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A & P 2 > Lecture 2: Neuro > Flashcards

Lecture 2: Neuro Flashcards

1
Q

What principal does the action potential follow

A

All or nothing

- a cell will either fire or not

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2
Q

What initiates the action potential

A

The sum (graded signal) of the inputs at the cell of the dendrites or the cell body

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3
Q

What can generate input that initiates action potential

A
  • Neighbouring neurons

- direct stimulation (heat,light,chemicals,etc) that work on the opening and closing of sodium channels

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4
Q

The sum of all the inputs must be large enough to overcome what in order for action potential to take place and travel along the axon

A

Firing threshold

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5
Q

What are the 4 steps of action potential

A
  1. Resting state
  2. Depolarization
  3. Repolarization
  4. Hyperpolarization
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6
Q

What is the resting state step

A
  • the membrane is maintained at its resting potential

- no net movement of ions

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7
Q

What is depolarization step of action potential

A
  • loss of the difference in charge btw the inside and outside of the plasma membrane
  • influx of sodium
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8
Q

What is the repolarization step of action potential

A

-change in membrane potential that returns it to a negative value just after the depolarization

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9
Q

What is the hyperpolarization step of action potential

A
  • is a change in cell’s membrane potential that makes it more negative
  • it is the opposite of a depolarization
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10
Q

Typically the action potential generates a voltage change of how much in the membrane

A

110-120 mV (0.1V)

- membrane potential arises from disparity of ions

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11
Q

How long do action potentials last

A

approx. 1 msec (1/1000 of a second)

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12
Q

What is the energy that corresponds to the voltage generated in typical action potential

A

~10(-20exponent) J

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13
Q

What do you call the period during an action potential when another action potential cannot be generated

A

Refractory periods

-reload times

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14
Q

During what steps in the action potential is the refractory period

A

from the beginning of depolarization until the end of repolarization
(same duration as the action potential proper)

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15
Q

What occurs with the sodium and potassium channels during refractory period

A
  • sodium channels are inactive

- potassium channels are open

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16
Q

If there is a potent input signal during refractory period will it generate a second action potential

A

NO

- no matter how potent there can be no other action potential generated

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17
Q

When is the relative refractory period

A

from the end of repolarization to the end of hyperpolarization

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18
Q

What happens at the end of hyperpolarization

A

resting membrane potential is reached

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19
Q

Can an action potential be produced during relative refractory period

A

It is possible but the stimulation must be stronger than when the neuron is at rest

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20
Q

Why does relative refractory period require stronger stimuli to produce AP

A
  • the membrane is hyperpolarized so it is farther away from the threshold
  • many channels have not returned to their resting state
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21
Q

What does the ALL or NONE principle stipulate about action potentials

A

-they have similar intensities (same change in membrane potential)

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22
Q

What 2 characteristics do you examine to differentiate between a weak or a strong stimulus

A
  • frequency

- summative

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23
Q

What is frequency affect on intensity of the stimulus

A
  • it varies in function with the intensity of the stimulus

- greater the frequency of an AP the greater the intensity

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24
Q

What is summative affect on intensity of the stimulus

A
  • an intense stimulus can often stimulate more sensory neurons
  • recruitment of many neurons increases the intensity of the stimulus
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25
Q

What 2 factors affect the speed of propagation of the AP

A
  • diameter of the axon

- degree of myelination (saltatory conduction)

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26
Q

Physics states:

-the resistance to the passing of an electric current is inversely proportional to …

A

the diameter of the canal where it is transmitted

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27
Q

Physics states:

-the greater the diameter..

A

the less resistance to current (=the more conduction)

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28
Q

What do the synapses allow for

A

-transfer of info from 1 neuron to the next or from 1 neuron to an effector cell

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29
Q

in the neurons from the boundaries of the synapse what are presynaptic and postsynaptic

A
  • presynaptic (neurons that send info)

- postsynaptic (neurons that receive info

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30
Q

How to the neurons from the boundaries of the synapse work

A

1 neuron receives information from millions of presynaptic neurons & sends them to millions of postsynaptic neurons

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31
Q

What are the 3 names of synapses based on where they connect

A
  • axodendritic
  • axosomatic
  • axoaxonal
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32
Q

What are the 2 classes of synapse

A
  1. electrical

2. chemical

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33
Q

What is structure of electrical synapse

A
  • less abundant
  • separation is ~ 2nm
  • formed of proteins (connexons) which join adjacent membranes (++in myocytes of heart)
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34
Q

What are electrical synapses also known as

A

gap junctions

-as their separation is so small

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35
Q

What is functions of electrical synapse

A

allows the AP to propagate as if it were generated in the same cell

  • syncytium
  • unidirectional and bidirectional communication
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36
Q

what is a characteristic of electrical synapses

A
  • low resistance
  • extremely electrically labile (easily broken down or changed)
  • intimately linked to seizure and epilepsies
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37
Q

What is the separation between chemical synapse cell

A

~1 um (~500 times further apart than gap junctions)

38
Q

What are the presynaptic axon terminals of chemical synapses

A

the sender

-it creates vesicles which release neurotransmitters

39
Q

What are the postsynaptic terminals of chemical synapses

A

the receiver

-they have the receptors specific to a given neurotransmitter

40
Q

What happens in chemical synapse cells

A

the synaptic cleft prevents the AP from directly coupling w/ the postsynaptic cell
-next cell is activated by neurotransmitters

41
Q

Where are neurotransmitters in the chemical synapse

A

they are floating

42
Q

where are the neurotransmitters released from in chemical synapse

A

postsynaptic proteins

43
Q

what process do neurotransmitters go through in chemical synapse

A

presynaptic RE-UPTAKE

-recycling process

44
Q

what do SSRI antidepressants do

A

block the chemical synapse presynaptic re-uptake

45
Q

What are neurotransmitters

A

they are chemicals which are created within the brain in order to modulate and activate chemical synapses

46
Q

What are 2 main functions of neurotransmitters

A
  1. inhibition

2. Excitation

47
Q

What do excitatory neurotransmitters produce

A

excitatory postsynaptic potentials (EPSPs)

48
Q

What do EPSPs do

A
  • opens sodium channels that also let Calcium enter
  • Ex: glutamate, dopamine, epinephrine
  • Brings membrane potential closer to threshold
49
Q

What do inhibitory neurotransmitters produce

A

inhibitory postsynaptic potentials (IPSPs)

50
Q

What do IPSPs do

A
  • opens channels which allow potassium to exit OR chloride to enter
  • EX: GABA, acetylcholine
  • Brings membrane potential farther from threshold
51
Q

Neurotransmitters are classified according to?

A

their structure/ from where they originated

52
Q

what are the 6 classifications of neurotransmitters

A
  1. biogenic amines
  2. amino acids (glutamate, glycerin)
  3. Neuropeptides (endorphins, oxytocin)
  4. Purines (adenosine)
  5. Gases and lipids (nitric oxide, endocannabinoids)
  6. Other (acetylcholine)
53
Q

What are 2 subcategories of Biogenic amines

A
  • catecholamines (dopamine, noradrenalin)

- indolamines (serotonin, histamine)

54
Q

What is action of neurotransmitter that involves secondary messengers

A

the neurotransmitter will bind to the receptor that starts the internal mechanisms for a response to the stimulus that can lead (or not) to , a postsynaptic action potential

55
Q

What is the simpler action of neurotransmitters

A

Certain channels open with the binding of neurotransmitter to receptors

56
Q

how many cranial nerves serve to bring peripheral info to the CNS

A

12

-numbered in roman numerals

57
Q

What does the # of cranial nerve reflect

A

the position of the nerve along the ventral surface of the brain

58
Q

what kind of function can the cranial nerves have

A
  • sensory
  • motor
  • sensorimotor
59
Q

how to they become integrated at the level of the brain

A

interface with specific nuclei

60
Q

Olfactory nerve : # , function and nucleus

A

I.

  • sensory: smell
  • motor: none
  • nucleus: olfactory bulb
61
Q

Optic nerve: # , function and nucleus

A

II.

  • sensory: vision
  • motor: none
  • nucleus: lateral geniculate, superior colliculus
62
Q

Occulomotor nerve: # , function and nucleus

A

III.

  • sensory func: none
  • motor: eye movement, pupil constriction
  • nucleu: oculomotor nucleus, Edinger-Westphal nucleus
63
Q

Trochlear: # , function and nucleus

A

IV.

  • sensory f.: none
  • motor f.: eye movements
    nucleus: trochlear nucleus
64
Q

Trigeminal: # , function and nucleus, 3 divisions

A

V.

  • sensory f.: sensations frm the skin of face, nose, mouth
  • 3 divisions: ophthalmic (eyes and nose), maxillary (upper lip), mandibular (lower jaw, largest, dentists favorite)
  • motor f.: chewing & swallowing
  • nucleus: spinal & sensory Trigeminal nuclei, mesencephalic nucleus
65
Q

Abducens: # , function and nucleus

A

VI.
-sensoryf.: none
Motor f.: eye movements
-nucleus: abducens nucleus

66
Q

Facial: # , function and nucleus

A

VII.

  • sensory f.: taste frm anterior 2/3 of mouth
  • motor f.: facial expressions, crying, salivation
  • nucleus: spinal trigeminal, nucleus of the solitary tract, superior salivatory nucleus, facial motor nucleus
67
Q

Auditory (vestibulocochlear): # , function and nucleus

A

VIII.

  • sensory f.: hearing, balance
  • motor f: none
  • nucleus: cochlear and vestibular nuclei
68
Q

Glossopharyngeal: # , function and nucleus

A

IX.

  • sensory f.: taste frm posterior tongue and throat
  • motor f.: swallowing, salivation
  • nucleus: spinal trigeminal nucleus, nucleus of the solitary tract, inferior salivatory nucleus, nucleus ambiguous
69
Q

Vagus: # , function and nucleus

A

X.

  • sensory f.: taste sensation frm neck and abdo
  • motor f.: swallowing, control of larynx, parasympathetic nerves to heart and viscera
  • nucleus: spinal trigeminal nucleus, nucleus of the solitary tract, dorsal motor nucleus, nucleus ambiguous
70
Q

Spinal Accessory

A

XI.

  • sensory f.: none
  • Motor f.: movement of shoulders and head
  • nucleus: accessory nucleus
71
Q

Hypoglossal

A

XII.

  • sensory f.: none
  • motor f.: movement of the tongue
  • nucleus: hypoglossal nucleus
72
Q

Structure of meninges

A
  • consists of 3 diff. CT membranes

- they differ according to thickness & toughness of the T

73
Q

What are the 3 membranes of meninges (from skull to brain)

A
  1. DURA MATER
  2. ARACHANOID MATER
  3. PIA MATER
74
Q

What is the function of meninges

A
  • protection

- separation of tissues

75
Q

What is structure of the DURA MATER

A
  • least malleable, most rigid
  • has 2 layers that are fused across the brain except at the DURAL SINUSES (where venous blood collects and is sent into internal jugular)
76
Q

What are the 2 layers of the DURA MATER

A
  1. External / Periosteal layer:
    - attaches to the interior of the cranium bone
  2. Internal/ Menigeal layer:
    - external layer of the CNS
77
Q

Where do certain extensions of the dura mater introduce themselves

A

-btw the hemispheres or other separations of the brain parts
(falx cerebri, falx cerebelli, tentorium cerebelli)

78
Q

What is the function of dura mater

A
  • fixes brain to the cranium
    -limits movement of the brain
    NOTE:
    The dura mater can actually
    cause damage to the underlying
    cortex when the brain sustains
    an injury
79
Q

What is structure of arachnoid mater

A

-flexible envelope
-Separated from dura mater by the subdural space and from the pia mater by the subarachnoid space
Filled with CSF
-attached to the pia mater by filamentous extensions

80
Q

What allows the passage of the venous blood of the Dural sinuses

A

The arachnoid villi cross the dura mater & penetrate in the Dural sinuses located in the superior portion of the cranial cavity

81
Q

What is the PIA Mater: structure/ function

A
  • vascularized
  • firmly adheres to CNS (follows each convolution of the brain)
  • location of meningiomas
82
Q

Where is CSF generated and flows through

A

within the ventricles

-open spaces within the brain

83
Q

How many ventricles are there in the brain

A

4

  • 2 lateral (w/ several landmark divisions like the horns)
  • 3rd and 4th ventricles
84
Q

How do ventricles communicate w/ each other

A

through specialized passageways called :

  • interventricullar foramen (of Monroe)
  • Cerebral Aqueduct (of Sylvius)
85
Q

What lines the ventricles

A

ependymal cells

-give rise to CSF

86
Q

What is function of CSF

A
  • ensures that the CNS float

- provides nutrients and recycles debris frm the CNS

87
Q

What produces CSF

A

Produced by the choroid plexus that are a cluster of porous capillaries surrounded by a layer of ependymal cells linked by tight junctions & bearing numerous microvilli

88
Q

Structure and function of choroid plexus

A

There is a plexus on the roof of every ventricle
Blood filtrate passes with ease through the endothelium of the capillaries because of the large fenestration
The ependymal cells monitor substances that pass in the CSF because they have pumps controlling ions

89
Q

How much CSF is produced per day

A

1 Liter/ day

capacity: 150ml
renewal: every 3-4 hrs

90
Q

circulation of CSF

A
  1. lateral ventricles
  2. interventricular foramen (of monroe)
  3. 3rd ventricle
  4. cerebral aqueduct (of sylvius)
  5. 4th ventricle
  6. median & lateral aperture
  7. central canal
  8. subarachnoid space
  9. dumps into dural venous sinuses and lymphatic vessels

A & P 2 (13 decks)

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