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Phisiology Hope > Nerve and Synapse > Flashcards

Nerve and Synapse Flashcards

1
Q

Communications and control network that allows an organism to interact in appropriate ways with its environment

A

Nervous System

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2
Q

o Central control hub of the nervous system

o Includes the brain and spinal cord

A

Central Nervous System

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3
Q

o Provides an interface between the environment and the central nervous system
o Includes sensory neurons, somatic motor neurons, and autonomic motor neurons

A

Peripheral Nervous System

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4
Q

Includes the following:
o Transmission of information via neural networks
o Transformation of information by recombination with other information (neural integration)
o Perception of sensory information
o Storage and retrieval of information (memory)
o Planning and implementation of motor commands
o Thought processes and conscious awareness
o Learning
o Emotion and motivation

A

Information Processing

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5
Q
  • Totality of an organism’s responses to its environment

* May be covertly or overtly expressed

A

Expression Of Behavior

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6
Q

Anatomically and physiologically specialized for communication and signaling

A

Neurons (Nerve Cells)

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7
Q

o Characterized as supportive cells that sustain neurons both metabolically and physically
o Maintain internal milieu of the nervous system

A

Neuroglia (Nerve Glue)

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8
Q

Types of Neuroglia

A
  1. MICROGLIA (Latent Macrophages)
    - Scavenger cells that resemble macrophages
    - Remove debris resulting from injury or disease
  2. MACROGLIA
    - Supportive matrix of the central nervous system
    - Protects neurons from extreme variations in their extracellular environment
  3. EPENDYMAL CELLS
    - Epithelial lining the ventricular spaces of the brain
    - CSF is secreted in large part by specialized ependymal cells of the choroid plexus
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9
Q

Types of Macroglia

A
  1. Central Nervous System
    O Astrocytes
    O Oligodendroglia
  2. Peripheral Nervous System
    O Schwann Cells
    O Satellite Cells
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10
Q
  • Star-shaped
  • Help regulate the CNS microenvironment
  • Foot processes form the blood-brain barrier
A

Astrocytes

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11
Q

Types of Astrocytes

A 
1. FIBROUS ASTROCYTES
o	Contain many intermediate filaments
o	Found in white matter
2. PROTOPLASMIC ASTROCYTES 
o	Found in gray matter
o	Granular cytoplasm
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12
Q
  • Involved in myelin formation around axons in the central nervous system
  • many central axons can be myelinated by a single oligodendrocyte
A

Oligodendrocytes

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13
Q
  • Involved in myelin formation around axons in the peripheral nervous system
  • Each Schwann cell myelinates only one axon
A

Schwann Cells

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14
Q

Importance of Myelination

A
  • Increases speed of action potential conduction
  • Restricts flow of ionic current to small unmyelinated portions of the axon between adjacent sheath cells (nodes of Rangier)
  • This process is called SALTATORY conduction
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15
Q
  • Encapsulate dorsal root and cranial nerve ganglion cells

* Regulate their microenvironment in a fashion similar to that used by astrocytes

A

Satellite Cells

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16
Q
  • Contains the nucleus of the nerve cell

* Metabolic and integrative center of the neuron

A

Cell Body (Soma)

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17
Q
  • Processes that extend outward from the cell body and arborize extensively (arbor vitae)
  • Small knobby projections (dendritic spines)
A

Dendrites

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18
Q
  • Long fibrous process that originates from a thickened area of the cell body (axon hillock)
  • Divides into presynaptic terminals, ending in synaptic knobs (aka terminal buttons or buttons)
  • Contain granules or vesicles which contain neurotransmitters
A

Axon

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19
Q

one process, with different segments serving as receptive surfaces and releasing terminals

A

Unipolar

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20
Q

have two specialized processes:

  • dendrite that carries information to the cell
  • axon that transmits information from the cell
A

Bipolar

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21
Q

a single process splits into two, both of which function as axons—one going to skin or muscle and another to the spinal cord

A

Pseudo-Unipolar

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22
Q

more than two specialized processes

A

Multipolar

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23
Q
  • Ability to respond to environmental changes called stimuli
  • Possessed by all cells
  • Highest degree of development of this property is seen in neurons
A

Excitability

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24
Q

• Any change in the environment that will influence an organism and cause a response

A

Stimulus

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25
Q
  • Type of energy transmitted by the stimulus
  • adequate stimulus is the particular form of energy to which a receptor is most sensitive
  • EXAMPLE: light for the rods and cones of the eye
A

Modality

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26
Q
  • Site on the body where the stimulus originated

* A single sensory axon and all its peripheral branches is called a sensory unit

A

Location

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27
Q

Is the spatial distribution from which a stimulus produces a response

A

Receptive Field

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28
Q

Sensation from receptors at the peripheral edge of the stimulus is inhibited compared to sensation from central receptors

A

Lateral Inhibition

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29
Q

Signaled by the response amplitude or frequency of action potential generation

A

Intensity

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30
Q

Magnitude of the sensation felt is proportional to the log of the intensity of the stimulus

A

Weber-Fechner Law

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31
Q
  • Time from start to end of a response in receptors
  • Receptors can be classified as:
    o Rapidly adapting (phasic) receptors
    o Slowly adapting (tonic) receptors
A

Duration

32
Q

At constant stimulation, frequency of the action potentials in sensory nerves decline over time

A

Adaptation or Desensitization

33
Q
  • For neurons, the curve clearly flattens out with long stimulus durations, reaching an asymptote
  • When the stimulus strength is below the rheobase, stimulation is ineffective even when stimulus duration is very long
A

Rheobase

34
Q

• Stimulus duration equal to twice the rheobase

A

Chronaxie

35
Q

The ____ the chronaxie, the more excitable a nerve is

A

Lower

36
Q
  • Once threshold intensity is reached, a full-fledged action potential is produced
  • Further increases in the intensity of a stimulus produce no increment or other change
  • Action potential fails to occur if the stimulus is subthreshold in magnitude
A

All-Or-None Principle

37
Q

• Junction that permits neurons to pass electrical or chemical signals to other cells
• Essential component to neuronal communication
o with other neurons
o with muscles
o with glands

A

Synapse

38
Q
  • Low-resistance pathway between cells
  • Direct flow of currents from one cell to another
  • Neurotransmission is multidirectional
A

Electrical Synapse

39
Q
  • Comprise almost all the synapses in the CNS used for signal transmission
  • Presynaptic neuron secretes neurotransmitters that act on postsynaptic cell
  • Neurotransmission is unidirectional
A

Chemical Synapse

40
Q

is the time required for the multiple steps in chemical neurotransmission

A

Synaptic Delay

41
Q

• Action potential in one presynaptic neuron produces an action potential in one postsynaptic cell
EXAMPLE: neuromuscular junction

A

One-To-One Synapse

42
Q

• Action potential in one presynaptic neuron produces an action potential in many postsynaptic cell
• Causes amplification of synaptic activity
EXAMPLE: motoneurons on Renshaw Cells

A

One-To-Many Synapse

43
Q

• Multiple presynaptic neurons are required to depolarize one postsynaptic cell and produce an action potential
EXAMPLE: widespread in CNS/PNS

A

Many-To-One Synapse

44
Q

Small-molecule endogenous chemicals that transmit signals from a neuron to a target cell across a synapse

A

Neurotransmitter

45
Q

Essential Characteristics of Neurotransmitters

A
  • Have precursors and/or synthesis enzymes located in the presynaptic neuron
  • Present in the presynaptic neuron
  • Available in sufficient quantity affect postsynaptic cells
  • Capable of binding to postsynaptic receptors
  • Biochemical mechanism for inactivation
46
Q

• Secreted by neurons in many areas:
o Large pyramidal cells in motor cortex
o Basal ganglia (nucleus basalis)
o Skeletal muscles
o All preganglionic neurons of ANS
o Postganglionic neurons of parasympathetic NS
o Some postganglionic neurons of sympathetic NS
• May be excitatory or inhibitory
• Action terminated by metabolism (enzymatic degradation) by acetylcholinesterase

A

Acetylcholine

47
Q

• Secreted by many neurons:
o Brain stem
o Hypothalamus
o locus ceruleus in the pons
o Postganglionic neurons of sympathetic nervous system
• Control overall activity and mood of the mind, such as increasing the level of wakefulness
• May be excitatory or inhibitory
• Action terminated by repute (NET) and metabolism (monoamine oxidase, catechol-O-methyltransferase)

A

Norepinephrine and Epinephrine

48
Q
  • Secreted by neurons in the substantial nigra
  • May be excitatory or inhibitory
  • Action terminated by reuptake (DAT) and metabolism (monoamine oxidase, catechol-O-methyltransferase)
A

Dopamine

49
Q
  • Secreted mainly at synapses in the spinal cord (Renshaw cells)
  • Always acts as an inhibitory transmitter
A

Glycine

50
Q 
• Secreted by nerve terminals:
o	Spinal cord
o	Cerebellum
o	Basal ganglia
• Many areas of the cerebral cortex
• Always acts as an inhibitory transmitter
A

Gamma-AminoButyric Acid (GABA)

51
Q

• Secreted by:
o Presynaptic terminals in many of the sensory pathways
o Many areas of the cerebral cortex
o Always an excitatory neurotransmitter
• Most prevalent excitatory neurotransmitter in brain

A

Glutamate

52
Q
  • Secreted by nuclei from median raphe of brain stem
  • Inhibitory neurotransmitter
  • Controls mood and sleep
A

Serotonin

53
Q
  • Secreted in areas of the brain responsible for long-term behavior and memory
  • Short-acting inhibitory neurotransmitter
A

Nitric Oxide

54
Q

Which neurotransmitter is purely excitatory?

A

Glutamate

55
Q

Which neurotransmitters are purely inhibitory?

A

Serotonin, Glycine, GABA, Nitric Oxide

56
Q

Which neurotransmitters are may be excitatory or inhibitory?

A

Acetylcholine, Norepinephrine, Epinephrine, Dopamine

57
Q

o Inputs that depolarize the postsynaptic cell, bringing it closer to threshold and closer to firing an action potential
o Caused by opening of Na+ and K+ channels

A

Excitatory Postsynaptic Potentials (EPSP)

58
Q

o Inputs that hyperpolarize the postsynaptic cell, moving it away from threshold and farther from firing
o Caused by opening Ca+ channels

A

Inhibitory Postsynaptic Potentials (IPSP)

59
Q

Process of adding up postsynaptic potentials and responding to their net effect

A

Summation

60
Q

♣ Occurs when two EPSPs arrive at a postsynaptic neuron simultaneously
♣ Together, they produce greater depolarization

A

Spatial Summation

61
Q

♣ Occurs when EPSPs arrive at a postsynaptic neuron in rapid succession
♣ EPSPs overlap in time, adding in stepwise fashion

A

Temporal Summation

62
Q
  • Process where one neuron enhances the effect of another neuron
  • EPSPs bring membrane potential nearer threshold potential, but not yet at firing level
A

Presynaptic Facilitation

63
Q
  • Opposite of facilitation
  • Mechanism in which one presynaptic neuron suppresses another one
  • IPSPs bring membrane potential farther from threshold potential
A

Presynaptic Inhibition

64
Q
  • Bringing additional neurons into play as the stimulus becomes stronger
  • Enables the nervous system to judge stimulus strength by which neurons, and how many of them, are firing
A

Recruitment

65
Q
  • Neurons may function in larger ensembles called neuronal pools or neural networks
  • Thousands to millions of interneurons concerned with a particular body function
  • EXAMPLES: neuronal pools for rhythm of your breathing
A

Neuronal Pools

66
Q

• Within the discharge zone of an input neuron, an input neuron acting alone can make the postsynaptic cells fire

A

Discharge Zone

67
Q
  • Within the broad facilitated zone, a presynaptic input neuron synapses with other neurons in the pool
  • Can stimulate neurons to fire only with the assistance of other input neurons
A

Facilitated Zone

68
Q

• Neurons are in the subliminal fringe if:
o they are not discharged by an afferent volley (not in the discharge zone)
o they have their excitability increased

A

Subliminal Fringe

69
Q
  • Decrease in expected response

* Occurs due to presynaptic fibers sharing postsynaptic neurons

A

Occlusion

70
Q

• Signals from multiple inputs unite to excite a single neuron

A

Convergence

71
Q

• Input from just one neuron may produce output through dozens of neurons

A

Divergence

72
Q

o An input signal spreads to an increasing number of neurons as it passes through successive orders of neurons in its path
o EXAMPLE: corticospinal tract

A

Amplifying Divergence

73
Q

o Signal is transmitted in two directions from the neuronal pool
o EXAMPLE]: dorsal columns, thalamic pathways

A

Divergence Into Multiple Tracts

74
Q

• Also known as close-chain or oscillatory circuit

A

Reverberation

75
Q
  • One input neuron diverges to stimulate several chains of neurons
  • Each chain has a different synapses but eventually reconverges on one output neuron
A

Parallel-After-Discharge

Phisiology Hope (7 decks)

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