011 the neuron

Question 1

roughly how many neurons are there in the human brain?

Answer 1

100 billion

Question 2

roughly how many glia are there per neuron?

Answer 2

10 glia per neuron

Question 3

how can you measure the number of neurons in the brain?

Answer 3

• blend brain with buffer into a liquid
• count number of nuclei per certain volume of liquid and multiply up for whole brain
• use stain to differentiate neuron and others

Question 4

what stains are used to see neurons?

Answer 4

methylene blue and silver stain

Question 5

how did the first scientists (Golgi and Cajal) see neurons?

Answer 5

used microscope with sunlight and mirror and stains
- hand drew what they saw under the microscope
- saw different planes/levels to get the overall image

Question 6

what is the largest neuron cell?

Answer 6

• Betz cell

Question 7

why do neurons have such a large axon compared to their body/soma?

Answer 7

• there is bidirectional transport from the cell body to the cell terminal
• need lots of microfilaments, cytoskeleton, ion channels and receptors = need lots of space

Question 8

what type of neuron cell does this EM show?

Answer 8

pyramidal cell

Question 9

what type of neuron cell does this EM show?

Answer 9

pyramidal cell

Question 10

what can you see in this EM of a pyramidal neuron?

Answer 10

• big central nucleus
• lots of mitochondria, golgi bodies, RER
• thin cytoplasm
• dendrites

Question 11

what are gray type 1 and 2 synapses in the cerebral cortex?

Answer 11

• gray type 1 = asymmetric in contracting and excitatory - uses glutamate
• gray type 2 = symmetric in contracting and inhibitory - uses GABA

Question 12

what is this an image of?

Answer 12

• a medium spiny neuron

Question 13

what are medium spiny neurons?

Answer 13

• GABAminergic neurons in the striatum and basal ganglia
• projects GABA to D1 and D2 receptors (inhibitory)
• contains neuropeptides enkephalin, substance P and dynorphin
• (role in controlling movement)
• receives info from cerebral cortex, thalamus and substantial nigra and projects to globus pallidus and substantial nigra

Question 14

describe the direct dopaminergic pathway in the brain

Answer 14

• cerebral cortex –> striatum + –> Globus pallidus internal/substantia nigra pars reticulata –> thalamus (VA/VL/DM) –> cerebral cortex…

Question 15

what are the neurotransmitters involved in the direct dopaminergic pathway in the brain?

Answer 15

cerebral cortex –> striatum = glutamate +
striatum = dopamine +
striatum –> GPi/SNr = GABA -
GPi/SNr –> thalamus = GABA -
thalamus –> cerebral cortex = glutamate +

Question 16

what are the effects of the direct dopaminergic pathway in the brain?

Answer 16

• increase thalamic output = increase movement

Question 17

describe the indirect dopaminergic pathway in the brain

Answer 17

cerebral cortex –> striatum - –> Globus pallidus external –> subthalamic nucleus –> Globus pallidus internal/substantial nigra pars reticulata –> thalamus –> cerebral cortex
or
….. Globus pallidus external –> Globus pallidus internal/substantia nigra pars reticulata….

Question 18

describe the neurotransmitters in the indirect dopaminergic pathway in the brain

Answer 18

cerebral cortex –> striatum = glutamate +
striatum = dopamine -
striatum –> GPe = GABA -
GPe –> STN = GABA -
STN –> GPi/SNr = glutamate +
GPi/SNr –> thalamus = GABA -
thalamus –> cerebral cortex = glutamate +
or
…. GPe –> GPi/SNr = GABA - …

Question 19

what are the effects of the indirect dopaminergic pathway in the brain?

Answer 19

• decreases thalamus output = inhibits movement

Question 20

roughly how many synapses are formed by 1 DA neuron in the striatum?

Answer 20

between 1-3 million