Chapter 17 & 18 Cardiovascular Regulation Handout Flashcards
2 phases of local blood flow control
- Acute control
2. Long term control
What are some specific needs of the tissues for blood flow?
- Delivery of O2 to tissues
- Delivery of other nutrients (glucose, AA, FA)
- Removal of CO2 from tissues
- Removal of hydrogen ions from tissues
- Maintenance of proper concentrations of other ions in tissues
- Transport of barious hormones and other substances to different tissues
This type of local blood flow control is achieved by rapid changes in local vasodilation or vasoconstriction of the arterioles, metarterioles, and precapillary sphincters, occuring within seconds to minutes to provide very rapid maintenance of appropriate local tissue blood flow.
Acute control
A phase of local blood control wherein There is slow controlled changes in flow over a period of days, weeks, or even months.
Long-term control
What are the reflex mechanisms for normal BP?
- Baroreceptor reflex
- Chemoreceptor reflex
- Volume reflex
- Bainbridge reflex
- Cushing reaction
Most important endothelium-derived vasodilator substance
Nitric Oxide
What does the chemoreceptors sense?
- O2 lack
- CO2 excess
- H+ excess (low flow from nutrient artery)
What will happen to the BP when you clamp both carotid arteries?
Increase
What is the cushing’s triad?
Increased ICP
Increased BP
Bradycardia
It is a requirement for smooth muscle contraction in vessels
Oxygen
What vitamin is involved in oxygen-induced phosphorylation to produce ATP in cells?
Vitamin B (thiamin, niacin,riboflavin)
True or False:
Decrease in Vitamin B and other nutrients resultto decreased smooth muscle activity and consequently vasodilation.
True
Two basic theories for the regulation of local blood flow when either the rate of tissue metabolism changes or the availability of O2 changes.
- Vasodilator Theory
2. Oxygen Lack Theory
According to this theory, the greater the rate of metabolism or the less availability of O2 or some other nutrient to a tissue, the greater the rate of formation of vasodilator substances in the tissue cells.
Vasodilator Theory
O2 lack theory is also known as…
Nutrient Lack Theory
What are examples of vasodilator substances?
CO2 Adenosine Phosphate Coompunds Histamine K ions H+ ions
A disease caused by vitamin B deficiency
Beriberi
Special mechanism involved in metabolic control of local blood flow
- Reactive hyperemia (blood supply to tissue is blocked for a few seconds to as long as an hour or more)
- Active hyperemia (when tissues become highly active - exercise)
Return of blood flow after an acute rise from sudden increase in arterial pressure
Autoregulation
Most important local vasodilator for controlling local blood flow
Adenosine
What are the 2 mechanism in autoregulation?
- Metabolic theory (excess flow of nutrient –> vasoconstriction)
- Myogenic theory ( vascular stretch –> inc ca+ entry –> vasoconstriction)
* metabolic factors can override myogenic mechanisms in dramatic alterations
Where is the myogenic response more pronounced?
Arterioles
Myogenic response is initiated by ____
Stretch-induced vascular depolarization
This autoregulation mechanism is important in preventing excessive stretch of BV when BP is increased
Myogenic mechanism
True or False:
The level of excitability of the brain is highly dependent on exact control of both Co2 & H+ ion concentration
True
Half life of nitric oxide
6 seconds
Stimulus for secretion of Vascular Endothelial Growth Factor (VEGF)
Continued lack of O2
Vasoconstrictor Agents
NE Eponephrine Angiotensin II Vasopressin Endothelium
A potent vasoconstrictor created in the adrenal medulla
Norepinephrine
A less potent vasoconstrictor which can even cause VASODILATION
Epinephrine
Very potent vasoconstrictor of arterioles
Angiotensin II
A vasocontrictor more powerful than angiotensin II. It is formed in nerve cells in the hypothalamus of the brain. PPG secretes this.
*major function: water reabsorption from the renal tubules back into the blood
Vasopressin / Antidiuretic hormone
Vasodilator Agents
Bradykinin
Histamine
Vasodilator prominent in allergic reactions
Histamine
A vasodilator which regulates blood flow in skin, salivary glands and GI glands
Bradykinin
The most important part of the ANS for regulating the circulation
Synoathetic Nervous System
Part of the ANS which regulates heart function
Parasympathetic Nervous System
Where is the vasomotor center located?
Located bilaterally mainly in the reticular substance of the medulla and of the lower third of the pons
True or False:
The vasomotor center can either increase or decrease heart activity.
True
True or False:
Heart rate & strength of contraction
Increase - vasoconstriction
Decrease - vasodilation
True
True or False:
The nervous control of arterial pressure is by far the most rapid of all our mechnisms for pressure control
True
This reflex mechanism for normal BP is initiated by stretch receptors
Baroreceptor Reflex
Barorecptors are extremely abundant in?
- Carotid artery specifically in the carotid sinus
2. Wall of aortic arch
True or False:
The baroreceptors respond much more to a rapidly changing pressure than to a stationary pressure.
True
Primary purpose of the arterial baroreceptor system
Reduce minute-by-minute variation in arterial pressure
to about 1/3 that which would occur if the baroreceptor system was not present
It is not a powerful controller until BP reaches below 80 mmHg.
It is at lower pressures that this reflex becomes important to help prevent further decreases in arterial pressure
Chemoreceptor Reflex
True or False:
Vasomotor center
Vasoconstrictor area - anterolateral portions of UPPER MEDULLA
True
True or False:
Vasomotor center
Vasodilator area - anterolateral portions of LOWER HALF OF MEDULLA
True
True or False:
Vasomotor center
Sensory area - tractus solitarius
True
