#2 CASE STUDY: BAD FISH

12. Briefly describe the role of the autonomic nervous system in human physiology. What are the two divisions of this system?

1. The part of the Peripheral Nervous System, the ANS -nerves that control involuntary body functions of muscles, glands, and internal organs.* 2 divisions- sympathetic and parasympathetic - the automatic nerous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal. This system is the primary mechanism in control of the fight or flight response.

5. When nerve cells are at rest, there is an unequal amount of positive and negative charges on either side of a nerve cell membrane. This charge difference is called an electrical potential. Describe this "potential" when the neuron is at rest (resting potential).

1. The resting potential develops as there is a greater amount of negatively charged ions present inside the cell and more positively charged ions are present outside of the cell; net negative charge inside of the cell is around -65 mV and then a stimulus initiates the action potential and this force tries to open the voltage-gated sodium channels 2. Resting membrane potential: When a neuron is not sending any signals, it is said to be at rest. There is an unequal distribution of ions across the cytoplasmic membrane due to the action of ion-specific transporters. The inside of the neuron is negative relative to the outside. When the neuron is at rest, K+ ions can cross through the membrane, while Cl- and Na+ ions are not readily permeable. The Na+/K+ pump creates the ion concentration gradient by moving 3 Na+ out of the cell while moving 2K+ into the cell, against a concentration gradient. Due to this, more sodium ions accumulate outside the cell leaving the cell inside more negative. This difference in the ion concentration creates a potential, called membrane potential. The resting membrane potential (of a neuron) is -70 mV.. which means that the inside of the neuron is 70 mV less than the outside. How the resting potential is generated - When at rest, the neurons have a stable separation of charge at either sides of the membrane called the resting potential. The majority carrier outside the membrane is positive (cations) while that found inside the membrane are negative (anions). For a reference potential, the outer potential is considered 0 while the inner lies at -60mV. The potential exists because of the existence of many ions on either side of the membrane. The important cations used are Potassium, Sodium and Calcium.Anions are Chloride and other organic ions like glutamate. Different ions have different concentration gradients inside or outside the cells.Organic anions and Potassium have a higher concentration inside the neuron while Sodium and Calcium are present outside the cell in higher concentrations. Two forces play a role in the movement of ions through the membrane. They are the electrostatic potential and the diffusion potential.According to the electrostatic potential the ions move towards their opposite gradient charges. Since the outer membrane is positive while the inner membrane is negative, Organic ions move outide the cell, Potassium moves inside, Sodium moves inside, chloride moves outside and calcium moves inside. The diffusion potential depends on the concentration of ions on either side of the membrane. The ions move from higher to lower concentration until an equilibrium is attained. According to the diffusion potential -Organic ions move outside as their concentration outside is lower.Potassium moves outside as well for the same reasonSodium moves inside for the same reasonChloride moves inside and Calcium moves inside for the same reason (concentration differences) The resting membrane potential is a sum of both the above potentials. 3. sodium-potassium pump K+ leak channel, K+ always leaking out anions (more inside the cell than outside) - Part of why it is called a potential is because of the potential energy associated with the charge difference in particles on either side. The electrical forces, or charge difference, makes various behaviors possible due to various voltages. Resting potential is what the membrane potential is at when there is no stimulus. it is generally -70mV, closer to the electrical potential of potassium within a cell.

3. Why do sodium ions need channels in order to move into and out of cells?

- Channels help to develop an action potential and in order to repolarize the channels and also triggers sodium channel inactivation (negative resting potential) by this way they can regulate the number of ions that enter and leave the cell and conduct nerve impulses. These channels in turn allow the rapid intake of sodium ions. - This is how the cell membrane permeability is regulated. If unregulated, the cell would don't survive imbalanced exposure to various chemicals. Also, sodium can not cross the membrane via simple diffusion and needs to be facilitated via channels.

13. Atropine was administered in the ER as part of Dr. Westwood's care. What effect did it have on his vitals after it was administered? Atropine acts as an antagonist within the central nervous system, which means it acts as a blocker of specific cellular functions. What part of the autonomic nervous system does atropine block to produce its effect on Dr. Westwood?Describe the structure of a sodium ion.

- His vitals returned to self-sustainable and normal., Atropine is a competitive antagonist of muscarinic acetylcholine receptors, a group of G-class receptors proteins, blocking the action of acetylcholine and therefore suppressing the actions of the parasympathetic nervous system.

15.As you continued to experiment with higher concentrations of the toxin, you found cases when the cell could not repolarize at all, or if it began to repolarize, it would immediately depolarize again. Using this description and the description in the previous question, describe how this toxin acts on voltage-gated sodium ion channels.

- It is possible that the inactivation gate of the sodium ion channel is not able to reset, which is necessary for repolarization to occur. It is also possible that the sodium channel is simply kept open.

2. What is a voltage-gated sodium ion channel? What is it made of? What is its function?

- The voltage-gated sodium ion channels are known to be a class of transmembrane ion channels; activation of channels takes place by the electrical membrane potential near the channel. They are mainly made up of several subunits arranged in a way; a central pore is there and ions can travel down their electrochemical gradients through this pore. Their function is the initiation of action potential and propagation in excitable cells. - voltage-gated sodium ion channels are found on the plasma membrane of neurons. Their function is in the transmission of the action potential ("electrical impulse") - voltage-gated sodium channels are membrane proteins that change conformation in response to depolarization of the membrane potential, open a transmembrane pore, and conduct sodium ions inward to initiate and propagate action potentials.

11.Explain how tetrodotoxin is involved in the development of hypotension and hypoventilation.

1. *Hypotension- abnormally low blood pressure *Hypoventilation- ventilation of the lungs that does not fulfill the body's gas exchange needs. - The toxin blocks the diffusion of sodium ions through sodium channels...The nerves regulate the rate and strength of contraction in the heart so it would eventually cause hypoventilation and low blood pressure

6. What is happening to the electrical potential of a neuron when it generates an action potential? What is the function of the action potential in neurons?

1. A neuron further generates an action potential and sodium channel opens up and sodium enters into the cytoplasm, and rapid depolarization takes place; by this process the net charge changes from negative 65mV to positive 35mV. The function of this action potential is to develop communication with other neurons and eventually the brain and tissues. 2. Dr. Westwood experienced numbness after eating the puffer fish meal because the toxin tetrodotoxin blocks the opening of voltage-gated sodium channels (Na+ channel) then there will be no depolarization of neurons and no generation of an action potential so there will be no conduction of impulse that will lead to numbness. - At the action potential, the voltage depolarizes or approaches zero. It even becomes positive. This activates a sequence of channel activity that allows local and destination signaling for other target cells to respond to accordingly

7. Describe the role of sodium ions and sodium channels in the action potential.

1. After reaching the transmembrane potential or threshold sodium channels opens and the sodium goes into the cell and causes a depolarization, when the Tran membrane potential reaches +30 mV the voltage-gated sodium channels close; which is known as sodium channel inactivation, and then the voltage-gated potassium channels open up and potassium ions moves out of the cells and which in turn shifts the transmembrane potential towards resting levels. The sodium channels remain closed until the repolarization takes place. - Sodium ions rush into the cell during action potential and close at the top of the depolarization step. This is due to the opening of the channel, which is caused by a change in membrane potential--up to the threshold, which signals sodium channels to open and let sodium enter. Sodium enters due to electrochemical forces acting on it.

1. As mentioned in the case description, tetrodotoxin is a molecule that blocks voltage-gated sodium ion channels. Describe the structure of a sodium ion.

1. Answer: Sodium atom has 1 electron in the outer orbital shell. It loses this outer election to become a sodium ion. The ion still has 11 protons but now only 10 elections, thus a net positive charge of +1. Positive charged ion 2. Voltage-gated Sodium channels are sensitive to the changes in membrane potential. This means these channels are opened at a certain membrane potential and remain closed at certain membrane potential. For example, if any impulse arrived at a nerve cell caused an influx of sodium ions, the membrane potential becomes slightly positive, if this potentials difference is enough to equal to threshold potential, fast sodium channels will be opened to initiate depolarization. If the impulse fails to bring the threshold membrane potential, the fast sodium channels remain in a closed state because they open and close according to the membrane potential, that's why we call them voltage-gated channels. The structure of sodium channels contains a large alpha subunit and associated beta subunits. The core of the channel is formed by the alpha subunit. Expression of alpha subunit by the cell makes the cell be able to form voltage-gated sodium channels (other modulating subunits including beta subunits may not be expressed). The voltage dependence can be altered by the interaction of alpha subunits with the other accessory proteins. The channel pore contains the selectivity filter consisting of negatively charged amino acids, which specifically attract sodium ions and always keep out the anions such as chloride ions. Voltage-gated sodium channels contain neurotoxin binding sites on their alpha domain. The person is likely to suffer from paralysis, an immediate decrease in the rate of respiration, and difficulty in breathing is noticeable, which needs immediate hospitalization. The person needs to be administered with an anti-venom - depolorizes membrane and makes it more positive

4. Describe the process involved in the movement of ions through these channels.

1. Movement of Sodium through the channel takes place by the diffusion process as inside of cell has net negative charge and in outside due to high concentration of sodium ; net charge is positive so cells pull sodium inside. Then the charges are reversed and the concentration inside the cell is greater than outside the cell; that's how potential energy develops. - In a neuron, chemically gated ion channels are present on the dendrites ad cell body. Along the axon are voltage-gated sodium and potassium channels. As the channels open, ion movement across the plasma membrane increases, and the membrane potential is changed. - primary active transport

9. Now that you have addressed some of the basic biology of this case, explain why Dr. Westwood experienced numbness after eating the pufferfish meal.

1. Neuron could not communicate; as no action potentials can be generated due to blocking of sodium channels which are involved in the transmission of sensory information to the brain; the area affected by the tetrodotoxin would be experienced as numbness or no way of feeling. 2. The numbness is caused by the tetrodotoxin blocking the sodium channels in the sensory PNS - Without sodium channels, the neurons were unable to communicate. Sensory pathways were inhibited by nerve blocks occurring throughout his body, Loss of sensation is a sign of neurological disease/disruption.

10. Paralysis is a term used to describe the loss of function of muscle. If tetrodotoxin's effect is on neurons, why did Dr. Westwood experience paralysis?

1. Paralysis deals with motor neurons and like other neurons, these are also involved in the process of receiving and sending impulses and to create muscle movement of our bodies; if any nerves lacking the action potential part, then paralysis will result and in this case, the tetrodotoxin's guanidino group; inhibits the neuronal activity by blocking the sodium channels and preventing the movement of sodium ions that greatly contribute to an action potential in muscle cells also. 2. Neurons stimulate muscles to contract. So, if the neurons are unable to communicate with the muscles, then they will not be able to contract = paralysis. - He was unable to move because his muscles received no stimuli from neuropathways that we being inhibited by the toxin.

1. Your Company Name: What do you want to call your company? Be creative! 2. Name of Your Drug: 3. Treatment of: - What does your drug treat? - What other diseases, problems etc. might it be useful for? 4. Mechanism of Action: - Describe how your drug will work. - Be sure to provide details regarding its action. You are now familiar with the activity of this toxin at the level of molecules and cells, so your description should contain details of how your drug works at that level. 5. Dosage Form: - How will it be administered to patients? 6. Side Effects: - What type of side effects might your drug have?

1. PhatPharma 2. Tetrodoze 3. - It contains sodium ion channel function. - There are many diseases related to ion channels. Mutations in muscle voltage-gated sodium, potassium, calcium and chloride channels, and acetylcholine-gated channel may lead to such physiological disorders as hyper and hypokalemic periodic paralysis, myotonias, long QT syndrome, Brugada syndrome, malignant hyperthermia and myasthenia. Neuronal disorders, e.g,, epilepsy, episodic ataxia, familial hemiplegic migraine, Lambert-Eaton myasthenic syndrome, Alzheimer's disease, Parkinson's disease, schizophrenia, hyperekplexia may result from dysfunction of voltage-gated sodium, potassium and calcium channels, or acetylcholine- and glycine-gated channels. Some kidney disorders, e.g., Bartter's syndrome, polycystic kidney disease and Dent's disease, secretion disorders, e.g., hyperinsulinemic hypoglycemia of infancy and cystic fibrosis, vision disorders, e.g., congenital stationary night blindness and total color-blindness may also be linked to mutations in ion channels. (Dworakowska B, Dołowy K. Ion channels-related diseases. Acta Biochim Pol. 2000;47(3):685-703. PMID: 11310970.) I found this list from an article on the web. It is very sad that people have so many different types of issues from malfunctioning sodium channels 4. - The drug would work by adding another gate to the ion channels temporarily, which would clear and reset each aspect of the process. It would attach to the outer end of polarity sensing rods. It would give a momentary disruption to an ion channel to reset it, before moving to the next neuron so that the body doesn't get shut down all at once. 5. - How will it be administered to patients? It would be taken orally or by IV if they're unconscious; beginning at the origin site of malfunction. In the case of pufferfish poisoning, it would follow the ingestion pathway. 6. - It would likely cause cardiac arrest, paralysis, and brain damage from stroke because the channels are integrated with various factors of homeostasis.

8. What would happen to a neuron if it were exposed to tetrodotoxin? Be specific regarding its effect on the ability of a neuron to communicate.

1. When a neuron is exposed to tetrodotoxin, there is a guanidino group attached to the tetrodotoxin that is drawn into the cell and it blocked sodium ion channels also prevents sodium from entering into the cell. This would stop it from depolarizing and would block the cell from starting an action potential so it would be incapable of communicating further and the overall charge of the neuron remains negative which leads to paralysis. 2. If a neuron is exposed to tetrodotoxin, then sodium is NOT able to bind to the sodium ion channels and is NOT able to enter the neuron. If this happens, then the transmission speed of messages is slowed drastically. - Tetrodotoxin disables sodium channels. the transmission of this block of signals among neurons.