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Bioregulatory Systems 1 > Cells of the Nervous System > Flashcards

Cells of the Nervous System Flashcards

1
Q

What does the central nervous system consist of?

A
  • Two cerebral hemispheres
  • Brain stem
  • Cerebellum
  • Spinal cord
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2
Q

What does the peripheral nervous system consist of?

A

Nerve fibres originating from the CNS

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3
Q

What are the ridges on the telencephalon (the cerebral hemispheres) called?

A

Gyrus or Gyri (plural)

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4
Q

What are the valleys on the telencephalon (the cerebral hemispheres) called?

A

Sulcus or Sulci (plural).

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5
Q

What are the four lobes of the brain?

A
  1. Frontal
  2. Parietal
  3. Temporal
  4. Occipital
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6
Q

What is the function of the frontal lobe?

A

Responsible for executive functions such as personality

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7
Q

What is the function of the parietal lobe?

A

Contains the somatic sensory cortex responsible for processing tactile information

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8
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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9
Q

What is the function of the occipital lobe?

A

Processing of visual information

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10
Q

What does the brain stem consist of?

A

Midbrain, pons and the medulla oblongata.

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11
Q

What are some the functions of the brain stem?

A
  • Control of respiration and heart rate
  • Target or the source of all cranial nerves.
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12
Q

Where is the cerebellum located and what is responsible for?

A
  • Located in the dorsal region of the CNS and attached to the brainstem.
  • Plays an important role in motor coordination, balance and posture.
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13
Q

Where is the spinal cord attached to and what is its significance?

A
  • Extends down from the medulla
  • Acts as a conduit for neural transmission but can coordinate some reflex actions.
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14
Q

What are some characteristics of neurones?

A
  • Polymorphous (cannot be classified on the basis of shape, location or function).
  • A mature neurone is a non-dividing, excitable cell whose main function is to receive and transmit information In the form of electrical signals.
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15
Q

What are the different types of morphology in neural cells and what are their characteristics?

A
  • Unipolar: 1 axonal projection
  • Pseudo-unipolar: SIngle axonal projection that divides into two
  • Bipolar: 2 projections from the cell body (axon and dendrite)
  • Multipolar: Numerous projections from the cell body (one axon rest are dendrites).
    • Pyramidal cells: ‘pyramid’ shaped cell body
    • Purkinje cells: GABA neurons found in the cerebellum
    • Golgi cells: GABA neurones found in the cerebellum.
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16
Q

What are some common features among neurones?

A
  • All have Soma (cell body, perikaryon):
    • Contains nucleus and ribosomes
    • neurofilaments that help with structure and transport of proteins.
  • All have axons:
    • Long process (nerve fibre) - originates from the soma at the axon hillock
    • Can branch off into collaterals
    • Usually covered in myelin (allows faster transmission).
  • All have Dendrites:
    • Highly branched cell body - not covered in myelin
    • Numerous unlike a singular axon
    • Recieve signals from other neurons
17
Q

What other cell types apart from neurones are found within the CNS?

A
  • Astrocytes
  • Oligodendrocytes and Schwann cells
  • Microglia and ependyma:
18
Q

What are astrocytes?

A
  • Most abundant cell type in the mammalian brain.
  • Function as structural cells
  • Known to play an important role in cell repair, synapse formation, neuronal maturation and plasticity.
19
Q

What are oligodendrocytes and Schwann cells?

A
  • oligodendrocytes are myelin-producing cells of the CNS.
  • Schwann cells perform the same function in the PNS.
  • Each oligodendrocyte cell body sends out numerous projections that form internodes of myelin covering the axons of neurons.
  • Whilst each oligodendrocyte is capable of myelinating a number of axons a Schwann cell only myelinates a single axonal segment.
20
Q

What are Microglia and Ependyma

A
  • Microglial cells are specialised cells that are similar to macrophages and they perform immune functions in the CNS.
  • Ependymal cells are epithelial cells that line the fluid-filled ventricles regulating the production and movement of cerebrospinal fluid.
21
Q

What is the resting membrane potential a consequence of?

A
  • Ionic imbalance between extracellular fluid and intracellular fluid within a neuron with an unequal distribution of major physiological ions.
  • Imbalance and concs. of ions determined by membrane-bound channels and transporters.
22
Q

What is referred to as the reference point when talking about a neurons potential difference?

A
  • The outside of the cell which is said to have 0mv
23
Q

What does the membrane potential signify and what is it during the resting phase?

A
  • It is the potential difference between the inside of the cell (particularly the area adjacent to the cell membrane) and the outside zero reference point.
  • Usually, neurones have a negative membrane potential of around -50 to -90 mV.
  • Thus the resting membrane potential of neurones is said to be -70 mV.
24
Q

Recall the relative concentration (as in higher, lower, highest etc) of the physiologically significant ions that determine resting potential.

A
  • Sodium higher outside cell (highest compared to the others)
  • Potassium higher inside cell (highest compared to the others)
  • Calcium higher outside cell with very little inside so big conc. gradient.
  • Chloride higher outside cell
25
Q

What is the cell said to be when membrane potential becomes more negative?

A

The cell is hyperpolarised

26
Q

What is the cell said to be when membrane potential becomes more positive?

A

The cell is said to be depolarised.

27
Q

What is an action potential generated?

A
  • An action potential generated when there is a brief depolarisation spike in the membrane potential (to around +10 mV) before returning back to the RMP.
  • This action potential is transmitted along the membrane and axon by means of cable transmission and it is the ability to propagate action potentials, which makes neurones ‘excitable.’
28
Q

Why are neurones excitable?

A
  • Because they have an artificially generated resting membrane potential
  • Generated because of uneven distribution of charged ions by membrane proteins.
  • Manipulation of these ions allows
29
Q

What are the four major physiological ions in neurones and why are they used in neurones?

A
  • K+, Na+. Ca+ and Cl-.
  • They are used because cell membranes are impermeable to these ions so transport is regulated by channels and pumps.
30
Q

How is an action potential generated and propagated?

A
  • At RMP VGSCs and VGKCs are closed.
  • When there is a change in membrane potential from around -70 to around -40 mV VGSCs open resulting in an influx of Na+ causing further depolarisation.
  • Then the VGKCs (slower kinetics compared to VGSCs) open at a slower rate causing an efflux of K+ from the cell, resulting in membrane repolarisation.
  • This continues along the axon propagating the action potential in a process known as cable transmission.
31
Q

What happens to the ion concs. following an action potential and how is this tackled by the neurones?

A
  • AP leaves Na and K imbalance which needs to be restored.
  • The Na+K+ATPase or the sodium/potassium pup restores the ion gradient.
32
Q

How does the Na+K+ATPase restore the Na+ and K+ imbalance?

A
  • During resting configuration - Na+ enters vestibule and upon phosphorylation s transported through protein.
  • When active - Na+ is removed using energy from hydrolysis of ATP. Then K+ enters vestibule.
  • Pump returned to resting configuration and now K+ is transported back into the cell.
33
Q

What is saltatory conduction and what happens to the AP when it reaches the presynaptic terminal?

A
  • Neuronal axon is covered in myelin which prevents AP from spreading because it has high resistance and low capacitance.
  • However, myelinated neurones have small gaps in between known as nodes of Ranvier.
  • So AP ‘jumps’ between nodes to the presynaptic terminal in the process of saltatory conduction instead of cable transmission.
  • Finally, at the presynaptic terminal, the AP cannot ‘jump’ anymore so the electrical signal turns into a chemical one.
34
Q

How is the bioelectrical signal converted into a biochemical signal at the presynaptic terminal?

A
  • When AP arrives at nerve terminal it encounters a different species of ion channels than VGSCs and VGKCs.
  • These species are called VGCCs that open when AP reaches terminal and result in an influx of Ca2+ into the cell due to a large conc. gradient of Ca2+ (very little in the cell compared to outside).
  • Ca2+ binds to vesicles that contain neurotransmitters and these than bind to the presynaptic membrane and are released into the synaptic cleft by exocytosis.
35
Q

How is the biochemical signal converted into a bioelectrical signal at the postsynaptic membrane?

A
  • NT binds to the receptors on the post-synaptic terminal
  • Receptors modulate post-synaptic activity propagating the AP.
36
Q

What is the fate of neurotransmitters after being released into the synaptic cleft?

A
  • They are removed fairly quickly after release using different processes.
  1. Enzyme mediated breakdown such as cholinesterase will bind to acetylcholine and break it down. (some cases do not require a breakdown).
  2. Uptake of the broken products back into the presynaptic terminal.

Bioregulatory Systems 1 (5 decks)

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