Unit 1_Neural Communication Part 1

Question 1

What do the following help us with?

Helps us to understand the flexibility/adaptability the CNS has for normal function.

Helps us understand what underlies normal learning processes across the life span.

Helps us understand processes in response to disease and trauma that are important to rehabilitation.

Helps us develop an understanding of how we as rehabilitation and other health professionals can treat without drugs or surgery.

Answer 1

Understanding Neural Communication

Question 2

What generate impulses and serve as the major means of communication within the nervous system and between the nervous system and the body parts?

Answer 2

Neurons

Question 3

What is the metabolic center of the cell and an important area to receive signals (postsynaptic) from other neurons?

Answer 3

Cell body

Question 4

What receive signals from other neurons (postsynaptic)?

Answer 4

Dendritic branches or dendrites

Question 5

What conducts signals away from the cell body to communicate with other neurons?

Answer 5

A single axon

Question 6

What release neurotransmitters at the end of axons?

Answer 6

Presynaptic terminals

Question 7

What are 3 primary classifications of neurons?

Answer 7

Pseudounipolar
Bipolar
Multipolar

Question 8

What cell bodies do we see most in our nervous system?

Answer 8

Bipolar cell

Question 9

In addition to electrical signals, what do the axons transport from the cell body to the synaptic terminals (anterograde transport) and back from the synaptic terminal to the cell body (retrograde transport) to provide nourishment, structural changes, and materials needed at synapses?

Answer 9

Materials

Question 10

The axon arises from a specialized region of the cell body referred to as what?

Answer 10

axon hillock

Question 11

It is the axon that will convey information within the nervous system from one cell to another by transmitting an electrical signal that is called what?

Answer 11

Action potential

Question 12

What is started at the initial segment or trigger zone which is distal to the axon hillock?

Answer 12

Action potential

Question 13

What is just distal to the axon hillock where action potentials are generated?

Answer 13

The “trigger zone” or “initial segment”

Question 14

Near its end, an axon will divide into fine branches that have specialized swellings called what? By means of these terminals, one neuron will transmit information that it is carrying to the receptive post-synaptic surface of other neurons (usually dendrites but also on cell bodies or axons).

Answer 14

pre-synaptic terminals

Question 15

What is the site of communication between excitable cells (neuron to neuron or neuron to effector cell (muscle, gland, etc.))? This cell is one that can undergo changes in its electrical charge in response to stimulation.

Answer 15

Synapse

Question 16

What are two types of synapses?

Answer 16

Electrical and chemical

Question 17

What type of synapse is most common in the CNS and specialized neurotransmitters convey information from one cell to the other?

Answer 17

Chemical synapse

Question 18

What typically occur between the axon terminal of one neuron and the cell body or dendrite of a second neuron?

Answer 18

Neuronal synapses

Question 19

What is the neuron conducting impulses towards the synapse referred to as?

Answer 19

Pre-synaptic neuron

Question 20

What is the neuron conducting impulses away from the synapse referred to as?

Answer 20

Post-synaptic neuron

Question 21

What is a narrow gap that separates the pre-synaptic and post-synaptic cells?

Answer 21

Synaptic cleft

Question 22

How are signals transmitted across the synaptic cleft that is released from the presynaptic terminal?

Answer 22

Neurotransmitter

Question 23

Neurotransmitters can have either an excitatory effect or an inhibitory effect on the post-synaptic cell based on what?

Answer 23

Post synaptic receptor

(ex. Dopamine, which can be either excitatory or inhibitory depending on the post-synaptic receptor it binds with)

Question 24

If a threshold level of stimulation is reached, what will carry the signal from the post-synaptic cell to the next cell?

Answer 24

An action potential

Question 25

Synapses occur on all parts of neuron, but most are on what followed by cell body (soma)?

Answer 25

Dendrites

Question 26

What allows information to be widely spread to other neurons and other parts of the nervous system?

Answer 26

Divergence

Question 27

What allows information from various parts of the nervous system to be integrated at single or groups of neurons?

Answer 27

Convergence

Question 28

What signal is pre-synaptic?

Answer 28

Sensory signals

Question 29

What signal is pre and post-synaptic?

Answer 29

Motor signals

Question 30

What signal is post-synaptic?

Answer 30

Muscle signals

Question 31

What allows the nervous system to carry out its functions including the action potential for communication?

Answer 31

Special membrane properties

Question 32

What are the following properties of? Has passive properties based on basic physics Responds to voltage changes Responds to various chemicals (neurotransmtters)

Answer 32

Special membrane properties that allow the nervous system to carry out its functions

Question 33

What is the difference in electric potential (Voltage) between the interior and the exterior of a cell (neuron)?

Answer 33

Membrane Potential (Vm)

Question 34

What refers to how hard it is for ions to flow through membrane?

Answer 34

Membrane resistance (Rm)

Question 35

What refers to how easy it is for ions to flow through membrane?

Answer 35

Membrane conductance (g)

Question 36

What refers to the ability for membrane to store charge (think of a ditch or water tank)? Myelin decreases membrane capacitance.

Answer 36

Membrane capacitance (Cm)

Question 37

What refers to resistance to flow of ions within the cell, particularly the axon? Dependent on diameter of axon.

Answer 37

Axoplasmic (cytoplasmic) resistance (Ra)

Question 38

What is dependent on Membrane capacitance and membrane resistance, but more on membrane capacitance? Important for temporal summation.

Answer 38

Membrane time constant

Question 39

What refers to how far a membrane potential can maintain its height? Dependent on membrane resistance and axoplasmic resistance. Important for spatial summation.

Answer 39

Length (space) constant

Question 40

What is dependent on axoplasmic resistance and membrane resistance?

Answer 40

Conduction Velocity

Question 41

What decreases membrane capacitance reducing the time constant and increasing the conduction velocity?

Answer 41

Myelin

Question 42

What do neurons have that makes up a cell membrane and is made of fat?

Answer 42

Lipid bilayer

Question 43

What is the area outside of the neuron known as?

Answer 43

Extracellular space

Question 44

What does resting membrane potential of a neuron refer to?

Answer 44

Negative

Question 45

When we mention values of membrane potential, what are we reporting?

Answer 45

What is the inside of the cell relative to the outside of the cell

Question 46

What move ions across the neuron’s membrane?

Answer 46

electrical and chemical gradients

Question 47

What is a mosaic of membrane channels (windows) with transmembrane channels of various types that live right next to each other?

Answer 47

A neuron

Question 48

Some synapses involve depolarization (or less negative/positive charge, more sodium) which we call what?

Answer 48

Excitation

Question 49

Some synapses involve hyperpolarization (or negative charge, more potassium) which we call what?

Answer 49

Inhibition

Question 50

What requires adenosine triphosphate (ATP) that is responsible for maintaining the concentration gradients for continuous diffusion of ions and, therefore, a continual charge separation or membrane potential?

Answer 50

Sodium-Potassium Pump

Question 51

The local graded alterations in the resting membrane potential of the post-synaptic cell are referred to as what? These result from changes in ion permeability due to the effect of the neurotransmitter.

Answer 51

post-synaptic potentials

Question 52

What determine whether a synapse is excitatory or inhibitory?

Answer 52

The receptors

Question 53

If the neurotransmitter causes excitation, what will the result be, which will depolarize the post-synaptic cell membrane and bring it closer to threshold?

Answer 53

Excitatory post-synaptic potential or EPSP

Question 54

If the neurotransmitter causes inhibition, what will the result be, which will hyperpolarize the post-synaptic cell membrane and move it further from threshold?

Answer 54

inhibitory post-synaptic potential or IPSP

Question 55

What will determine whether or not a given post-synaptic cell reaches a threshold of stimulation that will result in an action potential?

Answer 55

The summation of EPSP’s and IPSP’s

Question 56

What is an autoimmune disease that destroys receptor sites (junctional folds) for acetylcholine at Neuromuscular junction (NMJ) on muscle cells which are post-synaptic cells? Patients have signs and symptoms related to cortical bulbar pathways, cranial nerve pathways so weakness in the face and can sometimes have difficulty swallowing.

Answer 56

Myasthenia Gravis

Question 57

What is is the initial segment or trigger zone of axon where SUMMATION occurs? Activity of all EPSPs/IPSPs are summed and decision of cell to generate action potential or not is reached. All EPSPs and all IPSPs passively move around the cell and via the axon hillock to initial segment/trigger zone. All are summated. If there is sufficient depolarization to reach threshold an action potential will be generated.

Answer 57

Integrative Component

Question 58

What occurs when a single neuron has many excitatory and inhibitory synapses on it with some out on dendrites and cell body with a few near the axon terminals? For example, a single motor neuron in the ventral horn of the spinal cord may have 10,000 synapses with other neurons.

Answer 58

Convergence

Question 59

What is a summation of post-synaptic potentials from a single stimulus location occurring at high frequencies? At high frequencies a new EPSP occurs before membrane potential can return to baseline. Therefore, a single sub-threshold synapse may drive neuron to threshold when it fires at high frequency.

Answer 59

Temporal summation

Question 60

What is combined action of 2 of more post-synaptic potentials from different points on the neuron (dendrite, cell body and sometimes axon terminal)? Synapses need to be close enough for summation to occur.

Answer 60

Spatial summation

Question 61

What ultimately affect initial segment/trigger zone?

Answer 61

Temporal and spatial summation

Question 62

Capacitance adds a time element to passive properties during what type of summation?

Answer 62

Temporal summation

Question 63

What determines amount of capacitance?

Answer 63

Separation of charges Less separation = more capacitance More separation = less capacitance (myelin separates charges)

Question 64

What affect how far a potential can move without disappearing and are the basis of the length (space) constant which is important for Spatial Summation?

Answer 64

Axonal (within cell) and Membrane (through membrane) resistances

Question 65

Larger diameter axons have what?

Answer 65

Less resistance

Question 66

What degrades signal?

Answer 66

Length

Question 67

What have greater impact than those out on tips of dendrites all else being equal?

Answer 67

Synapses closer to trigger zone

Question 68

When is there greater chance for spatial summation?

Answer 68

If the length constant is longer

Question 69

What is dependent on passive properties, but active properties underlay spiking an action potential?

Answer 69

Summation

Question 70

How do neurons communicate with each other?

Answer 70

Via action potentials

Question 71

What is a rapid change in membrane polarity observed in excitable cells that allows for the transmission of electrical information from one cell to another?

Answer 71

Action potential

Question 72

What involves a positive feedback cycle and is time-limited?

Answer 72

Spiking an action potential

Question 73

As soon as the critical threshold of depolarization caused by the summation of post- synaptic potentials is reached, what channels open allowing Na+ to rush into the cell along both its concentration and electrical gradient? These channels also open but more slowly and take longer to close. During this time more positive charges (Na+) enter the cell than leave (K+). The membrane potential thus decreases (becomes more positive) and eventually reverses as the inside becomes more positive than the outside. This constitutes the depolarization phase of the action potential which is short lived (<1 millisecond).

Answer 73

voltage gated sodium channels

Question 74

What channels close rapidly as the membrane becomes more positive and voltage gated potassium channels remain open long to allow K+ to diffuse quickly out of the cell? This K+ efflux brings the membrane potential back to its resting level and is called the repolarization phase. The K+ channels remain open long enough to cause a brief period of hyperpolarization.

Answer 74

Sodium channels

Question 75

What underlies generation of an action potential?

Answer 75

Positive feedback

Question 76

What channels do the following: Open quickly Close quickly Are refractory

Answer 76

Voltage gated Na+ channels

Question 77

What is responsible for refractory period?

Answer 77

Inactivation of voltage gated Na channels

Question 78

What is the axon itself?

Answer 78

The conductive component

Question 79

In regards to an atom, what do the following relate to: 1. diameter (Axoplasmic resistance) 2. if it is myelinated or not (Membrane 3. capacitance and resistance) 3. If myelinated, how much myelin.

Answer 79

How fast an axon conducts

Question 80

What is inversely related to Axonal resistance (Ra) and Axonal Capacitance (Cm)?

Answer 80

Axonal conduction velocity

Question 81

If axons have the following, what speed is their conduction velocity? 1. Small diameter axons have high resistance 2. Unmyelinated axons have high capacitance

Answer 81

Slower

Question 82

If axons have the following, what speed is their conduction velocity? 1. Large diameter axons have low resistance 2. Myelinated axons have low capacitance

Answer 82

Faster

Question 83

Not all axons are myelinated, but those that are myelinated conduct action potentials how?

Answer 83

Faster

Question 84

What process reduces the ability of passive current to leak out of the axon, increases the distance along the axon that a given local current can flow passively and decreases the capacitance of the axon reducing time to charge membrane allowing action potentials to conduct faster?

Answer 84

Myelinated axons at the Nodes of Ranvier

Question 85

What appear to occur only at the “nodes of Ranvier” where there are gaps in myelin, but they are traveling whole axon?

Answer 85

Action potentials

Question 86

What separate charges so they are less attracted to each other?

Answer 86

Myelin

Question 87

What varies with diameter of axon, and presence and thickness of myelin?

Answer 87

Velocity

Question 88

What are faster than smaller diameter because less axoplasmic resistance?

Answer 88

Large diameter myelin

Question 89

What are faster than unmyelinated because myelin reduces membrane capacitance?

Answer 89

Myelinated

Question 90

What disease affects the conductive component and is autoimmune? It destroys myelin in PNS-affects motor, sensory and autonomic functions of peripheral nerves-subsequent to infection-rapid progression. Initial symptoms are often tingling/numbness and weakness. Progressive muscle weakness that may result in full paralysis within days or weeks.

Answer 90

Guillain Barre

Question 91

What disease affects the conductive component and is autoimmune? It destroys myelin in CNS-cerebrum, brainstem and spinal cord. Visual, motor, sensory, bowel and bladder, cognition, emotions, speech, swallowing, autonomic, etc. Progressive – speed/severity may vary

Answer 91

Multiple Sclerosis