1. Hypocalcemia induces a condition known as tetany , which is characterized by

Question

1. Hypocalcemia induces a condition known as tetany, which is characterized by involuntary muscle contraction. This condition arises from the modulatory effect extracellular calcium ions have on voltage-gated channels found on -motor neurons. Which type is it?

sodium

potassium

calcium

2. Clinical tests often involve blood treated with an anticoagulant. What does treatment of blood with a calcium chelator induce?

effective hypocalcemia

inactivation of a molecular cascade

inability of procoagulants to induce clot formation

all of the above

3. The concentration of calcium ions within the bloodstream is monitored by chemoreceptors within the parathyroid glands. These cells secrete parathyroid hormone in response to hypocalcemia. Whereas bone is a reservoir for calcium, such calcium exists as hydroxyapatite, which is a mineral that is insoluble in water. What must parathyroid hormone enable in order to counteract hypocalcemia?

induce bone resorption

decrease renal recovery of phosphate

increase renal recovery of filtered calcium ions

all of the above

4. The cortex of each adrenal gland contains chemoreceptive endocrine cells. Such cells secrete aldosterone. Should this vital process fail, then death will occur within several days due to compromised cardiac output and cardiac arrest. These outcomes are due to hyperkalemia. Excess extracellular potassium has a profound effect upon:

mitochondrial function

calcium-induced calcium release

molecular motor operation

resting membrane potential

all of the above

5. Arterial blood flow into skeletal muscle increased during our case study. Regional changes in blood flow are controlled by:

local metabolic demands

the brainstem’s vasomotor center

the motor cortex

6. Regional changes in blood flow are mediated by the contractility of arterial smooth muscle. Vascular smooth muscle is innervated by autonomic neurons whose bodies are found within the:

vasomotor center

thoracolumbar cord

paravertebral ganglion chain

Explanation / Answer

Answers

1. Sodium ion voltage gated channels are found on -motor neurons.

2. All of the above

Explanation

a. Calcium chelation causes hypocalcemia.

b. calcium chelation induce the inactivation of a molecular cascade

c. Chelation of calcium leads to conformational changes of the coagulation factors V and VIII which results in loss of the procoagulant activity

3. In response to hypocalcemia, PTH induces the kidneys to reabsorb calcium, the kidneys to increase production of calcitriol, thereby increasing intestinal absorption of calcium, and the bones to release calcium.

4. All the above

Explanation

a. Effect on mitochondrial function- hyperkalemia decrease the levels of glutamine within mitochondria in proximal tubular cells and hence the urea cycle was effected.

b. Effect on resting membrane potential- the early effect of mild hyperkalemia on myocyte function is to increase myocyte excitability by shifting the resting membrane potential to a less negative value and thus closer to threshold potential.

c. Effect on calcium- As the membrane potential reaches 40 to 45 mV during hyperkalemia,   calcium channels are stimulated , releases the calcium ions and allowing calcium to enter the myocyte.

d. Effect on molecular motor operation- There is an up-regulation (increase) of muscle nicotinic acetylcholine receptors (AChRs), which when depolarized with succinylcholine leads to efflux of intracellular potassium into the plasma, leading to acute hyperkalemia.

5. The brainstem’s vasomotor center - Regional blood flows can be efficiently regulated at the local level at the level of the brainstem.

6. Paravertebral ganglion chain - Autonomic ganglia or spinal ganglion contain cell bodies of neurons that carry signals from sensory organs to integration center.

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