Bio 163

• Brain center: 
• contain interneurons that initiate visceral motor responses

• Cardiovascular center: 
• Cardiac control (heart), cardioacceleratory  neurons (interneurons will lead to a increase in HR) , cardioinhibitory neurons (interneurons will lead to a decrease in HR) 
• Vasomotor control (vessels)
• Together cardiac control and vasomotor control regulate blood pressure and heart function

• Sympathetic system
• Cardioacceleratory 
• Visceral motor 
• Vasoconstriction 
• Occurs when BP is to low — Increase HR
• Adrenergic receptors bind norepinephrine (NE) — increases rate of AP of SA node 

• Parasympathetic system
• When baroceptors are high PS is activated and cardioacceleratory would be inhibited 
• Cardioinhibitory
• Visceral motor
• Vasodilation 
• Occurs when BP is to high — Decrease HR
• Cholinergic receptors bind ACh — allows potassium to leave the cell (makes cell more negative) rate of AP decreases

• Afferent 
• Sensory input is integrated to create motor output to SA node

• (sensory input from muscles and tendons) 
• Informs brain on changes in physical activity

• (sensory input from blood vessels)
• Informs brain on changes to pressure in vessels

• (sensory input from blood vessel)
• Informs brain on changes carbon dioxide or oxygen levels in the blood
• Important in respiratory system, but has some effect on heart rate

• similar to membrane
• consists of one-layer of epithelial cells (endothelial cells) and thin layer of connective tissue (subendothelial layer and elastic fibers)
• endothelium is a selectively permeable barrier
• cells regulate what enters/exits bloodstream
• smooth surface normally repels bloods cells and platelets
• during damage, platelets and leukocytes (white blood cells) adhere to surface  plaque clogged vessels

• Smooth muscle layer 
• Elastic fiber membrane (in arteries only) — consists of collagen 
• Smooth muscle controls vasomotion — especially in arteries

• Outermost layer
• Connective tissue with collagen and elastic fibers
• Generally thicker in veins
• Anchor vessel to surrounding tissues
• Vasa vasorum – vessels of the vessels

elastic, muscular and arterioles

Veins (low pressure): venules (smallest veins), small veins, large veins

• Thick walled, close to heart
• Largest diameterMore elastin than in any other vessel; elastic fibers in all 3 layers
• Do not vasoconstrict, low resistance pathways 
• Act as pressure reservoirs (expand & recoil as heart ejects blood) 
• Blood flows fairly continuously instead of starting & stopping with pulsating rhythm of heart beat 
• Feed into Muscular arteries

• Deliver blood to specific body organs 
• More muscle in tunica media — responsible for vasoconstriction

• Smallest diameter artery 
• Smallest arterioles feed into capillary beds
• Vasomotion control blood flow into capillary beds 
• Blood within arterioles face high resistance — also called resistance vessels

connect arteriole and venules — site of exchange between blood and tissues

If arterial walls weaken in the wall of a BV an aneurysm can occur which is a balloon-like bulge, can be hereditary or acquired or both

• Scurvy: lack of vitamin C in diet disrupts proper production of collagen
• Scurvy results in weakened BV, spontaneous bruising, swollen gums, loss of teeth

• Vasoconstriction: narrowing of blood vessels 
• Vasodilation: widening of blood vessels

• Continuous
• Most common (abundant in skin, muscle, lungs, CNS)
• Least permeable 
• Wall of vessel is a single endothelial cell thick
• Cells overlap to make intercellular clefts where some molecules can travel through via diffusion

• Fenestrated 
• Have pores in endothelial cells that increase permeability 
• Found in areas of active filtration (kidney) or absorption (small intestine) 

• Sinusoidal 
• Most permeable, least regulated
• Incomplete basement membrane 
• Found in liver, spleen

• Vasoconstriction means decreased blood flow
• Vasodilation means increased blood flow

• Gases and nutrients pass between the blood and interstitial fluid via diffusion at capillaries 
• 2 major routes:
• —through a cell
• —through spaces between cells

Alternative blood routes to bypass a capillary or several vessels that lead to the same location

• Cells (formed elements, 45%)
• Red (gas transport), white blood cells (immunity), platelets (clotting)

• Plasma (55%)
• Water, proteins, nutrients, electrolytes (sodium), wastes Proteins:
• —Albumin: water balance (helps maintain osmosis INTO the blood)
• —Fibrinogen: clotting

• Hemostasis: prevent bleeding 
• Coagulation: formation of a clot

Vascular spasm — smooth muscle contracts causing vasoconstriction

Platelet plug formation — exposed collagen attract platelets, binding to collagen also causes platelets to secrete chemicals that attract more platelets

Coagulation — fibrin creates a mesh of proteins that trap RBCs and platelets, forming a clot. The clot is eventually dissolved as endothelial cell regrow

• Major goal — get oxygen and nutrient to the baby’s brain and rest of body 
• Pulmonary and digestive systems are not yet functional — lungs are still collapsed and fluid filled 
• Fetus receives oxygen and nutrients from mother’s placenta via diffusion

Diffusion of wastes, oxygen and nutrients

Returns oxygenated blood to fetus

Deoxygenated blood leaves fetus via the umbilical arteries

Umbilical vein

• Connects Umbilical vein to IVC
• Allows oxygenated blood from the placenta to bypass the liver

• Connect RA with LA
• Before birth the foramen ovale allows blood flow to bypass the lungs

• Connect pulmonary artery with aorta
• If fails — right side of heart will fail

• Placenta
• Umbilical vein
• To ductus venosus
• IVC
• Heart (liver is skipped)

• Placental
• Umbilical vein
• Portal sinus
• Liver
• Portal vein
• Heart (provide oxygen to liver)

70% of blood to RV then PA

At PA 90% of blood enters ductus arteriosus and is shunted you aorta

Or

Other 30% of blood is shunted to left atrium via foramen ovale

• SP: pressure during ventricle contraction (pressure heart exerts)
• DP: pressure during ventricle relaxation (pressure in arteries b/t beats)

Mean arterial pressure

average pressure in vessels

• Cardiac ouput
• Resistance of vessels 
• blood volume

• Amount of blood the heart pumps per minute into arteries 
• higher output — more blood in arteries — higher pressure (sympathetic)
• lower output — less blood in arteries — lower pressure (parasympathetic

Vasomotion — vessel diameter can change

• Total volume of blood in the vessels
• Regulated by lymphatic system, kidneys and hormones

• Intracellular — water in cells 
• Extracellular
• — interstitial fluid: water b/t cells of tissue 
• — plasma: water in blood vessels 
• — other: water in lymph vessels

• Hydrostatic: physical force resulting in net movement of fluid in one direction — pushes 
• Osmotic pressure: chemical forces resulting in net movement of water in one direction — pulls water to lower concentration

Net pressure out of bed

• Diffusion of water across a membrane 
• high concentration to low concentration 
• dilute solute to concentrated solute

Net pressure into bed

(Hydrostatic pressure in C - Hydrostatic pressure in IF) - (Osmotic pressure in C - Osmotic pressure in IF)

Interstitial fluid at the capillaries enters lymphatic capillaries, is filtered by white blood cells in lymph nodes and transported back to the blood stream at the left and right subclavian veins

3 layers of CT that hold kidneys in place 

• Fibrous capsule: 
• innermost layer
• Dense irregular tissue

• Perinephric fat capsule
• Middle layer
• Loose connective (adipose) tissue

• Renal fascia
• Outer layer
• Dense irregular  connective tissue anchors kidney to surrounding\
• structures