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PHARM 110 > 7 - Intro to Nervous System > Flashcards

7 - Intro to Nervous System Flashcards

1
Q

What are the 2 principle parts of the Nervous system?

A
  • Central nervous system (CNS)
    • Brain & spinal cord of dorsal body cavity
    • Integrating & control centre
  • Peripheral nervous system (PNS)
    • The portion of nervous system outside CNS
    • spinal nerves and cranial nerves
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2
Q

What are the 2 main cell types?

A
  • neurons
  • neuroglia
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3
Q

What are the Neuroglia cells in the CNS?

A
  • Astrocytes
  • Microglia
  • Ependymal cells
  • Oligodendrocytes
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4
Q

What are the Neuroglia cells in the PNS?

A
  • Satellite cells
  • Schwann cells
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5
Q

What are Astrocytes?

A
  • Star shaped cells found in CNS & spinal cord
  • Most abundant cell of the human brain
  • Guide the migration of young neurons & formation of synapses
  • Help determine capillary permeability
  • Control chemical environment (uptake/recycling) NTs & ions
  • Have gap junctions for communication b/w astrocytes (Ca2+ pulses)
  • Important in memory
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6
Q

What are microglia?

A
  • Small, ovoid cells w/ thorny processes
  • Migrate towards injured neurons
  • Phagocytize microorganisms & neuronal debris
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7
Q

What are ependymal cells?

A
  • Range in shape from squamous to columnar
  • Circulate in & produce CSF
  • Line central ventricular cavities of brain & spinal column
  • Separate the CNS interstitial fluid from CSF
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8
Q

What are Oligodendrocytes?

A
  • One cell can produce processes that wrap up to 60 axons
  • Forming insulating myelin sheaths
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9
Q

What are Satellite Glial Cells?

A
  • Surround neuron cell bodies in ganglia of PNS
  • Control microenvmt around neuron cell body
  • Similar to astrocytes of CNS
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10
Q

What are Schwann cells?

A
  • Most form myelin sheaths around axons
  • Vital for function, maintenance & regeneration of damaged nerve fibers
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11
Q

What does a Myelin Sheath do?

A
  • Protect & electrically insulate axon
  • Increase speed of nerve impulse transmission
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12
Q

What makes up Myelin sheath in PNS?

A
  • Schwann cells – wraps many times around axon
  • Neurilemma – peripheral bulge of schwann cell cytoplasm
  • Nodes of Ranvier – myelin sheath gaps b/w adjacent schwann cells
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13
Q

What makes up Myelin sheath in CNS?

A
  • Formed by processes of oligodendrocytes
  • Nodes of Ranvier
  • No neurilemma
  • Thinnest fibers (axons) are unmyelinated
  • 1 oligodendrocyte can wrap around up to 60 axons
  • Give rise to white matter
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14
Q

What are Neurons?

& what are their special characteristics

A
  • nerve cells, are structural units of nervous system
  • cells that conduct impulses

Special characteristics:
* Extreme longevity (last person’s lifetime)
* Amitotic – non-dividing, don’t regenerate
* High metabolic rate – requires continuous supply of oxygen & glucose
* All have cell body & one or more processes

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15
Q

What do Neuronal Cell Bodies do?

A
  • Synthesizes proteins, membranes, chemicals
  • Rough ER (chromatophilic substance or nissl bodies

Clusters of cell bodies are called:
* Nuclei in CNS
* Ganglia in PNS

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16
Q

Bundles of Neuron processes are called? CNS vs. PNS?

A
  • Tracts in CNS
  • Nerves in PNS
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17
Q

What are Dendrites?

A
  • Receptive (input) region of neuron
  • Convey incoming messages toward cell body as graded potentials
  • Contain dendritic spines – appendages w/ bulbous or spikey ends
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18
Q

What are Axons? What are the 3 parts?

A
  • Axon hillock, Axolemma, Axoplasm
  • Each neuron has 1 axon (conducting region) that starts at axon hillock
  • Long axons are called nerve fibers
  • Branches are called axon collaterals
  • Axons branch profusely at their end
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19
Q

What are the 3 Structure types of neurons?

A
  1. Multipolar - 3 or more processes w/ 1 axon and rest dendrites
  2. Bipolar – 2 processes w/ 1 axon + 1 dendrite (rare), found in retina and olfactory mucosa
  3. Unipolar (pseudounipolar) - single short processes that has 2 branches
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20
Q

What are the 3 Functional types of Neurons?

A
  1. Sensory (afferent) - transmit impulses from sensory receptors toward CNS
  2. Interneurons (association neurons) - shuttle signals through CNS pathways, most within CNS
  3. Motor (efferent) - carry impulses from CNS to effectors
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21
Q

What is white matter?

A
  • dense collections of myelinated fibers
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22
Q

What is gray matter?

A
  • mostly neuronal cell bodies & unmyelinated fibers
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23
Q

Neurons & membrane potentials

A
  • Like all cells, neurons have a resting membrane potential
  • Unlike most other cells, neurons can rapidly change resting membrane potential
  • Neurons are highly excitable
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24
Q

What is Ohm’s law

A
  • (I) = V/R
  • current directly proportional to voltage
  • Resistance inversely proportional to voltage
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25
Q

2 Main types of ion channels

A
  • Leakage (nongated) channels - always open
  • Gated channels - in which part of the protein changes shape to open/close channel
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26
Q

What are the 3 types of Gated channels

A
  • chemically gated, voltage-gated, mechanically gated
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27
Q

What Factors influence Resting Membrane Potential

A
  • Impermeable to negatively charged proteins
  • Slightly permeable to Na+ (Na+ leakage channels)
  • 25-100 times more permeable to K+ (K+ leakage channels)
  • Freely permeable to Cl-
  • Differences in ionic composition of ICF & ECF
  • Differences in plasma membrane permeability
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28
Q

What generates the Resting Membrane Potential?

A
  • Na/K pumps more cations out
  • [ ] gradient of K
  • higher permeability of K
  • membrane impermeable to anionic proteins
  • chemical gradient + electrical gradient
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29
Q

Membrane potential changes when…

A
  • [ ] s of ions across membrane change
  • Membrane permeability to ions changes
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30
Q

What are the 2 types of signals produced by changes in membrane potential?

A
  • Graded potentials
    • Incoming signals operating over short distances
  • Action potentials
    • Long-distance signals of axons
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31
Q

What is Depolarization?

A
  • Reduction in membrane potential
  • Going more +ve
  • Inside of membrane becomes less negative than resting potential
  • Increase probability of producing a nerve impulse
32
Q

What is Hyperpolarization?

A
  • Increase in membrane potential
  • Going more –ve
  • Inside of membrane becomes more negative than resting potential
  • Decrease probability of producing a nerve impulse
33
Q

What are graded potentials?

A
  • Short-lived localized changes in membrane potential
  • stronger the stimulus, the more voltage changes & farther current flows
  • Triggered by stimulus that opens gated ion channels
  • Results in depolarization or hyperpolarization
34
Q

What are the types of graded potentials?

according to location & function

A
  • Receptor potential (generator potential) - graded potentials in receptors of sensory neurons excited by some form of energy (heat, light or other)
  • Postsynaptic potential - neuron graded potential
35
Q

What are Action Potentials?

A
  • Principal way neurons send signals
  • long-distance neural communication
  • primarily in muscle cells & axons of neurons
  • Action potentials (APs) do not decay over distance
  • AKA nerve impulse
36
Q

Describe Voltage gated Na+ channels

A
  • have 2 gates, alternate b/w 3 different states
  • Activation gates - closed at rest, open w/ depol, allowing Na+ to enter cell
  • Inactivation gates - open at rest, block channel once it is open, prevent more Na+ from entering cell
  • closed - at rest
  • open - opened by depol
  • inactivated - blocked by inactivation gates soon after they open
37
Q

Describe Voltage gated K+ channels

A
  • have 1 gate & 2 states
  • Closed at rest
  • Opens slowly w/ depol
38
Q

What is the absolute refractory period?

A
  • Time from opening of voltage-gates Na+ channels until resetting of channels (involved opening the inactivation gate)
  • Time where you can’t generate any APs
  • Ensures that each AP is an all-or-none
  • Enforces 1-way transmission of nerve impulses
39
Q

What is the Relative refractory period?

A
  • Most voltage-gated Na+ channels have returned to resting state
  • Some voltage-gate K+ channels are still open
  • During hyperpolarization
  • Threshold required for initiating an AP generation is elevated
  • Need higher potential to initiate AP during relative refractory period
40
Q

Explain Threshold & all-or-none response

A
  • Not all depolarization events produce APs
  • depolarization must reach threshold voltage to trigger AP
  • All-or-none – an AP either happens completely or does not happen at all
  • Size of AP doesn’t change depending on strength of stimulus
41
Q

Describe the Propagation of an AP

A
  • AP to be transmitted from origin down entire axon length toward terminals
  • local currents that cause opening of Na+ voltage gates in adjacent membrane areas
  • Once initiated, an AP is self-propagating
  • AP occurs only in forward direction
42
Q

How does stimulus intensity affect APs?

A
  • All APs are alike & are independent of stimulus intensity
  • Strong stimuli - can generate APs more often than weaker stimuli
43
Q

What increase Conduction Velocity of neurons?

A
  • larger diameter fibers - less resistance to current flow, faster impulse conduction
  • myelination - insulate & prevent leakage of charge
44
Q

What is Saltatory Conduction?

A
  • Voltage-gates Na+ channels located at nodes of Ranvier
  • APs jump rapidly from node to node (30X faster than non-myelinated)
45
Q

What are the 3 nerve fiber classifications?

A

Group A fibers = 150 m/s fastest
* Large diameter, myelinated
* somatic sensory & motor fibers

Group B fibers = 15 m/s
* Intermediate diameter, lightly myelinated
* ANS motor fibers serving visceral organs & smaller somatic sensory fibers from skin (pain & touch)

Group C fibers = 1 m/s slowest
* Smallest diameter, unmyelinated
* some ANS motor fibers serving visceral organs & smaller somatic sensory fibers from skin (pain & touch)

46
Q

What is Multiple Sclerosis?

A
  • autoimmune disease that affects primarily young adults
  • immune system attacks myelin - Myelin sheaths in CNS are destroyed
  • Turns myelin into hardened lesions called scleroses
  • Impulse conduction slows & eventually ceases
  • Demyelinated axons increase Na+ channels, causing cycles of relapse & remission
47
Q

What is a synapse?

A
  • A junction that mediates info transfer from 1 neuron to another neuron or an effector cell
  • Presynaptic neuron - conducts impulses toward synapse
  • Postsynaptic neuron - transmit impulses away from synapse
48
Q

What are Chemical synapses?

A
  • most common
  • release & reception of chemical neurotransmitters
  • Axon terminal of presynaptic neuron – contains synaptic vesicles filled w/ NTs
  • Receptor region on postsynaptic neuron’s membrane – receives NT’s
  • Electrical (synapse) -> chemical (synaptic cleft) -> electrical (synapse)
49
Q

What is synaptic delay?

A
  • NT must be released, diffuse across synapse, & bind to receptors
  • Synaptic delay (0.3-0.5 ms)
  • synaptic delay is rate-limiting step of neural transmission
50
Q

What are Electrical Synapses?

A
  • Less common than chemical synapses
  • In embryonic development
  • Neurons are electrically coupled (gap junctions)
  • Communication is very rapid
  • May be unidirectional or bidirectional
  • Are important in stereotyped movements
51
Q

Postsynaptic potential strengths are determined by?

A
  • amount of NT released
  • Time NT is in area
52
Q

2 types of postsynaptic potentials

A
  • EPSP – excitatory postsynaptic potential
  • IPSP – inhibitory postsynaptic potentials
53
Q

Excitatory synapses & EPSP

A
  • NT binds chemically gated channels that allow simultaneous flow of Na+ & K+ in opposite directions
  • Na+ influx > K+ efflux (causes net depolarization)
  • EPSP helps trigger AP at axon hillock
54
Q

Inhibitory synapses & IPSPs

A
  • NT opens chemical gated channels for either K+ or Cl-
  • Causes hyperpolarization
  • Reduces postsynaptic neuron’s ability to produce an AP
55
Q

What is synaptic potentiation?

A
  • Repeated use increases efficiency of neurotransmission (long-term potentiation)
  • Ca2+ concentration increases in presynaptic terminal & postsynaptic neuron
56
Q

What is Presynaptic inhibition?

A
  • Release of excitatory NT by one neuron may be inhibited by activity of another neuron via an axoaxonic synapse
  • Block axon from releasing NTs before even getting response into synaptic cleft -> presynaptic inhibition
  • Less NT is released & smaller EPSPs are formed
57
Q

What are the NT classes?

A
  • Acetylcholine
  • Biogenic Amines (aka monoamines)
  • Amino acids
  • Peptides (neuropeptides)
  • Purines
  • Gases & liquids
58
Q

What is Acetylcholine?

A
  • Synthesized from choline & acetyl CoA by choline acetyltransferase (ChAT) & degraded by acetylcholinesterase
  • Released at neuromuscular junctions, some ANS neurons, and some CNS neurons
  • Nicotinic receptors (N) excitatory - on skeletal muscle, ANS ganglia & CNS
  • Muscarinic receptors (M) can be inhibitory or excitatory – on visceral effectors & in CNS
59
Q

What are Biogenic Amines?

A
  • Aka monoamines
  • Drug class: monoamine oxidase inhibitor (MOAI)
  • Derived from single amino acids
  • Play roles in emotional behaviors & biological clock

3 classes:
* Catecholamines (dopamine, norepinephrine, epinephrine)
* Indolamines (serotonin or 5HT)
* Imidazoleamine (histamine)

60
Q

Dopamine

A
  • inhibitory or excitator
  • Released by substantia nigra & hypothalamus
  • Important for motor pathways, motivation, reward & reinforcement
  • Tyrosine precursor
60
Q

NE & Epinephrine

A
  • inhibitory or excitatory
  • Released from locus coeruleus, limbic system, cerebral corte, postganglionic neurons in SNS & adrenal Medulla
  • Involved in mood, sleep, wakefulness, attention, feeding behaviour & SNS
  • Tyrosine -> dopamine -> NE -> E precuror
61
Q

Serotonin

A
  • mainly inhibitory
  • Brain & spinal cord
  • Role in sleep, appetite, nausea, migraine headaches, mood & digestion
  • Tryptophan precursor
62
Q

Histamine

A
  • Hypothalamus
  • Involved in wakefulness, appetite control, learning & memory, gastric secretions, in CT mediates inflammation & vasodilation
  • Histidine precursor
63
Q

What are Amino acids?

A
  • GABA – inhibitory
    • Principle inhibitory NTs in brain
    • Important for axoaxonal presynaptic inhibition
  • Glycine – inhibitory
    • Principal inhibitory NT in spinal cord
  • Glutamate – excitatory
    • Principal excitatory NT
    • Important in learning & memory
  • Aspartate – excitatory NT in some brain regions
64
Q

What are Neuropeptides?

A
  • Tachykinins – excitatory
    • Substance P, neurokinin A
    • PNS = mediator of pain signals
    • CNS = respirator & cardiovascular controls & mood
    • Also released by enteric neurons
  • Endorphins – inhibitory
    • Act as natural opiates
    • Reduce pain perception
    • Inhibits substance P
  • Cholecystokinin (CCK) - excitatory
    • Found in CNS & released by small intestines to encourage digestion
    • Involved in anxiety, pain, memory inhibit appetite
  • Somatostatin – inhibitory
    • Found in CNS & released by pancreas, stomach & intestines to slow down/inhibit digestion
65
Q

What are Gastrotransmitters?

A
  • Synthesized on demand
  • Diffuse out of cells that make them (lipid soluble)
  • Travel into target cell to bind to intracellular receptors
  • Nitric oxide (NO) - inhibitory or excitatory
    • Involved in learning & memory
    • Smooth muscle relaxation
  • Carbon monoxide (CO) - inhibitory or excitatory
65
Q

What are purines?

A
  • Act in both CNS & PNS to produce fast or slow response
  • ATP – inhibitory or excitatory
    • Released by sensory neurons
    • Provokes pain sensation
  • Adenosine – inhibitory
    • Potent inhibitor in brain
    • Caffeine stimulates by blocking brain adenosine receptors
    • Also cause vasodilation to increase blood flow to heart & other tissues as needed
66
Q

What are lipids?

A
  • Endocannabinoids – inhibitory
    • Synthesized on demand from membrane lipids
    • Receptors also activate by THC
    • Involved in memory as a retrograde messenger to decrease NT release
    • Involved in controlling appetite, suppressing nausea & vomitting & neuronal development
67
Q

What are Channel-linked receptors

A
  • Ligand-gated ion channels
  • Actions is immediate & brief (direct action)
  • Excitatory receptors – channels for small cations (Na+ influx contributes most to depolarization)
  • Inhibitory receptors – allow Cl- influx or K+ efflux that causes hyperpolarization
  • Ex. Ach & AAs
68
Q

What are G Protein-linked recpetors?

A
  • Have indirect action
  • NT binds to G protein-linked receptor & acts through intracellular 2nd messenger
  • Responses are indirect, slow, complex & often prolonged/widespread
  • Ex. Biogenic amines, neuropeptides, cannabinoids, & gases
69
Q

What are neuronal pools?

A
  • Neuronal pools – functional groups of neurons that:
  • Integrate incoming info
  • Forward processed info to other destinations
70
Q

What is a Diverging circuit?

A
  • 1 input, many outputs
  • Amplifying circuit
  • Ex. single neuron can activate 100 or more motor neurons in spinal cord, & thousands of muscle fibers
71
Q

What is a converging circuit?

A
  • Many inputs, 1 output
  • Concentrating circuit
  • Common in sensory & motor systems
  • Ex. Diff stimuli can elicit same memory
72
Q

What is a reverberating/oscillating circuit?

A
  • Chain of neurons containing collateral synapses w/ previous neurons
  • Sleep-wake cycles, breathing, repetitive motor patterns
73
Q

What is Parellel after discharge circuit?

A
  • Signal stimulates neurons arranged in parallel arrays that eventually converge on single output
  • Impulses reach output cell at diff times causes a burst of impulses
  • Involved in complex types of mental processing
  • Ex. Mathematics
74
Q

What is Serial processing?

A
  • Input travels along one pathway to specific destination
  • Works in all or none manner to produce specific response
  • Ex. Simple spinal reflexes
75
Q

What is Parallel processing?

A
  • Input travels along several pathways
  • 1 stimulus promotes numerous responses
  • Important for higher-level mental functioning
  • Ex. Step on sharp object – serial processed to withdraw foot, parallel processing of higher order (rub foot & seek help)

PHARM 110 (12 decks)

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