Midterm 2: Chapter 5/6/7 Flashcards
Stretch sense activated channels (2)
The anatomy+what happens
- The base of each hair is wrapped in a dendrite of a touch neuron. When you bend a hair or otherwise mechanically displace it, the encircling dendrite is stretched
- The displacement opens stretch activated channels in the dendrite’s membrane. When open, these channels allow an influx of sodium ions sufficient to depolarize the dendrite to threshold. At threshold, the voltage-activated sodium and potassium channels initiate a nerve impulse that conveys touch information to your brain.
end plate
The axon terminal contacts a specialized area of the muscle membrane called an end plate, where the axon terminal releases the chemical transmitter acetylcholine
Explain to me muscle contraction
When a motor neuron’s axon collaterals contact a muscle fiber end plate, acetylcholine attaches to receptor sites on the end plate’s transmitter-activated channels, opening them. These large membrane channels allownsimultaneous influx of Na and efflux of K. Acetylcholine does not enter the muscle but rather attaches to
transmitter-activated channels on the end plate to depolarize the muscle to the threshold for its action potential.
myasthenia gravis
the thymus, an immune system gland that normally produces antibodies that bind to foreign material like viruses, makes antibodies that bind to the acetylcholine receptors on muscles, causing weakness and fatigue
Sensory stimuli activate channels on neurons to initiate a nerve impulse, and the nerve impulse eventually ——-
activates channels on
motor neurons to produce muscle contractions.
adrenaline/epiniephrine (2)
Produced where+ what it did
- produced by the adrenal glands located atop the kidneys
- speed up heart rate
In mammals, the chemical that accelerates heart rate is
norepinephrine
Acetacholine (3)
What it does+ what is it made from?
- inhibits heart rate
- activates skeletal muscle
- Made from acetate (found in acidic foods) and choline (found in fats)
neurotransmitters
Chemical messengers released by a neuron onto a target to cause an excitatory or inhibitory effect
the real difference between neurotransmitters and hormones is
the distances they travel
Excitatory neurotransmitter ex+ what happens (2)
- glutamate, acetacholine
- Nat+ channel causes depolarization
inhibitory neurotransmitter+what happens (2)
- GABA, Glycine
- related to Cl- channel or efflux of K+
Structure/sequence of the synapse
axon->dendrite->soma-> axon->dendrite etc
the upper part of the synapse is
the axon terminal, or end foot
the lower part of the synpase is
the receiving dendrite
synaptic vesicles
- Contain neurotransmitter molecules
Storage granules
stores synpatic vesicles
synaptic cleft (2)
What must neurotransmitter do?
- The small gap that seperate the terminal and the dendrite
- neurotransmitter chemicals must bridge this gap to carry a message from one neuron to the next
The surrounding astrocyte contributes to chemical neurotransmission in several ways (3)
- supplying the building blocks for neurotransmitter synthesis
- by confining the movement of neurotransmitters to the synapse
- by mopping up excess neurotransmitter molecules
tripartite synapse
functional integration and physical proximity of the presynaptic membrane, postsynaptic membrane, and their intimate association with surrounding astrocytes
presynaptic membrane
- axon terminal: Neurotrasmitter is stored in synaptic vesicles, contain mitochondria
Neurotransmitter is released…
on the presynpatic membrane side of the synpase
microtubules
transport structure that carriers substances to the axon terminal
Postsynpatic membrane
- the dendritic spine: contain receptors
Gap junction
Fused prejunction and postjunction cell membrane in which connected ion channels form a pore that allows ions to pass directly from one neuron to the next. Constitute a regulated gate between cells because they can
either be open or closed. Allow no such plasticity and are built for speed
and efficient communication
Gap junction elimnates
delay in synpatic cleft
4 steps of neurotransmission
- neurotransmitter synthesized and stored in the axon terminal
- Transported to the presynpatic membrane and released in respinse to an action potential
- Able to activate the receptors on the target cell membrane located on the postsynpatic membrane
- Inactivated or will contine to indefinetly
First way in how neurotransmitters are made
synthesized in the axon terminal from building blocks that are often derived from food
Transporters
are protein molecules that move building blocks across cell membranes (to make transmitters), and they are responsible for packaging some
neurotransmitter classes into vesicles.
Mitochondria in the axon
terminal
provide the energy needed both to synthesize precursor chemicals into the transmitter and to power transporters.
Tryptophan
Precursor for seretonin (found in most protein based foods)
Second way of how neurotransmitters are made
- Synthesized in the cell body acording to DNA instructions and transported on microtubules to axon terminal
The three places neurotransmitters are stored:
- Stored in granules
- Attached to microfilaments
- Attached to the presynpatic membrane
neurotransmitter release:
- at the terminal the action potential opens voltage sensitive cacium channels
- Ca2+ enters the terminal and binds to the protein calmodulin forming a complex
- calmodulin causes some vesicles to empty their contents into the synpase and other get ready to empty theirs (both =exocutosis)
Receptor site activation
After being released, the neurotransmitter diffuses across the synpase and activates receptors on the postsynpatic membrane
Transmitter activated receptors
proteins embedded in the membrane of a cell that has a binding site for a specific neurotransmitter
Deactivation of the neurotransmitter is achieved 4 ways:
- Diffusion: Some of the neurotransmitter simply diffuses away from the synaptic cleft and is no longer available to bind to receptors
- Dergadation: Enzymes in the synaptic cleft break down the transmitter
- Reuptake: Membrane transporters specific to that transmitter may bring it back into the presynaptic axon terminal for reuse
- Glial reuptake: Taken by neighbouring glial cells where it can be modified or exported to the presynpatic neuron
axomuscular synapse
an axon synapses with a muscle end plate, releasing acetylcholine
axodendritic synapse
the axon terminal of a neuron synapses with a dendrite or dendritic spine of another neuron
Axoextracellular
synapses
no specific targets but instead secrete their transmitter chemicals into the extracellular fluid
axosecretory synapse
a terminal synapses with a tiny blood vessel, a capillary, and secretes its
transmitter directly into the blood
dendrodendritic synapses
Dendrites also may send messages to other dendrites
Axosomatic
A direct connection between the axon of one neuron to the cell body of another neuron. These tend to be inhibitory synapses.
Vegas nerve
inhibitory but for muscles it make it contract
excitatory synpase (5)
typicallyon+active zone+materia on membrane is+synpatic vesicle
- typically on the shafts or spines of dendrites
- the active zone on an excitatory synapse is larger
- The material on the presynaptic and postsynaptic membranes is denser
- synaptic cleft is wider
- round synaptic vesicles
Inhibitory synpase (2)
- typically on the cell body
- the vesicles in inhibitory synapses are flattened
Ionotropic receptors
associated with a pore that can open to allow ions to pass through the membrane, rapidly changing membrane voltagein one of two possible ways. These ion channels may allow Na to enter the neuron, depolarizing the postsynaptic membrane, and so have an excitatory action on the postsynaptic neuron. Or they may allow K to leave the neuron or Cl to enter the neuron, hyperpolarizing the postsynaptic membrane, and so typically have an inhibitory action on the postsynaptic neuron
metabotropic receptor
the 2 cases
Acetylcholine binds to binding site on the receptor which is attched to the G protein complex. After it binds, this triggers change in G protein complex and the subunit alpha protein unbinds and travels downstream and attach to another channel (allow ion to pass). In nother case, alpha protein attach to an enzyme whoch activates a second messenger. The second messenger then activates DNA transcription factors and produce new proteins and stuff that cause placidity
autoreceptors
responds to the neurotransmitter released by the neuron
- negaticive feedback look by itself
4 requirement for identifying neurotransmitters
- Chemicals must be synthesided in the neuron or be present in it
- When the neuron is active, the chemical must be released and produce a response in some target
- The same response must be obtaied when the chemical is experimentally placed on the target
- a mechanism must exist for removing the cemical from its site of activation
Small molecule transmitter (8)
quick acting, often synethsized from dietary nutrients
- acetocholine
- dopamine
- serotonin
- epiniphrine/adrenaline
- glutamate
- GABA
- glycine
Gaba is
inhibition in the brain
- lipid transmitter
Glycine is
inhibition in spinal cord
Acetylcholine synthesis:
- choline: breakdown of fats in diet (AcetylCOA)
- Acetate: found in acidic food (ChAT)
- Acetyl CoA carries acetate to the transmitter synthesis site, ChAT transfer acetate to choline
Acetylcholine breakdown
After ACh has been released into the synaptic cleft and diffuses to receptor sites on the postsynaptic membrane, a third enzyme, acetylcholinesterase (AChE), reverses the process, breaking down the transmitter by detaching acetate from choline. The breakdown products can then be taken back into the presynaptic terminal for reuse.
Peptide transmitter
a result of protein synthesis.
- Synthsized by instructions in the neuron’s DNA, packaged in membranes on the Golgi bodies, and transported on microtubules to the axon terminal.
Lipid transmitter (2)
- cannot be packaged and stored in vesicles, which are composed of lipids, but are rather synthesized “on demand” when an action potential reaches the axon terminal.
- Travel back and affects travel upstream
Activating systems
neural pathways that coordinate brain activity through a single neurotransmitter
- cholinergic
- doaminergic
- noradrengic
- serotonergic
Cholinergic system (2)
What it does+ related to
- The cholinergic system participates in typical waking behavior, attention, and memory
- alzhimers
Acetylcholinesterase inhibitors+ alzhimers
Inhibit the enzyme acetylcholinerase from breaking down acetylcholine in the synaptic cleft and can help treat memory deficits
Dopamiergic system
- The nigrostriatal dopaminergic system plays a major role in coordinating movement.
- the mesolimbic dopaminergic system plays a role in addiction/reward
Noradrenergic system (2)
What it does+ the two extreme behaviours
- Behaviors and disorders related to the noradrenergic system concern emotions
- depresion-mania
Serotonergic system (2)
What it does+ decrease in this causes
- Active in maintaining waking brain activity
- decrease in seretonin are related to depression
Parkinson is caused by
loss of dopamergic cells in the substantia nigra, these cells project to the caudate nucleus, an area in the basal ganglia that is involved in motor control
Habituation (2)
neurotransmiter…
Learning behavior in which a response to a stimulus weakens with repeated presentation
(gets use to it)
- less neurotransmitter is being received
Sensitization (2)
What it is+biological system occuring
- Learning behaviour in which a response to a stimulus strengthens with repeated presentations because the stimulus is novel or stronger than usual
- More ca2+ in the presynpatic terminal, more neurotransmitter release
Psychopharmacology
The study of how drugs affect the nervous system and behaviour
Psychoactive drugs
substances that act to alter mood, though or behaviour
Oral administration
safe/easy and convient
In halation
quick, less barriers than oral administration
Injection
Quick acting, few barriers
Drugs…
mimic neurotransmitters
Agonist drugs
drug enhances the function of a synpase
Anatagonist drugs
drugs that block the function of a synpase
metabolic tolerance
the number of enzymes needed to break down alcohol in the liver, blood, and brain increases. As a result, any alcohol consumed is metabolized more quickly, so blood alcohol levels fall.
Cellular tolerance
cellular tolerance, brain cell activities adjust to minimize the effects of alcohol in the blood. Cellular tolerance can help explain why the behavioral signs of intoxication may be so low despite a relatively high blood alcohol level
tolerance is due to
repeated use of a drug
Sensitization is a result of
occasional use of a drug
Drug sensitization changes at the synpase: (4)
- Increase in the amount of neurotransmitter released
- increased in the number of metabotropic receptors present on the postsynpatic membrane
- decrease in the rate of transmitter metabolism/reuptake
- changes in the number of synapses
Psychoactive drugs: behavioral stimulants
amphetamine
cocaine
(Dopamine agonists)
Nicotine
agonist (helps achecholine at synapse)
at ionotropic
Atropine
achyltocholine agonist
at metabotropic receptor
