Cardio Lecture 5 (ch17)

each tissue controls its own blood flow in proportion to its needs

• tissue needs:
• 1. delivery of O₂ to tissues
• 2. delilvery of nutrients such as glucose, amino acids, ect
• 3. removals of CO_{2 ,} H and other metabolites from the tissues
• 4. Transport various hormones and other substances to different tissues

increase in blood flow

increases tissue blood flow

• 1. the pressure difference (ΔP) between 2 ends of the vessel
• 2. resistance (R) of the vessel

ability of a tissue to maintain blood flow relatively constant over a wide range of arterial pressure

as arterial pressure is decrease, O₂ or nutrient delivery is decreased resulting in a release of a vasodilator

as arterial pressure falls the arterioles have an intrinsic property to dilate in response to decreases in wall tensions

Tension = Pressure x radius

• occurs by changing the degree of vascularity of tissues (size and number of vessels)
• oxygen is an important stimulus for regulating tissue vascularity

• the growth of new blood vessels
• occurs in response to angiogenic factors

• 1. ischemic tissues
• 2. rapidly growing tissue (embryology)
• 3. tissue with high metabolic rates (ovary, cancer)
• most are small peptides 
• VEGF: vascular endothelial cell growth factors
• FGF: fibroblast growth factor
• angiogen

• NE and EPI
• angiotensin
• vasopressin
• endothelin

• bradykinin
• serotonin
• histamine
• prostaglandins
• nitric oxide

• Catecholamine, non-peptide NT, that are secreted by the adrenal medulla
• bind to α and β GPCR andwork through   second messengers  (Gs- cAMP) affecting K and Ca

• important in kidney control of BP
• peptide hormone more potent then NE/ Epi
• mainly acts on the arterioles to increase total peripheral resistance
• AT1 and AT2 receptors
• activate PLC IP₃ / DAG

cleaves angiotensiogen into angiotensin I

• angiotensin converting enzyme
• converts Angiotensin I to II

• vasoconstrictor 
• Acts on Adrenal Cortex, Pituitary, Cardiac and Vascular hypertrophy, systemic vasoconstriction
• increased blood volume 
• renal sodium and fluid retention

• vasocontrictor 
• ADH: anti-diuretic hormone
• formed from nerve cells of hypothalamus 
• secreted by posterior pituitary gland into blood
• increases water reabsorption in the kidneys

• vasodilator
• 5HT₂
• important in localized vasoconstriction
• dilated cardiac blood vessels
• secreted by platelets
• Increases PLC, increase IP3, and increases intracellular calcium
• involved in wound healing

• vasodilator
• occurs in every tissue
• released by immune cells in respinse to damage, allergy, and inflammation
• Gs

• vasodilator
• released from healthy, endothelial cells
• acts locally on vascular SM cells
• cGTP converted to cGMP by guanylate cyclase enzyme to cause local SM relaxation