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Anatomy and Physiology 1 > 2. The Nervous System > Flashcards

2. The Nervous System Flashcards

1
Q

Membrane potential

A

Electrical potentials exist across the membranes of virtually all cells (the voltage diff inside vs out)

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2
Q

ICF and ECF charge at resting MP

A

resting MP is negative
- ICF is more negative than ECF
- it doesnt mean theres a positive side, they’re both negative

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3
Q

Action potential

A

excitable cells (nerve and muscle) can generate rapidly changing electrochemical impulses at their membranes

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4
Q

What is action potential used for

A
  • transmit messages
  • used by fertilized eggs and hormone-secreting cells
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5
Q

What does a potential difference require

A
  1. concentration gradient for an ion
  2. a membrane which is permeable to that ion
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6
Q

Explain

A

The concentration gradient moves out, but because of the electrical gradient, some move back n so the concentration = electrical and has equal potential

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7
Q

Membrane potential. how does it work

A
  1. an ion wants to move out because of concentration gradient
  2. this causes a region of electronegativity inside the membrane and electropositive outside the membrane
  3. electrical gradient creates an electrical force and draws the positive charges back into the cell
  4. since theres more ions leaving, the stronger the force and eventually equals the concentration
  5. net movement is equal
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8
Q

Equilibrium potential and formula

A

the potential difference at this equilibrium
- E (ion) = V (membrane potential)

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9
Q

Another name for equilibrium potential and why

A

reversal potential
- direction of ion movement changes when voltage difference exceeds this level

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10
Q

What happens to K+ movement when the membrane potential reaches -60mV and becomes more negative?

A

At -60mV, K+ movement is balanced between leaving the cell (due to concentration gradient) and being pulled back in (due to electrical gradient). If the membrane potential becomes more negative, K+ will move back into the cell, against its concentration gradient.

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11
Q

How does the membrane potential fluctuation affect the cell/cytoplasm

A

Actual number of ions moving is very small and they stay close to the membrane so it doesn’t affect it

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12
Q

Nernst potential

A
  • diffusion potential across a membrane that exactly opposes the net diffusion of a particular ion
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13
Q

How is nernst potential determined

A

ratio of the concentration of that specific ion on the two sides of the membrane

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14
Q

The greater the ratio for nernst potential

A

the greater the tendency for the ion to diffuse in one direction and the greater the NP required to prevent additional net diffusion

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15
Q

Nernst equation and explain what each mean

A

E(V) = RT/zF ln[x]out/[x]in
- E = equilibrium potential for each ion
- R = gas constant
- T - temp in K
- z - ion valence
- F - constant
- X - concentration of ions

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16
Q

What is the electrical potential in the nernst equation

A

membrane potential when ion x is as its electrochemical equilibrium

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17
Q

how does nernst equation relate to ion diffusion and what is EMF in milivolts

A

EMF (in mV) = +61 × log([in]/[out]) for a univalent ion.

Positive EMF if a negative ion is moving from inside to outside.
Negative EMF if a positive ion is moving from inside to outside.

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18
Q

What is the Goldman Equation and what factors does it consider?

A

The Goldman Equation calculates the membrane potential considering multiple ions. It takes into account:

The concentration of each ion inside (Ci) and outside (Co) the cell.
The permeability of the membrane to each ion (Pion).
The polarity of the ion’s charge.

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19
Q

What maintains the resting membrane potential of a nerve cell and whats the number

A

-90mV
- The Na+-K+ pump moves 3 Na+ out for every 2 K+ in, creating a negative potential inside the cell.
- This also creates a large concentration gradient.
- Leaky channels are 100 times more permeable to K+ than Na+, contributing to the resting membrane potential.

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20
Q

What is the pump useful for in resting membrane potential

A
  • compensates for leakage and maintains gradients and membrane potential
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21
Q
A
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22
Q

Explain this pic

A
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23
Q

How do the charges sent signals in nerve action potential

A
  • rapid changes in the membrane potential that spread rapidly along the nerve fiber
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24
Q

Stages of nerve action potential

A
  1. resting
  2. depolarization
  3. repolarization
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25
Q

What is the resting stage of a nerve action potential?

A

The membrane is polarized at -90mV.
The cell is stable, with the inside more negative compared to the outside.

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26
Q

What happens during the depolarization stage of a nerve action potential?

A

The membrane suddenly becomes highly permeable to Na+.
Na+ ions rapidly diffuse into the axon, making the inside of the cell more positive.

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27
Q

What occurs during the repolarization stage of a nerve action potential?

A

Na+ ion channels close.
K+ ion channels open more than normal.
K+ diffuses out of the cell, reestablishing the negative membrane potential

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28
Q

What are the two voltage gates of a Na+ channel and their functions?

A

Activation gate: Located outside; closed at resting (-90mV), opens to increase Na+ permeability as potential changes.
Inactivation gate: Located inside; remains open during activation but closes with a delay during repolarization.

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29
Q

How does the Na+ channel function during different membrane potentials?

A
  1. Resting (-90mV): Activation gate is closed, Na+ cannot enter.
  2. Activation (from -70 to -50mV): Activation gate opens, increasing Na+ permeability 500-5000 fold.
  3. Inactivation (+35 to -90mV): Inactivation gate closes, Na+ entry is blocked, and the cell repolarizes.
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30
Q

What happens to the Na+ channel during inactivation and how does it affect Na+ flow?

A

Inactivation gates close: This process is slower than activation gate opening, so Na+ flows in for a brief period (about 1/10,000th of a second).
Reopening: Inactivation gates will not reopen until the membrane potential returns to its original resting value (-90mV).

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31
Q

What happens to K+ channels during an action potential?

A
  1. Resting: K+ channels are closed.
  2. Conformation changes: They open with a delay as the membrane potential (MP) goes from -90mV toward zero, just as Na+ channels begin to close.
  3. Effect: Decreased Na+ entry and increased K+ exit speed up the repolarization process.
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32
Q

What factors can initiate an action potential?

A

Mechanical: For example, sensory neurons in the skin.
Chemical: Neurotransmitters transmit signals between neurons.
Electricity: Involves electrical signals between muscle cells in the heart and intestine.

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33
Q

How do sodium ions play a role in initiating an action potential

A

Any factor causing sodium ions (Na+) to diffuse inward through the membrane in sufficient quantities starts a positive feedback cycle of opening Na+ channels.

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34
Q

What is the threshold for excitation

A

65 millivolts

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35
Q
A
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36
Q

How does an action potential propagate along the membrane?

A

Propagation: An action potential at one site causes it to spread along the membrane, known as the nerve impulse.
Direction: It propagates in all directions from the stimulus until the entire membrane is depolarized.
All-or-Nothing: The action potential either fully occurs or does not occur at all.

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37
Q

What is the absolute refractory period and why does it occur?

A

Definition: It is the period during which a second action potential cannot be elicited, even by a strong stimulus.
Reason: Sodium channels are inactivated and can only reopen when the membrane potential (MP) is near its resting value.
Duration: In large myelinated fibers, it lasts about 1/2500 of a second.

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38
Q

How are sodium and potassium ionic gradients re-established after an action potential?

A

Method: Achieved by the sodium-potassium pump.
Energy: Uses ATP.
Activity: Pumping activity increases to the third power of intracellular sodium concentration. For example, doubling the sodium concentration results in an eight-fold increase in pump activity.
- Ex) 2 -> 2^3 = 8

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39
Q

What are the benefits of myelination in nerve fibers?

A

Saltatory Conductance: Ions flow through the membrane only at nodes of Ranvier.
Increased Velocity: Conductance velocity increases 5 to 50 fold.
Energy Efficiency: Reduces the energy required to re-establish sodium and potassium concentrations.
Ion Transfer: Allows repolarization to occur with minimal ion transfer.

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40
Q
A
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41
Q

What are the speeds of nerve impulses in small unmyelinated fibers versus very large myelinated fibers?

A

Small Unmyelinated Fibers: As slow as 0.25 m/s.
Very Large Myelinated Fibers: Up to 120 m/s (270 miles per hour).

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42
Q

how are action potentials triggered

A

net grade potential at the axon hillock

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43
Q
A
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44
Q
A
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45
Q

what is it called if something passes the threshold potential

A

trigger zone

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46
Q
A
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47
Q

conductance

A

measures the movement of charge across the membrane

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48
Q

permeability

A

measures the capability of ions to flow across the membrane, regardless of whether they are moving across the membrane

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49
Q

CNS includes

A

brain and spinal cord

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50
Q

PNS includes

A

cranial nerves and spinal nerves going to somatic structures
- autonomic nervous system - going to visceral structures

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51
Q

sensory neurons include

A
  • afferent neurons
  • transmits sensory information from the receptors of the entire body to the CNS
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52
Q

motor neurons include

A
  • efferent neurons
  • control various body functions
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53
Q

association neurons function

A

connecting interneurons
- carry information from afferent to efferent neurons
- 90% of all neurons
- integrative function

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54
Q
A
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55
Q

CNS location and function

A
  • located in the bony casing of the cranium and vertebrae
  • receives info, decides what to do with it, gives orders fro muscles and glands to act
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56
Q

PNS location and function

A
  • connects periphery with the brain and spinal cord
  • innervate muscle, skin and glands
  • brings messages in and out of the CNS system
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57
Q
A

the enteric subdivision lies in the walls of the GIT and is influenced by both the sympathetic and parasympathetic subdivisions but can function independently as well

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58
Q

somatic nervous system function

A

associated with voluntary control of muscles

59
Q

autonomic nervous system function

A

involuntary functions such as control of smooth muscle, cardiac muscle and glands

60
Q

autonomic nervous system divisions and location

A
  1. parasympathetic - cell bodies in select regions of the brain and in sacral levels of the spinal cord
  2. sympathetic - cell bodies located in the thoracic and lumbar regions of the spinal cord
  3. enteric - lies in the wall of GI tract
61
Q

Neurons involved in the somatic division

A

EFFERENT (motor) neurons innervate muscles

62
Q

Neurons involved in the autonomic division

A

SA and PSA neurons
- enteric: SA and PSA neurons

63
Q

PSA neurons

A
  • parasympathetic neurons
  • cell bodies in select regions of brain and sacral levels of spinal cord
  • first role: normal maintenance of internal environment
  • rest and digest
  • single structure important at the time
64
Q

SA neurons

A
  • sympathetic neurons
  • cell bodies in thoracic and lumbar regions of spinal cord
  • first role: response to impingements by external environment
  • act during stress and strain
  • many structures simultaneously
65
Q

Organs involving sym and parasym input

A

salivary glands, heart, bladder, sex organs

66
Q

Organs involving sym input only

A

sweat glands, most blood vessels, piloerector muscles of skin

67
Q

neurons

A

nerve cells

68
Q

afferent processes vs afferent process

A

afferent processes - dendrites
afferent process- axon

69
Q

nuclei

A

groups of nerve cell bodies within CNS

70
Q

ganglia

A

groups of nerve cell bodies outside the CNS

71
Q

tracts or fasciculi

A

bundles of nerve processes within the CNS

72
Q

nerves

A

bundles of processes outside the CNS

73
Q

Glia

A

non-neuronal cells that don’t produce impulses, just support and protection

74
Q

Glia function in detail

A
  • involved in K+ and Ca++ buffering
  • neurotransmitter reuptake
  • pathways for neuronal migration during development
  • axonal guidance during regeneration
  • release cytokines in disease
  • keeps bad stuff out of the brain (blood-brain barrier)
  • CSF production
75
Q

Types of glia

A
  1. macrogilia
  2. microglia
  3. ependyma
76
Q

Macroglia

A
  1. astrocytes - whtie and grey matter of brain and spinal cord. cover about 85% of the basal lamina of all blood vessels in CNS, blood-brain barrier
  2. Oligodendroglia - white and grey matter of CNS, involved in myelin sheath formation
77
Q

microglia

A
  • resident macrophages in the CNS
78
Q

ependyma

A
  • epithelium lining the ventricles of the brain and the central canal of the spinal cord
  • unite the pia mater and capilaries to form the choroid plexus (important in CSF production)
  • selective barrier between brain and csf compartments
79
Q
A
80
Q

dendrites

A

receive info from other neurons
- conduct nerve impulses towards the cell bodies

81
Q

cell body

A
  • consist of a nucleus, er, ribosome, golgi app and mitochondria
82
Q

axons

A
  • major route by which one nerve cell sends signal to other neurons
  • conduct nerve impulses away from cell body
83
Q

boutons

A
  • terminal or synaptic
  • distal end of axon
  • swellings that contain neurotransmitter filled vesicles that form chemical synapses with other neurons
84
Q

en passant boutons

A
  • found along the length of the axon
85
Q

how do neurons communicate

A

release of a neurotransmitter from a presynaptic neuron that binds to receptors on the postsynaptic neuron - causes a change in membrane potential

86
Q

number of neuron names

A
  1. pseudounipolar neuron
  2. bipolar neurons
  3. multipolar neurons
87
Q

pseudounipolar neurons

A
  • single process extends from cell body and divides into central and peripheral branches - dorsal root ganglia
88
Q

bipolar neurons

A

single axon and single dendrite extending from the cell body
- retina and olfactory systemm

89
Q

multipolar neurons

A
  • axon and several dendrites - most neurons in the cns
90
Q

types of synapses

A
  1. axo-dendritic - on dendrites
  2. axo-somatic - on cell body
  3. axo-axonic - on the initial segment of the axon or on the synaptic boutons
  4. dendro-dendritic
  5. neuromuscular junction - on muscles or other organs
91
Q

Types of synapses in the nervous system

A
  1. chemical
  2. electrical
92
Q

chemical synapses

A
  • most types are this one
    -one way conductance
  • from the presynaptic neuron (secretes to transmitter) to the post synaptic neuron (the transmitter acts in)
93
Q

electrical synapses

A

in muscle
- viseral smooth and cardiac and a few in CNS

94
Q

presynaptic terminals/ boutons - location

A
  • knobs that lie on the surface of the dendrites and some on cell body
  • are the ends of nerve fibrils that originate from many other neurons
95
Q

presynaptic terminals/ boutons - secretion

A
  • secrete either an excitatory or inhibitory transmitter substance
96
Q

presynaptic terminals/ boutons - contain

A
  1. transmitter vesicles: store and release the transmitter substance
    - action potential causes a small number of vesicles to release their transmitter into the synaptic cleft
  2. mitochondria: provides energy (ATP) for synthesizing transmitter
97
Q

presynaptic terminals - contain

A
  • contain large numbers of voltage gates calcium
98
Q

presynaptic terminal - calcium

A

depolarization causes large influx of calcium into the terminal
- amount of transmitter released is proportional to the amount of calcium that enters
- calcium binds with release sites causing them to open and release transmitter from vesicles

99
Q

release sites are found where

A

special proteins on the interior surface of the presynaptic membrane

100
Q

synaptic cleft

A
  • seperate the presynaptic terminal from the postsynaptic neural soma
101
Q

small molecules but fast acting transmitters

A
  1. class 1 - acetylcholine
  2. class 2 amines - norepinephrine, epinephrine, dopamine, serotonin, histamine
  3. class 3 amino acids - GABA, glycine, glutamate, aspartate
  4. class 4 - nitric oxide (NO)
102
Q

slow acting transmitters/growth factors

A
  1. hypothalamic-releasing hormones
  2. pituitary peptides
  3. peptides that act on gut and brain
  4. other tissues
103
Q

What is the structure of receptor proteins involved in neurotransmitter action on the postsynaptic neuron?

A
  1. Binding component – protrudes outward into the synaptic cleft.
  2. Ionophore component – passes through the membrane into the interior of the postsynaptic neuron.
104
Q

What are the two types of ionophore components in receptor proteins?

A
  1. Ion channel – alters the passage of specific ions.
  2. Second messenger activator – a molecule that protrudes into the cell cytoplasm and activates one or more substances.
105
Q

What are cation channels, and what ions do they allow to pass?

A

Most often allow Na+ ions to pass when open.
Can also allow K+ and/or Ca2+ ions to pass.
Lined with negative charges, attracting positively charged sodium ions when the channel diameter increases.
Repel chloride and other anions.

106
Q

What is the effect of excitatory transmitters on cation channels?

A

Excitatory transmitters open cation channels, allowing the positive charge of Na+ ions to enter, which excites the neuron.

107
Q

What happens when anion channels open?

A

When the anion channel diameter increases, Cl- ions pass into the channel and to the opposite side.

108
Q

What is the effect of inhibitory transmitters on anion channels?

A

Inhibitory transmitters open anion channels, allowing Cl- ions (negative charges) to enter, which inhibits the neuron.

109
Q

Why is the second messenger system important for prolonged activation?

A

The second messenger system is used for processes requiring prolonged changes in neurons, such as memory, which can take months to form, unlike the millisecond activation of ion channels.

110
Q

What is an example of a second messenger in neurons?

A

An example of a second messenger is the G protein, which is attached to the part of the receptor that protrudes into the cell.

111
Q

What happens when the G protein is activated?

A

When activated, the alpha portion of the G protein releases and moves freely within the cell, while the beta and gamma portions remain attached to the cell membrane.

112
Q

What can the alpha portion of the G protein do once activated?

A
  1. Open specific ion channels through the postsynaptic membrane, keeping them open for a prolonged time.
  2. Activate cAMP or cGMP in the neuron, which can activate specific metabolic machinery.
  3. Activate intracellular enzymes.
  4. Activate gene transcription.
113
Q
A
114
Q

What is the resting membrane potential of the soma of a spinal motor neuron?

A

The resting membrane potential of the soma of a spinal motor neuron is -65 mV,

115
Q

How does a change in membrane voltage affect the excitability of the neuron?

A

Decreasing the voltage to a less negative value makes the membrane more excitable.
Increasing the voltage to a more negative value makes the membrane less excitable.

116
Q

What role does the sodium-potassium pump play in the resting membrane potential of a spinal motor neuron?

A

The sodium-potassium pump in the soma of spinal motor neurons is strong, helping maintain the resting membrane potential by actively pumping Na+ out and K+ into the cell.

117
Q

How does chloride movement affect the resting membrane potential in spinal motor neurons?

A

The membrane is permeable to chloride, which moves out of the cell due to the negative charge inside. There is also a weak chloride pump that contributes to this movement.

118
Q

Find the nersnt potential for each ion

A
119
Q

When is the Nernst potential positive or negative?

A

Positive (+ve) when a negative ion diffuses from inside to outside, or a positive ion diffuses from outside to inside.
Negative (-ve) when a positive ion diffuses from inside to outside, or a negative ion diffuses from outside to inside.

120
Q

What are the conductive properties of the soma’s intracellular fluid?

A

The intracellular fluid of the soma is highly conductive, allowing electrical signals to travel easily within the neuron.

121
Q

What is the significance of the large diameter of the soma in spinal motor neurons?

A

The soma has a large diameter (10-80 μm), which provides very little resistance to electrical conduction within the soma.

122
Q

How do changes in one part of the soma affect other parts?

A

Any change in one part of the soma is almost exactly equal in all other parts due to its high conductivity.

123
Q

What is “summation” in the context of the soma?

A

Summation refers to the process by which signals from multiple sources can combine and influence the overall electrical activity of the soma.

124
Q

What effect does an excitatory transmitter have on the postsynaptic somal membrane?

A

An excitatory transmitter increases the membrane permeability to sodium in the postsynaptic somal membrane.

125
Q

What happens during the rapid influx of sodium in an excited neuron?

A

The rapid influx of sodium (a positive ion) into the cell increases the internal positive charge, contributing to the neuron’s excitation.

126
Q

What is an excitatory postsynaptic potential (EPSP)?

A

An EPSP is a positive increase in the voltage above the normal resting membrane potential, making the neuron more likely to fire.

127
Q

What was the resting membrane potential of the neuron, and what is it now in the excited state?

A

Resting membrane potential: -65 mV
Excited state potential: -45 mV

128
Q

How is the excitatory postsynaptic potential (EPSP) calculated in this case?

A

In this case, the EPSP is +20 mV, which is the difference between the resting membrane potential (-65 mV) and the excited state potential (-45 mV).

129
Q

What is required to reach the threshold for neuron excitation?

A

To reach the threshold for excitation, many presynaptic terminals must discharge simultaneously, a process known as summation.

130
Q

What happens when the EPSP rises high enough?

A

When the EPSP rises high enough, it initiates an action potential (AP) in the neuron.

131
Q

Where does the action potential (AP) begin, and why is it easier to generate there?

A

The AP begins in the initial segment of the axon, which has a seven times greater concentration of voltage-gated sodium channels compared to the soma. This higher concentration makes it easier to generate the AP.

132
Q

How does the action potential (AP) travel and what effect does it have on the soma and dendrites?

A

The AP travels in both directions along the axon, but the soma and dendrites have fewer sodium channels. As a result, the AP has little effect on these regions.

133
Q

What is an inhibitory postsynaptic potential (IPSP)?

A

An IPSP is an increase in negativity beyond the normal resting potential, resulting in hyperpolarization of the neuron.

134
Q

What types of channels are mainly opened during an IPSP?

A

During an IPSP, chloride channels and potassium channels are mainly opened.

135
Q

Can EPSP and IPSP occur simultaneously?

A

yes, EPSP and IPSP can occur simultaneously. Enough IPSP from one source can nullify the EPSP from another source.

136
Q

What is meant by the facilitation of neurons?

A

Facilitation of neurons refers to a state where large groups of neurons are near threshold but not quite firing, making them ready to respond quickly to arriving signals.

137
Q

What is presynaptic inhibition?

A

Presynaptic inhibition occurs before the signal reaches the synapse, involving the release of an inhibitory substance onto the outside of the presynaptic nerve fibrils before they terminate.

138
Q

What substance is commonly involved in presynaptic inhibition and what is its effect?

A

The substance commonly involved in presynaptic inhibition is GABA (gamma-aminobutyric acid). It opens anion channels, allowing large numbers of chloride ions to enter the terminal fibrils.

139
Q

How does the entry of chloride ions affect presynaptic nerve fibrils?

A

The entry of chloride ions makes the presynaptic nerve fibrils more negative, which inhibits synaptic transmission.

140
Q

Where does presynaptic inhibition commonly occur and what is its function?

A

Presynaptic inhibition occurs in many sensory pathways. It helps minimize sidewise spread and mixing of signals in sensory tracts.

141
Q

What is spatial summation in neurons?

A

multiple presynaptic terminals release neurotransmitters simultaneously at different locations on the postsynaptic neuron, combining their effects to influence the overall membrane potential and potentially initiate an action potential.

142
Q

What is temporal summation in neurons?

A

Temporal summation occurs when successive discharges from a single presynaptic terminal happen rapidly enough. These successive signals can summate to reach the firing threshold and initiate an action potential (AP).

143
Q
A

Anatomy and Physiology 1 (2 decks)

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