleep, wakefulness, and sensory processing. The PRG plays a specific role in regulating the rhythm and pattern of breathing, but it’s not the main control center.]

The brainstem, specifically the medulla oblongata, houses the dorsal and ventral respiratory groups (DRG and VRG). These groups act as the primary control center for breathing rhythm, sending signals to the diaphragm and intercostal muscles for inhalation and exhalation.

Question 65

where receptors that regulate breathing are located? how they function?

Answer 65

There are two main groups of receptors that regulate breathing located in different areas of the body:

1. Central chemoreceptors: These are located in the brainstem, near the medulla oblongata. They are primarily sensitive to changes in carbon dioxide (and pH) levels in the cerebrospinal fluid (CSF) surrounding the brain. Their location within the brainstem allows them to directly monitor CO2 levels in the CSF, which reflects the body’s overall CO2 levels. Increased CO2 levels act as a signal to stimulate breathing, promoting CO2 elimination.
2. Peripheral chemoreceptors: These are situated in two clusters outside the brainstem. Situated near major blood vessels, they can quickly detect changes in blood oxygen levels.
   Carotid bodies: Located at the bifurcation (division) of the common carotid arteries on either side of the neck.
   Aortic bodies: Found near the arch of the aorta, the major artery leaving the heart.
   When the bodies sense a drop in oxygen or an increase in CO2/acidity, they release excitatory neurotransmitters.
   These neurotransmitters stimulate the respiratory center in the brainstem, located in the medulla oblongata. The brainstem, in turn, sends signals to the diaphragm and intercostal muscles, which control breathing. This reflex response leads to an increase in breathing rate and depth, promoting more oxygen intake and CO2 elimination.

Question 66

define anaerobic threshold

Answer 66

The anaerobic threshold (AT), also known as the lactate threshold, is a crucial concept in exercise physiology. It marks the exercise intensity at which the body transitions from primarily relying on aerobic metabolism (using oxygen) to anaerobic metabolism (without oxygen) for energy production.

Question 67

what reflexes can modify breathing?

Answer 67

sneeze, cough and Hering Breuer

Hering-Breuer Reflex (Inflation Reflex):
This reflex is triggered by stretch receptors in the lungs. When the lungs inflate during inhalation, these receptors send signals to the brainstem, leading to the inhibition of inspiration and initiation of exhalation. This reflex helps to prevent overinflation of the lungs and maintain a regular breathing rhythm.