3 - Regulation of Vasculature Flashcards
What is th emost important part of the autonomic nervous system for regulating circulation?
What vessels are innervated?
Sympathetic Nervous System
All vessels except capillaries
What organs’ vessels receive parasympathetic innervation?
What type of role does the PsNS play in systemic circulation?
What does it play a large role in?
Salivary Glands
Pancreas
Gastric Mucosa
External Genitalia
Does not play a large role in systemic resistance and thus arterial blood pressure
Regulation of heart function
What are the sympathetic neurotransmitters and receptors that are found on blood vessels?
Neurotransmitter: NE, released by sympathetic adrenergic nerves
Receptor: a1-adrenoceptors
Causes smooth muscle contraction and vasoconstriction
What center of the brain is tonically active to maintain vascular tone?
What is this firing termed?
What is the partial state of contraction in vessels termed?
What if you were to knock out this center?
Vasoconstrictor area of the Vasomotor Center
Sympathetic Vasoconstrictor Tone
Vasomotor Tone
Significant vasodilation and hypotension
What reflex mechanisms are important for maintaining normal arterial pressure?
Arterial Baroreceptors found in the carotid sinus and in the aortic arch
Stretch = High BP, engages parasympathetics
No Stretch = Low BP, engage sympathetics
When you quickly stand from a laying down, what systems are engaged?
Suddent drop in BP from gravity pooling in lower extremity, stretch reflex signal low BP, (+) Sympathetic and (-) Parasympathetic
Where are cardiopulmonary receptors found? What do they respond to?
What impact would increased centra venous pressure/volume cause?
What hormone is inhibited by an increase in blood volume and venous pressure by these receptors?
Venoatrial Junctions of the heart; respond to atrial filling and contraction
Activation of these receptors by stretch, reflex decrease in sympathetic activity
(-) ADH, Vasopressin @ Posterior Pituitary
This causes diuresis, with lowers blood volume and venous pressure
Where are peripheral chemoreceptors round?
How does their firing change with changes to oxygen, carbon dioxide, and pH?
Carotid Artery
Aortic Arch
- - -
Increase firing in response to low oxygen or high carbon dioxide and acidosis (low pH or high [H+])
What would be the results if a patient breathed gas mixture with substantially lower oxygen PPM?
(ex. athlete from sea level city playing Denver Broncos in Denver)
Chemoreceptor activation increases respiratory activity and stimulates sympathetic activity to the heart and systemic vasculature
Circulating Catecholamines:
Where are they released from?
What receptors do these target?
Sympathetic activation causes Epinephrine and Norepinephrine (catecholamine) release from the adrenal medulla
Activate B1-Adrenergic receptors to increase HR / Inotropy (contractility)
Activate vascular a1 receptors to cause casoconstriction
What are the difference between a high and low level of catecholamine circulation?
Moderately increased epinephrine can cause vasodilation (B2 receptor)
High levels cause vasoconstriction (a1 receptor)
What system plays an important role in regulating and connecting blood volume, cardiac, vascular function, and arterial blood pressure?
What is the end result?
Renin-Angiotensin-Aldosterone System
Increase blood pressure
What is Atrial Antriuretic Peptide (ANP)?
Where is it synthesized, stored, and released?
What does thi act antagonistically to?
What is the end result?
Involved in long-term regulation of sodium water balance, blood volume, and atrial pressure
Made, stored, released by atrial myocytes
Acts antagonistically with Renin-Angiotensin-Aldosteron System
DECREASE blood pressure
Where is Vasopressin (Antidiuretic Hormone, ADH) released?
Where does it act?
What is the end result of its function?
Posterior Pituitary
Kidneys, Blood Vessels
Increased Arterial Pressure
What regulates the relative distribution of blood flow to organs? (local level regulation)
What factors can influence this?
The vascular resistance of the individual organs
Neurohumoral and Local Regulatory
Metabolic Influences:
How would an increase in metabolism change local blood flow?
Decrease in available oxygen?
Increase in metabolism = increase in blood flow
Decrease in local oxygen = increase in blood flow
What is the vasodilator theory?
The greater the rate of metabilism, the greater the rat of formation of vasodilator sibstance in the tissue cells–causing relaxation of smooth muscle
Substances: Adenosine, CO2, K+, H+
What is the Oxygen Lack Theory?
Oxygen is required for muscular contraction, if it is absent–vessels will dilate.
What is Reactive Hyperemia?
What is Active Hyperemia?
The transient increas in organ blood flow following brief ischemia
- - -
Increase in organ blood flow that is associated with increased metabolic activity or an organ or tissue
Clinical: What would result following clamp of blood vessels once blood flow is restored?
Reactive Hyperemia
(increased blood flow for a brief period of time)
What is the importance of active hyperemia?
When does it occur?
Increases oxygen to tissues to meet increased demands, aid removal of metabolic waste products from tissues
Occurs during: Muscle contraction, incresed cardiac activity, increased mental activity and increased activity during food absorption
What paracrine hormones are involved in regulation of blood flow that are not directly related to tissue metabolism?
Histamine, Bradykinin
When is histamine released?
What is the effect on capillaries?
When are these reactions prominent?
When tissue becomes damaged or inflamed, or subject to allergic reaction
Vasodilator effect on the arterioles, increase capillary permeability
Allergic reactions
Where is bradykinin formed and when is it released?
What s it’s impact on vessels?
What other roles does it play?
Formed in blood and tissue fluids during inflammation
Dilation/permeability
Helps regulated blood flow to the skin, salivary, and GI glands
What role do endothelial substances play in the paracrune regulation of s.muscle tone and blood flow?
Nitric Oxide (NO): Vasodilators
Endothelial Derived Hyperpolarizing Factor (EDHF): Vasodilator
Endothelin-1 (ET-1): Vasoconstrictor
Aracidonic Acid Metabolites: PGI2 - Dilator, Thromnoxanes/Leukotriends - Constrictors
What is the myogenic response?
When lumen of vessel suddenly expanded, smooth muscle responds by contracting to restore diamete and resistance
Reduction in pressure results in relaxation/vasodilation
What substances can autoregulate?
High Degree
Moderate
None
On a graph, what are would this be represented by?
High - Coronary, Cerebral, Renal
Moderate - Skeletal muscle, GI
None - Cutaneous circulation
Like a buffer titration–the flat area that change of dependent variable results in little change of independents variable
What three methods of autoregulation are likely involved in physiological response?
Oxygen Low = Increase BP
Accumulation of Metabolites = Increase BP
Decrease P sensed by smooth muscles = Increase Flow
Clinical: In hypotension caused by blood loss (GSW, trauma, etc) why do blood flow to the heart and brain remain steady (to an extent)?
Strong capacity to autoregulate using various mechanisms; escape vasoconstrictor sympathetics influences
If arterial pressure falls below autoregulatory range, this system is lost
u die m8
Clinical: What is the importance of autoregulation should a distributing artery become occluded (e.g. coronary artery)?
Increased resistance at one end, pressure drop along length; distal vessels pressure drop
Distal vessels dilate (resistance vessels)
Clinical: Orthostatic Hypotension
When a person suddenly moves form a supine to standing position
