Midterm 1 Review

Question 1

neurons

Answer 1

brain consists of ~100 billion neurons

Question 2

neuroglia

Answer 2

a glia:neuron ratio less than 1:1

Question 3

synapses

Answer 3

anywhere from 1k to 10k synapses for each neuron

Question 4

Brain cells broken into two groups:

Answer 4

neurons & neuroglia

Question 5

4 types of glial cells

Answer 5

astrocytes, oligodendrocytes, microglia, ependymal cells

Question 6

brain tissue broken down into

Answer 6

gray & white matter

Question 7

gray matter

Answer 7

mostly unmyelinated neurons, most of which are interneurons; this is area of nerve connections & processing

Question 8

white matter

Answer 8

mostly myelinated neurons that connect regions of gray matter to each other & rest of body. myelinated neurons transmit nerve signals much faster than unmyelinated axons. white matter acts as info highway of brain to speed connections between distant parts of brain & body.

Question 9

neuroglia or glial cells

Answer 9

act as helper cells of brain; support & protect neurons

Question 10

neuronal circuits are

Answer 10

rarely linear, frequently converge/diverge & are often bidirectional (reciprocal)

Question 11

1-2% of human genes are

Answer 11

“brain-specific”

Question 12

Cajal developed

Answer 12

“neuron doctrine”

Question 13

4 functional zones of neuron

Answer 13

1) input
2) integration
3) conduction
4) output

Question 14

1) zone of input in a neuron:

Answer 14

soma+dendrites

Question 15

2) zone of integration:

Answer 15

axon hillock

Question 16

3) zone of conduction:

Answer 16

Axon

Question 17

4) zone of output

Answer 17

terminal buttons @ ends of axon

Question 18

3 ions to remember

Answer 18

potassium K+
sodium Na+
calcium Ca++

Question 19

potassium (K+)

Answer 19

20mM extracellular concentration

400mM intracellular concentration

1/20 extra/intra ratio

Question 20

sodium (Na+)

Answer 20

440 mM extracellular concentration

50 mM intracellular concentration

9:1 extra/intra ratio

Question 21

calcium (Ca++)

Answer 21

10mM extracellular concentration

0.0001 mM intracellular concentration

100,000:1 extra/intra ratio

Question 22

sodium-pottasium pump (Na/K-ATPase)

Answer 22

moves 2 potassium ions into a neuron for every 3 sodium ions that it moves out, consuming 1 molecule of ATP

Question 23

voltage gated Na+ channels______than voltage gated K+ channels; they also______.

Answer 23

open more quickly; close earlier

Question 24

simaltaneous opening of both Na+ & K+ channels (overlap) is

Answer 24

metabolically inefficient

Question 25

Absolute refractory period

Answer 25

starts @ -55mV & includes depolarization & repolarization (when AP happens)

Question 26

relative refractory period

Answer 26

@ end of action potential & includes hyperpilarization (undershoot meaning it goes past the resting potential @ -70mV)

Question 27

absolute refractory period

Answer 27

time from opening of Na+ activation gates until closing of inactivation gates; neuron cannot respond to another stimulus

Question 28

relative refractory period

Answer 28

follows absolute refractory period. Na+ gates closed, K+ gates open & repolarization is ocurring. during this period only a strong stimulus can generate AP.

Question 29

above threshold_______triggers AP by______________.

Answer 29

depolarization; opening voltage-gated Na+ channels

Question 30

myelin sheaths

Answer 30

increase speed of AP propogation

Question 31

nodes of ranvier

Answer 31

between myelin sheath have higher concentration of Na+ ion channels which help AP “leap” down axon faster than in unmyelinated axons