pset

Explain what homeostasis is & how feedback loops are used in its maintenance

homeostasis allows the body to maintain a relatively stable internal environment. There are two main types of feedback loops: positive & negative. Positive feedback loops have an enhancing effect while negative feedback loops have an inhibitory effect. These loops help the body compensate when something is over or under production in order to maintain this "stable" environment

Match the letters to corresponding fluid compartments *note that C spans both B & D

A) intracellular fluid

B) blood plasma

C) extracellular fluid

D) interstitial fluid

what are the predominant ions in the ECF

sodium, chloride, bicarb

predominant ions in the ICF

potassium, phosphate

Describe the purpose of the Na+/K ATPase pump. Which ions are pumped into the cell, and which are pumped out of the cell? Are these ions transported across the cell membrane in an active or passive manner?

the purpose of the Na+/K ATPase pump is to establish a resting membrane potential. Sodium is therefore pumped out of the cell and potassium is pumped in. They are transported in an active manner.

Write out the chemical reaction corresponding to the hydrolysis of ATP.

ATP + H20 -\> ADP + Pi + Energy

How does the cell regulate the transport of molecules across its membrane? Give two types of proteins that aid in ion transport.

The cell regulates the transport of molecules through its membrane (composed of a phospholipid bilayer) by allowing diffusion to occur for small non-charged molecules, or by using proteins to facilitate the transport of larger, charged molecules. Two types of proteins that aid in ion transport are channel proteins and carrier proteins.

Large, charged molecules generally can diffuse across the cell membrane (T/F)

F

Osmosis results in water moving down its concentration gradient

T

Can water (H2O) diffuse across the cell membrane without the help of a protein? Which protein channel can facilitate water's crossing of the membrane?

Yes, water can diffuse even though it is a polar molecule because of its small size and because it has no overall charge. Another protein channel, called an Aquaporin, can also help facilitate water's diffusion through the phospholipid bilayer of the cell membrane.

Positive feedback loops allow amplification of an initial signal (T/F)

T

Describe a biological example of negative feedback & a biological example of positive feedback

negative - baroreceptor reflex

positive - thrombin autoactivation/blood clotting

SNS & PNS release \_____ from the preganglionic neuron. SNS releases \____ at postganglionic neuron while PNS releases \_____

acetylcholine, NE, acetylcholine

Vasovagal syncope results from an initial parasympathetic response followed by a rapid, sympathetic response that overshoots and leads to bradycardia, hypotension, and cerebral hypo-perfusion. (T/F)

F - other way around

Pre-ganglionic sympathetic neurons originate in the sacral region of the spine T/F)

F

The sweat glands are controlled by the parasympathetic nervous system and use acetylcholine as the neurotransmitter.

F

Which of the following adrenergic receptor types are found on the target organs that are innervated by post-ganglionic neurons?

Alpha 1, Beta 1, Beta 2

What are the three major components of asthma treatment? Give an example of one drug from each of the three categories, and briefly explain how each drug works to alleviate asthma symptoms.

alleviate bronchoconstriction, reduce secretions, reduce inflammation.

1) albuterol - acts on adrenergic receptor beta-2& 1 as an agonist to reverse bronchoconstriction (dilation of smooth muscle) and open the airway

2) atrovent - antagonist blocks ACh receptors \= less PNS activity & decreased bronchiolar secretions

3) steroids - like prednisone or advair which reduces inflammation

What is one side effect of asthma treatment with albuterol? Explain the underlying receptor pharmacology.

One side effect of asthma treatment with albuterol is heart palpitations or shakiness.

The reason for this is that albuterol binds to the beta-2 receptor, but can also bind to the beta-1 receptor and cause activation of the receptor. The beta-1 receptors are found on the heart muscle and kidney, so activating the receptors through albuterol can lead to an increased heart rate or heart palpitations.

Based on what you know about skeletal muscle contraction, why do patients exhibiting a cholinergic toxidrome experience muscle spasms, cramps, and paralysis?

A cholinergic toxidrome is caused when the parasympathetic nervous system is much more stimulated than the sympathetic nervous system. This can be caused by excess stimulation of nicotinic receptors like a lack of acetylcholinesterase to break down acetylcholine located in the neuromuscular junction. Having too much acetylcholine in the neuromuscular junction means that more calcium is triggered to release from the sarcoplasmic reticulum, causing more calcium to bind to troponin on actin filaments, allowing myosin to attach to actin and creating more muscle movement. Patients with a cholinergic toxidrome experience muscle spasms, cramps, and even paralysis because of the excess acetylcholine that causes this excess muscle movement.

Explain how an anticholinergic toxidrome can be distinguished from a sympathomimetic toxidrome.

a sympathomimetic toxidrome would likely cause warm, moist skin (sweat) and a anticholinergic toxidrome would cause hot, dry skin and dry mouth symptoms from dry mucous membranes.

A 27-yo male patient presents in the Emergency Department with altered mental status, tachycardia, hypertension, and mydriasis. His clothing is soaked in sweat, and his skin is warm to the touch.

a. Which of the three toxidromes we discussed in lecture do you suspect this patient is exhibiting?

b. Suppose you discover that the patient had ingested what he believed to be ecstasy just over an hour ago. What is the mechanism of action of this drug? Why does it result in the observed signs and symptoms?

c. After ingesting ecstasy, patients often drink excessive quantities of water. Explain the disruption in ion balance that may result. How can this condition lead to abnormal neurological functioning? What is the treatment for this ion imbalance?

d. In general, which drug would be given to treat the toxidrome identified in Part (a)?

I suspect that this patient is experiencing sympathomimetic toxidrome.

b. Ecstasy's main mechanism of action in this case is that it increases the body's release of noradrenaline or norepinephrine (NE) & serotonin. This increase of NE means that the sympathetic nervous system is overstimulating adrenergic receptors throughout the body. The overstimulation of the sympathetic nervous system is responsible for the symptoms of tachycardia, hypertension, mydriasis, and an altered mental state.

c. Water diffuses down its concentration gradient, so since normally the extracellular fluid of the cell has a low sodium concentration, water will flow into the cell. This causes the cells to swell, which is especially dangerous if untreated because it could cause brain herniation and compression of the brainstem (from cells in the brain swelling), leading to impaired neurological functioning. The treatment for this issue (hyponatremia) caused by the ion imbalance is a concentrated sodium solution, like an IV of hypertonic saline, in order to draw out water from the swelling cells and thereby reduce pressure in the brain.

d. One drug that could treat a sympathomimetic toxidrome is diazepam (valium) which can help calm the patient.

After a long flight, a parent brings a 9-yo child into the Emergency Department. The child is anxious, flushed, and hyperthermic, and she is complaining of dry mouth.

a. Which of the three toxidromes we discussed in lecture do you suspect this patient is exhibiting? Why?

b. What is one possible drug that can cause the toxidrome identified in Part (a)? Describe the mechanism by which it leads to a change in neurotransmitter availability at the synapse.

c. Which drug could be used to treat this toxidrome? What is its mechanism of action (how does it work?)?

a. I suspect that this patient is experiencing an anticholinergic toxidrome because anticholinergic toxidrome symptoms include being hot and flushed. Also, the child has dry mouth which makes sense if the sympathetic nervous system is more stimulated than the parasympathetic nervous system as the SNS causes decreased secretions (saliva).

b. One possible drug that could cause this toxidrome is Benadryl. Benadryl functions by blocking the ability of acetylcholine to bind to receptors, making acetylcholine less available for stimulation.

c. One drug that could be used is Physostigmine. Physostigmine is a acetylcholinesterase inhibitor which means that it prevents acetylcholinesterase from breaking down acetylcholine. This lets acetylcholine stay in the synaptic cleft for longer, giving it a better opportunity to bind to any available receptors so it can increase PNS activity back to baseline

Cardiac and smooth muscle are under involuntary control.

T

The pulmonary artery transports oxygenated blood to the lungs.

F

In the systemic capillaries, oxygen is picked up by the blood, and carbon dioxide is released from the blood into the tissues.

F

The arteries are the major sites of resistance in the systemic circuit.

F

The heart valves sit approximately in a plane of non-conducting, fibrous tissue.

T

Because the left ventricle pumps against the higher-pressure systemic circuit, the left ventricular wall is thicker than the right ventricular wall.

T

Desmosomes allow for the electrical functioning of the syncytium, while gap junctions allow for the mechanical functioning of the syncytium.

F

The hematocrit is the buffy coat of the blood, comprising approximately 55% of whole blood.

F

The spleen is the site of erythropoietin generation and release.

F - kidney

Each molecule of hemoglobin has the potential to bind four oxygen molecules.

T

Thrombolytics function by actively breaking down clots, while anticoagulants work to slow clot formation.

T

A thrombus is a clot; an embolus is a traveling clot.

T

During diastole, the heart is contracting and ejecting blood, and during systole, the heart is relaxing and filling with blood.

F

What are the three components of the neuromuscular junction (NMJ)?

presynaptic axon terminal, postsynaptic membrane of skeletal fiber, synaptic cleft

what are the two components of a motor unit

muscle fibers, controlling neuron

actin and myosin are also known as the _ and _ filaments are the _ proteins involved in skeletal muscle contraction, while troponin (which binds __) and tropomyosin (which twists around __) are the regulatory proteins involved

thin & thick, contractile, ca2+, actin, regulatory

We discussed two situations in which calcium plays a major role during skeletal muscle contraction. Describe the role of calcium release in BOTH of those situations.

Calcium is critical for skeletal muscle contraction. When an action potential reaches the axon terminal, this causes voltage-gated calcium channels to open, allowing calcium ions into the axon terminal. The calcium binds to vesicles and causes acetylcholine (neurotransmitter) to be released. Thus, calcium is essential for allowing acetylcholine to enter the synaptic cleft.

Another way calcium is critical is that when the action potential reaches the skeletal muscle, it eventually triggers calcium release from the sarcoplasmic reticulum. The calcium ions that are released end up binding to troponin on actin filaments, uncovering cross-bridge binding sites on actin, facilitating the process of muscle movement. Thus, calcium is also essential for the eventual skeletal muscle contraction.

At a biochemical level, walk through how calcium release in a muscle cell enables myosin's binding with actin.

Calcium is released from the sarcoplasmic reticulum of a muscle cell after an action potential triggers it. The calcium ions then bind to troponin on actin filaments. When calcium binds to troponin, this causes tropomyosin to physically move to uncover cross-bridge binding sites on the actin. Myosin is then able to bind to the actin. Thus, calcium is a critical part of the process to enabling myosin to bind with actin.

Explain what rigor mortis is and how it comes about.

Rigor mortis is when a few hours after a person or animal dies, the joints and muscles stiffen. This occurs because ATP is no longer being produced by the body, meaning the actin-myosin complex cannot dissociate, so the muscles and joints remain in their contracted state.

Write out the names (in order) of the heart chambers, valves, and major vessels through which blood passes through as it flows from the vena cava to the aorta.

After blood is deoxygenated at the organs, it passes through the superior and inferior vena cava into the right atrium. Through the tricuspid valve, blood then goes to the right ventricle. Blood then pushes through the pulmonary semilunar valve until it reaches the pulmonary arteries. Blood goes from the pulmonary arteries to the lungs to get oxygenated. From the lungs, the blood goes through the pulmonary veins back into the heart. The blood goes to the left atrium, where it goes through the bicuspid valve into the left ventricle. Blood goes into the aortic semilunar valve from the left ventricle. This feeds into the aorta.

The aorta supplies blood to systemic arteries which will provide oxygenated blood to different organs, repeating the process.

Is heart valve opening and closing considered an active or passive process? Which factor determines whether a valve is open or closed?

The heart valve opening and closing is a passive process. Whether a valve is open or closed depends on whether the pressure is greater in front of or behind the valve. When pressure is greater behind the valve, it will open. When pressure is greater in front of the valve, it will close.

functions of the chordae tendineae in the heart

Prevents the flow of blood from the ventricles into the atria during ventricular ejection

Prevents the AV valves from prolapsing during ventricular ejection

Explain two examples of valvular pathology, and indicate potential treatment options.

Regurgitation: Blood back-flowing reduces the amount of blood that can be effectively pumped, making the heart have to work harder just to get enough blood out to the rest of the body. One possible solution is an Annuloplasty, where surgery would be done to fix the "leaky valve" hopefully preventing back-flow in the future.

Atresia: When valves aren't formed properly in the body, or there are essential parts of the valve that are missing which is potentially life threatening because it makes the flow of blood ineffective. One possible treatment would be surgery in which the improper valve could be replaced with one that functions normally.

three layers of heart wall

myocardium, epicardium, endocardium

What is the purpose of pericardial fluid?

The pericardial fluid lubricates the heart and reduces friction during contraction.

Briefly, list the three steps of clot formation.

1. Vascular Spasm - constriction to reduce blood loss

2. Formation of Platelet Plug - blockage of the injury site

3. Blood Coagulation - formation of fibrin meshwork (a.k.a a clot)

What is the effect of thromboxane A2 and ADP release in clot formation?

Thromboxane A2 and ADP is released by platelets once a vessel is injured. These two substances recruit more platelets to the site of vascular injury (eventually helping blood coagulate to form a clot).

identify four roles of thrombin

converts fibrongen to fibrin

platelet aggregation enhacement

prothrombin -\> thrombin

activates factor XIII

The blood normally contains many clotting factors. Name 3 protective mechanisms that exist to allow activation of the clotting factors only under the appropriate circumstances.

1) AT-III inactivates thrombin directly

2) Thrombomodulin - binds thrombin resulting in activation of protein C and inactivation of factor V and factor VIII

3) Fibrin meshwork which inactivates thrombin itself.

Patients with Vitamin K deficiency will clot very easily.

F

List three risk factors for the development of coronary artery disease.

1) Hypertension (high blood pressure)

2) Diabetes

3) Smoking

Explain one treatment option for a patient with a severely occluded coronary artery.

CABG - Coronary Artery Bypass Graft

When a coronary artery is severely occluded, one possible treatment is to circumvent the vessel by grafting a vein. This essentially means that blood no longer needs to flow through the occluded part of the artery and instead can flow through the grafted vein.

order of electrical signals through the heart

SA node

AV node

Left and right Bundle branches

Purkinje fibers

internodal pathway

interatrial pathway

purpose of the AV nodal delay?

It allows sufficient time for blood to be expelled from the atria into the ventricles before ventricular contraction occurs.

What are the underlying conduction abnormalities in first-degree atrioventricular (AV) block and third-degree AV block?

In first-degree atrioventricular block, conduction is slowed through the AV node. Usually, electrical impulses travel through the atria before reaching the AV node and then the ventricles. The AV node acts as a way to slow down the electric impulse in order for there to be adequate time for the ventricles to fill with blood before contraction. With first-degree atrioventricular block, the AV node slows the electric impulse too much.