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NAS > WEEK 2 > Flashcards

WEEK 2 Flashcards

1
Q

Overview of Nervous System

A

CNS/PNS->Afferent/Efferent System->Somatic/Autonomic NS

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2
Q

What is the Somatic Nervous System?

A

Voluntary division of NS

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3
Q

What defines the Central Nervous System?

A

Meningeal encasement-Brain and Spinal cord. Also encased by cranium and vertebral column.

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4
Q

What defines the Peripheral Nervous System?

A

Part of NS outside CNS, connecting CNS to target organs/tissues and sensory organs to CNS

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5
Q

What is a Neurone (nerve cell)?

A

The specialised functional unit (ie cell) of the NS

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6
Q

General Anatomy of a Neurone

A

Cell body (soma), Axon Hillock, Axon, Axon terminal, Myelin Sheath, Nodes of Ranvier, Internodal and Nodal membrane

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7
Q

What makes up the Somatic NS?

A

Efferent and Afferent

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8
Q

What is the job of the efferent system?

A

Conveys commands from the CNS to target organs/tissues via motor neurones

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9
Q

Where do somatic efferents act?

A

At skeletal muscles via muscle contraction to bring about displacement of limbs (movement) and set muscle tone

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10
Q

What is the job of the afferent system?

A

Carry sensory information from sensory receptors to the CNS via sensory neurones

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11
Q

What do somatic afferents do?

A

Cause sensations which give awareness to the sensory experience

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12
Q

Typical characteristics of Somatic NS

A

Bi-stable state (Active or Inactive)
Largely paralysed during REM sleep
Effector organ is skeletal muscle and is responsible for muscle/motor tone

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13
Q

Morphology of motor neurone is

A

Multipolar (soma at distal aspect of neurone in CNS)

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14
Q

Morphology of sensory neurone is

A

Pseudounipolar (soma found along neurone in PNS)

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15
Q

Features of somatic motor neurones

A

Cell bodies located in either: Ventral horn of spinal cord or cranial nerve motor nuclei of the brain
Largely myelinated: Aalpha (faster than Agamma) or Agamma classification

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16
Q

Features of somatic sensory neurones

A

Varying levels of myelination:
Heavily myelinated=Aalpha and Abeta
Lightly myelinated=Aalpha
Unmyelinated=C-fibres/free nerve endings

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17
Q

What other somatic neurone morphology is there?

A

Bipolar (soma found along neurone)

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18
Q

What is the ‘nerve entry point’ or neurovascular hilum?

A

The geographical centre of any given muscle
The site of entry of a motor neurone into the substance of the muscle (NMJ)
The site of entry/exit of arterial supply/venous drainage to/from the muscle
The site of aggregation of nicotinic receptors of healthy muscles

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19
Q

What is the thickness of the axon dependent on?

A

The level of myelination (thicker axon=more myelination)

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20
Q

Conduction velocity (CV)=

A

5.8xFibre diameter (FD)

21
Q

What is the importance of myelination?

A

provide insulation of otherwise bare axonal membrane, increase axonal conduction velocity, reduce capacitance of neurones (easier activation), creates path of remyelination if nerve axon is cut

22
Q

Characteristic Neuroglia of the PNS and their functions

A

Schwann cells-myelinate peripheral nerve axons (1SC myelinates 1 axon)
Satellite cells-provide physical support for neurones
Microglia-immune and inflammatory functions

23
Q

Characteristic Neuroglia of the CNS and their functions

A

Oligodendrocytes-myelinates many axons at any one myelination segment

24
Q

Membrane envelopes of cranial and spinal nerves (from out to in)

A

Epineurium-ensheaths entire nerve, interfascicular bands attach adjacent nerve fascicles
Perineurium-ensheaths a nerve fascicle (collection of axons)
Endoneurium-ensheaths a single cell’s axon

25
Q

General functions of glia

A

guiding connections, physical support, metabolic support, electrical insulation, signalling

26
Q

Neuronal specialisations for communication

A

Dendrites-input from other neurones
Axon Hillock-action potential generation
Axon-impulse conduction
Axon Terminal-release of neurotransmitter

27
Q

What is the electrical synapse (gap junction)?

A

bidirectional transfer of information via a channel formed by pores in each membrane created by two connexons (composed of 6 connexins each), one in each membrane, allowing ions and small mol. to transfer, allowing synchronous activity between cells

28
Q

Where is the electrical synapse important?

A

glia-neurone or glia-glia communication + cardiac myocytes are connected by gap junctions

29
Q

What is the chemical synapse?

A

unidirectional transfer of information from pre-synaptic to post-synaptic neurone

30
Q

Describe the process of the chemical synapse

A

AP arrives at axon terminal of Pre-S neurone, V-gated Ca2+ ion channels open, Ca2+ enters the Pre-S neurone, synaptotagmin (Ca2+ sensor) causes vesicle movement to and fusion with membrane, docked vesicles release neurotransmitter via exocytosis, neurotransmitter diffuses across synaptic cleft and binds to receptors on Post-S membrane, ligand-gated ion channels open (cause excitation/inhibition), enzymes hydrolyse neurotransmitter, ending Post-S stimulation, neurotransmitter diffuse back into Pre-S neurone and are repackaged into vesicles

31
Q

What is the role of receptors in NS?

A

Membrane spanning protein recognition site for neurotransmitter, causing initiation of intracellular signal

32
Q

What are ionotropic receptors?

A

ligand-gated channels

33
Q

What is the process of ionotropic receptor signalling?

A

transmitter binds, conformational change, channel opening, ion movement

34
Q

What is the electrical effect of ionotropic receptor excitation?

A

neurotransmitter binds, conformational change, Na+ ion channels open, Na+ influx, membrane depolarisation

35
Q

What is the electrical effect of ionotropic receptor inhibition?

A

neurotransmitter binds, conformational change, Cl- ion channels open, Cl- influx, membrane hyperpolarisation

36
Q

What does excitatory mean?

A

more likely to fire AP, promoting generation of Post-S electrical signal

37
Q

What ion causes small excitatory post synaptic potentials (EPSPs)?

A

Na+

38
Q

What ion causes small inhibitory post synaptic potentials (IPSPs)?

A

Cl-

39
Q

What causes small excitatory/inhibitory post synaptic potentials?

A

individual synaptic input

40
Q

What is the process of metabotropic receptor signalling?

A

transmitter binds, conformational change, G-protein activation, activates ‘effector systems’, indirect effects on excitability

41
Q

What can G-protein activation cause?

A

Open/Close of ion channels or stimulation/inhibition of enzymes/secondary messenger systems

42
Q

Examples of metabotropic receptors include

A

ACh muscarinic, GABA(B), monoamine receptors (except 5-HT)

43
Q

Examples of excitatory ionotropic receptors include

A

glutamate AMPA, NMDA, ACh nicotinic receptors

44
Q

Examples of inhibitory ionotropic receptors include

A

GABA(A), glycine receptors

45
Q

What is needed to control neuronal firing?

A

Multiple synaptic inputs

46
Q

Where are synaptic inputs more influencial?

A

To Cell body>To Dendrites

47
Q

What is spatial summation?

A

summing of post synaptic potentials generated at separate synapses

48
Q

What is temporal summation?

A

summing of post synaptic potentials generated at the same synapse if they occur in rapid succession

NAS (9 decks)

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