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Flashcards in Week 2 Deck (70):
1

What does the cell body (soma of a neuron contain?

nucleus, Golgi apparatus, mitochondia, nucleic acids, usual organelle

2

What is the function of the cell body?

Synthesizes a large quantity and variety of proteins used as neurotransmitters

3

What do dendrites do?

receive information from other neurons (input sites for the cell)

4

Where do axons arise and end?

arise from axon hillock
end in presynaptic terminals

5

What is the length of an axon?

from long (greater than a meter) to short (less the 100um)

6

What is the function of an axon?

Specialized to send neural signals away to other neurons, muscle cells or glands (= “output unit” of the cell)

7

What is a pre-synaptic terminal?

Site of communication between neurons, and between a neuron and a muscle or a gland

8

What are the elements of a pre-synaptic terminal?

presynaptic terminals: fingerlike projections transmitting element of the cell
synaptic cleft: space between neurons
post-synaptic terminal

9

Vetebrate neurons are classified as:

bipolar cells
multipolar cells

10

Bipolar cells have:

2 primary processes from cell body
-dendritic root
axon

11

Pseudounipolar cell

subclass of bipolar cells; sensory neurons having two axons

12

Peripherial axon:

transits signals from the periphery to cell body

13

central axon

conduct signals to the spinal cord

14

How do neurons distinguish from most other cells?

by bioelectrical properties and intercellular communications

15

How do neurons function?

rapid changes in the electrical potential across the cell membrane

16

What is electrical potential?

difference in electrical charge carried by ions on each side of the cell membrane.

17

What are the four types of membrane channels?

modality-gated channels
ligand-gated channels
voltage-gated channels
leak channels

18

What does a modality gated channel open in response to?

mechanical forces (stretch or touch), temperature changes or chemicals; specific to sensory neurons

19

What does a ligand gated channel open in response to?

response to a neurotransmitter binding to the surface of a channel receptor on a postsynaptic cell membrane

20

What does a voltage gated channel open in response to?

in response to changes in the electrical potential across the cell membrane.

21

What is a leak channel?

non gated channel
A small number of ions leak at a slow, continuous rate

22

What causes gated channels to open and close?

‘Gated’ membrane channels open in response to a stimulus and close when the stimulus is removed

23

What are the three types of electrical potentials?

Resting membrane potential
Local potential
Action potential

24

What is the value of the resting membrane potential?

-40 mV to -80 mV

25

What occurs when two forces are balanced?

electrochemical equilibrium

26

What maintains electrochemical gradient in neurons and membrane resting potential?

- Passive diffusion of ions through leak channels in the cell membrane
- Na+/K+ pump

27

What is depolarized?

the membrane potential becomes less negative than the resting membrane potential

28

What is hyperpolarized?

the membrane potential becomes more negative

29

What does hyperpolarization do?

decreases the neuron's ability to generate an electrical signal, and its inhibitory

30

What is local potential?

Initial change in membrane potential

31

How do local potentials spread?

spread passively, confined to a small area of the membrane
-spread only a short distance along the membrane

32

What can increase the strength of a local potential?

temporal and spatial summation

33

What is temporal summation?

combined effect of a series of small potential changes that occur within milliseconds of each other

34

What is spatial summation?

process by which either receptor or synaptic potentials generated in different regions of the neuron are added together

35

What is an action potential?

a large depolarizing signal actively propagated along an axon by repeated generation of a signal

36

_____ depolarization is typically sufficient to trigger an AP

15mV

37

What is threshold stimulus intensity?

stimulus intensity sufficient to produce an action potential

38

What are the 3 events that produce an action potential?

1. Rapid depolarization (voltage-gated Na+ channels open)
2. Decrease in Na+ conduction (channels closed)
3. Rapid repolarization (voltage-gated K+ channels open)

39

What happens during the refractory period?

Na+ channels become inactivated immediately after opening for an AP and require a specific amount of time before they can be activated again for a subsequent AP

40

What is the function of the refractory period?

to promote forward propagation of an AP while preventing backward flow

41

Refractory period is also a period of:

period of hyperpolarization during which the membrane potential is even more negative than during resting (difficult to initiate a subsequent AP)

42

Why will some axons be specialized for faster action potentials because of 2 structural adaptions:

increased diameter
myelination

43

What does an increased diameter of the axon do?

speed of transmission is faster in larger-diameter axons.

44

What does myelination do?

increases efficiency of conduction of AP by decreasing the inherent leakiness of the membrane

45

What is myelination?

a sheath of proteins and fats surrounding an axon; Provides insulation, prevents current flow across the axonal membrane

46

Thicker myelin leads to what?

faster conduction and greater chances for AP propagation

47

What are nodes or ranvier?

small patches of myelinated axons which lack myelin

48

What is saltatory conduction?

quick node-to-node jumping of AP down a myelinated axon

49

Afferent neurons:

carry sensory information from the outer body toward the CNS

50

Efferent neurons:

relay commands from the CNS to smooth and striated muscles and to glands

51

Interneurons:

act throughout the nervous system, processing information locally or conveying information short distances; largest class of neurons

52

What is convergence?

multiple inputs from a variety of cells terminate on a single neuron

53

What is divergence?

single neuron with many branches that terminate on a multitude of cells

54

Ratio of glial cells to neurons in the brain:

3:1
New literature : 9:1

55

Glial cells:

form a critical support network for neurons

56

Types of glia cells:

macroglia
microglia
glial stem cells

57

Types of macroglia:

astrocytes
oligodendrocytes
schwann cells

58

What are astrocytes?

-star shaped macroglia found throughout the CNS
-primarily in gray matter
-act as scavengers

59

What stimulates astrocytes?

signals from adjacent neurons or by mechanical changes
spread waves of Ca2+ to neighboring astrocytes

60

What do oligodendrocytes and schwann cells do?

-form myelin sheath and are found primarily in white matter

61

What do oligodendrocytes myelinate?

neurons in the CNS

62

What do Schwann cells myelinate?

neurons in the PNS

63

What are microglial cells?

- phagocyte that resides in CNS
- act as immune system of CNS
- activated during development of nervous system following injury, infection or disease

64

What are glial stem cells?

- found throughout developing and adult brain
- immature and undifferentiated cells
- retain capacity to proliferate and generate

65

What is neuroinflammation?

the response of the CNS to infections, diseases and injuries

66

What is a beneficial effect of neuroinflammation?

when reactive microglia clean up and remove debris

67

What is a harmful effect of neuroinflammation?

- Death of neurons and oligodendrocytes, inhibition of neural regeneration
- Correlation between abnormal glial activity and neural damage

68

What is peripheral neuropathy?

any pathological change involving peripheral nerves

69

What does peripheral neuropathy result in?

destruction of myelin surrounding the largest, most myelinated sensory and motor fibers
-disrupted proprioception and weakness

70

What are the 4 types of MS?

relapsing/remitting
secondary progressive
primary progressive
progressive relapsing