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BMPH 1 > Nervous System > Flashcards

Nervous System Flashcards

1
Q

A feature of generator potentials that distinguished them from action potentials

A

Graded in amplitude

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2
Q

Region of most central neurons that has the lowest threshold for initiation of Na+-dependent action potentials

A

Proximal segment of the axon

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3
Q

When is axonal transport considered orthograde?

A

When the direction of transport is from the soma to the axon terminal.

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4
Q

Access from the blood to CSF is limited by tight junctions between:

A

Endothelial cells and choroid epithelial cells

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5
Q

Cerebrospinal Fluid (CSF)

A
  • Flows from ventricles out into the sub arachnoid space
  • Flows into the blood through the arachnoid villi
  • Mechanically and chemically buffers the brain
  • Originates in the choroid plexus
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6
Q

Reflex

A

Subconscious, predictable responses to specific sensory stimuli

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7
Q

Reflex arc

A

Neural pathway or “wiring” of the reflexes

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8
Q

Main components of the reflex arc (monosynaptic)

A

1) receptors (pressure, pain, chemical)
2) Afferent (sensory) neurons
3) Efferent (motor) neurons
4) Effectors (muscles, organs or glands)
5) Synapses

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9
Q

Purpose of receptors in reflex arc

A

To receive stimuli

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10
Q

Purpose of afferent/sensory neurons in reflex arc

A

carry the stimulus information into the integration center (CNS)

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11
Q

Purpose of efferent/motor neurons in reflex arc

A

Carry information out of the target muscle, organ, or gland

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12
Q

Purpose of effectors in reflex arc

A

Execute actions

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13
Q

Purpose of synapses in reflex arc

A

one synapse with the motor (efferent) neuron or multiple with interneurons

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14
Q

Main components of polysynaptic reflex arc

A

1) receptors (pressure, pain, chemical)
2) Afferent (sensory) neurons
3) Interneurons (CNS)
4) Efferent (motor) neurons
5) Effectors (muscles, organs or glands)
6) Synapses

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15
Q

Purpose of interneurons polysynaptic reflex arc

A

Process information, directs motor output

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16
Q

Are interneurons needed in a reflex arc?

A

No. Monosynaptic arcs don’t have any.

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17
Q

Explain the patellar reflex.

A

1) Hammer hits patellar tendon (right below kneecap).
2) Stretch receptor on afferent/sensory neuron activated
3) Signal transmitted down axon to cell body and then dorsal root ganglion through spinal cord
4) Sensory neuron activates efferent (motor) neuron on extensor muscle. Also activated interneuron in spinal cord, which then activates motor neuron on flexor muscle.
5) Motor neurons signal transmits out of spinal cord and back to flexor and extensor muscles.
6) Flexor muscle contracts white extensor extends, causing reflex reaction.

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18
Q

Example of a monosynaptic reflex

A

Muscle stretch/patellar reflex

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19
Q

Example of a polysynaptic reflex

A

Withdrawal reflex

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20
Q

Somatic reflexes

A

Stimulate skeletal muscles

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21
Q

Autonomic reflexes

A

Regulate smooth muscle, glands

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22
Q

Structure of a neuron

A

1) Dendritic branches
2) Dendrites
3) Cell body: Mitochondria, ER, Golgi, Nucleus
4) Axon Hillock
5) Axon
6) Telodendria
7) Synaptic terminals

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23
Q

5 Classifications of Neurons

A

1) Anaxonic: no axon
2) Unipolar: one structure extend from soma (cell body)
3) Bipolar: one axon + one dendrite
4) Multipolar: One axon + multiple dendrites (CNS)
5) Pseudounipolar: One extension that divides into two (PNS)

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24
Q

Structure of a synapse

A

1) Presynaptic: neurotransmitter vesicles
2) Synaptic cleft: space between neuron and receiving structure
3) Postsynaptic: ligand-gated receptors for NT, ion channels for depolarization

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25
Q

Types of Neuroglia

A

1) Ependymal cells
2) Oligodendrocytes
3) Astrocytes
4) Microglia
5) Satellite cells
6) Schwann cells

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26
Q

Neuroglia in central nervous system

A

1) Ependymal cells
2) Oligodendrocytes
3) Astrocytes
4) Microglia

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27
Q

Neuroglia in peripheral nervous system

A

1) Satellite cells

2) Schwann cells

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28
Q

Ependymal cells

A
  • CNS
  • Assist in producing, circulating, and monitoring of CSF
  • Columnar, ciliated cells lining the ventricles (brain) and central canal (spinal cord)
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29
Q

Oligodendrocytes

A
  • CNS
  • Myelination: faster APs and better conductance
  • Degradation, immune surveillance, and antigen transfer to microglia
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30
Q

Astrocytes

A
  • CNS
  • Structure/Scaffold
  • Regulate ion, nutrient, and dissolved gas concentrations
  • Neuroprotection to neuron
  • Clear the synapsis: absorb and recycle
  • Homeostasis
  • Glial fibrillary acid protein (GFAP)
  • End feet (cover blood vessels, BBB)
  • Maintain BBB
  • Form scar tissue after injury
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31
Q

Microglia

A
  • CNS
  • Immune response: protection from pathogens
  • Neurotransmission to neuron
  • Macrophage-like
  • Scavenging cells
  • Remove cell debris, wastes, and pathogens by phagocytosis
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32
Q

Satellite Cells

A
  • PNS
  • Surround neuron cell bodies in ganglia
  • Regulate O2, CO2, nutrient, and NT levels around neurons in ganglia
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33
Q

Schwann cells

A
  • PNS
  • Myelination of peripheral axons
    - single wrap = unmyelinated
    - multiple-wrap = myelinated
  • Participate in repair process after injury
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34
Q

How is the nervous system organized?

A

Central Nervous System: Brain & spinal cord

  • input from afferent division of PNS
  • output to efferent division of PNS

Peripheral nervous system: afferent/efferent

  • afferent: sensory & visceral stimuli
  • efferent: somatic & autonomic NS
    • Somatic: motor neurons –> skeletal
    • Autonomic: Sym, para, & enteric
      • Sympathetic & parasympathetic
        • Smooth muscle
        • Cardiac muscle
        • Exocrine glands
        • Some endocrine glands
      • Enteric: stimuli in digestive tract
        • Affects digestive organs only
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35
Q

Bundles of neurons

A

CNS: nuclei
PNS: ganglia

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36
Q

Describe the withdrawal reflex (polysynaptic reflex)

A

PNS:

1) Painful stimulus at receptor
2) Signal travels down sensory neuron axon

CNS:

3) synapse with interneurons 1 and 2 (excitatory)
4) Interneuron 1 excites motor neuron 1 while 2 inhibits motor neuron 2
5) Interneurons synapse with motor neurons 1 (excitatory) & 2 (inhibitory) respectively

PNS:

6) Signals travel down motor neuron 1 & 2’s axons
7) Motor neuron 1 connects to flexor muscle (contract) while motor neuron 2 connects to extensor muscle (no contraction)

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37
Q

Why are interneurons needed?

A

They are mostly inhibitory neurons connecting different brain regions, including sensory and motor neurons. Forms circuits with nearby neurons to analyze small pieces of info and connect circuits of neurons in different (or distant) regions.

In reflex, inhibits opposite muscle group to facilitate action of activate group. Without this, actual response would be diminished, jerk would be less vigorous, withdrawal slow and milder.

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38
Q

How does neuron morphology relate to its function?

A

Provide evidence of the role of that particular type of neuron.

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39
Q

How does unipolar neuronal structure relate to function?

A

Structure: Only one process extends from the cell body.

Function: Less common in vertebrates. One example is dorsal cochlear nucleus.

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40
Q

How does pseudo-unipolar neuronal structure relate to function?

A

Structure: one extension from cell body, and axon split into two branches

Function: signal can bypass cell body and propagate rapidly. One example is sensory neurons, with one branch to PNS and the other to CNS.

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41
Q

How does multipolar neuronal structure relate to function?

A

Structure: Single axon, many dendrites

Function: the higher the need for processing higher information inputs, the higher the number of dendrites. Examples include motor neurons, cone cells, and Purkinje cells.

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42
Q

How does the high specialization of neurons affect their functioning?

A

Require high metabolic resources, virtually all from aerobic glucose metabolism, therefore requiring large amounts of oxygen and thus blood flow. Any alteration in blood flow can lead to neuronal cell death.

Postmitotic terminally differentiated so neurogenesis ends during adulthood.

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43
Q

White matter

A

highly myelinated - axons

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44
Q

Gray matter

A

Myelin + cell bodies

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45
Q

Two major methods to send electrical information

A

Active & passive

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46
Q

Use of action potentials

A

For active transfer of information

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47
Q

Use of local graded potentials

A

For passive transfer of information

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48
Q

Active spread of information

A

An AP propagates to a synapse on the dendrite of a neuron where a local synaptic potential is generated in the dendrite.

AP later generated at axon hillock travels in the axon from the motor neuron to the neuromuscular synapse with a muscle fiber.

AP generated at muscle fiber propagates to the ends of the muscle fiber initiating contraction.

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49
Q

Passive spread of information

A

Local potentials generated by AP passively flows to the cell body and axon hillock.

Local EPP (end plate potential) generated by neuromuscular synapse in the muscle fiber flows across synapse.

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50
Q

Action potentials ____ propagate along nerve and muscle membrane

A

Actively

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51
Q

APs send ___ information

A

electrical

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52
Q

Information is coded in the ___ and ___ of the action potentials

A

frequency; spacing

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53
Q

APs typically propagate ____ change in size or shape as a pulse of voltage changes

A

Without

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54
Q

The distance an AP can travel is only limited by the ___

A

Length of the axon or muscle fiber

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55
Q

APs require ___ to propagate

A

voltage dependent Na+ and K+ channels

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56
Q

The amplitude of graded potentials ___ with increasing distance from the site of current injection

A

Decreases

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57
Q

What are the conductors in living organisms?

A

The intracellular and extracellular electrolyte solutions

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58
Q

How is current carried in living organisms?

A

By the movement of 150 mM of positive ion and 150 mM of negative ions

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59
Q

Does a cell membrane have low or high resistance?

A

High resistance

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60
Q

Why do cell membranes have the level of resistance that they do?

A

Have high resistance because it greatly impedes the movement of ions across it

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61
Q

What changes the resistance of cell membrane?

A

Ion channel proteins

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62
Q

How do ion channels affect resistance of cell membranes?

A

Decrease resistance by opening their pores

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63
Q

Time constant

A

Tau (c)

The time for current to inc to 63% of steady state level or to decay to 37% of steady state level

Typical range: 1-20 ms

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64
Q

Length constant

A

lambda (c)

The distance at which the voltage falls to 37% of its highest value

Typical range: 0.1-5 mm

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65
Q

When is lambda (length constant) smallest?

A

Small diameter axons and muscle fibers

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66
Q

What two factors can increase lambda?

A

Increasing diameter and myelination

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67
Q

How does myelination increase lambda?

A

By decreasing membrane capacitance and increasing membrane resistance

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68
Q

Cable properties

A

The passive properties of axons and muscle fibers

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69
Q

When is repetitive discharge of excitable cells important?

A

1) Neurons that integrate local potentials and translate them into frequency of AP discharge
2) Some cells are driven to threshold by inputs from other cells
3) some cells have intrinsic pacemaker activity, including many neurons and the heart

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70
Q

What determines AP firing properties?

A

Ion channels!

Also: cell geometry and pattern of ion channel disrtibution

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71
Q

How is the membrane depolarized?

A

Influx of Na+ and Ca2+ –> more positive

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72
Q

How is the membrane hyper polarized?

A

Efflux of K+ –> more negative

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73
Q

How is depolarization achieved?

A

1) Activating depolarizing channels (Na, low voltage activate Ca, nonselective cation)
2) Turning off some of the depolarizing K+ channels (some turn off with time, others with depolarization)

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74
Q

Does repetitive AP activity require both hyper polarizing and depolarizing currents?

A

Yes

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75
Q

Compound AP

A

Extracellular AP produced by stimulating and recording from whole nerve. Grows as stimulation voltage is increase and more nerve fibers are recruited. Graded in size and at most a few mV.

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76
Q

Synapse

A

Junction between:

  • neuron-neuron
  • neuron-muscle

Where the axon of one neuron (presynaptic) terminates on the (postsynaptic):

  • dendrite
  • axon
  • cell body of another neuron
  • cell body of a muscle cell
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77
Q

Classification of synapses

A
  • Chemical
  • Electrical
  • Conjoint (chemical + electrical)
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78
Q

Differences between chemical and electrical synapses

A

Use NTs | Gap junctions
1-way transmission | transmission both ways
More common | More rare
Synaptic cleft | Gap junction
0.5 ms delay | 0.2 ms delay
Signal amplification | Same signal
Signal inversion. | Same signal

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79
Q

What is a neurotransmitter?

A

1) chemical must be found within presynaptic neuron
2) When presynaptic neuron is stimulated, it must release the chemical
3) when the chemical is applied exogenously, it must act on a post-synaptic neuron and case a biological effect
4) after a chemical is released, it must be inactivated

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80
Q

Synaptic transmission process

A

1) . AP arrives at axon terminal
2) Voltage-gated Ca2+ channels open and Ca2+ enters the axon terminal
3) Ca2+ entry causes NT-containing synaptic vesicles to release their contents by exocytosis
4) NT diffuses across the synaptic cleft and binds to ligand-gated ion channels on the postsynaptic membrane
5) Binding of NT opens ligand-gated ion channels, resulting in graded potentials
6) Reuptake by presynaptic neuron, enzymatic degradation, and diffusion reduce NT levels, terminating the signal.

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81
Q

Acetylcholine

A

Derived from: Choline

Synthesized in: presynaptic cytosol

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82
Q

Dopamine

A

Derived from: Tyrosine

Synthesized in: Presynaptic cytosol

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83
Q

Norepinephrine (noradrenaline) and Epinephrine (adrenaline)

A

Derived from: Tyrosine
Synthesized in:
- NE: dopamine containing vesicles
- epi: NE containined vesicles

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84
Q

Serotonin

A

Derived from: Tryptophane

Synthesized in: presynaptic cytosol & cells in GI

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85
Q

Histamine

A

Derived from: histidine

Synthesized in: presynaptic cytosol, mast cells, basophils/eosinophils

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86
Q

Glutamate-Glutamine Cycle

A

1) Glutamate release in synaptic cleft
2) Uptake into glia cell
3) Conversion of glutamate to glutamine via glutamine synthetase
4) Transfer glutamine to presynaptic terminal
5) Glutamine to glutamate via glutaminase
6) Package glutamate into vesicles

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87
Q

GABA

A

Derived from: Glutamate

Synthesized in: Presynaptic cytosol

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88
Q

Synaptic vesicle types

A

Small clear core and large dense core

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89
Q

Small clear core

A

Contain small molecule NTs like ACh, Glue, GABA, and biogenic amines

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90
Q

Large dense core

A

Contain serotonin, peptides, and biogenic amines

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91
Q

Fusion of vesicles to presynaptic membrane

A

1) Dimer on presynaptic membrane binds with VAMP on vesicle membrane result in SNARE complex
2) Binding brings presynaptic membrane closer to vesicle membrane
3) Ca2+ facilitates binding of SNARE complex to synaptotagmin on vesicle membrane
4) Bindings fuses vesicle membrane with presynaptic membrane, allow exocytosis of NT in vesicle

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92
Q

Types of postsynaptic receptors

A

Inotropic and metabotropic

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93
Q

Ionotropic receptors

A

1) primary transmitter attached to receptor

2) Gate is opened, allowing influx of ions

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94
Q

Metabotropic receptors

A

1) primary transmitter attached to primary receptor
2) Release of internal second messenger
3) second messenger binds to secondary receptor
4) Gate is opened, allowing influx of ions

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95
Q

How do receptor types differ in terms of response times?

A

Inotropic are rapid (5-10 ms) while metabotropic are slower (20-50 ms)

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96
Q

Where can each receptor type be found?

A

Ionotropic on postsynaptic only. Metabotropic can be both pre and post synaptic (pre regulates NT transmission)

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97
Q

Which NT is degraded in cleft??

A

Acetylcholine only by acetylcholinesterase

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98
Q

How are all NTs (except ACh) removed from cleft?

A

By transporters

GABA - GAT
Glutamate - GluT
Serotonin - SerT
Dopamine - DAT
Norepinephrine - NET
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99
Q

How does each structure on a neuron relate to function?

A

1) Dendrites, soma, and axon hillock: get input from many presynaptic endings
2) Soma and axon hillock: integrate input and “decide” to fire APs
3) Axon: Conducts APs to the synaptic ending
4) Synaptic ending: contacts other neurons and excites/inhibits

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100
Q

What is the importance of convergence?

A

Allows summation and integration of information from multiple sources

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101
Q

What is the importance of divergence?

A

Provides amplification: one input signal can reach a large number of targets

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102
Q

Excitatory chemical synapses

A

The NT depolarizes the posynaptic cell, inc the probability for an AP.

If reversal potential for the channel is more positive than the threshold, the synapse is excitatory.

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103
Q

Inhibitory chemical synapses

A

If reversal potential for channel is more negative than the threshold –> synapse is inhibitory

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104
Q

What determines if a chemical synapse is excitatory or inhibitory?

A

Postsynaptic neuron firing AP is:

Easier –> excitatory
Harder –> inhibitory

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105
Q

Trigger zone

A

Location where APs are initiated.

Highest density of Na channels –> lowest threshold –> AP will initiate here

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106
Q

What is the impact of synapse location?

A

Synapses closer to the trigger zone have a large impact on probability of the neuron to fire an AP

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107
Q

Spatial summation

A

Occurs when multiple terminals at diff location on one neuron are activated simultaneously –> postsynaptic potentials spread passively (cable properties) and “add up”

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108
Q

Temporal summation

A

Occurs when one terminal is activated at rapid succession

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109
Q

Why is axonal transport necessary?

A

1) Proteins synthesized in cell body but axons and nerve endings need continuous supply
2) Neuropeptides processed during transport
3) Signal molecules and growth factors travel to targets across neuron
4) Needed for repair after injury

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110
Q

Types of transport

A

1) Orthograde: away from cell body; fast and slow
2) Fast: carries vesicles and organelles
3) slow: carries enzymes and cytoskeleton components
4) Retrograde: toward cell body; fast

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111
Q

Fast orthograde transport mechanism

A

Vesicles and organelles move along microtubules powered by Kinesin using ATP

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112
Q

Retrograde transport mechanism

A

Organelles and vesicles separately move along microtubules powered by Dynein using ATP

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113
Q

Retrograde transport - general

A
  • Carries growth factors from terminals to cell body
  • May carry info about state of terminals
  • Transports viruses such as herpes, polio, chickenpox, and rabies
  • Transports toxins like tetanus
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114
Q

Blood brain barrier

A

Limits passage of molecules into the brain. Can override by injecting straight into CSF or increasing oil/water partition coefficient (hydrophobic is better).

Endothelial cells of BBB are fused tightly together to form tight junctions to nothing can get through. Surrounded by astrocytic end feet.

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115
Q

Generator potential

A
  • Depends on stimulation
  • Changes in sensory cell’s resting potentials
  • Graded in amplitude
  • Produced by ion channels or GPCR
  • Adapt with varying speed (Fast vs slow)
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116
Q

Why is the generator potential graded?

A

So the response to a stronger second stimulus is larger

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117
Q

What does a generator potential generate?

A

A sufficient depolarization in excitable cells can reach threshold and GENERATE APs (even a little after the stimulus once firing begins)

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118
Q

Why do generator potentials adapt?

A

Stronger stimulus produce larger responses (graded), but as a strong stimulus persists, the response diminished in time.

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119
Q

What is the mechanism of the generator potential?

A

1) A change in ion channel conductance, often by opening channels that allow entry of Na or Ca
2) Channels may be directly activated by mechanical force, temp change, or another stimulus
3) In other cases, the stimulus is sensed by a GPCR and a cascade of second messengers changes channel conductance
4) A stronger stimulus opens more channels, so the response is larger.

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120
Q

Generator potentials at synapses

A

Cause more NT to be released a more positive voltages and less a more negative voltages

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121
Q

Neurons

A
  • Highly specialized, excitable cells

- Morphologic diversity

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122
Q

Glia

A

Supporting cells

1) Schwann (neurolemmacytes): myelin producing - PNS
2) Oligodendrocytes: myelin producing - CNS
3) Astrocytes: nutritional support
4) Microglia: macrophages (immune support)

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123
Q

Central Nervous system (CNS)

A
  • Brain and spinal cord

- Collection of nerve cell bodies = nucleus

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124
Q

Peripheral Nervous System (PNS)

A
  • Peripheral nerves

- Collection of nerve cell bodies = ganglia

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125
Q

Sensory (afferent) function of NS

A
  • General - Touch

- Special sense - sight, sound, taste, smell

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126
Q

Motor (efferent) function of NS

A
  • Voluntary (somatic): skeletal muscle

- Involuntary (autonomic): smooth & cardiac

127
Q

Involuntary (autonomic) NS

A
  • Parasympathetic: craniosacral - fight or flight

- sympathetic: thoracolumbar - feed or fornicate

128
Q

Integrative function of NS

A

Interneurons within the CNS

129
Q

Types of Synapses

A

1) Axosomatic or axodendritic: terminal to dendrite, no invagination of dendrite
2) Axodendritic: terminal to dendrite, invagination of dendrite to terminal
3) Axoaxonic: terminal to terminal

130
Q

Presynaptic inhibition

A

Inhibit excitatory neuron directly (on terminal)

131
Q

Postsynaptic inhibition

A

Inhibit excitatory neuron indirection (not on terminal, elsewhere on postsynaptic)

132
Q

Most common communication method with neurons?

A

Chemical synapse

133
Q

Saltatory conduction

A

Signal jumps along axon between nodes, increasing speed and better signal recognition/strength (bc it doesn’t degrade)

134
Q

The role of myelin

A
  • Increase neural transmission along axon via saltatory conduction
  • Provides some limited protect but other methods provide more
  • No nutrition
135
Q

Organization of nerves

A

Smallest –> largest

Endo –> Peri –> Epi

136
Q

Endoneurium

A

Smallest; surrounds individual nerves/schwann cells

137
Q

Perineurium

A

Middle; surrounds fascicles, holds fibers together

138
Q

Epineurium

A

Largest; surrounds peripheral nerves, holds fascicles together

139
Q

Meninges

A

CNS

Dura, arachnoid, and pia mater

140
Q

Dura mater

A

CNS

Dense, fibre-elastic connective tissue

141
Q

Arachnoid mater

A

CNS

Fibrous connective tissue, subarachnoid space

142
Q

Pia mater

A

CNS

Collagen, elastin, and few fibroblasts

143
Q

Order of meninges

A

Dura (outer) –> arachnoid –> pia (inner)

144
Q

Choroid plexus

A
  • Modified ependymal cells

- Highly vascular: produces CSF

145
Q

Autonomic Sympathetic mechanism

A
  1. preganglionic cell bodies: thoracolumbar (T1-L2/L3)
  2. Preganglionic fibers: shorts, ACh release
  3. Postganglionic cell bodies: sympathetic chain ganglia
  4. Postgangionlic fibers: long, NE release
  5. Target
146
Q

Autonomic parasympathetic mechanism

A
  1. preganglionic cell bodies: craniosacral (III, VII, IX, X; S2-4)
  2. Preganglionic fibers: long, ACh release
  3. Postganglionic cell bodies: ganglia close to target
  4. Postgangionlic fibers: short, ACh release
  5. Target
147
Q

Ganglia

A

Peripheral collections of neuronal cell bodies

1) Autonomic ganglia
2) Sensory ganglia
3) satellite cells

148
Q

Autonomic ganglia

A

a. sympathetic chain ganglia: on thoracic vertebral bodies

b. parasympathetic ganglia: on the walls of the organs

149
Q

Sensory ganglia

A

Pseudounipolar neurons

a. cranial ganglia (V, VII, IX, & X)
b. Doral root (spinal) ganglia (spinal nerves)

150
Q

CNS Matter

A

Gray matter

white matter

151
Q

Gray matter

A

a. nerve cell bodies (nuclei)
b. dendrites & axons
c. glia

152
Q

White matter

A

a. nerve fibers (axons) - myelinated

b. glia

153
Q

Matter organization in brain

A

White in, gray out

154
Q

Matter organization in spinal cords

A

gray in, white out

155
Q

Subdivision of CNS

A
  1. Cerebral cortex
  2. Cerebellar cortex
  3. Spinal cords
156
Q

Cerebral cortex

A

a. 6 histological layers

b. integration of afferent & efferent info

157
Q

Cerebellar cortex

A

a. 3 histological layers: molecular, purkinje, and granula

b. coordinates balance and muscle tone

158
Q

Spinal cord organization

A

a. central gray matter
b. peripheral white matter
c. reflexes and basic integration

159
Q

Spinal cord central organization

A
  1. dorsal horn: sensory (afferent)
  2. lateral horn: autonomic
  3. ventral horn: motor (efferent)
160
Q

Dorsal horn

A

Sensory (afferent)

161
Q

Lateral horn

162
Q

Ventral horn

A

Motor (efferent)

163
Q

Major NT used in ANS

A

Acetylcholine

164
Q

When is ACh not used in ANS?

A

Postganglionic sympathetic uses NE

165
Q

In spinal cord, gray matter is ____ while white matter is ____.

A

Internal; external

166
Q

In cortex and cerebellum, gray matter is ____ while white matter is ____.

A

external, internal

167
Q

Steps in Neurodevelopment

A
  1. Formation of neural plate (notochord)
  2. Formation of Neural tube
  3. Cell proliferation
  4. Cell migration
  5. Axon/dendrite outgrowth
  6. Cell death
  7. Synapse formation
  8. Synapse elimination
  9. Myelination
  10. Critical periods
168
Q

Neural plate

A

Develops by Day 18 = notochord plate

169
Q

Neural tube

A

Closed at 3 weeks; starts closing in middle and goes cranial/caudal

170
Q

What happens if neural tube fails to close cranially/rostrally?

A

Anencephaly

171
Q

What happens if neural tube fails to close caudally?

A

Spinal bifida

172
Q

Division of neural tube cells

A

Start S-phase in pial (outer) surface and move towards ventricle (inner) surface by M-phase. Move back to pial after division.

173
Q

Neural tube has progenitors of the neurons and glia in the ____ and ____.

A

Brain, spinal cord

174
Q

Ventral-derived interneurons become ____

A

GABAergic cells

175
Q

Cortical-dervived pyramid neurons become ___

A

Glutamatergic cells

176
Q

Is transmitter choice due to inheritance or environment?

A

Inheritance but environment can overrule.

177
Q

Development of axons

A

Grow at tips (filopodium, then growth cone) followed by intercalar growth (axon)

178
Q

Semaphorin 3A mechanism

A
  1. Acts on apical dendrite, causing it to grow towards pial surface
  2. Axons repel it so grow away, towards ventricular zone
179
Q

Why to neurons reach the target they do?

A

Molecular gradients!

If molecules repel each other, cell bodies in high concentration area of one molecule will extend their axon towards area with lower concentration of repelling molecule.

180
Q

Can neurotransmitter receptors move after innervation?

A

Yes, usually scatter but will reorganize at innervation

181
Q

What happens with polyneuronal innervation?

A

If more than one neuron innervates a muscle fiber, it will lead to lots of competition between each neuron on each fiber. Cells will figure out which neuron will stay on the cell so that only on nerve per fiber (no competition).

182
Q

How does re-innervation happen?

A
  1. Partial de-nervation: cell loses a neuron
  2. Sprouting: Schwann cells move and bring axon
  3. Re-innervation: via a different pathway than original
183
Q

Pruning

A

During maturation, some connections will be pruned. Some general wiring happens early but will be readjusted and specified via pruning.

184
Q

Occular dominance

A

Separation of projections of left and right eyes to primary visual cortex –> creates patterns on cortex

185
Q

Critical period

A

Period during which synapses in the cortex are plastic and change with neuronal activity.

186
Q

What is the purpose of cortical folding?

A

Brings related regions closer together

187
Q

4 Basic properties of sensory systems

A
  • Modality
  • Location
  • Intensity
  • Duration
188
Q

Meissner’s corpuscle

A
  • Modality: respond to movement, deep touch
  • Location: 2nd smallest, tight
  • Intensity: constantly changing stimuli
  • Duration: short
  • Adaptation: rapid
189
Q

Merkel cells

A
  • Modality: sustained light touch (braille)
  • Location: smallest field size
  • Intensity: sustained touch
  • Duration: long
  • Adaptation: slow
190
Q

Pacinian corpuscle

A
  • Modality: vibrations/light touch
  • Location: targeted but dispersed wide
  • Intensity: constantly changing stimuli
  • Duration: short
  • Adaptation: rapid
191
Q

Ruffini endings

A
  • Modality: skin stretch
  • Location: wide range, nonspecific
  • Intensity: sustained touch
  • Duration: long
  • Adaptation: slow
192
Q

Touch is signaled primarily by those with ____ axons

193
Q

What type of axon is used in touch?

194
Q

Two point discrimination

A

With smaller receptive fields, 2 tips can be discriminated better. Measure of receptive field size and acuity.

195
Q

Receptive fields of cells are sharpened by ____, mediated by inhibitory interneurons

A

Lateral inhibition

196
Q

Lateral inhibition

A

Receptive fields of touch afferents are entirely excitatory, but second order neurons have opponent center-surround organization.

197
Q

Homunculus

A

Contralateral body surface maps onto the primary somatosensory cortex. Fixed by adulthood but can change via plasticity following injury.

198
Q

Nociception

A

Acute perception of a potentially damaging stimulus

199
Q

Inflammatory pain

A

Pathologic chronic pain associated with tissue damage and infiltration of immune cells

200
Q

Neuropathic pain

A

Pathologic chronic pain that may occur after nerve fibers are injured

201
Q

Analgesia

A

Lack of or reduced pain

202
Q

Hyperalgesia

A

Exaggerated response to a noxious stimulus

203
Q

Allodynia

A

Sensation of pain in response to a normal innocuous stimulus (ex: touch)

204
Q

Causalgia

A

Spontaneous burning pain that occurs long after seemingly trivial injuries

205
Q

Pain, itch, and temperature are signaled by the ____ axons

A

Smallest –> slowest

206
Q

Which axon type signals pain?

A

A-delta and C

207
Q

Which axon type signals temperature?

A

A-delta and C

208
Q

Which axon type signals itch?

209
Q

What is the mechanism for pain?

A
  1. A-delta fibers convey “1st pain”, releasing glutamate in spinal cord
  2. C fibers convey “2nd pain”, releasing glutamate, substance P, and CGRP in spinal cord
210
Q

How are nociceptors activated?

A

By chemical mediators released after tissue damage.

Ex: prostaglandin, histamine (immune)

211
Q

Basics of inflammatory pain

A
  1. Prostaglandin produced after skin cell damage
  2. Prostaglanding bind to blood vessels and dilate (widen)
  3. Neutrophils in blood released from vessels
  4. Neutrophils release inflammatory mediators
  5. Bind to nerve endings and activate
212
Q

What is the function of aspirin?

A

Block prostaglandin production, breaking inflammatory pain pathway

213
Q

Why is long term potential and depression important?

A
  1. underlies learning and memory
  2. Used in Alzheimer’s treatment
  3. Might be involved in Alzheimer’s itself
214
Q

Mechanism of long term potentiation

A
  1. Presynaptic neuron has glutamate (excitatory)
  2. Post synaptic has AMPA and NMDA receptors
  3. AMPA receptors open but NMDA can’t bc Mg2+ blocks the channel
  4. Increasing presynaptic stimulation pushes Mg2+ off and opens NMDA channels, allowing more Ca2+ in
  5. Leads to a larger EPSP
  6. Larger influx of Ca2+ activate kinases
  7. Increase strength and number of AMPA receptors
  8. Continue to increase potentiation of EPSP and therefore LTP
215
Q

Can LTP be transferred to neighboring synapses?

A

Yes –> coincident imputes at a neighboring synapse can trigger LTP at that one

216
Q

What determines LTP vs LTD?

A

Frequency of impulses!

Rate of impulses affects size of EPSP due to summation –> affects # of NMDA receptors unblocked –> determines depolarization –> affects amount of CA2+ entry

217
Q

What is LTD?

A

Similar to LTP, but:

  • Low freq –> lower Ca2+ (only NMDA open, no AMPA)
  • Low Ca2+ –> activate phosphatase instead of kinase
  • Oppositve effect from LTP
218
Q

Declarative memory

A

Episodic: facts, events, places

219
Q

Nondeclarative memory

A
  • Procedural: playing an instrument
  • Conditioning: Pavlov
  • Priming: patterns
  • Nociception: pain
220
Q

How is LTP related to learning?

A
  1. Learning related to hippocampus.
  2. Hippocampus has dendritic spines.
  3. Dendritic spines grow via LTP in a dish!
221
Q

Factors that enhance consolidation

A
  1. NTs: ACh and NE
  2. Stress (mixed effects)
  3. Attention
  4. Relevance
  5. Repetition
  6. Sleep
222
Q

Visual system

A
  1. Photoreceptors on retina
  2. Optic nerve
  3. Optic chiasm (split)
  4. Optic tract
  5. Lateral geniculate nucleus (LGN)
  6. Optic radiation
  7. Striate cortext
223
Q

Receptive field mapping

A

If on-center field:

  • light in center –> on
  • light in periphery –> off

Lateral inhibition!

224
Q

Layered structure of retina

A
  1. Light comes in
  2. Pigment epithelium
  3. Photoreceptors: rods and cones
  4. Horizontal and bipolar cells
  5. Amacrine cells
  6. Ganglion cells to optic nerve
225
Q

Distribution of photoreceptors on retina

A

Cones in the center, rods surround

226
Q

Proteins used by photoreceptors for color

A

Cone opsin (short, medium, and long) and rod rhodopsin

227
Q

Mechanism of bipolar cells

A
  1. Cones release glutamate
  2. Hyperpolarize on-bipolar cells
  3. depolarize off-bipolar cells
228
Q

Why is the surround of a receptive field antagonistic?

A

Horizontal cells feed back on surrounding photoreceptors and suppress their responses

229
Q

Ventral/dorsal divergence from primary visual cortex

A 
Ventral = what
dorsal = where
230
Q

Crista ampularis of semi-circular canals in ear

A

fluid movement moves hair cells, which depolarize. Signal travels via tight junctions

231
Q

Otolith organs of ears

A

Vestibular sense!
Utricle: forward acceleration (horizontal)
Sacculus: gravitational acceleration (vertical)

232
Q

Organ of cord in ears

A

Hearing via inner hair cells

233
Q

Hair cell mechanism

A
  1. Hair cells pushed in one direction stretched trp link between channels on cells
  2. Depolarize one (open Na/Ca channels)
  3. Link bounces back
234
Q

Traveling waves along basilar membrane

A

As freq of sound decreases, peaks are further from stapes

235
Q

What is the relationship between taste and olfaction?

A

Combination with olfaction leads to sense of taste

236
Q

What mechanism do odorant receptor neurons use?

A

GPCR (metabotropic)

  1. Odorant to cilia on outer olfactory epithelium
  2. Olfactory receptor cells to olfactory bulb
  3. Bundles of olfactory receptor cells to bulb = cranial nerve 1
  4. Glomeruli of olfactory bulb connect to mitral cells and tufted relay neurons
  5. Go to olfactory cortex
237
Q

What mechanism do NSAIDs use to reduce pain?

A

Block prostaglandin synthesis

238
Q

A key molecular event to increase postsynaptic responsiveness to glutamate during hippocampal LTP?

A

Phosphorylation of AMPA receptors to increase their conductance

239
Q

What can enhance both LTP and is used to improve memory in Alzheimer’s disease?

A

Inhibition of acetylcholinesterase to increase acetylcholine levels

240
Q

Simtulation of the center of the receptive field of an “on” center retinal ganglion cell with light results in ___

A

The cell firing rapidly

241
Q

When the hair bundle is deflected towards the tallest steocilium, __ enter the cell via selective channels near the tips of the stereo cilia and the hair cell ____

A

k+ ; depolarizes

242
Q

During development, axon growth is controlled by:

A
  • growth stimulating molecules on cell surface and intracellular matrix (laminin)
  • growth inhibiting molecules on cell surface and in extracellular matrix (ephori’s)
  • diffusible molecules that attract axons (entrain)
  • diffusible molecules that repel axons (semaphorin)
243
Q

Mechanism of vestibular system

A
  1. Rotation of head moves endolymph (liquid) inside semicircular canal that corresponds with the plane of movement (L-R, up down, shake).
  2. Endolymph moves to ampulla with hair cells with stereocilia at top that move to release NT to brain
244
Q

Mechanism for taste

A
  1. Taste buds on tongue have multiple taste cels with microvilli (taste hairs)
  2. Microvilli come in contact with taste chemicals and depolarize
  3. Send signals to thalamus and then gustatory cortex
  4. Encode for sweet, salty, bitter, savory/umami, sour
245
Q

How long does the spinal cord extend along the vertebrae?

A

Extends to L1/L2 level

246
Q

Number of spinal nerves

247
Q

Order of spinal nerves

A
  1. 8 cervical
  2. 12 thoracic
  3. 5 lumbar
  4. 5 sacral
  5. 1 coccygeal
248
Q

What is the impact of an injury higher on the spinal cord compared to lower?

A

Higher injuries lead to greater deficit

249
Q

Conus Medullaris

A

End of spinal tail

250
Q

Cauda Equina

A

End of spinal nerves

251
Q

Spinal cord meninges

A
  1. Epidural space: created by loose attachment of dura mater
  2. Dura mater
  3. Subdural space
  4. Arachnoid mater
  5. Subarachnoid space: CSF
  6. Pia mater: denticulate ligaments - support spinal cord
252
Q

Gray matter of spinal cord

A
  1. Anterior (ventral) horn
  2. Lateral horn: Intermediolateral cell column
  3. Posterior (dorsal) horn
253
Q

Anterior (ventral) horn

A

Gray Matter

  1. Somatic motor - skeletal muscle
  2. Cervical enlargement (C5-T1)
  3. Lumbosacral enlargement (L1-S3)
  4. Anterior (ventral) rootlets
254
Q

Specific motor distribution of anterior horn

A

Somatotopic homunculus: Proximal areas of horn regulate proximal muscles of limbs, vice versa with distal

255
Q

Lateral horn (intermediolateral cell column)

A

Gray matter

  1. T1-L2 (preganglionic sympathetic) & S2-S4 (pregangionlic parasympathetic)
  2. Autonomic (visceral motor - smooth muscle)
256
Q

Posterior (dorsal) horn

A

Gray matter
Sensory

  1. Nucleus gracilis (lower extremity) - in medulla
  2. Nucleus cuneatus (upper extremity) - in medulla
  3. Nucleus dorsalis (of Clark)
  4. Posterior (dorsal) rootlets - posterior (dorsal) root
  5. Posterior (dorsal) root ganglion (sensory cell bodies)
257
Q

White Matter of spinal cord

A
  1. Ascending tracts (sensory)

2. Descending tracts

258
Q

Ascending tracts of white matter in spinal cord

A
  1. Posterior (dorsal) column sensory pathways

2. Lateral column sensory pathways

259
Q

Posterior (dorsal) column sensory pathways (ascending - white matter)

A

General sensation

  1. Fasciculus cuneatus (upper extremity)
  2. Fasciculus gracilis (lower extremity)
260
Q

Lateral column sensory pathways (ascending - white matter)

A
  1. Spinothalamic tract: pain and temperature

2. Spinocerebellar tracts: spine to cerebellum –> position in space

261
Q

Fasciculus cuneatus

A
  • ascend via here (lateral) if above T6
  • Upper extremity general sensation
  • Synapse in nucleus cuneatus
262
Q

Fasciculus gracilis

A
  • ascend via here (medial) if below T6
  • Lower extremity general sensation
  • Synapse in nucleus gracilis
263
Q

Spinothalamic tract

A

Pain and temperature

264
Q

Spinocerebellar tract

A

Spine to cerebellum –> position in space

265
Q

Descending tracts of white matter in spinal cord

A
  1. Lateral column motor pathways

2. Anterior (ventral) column pathways

266
Q

Lateral column motor pathways (descending - white matter)

A
  1. Rubrospinal tract: don’t use

2. Corticospinal tract: voluntary movement (skeletal)

267
Q

Rubrospinal tract

A

Don’t use

268
Q

Corticospinal tract

A

Voluntary movement skeletal)

269
Q

Anterior (ventral) column pathways (descending - white matter)

A
  1. vestibulospinal tract: balance
  2. Reticulospinal tract: varied
  3. Tectospinal tract: visual
  4. Anterior corticospinal: trunk musculature
270
Q

Vestibulospinal tract

A
  • White matter
  • descending
  • anterior ventral column pathways
  • Act on spinal cord neurons for proper control of head and neck musculature in balance and posture.
271
Q

Reticulospinal tract

A
  • White matter
  • descending
  • anterior ventral column pathways
  • Coordinated postural movements
  • Descending autonomic and pain modulation information
272
Q

Tectospinal tract

A
  • White matter
  • descending
  • anterior ventral column pathways
  • Visual spatial orientation
  • Act on contralateral motor neurons in upper spinal cord mediating head and neck musculature allowing for proper head and neck postural reflexes based on visual information.
273
Q

Anterior corticospinal

A
  • White matter
  • descending
  • anterior ventral column pathways
  • Bilaterally innervate alpha motor neurons that control trunk musculature, where coordination b/t the muscles on both sides of the body is important.
274
Q

Central canal in Spinal Cord

A

Contains CSF

275
Q

The spinal cord is shorter than the vertebral column and ends at the ____.

A

1st/2nd lumbar vertebra

276
Q

In the spinal cord gray matter, the anterior horn has ____ neurons, the lateral horn has ____ neurons, and the posterior horn has ____ neurons.

A

Motor - Skeletal
Autonomic
Sensory

277
Q

Function of posterior (dorsal) columns

A
  1. Fine touch - Meissner corpuscles
  2. Vibration sensation/deep touch - Pacinian corpuscles
  3. Proprioception - muscle spindles, Golgi tendon organs (ear)
  4. Stereognosis - recognize an object by touch without visual cues
278
Q

Pathway of posterior (dorsal) columns and medial lemniscus

A
  1. Myelinated, rapid conducting axons enter via posterior (dorsal) root ganglion/posterior (dorsal) root neurons (first order neurons)
  2. Ascend in posterior (dorsal columns (no synapse)
  3. In the caudal medulla
  4. 2nd order neurons cross over in medulla oblongata
  5. Ascend in contralateral medial lemniscus
  6. Synapse in thalamus (VPL)
  7. 3rd order neurons ascend through internal campus to cerebral cortex (post central gyrus)
279
Q

Dermatomes

A

Show cervical levels and connection to body –> creates patterns important for clinical practice

280
Q

Function of spinothalamic tract

A
  1. Pain - free, unmyelinated nerve endings in skin

2. Temperature - free, unmyelinated nerve endings in skin

281
Q

Pathway of spinothalamic tract

A
  1. Enter via posterior (dorsal) root ganglion / posterior (dorsal) root (1st order neurons)
  2. Synapse in posterior (dorsal) horn)
  3. 2nd order neurons cross over at the spinal cord level of entry (anterior white commissure)
  4. Ascend in contralateral spinothalamic tract (anterolateral tract)
  5. Synapse in thalamus (VPL)
  6. 3rd order neurons ascend through internal capsule to cerebral cortex (post central gyrus)
282
Q

Lesions of posterior (dorsal) columns

A
  1. ipsilateral deficit in spinal cord lesion

2. Contralateral deficit in brain stem/cortical lesion

283
Q

Lesions of spinothalamic tract

A
  1. Contralateral deficit in spinal cord lesion

2. ipsilateral deficit in brain stem/cortical lesion

284
Q

Function of corticospinal tract

A

Voluntary motor (skeletal muscle)

285
Q

Pathway of corticospinal tract (descending - motor)

A
  1. Arise in cerebral cortex (precentral gyrus or premotor cortex)
  2. Descend through internal capsule, cerebral peduncle in midbrain
  3. Cross over in caudal medulla (pyramidal decussation) becoming the lateral corticospinal tract
  4. Descend through spinal cord (contralateral side)
  5. Synapse in anterior (ventral) horn on anterior (ventral) horn cells or on interneurons
  6. Lower motor neurons pass through anterior (ventral) root to spinal nerve to supply skeletal muscles
286
Q

Ascending (sensory) white matter tracts are found in the ____ & ____ columns.

A

Lateral, posterior

287
Q

Pain & temperature sensation travels by a different pathway than general sensation. Which pathway decussates in spinal cord?

A

Pain & temperature only

288
Q

The descending motor pathway (corticospinal tract) decussates in the _____.

A

Brain stem (medulla oblongata)

289
Q

Define two-point discrimination.

A

Way to determine discrimination b/t 2 points

290
Q

What receptors are activated in the 2-point discrimination test?

A

Merkel cells: smallest receptive field

291
Q

Does the measurement on the 2-point discrimination differ between the fingertip and the arm or other locations?

A

Yes, much smaller on finder than arm or elsewhere

292
Q

Why do you think the measurements may differ in 2-point discrimination between finder and other areas?

A

Finger has smaller receptive fields

293
Q

Which skin areas have a higher density of receptors?

A

Finger has highest density of receptors, followed by palm, forearm, etc.

294
Q

Explain the concept of receptive field.

A

Region that stimulated will change nerve’s response –> can be positive or negative response

295
Q

What are the implications of having different sensitivities in different skin areas/

A

Areas with higher sensitivity are more important for survival evolutionarily (ex: fingers)

296
Q

What is the pathway followed for info form sensory receptors in the skin to get to the brain?

A
  • 1st order neurons: primary sensory afferent - cell body in dorsal root ganglia.
  • 2nd order neurons: Interneurons that connect to 1st and cross over in medulla
  • 3rd order neurons: thalamus to somatosensory cortex
297
Q

Which two sensory systems are involved in rubber hand illusion?

A

Somatosensation and vision

298
Q

The pathway that mediates reflexes involve what types of neurons?

A

Sensory and motor

299
Q

Characterization of the ionic changes in an axon that produce an AP

A
  1. Influx of sodium

2. Outflux of potassium

300
Q

What would be impaired if tyrosine hydroxylase is decreased?

A

Dopamine and noradrenaline

301
Q

In temporal summation, a ________ of Aps in the presynaptic neuron elicits postsynaptic potentials that add together.

A

high frequency

302
Q

What is the mechanism by which acetylcholine is inactivated in the synaptic cleft?

A

Enzymatic breakdown

303
Q

_____ provide the main cytoskeletal “track”s for axonal transportation.

A

Microtubules

304
Q

What mechanism would work to design a drug that penetrates the CNS?

A

Adjunctive administration of vasoactive substances that can permeate tight junctions between endothelial cells.

305
Q

____ afferents have small receptive fields and produce sustained responses.

306
Q

The first order neurons of somatosensory pathways typically have bodies in the _______.

A

Dorsal root ganglia

307
Q

The ability of synapses to strengthen or weaken over time in response to increases or decreases in their activity.

A

Synaptic plasticity

308
Q

Types of axons

A
  • A alpha
  • A beta
  • A delta
  • C
309
Q

Properties of A alpha axons

A

Diameter: 13-20
Speed: 80-120
Receptors: Proprioceptors/skeletal muscle

310
Q

Properties of A beta axons

A

Diameter: 6-12
Speed: 35-75
Receptors: Mechanoreceptors (touch)

311
Q

Properties of A delta axons

A

Diameter: 1-5
Speed: 5-30
Receptors: Pain/temp

312
Q

Properties of C axons

A

*Not myelinated!
Diameter: 0.2-1.5
Speed: 0.5-2
Receptors: Pain/temp/itch

313
Q

Diameter/speed of axons

A

Alpha > beta > delta > C

BMPH 1 (8 decks)

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