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+ BIOL 371 > Lecture 3: Neural Circuits and Their Function > Flashcards

Lecture 3: Neural Circuits and Their Function Flashcards

1
Q

What is a complete neural circuit?

A

from sensor (afferent) to effector (efferent) – can involve as few as two neurons

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2
Q

What are action potentials (spikes or nerve impulses) ?

A

electrical mechanism that nervous systems have evolved that allow for conduction of information across distances

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3
Q

What can extracellular recordings record?

A

AP – because of their large amplitude

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4
Q

What can intracellular recordings record?

A

PSP

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5
Q

What are post-synaptic potentials?

A

signals induced when a neurotransmitter activates receptors at a synapse

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6
Q

What is neuromodulation?

A

term for synapses whose effects are not simple PSPs

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7
Q

What are three classes of effects that can occur when a synapse is activated?

A
  • excitation
  • inhibition
  • modulation
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8
Q

What is excitation?

A

activating the synapse causes EPSP

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9
Q

What is inhibition?

A

activating the synapse causes IPSP

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10
Q

What is modulation?

A

activating the synapse causes effects other than simple PSPs

these effects can often be changes to the strength of other neighbouring synapses on the postsynaptic cell – synapse ‘modulates’ its target

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11
Q

When is a synapse considered ‘activated’?

A

when AP occurs in presynaptic neuron’s axon (and axon terminal), which causes release of neurotransmitter from axon terminal – neurotransmitter will be detected by postsynaptic cell

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12
Q

What is grey matter?

A

CNS areas with somata and neuropil (dendrites, axon terminals and synapses)

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13
Q

What is white matter?

A

consists of (myelinated) axons linking the neurons in two or more regions of grey matter

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14
Q

Sensory vs. Motor Neurons

Polarity

A

SENSORY: often ‘pseudo-unipolar’ – dendrite joins axon, not soma

MOTOR: multipolar – one axon, many dendrites

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15
Q

Sensory vs. Motor Neurons

Location of Somata

A

SENSORY: outside CNS in dorsal root ganglion

MOTOR: (and dendrites) In ventral grey matter

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16
Q

Sensory vs. Motor Neurons

Location of Axon

A

SENSORY: enters spinal cord/hindbrain on dorsal side, into dorsal grey matter

MOTOR: Leaves spinal cord via ventral root and travels directly to skeletal muscle cells

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17
Q

Within a circuit, what is a neuron’s activity is generated from?

A

sum of its inputs across time and space – most neurons (including those involved in simple reflexes), receive synapses from many different neurons, and each synapse is activated every time its presynaptic axon fires an AP

18
Q

What is spatial activation?

A

summation in different points of space (different synapses)

19
Q

What is temporal activation?

A

summation in same space, but at different times (repeated activation)

20
Q

What determines the postsynaptic neuron’s activity/output?

A

integrated total of all recent inputs, such as spatial and temporal summation (measured by APs generated in its axon hillock)

21
Q

What is convergence?

A

property of postsynaptic neuron in which multiple inputs converge onto it – receiving information

22
Q

Where does divergence occur?

A

in axons

23
Q

Where does convergence occur?

A

in dendrites

24
Q

Where does convergence occur?

A

in dendrites

25
Q

What is divergence?

A

how many separate cells are being communicated with

26
Q

What does dorsal grey matter contain?

A

interneurons processing sensory info

27
Q

What does ventral grey matter contain?

A

somatic motor neuron somata

28
Q

What effect does changing the position of motor neurons in the ventral horn have?

A

scrambling the position of motor neurons within the ventral horn scrambles motor behaviour

29
Q

How are neurons mapped in the zones of grey matter?

A

between (and within) ten zones (I-X), different functional neuron subtypes are topographically mapped

30
Q

How are neurons mapped in the dorsal horn (I-IV)?

A

sensory neurons that carry different information make synapses with distinct interneuron types concentrated in different zones (function-o-topy)

31
Q

How are neurons mapped in the ventral horn (IX)?

A

motor neurons innervating muscle cells from neighbouring muscles are located next to each other (somatotopy), at any particular spinal cord level

  • upper limb muscle motor neurons: somata in cervical (neck) region of spinal cord
  • lower limb motor neurons: found lower in spinal cord
32
Q

What do efferent neurons of ANS control?

A

non-motor organ systems – neurons innervate visceral organs, muscles, skin and limbs

33
Q

How is the overall organization of ANS similar to SNS? (2)

A
  • circuit organization of afferents, interneurons, and efferents
  • somatotopic mapping – neuron cell body position within nervous system roughly corresponds to position of target organ in the body
34
Q

What is the visceral nervous system?

A

part of PNS that consists of all the nerves that relay information between CNS and visceral organs

35
Q

What is the autonomic nervous system?

A

part of PNS that regulates involuntary physiologic processes – including heart rate, blood pressure, respiration, digestion, and sexual arousal

36
Q

How many neurons does the ANS pathway have?

A

two neurons (extra, compared to SNS) in their effector pathways (to reach their targets) – preganglionic and postganglionic

  • preganglionic efferent neuron’s soma is located in lateral horn grey matter
  • synapse between two neurons (and postganglionic neuron’s soma) are located in autonomic ganglia, outside CNS
37
Q

How many neurons does the SNS pathway have?

A

single efferent neuron sends axon from ventral horn grey matter in spinal cord, to target organ (skeletal muscle)

motor neurons only have excitatory effects on their target muscles, and each skeletal muscle cell will only receive one synapse from one motor neuron

38
Q

What is the antagonistic effect of the parasympathetic and sympathetic divisions of the ANS caused by?

A

caused by postganglionic neurons from the two divisions signalling onto the same target cells using different neurotransmitters

39
Q

What is the enteric nervous system?

A

division of VNS that coordinates sensory and motor functions of digestive organs, and can operate independently of CNS

40
Q

What are the two functions of visceral sensory neurons?

A
  • send information to CNS

- directly synapse on interneurons and effector neurons of ENS

41
Q

What do parasympathetic and sympathetic neurons synapse on?

A

parasympathetic and sympathetic divisions represent the CNS response to visceral sensory information, but mostly synapse onto ENS neurons, not effector cells

+ BIOL 371 (22 decks)

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