5-Electrical Signaling/neurotransmission

Front 1

????

Back 1

If concentration gradient is important for movement, as AP progresses, won't the gradient want less Na+ to get in? so how does AP propagate?

Front 2

how does phenomenon like dream/memories occur?

Back 2

the neuron is the unit, but these phenomenon occur through the interactions of many neurons not many isolated ones. Each neuron is capable of turning its neighbors on or off through signals.

The stable firing in patterns represents memories, dreams, etc.

Front 3

What types of signals do neurons send to their neighbors and how are they processed.

Back 3

The signal that a neuron can send either a EPSP or an IPSP and a neuron receives many of these EPSP/IPSP because it has many input neurons.

*excitatory POST synaptic potential

Front 4

How are inputs from different inputs integrated?

Back 4

These inputs are integrated (summed up) across time and across synapses. Meaning the
1.number of input neurons active at any one time
2.how many each send
3. what type of signal (EPSP or IPSP)

these are literally summed to find the overall summed potential of the postsynaptic neuron

Front 5

Types of specialization of Synapses

Back 5

each Synapse is specialized in
1.location
2. structure
3.function
4.target

Front 6

What do transmitters do (big picture)

Back 6

they can control the actions of the target neuron in different ways through connections to its dendrites, cell body or axon

Front 7

Specific examples of varieties of synapses (target neurons)

Back 7

varieties of target
1. Dendrodendritic: dendrites send messages (neurotransmitters) to other dendrites
2. AxoDendritic: axon terminal of one neuron synapses on dendritic spine of another
3. Axoextracellular: axon terminal with no specific target. Secretes transmitter into extracellular fluid to send messages to localized area of many cells.
4. Axosomatic- axon terminal ends on cell body
5. Axosynaptic- axon terminal ends on another terminal
6. Axoaxonic- axon terminal ends on another axon
7. Axosecretory- axon terminal ends on tiny blood vessel and secretes transmitter directly into blood.

Front 8

What is a chemical synapse and the steps it is involved in?

Back 8

synapse is a junction where messenger molecules, or neurotransmitters from one neurons are released to EXCITE OR INHIBIT the next neuron.
*most mammalian neurons are chemical neurons.

Steps:
1. Signal reaches the axon terminal causing reuptake of Ca2+ via voltage-gated Ca2+ channels.
2. Ca2+ inside terminal causes vesicles filled with neurotransmitter to dock and merge with membrane, releasing into cleft
3. neurotransmitters attach to receptors on postsynaptic membrane, causing them to open or close, etc, or open/close other ion channels
4. Ion channels uptake/don't ions causing graded potentials in postsynaptic neuron. (making the cell more positive via ligand-gated sodium channels)

Front 9

neurotransmitter

Back 9

excitatory or inhibitory chemical messengers sent by one neuron to its target.

Outside the CNS, these chemicals are circulated in the blood stream as hormones, but have DISTANT (not indistinct) targets and are much slower to cause an effect.

Front 10

how where neurotransmitters discovered?

Back 10

experiments designed to understand how HEART RATE is controlled helped us to understand how neurons communicate by sending either inhibitory or excitatory messages to speed up or slow down heart rate

Frog Heart experiment- vagus nerve and neurotransmitter ACh (slowing heart rate)

Front 11

Acetylcholine

Back 11

first neurotransmitter discovered in PNS/CNS.
1. Excites skeletal muscles in somatic nervous system
2. Excites/Inhibits internal organs in autonomic nervous system

Front 12

Electrical synapse

Back 12

electrical- passing of ions

these synapses are GAP JUNCTIONS of fused presynaptic and postsynaptic membrane that allow ions, or electrical messages to pass directly from one neuron to the next allowing for VERY FAST (synchronous communication- like extended axon), but are less common

Front 13

What is another name for chemical synaptic transmission?

Back 13

Neurotransmission-because neurotransmitters are transmitted :)

Front 14

Steps in neurotransmission

Back 14

1. Synthesis: neurotransmitter is either made in the cell nucleus and transferred to axon terminal, or the building blocks on transmitters is taken up (imported) into the terminal and made. Both ways are packaged in the terminal.
2. Release: In response to action potential, and then presence of Ca2+ neurotransmitters in vesicles which fuse with membrane via exocytosis are released into the synaptic cleft
3. Receptor Binding: neurotransmitters crosses cleft to bind with receptors on postsynaptic membrane.
4. Inactivation: Neurotransmitter is either taken back into the terminal or inactivated in the cleft.

Front 15

how (mechanism) do psychoactive drugs cause their effects on the body?

Back 15

the drugs participate in at least one of the four steps of synaptic transmission

Front 16

How is neurotransmitter taken away from cleft and why must they do so?

Back 16

If transmitter stays in cleft, the neuron cannot be inhibited/excited anymore. No more communication.
Taken away by:
1. Taken up again by presynaptic cell for reuse
2. Taken up by neighboring glial cells.
3. Diffuses away from cleft
4. Broken down by enzymes in cleft

Front 17

Electrical vs Chemical Transmission

Back 17

Either
Electrical Signal--Chemical Signal--Electrical Signal

or

Electrical Signal-Electrical Signal through Gap junction- Electrical Signal