B4: Cell Bio Exam 1

right

(right/left) heart propels blood into the pulmonary system

left

(right/left) heart propels blood into systemic circulation

arterioles

What vasculature provides resistance to blood flow?

on exam!!

heart and lungs

What are the only two organs to receive 100% of cardiac output?

true

T/F: the heart has an absolute requirement for aerobic production of ATP to maintain adequate ATP concentrations because anaerobic capacity is limited in the heart

increase

When heart rate and contractility is increased, myocardial metabolism will (increase/decrease)

oxygen

The heart requires ____________ for ATP production

true

T/F: oxidative phosphorylation requires oxygen

fatty acids

What energy source is preferred for the heart?

hypoxic

Under ________ conditions, glycogen is metabolized ultimately to lactate and cellular ATP levels decrease

lactate

What energy source is important during exercise (anaerobic conditions) which can then make pyruvate --> acetyl-CoA --> 18 ATP?

red blood cells

What primarily produces lactate?

Hint: they do not have mitochondria, thus cannot process acetyl-CoA

lactate dehydrogenase

What converts pyruvate to lactate and lactate back to pyruvate?

on exam!!

18

How many ATP does pyruvate produce?

on exam!!!

2

How many ATP does lactate produce?

on exam!!!

30

How many ATP does glucose (carbohydrate oxidation) produce?

on exam!!!

a.

What energy source provides the highest amount of ATP?

a. fatty acids

b. pyruvate

c. glucose

d. ketones

true

T/F: the heart has low anaerobic capacity and has a high dependence on oxygen delivery

fatty acid beta oxidation

What process provides 60-90% of energy to the heart, requires more oxygen, and produce large amounts of ATP?

glucose oxidation

What process provides 20-40% of energy to the heart, is an oxygen efficient pathway, and produces a modest amount of ATP?

lactate

What fuel source is used by the heart during exercise, converted to pyruvate via lactate dehydrogenase, and produces a modest amount of ATP?

true

T/F: 98% of cardiac ATP is generated via oxidation

lactate

What is the preferred fuel source for the heart during exercise?

true

T/F: diet and activity level influence which substrate is primarily utilized by the heart

fatty acids

What substrate is primarily used by the heart following an overnight fast?

glucose

What substrate is primarily used by the heart following a high carbohydrate meal?

lactate

What substrate is primarily used by the heart during exercise?

ketone bodies

What is fuel substrate for the heart and brain that is formed from fatty acids during fasting or starvation?

true

T/F: heart prefers fatty acids over ketone bodie

insulin

What stimulates increased GLUT4 transporter expression?

on exam!!

insulin

Adipose, skeletal, and heart muscles all respond to _________ by inserting GLUT4 into the membrane surface, thereby increasing glucose uptake

on exam!!

increase

When the heart is in hypoxic conditions and undergoes ischemia, there is a(n) (increase/decrease) in GLUT4 transporter expression

on exam!!

a.

(slow/fast) twitch skeletal muscle

-oxidative aerobic pathways predominant

-fatigue resistant (e.g., sustained energy production)

-high capillary density (to get more supplies to muscle and rid of waste)

-many mitochondria

-small diameter (minimal glycogen storage)

on exam!!

a. slow

b. fast

fast

(slow/fast) twitch skeletal muscle

-glycolytic, anaerobic pathways predominate

-easily fatigued (e.g., rapid energy utilization)

-low capillary density

-few mitochondria

-large diameter (large amounts of oxygen)

on exam!!

ketone bodies

What substrate for metabolism is formed in the liver from fatty acids to be used as an alternate (non-carb) energy source?

Hint: acetoacetate and beta-hydroxybutyrate

carbohydrates

When ___________ are low (e.g., during fasting or starvation), ketone production increases

ketoacidosis

Untreated, type I diabetics develop _______________ (e.g., high ketones in serum) due to lack of insulin inhibiting glucose uptake causing blood pH to decrease and increase hyperventilation

ischemia

What impairs the aerobic production of ATP?

coronary artery disease

What disease reduces blood flow (and, therefore, oxygen delivery) to affected cardiac tissue and can cause angina pectoris (chest pain) from lactate build up causing lactic acidosis?

glycolysis

When oxygen is not available, what is the only means of ATP production for the heart?

Hint: No route for pyruvate consumption, so pyruvate converted to lactate

No oxygen --> ETC backed up --> TCA backed up --> pyruvate dehydrogenase can’t convert pyruvate to acetyl CoA --> LDH will reduce pyruvate to lactate, producing 1 NAD+, which helps to keep glycolysis going

cAMP

What is a huge cellular signal that energy is desperately needed and is converted to adenosine which will leave the cardiac myocyte and cause coronary vasodilation?

Hint: converted from ADP using adenylate kinase

adenosine

What is produced from cAMP and causes coronary vasodilation?

myocardial infarction

What disorder reduces blood flow to zero in the affected regions of the heart, causing cardiac muscle tissue to potentially die if not reversed within 20-40 minutes?

brain

The heart can use ketone bodies as an energy source, but prefers fatty acids, thereby leaving ketone bodies for the ______

pyruvate dehydrogenase

What enzyme converts pyruvate into acetyl-CoA?

ketosis

_________ results from the restriction of carbohydrates in the diet (e.g., when partaking in the ketogenic diet) and produces acetone/chemical/"fruity smelling" breath

myocaridum

What tissue in the heart has a striated appearance due an ordered arrangement of contractile filaments, is single or binucleated, has a high density of mitochondria, and is terminally differentiated (amitotic)?

on exam!!!

gap junctions

What connection between myocytes is an electrical connection that allows for electrical synapses and facilitated action potential propagation?

on exam!!

desmosome and fascia adherens

What connection between myocytes are mechanical connections?

on exam!!

intercalated disks

What are located at either end of a cardiomyocyte, physically connect adjacent cardiomyocytes, and electrically couples the cells via gap junctions?

true

T/F: cardiomyocytes have electrical and mechanical syncytium

true

T/F: the heart has more connective tissue than skeletal muscle

T-tubules

What part of the cardiomyocyte runs down the Z-linke and form a dyad with the terminal cisterna?

0.1 mM

What is the concentration of calcium at REST in the sarcoplasmic reticulum (SR) in a cardiomyocyte?

on exam!!

0.0001 mM

What is the concentration of calcium at REST in the cytoplasm in a cardiomyocyte?

on exam!!

1-2 mM

What is the concentration of calcium at REST in the T-Tubule of a cardiomyocyte?

on exam!!

L-type

What type of voltage gated calcium channel are the dihydropyridine receptors?

dihydropyridine receptors

What is a voltage-gated L-type Calcium channel that is the target for calcium channel blockers?

1. Wave of depolarization

2. Dihydropyridine receptors open

3. Ca2+ influx

4. Ca2+ sensitizes ryanodine receptor (RyR) on SR

5. Calcium-induced calcium release (CICR)

6. CICR = [Ca2+]i increases from 0.0001 mM to about 0.1 mM

7. Binding of Ca2+ to TnC: conformational change allows myosin binding sites to be exposed on F-actin and shifting of TnI out of the way

8. Myosin heads (bound to ADP and Pi) interact with F-actin to form cross-bridges

10. Pi is released and conformational change converts potential energy to kinetic energy to induce power stroke; pulls actin forward and ADP is released

Describe the process of excitation-contraction coupling in a cardiomyocyte.

on exam!!

tropomyosin

What covers myosin attachment sites on F-actin?

troponin

What consists of 3 proteins, regulates tropomyosin confirmation, and is the site of binding for calcium?

TnT

What subtype of troponin fixes troponin group to tropomyosin?

TnI

What subtype of troponin prevents ATPase activity when bound to actin?

(think: TnInhibit)

TnC

What subtype of troponin is sensitive to Calcium and binds up to 4 molecules (but only requires a minimum of 1) to activate?

(think: TnCalcium)

tetanus

In skeletal muscle, rapid succession of action potentials can lead to an additive effect on muscle contraction known as _________, a single substantial and prolonged contraction event

true

T/F: cardiac muscle is unable to be activated frequently enough to induce tetany because it is absolutely necessary to allow appropriate time for filling (to preserve stroke volume, end-diastolic volume, and ejection fraction)

contraction

The time of a heart ________ is about the same as its action potential (e.g., there is a long refractory period because the refractory period cannot end until the mechanical action is completed)

end-diastolic volume

What is the volume of blood in a given heart chamber at the end of diastole (relaxation)?

low

If EDV is too ____, less volume will be ejected during systole (contraction)

preserve stroke volume

What is the volume of blood ejected during systole into the ascending aorta?

Hint: also known as cardiac output

ejection fraction

What is stroke volume divided by end-diastolic volume?

1. Ca2+ is resequestered into the SR by the ‘Sarcoplasmic Reticulum Calcium ATPase’ (SERCA).

2. SERCA activity is regulated by phospholamban.

3. Once in the SR, Ca2+ is bound by sequestration chaperone proteins that prevents leakage:

Calsequestrin

Calreticulin

4. Some Ca2+ exported from the cytoplasm to the extracellular milieu though 3Na+-1Ca2+ exchangers and a sarcolemmal Ca2+ ATPases.

5. [Ca2+]i falls back to ~0.0001 mM.

5. Another ATP binds the myosin head; myosin releases from actin.

6. Myosin head has intrinsic ATPase hydrolytic capacity; ATP à ADP + Pi; myosin head releases actin and stores potential energy from broken bond for another power stroke; remains in a ‘cocked’ or ‘trigger’ state in the resting conformation.

Describe the process of muscle relaxation after excitation-contraction coupling.

true

T/F: relaxation (the cessation of contraction and return to resting state) of the heart is dependent on calcium

lusitropy

What is the rate of myocardial relaxation?

on exam!!

positive

(positive/negative) lusitropic agents increase myocardial relaxation

on exam!!

negative

(positive/negative) lusitropic agents decrease myocardial relaxation

on exam!!

isometric

When a muscle is ___________ it is at a fixed LENGTH, tension will increase but the length of the muscle tays the same

Lmax

What is the maximum length of a muscle (no cross-bridge interaction between actin-myosin) before the muscle is ruptured?

resting tension

What is the force required to stretch a muscle to its max length?

active tension

What describes a muscle being stimulated to contract while the length is held constant?

Hint: this occur when you are doing a bench press and you cannot lift the bar up -- your muscles are not lengthening/shortening yet are contracted to hold the bar up!

a.

When muscles are in an (isometric/isotonic) state, potential energy INCREASES but kinetic energy decreases

a. isometric

b. isotonic

b.

When muscles are in an (isometric/isotonic) state, kinetic energy INCREASES but potential energy decreases

a. isometric

b. isotonic

isotonic

When a muscle is ___________, it is in a fixed tone/tense state -- the tension stays the same but the length of the muscle changes

Vmax

A muscle will shorten at _______, the max possible velocity of muscle shortening that is determined by max possible rate of cross bridge cycling

preload

What is the load on the muscle at rest that increases potential energy (velocity of shortening is increased by Vmax is unchaged)?

on exam!!

a.

A(n) (increase/decrease) in preload will increase the maximal force of contraction

on exam!!

a. increase

b. decrease

a.

A(n) (increase/decrease) in preload will increase the potential energy for increased force of contraction

on exam!!

a. increase

b. decrease

afterload

What occurs when the load on the muscle at rest and the load on the muscle during contraction are different (e.g., the force that the ventricle must overcome to achieve systolic ejection)?

on exam!!

a.

An (increase/decrease) in afterload decreases the capacity to shorten and contract

on exam!!!

a. increase

b. decrease

true

T/F: greater resting tension will cause greater active tension

true

T/F: active tension is greatly affected by the resting tension of the muscle

optimal length

The actin-myosin overlap that affords the most cross-bridging with room to accommodate the power stroke, which will generate the greatest force of contraction or __________

To allow for greater preload, or greater filling of the heart from venous return; greater stretch without negating actin-myosin overlap

Why is the optimal length (Lo) of cardiac muscle slightly lower than that of skeletal muscle?

on exam!!!

a.

If cardiac filling increases (e.g., increased preload), end-diastolic volume (increases/decreases)

a. increases

b. decreases

a.

If end-diastolic volume increases, then resting tension (increases/decreases)

a. increases

b. decreases

increase

If resting tension increases (e.g., greater stretch/passive tension), then the force of contraction will (increase/decrease)

a.

If the force of contraction increases, then the stroke volume (and thus cardiac output) will (increase/decrease) in proportion

a. increase

b. decrease

end-diastolic volume

What is the volume in the ventricle after filling and prior to ejection?

end-systolic volume

What is the volume in the ventricle following ejection and before diastole?

stroke volume

What is the volume ejected from the ventricle during systole?