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anatomy > the neuron and nerve transmission > Flashcards

the neuron and nerve transmission Flashcards

1
Q

what 2 cells make up the nervous system

A

neurons and neuroglia

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2
Q

what does it mean that neurons possess electrical excitability?

A

they have the ability to respond to a stimulus and convert it into an action potential

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3
Q

what is action potential?

A

electrical signals (impulses) that travel along the membrane of a neuron

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4
Q

what are the parts of a neuron that are part of the cell body?

A

cell body, nissl bodies, neurofibers, nerve fibers

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5
Q

what is a cell body?

A

contains the nucleus and organelles of a neuron

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6
Q

whats a nissl body and its function

A

clusters of rough endoplasmic reticulum that synthesizes proteins used for growth of neurons and to regenerate axons

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7
Q

what are neurofibrils

A

bundles of intermediate filaments that provide cell shape and support

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8
Q

what are nerve fibres and gives 2 examples

A

neuronal extensions that emerge from the cell body (axons and dendrites)

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9
Q

what are dendrites (describe)

A

the little trees
processes that are info receivers and contain receptor sites for chemical messengers from other cells to bind to

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10
Q

what are the parts associates with the axons

A

axons, axon hillock, axon telodendria, collaterals

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11
Q

what are axons

A

send nerve impulses toward other neurons

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12
Q

whats an axon hillock

A

site of transition between axon and cell body

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13
Q

what are axon telodendria

A

brances/processes at the distal end of axon

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14
Q

what are collaterals

A

things that branch off of axon

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15
Q

what is the site between 2 neurons?

A

synapse

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16
Q

how are structural neurons classified and what are the 3 types

A

they are classified according to # of processes that are directly attached to the CELL BODY
1. unipolar (1 processes –> sensory receptors)
2. bipolar (2 processes –> in ear and eye)
3. multipolar (3+ processes –> brain and spinal cord)

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17
Q

how are functional neurons classified and what are the 3 types

A

classified according to the direction in which the nerve impulse travels
1. sensory (detects and delivers info, forms an action potential)
2. interneurons (processes sensory info and elicits a motor response by activating the motor neurons, makes decision)
3. motor neurons (sends info to muscles or glands, conveys action potential)

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18
Q

what are neuroglia

A

helper cells that holds nervous tissue together
doesn’t generate action potentials
can multiply/divide in mature nervous system

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19
Q

what are 4 types of neuroglia in the cns

A

astrocytes, oligodendrocytes, microglia, ependymal

20
Q

what are astrocytes

A

star shaped cells that are the largest and most numerous
- have microfilaments that allows them to hold/support neurons
- protect neurons from harmful things in blood (form blood barrier)
- regulate growth/migration/interconnections of neurons
- maintain proper environment

21
Q

what are oligodendrocytes

A

look like astrocytes but are smaller with less processes
- form and maintain myelin sheath

22
Q

what are microglia

A

small cells with sharp spikes
- immune function
- remove cell debris
- phagocytize (ingest) microbes and damaged nervous tissues

23
Q

what are ependymal

A

cells arranged in a single layer
- lines ventricles of brain/spinal cord
- produce/monitor/assist in circulation of cerebrospinal fluid

24
Q

what are the 2 neuroglia cells in the pns

A

schwann cells and satellite cells

25
Q

what are schwann cells

A

circle around axons and form the myelin sheath
- it only myelinates a single myelinated axon
- help in axon regeneration

26
Q

what are satellite cells

A

flat and surround cell bodies of neurons (have the same function as astrocytes)
- provide structural support
- regulate exchanges

27
Q

what are myelin sheaths

A

multilayered membrane coverings made up lipids and proteins that wrap around axon

28
Q

what is the purpose and myelin sheaths

A

insulate the axon and inc speed of nerve impulse

29
Q

what produces myelin sheaths

A

oligodendrocytes and schwann cells

30
Q

what are nodes of ranvier

A

gaps in myelin sheath where collaterals arise

31
Q

how do neurons communicate and what are 2 types of communication

A

communicate through electrical signals
- graded potentials: short distance
- action potentials: long distance

32
Q

what are the important ion channels

A

voltage-gated: respond to change in membrane potential (voltage)
ligand-gated/chemically gated: respond to change in chemical stimulus (addition of Cl- or Na+ for example)

33
Q

what is a resting potential (resting membrane potential is another name)

A

when the outside of the cell is slightly +ve charged and the inside of the cell is slightly -ve charged and the inside of the cell has a resting membrane potential of -70 mV

34
Q

what 3 things cause the the resting potential to be -70 mV

A
  1. unequal charge distribution –> the outside of the cell is richer in Na+ and Cl- while the inside of the cell is rich in K+. Membranes have more K+ leak channels so K+ diffuses down their conc gradient which causes the inside of the cell to be less +ve
  2. anions (-ve) in the cell are attached to things that can’t leave like proteins
  3. Na+K+ ATPase pump offsets leaks so 3 Na+ are pumped out while 2 K+ are pumped in
35
Q

what is an action potential

A

sequence of rapid events that dec and reverse the membrane potential then restore it to the resting rate

36
Q

what is a threshold

A

the voltage that must be reached in order for the action potential to occur
if the stimulus is able to bring the membrane to -55 mV (the threshold) then the ac pot will happen

37
Q

what is all or nothing theory

A

an action pot will either occur completely or it won’t at all.. no half assing

38
Q

what are the 2 voltage gates that open during ac pot

A
  1. Na+: open first. open at -55mV and close at +30 mV
  2. K+: open second. Open at +30 mV and close at -70 mV
39
Q

describe what happens during ac pot

A
  1. stimulus causes the membrane to reach the threshold (goes from -70 mV to -55 mV). this causes the Na+ gates to open and Na+ flows in and brings the inside of the membrane to +30 mV. this is the depolarizing phase
  2. the membrane is at +30 mV and this causes the K+ channels to open and cause the Na+ gates to close. K+ goes out of the cell and the membrane pot goes back to the low negatives (-90 mV). this is the repolarizing phase
  3. the K+ gates close. the overshoot of the membrane pot is corrected by the Na K pumps that bring it back to the resting potential. this is the hyperpolarizing period
40
Q

what is the difference between the absolute and relative refractory period

A

absolute: when the membrane pot is at +30 mV. another act pot cannot occur because the opening of the Na+ gate will remain blocked (it’s inactive) until the membrane goes back to the resting rate

refractory: during the hyperpolarizing phase, only a very very strong stimulus can create another ac pot because it needs to work harder to bring the membrane to it’s threshold (the Na gate is closed rather than inactive)

41
Q

what is propagation

A

when an ac pot/impulse keeps it’s strength and travels as it spreads along the membrane of the axon
- it allows impulses to go from one part of the body to another
- it’s not the same ac pot that propagates.. they regenerate over and over
- only propagates in one direction

42
Q

what are the 2 types of propagation

A
  1. continuous: happens in unmyelinated axons and muscle fibers. step by step de/repolarization of each segment along the membrane
  2. saltatory: occurs in myelinated axons. ac pot leaps from one node to the other bc the first node’s ac pot creates a current that depolarizes the membrane that opens the na+ gate at the next node, and then current then flows thru the next node. cycle repeats
43
Q

what is a graded potential

A
  • potential that occurs due to chemical gates in the dendrites of the neuron (usually caused by neurotransmitters)
  • have varying amplitude that depends on the amount of stimulus
  • diff neurotransmitters can cause epsp or ipsp
44
Q

what are the 2 types of ‘graded’ potentials

A

epsp: excitatory post synaptic potential: when the Na+ gates are opened and sodium causes a depolarization, which will most likely cause an ac pot (membrane will reach threshold)
ipsp: inhibitory: when the cl gates are opened and causes hyperpolarization. It won’t cause an ac pot

45
Q

what is a neuromodulator

A

messenger released from a neuron that affects the transmission of the signals between neurons

46
Q

what are neuron pools

A

a collection of motor neurons whose axons all connect to the same muscle

anatomy (12 decks)

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