4. How do sensory receptors communicate the intensity of a stimulus to the CNS?

Question

4. How do sensory receptors communicate the intensity of a stimulus to the CNS? The blood-brain barrier protects the brain from harmful substances in the blood, but it also protects the brain from potentially therapeutic chemicals that may reduce the size of brain tumors by killing cancer cells, alleviate depression, and aid in patient recovery from stroke or spinal cord injury. Two methods are currently being researched to get these helpful chemicals past the blood-brain barrier. The two methods are termed "molecular Trojan Horse" and osmotic "blood-brain barrier disruption." Based on their names, hypothesize how these methods might allow chemicals to pass through the blood-brain barrier. (see http://en. wikipedia.ora/wiki Troian Horse if not familiar with the legend of the Trojan Horse) Some pain receptors transmit signals on myelinated axons in neurons with conduction speeds up to 30 m/s and others are transmitted on very slow unmyelinated axons with speeds of 2 m/s and lower. Answer part a and b below, show calculations, state your assumptions 5. 6. How long does it take such receptors on your finger tips to be transmitted to your brain on myelinated axons? Unmyelinated axons? a. b. How long does it take such receptors on your toes to be transmitted to your brain on myelinated axons? Unmyelinated axons?

Explanation / Answer

4. Receptors are also called as transducers. Receptors convert any form of energy into electrical energy that is action potential. So receptors generate and conduct action potential to the central nervous system. As the intensity increases the number of action potential also increases. Hence sensory receptors convey the intensity of stimulus by changing the number of action potential.

5. trojan is the horse used to enter the Troy city. Greek hid in that horse and started war with troy. Same way molecular Trojan horse method is used for molecules that cannot pas through blood brain barrier. so in this method for example any chemical, drug will be hid in the molecules that can pass BBB. So once it is crossed hidden substances act on brain

Same way osmotic blood brain disruption works.

6. Pain sensation is carried by lateral spinothalamic tract which is a polysynaptic pathway.

a. Pain from finger tips on myelinated axons might take less than a second, whereas on unmyelinated axons it might take one second. because myelinated axons conduct fast whereas unmyelinated axons conduct very slow.

b. Pain from toes on myelinated axons might take ess than a second, whereas on unmyelinated axons it might take one second.

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