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pays exam 2 > chapter 7 > Flashcards

chapter 7 Flashcards

1
Q

function and division of the nervous system

A

Regulate and control other systems of the body by communicating through electrochemical impulses

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2
Q

neuron

A

respond to stimuli, conduct electrical activity (action potential), release chemical regulators

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3
Q

structural classes of neurons is based on

A

of processes

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4
Q

glial cells of the CNS (3 things)

A
  • Constitute about half of the cells in the CNS
  • Can divide by mitosis unlike neurons
  • Provide physical and metabolic support
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5
Q

4 types of glial cells

A
  • Microglia=immune function
  • Ependymal cells=regulate reproduction of cerebrospinal fluid
  • Oligodendrocyte
  • Astrocytes
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6
Q

Oligodendrocytes

A
  • type of glial cell in CNS
  • Insulates and covers axon
  • Forms myelin sheaths which speed up conduction (function) of electrical signals along axon
  • -Myelin forming cells called Oligodendrocytes in CNS, Schwann cells in the PNS
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7
Q

Myelin forming cells called ______ in CNS, ______ in the PNS

A

Oligodendrocytes; Schwann cells

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8
Q

Astrocytes

A
  • type of glial cell in CNS
  • Most abundant
  • Regulates extracellular fluid and stimulates the formation of blood brain barrier among other duties
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9
Q

Microglia

A
  • type of glial cell in CNS

- immune function

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10
Q

Ependymal Cells

A
  • type of glial cell in CNS

- regulate production of cerebrospinal fluid

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11
Q

membrane potential recap

A
  • Neurons have a resting potential of -70mV.
  • -Established by large negative molecules inside the cell
  • -Na+/K+ pumps
  • -Permeability of the membrane
  • At rest, there is a high concentration of K+ inside the cell and Na+ outside the cell.
  • Ions constantly move to maintain the concentration gradients
  • ->Na+, K+, Cl-, Ca2+
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12
Q

Ligand gated (channel in the membrane)

A

opening in response to binding of a chemical ligand to its receptors (signaling molecules)
–>ACh

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13
Q

Mechanical gated (channel in the membrane)

A

open when physical deformation to membrane occurs (like stretching)
–>Skin

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14
Q

Voltage gated (channel in the membrane)

A

protein channel when stimulated depolarizes membrane to threshold, specific to an ion; ability to undergo action potential meaning depolarizing membrane to threshold, specific to an ion

-open at certain membrane potentials and close at other

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15
Q

changes in membrane potential are controlled by what

A

changes in the flow of ions through channels

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16
Q

Voltage gated K+ channels

A
  • Open at +30mv (stimulus point)
  • Slower to open and to close
  • opens 2nd (compared to Na+ channels)
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17
Q

Voltage gated Na+ channels

A
  • Open at negative values
  • Respond faster at threshold (-55mV)
  • Inactivate at +30mV, breaking positive feedback loop (closing up)
  • opens 1st (compared to K+ channels)
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18
Q

similarity between voltage gated K+ channel and Voltage gated Na+ channel

A

closed at resting potential

19
Q

When threshold is reached what happens

A

action potential fires

–once hit this point stimulus strength doesn’t matter

20
Q

Strength affects _______ of Action Potential and may recruit more neurons to have AP

A

frequency, NOT amplitude

21
Q

depolarization deals w

A

sodium (Na)

22
Q

repolarization deals w

A

potassium (K)

23
Q

Action potentials characteristics

A
  • primary mechanism used to communicate over large distances
  • Voltage-gated channels for both Na+ and K+, which will change the concentrations
  • Apply to neurons and muscular cells
  • All or none Law: full action potential, threshold to +30mV
  • Large, Fast change in the membrane potential: -70 to +30mV in approx. 3 msec
24
Q

Action potential

A

all or nothing electrical event in a single cell where the membrane potential quickly becomes positive and returns to resting potential ??

25
Q

Action potential; absolute refractory periods

A

A second stimulus will not produce an action potential

why??

  • Na+ channels are inactivated
  • As soon as inactivation is removed and Na+ are closed the channel can reopen to second stimulus
26
Q

Action potential; Relative refractory period

A

second action potential can happen only if stimulus strength is greater than usual

Why can it occur here?

  • Some K+ channels still open
  • Magnitude of the potential will be reduced
27
Q

Action potential conduction

A
  • The depolarization of the first AP is the stimulus for the new action potential in the region just ahead of it and so on…
  • Each AP is its own separate event and thus said to be regenerated

-However: Positive feedback of Na+ allows the action potential to travel without decrement (decrease) thus reaching the end with the same amplitude

28
Q

Saltatory Conduction

A
  • Myelin prevents Na+ and K+ from moving through the membrane-can’t get out!
  • AP move faster due to ‘leaping from node to node’ compared to ion channels located ALL along the axon
29
Q

unmyelinated

A

The conduction rate is slow because so many action potentials are generated, each one an individual event.

30
Q

myelinated

A

More charge arrives at nodes due to myelin insulation preventing charge to leak out, therefore AP moves faster.

-Due to ions pumping only at the nodes and restoring fewer ions, This creates less work for the pumps saving energy!

31
Q

Synapse characteristics

A

Synapses can use both chemical and electrical stimuli to pass information.

Synapses can be inhibitory or excitatory depending on the neurotransmitter (chemical signal) being transmitted.

Synapses occur between neurons and in the PNS the target muscle or gland

32
Q

synapses using electrical stimuli

A
  • Pre- and post-synaptic cells are connected by gap junctions
  • Current flow continues quickly across the gaps
  • Found in cardiac, smooth muscle to allow contraction as a unit to occur
  • either direction !!
33
Q

Synapses using chemical stimuli (the majority )

A
  • Axon terminals hold synaptic vesicles
  • Pre-synaptic neurons release neurotransmitter
  • Neurotransmitter is a chemical messenger that travels across the synaptic cleft and binds to receptors on post-synaptic neurons
  • one way !!
  • example: ACh
34
Q

mechanisms of neurotransmitter release

A

Calcium Ions trigger a change in the SNARE proteins that lead to the fusion & release of the neurotransmitter

  1. action potentials reach axon terminals
  2. voltage gated Ca2+ channels open
  3. Ca2+ binds to sensor protein in cytoplasm
  4. Ca2+ protein complex stimulates fusion and exocytosis of neurotransmitters
35
Q

SNARE proteins loosely dock vesicles

A

The vesicle needs to be released from where it is held at, fuse to the membrane, and release out the neurotransmitter from the vesicle (this is where we have drug interference)
We have completed the process of an action potential leaving the presynaptic cell

36
Q

At the post synapse

A

Neurotransmitters come in large amounts to ensure binding to a post synaptic receptor, unused are transported away from the site

37
Q

Postsynaptic response: Excitatory

A

-Opening Na+ or Ca2+ channels results in a graded depolarization called an excitatory postsynaptic potential (EPSP)
-Brings postsynaptic membrane closer to threshold (Depolarizing).
is a graded potential

38
Q

Postsynaptic response:: Inhibitory

A
  • Opening K+ or Cl-channels results in a graded hyperpolarization called inhibitory postsynaptic potential (PSP)
  • Brings postsynaptic membrane further from threshold (Hyperpolarizing)
  • Decreasing the likelihood of an action potential
39
Q

EPSP & IPSP are what kind of potentials

A

graded potentials

  • amplitude decreases as signal moves toward axon hillock.
  • Action potentials can begin at the hillock due to high amt of Na+ and K+ channels
40
Q

Characteristics of graded potentials

A
  • summation and lack of a refractory period

- graded potentials may lead to action potentials

41
Q

Nicotinic ACh receptors

A

-Ach binds at post synaptic cell, ex. skeletal muscle cells (how muscles contract)

  • Agonist: nicotine
  • Antagonist: curare
  • Binding of 2 acetylcholine molecules opens a channel
  • ->Due to electrochemical gradient, more Na+ flows in than K+ out, EPSP is begun
42
Q

Muscarinic ACh receptors

A

-Ach binds at post synaptic cell, ex. digestive cells or cardio cells

  • Agonist: muscarine
  • Antagonist: atropine

-Binding at the receptor opens ion channels indirectly by using a G-protein.
Dopamine and norepinephrine receptors do this too!

43
Q

what are Enogenous opioids and what do they do

A
  • polypeptides produced by the brain and pituitary gland
  • Opioids bind to Opioid receptors
  • -Receptors activated by stress and block the transmission of pain
  • -Drugs such as opium and morphine fit these same receptors, resulting in pain relief.

what do they do?
-Opioids also produce euphoria so they may mediate reward pathways; for example release of endorphins (named from the polypeptide: β-endorphins)

44
Q

examples of opioids

A

oxycodone, fentanyl, hydrocodone, heroine

pays exam 2 (6 decks)

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