chapter 6

Question 1

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

Answer 1

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

Question 2

the preganglionic neuron synapses at a peripheral nueron on the?

Answer 2

• 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

Question 3

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

Answer 3

• acetylcholine
  
  • podtganglionic sympathetic fibers rely on norepinepherine

Question 4

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

Answer 4

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

Question 5

The planning of motor control is initiated in the?

Answer 5

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

Question 6

the coordination of movement is heavily dependent on?

Answer 6

• dopamine

Question 7

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

Answer 7

• the neuron

Question 8

what are glial cells?

Answer 8

• 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.

Question 9

astrocytes form the?

Answer 9

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

Question 10

what is one of the notable functions of astrocytes?

Answer 10

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

Question 11

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

Answer 11

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

Question 12

insulating the axons of neurons serves 2 purposes which are?

Answer 12

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

Question 13

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

Answer 13

• saltatory conduction

Question 14

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

Answer 14

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

Question 15

what are ependymal cells?

Answer 15

• produce and circulate celebrospinal fluid in the CNS

Question 16

what are satellite cells?

Answer 16

• control the microenvironment around cell bodies in ganglia and the PNS

Question 17

what is the function of CSF

Answer 17

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

Question 18

what is the structure of a neuron?

Answer 18

Question 19

what is the synaptic cleft?

Answer 19

• a very small gap between 2 neurons

Question 20

what is a graded potential?

Answer 20

• 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.

Question 21

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

Answer 21

• 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+)

Question 22

what is the movement of action potential down a neuron?

Answer 22

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

Question 23

when does repolarization start?

Answer 23

• 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

Question 24

what is the absolute refractory period?

Answer 24

• 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

Question 25

what is the relative refractory period?

Answer 25

* 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

Question 26

what is the role of voltage gated Ca²⁺ channels?

Answer 26

* 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

Question 27

what is degradation?

Answer 27

* 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

Question 28

what is reuptake?

Answer 28

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

Question 29

what is the function of acetylcholine?

Answer 29

* 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

Question 30

what is the function of dopamine?

Answer 30

* used in reward pathways and motor pathways * Parkinson's disease

Question 31

what is the function of glycine?

Answer 31

* inhibitory neurotransmitter of the spinal cord and brainstem * can work with GABA

Question 32

what are gap junctions?

Answer 32

* 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

Question 33

differences between chemical vs electrical synpase?

Answer 33

Question 34

what is capacitance and resistance?

Answer 34

* 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

Question 35

larger neurons have?

Answer 35

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

Question 36

what is cytoplasmic resistance?

Answer 36

* 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

Question 37

what is membrane resistance?

Answer 37

* 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

Question 38

what are the effects of myelination?

Answer 38

* increases membrane resistance * decreases capacitance * conduction is rapid along myelinated segment