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CIF > Neuro > Flashcards

Neuro Flashcards

1
Q

What are the function of dendrites?

A

Post-synaptic signal conduction and integration - collects synaptic input from many different neurons

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2
Q

What are the function of the axonal hillock(/soma)?

A

Generation of AP

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3
Q

What is the function of the axon?

A

Propagation of AP

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4
Q

What are temporal and spatial summation?

A

Temporal: converts a rapid series of weak pulses from a single source into one large signal
Spatial: converts several of weak signals from different locations into a single large one

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5
Q

What is the length constant?

A

Quantifies the decrease in signal. The bigger the length constant the bigger the chance of an AP (needs to be the length of the dendrite to generate an AP)

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6
Q

But not all dendrites are <1 length constant, so what can they do?

A

Dendrites are capable of effectively increase the length constant and amplify the signal via voltage-gated ion channels (Cav). Dendrites debranch –> cell diameter becomes larger –> allows for activity along cable –> length constant becomes longer

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7
Q

What causes the unique low threshold in the axon hillock?

A

High density of Nav (app. 2000 channels/µm2)

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8
Q

Why is the signal unidirectional?

A

Due to the refractory period (channels inactivate before they close, ergo they can’t be activated for a while)

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9
Q

True or false: most info within a neural system is encoded in the temporal pattern of APs

A

True

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10
Q

What are rate coding vs temporal coding?

A

Rate: info is contained in the fire rating - number of spikes, not timing
Temporal: info is contained in the timing of spikes, such as first spike latency and inter-spike periods

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11
Q

How is the axonal conduction of APs tuned for speed?

A

Myelin: oligodendrocytes in CNS, Schwann cells in PNS

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12
Q

What does an increased diameter lead to?

A

A decrease in intracellular resistance (Ri)

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13
Q

What is the time constant?

A

Quantifies the rate at which charge spreads. T = RmCm
Rm = resting membrane resistance
Cm = membrane capacitance

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14
Q

What are and what are the function of the internodes in myelin sheats?

A

Myelinated regions
Function: Works as an insolater - AP “jumps” from node to node (saltatory conduction)

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15
Q

What are and what are the function of the nodes of Ranvier in myelin sheats?

A

Regions not covered by myelin, with a high density of ion channels
Function: act as mini axonal hillocks

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16
Q

How does the myelin effect the Rm and Cm?

A

High Rm, low Cm –> higher rates of AP propagation

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17
Q

What can multiple sclerosis lead to?

A

Demyelation –> disrupts the CNS ability to effectively conduct electrical signals –> increase the Cm, decrease the Rm
Results in a wide range of syndroms

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18
Q

What are the different types of synapses?

A

Axosecretory: directly into bloodstream
Axoaxomatic
Axodendritic
Axoextracellular: secretes into extracellular fluid
Axosomatic
Axosynaptic

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19
Q

What are the two types of synapses?

A

Electrical and chemical

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20
Q

How do electrical and chemical synapses differ?

A

Electrical: smaller distance (3.5 nm), gap junction, carries info as ion currents, no delay, didirectional, no plasticity

Chemical: longer distance (20-50 nm), presynaptic vesicle, chemical transmitter, at least 0.3 ms delay (usually 1-5 ms), unidirectional, plasticity

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21
Q

Where are chemical- and electric synapses found?

A

Chemical: everywhere
Electrical: heart and secretory cells

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22
Q

What are the two types of vesicles in chemical synapses (presynaptic)?

A

Clear secretory: enzyme synthesized transmitters, concentrated at active zones

Dense core: neuropeptides, dispersed at the presynaptic terminal

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23
Q

Describe some properties of the post synaptic side.

A

Dense neurotransmitter receptor concentration, downstream molecular signaling proteins, often specialized dendritic architecture (spines)

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24
Q

What are some NTs derived from amino acids?

A

GABA, glycine

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25
Q

What are some NTs derived from mono amines?

A

Acetylcholine, serotonine, histamine

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26
Q

What are some NTs derived from catecholamines?

A

Dopamine, adrenaline, noradrenaline, DOPA, tyrosine

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27
Q

What are some NTs derived from peptides?

A

Oxytocin, comatostatin, arginine vasopressin, substance P

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28
Q

How can NTs be synthesized?

A

Enzyme or ribosome

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29
Q

What are the properties of enzyme synthesized NTs?

A

Made throughout the neuron, selectively packed into vesicles, often recovered after release, activates both ionotropic and metabotropic receptors

30
Q

What are the properties of ribosome synthesized NTs?

A

Synthesized on rough ER –> packed in golgi = long transport, not recovered, activates only metabolic receptors

31
Q

What are the two types of receptors NTs bind to?

A

Ionotropic: single receptors, but protein complexes, opens upon binding, very fast response, different effects of changing membrane permeability

Metobatropic: GPCRs, slower response (up to days), produce modulatory responses, that typically change neuronal excitability

32
Q

The same NT can have different effects based on the receptor it binds to. Use ACh as an example.

A

When ACh binds to nicotinic ACh receptor (ionotropic):
Excitatory stimuli, cation channels activation. Found in: neuromuscular junction

Muscarinic M2/4 (metabotropic):
Inhibatory, K+ channels activation. Found in: cardiac muscles

M1/3/5: hyperexcitable, inhibits K+ channels. Found in: sympathetic neurons

33
Q

Describe the properties of excitatory synapses.

A

Often on dendrites, most use glutamate, most use ionotropic Rs, generate EPSP by a non-selective cation channel, EPSP is usually very small: 0.01 - a few mV –> need for summation

34
Q

Decribe the properties of inhibitory synapses.

A

Often on cell bodies, most use GABA or glycine, ionotropic, generate IPSP by activation of Cl- selective channels bringing Vm–> E_Cl, IPSPs oposes EPSPs. GABA is the source of action of alcohol and other anaesthetics

35
Q

What are the two main classes of ionotropic glutamate receptors?

A

NMDA (slow phase, voltage gated, high Ca2+ permeability, Mg2+ block) and AMPA (fast phase, ligand gated cation channel)

36
Q

Why must synaptic inhibition be tightly regulated?

A

Too much –> coma
Too littel –> seizure

37
Q

Decribe the properties of modulatory synapses.

A

Can be found throughout neurons, use neuropeptides and monoamines, use metabotropic Rs

38
Q

What are the difference between spatially focused and widely divergent neurons?

A

Spatially focused: only a few synapses close to each other - fast, specific, spatially organized
Widely divergent: a lot of synapses - mood, sleep, awareness

39
Q

Describe the general effect of NA and adrenalin on the brain, and when it is active.

A

Active during: new, unexpected, non-painful sensory stimuli in the environment
Role: general arousal of the brain during interesting events
Regulation of attention, arousal, sleep/awake, behavioural flexibility, anxiety, pain and emotion
“mobilizing the brain”, directing resources away from maintenance toward active movement

40
Q

Describe the general effect of serotonine on the brain, and when it is active.

A

Active during: wakefulness
Role: regulation of mood, memory processing, sleep and cognition
Specifically in control of sleep/wake cycles
Modulation of certain emotional behaviours

41
Q

What are some diseases linked to altered serotonin signaling in the CNS?

A

Depression and anxiety (reduced levels)
Obsessive-compulsive disorder (depletion of serotonin)
Falling in love has recently been shown to result in depleted serotonin levels –> might explain the obsessive component of this phase

42
Q

What is the function of the neuronal microenvironment?

A

To protect the brain from itself and the rest of the body. Consists of fluids, barriers and cells

43
Q

What is the CSF?

A

The cerebrospinal fluid, secreted from the choroid plexus cells (epithelial cells lining the ventricles)
Communicates and stabalizes fluid around the neurons

44
Q

What is the fluid composition of CSF that varries most from BECF?

A

Low [K+] app. 2.9 mM, low [amino acids] app. 0.7 mM, low [proteins] app. 0.03 g/dL

45
Q

Where do we find CSF?

A

In the ventricles, subarachnoidal space, and spinal cord
The brain floats in CSF

46
Q

What is CSF reabsorped by, and what is reabsorped?

A

Arachnoid granulation and villi

47
Q

Descripe what is secreted/absorped by choroid plexus.

A

Secreted: NaCl and NaHCO3, and osmotically driven H2O

Absorped: K+ and metabolites of serotonin and dopamine

48
Q

What is the BECF?

A

Brain ECF
Similar to CSF and plasma, but not identical

49
Q

Where is BECF found?

A

Around neurons, glia cells and capillaries in the brain

50
Q

What is the role of BEFC?

A

Plays a role in cell-cell communication

51
Q

Describe the properties of BEFC.

A

Tortuous (snoede) and limiting diffusion
Decreases with cell swelling
Route for O2, CO2, catabolized transmitters, and spilled over amino acids
Large changes in extracellular ion concentrations, e.g., K+
Communicates with CSF

52
Q

What can cause cell and brain swelling (edema, when fluid is drawn from capillaries)?

A

Traumatic brain injury, ischemic stroke, intracerebral haemorrhage, brain infection, tumor, low Na+

53
Q

What is the function of the BBB?

A

Tight control of transfer of nutrients and ions
Stabalizes CSF and BECF

54
Q

Describe the anatomy of the BBB.

A

From inside-out: Capillary, endothelial cell, pericyte, basement membrane, astrocyte

55
Q

Describe the transfer properties of the BBB.

A

Can pass: uncharged and lipid-soluble molecules (gases, ethanol, caffeine)
May pass (needs protein to pass): glucose

56
Q

What can altered BBB permeability cause?

A

Multiple sclerosis, stroke, brain tumors, metastatic tumor cells, CNS infections

57
Q

What are the circumventricular organs?

A

Very small contact areas without BBB
Produce prehormones, important for regulation of body fluids, located where the brain needs to secrete something (e.g., melatonin, oxytocin) or sense something

58
Q

What are the most prominent cells in the CNS?

A

Glial cells - comprise half of the volume of the brain and outnumber neurons 10:1

59
Q

What are the main glial cell types in the CNS?

A

Astrocytes, oligodendrocytes, and microglial cells

60
Q

What are the general properties of glial cells?

A

Non-excitable, can proliferate

61
Q

What are the functions of oligodendrocytes?

A

Sustain myelin, involved in pH regulation and iron metabolism

62
Q

True or false? Oligodendrocytes are targeted by immune cells in MS.

A

True

63
Q

What are the function of astrocytes?

A

Supply fuel to neurons in form of lactic acid, permeable to K+, synthesize and take up neurotransmitters

64
Q

How are astrocytes coupled?

A

Via gap junctions (connexins, not permeable to Ca2+)

65
Q

Describe the K+ homeostasis of astrocytes.

A

Na-K-ATPases, inwardly rectifying K+ channels, Na-K-Cl-transporters facilitate K+ uptake by astrocytes

66
Q

Describe how astrocytes are involved in the glutamate cycle.

A

Takes up glutamate (via EAAT1/2) –> converts it to glutamine (via glutamine synthetase) –> secretes glutamine (via SNAT3/5) –> glutamine taken up by neurons (via SNAT1/2) –> resynthesized as glutamate (by glutaminase)

67
Q

Describe the communication properties of astrocyte.

A

They are Ca2+ excitable (does not communicate via APs). They release gliotransmitters (e.g., ATP, glutamate, prostglandins). Release trophic factors, cytokines, and factors affecting blood flow. Express specialized receptors e.g., purinergic.

68
Q

Describe how ATP is involved in astrocyte communication.

A

Extracellular ATP stimulates intracellular release of Ca2+. ACs communicates in Ca2+ waves stimulate by extracellular ATP

69
Q

What are the function of microglial cells?

A

They are the immunoreactive cells of the brain aka. macrophages of the CNS

70
Q

What are the microglial cells associated with in the PNS?

A

Pain transmission

CIF (11 decks)

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