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202: Theme 1 > Neurons + Neural Tissues > Flashcards

Neurons + Neural Tissues Flashcards

1
Q

The Central Nervous System

A
  • Brain + Spinal Cord
    • information processing: integrative function
    • reflexes and behaviour
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2
Q

The Peripheral Nervous System

A

constitutes the cranial nerves and the spinal nerves

  • Sensory detection
  • Motor activation
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3
Q

Ganglion

A
  • a group of cell bodies outside the CNS (inside the CNS groups of neurons are called nucleus)
  • Motor ganglion is autonomic
  • Parasympathetic ganglion: smaller neurons - with eccentric nuclei
    • in sensory ganglia the nucleus is central
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4
Q 
# Define:
Caudal

Rostral

Ventral

Dorsal

Medial

A

Caudal = toward tail (from Latin)

Rostal = toward the beak/nose (from Latin)

Ventral = toward the belly and opposite the dorsum (from Latin)

Dorsal = toward the spine/back and opposite the ventrum (from Latin)

Medial = toward the mid-sagittal plane (ie the centre line that extends from head to foot in a human)

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5
Q

Brodmann Areas of the Neocortex

  • Area 4:
  • Area: 17
A
  • regions of th3 cortex numbered 1-52
  • boundaries determined by the cellular architecture
    • each area has a particular set of inputs and outputs
  • Brodmann Area 4: is the primary motor cortex
  • Brodmann Area 17: Primary visual cortex
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6
Q

Pyramidal Cell

A

found in the neocortex (cerebral cortex), used in measuring EEG signals

  • involved in thinking
  • has many dendrites collaterals
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7
Q

Purkinje cell

A

found in the cerebellum

  • has very complicated arborization
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8
Q

Dorsal Root Ganglion

A

DRG are psudonunipolar sensory neurons

  • the dorsal root is the neuron leading up to the entry of the spinal cord, and the DRG is a small touching on that root into the spinal root
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9
Q

Interneurons (relay neurons)

A

only occur in the CNS and generally process signals- not sensory or motor

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10
Q

Glial Cells

A

These are non-neural cells that form the interstitial tissue of the nervous system: astrocytes, oligodendroglia, microglia, ependymal cell, pia mater

  • have no action potentials
  • do not form synapses
  • are able to divide
  • form the myelin sheathes
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11
Q

Oligodendrocyte

A

a neuroglial cell in the CNS

  • smaller than astrocytes with fewer and shorter branches
  • cytoplasm doesn’t contain neurofilaments
  • In white matter, these cells are located along long rows along myelinated fibres and are known as interfascicular oligodendrocytes
    • ​are involved with myelinating the neurons
  • In grey matter, they are called perineural oligodendrocytes​​
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12
Q

Astrocytes

A

a neuroglial cells

  • provide electrical insulation for the neurons
    • can take up the neurotransmitter GABA released from nerve terminals, which stops the action potential
    • can take up excess extracellular K+ through their membrane channels and dissipate it over a large area
  • Protoplasmic Astrocytes
    • found in grey matter neurons, have thicker and shorter process: terminate in ‘end-feet’
    • act as metabolic intermediaries for neurons
    • end-feet join together to form a limiting membrane along the outer surface of blood vessels and the pia mater membrane
    • forms part of the blood-brain barrier
  • Fibrous Astrocytes
    • ​mainly in white matter, with little branching
    • repair damaged tissue (scarring possible)
  • Müller Cells
    • ​found in the retina
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13
Q

Microglia

A

Neuroglia cells that are immune cells, protect neurons from disease, migrate to injury sites, engulf microbes/debris

  • originates from the mesoderm
  • the smallest of the glial cells
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14
Q

Ependymal Cells

A

Neuroglia cells that line the brains ventricles and the central canal of the spinal cord: they form the CNS there are three types

  • Ependymocytes
    • cuboidal/columnar cells that possess microvilli
    • presence of microvilli suggestive some absorptive function- also facilitate the flow of CSF
  • Tanycytes
    • ​found in the floor fo the third ventricle
    • their processes texted into the brain tissue where they juxtapose blood vessels and neurons
    • suggestive involvement in the transport of hormones from the CSF to capillaries of the portal system and also from the hypothalamic neurons to the CSF
  • Choroidal epithelial cells
    • ​present in the choroid plexus
    • involved in the production and secretion of CSF
    • have tight junctions that prevent CSF from spreading to adjacent tissue
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15
Q

Schwann cells

A

Glial cells in the Peripheral Nervous System

  • production and maintenance of the myelin sheath
  • Nodes of Ranvier allow for saltatory conduction hence faster transmission of action potentials
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16
Q

Satellite Cells

A
  • glial cells that exist in the PNS
  • support neurons, regulate the exchange of materials between neurons and interstitial fluid (similar to what astrocytes do in the CNS)
17
Q

the Meninges

A
  • made up of, three layers of connective tissue membranes:
    • Dura Mater
      • ​contains a lot of collagen fibrils
  • ​Leptomeninges (thin and fine)
    • Arachnoid Mater
      • ​no collagen fibrils
    • Pia Mater
18
Q

Glioma

A

largest group of primary tumours derived from glial cells

  • highly malignant, grow rapidly
  • difficult to remove completely with surgery
  • usually inside cranium
19
Q

Neuroblastoma

A
  • most common in children & infants
  • outside of cranium
  • derived from neural crest cells from the sympathetic NS
    • often see an increase in catecholamine levels
  • treatment and prognosis varies depending on the type of neuroblastoma present: survivors often develop neurological problems ~30 yrs later
20
Q

Electrical Synapses

A
  • Faster than chemical synapses
  • can be bidirectional
    • rectifying vs non-rectifying(most in mammals)
  • Smaller Gap
  • No plasticity- no learning
  • No amplification
  • Used for defensive reflexes (in invertebrates), in the retina and the brain
  • used when the activity of neighbouring neurons need to be highly synchronized
21
Q

Draw out and explain the phases of the action potential

A
22
Q

Coding intensity of synaptic inputs by neurons

A
  • Firing frequency = intensity of the neural activity
    • increasing threshold for an AP lowers firing frequency
    • increasing excitatory synaptic activity increases firing frequency
    • small currents that are long (>10msec), create a higher threshold potential for AP generation than larger currents
      • this is due to accommodation of Na+ current (this inactivates during the slower subthreshold depolarization)
      • accommadation=diminishes in the face of continued stimulation (first response is stronger than consecutive responses)
23
Q

The Excitability of Neurons

A

Excitability= how easy it is to start a nervous signal

  • Increased threshold lowers the excitability
    • Threshold= voltage above which the action potential fires
  • Can change due to psychotropic drugs
24
Q

How does ionic permeability effect the control of voltage?

A
  • increased permeability of K+ makers a membrane more negative and Na+ is the opposite
  • the voltage of the cell membrane is determined by inter-related feedback loops
  • At rest, Vm = ~Ek
    • based on a weighted average of K, Na, Ca and Cl,
    • the conductance of K+ is much greater than Na= or Ca2+,
    • since there is always some conductance of the other ions Vm is not exactly Ek
25
Q

Lignocaine/Lidocaine

A
  • blocks Na+ channels in pain neurons
  • raises the threshold -> lowers the excitability
  • stops action potentials locally

applied as a local anaesthetic, applied topically

26
Q

Carbamazepine

A

an anticonvulsant: antiarrhythmic drugs like

  • blocks sodium channels
    • quinidine, and pufferfish poison tetrodotoxin (very powerful)
  • raises AP threshold and lowers the excitability
27
Q

Nagging, King, easy as, Club for Alibaba

Equilibrium potentials

A
  • ENa = +60 mV
  • EK = -90 mV
  • ECa = +123 mV
  • ECl = -40 mV (in neurons –65 mV)
28
Q

Nernst Equation

A
  • used for Deriving Equilibrium Potentials
29
Q

Graded potentials

A
  • Decrease as they move along the neuron away from the source (they are not amplified)
  • Electrically localised
  • Last a long time
  • flatter in shape, are conducted almost instantly
    • the size and duration of the potential is proportional to the stimulus

Found in receptor cells (rods and cones) and in the inner cochlear

  • Graded potentials transmit action potentials, through Nodes of Ranvier, allows for reamplification of the initial signal even when it’s far away from the source
  • Faster with a larger diameter and along myelinated neurons
30
Q

What is the clinical importance of Conduction Velocity?

A
  • Nerve conduction studies are used for evaluation of paresthesias
    • numbness, tingling, burning
  • Evaluation of weakness of the arms and legs
    • can help diagnose other pathologies

202: Theme 1 (14 decks)

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