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Neuromotor Function 1 > Lecture 2 - Communication within the Nervous System > Flashcards

Lecture 2 - Communication within the Nervous System Flashcards

1
Q

Does the human brain have more neurons or glial cells?

A

glial cells (10-50 x more than neurons)

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2
Q

T/F: It is always one-on-one communication between neurons.

A

False: 1 neuron can communicate with multiple neurons

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3
Q

List the 4 main functions of neurons.

A
  1. receive and integrate incoming information from sensory receptors or other neurons
  2. generate a nerve impulse (action potential)
  3. conduct the action potential
  4. transmit information to target cell (other neurons, muscles, glands)
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4
Q

How does information get passed along within the nervous system?

A

Action Potential

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5
Q

What is the basic functional unit of the nervous system?

A

Neuron cells

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6
Q

What are the 3 main features of a typical neuron?

A

cell body, dendrites, axons

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7
Q

Differentiate between dendrites and axons.

A

Dendrites carry signals towards the cell body, axons carry signals away from the cell body.

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8
Q

What are neurites?

A

axons and dendrites

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9
Q

What 2 ways are neurons classified?

A

structure and function

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10
Q

How are neurons structurally classified?

A

by number of a neuron’s processes extending from cell body

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11
Q

What are the 4 types of structural neuron classifications?

A

unipolar neurons
pseudo-unipolar neurons
bipolar neurons
multipolar neurons

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12
Q

Describe a unipolar neuron.

A

single process from cell body, characteristic of invertebrates

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13
Q

Describe a pseudo-unipolar neuron and list an example.

A

Short single process from cell body that splits into two processes (like a “T‟)
•Example: sensory neurons within dorsal root ganglion

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14
Q

Describe a bipolar neuron and list an example.

A

2 processes:one dendrite, one axon
•Examples: some sensory
neurons, including those of retina of eye and olfactory epithelium

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15
Q

Describe a mulitpolar neuron Where are they abundant? List an example of one.

A

a single axon and one or more dendritic branches emerge from all parts of the cell body
•characteristic of most neurons in brain and spinal cord
•Examples: motor neurons in spinal cord, Purkinje neurons of cerebellum, pyramidal neurons of motor cortex

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16
Q

Of the 4 structural classifications of neurons, which are the most abundant in the human nervous system?

A

multipolar

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17
Q

What are the 4 morphological characteristics of a multipolar neuron?

A

dendrites, cell body, axon, pre-synaptic terminal

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18
Q

Describe the nerve cell body.

A

Contains mitochondria, nucleus, neurofibrils and nissl substances; metabolic centre of the nerve.

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19
Q

Describe dendrites.

A

main apparatus for receiving information from other nerve cells; relatively short processes
often branch extensively (resemble branches of a tree)

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20
Q

What can you devise when you come across a neuron that has an extensive dendrite branching?

A

That the nerve is capable of receiving more information and is able to perform more complex tasks.

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21
Q

What is the main conducting unit of a neuron?

A

axons

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22
Q

Describe axons.

A

Can vary in length (1mm -> 1m), branch extensively before terminating, ends of the branches are enlarged and called the pre-synaptic terminals

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23
Q

Describe presynaptic axon terminals.

A

where axons make contact to transmit information, point of contact is the synpase.

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24
Q

What are the 3 components of a synpase?

A

presynaptic membrane + synaptic cleft + post synaptic membrane

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25
Q

How are neurons functionally classified?

A

based on connections to different tissue types

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26
Q

What are the 3 functional classifications of neurons?

A
  1. Primary sensory or afferent neurons
  2. Motor or efferent neurons
  3. Interneurons
27
Q

You just wrapped your hands around your mug of coffee and found it to be warmer than you expected. Trace the action potential through the 3 functional classification of neurons.

A
  1. Primary sensory/afferent neurons: registered the temperature stimulus and passed it onto the interneuron
  2. Interneuron: sorted through the incoming information and realized that the best course of action is to let go of the mug. The interneurons passed this message in to the motor/efferent neurons.
  3. Motor neuron/efferent neurons: received the message from the interneurons and activated the appropriate muscles in the hand let go of the mug.
28
Q

Differentiate between Golgi Type 1 neurons and Golgi Type 2 neurons. Where can each be found?

A 
Golgi Type 1:
• have long axons
• form the long fibre tracts of brain and
spinal tracts
• form the nerve fibres of peripheral
nerves
Golgi Type 2:
• have short axons that terminate
near cell body
• have short dendrites, with a starshaped
appearance
• found in large numbers in cerebral
and cerebellar cortex and in retina
29
Q

What is a synapse? What are the 2 most common areas for synapses?

A

A point of functional contact between two neurons or between a neuron and an effector cell;
axo-dendritic and axo-somatic

30
Q

What are the 2 types of synapses?

A

chemical and electrical

31
Q

Describe the synaptic transmission at a chemical synapse.

A
  • a chemical substance, the neurotransmitter, is released from presynaptic terminals of neuron
  • neurotransmitter binds to neurotransmitter receptors in postsynaptic membrane of another neuron
  • produces either excitation or inhibition of postsynaptic neuron
32
Q

The neurotransmitters at the axon terminal are housed in what structure?

A

vescicles

33
Q

What is the resting membrane potential?

A

potential difference across nerve fiber cell membrane is -70 to - 80 mV
• produced by diffusion of sodium and potassium ions through plasma membrane which is maintained by active sodium-potassium pump and passive leakage

34
Q

When are action potentials generated?

A

when excitatory synaptic inputs

excite a neuron

35
Q

Describe the different stages of an Action Potential.

A
  • nerve impulse (AP) is initiated at initial segment of axon
  • AP acts as a stimulus to adjacent point along cell membrane
  • this stimulus alters permeability of membrane to sodium ions (-55 mv)
  • sodium ions rapidly enter axon, producing depolarization of membrane potential
  • repolarization
  • refractory period
  • resting membrane potential
36
Q

What is the purpose of the refractory period?

A

Ensures that action potential propagation occurs unidirectionly & avoids a continuous excitatory state of the nerve and limits the frequency of the impulses

37
Q

Trace the movement of the neurotransmitters following the arrival of action potential at presynaptic axon terminal.

A

membrane of presynaptic terminal depolarizes, causing opening of voltage-gated Ca2+ channels, influx of Ca2+ causes synaptic vesicles to fuse with presynaptic membrane  triggers release of neurotransmitters into synaptic cleft

38
Q

T/F: Once the neurotransmitter binds to the receptor on the post-synaptic membrane the signal will always be excitatory.

A

False: depends on the type of neurotransmitter

39
Q

______ synaptic potentials tend to generate excitatory postsynaptic potentials (EPSP).

A

depolarizing

40
Q

______ synaptic potentials inhibit production of action potentials -> inhibitory postsynaptic potentials (IPSP)

A

hyperpolarizing

41
Q

______ is a neurotransmitter found at neuromuscular junction and parasympathetic nerve endings.

A

acetylecholine

42
Q

_____ is a neurotransmitter that acts on postsynaptic membrane in the sympathetic nervous system

A

norepinephrine

43
Q

How do neurotransmitters released into the synapse allow for communication between neurons?

A

By either producing EPSPs or IPSPs

44
Q

What are neuromodulators? Give an example of a neuromodulator.

A

modulate and modify activity of post-synaptic neurons, they’re not neurotransmitters. Neuromodulators released into synaptic cleft enhance, prolong, inhibit, or limit the effect of principal neurotransmitter on postsynaptic membrane.
Example: dopamine

45
Q

Describe how action potentials travel along unmyelinated neurons.

A

slow conduction rate and AP occurs on one direction; usually seen on small-diameter neurons.

46
Q

T/F: All myelin sheath is produced by Schwann cells.

A

F: Oligodendrocytes (CNS) Schwann cells (PNS).

47
Q

The small space of axon not covered by myelin sheath is called the ____ _ ____.

A

Node of Ranvier

48
Q

List the 4 functions of myelin sheath.

A
  1. insulates the axonal membrane
  2. reduces ability of current to leak out of the axon
  3. thus, myelin increases the distance that a current can flow passively
  4. greatly increases speed of AP conduction
49
Q

How are the Nodes of Ranvier able to depolarize the membrane?

A

b/c they have a high density of voltage-gated sodium channels

50
Q

How does AP propagation occur along myelinated neurons?

A

through saltatory conduction - jumping from one Node of Ranvier to the next

51
Q

Describe the etiology of Multiple Sclerosis.

A

plaques of demyelination are accompanied by inflammation of axons
 may lead to permanent axonal damage
 eventually blocked transmission of signals

52
Q

Electrical synapses use ___ ____ for communication.

A

gap junctions

53
Q

Describe how electrical synapses work.

A

mode of information transmission through ionic current
ion channels extend from cytoplasm of presynaptic neuron to cytoplasm of postsynaptic neuron
channels permit very rapid flow of ionic current from one cell to another e.g. defense reflexes

54
Q

T/F: Both chemical and electrical synpases allow only for unidirectional communication.

A

False.
Chemical: unidirectional.
Electrical: bidirectional

55
Q

List the 4 types of glial cells found in the CNS.

A
  1. Microglia
  2. Astrocytes
  3. Ependymal cells
  4. Oligodendrocytes
56
Q

What is the function of microglia?

A

smallest of glial cells

•function as phagocytes to remove cell debris, wastes and pathogens; protect brain against micro-organisms

57
Q

What are the 4 functions of astrocytes?

A

star-shaped glial cells; numerous in CNS

  1. maintain blood-brain barrier
  2. regulate the chemical environment of the extra-cellular space
  3. provide structural support to neurons
  4. absorb and recycle neurotransmitters
58
Q

What is the function of ependymal cells?

A

line ventricles of brain and central canal of spinal cord

•assist in production and circulation of Cerebrospinal Fluid (CSF)

59
Q

What is the function of oligodendrocytes?

A

form a myelin sheath around CNS axons
•one oligodendrocyte contributes myelin to several axons
•provide structural framework

60
Q

What are the 2 types of glial cells found in the PNS.

A

Schwann and Satellite cells

61
Q

What is the function of Schwann cells?

A

form myelin sheaths around axons in PNS
•each Schwann cell myelinates only a single axon
•participate in repair process after injury

62
Q

Compare and contract Oligodendrocytes and Schwann cells.

A 
Oligodendrocytes:
1. Produce myelin sheath
2. Found in the CNS
3. 1 oligodendrocyte cell can make myelin sheath on many axons
Schwann cells:
1. Produce myelin sheath
2. Found in the PNS
3. 1 Schwann cell per axon
63
Q

What is the function of satellite cells?

A

surround neuron cell bodies in PNS ganglia

•regulate O2, CO2, nutrient and neurotransmitter levels around ganglia

Neuromotor Function 1 (21 decks)

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