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Neuroanatomy > Anatomy and Physiology of Cells of the NS > Flashcards

Anatomy and Physiology of Cells of the NS Flashcards

1
Q

Soma

A

-Cell body of neuron
-Contains nucleus and most other organelles
-Common site of synaptic input (afferent)
-Contain receptors for neurotransmitters (subsynaptic membrane)

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2
Q

Dendrites

A

-Extension of the soma
-Common site of synaptic input (afferent)
-Contain receptors for neurotransmitters (subsynaptic membrane)

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3
Q

Axon hillock

A

-Anatomical transition from soma to axon
-Physiological transition from graded potential to action potential (AP)
-initial segment - has lowest graded threshold for AP

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4
Q

Axon

A

-Long thin, efferent process
-Many microtubules and microfilaments to maintain shape

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5
Q

Axon transport

A

-Up to 400mm per day

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6
Q

Anterograde transport

A

-Movement of materials (neurotransmitters, proteins, etc) from soma towards synaptic knobs

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7
Q

Kinesin

A

-Protein motor molecule

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8
Q

Retrograde transport

A

-Movement of materials (often waste) from synaptic knobs towards soma

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9
Q

Dynein

A

-Protein motor molecule

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10
Q

What surrounds the axon?

A

-May be surrounded by myelin with nodes of Ranvier

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11
Q

AP conduction speed _________ with _________ diameter & ________myelin.

A

increases, increased, increased

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12
Q

Fibers with largest diameter, most myelin

A

Sensory (afferent) A-alpha
Motor (efferent) Ia, Ib, II
Conduction speed: 70-120m/sec

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13
Q

Fibers in between

A

Sensory (afferent) A-beta
Motor (efferent) III
Conduction speed: 5-30m/sec

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14
Q

Fibers with smallest diameter, least myelin

A

Sensory (afferent) C
Motor (efferent) IV
Conduction speed: 0.5-2m/sec

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15
Q

Synaptic knobs (terminal boutons)

A

-Swelling at end of axons
-Contain structures of synaptic transmission (esp. vesicles of neurotransmitter)

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16
Q

Membrane potential

A

-Due (primarily) to differences in [Na] & [K] between ICF and EFC
-Also [Cl] & [Ca]
-When no signal is being sent = resting membrane potential
[-70mV] varies among neurons & types of neurons

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17
Q

Changes in membrane potential (=information)

A

-Depolarization: toward 0mV
-Repolarization: return from depolarization toward -70mV
-Hyperpolarization (overshoot): more negative than -70mV

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18
Q

Graded (local) potentials

A

-Small, decremental voltage changes in response to some stimulus (receptor, neurotransmitter, etc.)
-Larger stimulus causes larger voltage change (=graded)
-Can be excitatory (depolarizing) or inhibitory (hyperpolarizing)
-Created/located in the dendrites and soma

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19
Q

Action potential (AP)

A

-Huge, stereotypical, non-decremental, unidirectional change in membrane potential that is propagated along axon

20
Q

AP is formed if threshold voltage is met (All or none rule)

A

-Initial segment of axon hillock (site of transition from local potential to AP)
-Threshold varies among neurons, even of the same type (usually around -55mV)

21
Q

Propagation along axons

A

Contiguous or Saltatory

22
Q

Contiguous Conduction

A

-On unmyelinated fibers
-Slower
-Must be recreated on every portion of the membrane

23
Q

Saltatory Conduction

A

-On myelinated fibers
-Much faster
-AP “jumps” from one Node of Ranvier to the next

24
Q

Synapses

A

-Functional connection between neurons
-Usually axodendritic or axosomatic (but can be axoaxonic)
-Usually functions by transforming AP signal into chemical signal (neurotransmitter) that crosses the synaptic cleft

25
Q

Presynaptic neuron

A

Releases neurotransmitter (sends information)

26
Q

Postsynaptic neuon

A

Senses neurotransmitter (receives information)

27
Q

EPSP - Excitatory Post-Synaptic Potential

A

-Depolarizes postsynaptic cell
-Moves membrane potential closer to threshold
-Makes it more likely to fire an AP

28
Q

IPSP - Inhibitory Post-Synaptic Potential

A

-Hyperpolarizes postsynaptic cell
-Moves membrane further from threshold
-Makes it less likely to fire an AP

29
Q

Neurotransmitters

A

Chemical messengers (hundreds)

30
Q

Excitatory (fast)
[neurotransmitter]

A

Acetylcholine (ACh), glutamate (primarily CNS; estimated at 90%+ of synapses)

31
Q

Inhibitory (fast)
[neurotransmitter]

A

GABA (gamma-aminobutyric acid; mostly brain), glycine (mostly spinal cord)

32
Q

Second messenger mediated (slow; many are either excitatory or inhibitory, depending on receptor)

A

-Catecholamines (epinephrine & norepinephrine; dopamine)
-Serotonin
-Neuropeptides (neuromodulators)
-Several neurotransmitters have both fast & slow receptors (ACh, glutamate, GABA)

33
Q

Drugs and diseases acting at synapse

A

-Curare
-Botulsim
-Tetanus
-Myasthenia Gravis

34
Q

Curare

A

-Toxin that blocks ACh receptors (nicotinic receptors)
-Causes flaccid paralysis

35
Q

Botulsim

A

-Toxin prevents exocytosis of ACh (esp @ neuromuscular junction)
-Causes flaccid paralysis

36
Q

Tetanus

A

-Toxin is transported by retrograde axonal transport to inhibitory neurons of spinal cord
-Blocks glycine release
-Prevents inhibition of motor neurons; causes spastic paralysis

37
Q

Myasthenia Gravis

A

-Autoimmune destruction of ACh receptors; although ACh release is normal
-Muscle contraction decreases (esp. to repeated contractions)
-Causes weakness, double vision, etc.

38
Q

Glial cells

A

90% by number; 50% by volume

39
Q

Astrocytes (CNS)

A

-Connective tissue of the CNS
-Hold neurons in position
-Blood-brain barrier - chemically protect neurons

40
Q

Oligodendrocytes (CNS)

A

-Myelinate axons in CNS
-Larger, myelinate many regions of multiple axons

41
Q

Schwann cells (PNS)

A

-Myelinate axons in PNS
-Smaller, myelinate specific region of one axon
-Provide support, myelinate, and have phagocytotic role

42
Q

Ependymal cells (CNS)

A

-Line ventricles, central canal of the spinal cord
-Choroid plexus: specialized ependymal cells within the ventricles that produce CSF
-Function: secretory, absorptive and CSF circulatory role

43
Q

Microglia (CNS)

A

-Phagocytosis of degenerative debris of CNS
-Immune function

44
Q

Charcot-Marie Tooth Disease
(family of disorders)

A

-Uncurable; genetic (most common inherited neurological disorder: 40 in 100,000)
-Peripheral neuropathy – caused by gap junction channelopathy
-Progressive loss of touch sensation, muscle weakness & wasting
-Affects longest axons first
-(i.e., feet first, then legs, then hands, then arm)
-Mechanism/molecule unknown, but causes demyelination of PNS

45
Q

Guillain-Barre Syndrome

A

-Autoimmune inflammation (after viral infection) where macrophages attack and destroy myelin in the PNS (fairly rare: 1 in 100,000)
-Can cause rapid (12 hours! to 2 week) symptoms of weakness, loss of sensation
-often affects breathing muscles & patients require ventilation
-Patients often recover significantly, but 20% are unable to walk unaided after 6 months

46
Q

Multiple Sclerosis

A

-Autoimmune attack on CNS myelin (approx. 28 in 100,000)
-Symptoms vary widely – depending on specific area of damage
-Chronic & debilitating changes in sensation, movement, mood and/or cognition

Neuroanatomy (20 decks)

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