Ch 7 Flashcards

Question

Schwann Cells

Answer 1

PNS neuroganglia | form myelin sheaths around peripheral axons

Answer 2

PNS neuroganglia support cell bodies within the ganglia of PNS -ex. secreting growth factors

Answer 3

CNS neuroganglia form myelin sheaths around the axons of CNS neurons -analogous to schwann cells

Answer 4

CNS neuroganglia | migrate around CNS tissue and phagocytize foreign and degenerated material

Answer 5

CNS neuroganglia regulate the external environment of the neurons -regulate tight junctions to regulate material movement in endothelial cells --> create BBB

Answer 6

CNS neuroganglia | line the ventricles and secrete cerebrospinal fluid

Answer 7

- capillaries in the brain do not have pores between adjacent cells but are joined by tight junctions - substances can only be moved by very selective processes of diffusion through endothelial cells, active transport, and bulk transport - movement is transcellular, not paracellular - astrocytes: support cell bodies/regulate formation of BBB

Answer 8

neurons have a resting potential of -70mV - established by large negative molecules inside the cell - Na+/K+ pumps - permeability of the membrane to positively charged, inorganic ions --> at rest there is a high concentration of K+ inside the cell and Na+ on the outside

Answer 9

occurs when positive ions enter the cell (usually Na+) - -> membrane potential moves towards 0/more positive - EXCITATORY

Answer 10

occurs when positive ions leave the cell (usually K+) | -INHIBITORY

Answer 11

Two types of channels 1. K+ leakage channels: not gated (always open), increases permeability to K 2. Voltage-gated K+ channel: open when a particular membrane potential is reached, closed at resting potential -Na+ voltage-gated channels are closed at rest, the membrane is less permeable to Na+ at rest

Answer 12

- -> these channels open if the membrane potential depolarizes to -55mV (a.k.a. threshold) 1. Channels open --> sodium rushes in due to electrochemical gradient 2. Membrane potential increases toward Na+ equilibrium potential 3. Channels deactivated at +30mV 4. Voltage-Gated K+ Channels open and K+ rushes out of cell following electrochemical gradient 5. This makes the cell depolarize back toward K+ equilibrium potential

Answer 13

1. At threshold membrane potential (-55mV), voltage-gated Na+ channels open and Na+ rushes in 2. As cell depolarizes, more Na+ channels are open, and the cell becomes more and more permeable to Na+ - POSITIVE feedback loop - causes an overshoot of membrane potential --> reaches +30mV 3. At +30mV, Na+ channels close and K+ channels open - results in repolarization of membrane potential - NEGATIVE feedback loop

Answer 14

-threshold is reached --> action potential occurs - size of stimulus will NOT: 1. affect size of action potential (will always reach +30mV - may recruit more neurons) 2. affect action potential duration, but will make them happen more frequently

Answer 15

action potentials can only increase in freq to a certain point - there is a refractory period after action potential when neuron can NOT become excited again (for milliseconds) - absolute vs. refractory periods - each action potential remains a separate, all-or-none event

Answer 16

occurs during the action potentials | -Na+ channels are inactive (not just closed)

Answer 17

- K+ channels are still open (still in hyper polarization phase) - only a very strong stimulus can overcome this

Answer 18

- action potential occurs at neuron membrane - voltage gated Na channels open as a wave down the axon - axon potential at one location serves as depolarization stimulus for next region of axon

Answer 19

* chaotic/unorganized - axon potentials produced down entire length of axon - slow conduction rate b/c so many action potentials are generated - amplitude of each action potential is the same (conducted w/o reduction)

Answer 20

* much more organized - myelin = insulation - Nodes of Ranvier allow Na and K to cross membrane every 1-2mm - -> Na ion channels concentrated at the nodes - action potentials "leap" from node to node - --> called "saltatory conduction"

Answer 21

1. diameter: reduces resistance to spread of charges via cable properties 2. Myelination b/c of saltatory conduction - -> thin unmyelinated= 1 m/sec - -> thick myelinated= 100 m/sec

Answer 22

- ->the functional connection between a neuron and the cell it's signaling * electrical or chemical 1. in CNS, second cell = another neuron 2. in PNS, second cell= muscle/gland (neuromuscular junction)

Answer 23

- can occur in mostly in smooth/cardiac muscle, between neurons of brain or glial cells - cells joined by gap junctions - stimulation causes phosphorylation or dephosporylation of connexion proteins to open or close the channels

Answer 24

- most involve the release of a neurotransmitter from axon terminal - synaptic cleft: very small, released neurotransmitter can readily diffuse across this space

Answer 25

Neurotransmitter is enclosed in synaptic vesicles in the axon terminal 1. when action potential reaches the end of the axon --> voltage gated Ca channels open 2. Ca stimulates the fusing of synaptic vesicles to the plasma membrane and exocytosis of neurotransmitter

Answer 26

Neurotransmitter diffuses across the synapse, where it binds to a specific receptor protein. 1. neurotransmitter is referred to as the ligand 2. results in opening of chemically regulated ion channels (a.k.a. ligand-gated ion channels)

Answer 27

Neurotransmitter: directly opens ion channels when it binds to a receptor - Excitatory in some areas of CNS, in some autonomic motor neurons, and in all somatic motor neurons - Inhibitory in some autonomic neurons

Answer 28

- can be stimulated by nicotine | - found on motor end plate of skeletal muscle cells, in autonomic ganglia, and in some parts of the CNS

Answer 29

- can be stimulated by muscarine (from poisonous mushrooms) | - found in CNS and plasma membrane of smooth/cardiac muscles and glands innervated by autonomic motor neurons

Answer 30

drugs that can stimulate a receptor

Answer 31

drugs that inhibit a receptor (ex. beta-blockers)

Answer 32

- enxyme that inactivates AChE activity shortly after it binds to the receptor - hydrolyzes ACh into acetate and choline, which are taken back into the presynaptic cell of reuse (recycles to rebuild ACh)

Answer 33

Regulatory molecules derived from AAs 1. Catecholamines: derived from tyrosine (ex. dopamine, norepinephrine, and epinephrine) 2. Serotonin: derived from L-tryptophan 3. Histamine: derived from histidine

Answer 34

- made from presynaptic axon, released via exocytosis, diffuse across synapse, and bind to specific receptors - quickly taken back into the presynaptic cell (reuptake) and degraded by monoamine oxidase (MAO)

Ch 7 Flashcards

(59 cards)