Chapter 11

Question 1

Hyperpolarization

Answer 1

When the membrane potential becomes more negative and is the movement of the membrane potential further away from zero

Question 2

Hypopolarization

Answer 2

in neurochemical transmission of nerve impulses this is decreased polarity of the postsynaptic membrane, e.g. that caused by excitation from receptor stimulation.

Question 3

repolarization

Answer 3

is the return of the ions to their previous resting state, which corresponds with relaxation of the myocardial muscle

Question 4

Explain the two functions of nervous tissue

Answer 4

Irritability Conductivity

Question 5

What is irritability function of neurons?

Answer 5

This is the ability to respond to a stimulus and convert it into a nerve impulses

Question 6

What is conductivity function of neurons?

Answer 6

This is the ability to transmit the impulse to other neurons, muscles, or glands

Question 7

Describe the three different kinds of neurons, functionally and structurally.

Answer 7

Sensory Neurons

Motor Neurons

Interneurons

Question 8

Describe the three components of a neuron.

Answer 8

Neuron Cell body

Dendrites

Axons

Question 9

Sensory Neurons

Answer 9

Conduct action potentials toward the CNS

Question 10

Motor Neurons

Answer 10

Conduct action potentials away from CNS toward muscles or glands

Question 11

Interneurons

Answer 11

conduct actions potentials from one neuron to another within the CNS

Question 12

Neuron Cell Body

Answer 12

Has the nucleus-source of information, and protein synthesis - done in the nissl bodies

Question 13

Structure of a Typical neuron

Answer 13

Question 14

Dendrites

Answer 14

These are neuron processes that convey incoming messages (electrical signals) toward the cell body

Question 15

Axon

Answer 15

These are neuron processes that generate nerve impulses and typically conduct them away from the cell body

Question 16

Axon Hillock

Answer 16

This is the conelike region of the cell body

Question 17

What are axon terminals?

Answer 17

This is where axons end
These contain vesicles with neurotransmitters
They are also separated from the next neuron by a gap

Question 18

What are neurotransmitters?

Answer 18

These are chemicals that is contained in the terminals’ tiny vesicles

Question 19

What is the synaptic cleft?

Answer 19

This is the gap between adjacent neurons

Question 20

What is a synapse?

Answer 20

Theses are the functioning junctions between the nerves

Question 21

What is myelin?

Answer 21

This is the whitish, fatty material (which has a waxy appearance) covering most long nerve fibers. This protects and insulates the fibers and increases the transmission rate of nerve impulses.

Question 22

What are schwann cells?

Answer 22

These produce myelin sheaths in jelly-roll like fashion

Question 23

What are myelin sheaths?

Answer 23

This is a tight coil of wrapped membranes enclosing the axon.

Question 24

Describe the various kinds of neuroglia.

Answer 24

Astrocytes

Ependymal Cells

Mycroglia

Oligodendrocytes

Schwann Cells

Satellite Cells

Question 25

Astrocytes

Answer 25

star shaped cytoplasmic extensions end in foot processes extensive cytoskeleton help regulate ECF composition of brain fluid the blood-brain barrier They have other functions

Question 26

Ependymal Cells

Answer 26

line the ventricles of the brain and the central canal of the cord their free surfaces have cilia the choroid plexes (secrete the cerebrospinal fluid)

Question 27

Microglia

Answer 27

become mobile and phagocytic in response to inflammation

Question 28

Oligodendrocytes

Question 29

Schwann cells

Answer 29

form myelin on peripheral neurons

Question 30

Satellite cells

Answer 30

provide support, nutrition and protection of cell bodies

Question 31

The electrical properties of neurons are due to:

Answer 31

Ion concentration differences across the cell membrane Permeability characteristics of the membrane

Question 32

Differences in the intra- and extra-cellular concentrations are due to:

Answer 32

Sodium-Potassium pump Permeability characteristics of the membrane

Question 33

Two ion channels

Answer 33

leak ion (nongated) channels gated ion channels: a. ligand-gated ion channels b. voltage-gated ion channels c. other-gated ion channels

Question 34

Leak ion channels

Answer 34

always open responsible for membrane permeabiity in resting states each channel is specific for a particular ion permeability is based upon the number of channels

Question 35

Gated ion channels

Answer 35

normally closed opened by specific signals

Question 36

Ligand-gated

Answer 36

opens (or closes) when ligand binds to the receptor portion of the extracellular component of the channel common in nerve and muscle and glands exist for Na+, K+, C++, Cl-

Question 37

Voltage-gated

Answer 37

open (and close) in response to small voltage changes across the membrane when a cell is stimulated, the permeability of the membrane is changed because gated ion channels open (or close) the movement of ions across the membrane changes the charg difference across the membrane. This causes the voltage-gated channels to open (or close) Those specific for Na+ and K+ are most numerous in electrically excited tissue C++ channels are important in smooth and cardiac muscle

Question 38

Establishing the resting membrane potential

Answer 38

All fluids are electrically neutral because the concentration of positively charged particles is equal to the concentration of negatively charged particles There is a difference in charge across the membrane because of the uneven distribution of ions on either side of the membrane Potential difference = the electrical charge difference across the membrane

Question 39

Resting membrane potential

Answer 39

the potential difference across the membrane in an unstimulated (resting) state

Question 40

the resting membrane potential is due to

Answer 40

permeability characteristics of the membrane differences in concentrations of various ions between the ECF and ICF

Question 41

Effect of K+

Answer 41

increasing [K+]ECF causes hyperpolarization decreasing [K+]ECF causes hypopolarization

Question 42

Effect of Na+

Answer 42

increasing [Na+]ECF causes hyperpolarization decreasing [Na+]ECF causes hypopolarization

Question 43

Effect of Ca++

Answer 43

increasing [Ca++]ECF closes voltage-gated Na+ channels decreasing [Ca++]ECF opens Na+ channels

Question 44

Effect of Cl-

Answer 44

increasing [Cl-]ECF causes hyperpolarization decreasing [Cl-]ECF causes hypopolarization

Question 45

Intercellular and Extracellular Potentials

Answer 45

Question 46

What are graded potentials?

Answer 46

these are local disturbances in the resting membrane potential they can result from: - chemical signals binding with receptors - changes in voltage across the membrane - mechanical stimulation - temperature changes - spontaneous opening of the ion channels they can be hypo- or hyperpolarizing events A hypopolarizing event can lead to a depolarizing event The magnitude of graded potentials is dependent upon the strength of the stimulus they can summate

Question 47

Describe an action potential. What are the roles of of Na+ and K+ on the action potential,?

Answer 47

Depolarizing events Reversal of polarity occurs Action potentials rapidly repolarizes The depolarizing phase of an action potential is caused by increasing permeability to Na+ The repolarizing phase of an action potential is caused by increasing permability to K+ An impulse is a wave of depolarization passing along a neuron followed by a wave of depolarization Continuous conduction occurs along a non-myelinated neuron Saltatory conduction occurs along a myelinated neuron Frequency of action potential is dependent upon the magnitude of the stimulus

Question 48

Relate the strength of a stimulus to the strength of an action potential.

Question 49

Describe a synapse. An essay question could be to describe synaptic transmission across a myoneural junction.

Answer 49

When an action potential reaches the synaptic knob of a presynaptic neuron, it triggers the opening of calcium voltage gated channels. The influx of calcium ions (Ca2+) leads to the release of neurotransmitter that are stored in the synaptic vesicles. The neurotransmitter crosses the synaptic cleft to bind to ligand gated channels on the postsynaptic cell. This creates an end plate potential which may or may not trigger an action potential in the postsynaptic cell.

Question 50

Synapse (image)

Answer 50

Question 51

Myoneural Junction, simple terms

Answer 51

The synaptic connection of the axon of a motor neuron with a muscle fiber.

Question 52

What are EPSP and IPSP?

Answer 52

EPSP = excitatory post-synaptic potential IPSP = inhibitory postsynaptic potential

Question 53

Relate a synaptic transmitter and a synaptic transmitter receptor to EPSP and IPSP.

Answer 53

An inhibitory postsynaptic potential (IPSP) is a kind of synaptic potential that makes a postsynaptic neuron less likely to generate an action potential. The opposite of an inhibitory postsynaptic potential is an excitatory postsynaptic potential (EPSP), which is a synaptic potential that makes a postsynaptic neuron more likely to generate an action potential.