Blood Pressure Regulation and Capillary Dynamics

Comprehensive vocabulary flashcards covering blood pressure regulation, renal mechanisms, the RAA system, local tissue perfusion, and capillary exchange dynamics based on the lecture transcript.

Baroreceptors

Sensory receptors that monitor blood pressure and adapt quickly to chronic changes, effectively being "reprogrammed" to a person's personal norm rather than a homeostatic normal.

Direct Renal Mechanism

A long-term blood pressure regulation method where the kidneys adjust blood volume through filtration rate changes without the use of hormones.

Renin-angiotensin-aldosterone (RAA) mechanism

An indirect renal mechanism that activates when blood pressure falls too low, involving a cascade of hormones to increase blood volume and pressure.

Renin

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

Angiotensinogen

An inactive plasma protein produced by the liver that circulates in the blood at all times.

Angiotensin converting enzyme (ACE)

An enzyme responsible for converting the inactive hormone angiotensin I into the active, potent hormone angiotensin II.

Angiotensin II

An active hormone that acts as a potent vasoconstrictor, stimulates the hypothalamic thirst center, and triggers the release of ADH and aldosterone.

Antidiuretic hormone (ADH)

A water-conservation hormone stored in the posterior pituitary that tells the kidneys to reabsorb more water, reducing urine output.

Aldosterone

A salt-conservation hormone released by the adrenal cortex that causes the kidneys to reabsorb more salt; water follows this salt via a gradient, increasing blood volume.

Orthostatic hypotension

A temporary drop in blood pressure resulting from changing posture quickly (straight to standing), leading to dizziness due to inadequate oxygen delivery to the brain.

Primary (Essential) hypertension

A form of high blood pressure with no specific underlying medical cause, accounting for approximately $90\%$ of hypertensive cases and controlled primarily by lifestyle changes.

Secondary hypertension

A less common form of high blood pressure (approx. $10\%$ of cases) caused by identifiable disorders such as kidney disease or endocrine disorders.

Tissue perfusion

The flow of blood through body tissues and capillary beds for gas exchange, nutrient delivery, and waste removal.

Intrinsic control (Autoregulation)

The automatic, local adjustment of blood flow to each tissue in proportion to its specific metabolic requirements at any given moment.

Extrinsic control

Control of blood flow via the nervous and endocrine systems used to maintain constant systemic blood pressure by reducing flow to tissues with low metabolic demand.

Metabolic controls

Intrinsic chemical signals, such as low oxygen or increased $CO_2$ and hydrogen ions, that stimulate local vasodilation to increase blood flow.

Nitric oxide

A potent vasodilator released by the lining of blood vessels to override vasoconstriction and increase tissue perfusion.

Myogenic control

An intrinsic mechanism where vascular smooth muscle responds to stretch from high pressure by constricting to protect downstream capillaries.

Angiogenesis

A long-term autoregulation process where the body increases the number and size of blood vessels in a specific region to meet oxygen and nutrient needs.

Bulk flow

The movement of fluid between the capillaries and tissue spaces which determines fluid volume distribution in the body.

Filtration

The movement of fluid from the bloodstream out into the tissue spaces, which typically occurs at the arterial end of the capillary bed.

Reabsorption

The movement of fluid from the tissue spaces back into the bloodstream, which typically occurs at the venous end of the capillary bed.

Capillary hydrostatic pressure ($HP_c$)

The pressure of the blood pressing against the capillary wall from the inside, acting as a "pushing" force to move fluid out of the vessel.

Colloid osmotic pressure ($OP_c$)

An inward "sucking" or "pulling" force created by large, non-diffusible plasma proteins that keeps fluid within the bloodstream.

Net filtration pressure (NFP)

The total of all forces acting on a capillary bed; a positive value indicates filtration, while a negative value indicates reabsorption.

Lymphatic vessels

Drainage vessels that pick up the remaining $15\%$ of leaked fluid and plasma proteins from tissue spaces and return them to the venous circulation.

Edema

An abnormal increase in the amount of interstitial fluid out in the tissue spaces.