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IB Bio > Neurons and Synapses > Flashcards

Neurons and Synapses Flashcards

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Biology 101 flashcards
1
Q

Central nervous system (cns)

A

Brain and spinal cord

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2
Q

Peripheral nervous system (pns)

A

Peripheral nerves outside the brain and spinal cord (cranial nerves: emerge directly from the brain stem - 12 pairs; spinal nerves: emerge directly from the spinal cord - 31 pairs)

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3
Q

Stimulus response pathway

A

Stimulus - transmit - response (for the transmission of electrochemical signals)
Change the neurons membrane potential

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4
Q

Stimulus (external or internal)

A

Detected by a sensory receptor in the peripheral nervous system (skin, eyes, ears, etc)

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5
Q

Transmit

A

Sensory neurons (nerves in PNS) transmit the signal (via electrical impulses) to the central nervous system (to relay neurons)

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6
Q

Response

A

“Selected” by CNS (conscious or unconscious) and a signal is sent (via relay neurons in the CNS to motor neurons in the PNS) to effectors (muscles or glands) to generate a response

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7
Q

What is a response

A

Change in an organism due to detection of a stimulus

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8
Q

Neurons (function)

A

To transmit electrical impulses

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9
Q

Basic structure of a neuron

A

Dendrite, cell body (soma), axon

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10
Q

Dendrite (what is it, function)

A

Short branched fibers (branch off the cell body)
Function: receive chemical signals (from sensory or other neurons) and transform them into electrical signals which are sent to cell body (into neuron)

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11
Q

Cell body (soma; what is it, function)

A

Nucleus and cytoplasm + organelles

Function: metabolism and summation of input cells

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12
Q

Axons (what is it, function)

A

Carry signals away from cell body to the end of the axon (axon terminal)

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13
Q

Axon terminal

A

Where neurotransmitters are released for communication with other neurons or effectors

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14
Q

Schwann cells

A

Supporting cells that form the myelin sheath

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15
Q

Myelin sheath

A

Insulating layer on the axon: increases the speed of the saltatory conduction

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16
Q

Saltatory conduction

A

Signal along the axon

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17
Q

Sensory neurons (peripheral)

A

Transmit impulses from body to CNS

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18
Q

Motor neurons (peripheral)

A

Transmit impulses from CNS to body (effectors)

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19
Q

Relay neurons (central)

A

Transmit impulses within CNS

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20
Q

Nerve

A

Bundle of neurons grouped together into a single structure (can be sensory, motor, or mixed)

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21
Q

Role of neurons

A

Pump sodium and potassium ions across their membranes to generate a resting potential

22
Q

Membrane potential

A

The difference in electrical charge across the plasma membrane

23
Q

Resting potential

A

The difference in electrical charge across the plasma membrane when s neuron is at rest (not sending an impulse) = -70mV

24
Q

Inside of the cell at rest

A

More negative
Cations: lots of K+ and few Na+
Anions: proteins, sulfate, phosphate (collectively A-) and few chloride (Cl-)

25
Q

Outside of cell at rest

A

More positive
Cations: lots of Na+ and few K+
Anions: chloride (Cl-)

26
Q

Resting membrane potential steps

A

1) sodium-potassium pumps in the membrane of the axon maintain the resting potential
2) using active transport (atp) sodium potassium pumps pump 3 Na+ ions out of the axon while pumping 2 K+ ions into the axon

27
Q

Result of resting potential membrane steps

A

Outside of neuron is more positive compared to the inside

Outside of axon and inside of neuron are polarized (negative resting potential of -70mV)

28
Q

Role of cytoplasm inside axon in resting membrane potential

A

Contains negatively charged ions that are permanently fixed there (A-) help maintain -70mV

29
Q

Nerve impulse

A

Action potentials propagated along the axons of neurons

30
Q

Action potential is generated and sent down the axon ONLY WHEN:

A

A stimulus caused a voltage gated ion (Na+) channel to open in the axon membrane
Threshold voltage is reached

31
Q

An action potential is…

A

ALL OR NOTHING

32
Q

Action potential consists of…

A

Depolarization and repolarization of the neuron

33
Q

Depolarization

A

Voltage-gated Na+ channels open when threshold potential of -55mV is reached
Na+ rushes into axon (more Na+ outside the cell)
Causing more Na+ channels to open
Domino effect down the axon
Membrane potential becomes more positive

34
Q

Repolarization

A

K+ channels open (Na+ channels close)
K+ rushes out of the axon
Domino effect down the axon
Membrane potential becomes more negative (hyperpolarized)

35
Q

Resting potential restored

A

Sodium potassium pumps: 3 Na+ out for every 2 K+ in
(Refractory period: reset stage - action potential can’t be fired until this is done; the resting potential and Na+/K+ ion concentration gradients need to be restored

36
Q

In myelinated neurons, actions potentials travel…

A

Faster down the axon bc ion channels are only positioned between myelinated portions (saltatory conduction)
Also require less atp to return to resting potential

37
Q

Synapse

A

Junction between two neurons (axon to dendrite)
Transmitting cell- presynaptic neuron
Receiving cell- post synaptic neuron

38
Q

Synaptic cleft

A

Gap that separated the neurons

39
Q

Neurotransmitters

A

Chemically Transmit messages across the synaptic cleft

Either excitatory or inhibitory

40
Q

Excitatory neurotransmitter

A 
Open ion channels (Na+ into post-synaptic cell) 
Cause depolarization (action potentials)
Ex: acetylcholine
41
Q

Inhibitory neurotransmitter

A

Open ion channels (Cl- into post synaptic cells)
Prevent depolarization (action potentials)
Hyperpolarize post-synaptic cell
Example GABA

42
Q

Acetylcholine (Ach)

A

Neurotransmitter

Made by combining choline and an acetyl group

43
Q

Ach is usually released by presynaptic neurons at…

A

Neuromuscular junctions in order to trigger muscle contractions by binding to receptors (cholinergic/nicotinic) in the membrane of postsynaptic muscle fibers to allow Na+ ions to diffuse into postsynaptic muscle fiber cells

44
Q

Acetylcholinesterase (enzyme)

A

Released by presynaptic cell or found in membrane of postsynaptic cell
Continually breaks down Ach into choline and an acetyl group

45
Q

Overstimulation of muscle fibers by Ach can lead to…

A

Fatal convulsions and paralysis. Break down in necessary

46
Q

Reabsorption

A

Choline is taken back into the presynaptic cell to be used to make Ach again

47
Q

Pesticides: blocking synaptic transmission at cholinergic synapses is done by…

A

Irreversibly Binding neonicotinoid pesticides to acetylcholine receptors (in postsynaptic muscle fiber cell membranes)

48
Q

It’s an effective pesticide bc…

A

Ach receptors in insects are different than in mammals, so the neonicotinoid binds stronger to the receptor

49
Q

When the neonicotinoid binds to Ach receptors…

A

It blocks normal Ach binding (block synaptic transmission)

AchE cant break down neonicotinoids, so it’s effect is permanent (paralysis/no muscle contraction/death)

50
Q

Environmental considerations of neonicotinoids

A

Reduces bees and bird populations

IB Bio (26 decks)

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