ANSC 220 Lecture 17: Cardiovascular IV and Respiratory System

Mean Arterial Pressure (MAP)

The average blood pressure generated during a single cardiac cycle that measures the driving force of blood through the cardiovascular system, calculated as $\text{MAP} = 120 + \frac{2 \times 80}{3} = 93\,\text{mmHg} = \text{CO} \times \text{TPR}$.

Total Peripheral Vascular Resistance (TPR)

The resistance to blood flow provided primarily by arterioles, which is constantly modified to regulate and correct for changes in mean arterial pressure.

Myogenic Activity

An intrinsic property of arteriolar smooth muscle where mechanical stretch of the vessel wall naturally induces contraction and vasoconstriction.

$\alpha_1$-Adrenergic Receptors

Receptors located on smooth muscle surrounding arterioles in most tissues that bind sympathetic norepinephrine and epinephrine to induce vasoconstriction and increase total peripheral resistance.

$\beta_2$-Adrenergic Receptors

Receptors with a high affinity for epinephrine located on arteriolar smooth muscle in the heart and skeletal muscle, which trigger vasodilation to increase blood flow during activity or stress.

Capillary Endothelium

A single layer of simple squamous epithelial cells (endothelial cells) measuring only $1\,\mu\text{m}$ in thickness, containing intercellular pores or fenestrations that enable diffusion and filtration without tight junctions.

Plasma Colloid Osmotic Pressure (Oncotic Pressure)

An inward osmotic force generated by large plasma proteins (particularly albumins) that cannot cross the capillary wall, which helps pull water back into the vessel and maintain forward flow.

Capillary Ultrafiltration

The outward bulk flow of water and small solutes from the capillary into the interstitial fluid, promoted by capillary blood pressure ($P_c$) and interstitial fluid-colloid osmotic pressure ($\pi_{\text{IF}}$).

Capillary Reabsorption

The inward movement of fluid from the interstitial space back into the capillary lumen, promoted by plasma colloid osmotic pressure ($\pi_p$) and interstitial fluid hydrostatic pressure ($P_{\text{IF}}$).

Edema

The abnormal accumulation of fluid and swelling in the interstitial space and tissues, caused by reduced plasma proteins, abnormally elevated blood pressure, or altered capillary filtration.

Venous Reservoir

The venous system serving as a low-pressure blood reservoir that contains approximately $60\%$ of total body blood volume due to high distensibility and large radii.

Venous Valves

One-way structural valves found in veins that prevent the backflow of blood, ensuring unidirectional flow toward the heart under low pressure.

Arterial Baroreceptors

Mechanoreceptors located in the carotid sinus and aortic arch that detect variations in mean arterial pressure and transmit action potentials to the cardiovascular control center in the medulla oblongata.

Baroreceptor Reflex

An autonomic homeostatic response mediated by the medulla oblongata that modulates heart rate, stroke volume, and vascular resistance in response to afferent signals from baroreceptors.

Ventilation

The initial step of external respiration involving the bulk movement of an external medium (air or water) across or through a gas exchange surface.

Respiratory Exchange

The second step of external respiration where oxygen and carbon dioxide diffuse across the respiratory boundary between the external environment and the animal's internal body fluids.

Respiratory Circulation

The third step of external respiration consisting of the transport of dissolved or bound oxygen and carbon dioxide throughout the body via extracellular fluids such as blood.

Cellular Gas Exchange

The fourth step of external respiration involving the diffusion of oxygen and carbon dioxide between circulating extracellular fluid and tissue cell cytoplasm.

Tidal Ventilation

A respiratory flow mechanism common in terrestrial animals where air moves into and out of the gas exchange structures through the same opening.

Flow-Through Ventilation

A highly efficient respiratory flow mechanism utilized by aquatic animals such as fish, where water enters through one opening (mouth) and exits via a separate opening (operculum/gills).

Conchae (Nasal Turbinates)

Thin scrolls of cartilage and bone lined with vascularized mucosa located within the nasal cavity that warm, humidify, and retain moisture and heat during respiration.

Pharynx

The throat region that functions as a common passageway for both air and ingested food prior to diverging into the trachea and esophagus.

Glottis