Cardiovascular Reflexes, Hematology and Hemostasis

parts of the CNS that exert effects on the cardiovascular system

1. cortex

2. hypothalamus

3. cardiovascular brainstem nuclei

where are baroreceptors located?

1. aortic arch

2. carotid sinus

baroreceptors are an _______ mechanism of blood pressure regulation 

acute

_______ firing rate of baroreceptors indicate an elevation in pressure

increased 

function of tonic activity of baroreceptors

allows them to increase or decrease firing frequency

what occurs as a result of chronic elevated baroreceptor firing?

it will eventually be seen as normal, and the cardiovascular brainstem nuclei will readjust their set points 

baroreflex response to increased blood pressure

activation of PNS and withdrawal of SNS

baroreflex response to decreased blood pressure

systemic arterial pressure rises

the baroreflex is a ______ feedback control loop

negative

what cardiac factors are influenced by the baroreflex in an attempt to maintain blood pressure at its set point?

1. heart rate 

2. force of contraction

3. systemic vascular resistance 

4. venous tone

5. stroke volume 

how does the baroreflex affect receptor activation when increased blood pressure is sensed?

1. increased muscarinic activation via PNS

2. decreased beta-adrenergic receptor activation via SNS

3. decreased alpha-adrenergic receptor activation via SNS

what sensory fibers are associated with the baroreflex?

1. aortic arch: vagus X

2. carotid sinus: glossopharyngeal nerve IX

what does the bainbridge reflex sense?

elevated right atrial pressure as a result of volume loading

what effect does the bainbridge reflex produce?

1. reduces “back-load” on heart 

2. increases cardiac output 

3. favors blood moving into arterial circulation 

what type of receptors are associated with the baroreflex and bainbridge reflex?

stretch-sensitive mechanoreceptors

when does the baroreflex dominate?

1. volume depletion lowers systemic blood pressure

2. increased heart rate is triggered 

when does the bainbridge reflex dominate?

1. volume loading increases right atrial pressure

2. increased heart rate is triggered

locations of chemoreceptors

1. aortic body

2. carotid body 

3. medulla  

function of chemoreceptors

monitoring and maintaining oxygen, carbon dioxide, and pH levels of blood

where is information from the chemoreceptor sites carried to?

brainstem nuclei controlling cardiorespiratory function 

what physiological conditions represent inefficient ventilation for the metabolic needs of the systems’ tissues?

1. hypoxemia 

2. hypercapnia

3. acidosis  

what is the result of the chemoreceptor reflex in response to stimulation? 

1. increased respiratory rate

2. increased TPR via peripheral vasoconstriction 

3. increased cardiac output 

how does the chemoreceptor reflex influence the sympathetic and parasympathetic influences?

increased SNS, decreased PNS

renin angiotensin system RAS

1. chronic control of blood pressure 

2. initiated by renal system 

3. hormonal control 

what variables do the renal arterioles sense?

1. increased pressure

2. increased concentrations of solute 

what is renin?

a hormone released from kidneys into the blood when low blood pressure is sensed

what does renin do?

helps convert angiotensinogen into angiotensin I

how does angiotensin I convert to angiotensin II?

angiotensin converting enzyme ACE

angiotensin II functions

1. binds to the nephron to promote sodium and water reabsorption 

2. promotes vasoconstriction at the vessels

3. stimulates release of ADH and aldosterone 

how does angiotensin II affect blood pressure?

elevates it back to normal

ADH is either stimulated ________ or ________ for release

directly, indirectly

mechanisms to stimulate vasopressin or anti-diuretic hormone ADH release

1. direct: hyperosmolarity or significantly reduced blood volume 

2. indirect: release from hypothalamus/pituitary by angiotensin II

two targets of ADh

1. vasoconstriction of peripheral blood vessels 

2. water reabsorption by kidney 

does ADH work to increase or decrease blood pressure?

increase

what is aldosterone ALD?

a hormone stimulated by angiotensin II and released into the blood by the adrenal cortex 

what does aldosterone promote?

sodium retention, and therefore water retention within the kidney

what effect does aldosterone have on blood pressure?

increases blood pressure

what hormone inhibits the release and actions of angiotensin II, ADH, and aldosterone?

atrial natriuretic peptide ANP

what is atrial natriuretic peptide ANP?

1. salt-dumping hormone 

2. released in response to increased atrial stretch from increased blood volume 

what does atrial natriuretic peptide do?

1. inhibits salt and water retention mechanisms

2. increases salt and water excretion by the kidney 

blood represents the ________ component of the ECF compartment

circulating

main components of plasma

1. water

2. ions

3. organic molecules 

4. trace elements and vitamins 

5. gases 

proteins in plasma

1. albumins 

2. globulins 

3. fibrinogen 

4. transferrin

cellular elements of blood

1. red blood cells 

2. white blood cells 

3. platelets 

main types of white blood cells

1. lymphocytes 

2. monocytes 

3. neutrophils 

4. eosinophils 

5. basophils 

albumin 

1. most prevalent plasma protein

2. contributes to oncotic pressure

3. carrier of various substances

globulins

1. clotting factors 

2. enzymes 

3. antibodies 

4. carriers for various substances 

fibrinogen

forms fibrin threads for blood clotting

transferrin

iron transport

what is the source of most plasma proteins?

liver

specialized globulins (like immunoglobulins and antibodies) are synthesized and secreted by specialized…

blood cells

white blood cells represent the only fully ______ cells in the circulation

functional

monocytes in tissue are called…

macrophages

basophils in the tissue are called…

mast cells

phagocytes

1. include neutrophils, monocytes, and macrophages

2. engulf and ingest foreign particles 

lymphocytes

have specific immune responses directed against invaders 

granulocytes

1. include basophils, eosinophils, and neutrophils 

2. have cytoplasmic inclusion making them granular 

bone marrow

soft tissue located in center of hollow bones

pluripotent stem cells 

1. in bone marrow 

2. transition through different cascades of differentiation to determine their fate 

uncommitted stem cells

1. first type of cell in cascade of differentiation

2. 1 of every 100,000 cells in bone marrow 

progenitor cells

1. committed to developing into one or two cell types 

2. can differentiate into RBCs, WBCs, or megakaryocytes 

active vs inactive bone marrow is indicated by…

color

____ percent of developing cells are RBCs, while ____ percent are destined to be WBCs

25, 75

why are fewer developing cells going to be RBCs and more will be WBCs? 

RBCs have a longer lifespan (4 months), while some WBCs only have half lives of around 6 hours 

hematopoiesis

blood cell production

cytokines

1. control hematopoiesis 

2. peptides or proteins released from one cell that affect the activity of another cell 

common cytokines

1. erythropoietin EPO

2. thrombopoietin TPO

3. colony-stimulating factors, interleukins, stem cell factor 

site of production of erythropoietin EPO

kidney

site of production of thrombopoietin TPO

liver

site of production of colony-stimulating factors, interleukins, and stem cell factor

endothelium and fibroblasts of bone marrow, and leukocytes 

erythropoietin EPO influences growth or differentiation of…

red blood cells

thrombopoietin TPO influences growth or differentiation of…

megakaryocytes

what triggers release of erythropoietin EPO?

hypoxia (low oxygen levels)

what is the goal of erythropoietin EPO?

increase hemoglobin in circulation to carry oxygen

what does erythropoietin EPO convert?

erythroblasts into erythrocytes

erythroblasts

large and nucleated cells in bone barrow that give rise to red blood cells 

as erythroblasts mature they lose their…

nucleus and membranous organelles

reticulocyte

immature form of red blood cell that leaves the bone marrow and enters circulation 

what helps form the unique biconcave disk shape of RBCs?

cytoskeleton

crenation RBCs

shrunken in hypertonic solution with a spiky surface due to rigid cytoskeleton

hemoglobin structure 

1. 4 globular chains each with a heme group

2. 2 alpha and 2 beta chains 

3. bind up to 4 oxygen molecules

heme group structure

1. porphyrin ring 

2. iron atom in center 

ferritin

what the liver stores excess iron as

how does the bone marrow acquire iron?

transferrin protein in plasma transports iron

where is hemoglobin made?

bone marrow

how are old red blood cells destroyed? 

1. the spleen converts hemoglobin to bilirubin 

2. bilirubin and metabolites are excreted

3. liver = metabolites in feces 

4. kidney = bilirubin in urine 

main causes of anemia: RBC loss

1. blood loss

2. hemolytic anemias 

3. defective RBC or hemoglobin synthesis in bone marrow 

4. inadequate production of erythropoietin 

inactive platelet morphology

small and disk-like

activated platelet morphology

spiky outer surface and adhere to each other

how are platelets formed?

edges of megakaryocytes break off to form cell fragments called platelets

hemostasis

process of keeping blood within a damaged blood vessel

main methods to uphold hemostasis

1. vasoconstriction 

2. platelet plug

3. coagulation

platelet plug formation steps

1. exposed collagen binds and activates platelets

2. release of platelet factors 

3. factors attract more platelets 

4. platelets aggregate into plug 

what prevents platelet plug formation?

intact endothelium releases prostacyclin and nitric oxide to prevent platelet adhesion

coagulation converts a platelet plug into a ______

clot

intrinsic pathway of the coagulation cascade

uses proteins already in plasma to begin cascade

extrinsic pathway of the coagulation cascade

starts when damaged tissues expose tissue factor

both the intrinsic and extrinsic pathways of the coagulation cascade feed into the…

common pathway, which allows for insoluble fibrin polymers to become part of the clot 

common pathway of coagulation cascade

1. prothrombin is cleaved into thrombin 

2. fibrinogen in the plasma is converted to fibrin 

3. fibrin forms cross-linked fibrin polymers

plasmin 

enzyme that breaks down fibrin to disintegrate a clot