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BS129: Physiology, Neurobiology and Metabolism > Neurobiology (Lecture 20-25) > Flashcards

Neurobiology (Lecture 20-25) Flashcards

1
Q

What does the nervous system do?

A
  • Sensory system: recieve and interpret information abt the internal and external environments of the body
  • Integrating system: making decisions abt information
  • Motor system: to organize n carry out action
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2
Q

What are the 3 parts of the neuron?

A
  • Dendrites
  • Soma (cell body)
  • Axon
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3
Q

What are neurons?

A

Individual cells, which are not continuous to other neurons

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4
Q

Dendrites

A
  • Increase surface area
  • Recieve inputs
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5
Q

Axon

A

Carries information

Over distances

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6
Q

Myelin

A

Coats axon

Improves conduction

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7
Q

Node of Ranvier

A

Break in myelin sheath

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8
Q

Terminals

A
  • Output region
  • Transmitter release
  • Synapse w other neurons
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9
Q

How should we classify neurons?

A
  • Morphology
    • Multipolar, unipolar
  • Interneurons vs principle neurons
    • Interneurons: local circuits
    • Principle neurons: extend process over long distances
  • Neurotransmitter
    • Cholinergic
    • Glutamatergic
    • GABAergic
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10
Q

How do things get to n from axon terminals?

A
  • Anterograde transport
    • Soma down axon to terminals
  • Retrograde transport
    • From terminals to soma
    • Worn out mitochondria, SER
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11
Q

Mechanism of axonal transport

A
  • Requires hydrolysis of ATP n microtubules
  • Protein shuttles that move in either direction in the microtubule network
  • Microtubules are polarized (positive n negative end)
  • Molecules “walk”
  • This process is catalyzed by ATP (energy-intensive process)
  • TAU protein becomes dysfunctional in Alzheimer’s
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12
Q

Astrocytes

A
  • Making contact w blood vessels
  • Associated w synapses
  • Correct ionic environment
  • Release gliotransmitters (ATP, glumate, D-serine)
  • Provide metabolic fuel for neurons
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13
Q

Oligodendrocytes

A
  • Cells that myelinate axons in the brain and CNS
  • Schwann cells myelinate axons in peripheral nervous system
  • Oligodendrocytes can myelinate multiple axons
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14
Q

Microglial cells

A
  • Immune cells of nervous system
  • Acts as scavengers
  • Clean up cellular debris
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15
Q

Describe the structure of vertebrate ganglia

A
  • Cell body
    • Outside of the ganglia
    • Send their axons into the neuropils
  • Neuropil: dense regions of nerve fibers devoid of cell bodies
  • Axons in tracts
    • Run together in nerve trunks [protect axons from damage]
  • Ganglion sheath
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16
Q

Encephalization quotient

A
  • Brain weight/body weight
  • Expectation: linear correlation
  • Our brain has become folded
    • Cell sides and gyri pack more “brain” into skull
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17
Q

What are the meninges?

A
  • Surround the CNS
  • Brain suspended in jacket of cerebrospinal fluid
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18
Q

What are the 3 layers of meninges

A
  • Dura mater: protects the brain
  • Arachnoid mater
  • Pia mater: thin membrane that covers actual surface of brain tissue
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19
Q

Falx cerebri

A
  • Invaginations in the brain b/w the gyri n the longitudinal fissure
  • Allows the blood vessels to penetrate the tissue further from the surface of the brain
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20
Q

Importance of the ventricular system

A
  • Removes waste products
  • Supplies brain n spinal cord w nutrients
  • Buffers changes in blood pressure n protects the brain
  • Supplies brain w fluid during dehydration
  • Allows the brain to remain buoyant
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21
Q

Composition of CSF

A
  • Low levels of protein n glucose
    • To protect the brain from glucose fluctuations in the blood
    • Ability of astrocytes to regulate glucose uptake into the brain
22
Q

Lumbar puncture

A
  • Examine the state of the brain by proxy of what’s happening in the CSF
  • Expected: clear colourless fluid
  • Blood → subarachnoid hemorrhage
  • Yellow CSF → old blood or jaundice
23
Q

CSF n Alzheimer’s Disease

A

Based on the accumulation of proteins in the CSF

24
Q

What is the structure of invertebrate ganglia?

A
  • Cell body
  • Axons in neuropil
  • Ganglion sheath
  • Axons in tracts
25
Q

Frontal lobe function

A
  • Executive function
  • Judgement
26
Q

Corpus callosum

A
  • White matter tract
  • Axons in 1 hemisphere
  • Instances when corpus callosum is surgically cut through
    • Epilepsy
27
Q

Midbrain

A
  • Visual n auditory information
  • Motor control
  • Sensation
28
Q

Pons

A
  • Links w cerebellum
  • Modifies medulla output
29
Q

Medulla

A
  • Respiration
  • Cardiovascular function
30
Q

Cerebellum

A
  • Balance
  • Gait
  • Fine movement
  • Posture
31
Q

Thalamus

A
  • Relay station
  • Integrates sensory information
32
Q

Hypothalamus

A
  • Autonomic control
  • Homeostasis
  • Endocrine control
33
Q

Hyperpolarization

A

Membrane potential becomes more negative

34
Q

Depolarization

A

Membrane potential becomes more positive

35
Q

What results in a resting membrane potential?

A
  • Intact cell (semi-permeable) membrane
  • Ionic concentration gradients n ionic permeabilities
  • Over the long term: metabolic processes
36
Q

Compare the IC n EC ionic concentration gradients

A
  • Higher in IC
    • Potassium
    • Anions (proteins, phosphate groups)
  • Higher in EC
    • Sodium
    • Chlorine
37
Q

What is the ideal plasma membrane?

A

Impermeable to Na+ ions thus changing Na+ concentration will not affect resting potential

38
Q

What maintains the balance b/w K+ ions moving out of the cell?

A
  • Concentration gradient of K+ ions to leave the cell
    • Favouring efflux of K+ ions to outside the cell
  • Inside of the cell is -80mV which counteracts the concentration gradient → keeps K+ inside the cell
39
Q

How does the membrane potential change w EC K+ if membrane is only permeable to K+ ions

A

As we increase EC K+ ions → membrane becomes depolarized

40
Q

What are the important physiological implications of K+ concentration gradient?

A
  • Epileptic seizure
    • Lots of K+ ions that leave the cell -> depolarize adjacent neurons -> cause them to become excitable
    • Glial cells attempt to distribute potassium cells from intensively active sites
41
Q

Why is the membrane potential usually less negative than Ek?

A
  • Cell membrane is not completely impermeable to Na+ (Na+ moves in)
  • There is K+ leakage (K+ moves out)
  • Na+ and K+ movements changes membrane potential
  • This positive charge reduces the overall negativity of the resting membrane potential
42
Q

Action potential

A
  • Major mechanism of neuronal communication
    • Neurons take in information via dendrites n assimilate this information
  • Travels down axon to terminals
  • Does not decrement by virtue of myelin sheath
  • Trigger transmitter release
43
Q

Action potential depends critically on Na ions. Explain.

A

If you drop Na conc by 2/3 then overshoot (which is important for action potential propagation) was not achieved (Hodgkin and Katz 1949)

44
Q

Why does Na+ move into cell when channels open?

A
  • Concentration gradient: inward
    • Na+ outside cell so chemical driving force
  • Electrical gradient: inward
    • Draw sodium ions inside the cell
  • Driving force = conc gradient + electrical gradient
45
Q

What initially depolarizes neurons to open the voltage-gated Na+ channels?

A
  • Synaptic transmission
    • Excitatory postsynaptic potentials (EPSPs)
      • Generated by neurotransmitter release at synapses can depolarize the postsynaptic neuron n open voltage-gated Na+ channels
  • Generator (receptor) potentials
    • Activation of receptors that are permeable to sodium ions
      • Sensory neurons: can depolarize membrane by allowing Na+ ions to flow in
  • Intrinsic properties
    • Pacemaker activity in heart
      • Rhythmic depolarizations occur due to intrinsic mechanisms
  • Experimental
    • Electrical stimulation
46
Q

Why is Na+ channel opening a positive feedback loop?

A
  • Membrane potential of neuron reaches threshold level
    • Voltage-gated Na+ channels open
  • Na+ ions influx
    • Leads to further depolarization
      • Opens more channels
47
Q

Action potentials have all “all or nothing” property. Explain.

A

Once the threshold lvl of depolarization is reached, AP is generated at full magnitude regardless of the strength of the initial stimulus

48
Q

Explain the 2 ways the repolarization of the AP occurs

A
  • Voltage-gated sodium channels start to close
    • Deactivate → no more Na+ ions going in
  • Activation of K+ channels
    • Time lag → allows Na+ channels to open
    • Moves K+ out of the cell → makes inside of the cell more negative [losing + ions]
49
Q

What causes hyperpolarization?

A
  • Change in the membrane potential of a neuron where potential becomes more negative than resting membrane potential
  • K+ efflux
    • Membrane becomes permeable to K+ ions → they move out of the cell → membrane potential becomes more negative
50
Q

What are the key events involved in the repolarization of the membrane after an action potential?

A
  • Around threshold Vm, the membrane becomes much more permeable to Na+ ions
  • This leads to depolarisation and further recruitment of VG Na+ channels
  • Depolarisation results in VG Na+ channels inactivation (closure)
  • After a delay VG K+ channels open
  • Both contribute to the repolarisation of the membrane after the action potential
51
Q

Explain the ball n chain method in relation to VG Na+ channel inactivation

A
  • Positively charged activation gate keeps channel closed [repel Na+ ions]
  • Depolarization of membrane cause activation gate to swing out of the way
    • Allows Na+ ions to enter n cause further depolarization
  • Inactivation “ball” rapidly enters the channel to block Na+ influx

BS129: Physiology, Neurobiology and Metabolism (2 decks)

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