BIO212-004 Exam 2: Ch. 11

Metabotropic Receptors

found within plasma membrane associated with a separate ion channel; directly connected to metabolic processes that are initiated when neurotransmitter binds

Neurotransmitter release from vesicles of the synaptic terminus results from a. influx of calcium into synaptic terminus b. efflux of calcium out of synaptic terminus c. influx of sodium into synaptic terminus d. efflux of sodium out of synaptic terminus

a. influx of calcium into synaptic terminus

Action potential arrival at the synaptic terminus causes a. opening of voltage-gated calcium channels b. opening of voltage-gated sodium channels c. opening of voltage-gated potassium channels d. opening of voltage-gated chloride channels

a. opening of voltage-gated calcium channels

The correct order for events at a chemical synapse is

action potential arrives at axon terminus, neurotransmitter is released, neurotransmitter binds to receptors, local potential occurs in postsynaptic cell

The correct sequence of major events during chemical synaptic transmission

action potential, synaptic transmission, postsynaptic potentials, synaptic transmission termination

Synaptic Transmission is BIDIRECTIONAL (electrical synapses)

either neuron may act as the presynaptic or the postsynaptic neuron and that current may flow in either direction between the two cells

Synaptic Vesicles

filled with chemical messengers (NEUROTRANSMITTERS) that transmit signals from presynaptic to postsynaptic neurons are found at CHEMICAL SYNAPSES

Neurotransmitter Receptors

found in postsynaptic neuron; bind to neurotransmitter secreted from presynaptic neuron that has diffused across synaptic cleft

Spatial Summation

involves simultaneous release of neurotransmitters from axon terminals of many presynaptic neurons

Postsynaptic potentials

local potentials found in membranes of postsynaptic neuron

Chemical Synapse

make up majority of synapses in nervous system; more efficient than electrical synapses because they convert electrical signals into chemical signals so no signal strength is lost

Postsynaptic Neuron

neuron RECEIVING messages from presynaptic neuron at its cell body, axon or dendrites

`Presynaptic Neuron

neuron SENDING message from its axon terminals

Temporal Summation

neurotransmitter is released repeatedly from axon terminal of a single presynaptic neuron; each local potential (EPSP) is short-lived so they must be generated quickly to reach threshold and create action potential

Electrical Synapse

occurs between cells that are electrically coupled via gap junctions -Gap junctions align channels that form PORES that ions or other small substances can flow through -breathing

Summation

phenomenon whereby all input from several postsynaptic potentials are added together (EPSPs+IPSPs) to affect membrane potential trigger zone

Neural integration

process in which postsynaptic neuron integrates all incoming information into a single effect

Ionotropic receptors

receptors found as components of a ligand-gated ion channels; directly control movement of ions into or out of neuron when they bind to neurotransmitter

Synaptic Cleft

small ECF-filled space; separates presynaptic and postsynaptic neurons; found in CHEMICAL SYNAPSES; GAP JUNCTIONS connect neurons in ELECTRICAL SYNAPSES

Acetylcholine (ACh)

small molecule neurotransmitter widely used by nervous system

Synaptic Transmission is nearly INSTANTANEOUS (electrical synapses)

the delay between depolarization of the presynaptic neuron and change in potential of the postsynaptic neuron is less that 0.1 ms *10x faster than a chemical synapse

Synapse

where a neuron meets its target cell called a NEURONAL SYNAPSE -can be electrical or chemical

EPSPs a. are inhibitory b. move the postsynaptic membrane toward threshold c. result from potassium channels opening d. are usually large local potentials

b. move the postsynaptic membrane toward threshold

Which of the following is NOT a method for termination of synaptic transmission? a. diffusion and absorption b. receptor fatigue c. reuptake into presynaptic neuron d. degradation in synaptic cleft

b. receptor fatigue

There are 3 structural differences between Electrical and Chemical Synapses

1. Synaptic Vesicles 2. Synaptic Cleft 3. Neurotransmitter Receptors

Chemical Synapse

1. an action potential in presynaptic neuron triggers voltage-gated calcium ion channels in axon terminal to open 2. influx of calcium ions causes synaptic vesicles to release neurotransmitters into synaptic cleft 3. neurotransmitters bind to receptors on postsynaptic neuron 4. ion channels open, leading to a local potential and possibly an action potential if threshold is reached

Three main amino acid neurotransmitters

1. glutamate 2. glycine and GABA 3. neuropeptides -subastance p -opioides -neuropeptide y

Two events that can occur with postsynaptic potentials

1. membrane potential of postsynaptic neuron moves closer to threshold; caused by a small depolarization call an EXCITATORY POSTSYNAPTIC POTENTIAL (EPSP) 2. membrane potential of postsynaptic neuron moves farther away from threshold; caused by a small local hyperpolarization call an INHIBITORY POSTSYNAPTIC POTENTIAL (IPSP)

Synaptic transmission may be terminated by ending effects of neurotransmitter in one of three methods

1. some neurotransmitters diffuse away from synaptic cleft in ECT; can be reabsorbed into a neuron or an astrocyte 2. neurotransmitter can be broken down in synaptic cleft by enzymes; by-products of reaction can be reabsorbed by presynaptic membrane for reassembly of original neurotransmitter 3. some neurotransmitters are reabsorbed into presynaptic neurons by a process called REUPTAKE

2 types of Summation

1. temporal summation 2. spatial summation

IPSPs a. are inhibitory b. move the postsynaptic membrane toward threshold c. result from sodium channels opening d. are usually large local potentials

a. are inhibitory

Postsynaptic potentials a. are always inhibitory b. always move the postsynaptic membrane toward threshold c. depend on which membrane channels open d. only involve sodium channel opening and closing

c. depend on which membrane channels open

Neurotransmitter binding to receptors on the postsynaptic membrane a. opens or closes ligand-gated calcium channels b. opens or closes voltage-gated sodium channels c. opens or closes ligand-gated sodium channels d. opens or closes voltage-gated potassium channels

c. opens or closes ligand-gated sodium channels

Synaptic Transmission is UNIDIRECTIONAL (chemical synapses)

chemical synapses travel in only one direction, unlike electrical synapses; allow for variable signal intensities

Biogenic Amines (monoamines)

class of five neurotransmitters synthesized from amino acids; used throughout CNS and PNS for many functions such as regulation of homeostasis and cognition 1.Norepinephrine 2.Epinephrine 3.Dopamine 4.Serotonin 5.Histamine

Axoaxonic Synapses

connection between axon and axon

Axosomatic Synapses

connection between axon and cell body

Axodedritic Synapses

connection between axon and dendrite

Termination of synaptic transmission is necessary because a. presynaptic neurons will run out of neurotransmitter b. receptor fatigue will occur c. effect of neurotransmitter is not longer needed d. postsynaptic response cannot be reinitiated until first response is terminated

d. postsynaptic response cannot be reinitiated until first response is terminated

Synaptic Delay

time gap between arrival of action potential at axon terminal and effect on postsynaptic membrane

Synaptic Transmission

transfer of chemical or electrical signals between neurons at a synapse -allows for voluntary movement, cognition, sensation and emotions -a presynaptic neuron forms synapses with about 1000 postsynaptic neuron -a postsynaptic neuron can have as many as 10000 synaptic connections with different presynaptic neurons