Hormonal Regulation of Blood Pressure and Respiratory Physiology

Flashcards covering hormonal blood pressure regulation (Adrenergic, ADH, Renin-Angiotensin systems) and respiratory anatomy and mechanics (lung structures, pleura, and pressures).

Catecholamines

Hormones including epinephrine and norepinephrine (adrenaline and noradrenaline) released by the adrenal gland in response to sympathetic stimulation to increase cardiac output and total peripheral resistance.

Alpha adrenoceptors

Receptors that, when stimulated, activate phospholipase C and increase cytosolic $Ca^{2+}$, leading to vasoconstriction.

Beta adrenoceptors

Receptors that activate adenylyl cyclase and produce cAMP upon stimulation, ultimately leading to vasodilation.

Vasopressin (Anti-Diuretic Hormone; ADH)

A hormone synthesized in the Paraventricular Nucleus of the hypothalamus and stored in the posterior pituitary that raises blood pressure through vasoconstriction and water retention.

Renin

An enzyme released by the kidneys in response to low blood pressure that converts angiotensinogen into angiotensin I.

Angiotensin II

A hormone converted from angiotensin I by ACE that causes vasoconstriction and the release of ADH; it has the greatest pressor effect of any substance in the human body.

ACE (Angiotensin Converting Enzyme)

An enzyme found in lung capillaries that converts angiotensin I into the more active hormone angiotensin II.

Diaphragm

A curved, thin muscle located under the lungs that serves as the major respiratory muscle in humans, separating the thoracic and abdominal cavities.

Cardiac notch

A slight indentation in the left lung caused by the position of the heart, making the left lung narrower than the right.

Airway patency

The rigidity of the trachea, maintained by rings of cartilage, which prevents its collapse.

Obstructive sleep apnea

A condition accounting for approximately $90\%$ of sleep apnea cases, occurring when relaxed upper airway muscles and excess tissue weight cause the trachea to collapse.

Epiglottis

A flap of tissue that covers the glottis during the swallowing reflex to prevent food and drink from entering the trachea.

Conducting zone

The region from the trachea down to the terminal bronchioles where no gas exchange occurs; it warms and humidifies air and contains approximately $150\,ml$ of anatomical dead space.

Respiratory zone

The region consisting of respiratory bronchioles, alveolar ducts, and alveoli where gas exchange occurs.

Phrenic nerve

The nerve that innervates the diaphragm, arising from the spinal column at the level of the $4^{th}$ to $5^{th}$ cervical vertebrae.

Visceral pleura

The innermost membrane of the pleural sac that directly coats the exterior of the lung.

Parietal pleura

The membrane of the pleural sac that coats the inner chest wall.

Pleurisy

A disorder where the visceral and parietal pleura rub against each other and become inflamed, causing severe chest pain during breathing.

Interpleural pressure

The pressure within the pleural space, which is typically negative at approximately $756\,mmHg$ ($-4\,mmHg$ relative to atmospheric pressure).

Transpulmonary pressure

The difference between intra-alveolar pressure and intrapleural pressure, which serves as the driving force for lung expansion.

Pneumothorax

A condition where air leaks into the pleural cavity, causing intrapleural pressure to lose its negative value and leading to lung collapse.

Tension pneumothorax

A life-threatening condition where air enters the pleural space through a one-way valve wound but cannot exit, compressing the heart and the non-collapsed lung.

Haemothorax

A condition in which blood enters the pleural space, typically caused by physical trauma.

Pleural effusion

An accumulation of fluid within the pleural space or alveoli caused by factors like pulmonary edema, infection, or low blood protein levels.