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MCAT biology > chapter 6 > Flashcards

chapter 6 Flashcards

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1
Q

During fetal development, the neural tube forms 3 main regions that give rise to the brain. From anterior to posterior, these regions are?

A
  • the prosencephalon (the forebrain)- behaviour and personality
  • the mesencephalon (midbrain)
  • the rhombencephalon (hindbrain)
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2
Q

the preganglionic neuron synapses at a peripheral nueron on the?

A
  • postganglionic neuron, which then synapses and acts on the target oragan
    • preganglionic neurons are long in the parasympathetic NS and synapse on the target organ
    • preganglionic neurons are short in the sympathetic NS and synapse on the sympathetic trunk
    • postganglionic sympathetic fibers are longer and extend out to their target organs
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3
Q

preganglionic fibers and postganglionic fibers of the parasympathetic system, as well as preganglionic fibers of the sympathetic system primarily rely on the neurotransmitter?

A
  • acetylcholine
    • podtganglionic sympathetic fibers rely on norepinepherine
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4
Q

the primary function of the NS is to carry out 2 parallel and interdependent tasks?

A
  1. processing sensory information from the environment
  2. initiating physiological changes in response to that sensory input
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5
Q

The planning of motor control is initiated in the?

A
  • premotor cortex, and executed by the primary motor cortex located in the frontal lobe on a structure called the precentral gyrus
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6
Q

the coordination of movement is heavily dependent on?

A
  • dopamine
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7
Q

the cell type that makes this rapid relay of signals possible is?

A
  • the neuron
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8
Q

what are glial cells?

A
  • Glia, also called glial cells or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses. They maintain homeostasis, form myelin in the peripheral nervous system, and provide support and protection for neurons.
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9
Q

astrocytes form the?

A
  • blood-brain barrier, a structure that links the neurons of the CNS to the blood supply
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10
Q

what is one of the notable functions of astrocytes?

A
  • constant, indulin-independent, active transport of glucose from the bloodstream, ensuring a constant supply of glucose for neurons
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11
Q

insulation is provided by what cells in the CNS and PNS?

A
  • oligodendrocytes in the CNS
  • Schwann cells in the PNS
    • chieved by wrapping the axon in myelin
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12
Q

insulating the axons of neurons serves 2 purposes which are?

A
  • preventing cross-talk between axons
  • massively speeding up signal transmission
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13
Q

the signal called an action potential then travels from one unmyelinated gap to the next rapidly “jumping” down the axon in a process called?

A
  • saltatory conduction
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14
Q

What cell is the first line of defense against invaders in the CNS?

A
  • microglia
    • function like macrophages but also remove waste and damaged cells, prune some neurons and can even eat away extracellular protein deposits
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15
Q

what are ependymal cells?

A
  • produce and circulate celebrospinal fluid in the CNS
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16
Q

what are satellite cells?

A
  • control the microenvironment around cell bodies in ganglia and the PNS
17
Q

what is the function of CSF

A
  • bathes and buffers all cells within the CNS which provides a more constant, stable environment, and physcially cushions the CNS
18
Q

what is the structure of a neuron?

A
19
Q

what is the synaptic cleft?

A
  • a very small gap between 2 neurons
20
Q

what is a graded potential?

A
  • A change in the electrical potential on the membrane of an excitable cell (e.g. a nerve cell) in response to a stimulus, and where the magnitude of change is proportional to the strength of the stimulus.
21
Q

what is the role of Na+/K+ ATPase (sodium potassium pump)

A
  • regulates the entry and exit of specific ions whcih results in a membrane potential
    • intracellular environment is more negative (rich in K+, poor in Na+, Cl- and Ca2+) and the extracellular environment is more positive (rich in Na+)
22
Q

what is the movement of action potential down a neuron?

A
  1. Neuron at rest- neuron at resting potential -70mV, more Na+ ions outside of neuron, More K+ ions inside of neuron
  2. initation of action potential- stimulus opens Na+ channel proteins and Na+ ions move into neurons and inside of neuron becomes more positive
  3. movement of action potential part 1- Na+ channels open ahead of AP, K+ channels open behind AP
  4. movement of action potential part 2- Na+ channels open ahead of AP, K+ channels open behind AP
23
Q

when does repolarization start?

A
  • when the voltage-gated potassium channels with a much higher threshold for activation open up, triggered by the positice membrane potential due to the recent, influx of sodium
  • at the same time, the voltage gated sodium channels are closing at about +35mV, after only being open for a short time being
  • K+ rushes out which makes the membrane potential negative again and hyperpolarization occurs
  • once the voltage-gated potassium channels close, Na+/K+ ATPase is sufficient to bring both the membrane potential and concentration gradient back to normal
24
Q

what is the absolute refractory period?

A
  • after the sodium channels close, when depolarization hits its peak around +40mV, they cannot open again for a certain period of time and this serves as a safety check by preventing a signal from traveling backwards
25
Q

what is the relative refractory period?

A
  • occurs when the sodium channels are able to open again, but the membrane remains hyperpolarized
    • called relative because it is possible but more difficult to generate another action potential at this time
26
Q

what is the role of voltage gated Ca2+ channels?

A
  • open in response to the change in membrane potential caused by arribing wave of depolarization, their opening results in an influx of Ca2+ which causes a chemical signaling cascade that ends with the exocytosis of neurotransmitters from vesicles where they can bind with ligand-gated ion channels on the dendrites of the next neuron starting the process all over
27
Q

what is degradation?

A
  • hydrolytic enzymes rapidly break the neurotranmitter apart, thereby preventing it from binding to receptors any further
    • ex. acetylcholinesterase whcih makes sure the effects of acetylcholine in the synpase is brief
28
Q

what is reuptake?

A
  • occurs when neurotransmitters are moved out of the synpatic cleft wither by presynpatic neurons or by astrocytes and may ne followed by breakdown
29
Q

what is the function of acetylcholine?

A
  • activates muscle contraction at the neuromuscular junction.
  • used in all autonomic outputs from the brain to autonomic ganglia
  • used in the parasympathetic NS for post-ganglionic connections
30
Q

what is the function of dopamine?

A
  • used in reward pathways and motor pathways
  • Parkinson’s disease
31
Q

what is the function of glycine?

A
  • inhibitory neurotransmitter of the spinal cord and brainstem
  • can work with GABA
32
Q

what are gap junctions?

A
  • Gap junctions are channels that physically connect adjacent cells, mediating the rapid exchange of small molecules, and playing an essential role in a wide range of physiological processes in nearly every system in the body, including the nervous system
    • allow ions to diffuse between the 2 neurons, enabling the membrane potential of one to directly and immediately influence that of the other
33
Q

differences between chemical vs electrical synpase?

A
34
Q

what is capacitance and resistance?

A
  • the ability to store charge while resistance is the ability to resist the flow of charge
    • the cell membrane of neurons are characterized by both capacitance, as reflected by the difference in charge between both sides of the membrane, and resistance.
    • capacitance is just a function of how much charge is on both sides of an insulator and the thickness of that insulation (the insulator is the p.m.) so this phenomenon is called membrane capacitance
35
Q

larger neurons have?

A
  • more area to store charge along their membranes so they have a higher membrane capacitance, making them ahrder to depolarize
36
Q

what is cytoplasmic resistance?

A
  • how much the cytoplasm itself impedes the flow of ions
  • the more the cytoplasm imedes the flow of ions, the slower and more difficult conduction will be
  • the larger the neuron, the lower the cytoplasmic resistance
37
Q

what is membrane resistance?

A
  • reflects the ability of a membrane to effectively separate charge
  • high membrane resistance promotes the effective transmission of an action potential
  • high membrane resistance makes the transmission of action potentials more effective
38
Q

what are the effects of myelination?

A
  • increases membrane resistance
  • decreases capacitance
    • conduction is rapid along myelinated segment
39
Q
A

MCAT biology (12 decks)

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