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BRS - Neurology and neuroscience > Cells of the Nervous System > Flashcards

Cells of the Nervous System Flashcards

1
Q

What does the CNS consist of?

A

two cerebral hemispheres, the brainstem, the cerebellum and the spinal cord

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2
Q

What are the ridges of the brain called?

A

gyri (singular gyrus)

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3
Q

What are the valleys of the brain called?

A

sulci (singular sulcus)

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4
Q

What are the 4 lobes of the brain?

A

Frontal
Parietal
Temporal
Occipital

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5
Q

What is the function of the frontal lobe?

A

Responsible for executive functions such as personality

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6
Q

What is the function of the parietal lobe?

A

Contains the somatic sensory cortex responsible for processing tactile information

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7
Q

What is the function of the temporal lobe?

A

Contains important structures such as the hippocampus (short term memory), the amygdala (behaviour) and Wernicke’s area (auditory perception & speech)

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8
Q

What is the function of the occipital lobe?

A

Processing of visual information

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9
Q

What does the brainstem consist of in descending order?

A

midbrain, pons and medulla

these structures are the target source of all cranial nerves

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10
Q

What does the cerebellum have an important role in?

A

motor coordination, balance and posture

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11
Q

What are the main types of neurone morphologies?

A

Unipolar
Pseudo-unipolar
Bipolar
Multipolar

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12
Q

Describe a unipolar neurone

A

cell body containing nucleus, and a single axonal

projection from the cell body

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13
Q

Describe the structure of a pseudo-unipolar cell

A

Cell body with nucleus and a single projection. However, the single projection is able to fork into two different branches, therefore forming two different projections from one original projection from the cell body

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14
Q

Describe the structure of a bipolar neurone

A

Cell body with the nucleus and the two projections from the cell body.
One will be an axon and the other one is commonly referred to as a dendrite

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15
Q

Describe the structure of a multi-polar neurone

A

Most common type of neurone
Numerous projections from cell body
Only one of these projections will be an axon and rest are dendrites

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16
Q

Name the 3 types of multipolar neurone types

A

Pyramidal cells
Purkinje cells
Golgi cells

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17
Q

Define a mature neuron

A

non-dividing excitable cell whose main function is to receive and transmit information in the form of electrical signals

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18
Q

Give 4 characteristics of neurones

A

Excitable cells of CNS
Heterogenous morphology
Non-dividing cells
Share common features

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19
Q

What are some common features of neurones?

A

Soma (cell body, perikaryon)
Axon
Dendrites

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20
Q

What does the soma (cell body) contain?

A

Nucleus and ribosomes

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21
Q

What are neurofilaments important for?

A

Maintaining structure of neuron and transportation of proteins (e.g. to end our axons or dendrites

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22
Q

What is an axon?

A

Single projection from cell body and it projects from an area known commonly as the Axon hillock
Axon has collateral elements, which can project to different areas or different neurones

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23
Q

What substance usually covers the axon?

A

Myelin

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24
Q

What is the purpose of myelin?

A

Allow signals to be transmitted from axons at a faster rate

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25
Q

What are dendrites?

A

projections from the cell body, but unlike axons there are numerous dendrites from the cell body

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26
Q

What are dendrites important for?

A

Receiving signals from other neurons

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27
Q

What are astrocytes?

A

Astrocytes are the most abundant cell type in the mammalian brain. They function as structural cells and are known to play an important role in cell repair, synapse formation, neuronal maturation and plasticity

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28
Q

What are oligodendrocytes?

A

Myelin producing cells of CNS. Each oligodendrocyte cell body sends out numerous projections that form internodes of myelin covering the axon of neurones

29
Q

What are the myelin producing cells of the of the PNS?

A

Schwann cells

30
Q

How many axons can each Schwann cell myelinate?

A

Only a single axonal segment

31
Q

What are microglia?

A

Specialised cells that are similar to macrophages and they perform immune functions in the CNS.

32
Q

What are ependyma?

A

Ependymal cells are epithelial cells that line the fluid filled ventricles regulating the production and movement of CSF

33
Q

What is said to be the resting membrane potential of neurones?

A

-70mV

34
Q

What does hyperpolarised mean?

A

membrane potential becomes more negative

35
Q

What does depolarised mean?

A

membrane potential becomes more positive

36
Q

What happens when a cell is sufficiently depolarised?

A

Action potential is generated

37
Q

What are 4 major physiological ions?

A

Potassium, sodium, chloride and calcium

38
Q

How do ions impermeable to the cell membrane get transported across it?

A

Transportation regulated by channels and pumps (ion channels)

39
Q

What does the activity of ion channels lead to?

A

Uneven ionic distributions

40
Q

Which ions are more abundant extracellularly?

A

Na+ and Cl-

41
Q

Which ions are more abundant intracellularly?

A

K+

42
Q

In which direction would calcium be transported?

A

Into the cell down its concentration gradient

43
Q

What is the range of a RMP?

A

-40 to -90 mV

44
Q

Which ions are important in the generation of neuronal action potential?

A

Na+ and K+

45
Q

At RMP are VGSCs and VGKCs closed or open?

A

They are closed

46
Q

What is membrane depolarisation?

A

Membrane potential becomes more positive leading to the opening of VGSC and VGKC

47
Q

What leads to membrane repolarisation?

A

efflux of K+ from cells

48
Q

Which channel opens faster?

A

VGSCs

49
Q

What is the purpose of the Na+-K+-ATPase (pump)?

A

restoring the Na+ and K+ gradients

50
Q

Why does myelin prevent the AP from spreading?

A

Myelin has high resistance and low capacitance

51
Q

What are the areas where there are no myelin called?

A

Nodes of Ranvier (high concentration of sodium and potassium channels)

52
Q

What happens in saltatory conduction?

A

AP jumps between Nodes of Ranvier to the presynaptic terminal
Much faster than cable transmission

53
Q

What are the small gaps that exist between neurones known as?

A

Synapse

54
Q

What does the synapse itself consist of?

A

pre-synaptic nerve terminal, which is separated from the postsynaptic cell by an extracellular space known as the synaptic cleft

55
Q

Why is the electrical signal turned into a chemical signal?

A

So that it can cross the synapse (turns back into an electrical signal on the post-synaptic cell)

56
Q

What does an action potential open at the presynaptic terminal?

A

voltage gated Ca2+ channels (influx via vesicle exocytosis)

57
Q

What is released from the pre-synaptic terminal that binds to the post-synaptic terminal?

A

Neurotransmitter

58
Q

How can you remove the neurotransmitter afterwards?

A

Enzymes (e.g. cholinesterase) break it down and allow re-uptake back into the pre-synaptic terminal

59
Q

Outline chemical transmission at a synapse.

A

1) Propagation of the AP: AP is propagated by VGSCs opening. Na+ influx → membrane depolarisation → AP ‘moves along’ neurone. VGKC opening → K+ efflux → repolarisation
2) NT release from vesicles: AP opens VGCC at presynaptic terminal. Ca2+ influx → vesicle exocytosis
3) Activation of postsynaptic receptors - NT binds to receptors on post-synaptic membrane. Receptors modulate post-synaptic activity
4) NT reuptake - NT dissociated from receptor and can be: Metabolised by enzymes in synaptic cleft. Recycled by transporter proteins

60
Q

Outline synaptic organisations between neurones.

A

Axodendritic synapse - Connection between presynaptic terminal → neuronal dendrite

Axosomatic synapse - connection between presynaptic terminal → neuronal soma

Axoaxonic synapse - connection between presynaptic terminal → neuronal axon

61
Q

What is the NMJ?

A

Specialised structure incorporating axon terminal and muscle membrane allowing unidirectional chemical communication between peripheral nerve and muscle.

62
Q

Describe communication between nerve and effector cells.

A

Paracrine - NT release

63
Q

Outline transmission across NMJ.

A

AP propagated along axon → Ca2+ entry at presynaptic terminal

Ca2+ entry → ACh release into synapse

ACh binds to nicotinic ACh receptors (nAChR) on skeletal muscle → change in end plate potential (EPP)

Miniature EPP: quantal ACh release

64
Q

What is sarcolemma?

A

Skeletal muscle membrane

nAChR activation → depolarisation -AP

65
Q

What are T-tubules?

A

Continuous with sarcolemma and closely connected to SR

AP travels through T-tubules

66
Q

Where is SR located?

A

Surrounds myofibrils (contractile units of muscle)

67
Q

What is the function of SR?

A

Ca2+ storage → Ca2+ release following sarcolemma depolarisation

Effect: Ca2+ → myofibril contraction and muscle contraction

68
Q

List and explain 3 disorders of the NMJ.

A

Botulism - Botulinum toxin - irreversible disrupts stimulation - induced ACh release from presynaptic nerve terminal

Myasthenia Gravis - Autoimmune disorder - antibodies directed against ACh receptor. Cause fatiguable weakness

Lambert-Eaton myastenic syndrome (LEMS) - Autoimmune disorder - Abs directed against VGCC

BRS - Neurology and neuroscience (11 decks)

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