Synapses Flashcards
What is the function of synapses
Send information to another cell or target
Pre-synaptic part of the synapse
Axon
Post-synaptic part of the synapse
Dendrite
What are the types of synapses?
- Axo-somatic
- Axo-dendridic
- Axo-axonal (right by presynaptic terminal)
Do synapses with different locations have different functions?
The axo-somatic and axo-dendridic synapses send information. Axa-axonal synapses modulate how much neurotransmitter is released by the second neuron.
What type of ion channels do APs open in the presynaptic terminal?
Voltage-gated calcium ion channels
What happens when calcium enters the presynaptic terminal?
Calcium activates a series of proteins and enzymes, which moves the vesicles to the presynaptic terminal and releases neurotransmitters into the synaptic cleft
What determines how much neurotransmitter is released?
The amount of calcium that enters the presynaptic terminal (more calcium = more neurotransmitter); determine by how many and how long voltage gated-ion channels are opened
What ion channels are involved in EPSPs?
Na and Ca ion channels
What ion channels are involved in IPSPs?
K and Cl ion channels
In the nervous system, EPSPs can summate to generate an action potential. What kinds of summation are used to do this?
Temporal and Spatial; usually need summation to fire AP
Do you need summation at the NMJ to produce EPSP in the muscle to produce a muscle contraction?
No, an AP in the motor neuron is sufficient
What happens when there are both EPSPs and IPSPs at a postsynaptic neuron?
Summation is important here - depends on which potential summation is stronger
With presynaptic facilitation, the synapses are axon-______. An [inhibitory/excitatory] synapse neuron (1) makes an action potential in the 2nd neuron last [longer/shorter] and [increases/decreases] the number of calcium ions that enter the presynaptic terminal.
Axo-axonal; excitatory; longer; increases
{Depolarization}
With presynaptic inhibition, an action potential in the 2nd neuron last [longer/shorter] and [increases/decreases] the number of calcium ions that enter the presynaptic terminal.
shorter; decreases
{Hyperpolarization}
Collection of neuorns in one region that communicate among themselves to process things
Local circuits
Generalized information that goes from one point to wide-spread regions of the nervous system; i.e., level of arousal, sympathetic nervous system
Diffuse systems
Transmit specific information from one point to another; i.e., making your thumb move
Relay systems
What are the two receptors for ACh?
- Nicotinic
2. Muscarinic
What makes acetylcholine? what breaks it down?
Choline acetyltransferase (CAT); Acytlcholineesterase (AChE)
What are the type of receptors at the NMJ that bind ACh? What is its function?
Nicotinic; contraction of muscles
What are the type of receptors in the autonomic nervous system that bind ACh? What is its function?
Muscarinic (target) and nicotinic (postganglionic neuron); Regulate visceral function
What are the type of receptors in the central nervous system that bind ACh? What is its function?
Nicotinic and muscarinic; autonomic regulation and selection of objects of attention
What are the main neurotransmitters of central nervous system?
Amino acids (aspartate, glutamate, glycine, GABA)
What are the excitatory amino acids?
- Aspartate
2. Glutamate
What are the inhibitory amino acids?
- Glycine
2. Gamma-aminobutyric acid (GABA)
What is the principle fast neurotransmitter? what is its functions?
Glutamate; Learning, Development, and Neuronal death after CNS injury
Inhibits postsynaptic membranes, particularly in brainstem and spinal cord; act to prevent excessive neural activity; block the effects of these neurotransmitters can produce seizures
Glycine
Major inhibitory neurotransmitter in CNS; Interneurons in spinal cord; act to prevent excessive neural activity; block the effects of these neurotransmitters can produce seizures
GABA
Where are the cell bodies of monoamines located? what are their overall functions?
Brain stem; Diffuse systems: sleep, wake, consciousness, attention, regulation of pain
What neurotransmitters are included in monoamines?
- NE (noradrenaline)
- Dopamine
- Serotonin
- Histamine
What are the precursors to catecholamines? What is the immediate precursor to dopamine?
Phenylalanine and Tyrosine; Dihydroxyphenyl-alanine (l-DOPA)
What are the catecholamine neurotransmitters?
Dopamine, NE, and epinephrine
What does dopamine do?
- Motor activity
- Cognition
- Motivation (can result in addiction)
What disorder results from too much dopamine?
Schizophrenia
What is NE’s functions?
- Autonomic nervous systems (fight or flight, panic disorders)
- Attention and vigilance
Functions include:
- Open/close ion channel
- Activate/inhibit enzymes
- Regulate calcium levels in cell
- Activate/inactivate genes
G-protein mediated receptors
What are the steps that occur to activate a G-protein mediated receptor?
Ligand binds to receptor -> receptor activates G-protein -> G-protein moves through the cell to its effectors
~takes longer to have an effect, but lasts longer once they happen
What are 3 second messengers used in G-protein mediated receptor?
- Cyclic AMP (cAMP)
- Arachidonic acid
- Inositol triphosphate
2nd messenger that modulates ion channels (pain sensation in PNS)
cAMP
2nd messenger that produces prostaglandins; regulate vasodilation, Enhances inflammation
Arachidonic acid
2nd messenger that regulates Calcium ion stores
inositol triphosphate
Nicotinic, ligand-gated ion channel; at neuromuscular junction, autonomic ganglia, and some parts of CNS
ACh receptors
What are the functions of ACh receptors?
- Memory and learning (decrease of receptors seen in Alzheimer’s disease)
- Neuronal development
G-protein linked receptors; Autonomic targets = heart, Selected areas of brain
Muscarinic acetylcholine receptors
What are the functions of muscarinic aceytlcholine receptors?
autonomic function (parasympathetic; i.e., slows heart)
Both ion channels and G-protein linked; Ion Channels - AMPA, Kainite, NMDA;
G-protein – metabotropic receptors
glutamate receptors
Receptors that have normal neurotransmission; long-term changes in the CNS (Long-term potentiation, Learning and memory); Overactivity may cause epileptic seizures
NMDA receptors
Chloride ion-channel linked [Effect on cell membrane?]; Barbiturates bind to this = Sedation, Decrease anxiety, Anticonvulsants for treating seizures
GABA - A receptors
G-protein mediated; Linked to ion channels through 2nd messengers; opens chloride-channels
GABA - B receptors
What dopaminergic receptor types have the same effect?
D1 = same as D3, D5 D2 = same as D4
What types of beta receptors are in the heart? what is its effects when NE binds?
Beta-1; increase force and rate of contraction
beta blockers given to reduce amount of O2 needed for heart
What types of beta receptors are in the lungs? what is its effects when NE binds?
Beta-2; bronchodilation
What functions are regulated by serotonin receptors?
- Cognition
- Sleep
- Perception (including pain)
- Motor activity
- Mood
What are the main types of opioid receptors?
- Mu (binds morphine)
- Delta
- Kappa
What are opioid peptide receptors’ main function? where are they located?
Primary action is inhibition of slow pain information; Location = hypothalamus, spinal cord, and periaqueductal gray
What are the ADRs of opioids?
Respiratory depression and slows GI (constipation)
What drug is used to treat parkinson’s disease?
l-DOPA (increases the amount of dopamine that gets made, side effect can be psychosis due to too much dopamine)
What drug is an example that prevents catecholamines to be stored into vesicles?
Reserpine
What is a commonly used drug that blocks neurotransmitter release?
Botulinum toxin aka BOTOX (irreversibly binds to vesicles, and prevents them from releasing ACh at NMJ)
How does the effect of botox go away?
The neural system makes new presynaptic terminals that branch off the old inactive terminal
What’s important to remember as a PT when working with pts who get botox?
You want to work with them right away so you can raise level of functionality when the botox effect wears off
What do drugs that block neurotransmitter degradation do?
prevent neurotransmitters from being broken down so their effects last longer (i.e., MAO-I, acetylcholinesterase)
What drug is used in Parkinson’s disease that blocks the break down of dopamine (which produces free radicals) and can reduce the progression of the disease?
Monoamine oxidase inhibitors (MAO-I)
What drug is used a lot in bug sprays and pesticides (also used in nerve gas)?
Acetylcholinesterase inhibitors
What drugs act to prevent neurotransmitter reuptake?
Tricyclic antidepressants (inhibit monamine reuptake, also act at cholinergic receptors) and Selective Serotonin Reuptake Inhibitors (prozac)
Antibodies are produced against voltage-gated calcium channel of the neuromuscular junction;Antibodies block calcium entry into presynaptic terminal; Mostly seen in patients with cancer, usually small cell carcinoma of the lung
Lambert-Eaton Syndrome
What affect does lambert-eaton syndrome have on ACh release and muscle strength?
Decrease in ACh release and decrease in strength
Disease where antibodies bind to the nicotinic acetylcholine receptor; Antibody blocks the effect of ACh on the muscle = increasing weakness seen with repeated use of a muscle; Initial sign in about 50% of patients is weakness opening eyelids/moving eyes
Myasthenia gravis
With myasthenia graves, there is weakness opening eyelids or moving eyes. Why?
Because we use eyes/eyelids a lot
What are common treatments of myasthenia gravis?
- Acetylcholinesterase inhibitors
- Removal of thymus gland (repress production of antibodies)
- Immunosuppressive drugs (repress reproduction of antibodies)
- Plasmapheresis: removes antibodies
