Signal

Question 1

A ____ is a junction between two neurons, or between a neuron and an effector (muscle or gland)

Answer 1

synapse

Question 2

Synapses contribute to homeostasis by providing for evaluation and integration of ____

Answer 2

stimuli

Question 3

Synapses are physically ___ with repeated use (which includes learning)

Answer 3

changed

Question 4

Some diseases and disorders result from synaptic disruptions, and many therapeutic and addictive chemicals have their sites of action at ___

Answer 4

synapses

Question 5

The neuron sending the signal is the _____

Answer 5

presynaptic neuron

Question 6

The neuron receiving the message is the ____

Answer 6

postsynaptic neuron

Question 7

Most neurons, including all interneurons, function as both ___ and ____ neurons, receiving information from some neurons and conveying information to others

Answer 7

presynaptic

postsynaptic

Question 8

from axon to dendrite

Answer 8

axodendritic (slide 4)

Question 9

from axon to soma

Answer 9

axosomatic (slide 4)

Question 10

from axon to axon

Answer 10

axoaxonic (slide 4)

Question 11

The cells on each side of the synapse are in physical contact

Answer 11

Electrical synapses

Question 12

Action potential moves from one cell to the other as a flow of ions through ___

(Electrical synapses)

Answer 12

gap junctions

Ions flow from one cell to the other, conveying the action potential

Question 13

The cells on each side of the synapse are not in physical contact

Answer 13

Chemical synapses

Question 14

Action potential moves from one cell to the other by means of a ____ that bridges the gap between the two cells

(chemical synapses)

Answer 14

neurotransmitter

Question 15

Hundreds of ___ per gap junction connect the cytosol of the adjacent cells

(electrical synapse)

Answer 15

connexons

Electrical synapses are faster than chemical synapses

Electrical synapses can synchronize groups of neurons or muscle fibers

Question 16

Locations include muscle fibers of the heart and ____

electrical synapse

Answer 16

visceral smooth muscle

Question 17

Nerve impulse arrives at a synaptic end bulb of a presynaptic neuron

Depolarizing phase of the nerve impulse opens voltage-gated ___ channels, and Ca++ flows inward through the opened channels due to concentration differences

(Events at a chemical synapse pt. 1,2)

Answer 17

Ca++

Question 18

Increased intercellular Ca++ level within the presynaptic neuron triggers ___ of some of the synaptic vesicles, releasing neurotransmitter into the synaptic cleft

Neurotransmitter molecules diffuse across the synaptic cleft and bind to neurotransmitter receptors in the _____ plasma membrane

(Events at a chemical synapse pt. 3,4)

Answer 18

exocytosis

post-synaptic neuron’s

Question 19

Ligand-gated channels open, allowing ions to cross the membrane (here, Na+), changing the voltage and creating a postsynaptic ___

Threshold _____ postsynaptic potential triggers one or more nerve impulses

(Events at a chemical synapse pt. 5,6)

Answer 19

potential

depolarizing

Question 20

Neurotransmitters that depolarize the postsynaptic membrane cause an excitatory ___ potential because it brings the membrane closer to threshold

Answer 20

graded

Question 21

Neurotransmitters that cause hyperpolarization (further polarization) of the postsynaptic membrane are ____

Answer 21

inhibitory

Question 22

Typically result from opening of ligand-gated cation channels, the three most common cations being Na+, K+, and Ca++

Answer 22

Excitatory postsynaptic potential

EPSP

Question 23

A single EPSP does not normally initiate a nerve impulse, but the neuron does become more ____, and being partially depolarized is more likely to reach threshold at future EPSP arrival

Answer 23

excitable

Question 24

Typically result from opening of ligand-gated anion channels for Cl- or ligand-gated channels for K+, which then diffuse according to concentration gradients resulting in the inside becoming more negative (hyperpolarized)

Answer 24

Inhibitory postsynaptic potential (IPSP)

Question 25

Neurotransmitters must be ____ from the synaptic cleft for normal synaptic function

Answer 25

removed

Question 26

If neurotransmitters were not removed, they would continue to ___ the postsynaptic neuron, muscle fiber, or gland indefinitely

Answer 26

influence

Question 27

Diffusion Enzymatic degradation Uptake by the cells

Answer 27

Mechanisms of neurotransmitter removal

Question 28

acetylcholinesterase breaks down acetylcholine into acetyl and choline

Answer 28

Enzymatic degradtion, e.g.

Question 29

Termed reuptake if taken back up by the same cell that released the neurotransmitter Termed uptake if taken up by a cell that did not actually release it in the first place Neurotransmitter transporters are membrane proteins that accomplish the uptake

Answer 29

"uptake by the cells" most common mechanism of neurotransmitter removal

Question 30

The synaptic input is integrated (evaluated) by a process known as summation, which occurs at the ___

Answer 30

trigger zone

Question 31

The greater the summation of ____, the greater the chance that threshold will be reached, and that a nerve impulse will arise

Answer 31

EPSPs

Question 32

results from buildup of neurotransmitter released simultaneously by several presynaptic end bulbs (summation type)

Answer 32

spatial summation

Question 33

results from buildup of neurotransmitter released by a single presynaptic end bulb many times in rapid succession (summation type)

Answer 33

Temporal summation

Question 34

If the total excitatory effects are greater than total inhibitory effects, but still less than threshold the result is a sub-threshold EPSP, no ____, but partial depolarization may make a nerve impulse easier with additional stimuli

Answer 34

nerve impulse

Question 35

If the total excitatory effects are greater than total ___ effects, and threshold is reached, the result is generation of one or more nerve impulses

Answer 35

inhibitory

Question 36

If the total inhibitory effects are greater than the excitatory effects, the membrane ____, thereby inhibiting the ability of the postsynaptic neuron to generate a nerve impulse

Answer 36

hyperpolarizes

Question 37

Neurotransmitters are divided into two classes based primarily on size

Answer 37

Small-molecule neurotransmitters Neuropeptides

Question 38

Acetylcholine Amino acids Biogenic amines ATP and other purines Nitric oxide

Answer 38

Small molecule neurotransmitters

Question 39

Best studied neurotransmitter Released by many PNS neurons and some CNS neurons Excitatory at some synapses such as the previously-discussed neuromuscular junction where it opens ligand-gated cation channels Inhibitory at other synapses (specifics to be covered later in the course)

Answer 39

Acetylcholine Commonly abbreviated ACh

Question 40

Associated with central nervous system Most common excitatory examples are glutamate (glutamic acid) and aspartate (aspartic acid) Most common inhibitory examples are gamma aminobutyric acid (GABA) and glycine

Answer 40

Amino acids

Question 41

Nutritionally, they are found in a wide range of foods, and as exogenous amines they are directly absorbed in the intestine.

Answer 41

Biogenic amines As neurotransmitters, they are generally associated with the brain Depending on the type of receptor, biogenic amines may cause either excitation or inhibition (there are multiple receptor types for each biogenic amine)

Question 42

Histamine Serotonin

Answer 42

Classical monoamine neurotransmitters

Question 43

as a neurotransmitter it mediates arousal and attention, also a pro-inflammatory signal released from mast cells in response to allergic reactions or tissue damage

Answer 43

Histamine

Question 44

thought to be involved in sensory perception, temperature regulation, control of mood and appetite, and induction of sleep

Answer 44

Serotonin

Question 45

dopamine norepinephrine (noradrenaline) epinephrine (adrenaline)

Answer 45

Catecholamine neurotransmitters (type of biogenic amine)

Question 46

for brain neurons that are active during emotional responses, addictive behaviors, and pleasurable experiences, plus regulating skeletal muscle tone and skeletal muscle contractions

Answer 46

Dopamine

Question 47

used by some neurons of the brain, has roles in awakening from deep sleep, dreaming, and regulating mood. It is also a hormone produced by the adrenal medulla

Answer 47

Norephinephrine

Question 48

used by some neurons of the brain, and is also an adrenal medulla hormone

Answer 48

Epinephrine

Question 49

Formed on demand, rather than being synthesized and stored in synaptic vesicles Produced by endothelial cells in blood vessel walls, it is LIPID SOLUBLE and diffuses into neighboring smooth muscle cells causing them to relax, producing vasodilation

Answer 49

Nitric oxide

Question 50

neurotransmitters that comprise 3 to 40 amino acids (i.e. short chain amino acids) linked by peptide bonds widespread in both the CNS and PNS excitatory and inhibitory actions formed in the neuron cell body, packaged into vesicles, and transported to axon terminals also serve as hormones, regulating physiological responses elsewhere in the body

Answer 50

Neuropeptides

Question 51

Certain brain neurons have plasma membrane receptors for opiate drugs such as morphine and heroin

Answer 51

neuropeptides

Question 52

Naturally occurring neuropeptides that use those receptors are called opioid peptides, and include . . .

Answer 52

Enkephalins Endorphins Dynorphins

Question 53

A ___ is a functional group of neurons that processes a specific kind of information

Answer 53

neural circuit

Question 54

Simple series circuit Diverging circuit Converging circuit Reverberating circuit Parallel after-discharge circuit

Answer 54

neural circuit type

Question 55

One presynaptic neuron stimulates only a single postsynaptic neuron The postsynaptic neuron then stimulates another, etc. Most neural circuits are more complex than this

Answer 55

Simple series circuit

Question 56

A nerve impulse from a single presynaptic neuron causes the stimulation of increasing numbers of cells along the circuit (i.e. the action potential diverges) The effect is amplification of the original signal Sensory signals often spread into diverging circuits that are relayed to different parts of the brain

Answer 56

Diverging circuit slide 32

Question 57

A postsynaptic neuron receives nerve impulses from several different sources (i.e. the action potentials converge) The effect is more effective stimulation or inhibition of the postsynaptic neuron Motor neurons that synapse with skeletal muscle fibers may receive input from several pathways that originate in different parts of the brain

Answer 57

Converging circuit

Question 58

The incoming impulse stimulates the first neuron, which stimulates the second, which stimulates the third, etc Branches from later neurons loop back to synapse with earlier neurons, sending impulses back through the circuit many times

Answer 58

Reverberating circuit

Question 59

The reverberations may last seconds to hours Thought to be used in breathing, waking up, and short-term memory

Answer 59

Reverberating circuit

Question 60

One presynaptic input neuron has one output neuron with a variable number of intermediate neurons between input and output (and therefore variable number of synapses)

Answer 60

Parallel after-discharge circuit

Question 61

This imposes varying synaptic delays, so the last neuron exhibits multiple EPSPs or IPSPs

Answer 61

Parallel after-discharge circuit

Question 62

If the input is excitatory, the output neuron can send out a stream of impulses in quick succession

Answer 62

Parallel after-discharge circuit

Question 63

The nervous system exhibits ___ which is the ability to change based on experience and need

Answer 63

plasticity

Question 64

Individual neurons can sprout new dendrites, synthesize new proteins, and change the ___ of synapses

Answer 64

nature and number

Question 65

Neurons are generally not able to ____, that is to undergo mitosis and replicate, or to repair themselves to any great extent

Answer 65

regenerate

Question 66

___ dendrites and myelinated axons may be repaired if the cell body remains intact, and Schwann cells remain active

Answer 66

PNS

Question 67

Little or no repair of damage to neurons occurs in the __; generally even a severed axon can not be repaired or regrown

Answer 67

CNS

Question 68

The outer nucleated cytoplasmic layer of the Schwann cell, which encloses the myelin sheath, is the ____ (sheath of Schwann).

Answer 68

neurolemma

Question 69

``` When an axon is injured, the neurolemma aids regeneration by forming a ____ that guides and stimulates regrowth of the axon ```

Answer 69

regeneration tube

Question 70

To do any regeneration, neurons must be located in the ___, have an INTACT CELL body, and be MYELINATED by functional Schwann cells having a neurolemma

Answer 70

PNS

Question 71

refers to the loss or destruction of myelin sheaths around axons. It may result from disease, or from medical treatments such as radiation therapy and chemotherapy

Answer 71

Demyelination Any single episode of demyelination may cause deterioration of affected nerves

Question 72

In axons that are normally myelinated, voltage-gated channels are concentrated (or exclusively present) only at ____. Myelin insulates the neuron and allows the current to spread further before it attenuates. Destruction of myelin means the current does not spread as far, and therefore does not reach the next concentration of voltage-gated channels

Answer 72

nodes of Ranvier

Question 73

an autoimmune disease that causes progressive destruction of myelin sheaths in the CNS

Answer 73

Multiple Sclerosis Multiple regions of myelin sheaths deteriorate to scleroses (hardened scars or plaques) Destruction of the myelin sheaths first slows, then short circuits nerve impulse propagation

Question 74

demyelinating disorder in which macrophages strip myelin from axons in the PNS

Answer 74

Guillain-Barré syndrome May result from the immune system’s response to a bacterial infection

Question 75

The discharges stimulate neurons to send spontaneous impulses, resulting in the perception of lights, noises, and smells that do not exist and for which the corresponding sense organ has not been stimulated; skeletal muscles may also contract involuntarily; not all seizures are dramatic

Answer 75

Epilepsy Manifests in epileptic seizures, which are commonly described “an electrical storm in the brain”

Question 76

A fatal disease caused by a virus that reaches the CNS via fast axonal transport Usually transmitted by the bite of a dog or other meat-eating animal Symptoms are excitement, aggressiveness, and madness, followed by paralysis and death

Answer 76

Rabies

Question 77

They act by blocking the opening of voltage-gated Na+ channels, thereby preventing transmission of pain signals

Answer 77

Local anesthetics