Aorta

 The aorta holds the distinction of being the largest artery in the human body. Its significance lies in serving as the initial pathway for blood leaving the heart and distributing it to various organs through smaller, branching arteries. Without the aorta, our body’s tissues wouldn’t receive the vital oxygen and nutrients they need 1. Let’s delve into more details about this remarkable vessel:

• Anatomy of the Aorta:

  • The aorta starts at the left ventricle of the heart, where it receives oxygenated blood.
  • It then arches upward toward the neck (forming the aortic arch), before curving back downward and extending into the abdomen.
  • Structurally, the aorta is a big tube-like structure, typically about 1 inch wide in diameter. However, its size can vary based on an individual’s height and weight.
  • The aorta is widest at its connection to the heart’s left ventricle through the aortic valve. As it descends into the abdomen, it gradually narrows.

• Four Parts of the Aorta:

  1. Ascending Aorta:
     • The first part of the aorta, connected to the left ventricle.
     • Originates at the aortic valve, which regulates blood flow from the heart into the aorta.
  2. Aortic Arch:
     • Curves upward toward the head and neck.
     • Begins where the ascending aorta ends.
  3. Descending Aorta:
     • Travels downward from the aortic arch through the chest.
     • Also known as the descending thoracic aorta.
  4. Abdominal Aorta:
     • The final part of the aorta.
     • Starts at the diaphragm and ends where it splits into the two iliac arteries that extend into the legs.

• Layers of the Aorta Wall:

  • The aorta has three layers in its wall:
    1. Tunica Intima: The innermost layer, providing a smooth surface for blood flow. Composed of endothelial cells and supporting tissue.
    2. Tunica Media: The middle layer, consisting of smooth muscle, elastic tissue, and collagen.
    3. Tunica Adventitia: The outer layer made of connective tissue (collagen) and a network of small blood vessels (vasa vasorum) that nourish the aorta.

• Variations and Anomalies:

  • In some conditions (such as dextrocardia or situs invertus), the aorta may be on the right side instead of the left.
  • Coarctation of the aorta is a birth defect where a part of the aorta is significantly narrower than usual.

In summary, the aorta’s essential role as the largest artery ensures efficient oxygen and nutrient distribution throughout our body, making it a vital conduit for life-sustaining blood flow 234. If you have more questions or need further information, feel free to ask! 😊

lab exit

What Is Aortic Stenosis? Your aortic valve keeps blood flowing from your heart's lower left chamber (left ventricle) to the aorta which is the main artery bringing blood from the heart to the body. Aortic stenosis occurs when the aortic valve narrows and blood cannot flow normally.

regurgitation?

Mitral valve regurgitation is a problem that occurs when there is a valve leak, leading to blood flowing back into the left atrium. The incomplete valve closure may produce a softer S1 sound. Symptoms that may arise in people with this valve problem include: dizziness.

 

check in question week 7

 

tetrodotoxin TXX blocks voltage gated sodium channel which part of action potential graph is affected by TXX discuss the activation and inactivation status of channel the key channel involved and the refractory period

 Tetrodotoxin (TTX) is a potent neurotoxin that specifically targets voltage-gated sodium channels. Let’s explore how TTX affects the different phases of the action potential graph:

Activation and Inactivation of Sodium Channels:

Voltage-gated sodium channels play a crucial role in generating action potentials.

These channels have two main states: closed (resting state) and open (activated state).

When a neuron is at rest, sodium channels are predominantly in the closed state.

Upon depolarization (due to an incoming stimulus), some sodium channels open, allowing sodium ions (Na⁺) to flow into the cell. This is the activation phase.

However, sodium channels also have an inactivation gate that can close the channel shortly after it opens. This prevents continuous sodium influx.

Tetrodotoxin’s Mechanism of Action:

TTX binds to the extracellular pore opening of voltage-gated sodium channels.

By binding to site 1 of the sodium channel, TTX temporarily disables the channel’s function.

Specifically, it prevents the passage of sodium ions into the neuron during the rising phase of an action potential.

As a result, the nervous system cannot transmit messages effectively, leading to muscle paralysis.

Key Channel Involved:

The primary sodium channel affected by TTX is the fast voltage-gated sodium channel.

These channels are responsible for the rapid depolarization phase of the action potential.

Refractory Period:

The refractory period is a critical aspect of action potentials.

After an action potential, sodium channels enter a refractory state:

Absolute refractory period: During this phase, sodium channels are completely closed and cannot be activated, regardless of the stimulus.

Relative refractory period: In this phase, some sodium channels have recovered from inactivation, but the membrane potential is still below the resting level. A stronger stimulus can trigger another action potential.

TTX prolongs the refractory period by preventing sodium channels from reopening promptly.

In summary, TTX disrupts the normal function of sodium channels, leading to the inhibition of action potentials and muscle paralysis. Its selective blocking action makes it a valuable tool for studying neuronal excitability and pain pathways12. 🧪🔬

If you have more questions or need further clarification, feel free to ask! 😊

what is the concentration gradient for the ion at the resting membrane potential what happen ion flow once the drug added and how the drug change the memembrane potential

 what is the concentration gradient for the ion at the resting membrane potential what happen ion flow once the drug added and how the drug change the memembrane potential

Copilot

Certainly! Let’s break down the impact of a drug on the resting membrane potential (RMP) and how it affects ion flow.

Concentration Gradient at RMP:

At the resting membrane potential, there is a concentration gradient for both sodium ions (Na⁺) and potassium ions (K⁺).

Inside the cell, the concentration of potassium ions is higher than outside, while the concentration of sodium ions is higher outside the cell.

This concentration gradient is maintained by the sodium-potassium pump and leak channels.

Ion Flow Once the Drug Is Added:

When a drug is introduced, it can alter the permeability of the cell membrane to specific ions.

Let’s consider a hypothetical drug that selectively increases the permeability of sodium ions (Na⁺) through the membrane.

Impact of the Drug on Membrane Potential:

If the drug enhances sodium ion permeability, more sodium ions will flow into the cell.

This influx of positive charges will depolarize the cell membrane (make it less negative).

As a result, the resting membrane potential will shift toward a less negative value (e.g., from -70 mV to a less negative value).

Overall Effect:

The drug disrupts the balance between sodium and potassium ions, altering the resting membrane potential.

Depending on the drug’s mechanism, it could lead to hyperpolarization (more negative potential) or depolarization (less negative potential).

Remember that the specific effects of a drug depend on its properties and the type of ion channels it interacts with. Real-world drugs can have complex interactions, affecting various ion channels and receptors.

If you have any further questions or need additional details, feel free to ask! 🧪🔬

explain how each of the choices selected above RMP K leack channel and sodium and potassium pump and concentration gradient and membrane permeablity why RMP is -70

 

the factors that contribute to the resting membrane potential (RMP) of a neuron and why it is typically around -70 mV.

Leak Channels:

Neurons have leak channels (also known as non-gated channels) that allow ions (such as potassium and sodium) to passively move across the cell membrane.

These channels are always open and contribute to the resting membrane potential.

The most important leak channel for RMP is the potassium leak channel (K⁺ channel). It allows potassium ions (K⁺) to move out of the cell, making the inside of the cell more negative.

Sodium-Potassium Pump (Na⁺/K⁺ Pump):

The sodium-potassium pump actively transports sodium ions (Na⁺) out of the cell and potassium ions (K⁺) into the cell.

For every three sodium ions pumped out, two potassium ions are pumped in.

This pump helps maintain the concentration gradients of sodium and potassium across the cell membrane, which is crucial for RMP.

Concentration Gradient:

The concentration gradient refers to the difference in ion concentrations between the inside and outside of the cell.

At rest, there is a higher concentration of potassium ions (K⁺) inside the cell and a higher concentration of sodium ions (Na⁺) outside the cell.

The potassium leak channel allows potassium ions to move out of the cell along their concentration gradient, contributing to the negative RMP.

Membrane Permeability:

The permeability of the cell membrane to different ions affects RMP.

The cell membrane is more permeable to potassium ions (K⁺) due to the abundance of potassium leak channels.

Sodium ions (Na⁺) have fewer leak channels, so their contribution to RMP is smaller.

Now, let’s tie it all together:

The potassium leak channel allows potassium ions to leak out of the cell, making the inside more negative.

The sodium-potassium pump maintains the concentration gradients by actively pumping sodium out and potassium in.

The net effect of these processes results in an RMP of approximately -70 mV.

Remember that RMP can vary slightly depending on the specific type of neuron and its environment, but -70 mV is a common value. 

If you have any more questions or need further clarification, feel free to ask! 😊

 The first heart sound "lubb" (or S1) corresponds to AV valves closing. The second heart sound "dubb" (or S2) corresponds to the closing of semilunar valves closing.

 

The closing of these valves are so forceful that you can hear these when you are listening to heart beats of a person/patient and this is what we refer to when we are listening to someones heart beat!

Answer 1:

AV

 

Answer 2:

semilunar

 

The Cardiac Cycle, Animation

Cardiac Cycle | Wiggers Diagram | Part 5 | Summary | Cardiac Physiology

Muscle Contraction - Cross Bridge Cycle, Animation.

Lecture 6: Cardiac Cycle Conduction Friday 5/17

 Lecture 6: Cardiac Cycle Conduction

Friday 5/17

Pre-Class SlidesDownload Pre-Class Slides

Take notes with me using this handoutDownload Take notes with me using this handout

Lecture 6 (5/17) Exit Ticket (opens when I open it during class!)

Post-class slidesDownload Post-class slides

RecordingLinks to an external site.

This is actually a really nice summary of the whole cardiovascular section we'll cover over the next few weeks. For pre-nursing folks, this is actually put together for their Associate degree in nursing (so this stuff is quite relevant!). I'll leave this here in case folks like a one-stop resource of helpful diagrams & text. Otherwise feel-free to review lecture recordings & pre-class videos: https://www.austincc.edu/apreview/PhysText/Cardiac.htmlLinks to an external site.

Lecture 10 handout Key (will post at the end of the week :) have some folks making up the lecture)

 

Guiding Questions:

1. Lay out the steps of myocardial cell contraction. Describe carefully what happens in each step.

What is the Ca2+ spark (rush of calcium into the cell)? Where does the Ca2+ come from?

Lay out the steps that lead to relaxation of the myocardial cell after contraction.

How is Ca2+ removed in a contractile myocardial cell?

3. What is the resting membrane potential of a contractile myocardial cell?

What is the trigger for the action potential in contractile myocardial cells? What is the source of that stimulus?

What type of channel activity results in the rising phase, plateau phase and falling phase of the action potential? What is the trigger for each of these types of channel activity?

4. Why is the refractory period in contractile cells so much longer than that in skeletal muscle cells? (covered in post-class week 6, not lecture)

How does the refractory period for myocardial cells prevent summation of force in these cells*****

What would the impact of summation be if it could happen in these cells? Where does the Ca2+ come from to lengthen the refractory period so much? ****These questions will actually be answered during your pre-class week 7! Feel free to skip for now and make sure they are answered by next week!

5. Describe the origin of the pacemaker potential found in autorhythmic cells.

How does the pacemaker potential trigger the rising phase in autorhythmic cells?

What causes the falling phase in autorhythmic cells?

Compare and contrast the rising phase of the autorhythmic cells with the rising phase of the contractile cells, the rising phase in skeletal muscles and the rising phase in neurons.

6. How do action potentials in autorhythmic cells translate to the contraction of the contractile cells?

 

. What is the function of the cardiovascular system? Give some examples of materials transported by the system.

Describe the organization, pattern of blood flow and the major function of the cardiovascular system using the following terms: heart, arteries, capillaries, and veins.

Describe the structure of the heart and pattern of blood flow through the heart using the following terms: atria, ventricles, septum, vena cava, aorta, pulmonary veins, pulmonary arteries, AV valves, papillary muscle*, chordae tendineae*, semilunar valves.

What is the function of the valves in the heart? Where does the energy come from to open and close the valves? (*covered in lab Week 6)

2. What is the importance of the gap junctions that connect the autorhythmic cells with the contractile cells?

Outline the steps of the intrinsic conducting system and associate them with the steps of the cardiac cycle.

Describe how the SA node controls heart rate. What would happen when the SA node is damaged?

Explain how heart rate is controlled by the parasympathetic system and the sympathetic system. Be sure to discuss the intrinsic heart rate, the neurotransmitters and receptors that operate during control of heart rate

3. Define the terms systole and diastole in terms of the cardiovascular system.****

Explain how pressure gradients drive blood flow in the cardiovascular system. Identify the location of high pressure and low pressure during systole and diastole.*** these questions will be covered next Tuesday's lecture

week 2 preclass activity quizz

 

Question 2

0 / 1 pts

When I teach this in person, I like to make an analogy between pacemaker cells, contractile cells, and the autonomic nervous system (ANS). Remember that the ANS is divided into sympathetic (speeds up heart rate) and parasympathetic (slows down heart rate).

 

Consider how lights can be turned on/off and that some have a dimmer switch:

 

I would argue that each component: pacemaker, contractile cells and autonomic nervous system match the way this lighting system works. Check your understanding by matching the terms below.

Correct!

Pacemakers are autorhythmic and determine when contractile cells will depolarize.

 

               Light switch on/off             

Correct!

ANS can determine how fast or slow pacemaker and contractile cells depolarize and therefore speed up/slow down heart rate.

 

               Dimmer switch (controls how bright/dim lights are)             

Correct!

Contractile cells are THE cardiac muscle cells that generate contractions (pumping/beating) of the heart. They follow the pace set by pacemakers & ANS.

 

               The actual light (how bright or on/off)             

How are contractile and pacemaker cells connected? Select all

Correct!

  

They have continuous channels and share ions, forming a network of cells called a syncytium.

 

  

There are two syncytia: atrial and ventricular. This explains why the atria contract at once and the ventricles contract second.

 

You Answered

  

If connections between pacemaker & contractile cells are most similar to a chemical synapse.

 

Correct Answer

  

If connections between pacemaker & contractile cells are most similar to an electrical synapse.

 

How does the heart pump? How does it know when to beat?

  

Contractile cells set the pace/rhythm of beats. Autorhythmic cells cause cardiac muscle contractions

 

Correct!

  

Autorhythmic cells set the pace/rhythm of beats. Contractile cells cause cardiac muscle contractions

 

Week 3 practice question

 Question 1

1 / 1 pts

Chlorpromazine (marketed under brand names Thorazine and Largactil) is a drug used to treat psychotic disorders such as schizophrenia or manic-depression in adults. Chlorpromazine was developed in the 1950s and its introduction as the first antipsychotic on the market has been labeled as one of the great advances in the history of psychiatry.

Chlorpromazine blocks postsynaptic receptors for several different neurotransmitters, such as dopamine and serotonin. Predict the effect of chlorpromazine on synaptic transmission by selecting all of the steps it will directly inhibit in the picture below.

  

5

 

  

4

 

  

1

 

  

2

 

  

3

 

 

Question 2

1 / 1 pts

Some neurotransmitter receptors are ion channels that open when the neurotransmitter binds to them. Those receptors are called:

  

mechanically gated ion channels.

 

  

light-gated ion channels.

 

  

ligand-gated ion channels.

 

  

voltage-gated ion channels.

 

 

Question 3

1 / 1 pts

Funnel-web spiders are found in southeast Australia, around Sydney. Others are found in Europe, New Zealand, and Chile. They are not native to the United States, although some people may keep them as exotic pets.

Their bites are very painful and dangerous. They have been known to cause serious symptoms, such as agitation, confusion, numbness of mouth and lips, and even coma and death.

Funnel-web spider venom is a neurotoxin that blocks gated calcium channels. Its effect would be a/an:

  

increased neurotransmitter release.

 

  

decreased neurotransmitter release.

 

  

decreased production of neurotransmitter.

 

  

increased production of neurotransmitter.

 

 

Question 4

1 / 1 pts

Identify the ion that would move through the channel to produce an IPSP.

Ions 1-3 are in the extracellular fluid (blue background),  ions 4-6 are in the cytosol (yellow background). Figure out which ion and which direction it would flow based on what you know about concentration gradients for each ion.

  

Na+

 

  

Ca2+

 

  

K+

 

 

Question 5

1 / 1 pts

One type of channel involved in generating postsynaptic potentials at a chemical synapse is the:

  

ligand-gated ion channel.

 

  

light-gated ion channel.

 

  

mechanically gated ion channel.

 

  

voltage-gated ion channel.

 

 

Question 6

1 / 1 pts

Selective serotonin reuptake inhibitors (or SSRIs), such as Prozac, Celexa, Lexapro, Paxil, and Zoloft, are a class of drugs used to treat mood disorders such as depression and anxiety. They inhibit the transporter responsible for serotonin reuptake into the presynaptic neuron. What is the effect of the SSRIs on the serotonin concentration in the synaptic cleft?

  

The serotonin concentration in the synaptic cleft will increase.

Correct. When reuptake is inhibited, more serotonin stays in the cleft longer and is available to stimulate postsynaptic neurons. Since mood disorders often correlate with reduced serotonin availability and receptor stimulation, SSRIs are effective in helping patients who suffer from these disorders.

  

The serotonin concentration in the synaptic cleft will decrease.

 

Question 7

1 / 1 pts

Which of the following does NOT happen to neurotransmitters during synaptic transmission termination?

  

Diffusion away from synaptic cleft

 

  

Reuptake into presynaptic neuron

 

  

Uptake into postsynaptic neuron

 

  

Degradation by enzymes

 

 

Question 8

1 / 1 pts

Use what you learned during the Lecture 3 handout.

Cocaine is a powerfully addictive stimulant drug made from the leaves of the coca plant native to South America. As a street drug, cocaine looks like a fine, white, crystal powder or it is processed to a make rock crystal.

Cocaine acts as a dopamine reuptake inhibitor. Therefore, cocaine will:

  

decrease dopamine in the synaptic cleft.

 

  

increase dopamine receptor stimulation.

 

Correct. Less reuptake means more dopamine remains in the cleft and is available to stimulate dopamine receptors.

  

decrease dopamine inside the postsynaptic neuron.

 

  

increase dopamine in the axon terminal.

 

 

Question 9

1 / 1 pts

During the absolute refractory period, the axon membrane:

  

is unable to generate an action potential.

 

  

contains open voltage-gated Na+ channels.

  

is at –90 mV.

 

  

is more responsive to depolarization.

 

 

Question 10

1 / 1 pts

The refractory period of an action potential...

  

Allows bidirectional flow of the action potential

 

  

Is not a component of every action potential

 

  

Prevents flow of action potential toward cell body

 

  

Has no effect on direction of action potential propagation

 

 

Question 11

1 / 1 pts

The faster, more efficient way of propagating an action potential is:

  

unmyelinated conduction.

 

  

saltatory conduction.

 

  

disruptive conduction.

 

  

continuous conduction.

 

 

Question 12

1 / 1 pts

The threshold potential is best defined as the potential at which...

  

Voltage-gated potassium channels open

 

  

Voltage-gated potassium channels close

 

  

Voltage-gated sodium channels open

 

  

Chemically gated sodium channels open

 

 

Question 13

1 / 1 pts

Action potentials self-propagate because...

  

ATP is always available to drive the action potential

 

  

Each action potential triggers another in the next section of axon

 

  

They are a form of negative feedback

 

  

Neurotransmitter is released constantly