BIOL 1114 1st Edition Lecture 10-**Read your textbooks discussion of the nervous system, in areas of neurons, action potentials, and neurotransmitters*1- What is an action potential (AP)?In what direction does it move?- Will the poisons we discussed in the firstscenario (chemical defenses) will cause inhibition or disruption of the action potential? And how?- What is the resting potentialof a neuron? During the resting potential:  (1) What are the relative concentrations of the sodium ions(Na+)& the potassium ions(K+)ions on each side of the axon’s membrane? (2) What is the charge on the inner surface of the membrane?- What happens when the sodium ion (Na+)&potassium ions (K+)gates are open? When do they open? At random or otherwise?What does the Na+/ K+ (ATPase) pumpdo? How does it getenergy to operate? What happens when it fails to operate?What occurs within the synapse (synaptic cleft)?↓ When the action potential reaches the nerve (axon) terminal:↓- The (1) first neuron (the presynaptic cell)becomes electrically charged, causing molecule-filled sacs (vesicles) to release their contents(neurotransmitters or NTs)into the synapse. (2) These neurotransmitters then bond with receptor molecules on the postsynaptic cell (another neuron or a muscle cell),opening ion-gates. (3) These opened ion gates allow sodium ions (Na+) and potassium ions (K+) to enter the post-synaptic second cell (another neuron or a muscle cell).2The neuromuscular junction (NMJ): the special synapse between a neuron and a muscle cell.- * Remember that APs start in the pre-synaptic neuron & cause the release of the NT acetylcholine into the synapse. At the neuromuscular junction (NMJ), as soon as the NTs bind to the acetylcholine receptors, an AP is initiated in the post-synaptic (muscle) cell.- How can disruptions in this process result in muscle paralysis? muscle spasms?- Important Parts in the Neuromuscular Junction:- acetylcholine:neurotransmitter commonly associated with the neuromuscular junction- acetylcholine receptor : proteins within the cell membrane of the (post-synaptic) muscle that are specifically bonded to by acetylcholine molecules, leading to action potential propagation and muscle cell contraction- acetylcholinesterase :an enzyme (catalytic protein) that “patrols” the neuromuscular junction and regulates the amount of acetylcholine by degrading it- Atropine- extremely poisonous-found in the plant Belladonna-competes with acetylcholine for binding to acetylcholine receptors onmuscle cells- Half-life of 2 to 3 hours.- Muscles are paralysed by large doses, the paralysis finally affecting thecentral nervous system. Atropine also enters the central nervous system (CNS).- hallucinations, excitement, delirium, sedation and even unconsciousness- Medicinal uses: (In smaller doses, muscles are relaxed.)- eye exams--by optometrists for the dilation of the pupil- antidote:to nerve gas poisoning- Pre-medication for anesthesia as well as to lessen pain and inflammation. - Anti-spasmodic activity and is used for asthma and whooping cough. It is also used to revive a heart attack victim.3-View of Action Potential’s path from axon terminal to post-synaptic cell-4- Axon at rest potential- Na+ gates (yellow)K+ gates (blue)- Historical note:  15th Century manuscript depicting “witches”Atropine, a muscle-relaxant and paralytic drug,was allegedly used in “witches’ brews” by drug cults in medieval Europe and enabled the user to feel the sensation of “flying”. Extracts of the drug were applied using long sticks to rub it on the pulse points onthe hands and feet as well as the genitalia. Is the modern imagery of witches flying on broomsticks derived from this practice? Concentrated extracts of the Belladonna plant—the natural source of atropine—were used to carry out some assassinations during the Italian