3-Synaptic Transmission and Neural Intergration Flashcards Preview

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Flashcards in 3-Synaptic Transmission and Neural Intergration Deck (30):

What are chemical synaptic transmissions?

The chemical synaptic transmission is dependent on calcium.

1. APs propagate to the terminal down pre-synaptic terminal and depolarizes the inside of the cell. The only purpose of the AP is to depolarize this terminal and open up voltage gated calcium channels in the membrane.

2. Calcium is positive and there is more calcium outside the cell then in. AP depolarize presynaptic terminal, thus activating VG calcium channels.

3. Ca moves into the terminal and triggers exocytosis making vesicle fuse with the presynaptic membrane and release a neurotransmitter. These vesicle ruptures and release a NT into the synaptic cleft.

4. Once in the cleft it binds to a receptor to produce a response - an EPSP, IPSP, etc. Any excess NT can broken down by enzymes. diffuse away, or be reuptaken.


How do you turn off presynaptic transmission?

In order to turn of presynaptic transmission you need to remove the neurotransmitter from synaptic cleft. Removal of calcium from the presynaptic terminal or the process wont stop. There isn a whole lot of calcium in the cell its located in the ER and the mitochondrion. I calcium is needed or not needed it has to be actively pumped in or out. Exhaustion (temporary) cut of neurotransmitter supply. You run out o ACh. Calcium is actively transported by the Calcium ATPase.


What are the postsynaptic responses?

Inotropic responses are mediated by channel-linked (ionotropic) receptors and are fast. The neurotransmitter binds and acts like a channel that opens so ions can cross through the channel. The receptor is an ion channel. The NT binds to receptors. Can only open a channel.

Metabotropic are mediated by G-protein coupled receptors and are slow. NT binds to a receptor and one of the subunits has to break free and bind to the receptor which can open or close the ion channel. Metabotropic can open or close a channel.

Postsynaptic responses take the form of a change in membrane potential, a postsynaptic potential (PSP). Can be excitatory or inhibitory.


Describe the excitatory synapses.

Excitatory Synapses: PSP is depolarizing, brings membrane potential closer to AP threshold, excitatory postsynaptic potentials (EPSPs), postsynaptic AP more probable.

Excitatory inotropic synapses- when ACh binds to nicotine receptors. Nicotine receptors are permeable to both, but more sodium goes in than potassium leaving because of the driving force.


Describe the inhibitory synapses?

Inhibitory Synapses: PSP brings membrane potential away from AP threshold, inhibitory postsynaptic potentials (IPSPs), postsynaptic AP less probable. Sometime these will be a neurotransmitter and binds to a K+ receptor, opens it, causing K+ to leave producing a IPSP.


How do neuron communicate?

Neurons communicate by divergence or convergence. Divergence is communicating between one presynaptic neuron and multiple postsynaptic cells.
Convergence is communication between several presynaptic cells and one postsynaptic cell.


What is neural integration?

Neural integration is the combination of synaptic inputs arriving at the same time which determines AP firing. If axon hillock is depolarized to threshold then an AP will happen. If axon hillock is not depolarized to threshold there will be no AP. Timing plays an important role, not only do they have to be the same size, but they have to get to the cell at the same time in order to cancel each other out.


What are the Acetylcholine receptors?

The ACh receptors are Nicotinic Cholinergic Receptors and Muscarinic Cholinergic Receptors. ACh cause skeletal muscles to contract and causes heart muscles to relax. The same NT can have opposite effect in different part of the body. Cell have one or the other, having both would cause conflicting signals. This is called a high fidelity system because there is no room for error.


What are Nicotinic Cholinergic Receptors?

Nicotinic Cholinergic Receptors are found on your skeletal muscles. Pretty much on every voluntary muscle that you have. ACh causes the skeletal muscle to contract. Nicotinic receptors blocked by curare (from bark of South American vine—poison darts) causes skeletal muscle paralysis.


What are Muscarinic Cholinergic Receptors?

Muscarinic Cholinergic Receptors use the metabotropic pathways of the heart. Your heart muscles use this pathway which is a G-protein coupled pathway and results in an ion channel opening. Muscarinic receptors are blocked by atropine. Ex. for someone with a heart attack, give it epinehrines tells heart not to relax


What are the biogenic amines?

The biogenic amines are:
Catecholamines which are Dopamine - Released from CNS.
Norepinephrine - Released from CNS and PNS (binds adrenergic receptors).
Epinephrine - Released from CNS and adrenal medulla (binds adrenergic receptors).

These receptors are generally metabotropic.
Serotonin - released by CNS and controls sleep and emotions.
Histamine- released by CNS and released from non-neuronal mast cells as well as during allergic reactions.


What are the neurotransmitter amino acids?

The amino acid neurotransmitters are: Glutamate, Aspartate, GABA (Gamma Aminobutyric Acid), and Glycine.
GABA and Glycine are inhibitory neurotransmitters - IPSP, makes the cell more negative. There are only two ways to make the cell more negative: et positive ions to leave or negative ions to enter. In the case of GABA and Glycine, they are chloride channels. The chlorine enter and makes the cell negative, hypo-polarizing it.


What are the two types of synapses?

The two types of synapses are:

Electrical which includes Gap junctions, Ions and second messengers which flow directly from one cell to another and can be bidirectional, and act to synchronize electrical activity. They are physically connecting two cells. Electrical synapses are fast and can move in either direction, but isn't great for long distances.

Chemical synapses send chemicals (neurotransmitters) across synaptic cleft and are unidirectional. They can only move in one direction.


What is Glutamate?

Glutamate is the most common excitatory neurotransmitter in the CNS. Metabotropic glutamate receptors and Excitatory Ionotropic glutamate receptors include AMPA and Kainate (present in Na+ channels), and NMDA (present in Ca2+ channels).


What is GABA (Gamma Aminobutyric Acid)?

The GABA Ionotropic inhibitory receptors include GABAA receptors and GABAC receptors.
The GABA Metabotropic receptor is the
GABAB receptors.


What is glycine?

Glycine is very similar to GABA in its mode of action, but still an inotropic channel. It is mainly used in the PNS-why need inhibition in PNS. For certain organisms, like fish, they swim by lipping their tails. They need to contract muscles on opposing sides and relax muscles on opposing sides. In order to do this they need glycine. Glycine is stopping the movement o others and ACh moves what you are trying to move. Receptors are chloride channels and mediates inhibition in PNS.


What is long-term potentiation (LTP)?

Long term potentiation is the mechanism responsible for learning and memory formation. Process by which cells become more efficient at communication via synaptic transmission. Results in long-term structural and electrical changes to a synapse.


How do we learn something?

We learn by repetition. The area of the brain that is associated with the memory is the hippocampus - the pre and post synaptic cells in this area.
1. Glutamate is released from activated presynaptic neuron.
2. Glutamate binds with both AMPA (sodium channels) and NMDA (calcium channels).
3. Binding opens AMPA receptor channel.
4. Sodium entry though open AMPA channel depolarizes postsynaptic neuron, producing EPSP.
5. Binding opens gates of NMDA receptor channel, but Mg2+ still blocks channel. Sufficient depolarization from this AMPA opening plus other EPSP drives Mg2+ out.
6. Calcium entry through open NMDA channels activates Calcium second messenger pathway.
7. Second-messenger pathway promotes insertion of additional AMPA receptor in postsynaptic membrane, increasing its sensitivity to glutamate.
8. Second messenger pathway also triggers release of retrograde paracrine (likely nitric oxide).
9. Nitric Oxide stimulates long lasting increase in glutamate release by presynaptic neuron.


What are the types of memory?

The types of memory are Long term and short term memory.


What is long term memory?

Long-term memory can be classified into:
Nondeclarative (implicit) memory of simple skills and how to do things.

Declarative (explicit) memory of things that can be verbalized. People with amnesia have impaired declarative memory, further broken into:
Semantic memory for facts.
Episodic memory for events.


Describe the relationship between emotions and memory.

Emotions sometimes strengthen and other times weaken memory formation.
If the memory has an emotional component, an area of the brain called the amygdala is involved in memory formation. This is why you only remember the really good or really bad days of your life. Stress impairs memory formation and retrieval.


What is the purpose of sleep?

The function of sleep is unclear.

Catch-up is the restoring processes that have progressively degraded during wakefullness. Adenosine builds up during day and inhibits arousal-drowsiness. Injections of adenosine=sleep. Caffeine blocks adenosine receptors. Adenosine levels drop during sleep, ATP is being made.

Repair damage from toxic free radicals.
Your lymphatic systems is found everywhere except your brain. One of its function is to rinse out its brain. This is done only at night.

Long-term structural and chemical adjustments for learning and memory. Used to fine tune and hardwire memories formed during the day. Might be why infants require so much sleep.


How important is sleep?

In 1950, the average person claimed to get ~8.5 hours of sleep a night. In 2009, that number fell to ~6.5 hours a night.
In 2009, a group of researchers conducted a clinical study on 20 healthy, 18-22 year old males.
They monitored brain wave activity during sleep, and as soon as the subjects entered the REM stage of sleep, they were woken up by a loud alarm in the room.

During the day, subjects were allowed to eat at regular times and perform normal daily tasks.

This continued for 2 weeks.

At the end of the study, all 20 subjects were in a pre-diabetic state, where their cells were becoming resistant to insulin.

They all had elevated blood pressure and cholesterol levels, and were at risk for heart disease.


What is sleep?

Sleep is an active process consisting of two types of sleep characterized by different EEG patterns and different behaviors Slow-wave sleep an Paradoxical, or REM sleep.


What is an EEG?

Electroencephalogram (brain waves) are collected by external electrodes on the scalp. Not due to action potentials, but instead represent the collective postsynaptic potential activity in the cortex (EPSPs + IPSPs). Not recording individual AP, but all o the EPSP and the IPSP. The cortex is the part of the brain you see when you look at the brain.


What is language?

Most of the knowledge of how the brain controls language has come from studying people with speech problems called aphasias. Two forebrain areas are identified as important : Broca’s area and Wernicke’s area.


What is Broca's aphasia?

Broca’s aphasia involves slow, poorly articulated speech. There is no impairment in understanding.
Controls motor aspects of speech
Interestingly, other actions of the tongue, lips, and larynx are not affected; only the production of speech is affected. They can understand words, but they cannot make the sounds to make words.


What is Wernicke's Aphasia?

Wernicke’s aphasia involves production of rapid speech with no meaning, called “word salad.” Language (spoken and written) comprehension is destroyed. Controls understanding of words. People with this disease cannot understand, speak, or write words .


What is speech?

Speech is a two part process. To speak, word comprehension originates in Wernicke’s area on the left side of the brain, and is sent to Broca’s area on the right side of the brain. Broca’s area sends information to the motor cortex to direct movement of appropriate muscles. If either of these areas are damaged, either understanding or speech is affected.


What are mirror neurons?

Mirrors neurons are Found in frontal and parietal lobes. Connected to emotion centers in the brain. Activated when one does something, and when one sees something being done. Allows for empathy. Mirror neuron are activated when we observe the expressions of others and mimic them ourselves. This is why you yawn when others yawn. This is why you grimace when you see someone else get hurt, or shiver when you see a spider crawl over someone in a movie. Not everyone have these responses. May be involved in the ability to learn social skills and language. Have been implicated in autism. Individuals with autism have mirror neurons that don’t respond to emotions or actions of others, but only to their own actions.