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26 Cards in this Set

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  • Back
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The functional connection between a neruon and a second cell
Electrical Synapse
-Requires that cells are electrically coupled through gap junctions.

- Most common in cardiac muscle
-Smooth muscles
-Allows for rhytmic contraction of large masses of muscle cells
- Some brain regions
-Between some glial cells
-Present in many embryonic tissues
Function and location
Chemical Synapses
-Chemicals called neurotransmitters released fromy presynaptic cells stimulate action potentials in postsynaptic cells
-Pressynaptic neuron stores neurotransmitters in synaptic vesivles at th eaxon terminal.
-Arrival of action potential at axon terminal opens voltage gated Ca2+ channels
- Rapid influx of Ca2+ into axon triggers fusion of synaptic vesivles with axon membrance and release of neurotransmitter into snaptic cleft by process of exocytosis
-Tetanus and botulism toxins effect the exocytosis of synaptic vesivles
Description of process by which chemical synapses work
-Released into synaptic cleft bind to specific recptor proteins locatedo n the post synaptic membrane
What they do whne released
Ion channels when released
- Binding of the neurotransmitter to its receptor causes ion chanels to open in the postsynaptic membrance
Post synaptic membrane potential
-Opening of ion channels produces changes in postsynaptic membrane potential
-Excitatory postsynaptic potential= depolarization
- Caused by Na+ ions
- Graded in magnitude (not all or none)
- No refractory period
- Inhibitory postsynaptic potential = hyperpolarization
-Graded response ( not all or none)
- Cl- channels open
- ACh
- 2 receptor types:
1) Nicotinic ACh receptor (stimulatory)
2) Muscarinic ACh receptor (Stimulatory or inhibitory)
-Inactivation of ACh in the synaptic cleft is achieved through enzyme acetylcholinesterase (AChE)
ACh in CNS
-Cholinergic neurons use ACh as neurotransmitter
-Excitatory effects, EPSP
- Alzheimer's Disease, typically there is loss of cholinergic neurons that terminate in hippocampus and cermral cortex.
ACh in PNS
- Somatic motor neurons form synapses with skeletal muscle cells, EPSP
- Release of ACh produces action potentials in muscle fibers stimulating muscle contractions
-Autnomic motor neurons that have parasympathetic effects use ACh as their neurotransmitter
-Effects can be EPSP or IPSP
- Includes epinephrine, norepinephrine, dopamine, and serotonin.
- Derived from amino acids
Inhibition of Monoamines stimulatory action
1) reuptake by presynaptic neuron
2) degradation by monoamine oxidase (MAO) released by presynaptic neuron
3) degradation by catechal-O- methyltransferase in postsynaptic neron
-MAO inhibitors are common drugs
-role in regulation of mood, behavior, appetite
-many different subtypes of receptors
-SSRIs= serotonin-s[ecific reuptake inhibitors
-anti-depressants, anti-anxiety drugs
- Prozac, Paxil, Zoloft, Luvox
these drugs leave serotonin in synapse for longer period of time
-dopaminergic neurons
-nigrostriatal dopamine system
-dopaminerging neurons in substantia nigra (region of brain) send axons to group of nuceli called the corpus striatum deep in cerebrum
-involved in initiation of skeletal movements
Parkinson's Disease
-Involves destruction of dopaminergic neurons in substantia nigra
- Muscle tremors and rigidity
- difficulty initiating movements and speech
Mesolimbic dopamine system
- Dopaminergic neurons in midbrain send axons into limbic system within forebrain
-involved in behcaior and reward
-Schizophrenia may involve overactivity of mesolimbic dopamine pathways
-Some addictive drugs activate dopaminergic pathways in limbic system:
nicotine, cocaine, morphine, amphetamines, alcohol
-Used by sympathetic neruons in PNS
-Varied effect depending on organ
- Involved in behavioral arousal in CNS (fight or flight)
Amino Acids
- Glutamic Acid
- Glycine
-Gamma-aminobutyric acid (GABA)
Glutamic Acid
- Glutamate
- Excitatory neurotransmitter in CNS
- Bind to NMDA receptors
- Important in memory storage
- Excessive release may result in epilepsy and excitotoxicity of neurons
- Opens Cl- channels to hyperpolarize postsynaptic cells
- Helps control and coordinate skeletal muscle movements
Gamma-aminobutyric acid
- Most prevalent neurotransmitter in brain
-inhibitory neurotransmitter ISPS
- Similar to glycine in action (opens Cl- channels)
- Involved in motor control
- Huntington's Disease is caused by deficiency in GABA-releasing neurons, causing uncontrolled movements
- Neuropeptides
-Endogenous Opioids
- Neuropeptide Y
- Nitric Oxide (NO)
Endogenous Opioids
- activated by stressors to block transmission of pain
-B-endorphin, enkephalins, dynorphin, cannabinoids
-may mediate reward and positive reinforcement pathways (euphoria, felling of well being)
-released during exercise
Neuropeptide Y
** Most abundant neuropeptide in brain**
-Variety of effects
-powerful stimulator of appetite
-leptin supresses appetite by inhibiting neuropeptide Y release
Nitric Oxide
- Acts as a neurotransmitter in both CNS and PNS
-In CNS, may be involved in learning and memory
- In PNS, causes smooth muscle relaxation in target organs:
blood vessels, gastrointestinal tract, penis, respiratory tract