How are reflexes activated?
- Mechanoreceptors by stretch
2. Chemoreceptors by metabolic products
How does Mild to moderate exercise lead to increased cardia output?
Anticipation of activity —> inhibits vagus nerve to heart and increases sympathetic discharge. —> Increased HR and Contractility —> Increased Heart rate
What is the action of isoproterenol?
- Increaess signal to aquaporin
- Increases contractility of the heart
- Beta agonist Only
How does the preoptic anterior hypothalamus affect CV system?
Temperature center of the heart: Temperature changes alter HR and TPR
How does the Parahypogloassal area of the medulla affect the CV system?
Reciprocally activates Sympathetic and inhibits parasympathetic activity
What nucleus is the first to receive information from baroreceptors?
NTS: Nuceus of the tracts solitarius
What is the effect of the stimulation of NTS?
Inhibits sympathetic nerve outflow to peripheral blood vessels
What are the two locations of baroreceptors, and which are more sensitive?
Aortic
Carotid - More sensitive
How does NE affect Carotid Sinus sensitivity?
Enhances sensitivity; Increase in intravenous pressure produces greater depressor response
What are the two types of cardiopulmonary receptors? How are they activated?
- Type A: Tension activated during systole
2. Type B: Stretch activated during diastole
How to CP receptors modulate BP?
Initiated a reflex which lowers BP by inhibiting vasoconstrictor center in the cerebral medulla:
Inhibits:
- Angiotensin
- Aldosterone
- Vasopressin/ADH
Describe the relationship of change in Heart rate and Blood pressure reflex at different values.
- Inverse relationship btwn HR and BP is most pronounced at intermediate ranges
- At High and low values, HR is constant
What is the Bainbridge reflex?
Heart rate increases when Central venous pressure rises following right heart distention
Ho does the hypothalamus affect cardiovascular ulnar reflexes?
- Hypothalamus is responsible for behavioral and emotional control of CVS
Anterior: DEC BP and Bradycardia
Posterolateral: INC BP and HR
What is Cushing’s Phemomenon?
- Elevation in intracranial pressure caused by brain tumor results in increase in systemic blood pressure
- Ischemic stim of vasomotor regions in medulla
- Helps maintain cerebral blood flow in certain conditions such as expanding intracranial tumors
What are the pulmonary CV reflexes?
Lung Inflation —> Systemic vasodilation and DEC in BP
Lung collapse —> Systemic Vasoconstriction
- Fibers in Vagus nerve and sympathetic nerves
- Stretch receptors which inhibit vasomotor areas
- Magnitude Of depressor response directly related to degree of inflation
What is the response of central chemoreceptors to changes in blood chemistry?
- INC in PCO2 —> Vasoconstriction and INC Preiperal resistance
- DEC in PO2 —> Decrease tonic activity and decrease peripheral resistance
Lowering pH stimulates cerebral areas, ties in pH inhibits them
Where are the peripheral chemoreceptors located? What is their action?
On aortic arch just medial to carotid sinuses.
Stimulate vasoconstrictor regions in response to changes in PO2, PCO2, and pH
What is the primary reflex caused by peripheral chemoreceptors?
Activate medullary vagal center —> DEC HR
What are the secondary reflex responses to chemoreceptors?
Peripheral chemoreceptors —> Respiratory activity —> Hypocapnea + Increased Lungstretch —> Inhibits medullary vagal center
What is Coronary perfusion pressure?
Difference between aortic diastolic pressure and LVEDP
How does Left coronary artery physic pressure differ from Aortic and right coronary artery physic pressure?
- Dramatic downstroke at at end of of Diastole/beginning of systole
- Dramatic upswing after systole
What is Angina Pectoris?
Chest pains associated with myocardial ischemia
What are the most common treatments for Angina Pectoris?
Organic Nitrates —> Metabolized to NO which is a vasodilator
Calcium channel antagonist —> Cause Vasodilation
B-adrenergic antagonists
What is the common suffix for calcium channel blockers?
- dipine
* Think DHP channels
What is Coronary Steal?
Reduced pressure on the narrowed vessel further compromises blood flow to the ischemic myocardium
What is the action of Dipyridamole?
- Vasodilator
- Full dilate normal vessel branches which are parallel to narrowed segments and reduce pressure to occluded vessels
What is counterpulsation?
- Inflatable balloon inserted into thoracic aorta via femoral artery
- Balloon inflated during each ventricular diastole and deflated during systole
- Enhances coronary blood flow by raising diastolic pressure at a time when coronary extravascular resistance is lowest.
Which arteries come together to form the circle of Willis?
- Vertebral arteries come together to form Basilar arteries
- Basilar arteries and internal carotids form circle of Willis
How does innervation differ between pial and parenchyma arteries?
Pial Arteries —> External —> Sup Cervical Ganglion, Sphenopalpatine, and trigeminal nerve
Parenchymal—> Intrinisic —> Cerebral Neurons
What is the rate of cerebral blood flow?
55 ml/min/100g of brain tissue
What are the protective mechanisms for blood flow to the brain?
- Blood brain barrier
- Extrinsic regulation of CV centers
- Intrinsic control of autoregulation of circulation
- Funcitonal hyperemia
What is the effects of angiopoeitin?
- Growth factor
- Stimulates expression of occludins in endothelial cells of pericytes
What are circumventricular organs?
Places of the brain along the 3/4th ventricles where there are fenestrated capillaries and no BBB
What is the area postrema?
Circumventricular area of the brain which induces vomiting - Susceptible to chemotoxic agents
What provides the parasympathetic stimulation to cerebral vessels?
Facial nerve
What local factors adjust cerebral blood flow to metabolic activity?
- pH: Dilates cerebral vessels
- K+
- Adenosine
What is the pressure range for normal cerebral circulation?
60 - 160 mm Hg
What are neural factors which regulate blood flow in the brain?
- Extrinsic innervation: Cervical Sympathetic ganglion accompany carotid and vertebral arteries into cranial cavity and innervates cerebral arteries *Sympathetic exerts MOST PROMINENT effect during pathophysiological conditions
- Glu or Ach: Activate Astrocytes IP3 pathway —> Released K+ —> hyperpolarization —> Vasodilation
How does CO2 regulate cerebral blood flow?
- Increases in PaCO2 —> vasodilation
- Inhalation increases CO2 2X or 7%
- DEC in CO@f rom hyperventilation —> DEC cerebral blood flow
- CO2 works by altering arteriolar resistance by altering perivascular pH
Where’s are arteriovenous anastomoses located and what are their functions?
- Bypass Capillaries
- Palms, fingertips, Toes, Soles, ear, nose, and lips
- Respond to reflexes to regulate blood flow for temperature control
What is characteristic of Sefer exercise on the CV system?
- max 180 BP And SV
- Compensatory chaises start to fail
- Heat loss decreased
- Reduced pH