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Block 3 > Cells & Communication In The Nervous System > Flashcards

Cells & Communication In The Nervous System Flashcards

1
Q

What are the functions of the nervous system?

A
  1. Sensation: receptors in skin/organs respond to changes in environment providing information to the CNS
  2. Integration: input is processed + integrated by CNS so decisions and appropriate responses are formulated
  3. Activation: appropriate response forward to target muscles/glands causing contraction/secretion
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2
Q

What does the function of the nervous system depend upon?

A

Anatomical relationship between neurons: axon length, no. of neurons, type of neurons + receptive fields of a circuit

Interaction between neurons: mode of communication, chemical phenotype (transmitter?), how many transmitters + receptor density

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3
Q

How can the nervous system become dysfunctional?

A 
Damage by trauma/disease
Neurons lose ability to produce transmitters
Neurons over/under produce transmitters
Neurons fail to recognise transmitters
Effectors organs fail to respond
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4
Q

How can nervous system dysfunction manifest?

A

Loss: of sensation or function

Gain: appearance of new feature

Change: alteration in behaviour/personality or perception

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5
Q

What types of neurons exist?

A

Principal cells

Interneurons

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6
Q

What type of glia cells exist?

A 
Astrocytes
Ependymal cells
Microglia
Oligodendroglia
Schwann cells
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7
Q

What cell types can oligodendrocyte progenitor cells turn into other than oligodendrocytes?

A

NG2 cells
Polydendrocytes
Astrocytes
Tanycytes

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8
Q

What are tanycytes?

A

Ependymal cells with projecting processes that line the ventricular system + provide information on circulating factors to neurons cells but can also contract periventricular neurons directly

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9
Q

What are the 3 main groups of neurons?

A
  1. Multipolar
  2. Bipolar
  3. Pseudo/unipolar
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10
Q

What are the only true unipolar cells in the human body?

A

Cochlear nuclei + cerebellum brush cells which act as local interneurons

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11
Q

What are the common features of neurons?

A

Dendrites: receptive field sensitive to neurotransmitter input

Soma: metabolic + integrating centre of neuron

Axon: rapid 1 way communication between cell body + terminals

Synaptic terminals: release transmitters + communicate with other cells in a pathway or circuit

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12
Q

What are astrocytes?

A

Large star-shaped cells with multiple dendritic processes that form a bridge between the neuron and blood vessels functioning in structure, homeostasis + neurovascular communication

Major glial cell within CNS - ubiquitous

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13
Q

What are ependymal cells?

A

Simple ciliated cuboidal epithelial cells that form the lining of the ventricular system that produce and move CSF around the CNS

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14
Q

What are microglia?

A

Small glial cells with multiple processes involved in the immune response - activated by trauma (WBCs of the nervous system)

Found anywhere

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15
Q

What are oligodendroglia?

A

Large myelin-producing cells with broad processes of the CNS

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16
Q

What are schwann cells?

A

Large myelin-producing cells with broad processes of the PNS

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17
Q

Where are the majority of brain cancers found?

A

Glia cells

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18
Q

What are multipolar neurons?

A

Principal and interneuronal cells in the CNS with 1 axon + multiple dendrites on soma used for communication

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19
Q

What are bipolar neurons?

A

Cells often found in special senses (e.g. retinal cells in eye, olfactory cells in nose) that have a cell body with 2 principal processes used for communication

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20
Q

What are bipolar neurons?

A

Often sensory cells with one process to their cell body, used for communication

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21
Q

What factors cause the action potential (AP)?

A
  1. Balance between Na+ and K+

2. Myelin

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22
Q

What is the function of myelination?

A

Speeds communication (APs)

Causes saltatory conduction (AP jumps between myelination gaps speeding it up more)

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23
Q

What occurs in an action potential (AP) in terms of ion movements?

A
  1. Rest (-70mV): more K+ IC & Na+ EC so K+ efflux with no Na+ movement
  2. Depolarisation: Na+ channels open so net influx of Na+ which is greater than K+ efflux
  3. AP firing: threshold reached so rapid opening of all Na+ channels causes inward surge of Na+
  4. Repolarisation: Na+ channels close and K+ channels open - initial K+ efflux then influx + excess Na+ efflux
  5. Refractory period: Na+ channels inactivated and K+ current at its strongest so AP cannot be triggered
  6. Afterhyperpolarisation: still K+ influx as rest is being reached before ionic movement balances out
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24
Q

What is the size and duration of an action potential dependent on?

A

Number of Na+ channels present

Duration of channel opening time

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25
Q

What is myelination?

A

Insulation

26
Q

When is myelination of neurons complete? What is the relevance of this?

A

Not complete at birth, it only occurs at 19 months but it is key to developing motor reflexes so babies legs move rapidly everywhere with no control because of this

27
Q

What are examples of myelination disorders?

A

MS (CNS)

Guillain Barre (PNS)

28
Q

What occurs at chemical synapses?

A

Vesicles released from presynaptic terminal to act on receptors in postsynaptic terminal causing fast transmission (slower cell-cell but can cope with higher frequency activity)

Major drug target

29
Q

What occurs at electrical synapses?

A

Gap junctions that allow small molecules + current through as a low-pass filter allowing synchrony and slower transmission (faster cell-cell but more effective at lower frequency’s)

Up and coming drug target

30
Q

What occurs at the neuromuscular junction (NMJ)?

A
  1. AP triggers exocytosis of ACh from synaptic terminal
  2. ACh cross cleft + acts on nicotinic cholinergic receptors on motor end plate
  3. Initiation of muscle contraction
  4. Impulse carried through muscles via T-tubules and SR
31
Q

What is myasthenia gravis?

A

Autoimmune disease affecting NMJ where circulating Abs block the ACh receptors slowing muscle activity + reducing tone

Investigated with NCTs + EMGs

32
Q

What are the 2 main chemical transmitters in the central nervous system (CNS)?

A

Major excitatory transmitter: glutamate

Major inhibitory transmitter: GABA

33
Q

What 3 types of inhibition are responsible for coordinating activity?

A
  1. Direct inhibition
  2. Lateral inhibition
  3. Disinhibition
34
Q

Define synchrony.

A

Coordinates neuronal activity changing the strength of signals at a NETWORK level

Investigated using EEG

35
Q

Define plasticity.

A

Changes strength at a NEURONAL level via up or down regulation of synaptic strength via:

  • LTP/LTD
  • Synaptic morphology
  • Metabolic changes
  • Subunit changes
36
Q

What is direct inhibition?

A

Inhibitory input sculpts the excitatory regular neuronal firing that occurs in the absence of inhibition, producing patterns of activity (coding) which carries information that can be read by the brain so some drugs that increase firing can lead to loss of coding + psychological effects

37
Q

What is lateral inhibition?

A

Activation of excitatory cells also activates associated inhibitory cells so inhibition acts on neighbouring cells to reduce activity strengthening the response of the cell DIRECTLY stimulated

Seen in sensory pathways: vision, touch + olfaction

38
Q

What is disinhibition?

A

Activation of inhibitory circuit leads to excitation i.e. 2 -ve’s = 1 +ve

Pivotal role in basal ganglia circuitry shaping motor function

39
Q

How does synchrony occur in the nervous system?

A

Cell-cell via gap junctions

Pacemaker cells within hypothalamus

40
Q

What is the proposed roles of Long-Term Potentiation (LTP) and Depression (LTD)?

A

LTP: memory formation

LTD: procedural memory i.e. finetuning

41
Q

How do neurotransmitters (NTs) exert their action?

A
  1. Stored in vesicles in pre-synaptic terminal
  2. Released when terminal is depolarised during an AP
  3. Vesicle passes across synaptic cleft
  4. Activates receptors on postsynaptic terminal via binding
  5. Excitatory propagates signal onward whereas inhibitory blocks onward progression
42
Q

How do neuromodulators exert their action?

A
  1. Found in vesicles (or not) co-localised with NTs
  2. Act on receptors or membranes (also glial cells) to indirectly alter neuronal activity
  3. Change sensitivity or kinetics of NT receptor
43
Q

Why are neurotransmitters (NTs) used by neurons?

A

Rapid cell-cell communication

44
Q

What neurotransmitters (NTs) exist and what are their functions?

A

Excitatory:
Glutamate
Aspartate

Inhibitory:
GABA
Glycine

ACh (NMJ)
A/NA (stress/arousal)
DA(motivation/motor function)
5-HT (homeostasis)
Histamine (arousal)
45
Q

What neuromodulators exist and what are their functions?

A 
NPY (appetite)
Substance P (pain)
Vasopressin/ADH (osmoregulation)
Somatostatin (growth)
Anandamide (endogenous cannabinoid)
46
Q

What other transmitters exist and what are their functions?

A

NO, CO, adenosine + ATP (modulatory, not found in vesicles)

47
Q

How do neurotransmitters (NTs) link with disease?

A

Most disorders linked to change in transmitter efficacy - some from single transmitter alteration but most of the time > 1 pathway is affected

48
Q

What motor disorders exist and what transmitter is involved?

A

Parkinsons (DA)
Huntington’s (GABA)
Mysathenia gravis (ACh)

49
Q

What sensory disorders exist and what transmitter is involved?

A

Migraine (5-HT)

Fibromyalgia (substance P/5-HT)

50
Q

What cognitive disorders exist and what transmitter is involved?

A

Alzheimer’s (ACh)
Schizophrenia (DA)
Depression (5-HT/NA)
Epilepsy (GABA)

51
Q

Give an example of how pathways in the nervous system interact.

A

NA levels directly alter 5-HT activity

5-HT levels alter DA activity

DA levels alter ACh activity

ACh levels alter GABA activity

52
Q

What receptors exist in the nervous system?

A

Ionotropic (linked to ion channels)

Metabotropic (GPCRs)

53
Q

Some drugs targeted at receptors are too strong so what is the pharmaceutical industry now trying to develop?

A

Drugs that are subunit specific agonists of receptors

54
Q

What are specialised receptors?

A

Receptors for general sensation and sensory organs developed to respond to particular stimuli + transduce physical to electrical activity

55
Q

What are the 4 main types of cutaneous specialised receptors?

A
  1. Mechanoreceptors: detect tactile sensation (touch, pressure)
  2. Thermoreceptors: detect temperature changes
  3. Nociceptors: detect painful/noxious stimuli
  4. Proprioceptors: detect changes in head/body position
56
Q

What are channelopathies?

A

Mutations in channel subunits of any receptor class that can cause changed kinetics or sensitivity as a result of autoimmune disorders for example

Treatment symptomatic

57
Q

What disorder is commonly caused by channelopathies?

A

Development forms of epilepsy

58
Q

What drug-receptor targets are better for use in the central nervous system (CNS)?

A

Polyvalent non-selective drugs have fewer side effects than drugs that target one specific subtype of receptor (exploring where else drug is acting indicates where adverse effects may occur)

59
Q

What mechanisms are involved in pathogenesis of neuronal and psychological disorders?

A 
Altered neuronal activity
Altered synchrony
Cellular changes
Subcellular change
Genetic/epigenetic changes
60
Q

What physiological levels do we need to understand the functioning of the brain?

A 
Cellular/subcellular
Communication
Coordination
Patterns
Behaviour

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