7 Electrochemical Basis of Neuronal Function

Question 1

The potential of inactive cells is called

Answer 1

resting membrane potential

Question 2

-when the neuron receives excitatory or inhibitory signals, the neuronal membrane generates this

-In response to neurotransmitters from presynaptic neurons, brief local changes in postsynaptic membranes are generated at each synaptic site. These local membrane potentials are referred to as

-amplitude is directly proportional to the intensity of the stimulus applied at synaptic sites.

Answer 2

Graded potentials

Question 3

neuronal membrane undergoes a reversal of membrane potential called the

Answer 3

action potential

Question 4

-caused by an ion concentration difference on the two sides of the membrane.

-Because of the unequal concentrations of ions across a membrane, the membrane has an electrical charge.

Answer 4

Membrane potentials

Question 5

how many millivolts is the resting membrane potential of a neuron

Answer 5

–90 millivolts

Question 6

ions move down their gradients via ____ creating RMP.

-are open in the resting neurons

Answer 6

leak channels

Question 7

-this pump moves ions against a chemical gradient.

-makes a small direct contribution to the resting membrane potential. The net membrane potential with all these factors operative at the same time is about –90 millivolts.

Answer 7

Na+-K+ Pump

Question 8

Shifting the membrane potential toward a more positive is called

Answer 8

depolarization

Question 9

a depolarizing graded potential is referred to as

Answer 9

excitatory postsynaptic potential (EPSP)

Question 10

Shifting the membrane potential toward a more negative is called

Answer 10

hyperpolarization

Question 11

A hyperpolarizing graded potential is called an

Answer 11

inhibitory postsynaptic potential (IPSP)

Question 12

synapses that induce IPSPs are called

Answer 12

inhibitory synapses

Question 13

Numerous presynaptic axons converge on a postsynaptic neuron, generating thousands of EPSPs and IPSPs that may converge forming what

Answer 13

Summation

Question 14

two modes of summation,

Answer 14

spatial summation

temporal summation

Question 15

graded potentials induced by different synapses summate in the postsynaptic dendrites and cell body.

Answer 15

spatial summation

Question 16

graded potentials induced by the successive action of presynaptic terminals summates in the postsynaptic neuron.

Answer 16

temporal summation

Question 17

-Rapid changes in the membrane potential that spread rapidly along the nerve fiber membrane generate an action potential or neuronal firing.

-sudden change from the normal resting negative membrane potential to a positive potential and then ends with an almost equally rapid change back to the negative potential.

Answer 17

Nerve Action Potential

Question 18

Stages of the action potential

Answer 18

1. Resting Stage.
2. Depolarization Stage.
3. Repolarization Stage.

Question 19

principles in the propagation of action potential

Answer 19

1. Passive conduction
2. Saltatory conduction
3. All-or-Nothing Principle.
4. Plateau in Some Action Potentials.
5. Rhythmicity of some excitable tissues-repetitive discharge.

Question 20

*principles in the propagation of action potential

will ensure that the adjacent membrane depolarizes, so the action potential “travels” down the axon. But transmission by continuous action potentials is relatively slow and energy-consuming (Na+/K+ pump).

Answer 20

Passive conduction

Question 21

*principles in the propagation of action potential

is a faster mechanism that utilizes the myelination of nerves. Large nerve fibers are myelinated meaning they are covered with myelin sheath provided by the oligodendrocytes and Schwann cells. In between these sheaths are the presence of the node of Ranvier. Action potential travel only in the nodes which increases the velocity of nerve transmission in myelinated fibers as much as 5- to 50-fold.

Answer 21

Saltatory conduction

Question 22

*principles in the propagation of action potential

Once an action potential has been elicited at any point on the membrane of a normal fiber, the depolarization process travels over the entire membrane if conditions are right, or it does not travel at all if conditions are not right.

Answer 22

All-or-Nothing Principle.

Question 23

is the period of time it takes for an excitable membrane to be ready for a second stimulus once it returns to its resting state following excitation.

Answer 23

Refractory Period

Question 24

is a special site of contact, where one neuron communicates with others.

Answer 24

synapse

Question 25

-The transfer of signals from one neuron to another via synapses is called

-also occurs between motor neurons (somatic, visceral) and their target tissues (skeletal muscle, cardiac muscle, smooth muscle, glands).

Answer 25

synaptic transmission

Question 26

two distinct classes of synapses

Answer 26

electrical and chemical

Question 27

the majority of synapses present in the mammalian nervous system are

Answer 27

chemical synapses

Question 28

synapse wherein ion channels connect the cytoplasm of the presynaptic and postsynaptic cells at a gap junction, allowing ionic current to flow passively through the gap junction pores from one neuron to another.

Answer 28

electrical synapse,

Question 29

synapse wherein it has no gap junctions. Instead, there is a narrow space, called the synaptic cleft, between the presynaptic and postsynaptic membrane.

Answer 29

chemical synapse

Question 30

Neurotransmitters present in the peripheral nervous system (PNS) are

Answer 30

acetylcholine (ACh)

norepinephrine

epinephrine.

Question 31

what are the excitatory neurotransmitters of the CNS.

Answer 31

Glutamate

Aspartate

Question 32

The primary inhibitory neurotransmitters in the CNS are

Answer 32

GABA

Glycine

Question 33

Receptors for neurotransmitters

Answer 33

1. Cholinergic receptors.
2. Adrenergic receptors.
3. Glutamate receptors.

Question 34

One motor neuron innervates a group of skeletal muscle fibers. This unit comprising a motor neuron and the muscle fibers it innervates is known as a

Answer 34

motor unit

Question 35

Nerve impulses to skeletal muscle fibers are mediated by a ____ (also referred to as neuromuscular junction).

Answer 35

neuromuscular synapse