Vet 223 Exam 2

SA Node action potentials

If channels → Threshold (-40 mv) → Ca++ Channels → Depolarization → Closure of Ca++ → Opening of K+ channels → Repolarization → Back to -55 mv

Sinus nodal rhytmicity

SA node → both atria → AV node → moves through atrioventricular bundle → Purkinje fibers and conduct the AP rapidly to ventricular myocardium

Speed differences in the AP pathway

AV node = delayed more than 0.1 second

Purkinje fibers = rapid spread

Ventricular muscle - slightly less rapidly

Why are intercalated discs so important? What do they contain?

Each cardiac muscle cell physically contacts neighboring muscle cells at intercalated discs.

Intercalated discs contain gap junctions allow movement of ions between cells and desmosomes (spot welds) to prevent pulling apart during contraction

What is the mnemonic to remember for cardiac AP pathway

Some animals bite his paws - SA node, Atria, Bundle of His, His branches, Purkinje

What ion channels do both cardiac and neuronal cells have?

Voltage-Gated Na+ channels

Voltage-Gated K+ channels

Na+/K+ ATPase

K+ Leak channels

Why do cardiac and neuronal cells have different resting membrane potentials

Cardiac SA node, ventricular muscle, neurons

What Na+ channel difference exists between cardiac and neuronal cells

Neuronal APs use voltage-gated Na+ channels for depolarization

In the SA node, these Na+ channels are mostly inactive

What is the role of voltage-gated Ca2+ channels in cardiac vs neuronal cells

Cardiac - L-Type Ca2+ channels -cause plateau phase in ventricular APs

Cardiac - Help pacemaker cells depolarize - T-Type Ca2+ channels

Neurons - Use Ca2+ channels mainly for neurotransmitter release, not for action potentials

What is unique about “funny current” (If) Na+ channels

Found in cardiac pacemaker cells (SA/AV nodes)

Slowly leak Na+ into the cell

Allows heart to beat without neural input

How does K+ channel function compare in cardiac vs neuronal cells

Both use voltage-gated K+ channels for repolarization

Cardiac K+ channels close more slowly

Neuronal K+ channels close quickly

How do cardiac cells communicate vs neurons

Cardiac - connected by gap junctions (intercalated discs)

Neurons - communicate via synapses

Why do cardiac APs last longer than neuronal APs

Cardiac AP - L-Type Ca2+ channels stay open

Neurons - Fast Na+ depolarization, quick K+ repolarization

How long do cardiac vs neuronal APs last

Cardiac - 200-300 milliseconds

Neuronal - 1-2 milliseconds

Channels in the cardiac muscle

Phase 0 - Depolarization - Voltage gated sodium channels open

Phase 1 - initial repolarization - fast sodium channels close and potassium channels open

Phase 2 - Plateau - voltage gated calcium channels open and potassium channels remain open

Phase 3 - Rapid repolarization - calcium channels close

Phase 4 - Resting Membrane Potential

Depolarization in the cardiac muscle - why does the plateau happen?

Phase 0 - Slower voltage gated calcium channels open - activated fast sodium channels as those in neurons. slow voltage calcium channels. Voltage gated K+ channels activate for repolarization; however, the “slower” Ca++ channels remain opened for a few milliseconds - this causes the plateau

Where does the Ca++ that activates cardiac muscle contraction come from

Extracellular Fluid - enters cells during AP and triggers the release of more calcium from Sarcoplasmic Reticulum - leading to muscle contraction

What are the effects and mechanisms through which the ANS affects cardiac contraction

Parasympathetic stimulation slows cardiac rhythm and conduction → Ach increases permeability of the fiber membranes to potassium ions

Sympathetic stimuluation increases the cardiac rhythm and conduction → Norepinephrine increases permeability of the fiber membrane to sodium and calcium ions

Systemic circulations

Lungs (oxygenated) → pulmonary veins → left atrium → bicuspid valve → left ventricle → aorta semilunar valve → aorta

What is coronary circulation

system of blood vessels that serves the heart muscle - oxygenated blood flows directly into the coronary arteries from the aorta - deoxygenated blood collected by coronary veins and into coronary sinus and into right atrium

When does the cardiac muscle receive nutrients and oxygen

Coronary circulation

Concepts of stroke volume and cardiac output

Stroke volume - how much blood is pumped per beat

Cardiac output - how much blood is pumped per minute - SV * Heart rate

Heart adjusts CO by changing SV or how fast it beats (HR)

Differences between arteries and veins - pressure

Arteries - transport blood under high pressue to tissues

Veins - transport blood from venules back to heart

Is the capillary bed continuously “open”?

No - Blood flow through capitallies is intermittent due to contraction of metarterioles nad precapillary sphincters

Which molecule commonly doesn’t filter through the capillary

Plasma proteins - too large

Which molecules do filter through the capillary

Water, electrolytes, nutrients, waste products, oxygen and CO2

Permeability comparison between the brain and liver capillary beds

Brain - low permeability (small molecules only)

Liver - higher permeability (larger molecules)

Pulmonary circulation

Cranial and caudal vena cava (deoxygenated blood from body) → right atrium → tricuspid valve → right ventricle → pulmonary semilunar valve → pulmonary artery - lungs

Three functions of the lymphatic system

Transports excess interstitial (tissue) fluid back into the bloodstream

Transports absorbed fat from small intestine to the bloodstream

Help provide immunological defenses

Net exchange in the capillary bed forces and what happens when capillary hydrostatic pressure increases, or plasma colloid osmotic pressure decreases

Net exchange = (Capillary hydrostatic pressue + Interstitial colloid osmotic pressure) - (Interstitial fluid hydrostatic pressue + Plasma colloid osmotic pressue)

Arteriolar End - positive pressure = ultrafiltration

Venular End - negative pressure = reabsorption

Increased capillary hydrostatic pressure and decreased plasma colloid osmotic pressure both lead to increased filtration, resulting in potential edema.

How does hemoglobin bind oxygen

Binds more readily in the lungs, with high PO2, high pH, and lower temperature. In tissues, where PO2 is low and ocnditions like increased CO2, lowered pH, and higher temperature prevail, hemoglobin’s affinity for oxygen decreases, promoting oxygen release to cells

Oxygen-hemoglobin (O2-Hb) dissociation curve, left and right shifts

Right shift - Lower affinity for O2, promotes O2 release → low pH, high PCO2, high temperature, high 2,3-BPG

Left shift - Higher affinity for O2, promotes O2 binding→ high pH, low PCO2, low temperature, low 2,3-BPG

Exercise = release of oxygen from hemoglobin, lungs - oxygen binding to hemoglobin

What and why are the left and right shifts caused in Oxygen-hemoglobin (O2-Hb) dissociation curve?

Right - low pH, high CO2, high temperature, high 2,3-BPG (oxygen release)

Left - high pH, low CO2, low temperature, low 2,3-BPG (oxygen binding)

How is CO2 transported in the blood

Dissolved CO2 - 7% - directly dissolved in plasma

Bicarbonate ions (HCO3-) - 70% - CO2 converted into bicarbonate within RBCs and transported in plasma

Carbaminohemoglobin - 23% - bound to hemoglobin

What does carbonic anhydrase do?

Essential for rapid conversion of CO2 into bicarbonate ions in RBCs, allowing CO2 to be efficiently transported in the blood. During respiration in the lungs, the enzyme facilitates the reverse process, ensuring CO2 is released and exhaled

How is most of the CO2 in blood transported

Bicarbonate ions (70%)

Erthropoietin - Where is it secreted? What does it do? When is it secreted?

Secreted by the kidneys

Stimulates the bone marrow to increase the production of RBCs. Accelerates maturation of erythroblasts (immature RBCs) into mature erthroblasts

Secreted in response to low oxygen levels in the blood

Calculation of the different partial pressures of Oxygen at sea level and at very high elevations

Dalton’s law of partial pressures = Partial pressure of gas x = Barometric pressure (atmospheric pressure) x Fractional concentration of gas x

Sea level -

Atmospheric pressure = 760 mm Hg

Fractional concentration of oxygen = 0.21

Water vapor pressure = 47 mm Hg

Partial pressure of oxygen at sea level = (760 - 47) × 0.21 = 160 mm Hg

Mount Everest -

Atmospheric pressure = 260 mm Hg

Fractional concentration of oxygen = 0.21

Water vapor pressure = 47 mm Hg

Partial pressure of oxygen at mount everest = (260 - 47) × 0.21 = 55 mm Hg

How are gases exchanged? What are the different PPs of oxygen in the alveolar air, lung capillaries, interstitial fluid and inside the cell? - remember PP is functionally the same as concentration gradient

Diffusion - higher pressure → lower pressure

Alveolar air - 150 mm Hg

Lung capillaries - 40 mm Hg

Interstitial fluid - 40 mm Hg

Inside the cell - 23 mm Hg

What are platelets

Platelet plug formation - blood coagulation - vasoconstriction - Essential for blood clotting, helping to control bleeding by forming clots and promoting vascular repair

Difference between innate and adaptive immunity

Innate - Body’s first response to pathogens and involves general mechanisms

Adaptive - Developed after pathogen exposure and involves B and T cells

The two phagocytes

Neutrophils - WBCs - first responder to infection. Innate immune response

Macrophages - WBCs (monocytes) - found in tissues throughout body. Innate and adaptive immunity

Characteristics of inflammation

Vasodilation, increased permeability of capillaries, migration of large number of granulocytes and monocytes, clotting and swelling

Macrophage and neutrophil response during inflammation (the four lines of defense)

Tissue macrophages - first line of defense against infection

Neutrophil Invasion - second line of defense

Second macrophage invasion - third line of defense

Increased production - granulocytes and monocytes by bone marrow - fourth line

When do eosinophils and basophils increase in number

Eosinophils - parasitic infections and allergic reactions

Basophils - allergic reactions

Lymphocyte origin, maturation (thymus, lymph nodes) and activation process (Ag presentation by marcophages and Dendritic cells)

Lymphocyte origin - Hemocytoblasts in bone marrow

Maturation process - T-cell Lymphocytes = bone marrow → thymus gland -  for cell-mediated immunity - B-cell lymphocytes = bone marrow - for humoral immunity

Activation process - Requires presentation of antigens by macrophages and dendritic cells using MHC proteins. Allows body to mount a targeted immune response against specific pathogens

Types and main function of each type of T cells

T Helper Cells - Regulate immune system by secreting lymphokines (most abundant)

Cytotoxic T Cells - Directly kill infected, cancerous, or abnormal cells

Regulatory (suppessor) T Cells - Suppress immune response to prevent excessive reactions and maintain immune tolerance

B lymphocyte function

B lymphocytes provide humoral immunity by producing antibodies that target pathogens for destruction by other immune components, such as phagocytes and the complement system

What do B lymphocytes become when they are ready to secrete antibodies?

When B lymphocytes are activated, they enlarge and take on the appearance of lymphoblasts. Some lymphoblasts differentiate into plasmablasts, which become plasma cells. Plasma cells secrete antibodies

Antibody modes of action

Direct attack on invader - agglutination, precipiation, neutralization, and lysis

Activation of the complement system - enhances the actions of antibodies and phagocytic cells to destroy the invader

Where is tolerance to the body’s own tissues created for B and T lymphocytes? How is this tolerance acquired?

Tolerance is created during the preprocessing of T lymphocytes in the thymus and B lymphocytes in the bone marrow. This tolerance is acquired because lymphocytes that are specific to attack the body’s own tissues are destoryed during the preprocessing phase to prevent autoimmunity

From the left ventricle, what “type” of blood goes where?

Oxygenated - body

from the right atria, where does the blood go next

Right ventricle

From the right ventricle, where does the blood go next

Lungs

Deoxygenated blood reaches the lungs from the right ventricle through

Pulmonary artery

oxygenated blood reaches the left atria from the lungs through

pulmonary vein

the heart muscle receives its nutrients and oxygen mostly during

diastole

the brain vasculature has wide intercellular clefts (t/f)

false

what is the consequence of the inadequate reabsorption of ultrafiltrate fluid in the tissues

edema

in general erythrocytes

are bags of hemoglobin

2,3 BPG increases O2 binding in hemoglobin (t/f)

false

increased H+ decrease O2 binding in hemoglobin (t/f)

true

H+ “push” O2 from the heme group of hemoglobin (t/f)

true

CO2 “pushes” O2 from the heme group of hemoglobin (t/f)

true

erthropoietin is produced mainly in the liver (t/f)

false

pluripotent hematopoietic stem cells can be stimulated to produce

any type of blood cell

Left shirt vs right shift

Left = decreased temperature, decreased 2,3-DPG, decreased H+, CO

Right = (reduced affinity), increased temperature, increased 2,3-DPG, increased H+

which cell do you think is the first “primitive” type that eventually gives rise to leukocytes

pluripotent hematopoietic stem cell

which type of immunity is highly specific and has “memory”?

adaptive immunity

the chemicals through which the immune system communicates are called

cytokines

which of these are phagocytes

platelets, lymphocytes, erythrocytes, neutrophils

neutrophils

what type of leukocytes need to be presented antigens with MHC proteins in order to be activated

T lymphocytes

phagocytic cells:

B lymphocytes, cytotoxic T cells, T helper cells, Macrophages

macrophages

regulate almost the entire immune system

Cytotoic T cells, T suppressor cells, T helper cells, macrophages

T helper cells

first line of defense in the tissues

macrophages

Resting potential of SA node

-55 to -60 mV

gap junctions allow movement of

ions

“spot welds” that prvent intercalated discs from pulling apart are called

desmosomes

Cardiac action potential phases

0: depolarization - Na+ influx occurs via fast channels

1: initial repolarization - K+ efflux returns TMP to 0 as Na+ channels close

2: plateau - Ca2+ influx via L-type channels is balanced with K+ efflux from delayed rectifier channels

3: rapid repolarization - Ca2+ channels close and K+ efflux continues returning TMP to resting -90 mV

4: resting membrane - Na+/K+ ATPase pump stabilizes TMR

Blood flow

Inferior and Superior Vena Cava

Right Atrium → Tricuspid valve (right AV)

Right Ventricle

Pulmonary valve

Pulmonary arteries

Pulmonary veins → Left atrium

Mitral valve (left AV)

Left ventricle

Aortic valve

Aorta (to body)

Systole vs diastole

Systole: atria or ventricles EXPEL blood

Diastole: atria or ventricles RECEIVE blood

blood functions

transportation, regulation, protection

blood componenets

45% packed red cells (RBCs), 1% white blood cells (leukocytes), 55% plasma and serum, clear fluid layer at top of centrifuge tube