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MCAT Bio > Bio #4 > Flashcards

Bio #4 Flashcards

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1
Q

dendrites

A

located on the body of the neuron and where they receive information

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2
Q

neural crest cells go to ______ while neural stems cells (eventually neuroblasts) go to _____

A

PNS

CNS

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3
Q

neurons have a ____ outside and ____ inside

A

more positive

less positive

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4
Q

___ Na+ pumped out while ____ K+ pumped in

A

3

2

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5
Q

ionotropic

A

ion gated neurotransmitter receptors

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6
Q

ionotropic

A

gated ion channels: neurotransmitter receptors

depolarization or hyperpolarization depends on what ion is let in.

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7
Q

metabotropic

A

second messanger systems

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8
Q

afferent neurons carry info to the spinal cord from the ______ and efferent carry info from the ____

A

back

front

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9
Q

neuromuscular junction

A

synapse between motor cells and lower motor neurons

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10
Q

neurons have _____ communication within and _____ communication between

A

electrical

chemical

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11
Q

the nervous system is responsible for

A

control of muscular movement, neuromuscular reflexes, glandular secretions, and higher-level thinking.

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12
Q

the nervous system is responsible for

A

control of muscular movement, neuromuscular reflexes, glandular secretions, and higher-level thinking.

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13
Q

neurons

A

specialized cells capable of transmitting electrical impulses and then translating those electrical impulses into chemical signals.
o Each neuron has a shape that matches its function

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14
Q

nucleus

A

is located in the cell body (soma)

• Soma also houses ER and ribosomes

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15
Q

dendrites

A

appendages emanating from the soma, receive incoming messages from other cells.

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16
Q

axon hillock

A

integrates the incoming signals.
• Plays an important role in action potentials: the transmission of electrical impulses down the axon.

takes in info for both excitatory and inhibitory signals

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17
Q

action potential

A

the transmission of electrical impulses down the axon.

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18
Q

axon

A

a long appendage that terminates in close proximity to a target structure (a muscle, gland, or another neuron)

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19
Q

myelin

A

insulate nerve fibers, composed of a fatty membrane, prevent signal loss or crossing of signals.
• Myelin sheath: maintains the electrical signal within one neuron.
• Also increases speed of conduction
• Produced by:
o Oligodendrocytes in the Central NS
o Schwann cells in the peripheral NS
• Nodes of Ranvier: small breaks in the myelin sheath.
o Important for rapid signal transduction.

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20
Q

Axons carry signal ____ from the soma, dendrites carry signals ____ the soma.

A

away

toward

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21
Q

myelin sheath

A

maintains the electrical signal within one neuron.

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22
Q

oligodendrocytes

A

produce myelin sheath in CNS

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23
Q

schwann cells

A

produce myelin sheath in PNS

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24
Q

nodes of ranvier

A

small breaks in the myelin sheath.

o Important for rapid signal transduction.

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25
Q

nerve terminal

A

end of the axon. Enlarged and flattened to maximize transmission. Synonymous to synaptic bouton.

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26
Q

synaptic bouton

A

end of the axon. Enlarged and flattened to maximize transmission. Synonymous to nerve terminal.

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27
Q

neurotransmitters

A

the chemicals that transmit information between neurons.

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28
Q

synaptic cleft

A

the space between the presynaptic and postsynaptic neurons.

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29
Q

synapse

A

term for the nerve terminal, synaptic cleft, and postsynaptic membrane all together

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30
Q

nerve

A

in the peripheral NS when multiple neurons have been bundled together.
• Sensory, motor, or mixed (sensory and motor)
o Info they carry
• Cell bodies of neurons of the same type are clustered together into ganglia.

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31
Q

tracts

A

CNS axons bundled together.

• Only carry one type of info (as compared to nerves that carry sensory, motor, or mixed info)

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32
Q

ganglia

A

• Cell bodies of neurons of the same type

The cell bodies of neurons in the same tract are grouped into nuclei

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33
Q

nuclei (neurons)

A

The cell bodies of neurons in the same tract are grouped into nuclei (CNS)

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34
Q

glial cells

A

cells that support neurons

astrocytes
ependymal cells
microglia
oligodendrocytes and schwann cells

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35
Q

Oligodendrocytes (CNS) and Schwann Cells (PNS)

A

produce myelin around axons

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36
Q

astrocytes

A

nourish neurons and form the blood-brain barrier which controls the transmission of solutes from the bloodstream into the nervous tissue.

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37
Q

ependymal cells

A

line the ventricles of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as a shock absorber.

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38
Q

microglia

A

phagocytic cells that ingest and break down waste products and pathogens in the CNS

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39
Q

action potential

A

all or nothing messages used by neurons to relay electrical impulses down the axon to the synaptic bouton.

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40
Q

action potential

A

all or nothing messages used by neurons to relay electrical impulses down the axon to the synaptic bouton.

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41
Q

resting membrane potential

A

the net electric potential difference that exists across the cell membrane, created by movement of charged molecules across that membrane. It is the balance, the net effect of both sodium and potassium’s equilibrium potentials.

 For neurons this is -70mV (balance of tug of war between K+ and Na+ with the inside being negative compared to the outside.
 Greater K+ concentration inside the cell.

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42
Q

the inside of a neuron normally is ______ potential

A

negative

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43
Q

normal Na+ concentration relative to neuron membrane

A

outside

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44
Q

normal K+ concentration relative to neuron membrane

A

inside

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45
Q

potassium leak channels

A

allow slow leak of K+ to outside of cell.

• As this occurs, it gives inside of cell slight negative charge.

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46
Q

Equilibrium potential of potassium

A

Eventually K+ moving out due to concentration gradient equals potassium being pulled back in by electrostatic attraction.
o No more net movement of K+

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47
Q

Na+/K+ ATPase

A

: continually pumps sodium and potassium back to where they started. K+ into the cell and Na+ out of the cell.
• Restore resting potential and Na+ and K+ gradients.

3 Na+ out for 2 K+ in

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48
Q

depolarization

A

raising the membrane potential, Vm, from resting potential, from excitatory input, makes the neuron more likely to fire an action potential.

raising the membrane potential means it is becoming more positive.

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49
Q

hyperpolarization

A

lowering the membrane potential, Vm, from resting potential, from inhibitor input, makes the neuron less likely to fire an action potential.

50
Q

threshold

A

value at which an action potential will be triggered (-55 to -40 mV), meet this via depolarization

51
Q

summation

A

the additive effect of multiple signals from many different presynaptic neurons.
• Temporal: multiple signals are integrated during a relatively short period of time
o Ex: a lot of small excitatory signals can bring a postsynaptic cell to threshold.
• Spatial: additive effects are based on the number and location of the incoming signals.
o Ex: location (where they fire, dendrites or soma) and how many determine the threshold.

52
Q

temporal summation

A

integration of signals close in time
multiple signals are integrated during a relatively short period of time
o Ex: a lot of small excitatory signals can bring a postsynaptic cell to threshold.

53
Q

spatial summation

A

integration of signals close in space
additive effects are based on the number and location of the incoming signals.
o Ex: location (where they fire, dendrites or soma) and how many determine the threshold.

54
Q

what are the steps of polarization that cause an action potential to fire

A

resting potential (-) ==> depolarization (+) ==> repolarization (-) ==> hyperpolarization (–) ==> resting potential (-)

55
Q

electrochemical gradient

A

promotes the migration of sodium into the cell.
• Na+ wants to go into the cell because there is a lower concentration of sodium there AND the interior of the cell is more negative.

56
Q

sodium channels are ______ at +35 mV and the cell must be brought back to near resting potential for them to be _____

A

inactivated

deinactivated

57
Q

what are the 3 states of the sodium channel?

A
  • Closed: before the cell reaches threshold and after inactivation has been reversed.
  • Open: from threshold to +35 mV
  • Inactive: from +35 mV to resting potential.
58
Q

positive potential in the cell causes _____

A

the voltage gated potassium channels to open

59
Q

repolarization

A

kick out the K+ cells after depolarization causes a + charge on inside.

60
Q

Kicking out K+ causes ______ which makes neuron resistant to further action potentials.

A

hyperpolarization

61
Q

absolute refractory period

A

no amount of stimulation can cause another action potential to occur

62
Q

relative refractory period

A

there must be greater than normal stimulation to cause an action potential because the membrane is starting from a potential that is more negative than the resting value.

63
Q

impulse propagation

A

: the movement of the action potential down the axon to initiate neurotransmitter release.
 As sodium rushes in at one location it will cause depolarization at that location, which causes sodium channels to open at distal locations.
• Wavelike pattern.
 Info can only flow in one direction (due to refractory period)
 The speed at which actional potentials move depends on the length and cross-sectional area of the axon.
• Increased length means greater resistance and slower conduction
• Greater cross-sectional area means faster propagation due to decreased resistance.

64
Q

info can only flow in _____ due to ______

A

one direction

refractory period

65
Q

the speed at which action potentials move depends on the ____ and _____ of the axon

A

length
cross-sectional area

  • Increased length means greater resistance and slower conduction
  • Greater cross-sectional area means faster propagation due to decreased resistance (more important than length)
66
Q

saltatory conduction

A

the axon membrane is only permeable to ion movement at the nodes of Ranvier so the signal hops from node to node.

67
Q

_____ is responsible for fusion of neurotransmitter vesicles with the nerve terminal membrane

A

calcium

calcium influx into the cell as a result of the action potential reaching the nerve terminal.

68
Q

______ signals to _____ by release of neurotransmitter..

A

Presynaptic neuron
postsynaptic neuron

If neuron signals to gland or muscle then the postsynaptic cell is called an effector

69
Q

process of neurotransmitter release

A

 When action potential reaches the nerve terminal, voltage gated calcium channels open and calcium flows into cell  membrane bound vesicles carrying neurotransmitters fuse with cell membrane and release
 Receptor is:
• Ligand-gated ion channel: postsynaptic cell is depolarized or hyperpolarized

70
Q

process of neurotransmitter release

A

 When action potential reaches the nerve terminal, voltage gated calcium channels open and calcium flows into cell  membrane bound vesicles carrying neurotransmitters fuse with cell membrane and release
 Receptor is:
• Ligand-gated ion channel: postsynaptic cell is depolarized or hyperpolarized

71
Q

what is the receptor on the postsynaptic neuron

A

 Receptor is:
• Ligand-gated ion channel: postsynaptic cell is depolarized or hyperpolarized
• GPCR: change in levels of cAMP or influx of calcium.

72
Q

how are neurotransmitters removed from the synaptic cleft

A

 1. Broken down by enzymatic reactions
• Ex: Acetylcholine (ACh): broken down by acetylcholinesterase
 2. Reuptake carriers: bring neurotransmitters back into the presynaptic neuron.
• Ex: serotonin (5-HT), dopamine (DA) and norepinephrine (NE)
 3. Diffuse out of cleft
• Ex: Nitric oxide (NO)

73
Q

sensory neurons

A

afferent neurons, transmit sensory information from sensory receptors to the spinal cord and brain.

74
Q

motor neurons

A

: efferent neurons, transmit motor information from the brain and spinal cord to muscles and glands.

75
Q

interneurons

A

found between other neurons and are the most numerous.

 Found in brain and spinal cord and linked to reflexive behavior.

76
Q

can responses can be generated by the spinal cord

A

yes, reflex

77
Q

supraspinal circuits

A

requires input from the brain or brainstem.

78
Q

central nervous system

A

brain and spinal cord

79
Q

brain

A

o White matter: axons in myelin sheaths. Lies deeper than grey matter.
o Grey matter: unmyelinated cell bodies and dendrites
o Brainstem is at the base of the brain

80
Q

in the brain is white or grey matter deeper?

A

white

81
Q

what are the regions of the spinal cord

A

cervical
thoracic
lumbar
sacral

82
Q

vertebral column

A

protects the spinal cord, transmits nerves at the space between the adjacent vertebrae.

83
Q

spinal cord white matter vs. grey matter

A

grey matter is deep inside

84
Q

dorsal root ganglia

A

contain cell bodies of sensory neurons ONLY.

85
Q

motor neurons exit the spinal cord ____

A

ventrally

86
Q

motor neurons exit the spinal cord ____

A

ventrally

87
Q

peripheral nervous system

A

nerve tissue and fibers outside the brain and spinal cord (all 31 pairs of spinal nerves and 10/12 pairs of cranial nerves, olfactory and optic nerves are CNS)

• Connects the CNS to the rest of the body

made up of somatic and autonomic NS

88
Q

Autonomic NS

A

regulates heartbeat, respiration, digestion, and glandular secretions.
o Automatic functions.

o Peripheral component has two components.
 1. Preganglionic neuron: first neuron (cell body in CNS, synapse at ganglion in the PNS)
 2. Postganglionic neuron: second neuron (synapse in target tissue)

89
Q

Somatic NS

A

sensory and motor neurons distributed throughout the skin, joints, and muscles.

o Peripheral component has a neuron go from the spinal cord to the muscle without synapsing

90
Q

sympathetic NS

A

activated by stress
 Fight or flight.
 Increase heart rate, relaxes the bronchii, decreases digestion.
 Preganglionic neurons: acetylcholine, Postganglionic neurons: norepinephrine.

91
Q

parasympathetic NS

A

main role is to conserve energy.
 Resting and sleeping states, decelerate heart rate and promote digestion.
 Acetylcholine is NT for both pre and postganglionic neurons.
 Vagus nerve (Cranial Nerve X) responsible for parasympathetic innervation of the thoracic and abdominal cavity.

92
Q

difference in peripheral component of somatic and autonomic NS?

A

somatic: one neuron to target tissue from CNS
autonomic: two neurons connected by a synapse before reaching target tissue

93
Q

what are the pre and post ganglionic neurotransmitters for the sympathetic NS

A

pre: acetylcholine
post: norepinephrine

94
Q

what are the pre and post ganglionic neurotransmitters for the parasympathetic NS

A

 Acetylcholine is NT for both pre and postganglionic neurons.

95
Q

reflex arc

A

: neural circuits that control reflexive behavior. Sensory info reaches spinal cord which sends it up to the brain but also sends efferent signal to react to the signal too. Reaction occurs and info gets to the brain.

96
Q

reflex: monosynaptic

A

a single synapse between the sensory neuron that receives the stimulus and the motor neuron that responds to it.

• Ex: Knee-jerk reflex: afferent sensory neuron to efferent motor neuron and then contraction of the quadriceps muscle which extends the leg.

97
Q

explain knee-jerk reflex

A

• Ex: Knee-jerk reflex: afferent sensory neuron to efferent motor neuron and then contraction of the quadriceps muscle which extends the leg.

98
Q

reflex: polysynaptic

A

there is at least one interneuron between the sensory and motor neurons.
• Ex: Withdrawal reflex: stepping on a nail, need the initial reflex (similar to monosynaptic) to get off the nail but also need stimulation of motor neuron that controls the quadriceps muscles in the opposite limb.
o Interneurons in the spinal cord provide the connections from the incoming sensory information to the motor neurons in the supporting limb.

99
Q

explain withdrawal reflex

A

Withdrawal reflex: stepping on a nail, need the initial reflex (similar to monosynaptic) to get off the nail but also need stimulation of motor neuron that controls the quadriceps muscles in the opposite limb.
o Interneurons in the spinal cord provide the connections from the incoming sensory information to the motor neurons in the supporting limb.

100
Q

mature red blood cells do not have _____

A

nuclei

101
Q

the nucleus in neurons is located in the ____, also known as the ____

A

cell body

soma

102
Q

the myelin sheath maintains the _____ within one neuron and it increases the ______ in the axon.

A

electrical signal

speed of conduction

103
Q

ganglia

A

cluster of cell bodies of neurons of the same type.

104
Q

what are the 3 types of nerves?

A

sensory, motor, mixed

105
Q

synonym for glial cells

A

neuroglia

106
Q

the _____ fires an action potential if the ______ signals are strong enough to reach the threshold

A

axon hillock

excitatory

107
Q

Potassium (___) has a greater concentration ____ the neuron

A

K+, inside

108
Q

the inside of the neuron is ______ compared to the outside

A

negative (-70 mV)

109
Q

Sodium (____) has a greater concentration ___ the neuron

A

outside

110
Q

what are the equilibrium potentials of sodium and potassium

A

potassium: -90 mV
sodium: 60mV

111
Q

temporal summation vs. spatial summation of signals

A

temporal: many signals coming in at same time
spatial: many signals coming from different places

112
Q

what event makes a neuron resistant to future action potentials?

A

hyperpolarization

113
Q

what are the two roles of the Na+/K+ pump after an action potential is generated?

A

restore the gradient of Na+ and K+ and the resting potential across the membrane.

114
Q

because of the refractory period after an action potential in a certain area of the axon, information can _______

A

only flow in one direction (toward the nerve terminal)

115
Q

signal travels the fastest when the axon is _____ and has a _____

A

shorter (less resistance)

larger cross-sectional area

116
Q

for similar neurons, increased intensity of an excitatory signal does not result in an ______ of the action potential but rather an________.

A

increased potential difference

increased frequency of firing

117
Q

what is an effector in terms of a synapse

A

an effector is the gland or muscle that a neuron signals to.

118
Q

how many spinal nerves are there in the PNS

A

31

119
Q

which cranial nerves are considered part of the CNS?

A

the olfactory and optic nerves.

120
Q

Are inhibitory signals transmitted to the nerve terminal?

A

No

121
Q

does the somatic division of the nervous system contain some reflex arcs?

A

yes

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