BIOL 3240 Exam 2 | Complete Solutions (Verified)

BIOL 3240 Exam 2 | Complete Solutions (Verified) The process whereby a neuron communicates with another cell, which can be another neuron or a muscle cell Synaptic transmission Who was the first person to coin the term "synapse?" Charles Sherrington The region between pre and post synaptic cells zone of apposition (chemical/electrical) synapses are used to generate rapid and stereotyped depolarizing signals Electrical (chemical/electrical) synapses are capable of variable signaling, mediating either excitatory or inhibitory signals Chemical Chemical synapses can mediate excitatory or inhibitory signals and changes in ____ properties to the postsynaptic cell Electrical What protein helps stabilize synapses and the pre/post synaptic cells at this junction? Connexin In an electrical synapse, what is the distance between pre and postsynaptic cell membranes? 4 nm (chemical/electrical) synapses have cytoplasmic continuity between the pre and postsynaptic cells Electrical What is the distance between pre and post synaptic cell membranes in a chemical synapse? 20 to 40 nm What is the agent of transmission in an electrical synapse? Ion current The structural cellular component responsible for passing the agent of transmission in an electrical synapse Gap junction The structural cellular component responsible for passing the agent of transmission in a chemical synapse vesicles, active zones, postsynaptic receptors Which type of synapse has a more significant synaptic delay, chemical or electrical? Chemical How long is the synaptic delay of a chemical synapse? 1-5 ms The direction of transmission of an electrical synapse Bidirectional The direction of transmission of a chemical synapse Unidirectional At an electrical synapse, when an outward current in the presynaptic cell is strong enough, some of the current can enter the postsynaptic cell through... gap junctions In an electrical synapse, the presynaptic neuron has to generate a large enough current to do what? depolarize both presynaptic and postsynaptic cells In an electrical synapse, why is the postsynaptic cell typically smaller than the presynaptic cell? to be depolarized by the current that also depolarizes the presynaptic cell A gap junction channel consists of a pair of ____ _____, creating a pore between the neurons hemi channels [Gap junction structure] Each hemi channel consists of what type of protein subunit? How many? 6, connexin Electrically coupled cells generally have (higher/lower) thresholds Higher Electrical synapses have very short to almost no synaptic delay. What are the firing patterns of electrically coupled cells? they fire synchronously A presynaptic cell at a chemical synapse can contain between ___ to ____ vesicles 100 to 200 Synaptic vesicles are clustered at the ____ _____ - a structure in the presynaptic terminal active zone Specialized structure in the presynaptic terminal where vesicles cluster (chemical synapse) active zone When the action potential reaches a presynaptic site, what channels open? What ion flows inside the presynaptic zone? Ca2+ voltage gated channels When intracellular concentration of this ion rises prior to synaptic release, this causes the vesicles to fuse with the presynaptic membrane Ca2+ What is the effect of the rise of intracellular Ca2+ concentration in the presynaptic neuron, at the synapse? fusion of vesicles to the presynaptic membrane, release of neurotransmitters into the cleft If the neurotransmitter receptor is a Na+ ion channel, will the postsynaptic neuron depolarize or hyperpolarize in response to the neurotransmitter release? Depolarize If the neurotransmitter receptor is a Na+ ion channel, is the neurotransmitter excitatory or inhibitory? Excitatory If the neurotransmitter receptor is a Cl- ion channel, will the postsynaptic neuron depolarize or hyperpolarize in response to the neurotransmitter release? Hyperpolarize If the neurotransmitter receptor is a Cl- ion channel, is the neurotransmitter excitatory or inhibitory? inhibitory, depending on the membrane potential of the postsynaptic neuron What are the two features of all neurotransmitter receptors? 1. they are membrane proteins; 2. they have an effector function Ionotropic neurotransmitter receptors are what type of ion channel? ligand gated How many subunits make up an ionotropic receptor? 4 to 5 Metabotropic receptors require ____ proteins and _____ messengers to indirectly modulate ionic activity in a post synaptic cell G; secondary A G protein receptor would be necessary to open what type of neurotransmitter receptor? Metabotropic Neuromodulators, which act more diffusely on cells that are not necessarily connected to the releasing neuron, act through what type of post synaptic receptor? Metabotropic Although chemical transmission lacks the speed of electrical transmission, it has an ______ property Amplification A small presynaptic nerve terminal can depolarize a large postsynaptic cell because of what feature of chemical transmission? one synaptic vesicle is sufficient to release thousands of neurotransmitter molecules A motor neuron innervates a muscle fiber at a specialized region of the muscle membrane, a.k.a. the end plate At the end plate, the motor axon loses its ____ _____ and splits into several fine _____ myelin sheath; branches The motor neuron, at the end plate, splits into multiple varicosities called ______ _____, from which the neurotransmitter ______ is released synaptic boutons; acetylcholine [Neuromuscular junction] Where are synaptic boutons positioned at the synaptic cleft to be able to carry out chemical transmission? the junctional fold [Neuromuscular junction] What does the junctional fold contain? nicotonic acetylcholine receptor How wide is the synaptic cleft in the neuromuscular junction? 100 nm What is the synaptic cleft at the neuromuscular junction full of? collagen, extracellular matrix, acetylcholinesterase The enzyme that hydrolyses acetylcholine Acetylcholinesterase EPSP stands for excitatory post synaptic potential How large is the EPSP or end plate potential in the neuromuscular junction? 70 mV Which is larger, an EPSP generated at the neuromuscular end plate, or one generated by a neuron in the brain? end plate What is the difference between a graph of an AP in a neuron vs an AP in a muscle? Muscle fiber action potentials have slower K+ channel opening, no hyperpolarization, and lower resting potential What is the resting potential of a muscle fiber? -90 mV What two scientists studied the end plate potential, using curare to isolate resting potential vs. muscle fiber action potentials? Paul Fatt and Bernard Katz Which ion species are acetylcholine receptors permeable to? Na+, K+ The potential at which the sign of the current reverses reverse potential What is the reverse potential of the acetylcholine receptor? 0 mV A reverse potential of 0 mV indicates that the acetylcholine receptor (is/is not) selective is not What is the difference between a voltage gated ion channel and the acetylcholine receptor, structurally? What ions can the receptor accommodate? the receptor has a larger pore; Na+, K+, Ca2+ The end plate potential of a muscle cell rises ____ and decays ____ rapidly, slowly Why is there a slow decay of end plate potential in a muscle fiber? hydrolysis of acetylcholine by acetylcholinesterase T or F: the acetylcholine-gated channels and voltage-gated channels belong to the same gene family False How many subunits make up the acetylcholine-gated channel? 5 How many acetylcholine binding sites are there on the acetylcholine-gated channel? 2 Most mature muscle fibers are innvervated by how many motor neurons? 1 T or F: a motor neuron can innvervate different muscles True A comprehensive map of neuronal connections in a brain Connectome muscle fibers receive only ____ inputs excitatory Most interneurons receive both _____ and _____ inputs excitatory, inhibitory End plate potentials are mediated by the binding of ______ to its receptor Acetylcholine The neuromuscular junction is an _____ synapse. Synapses in the brain are not as efficient Efficient One AP in the presynaptic neuron, the motor neuron, is (sufficient/insufficient) to generate an AP in the post synaptic cell, the muscle fiber Sufficient Several action potentials need to be simultaneously generated in as many as ___ to ____ presynaptic neurons for an AP to be generated in a postsynaptic neuron (in the brain) 50 to 100 In this muscle pair, when one muscle contracts, the other relaxes antagonistic muscle pair What two muscles make up the antagonistic muscle pair in the stretch reflex of the leg muscles? quadriceps, biceps The antagonistic action of muscle pairs depends on the ability of motor neurons to do what? integrate excitatory and inhibitory inputs Without an inhibitory input, how would a neuron behave? fire continuously at a fixed interval ______s can sculpt pattern of firing in neurons that fire spontaneously at a given interval IPSP information can be encoded in neurons firing at fixed intervals through inhibition Whether a given neurotransmitter generates an excitatory or inhibitory current depends not on the neurotransmitter, but on the type of ________ found in the postsynaptic terminal ligand gated channels Glutamate produces what type of currents? Excitatory GABA produces what type of currents? Inhibitory glycine produces what type of currents? Inhibitory _____ ____ ___ synapses have asymmetrical membrane differentiations, due to an electron dense region at the active zone of the presynaptic membrane, and a more dense region at the post synaptic membrane Gray type 1 What type of synapse is characterized by round vesicles? Type 1 What type of synapse usually contacts a spine on a dendrite? Type 1 Specialized regions on dendrites where type 1 synapses usually make contact Spine This type of synapse is often glutamatergic and excitatory Type 1