Nervous System Mb, Biol 1620

Front 1

The Fundamental excitable cell in the nervous system is the ___

Back 1

Neuron

Front 2

The knee-jerk reflex has sensory neurons arisiong in the ___, interneurons in the _____, and efferent neurons that stimulate contraction in the _____

Back 2

Quadriceps muscle... spinal cord... hamstring muscle

Front 3

The cerebrospinal fluid is____

Back 3

A filtrate of the blood

Front 4

A neuron's nucleus is located in its ____

Back 4

Cell body (The cell body is the region of a neuron where the nucleus is found)

Front 5

A nerve impulse moves toward a neuron's cell body along ______

Back 5

Dendrites ( Dendrites conduct an impulse from a synapse toward the cell body.

Front 6

A nerve impulse moves away from a neuron's cell body along ____

Back 6

Axons (Axons conduct a nerve impulse away from the cell body

Front 7

An impulse relayed allong a myelinated axon "jumps" from _______ to ________

Back 7

Node of Ranvier.... Node of Ranvier

Front 8

Axons insulated by a(n)____ are able to conduct impulses faster then those not so insulated

Back 8

Myelin sheath (Myellin sheaths, formed when schwann cells wrap around an axon, allow such neurons to conduct impulses more rapidly then unmyelinated axons)

Front 9

What type of cell makes up the myelin sheath of a motor neuron?

Back 9

Schwann cells (myelin sheaths are formed when schwann cells wrap around the axons of motor neurons.)

Front 10

What part of a neuron relays signals from one neuron to another neuron or to an effector?

Back 10

Synaptic terminal (synaptic terminals contain neurotransmitter molecules that relay the nerve impulse across a synapse.

Front 11

The "information receiving" section of neuron is its _____

Back 11

Dendrites (the dendrites have receptor proteins that receive information by binding chemical messages called neurotransmitters)

Front 12

Most of the neurons in the human brain are ____

Back 12

Interneurons

Front 13

In a simple synapse, neurotransmitter chemicals are released by _____________.

Back 13

the presynaptic membrane

Front 14

Which term describes the difference in electrical charge across a membrane?

Back 14

Membrane potential (membrane potential is the difference in electrical charge across a membrane)

Front 15

Resting neurons are most permeable to which of ion?

Back 15

K+ (resting neurons are most permeable to K+ ions

Front 16

True or False? The potential energy of a membrane potential comes solely from the difference in electrical charge across the membrane.

Back 16

FALSE (the potential energy of a membrane potential comes both from the difference in electrical charge and from the concentration gradient of ions across a membrane

Front 17

Which channel is mainly responsible for the resting potential of a neuron?

Back 17

Potassium Leak Channel (K+ ions flow along their concentration gradient to maintain the resting potential of a neuron

Front 18

Which term describes an electrical signal generated by neurons?

Back 18

Action potential. (An action potential is a rapid electrical signal generated by neurons)

Front 19

Which channel maintains the concentration gradients of ions across a neuronal membrane?

Back 19

The sodium-potassium pump moving NA_ ions out and K+ ions in

Front 20

What behavior is observed if the voltage across a neuronal membrane is set to -20 mV

Back 20

The sodium channel opsn, the Na+ ions flow in (sodium ions flow into the cell when the membrane potential is between -20mV and 30 mV

Front 21

the operation of the sodium-potassium "pump" moves _____

Back 21

Sodium ions out of the cell and potassium ions into the cell

Front 22

The membrane potential in which there is no net movement of the ion across the membrane is called the _____

Back 22

Equilibrium potential

Front 23

two fundamental concepts about the ion channels of a "resting" neuron are that the channels _____

Back 23

open and close depending on stimuli, and are specific as to which ion can traverse them

Front 24

Which structure is NOT part of a neuron?

-cell body

-axons

-dendrite

-myellin sheath

Back 24

Myelin sheath (the myelin sheath is the layer of schwann cell wrapped around a neuron

Front 25

Which of the following statements about action potentials in a given neuron is FALSE?

-they are identical in magnitude

-they occur after the threshold potential is reached

-they are propogated down the length of the dendrite

-the are identical in magnitude

Back 25

They are propogated down the length of the dendrite

Front 26

True or False? action potentials travel in only one direction down an axon because potassium channels in the neuron are refractory and cannot be activated for a short time after they open?

Back 26

False. (action potentials travel in only one direction down an axon because sodium channels in the neuron are refactory.

Front 27

Which event triggers the creation of an action potential?

Back 27

The membrane depolarizes above a certain threshold potential. (Influx of Na+ ions into the neuron can lead to membrane depolarization above the threshold potential; this event triggers the creation of an action potential.

Front 28

Which of the following terms describes how a neuronal membran's potential is altered in the presence of inhibitory signals?

-polarization

-depolarization

-repolarization

-hyperpolarization

Back 28

Hyperpolarization (inhibitory signals hyperpolarize the membrane and make the membrane potential even more negative then normal

Front 29

Where in teh neuron do action potentials begin?

Back 29

Axon hillock (the axon hillock is the region where voltage-gated channels begin in a neuron, near the cell body

Front 30

How is an action potential propagated down an axon after voltage-gated sodium channels open in a region of the neuron's membrane?

Back 30

Sodium ions enter the neuron and diffuse to adjacent areas, resulting in the opening of voltage-gated sodium channels farther down the axon.

Front 31

A neuron has a resting potential of about _____ millivolts

Back 31

-70 (this is the resting potential, the charge difference found across the plasma membrane of a "resting" neuron

Front 32

An action potential moves along A(n) ____

Back 32

Axon (an axon is the only portion of a neuron cabable of generating an action potential.

Front 33

At rest, what plays a role in establishing the charge differential across a neuron's plasma membrane??

Back 33

The sodium-potassium pump moving sodium ions out of the neuron and potassium ions into the neuron

Front 34

The transmission of a nerve impulse first triggers the _____________________

Back 34

opening of voltage-gated sodium channels and the diffusion of sodium ions into the neuron

Front 35

A stimulus has opened the voltage-gated sodium channels in an area of a neuron's plasma membrane. As a result, _____________ ruses into the neuron and diffuses to adjacent areas; this in turn results in the ___________ in the adjacent areas

Back 35

sodium..... opening of voltage-gated sodium channels

Front 36

A graded hyperpolarization of a membrane can be induced by _____.

Back 36

Increasing its membrane's permeability to K+

Front 37

AFter the depolarization phase of an action potential, the resting potential is restored by _____.

Back 37

The opening of voltage-gated potassium channels and the closing of sodium channels.

Front 38

The "undershoot" phase of after-hyperpolarization is due to _____

Back 38

sustained opening of voltage-gated potassium channels

Front 39

Why are action potentials usually conducted in one direction?

Back 39

The brief refractory period prevents reopening of voltage-gated Na+ channels.

Front 40

Why do Na+ ions enter the cell when voltage-gated Na+ channels are opened in neurons

Back 40

Because the Na+ concentration is much higher outside the cell than it is inside, and the Na+ ions are attracted to the negatively charged interior

Front 41

Which of the following will increase the speed of an action potential moving down an axon?

1. action potentials move faster in larger diameter axons

2. action potentials move faster in axons lacking potassium ion channels.

3. action potentials move faster in myelinated axons

Back 41

Only 1 and 3

Front 42

What causes the release of neurotransmitter molecules?

Back 42

An action potential reaching the end of the axon

Front 43

the space between an axon of one neuron and the dendrite of another neuron is called a(n) __________.

Back 43

Synaptic cleft ("Synaptic cleft" is the name given to the space between two neurons that meet at a synapse

Front 44

Neurons store neurotransmitter molecules in vesicles located within ____.

Back 44

synaptic terminals

Front 45

A nerve poison that blocks acetylcholine receptors on dendrites would _____.

Back 45

Reduce the pinding of acetylcholine to its receptors on the postsynpatic membrane

(the binding of neurotransmitter molecules to their specific receptors on the postsynaptic membrane opsn ion channels, whcih complets the transmission of the impulse to the receiving cell. A nerve poison that blocked the acetylcholine receptors would prevent reception of the signal)

Front 46

The following steps refer to various stages in transmission at a chemical synapse:

1. neurotransmitter binds with receptors associated with the postsynaptic membrane.

2. calcium ions rush into neuron's cytoplasm.

3. an action potential depolarizes teh membrane of the presynaptic axon terminal.

4. the ligand-gated ion channels open

5. the synaptic vesicles release neurotransmitter into teh synaptic cleft.

Which sequence of events is correct?

Back 46

3 -> 2 -> 5 -> 1 -> 4

Front 47

When two excitatory postsynaptic potentials (EPSPs) occur at a signle synapse so rapidly in succession that the postsynaptic neuron's membrane potential has not returned to the resting potential before the second EPSP arrives, the EPSPs add together producing _______.

Back 47

Temporal summation

Front 48

What is a DIRECT result of depolarizing the presynaptic membrane of an axon terminal??

Back 48

Voltage-gated calcium channels in the membrane open.

Front 49

Suppose a particular neurotransmitter causes an IPSP in postsynaptic cell X and an EPSP in postsynaptic cell Y. A likely explanation is that _______________.

Back 49

Cells X and Y express different receptor molecules for this particular neurotransmitter

Front 50

The plasma membrane of a neuron has voltage-gated sodium and potassium channels. What is the effect of membrane depolarization on these channels?

Back 50

Membrane depolarization first opens sodium channels and then opens potassium channels.

(Membrane depolarization opens both types of channels, but they respond independently and sequentially. Sodium channels open first, initiating the action potential. As the action potential proceeds, the sodium channels become inactivated and remain inactivated until after the membrane returns to the resting potential and the channels close. Potassium channels open more slowly than sodium channels but remain open and functional throughout the action potential. Read about the generation of action potentials.)

Front 51

ne of the fundamental processes by which memories are stored and learning takes place _____.

Back 51

involves two types of glutamate receptors