Part III Neural Communication-Synapse, CH. 7
Excitatory Neurotransmitters
-Cause depolarization by EPSPs and promote action potential generation -Contains Glutamate
Inhibitory neurotransmitters
-Cause hyperpolarization by IPSPs and inhibit action potential generation. -Contains Gycline and GABA
Monoamines
Group of regulatory molecules that include epinephrine, norepinephrine, dopamine, and serotonin. Use a second messenger such as cyclic AMP
Step six in neurotransmitter ACh release
If depolarization reaches threshold, an action potential forms on the postsynaptic membrane
Step five in neurotransmitter ACh release
If it is a muscle cell, ACh binds with and opens ligand gated Na+ channels and Na+ diffuses into the muscle cell causing a graded depolarization.
Presynaptic and Postsynaptic
Impulses pass from the _________ neuron to the ________neuron.
Gylcine
Inhibitory neurotransmitter that is located in the spinal cord and brain
Acetate
Is absorbed and used to make more ACh or for energy by cells in the area.
Choline
Is absorbed by the synaptic end bulb and used to synthesize more ACh.
true
True or False: Monoamines: Group of regulatory molecules that include epinephrine, norepinephrine, dopamine, and serotonin
False, produces IPSP (inhibitory postsynaptic potential)
True or False: When muscarinic receptors on pacemaker cells get activated cell becomes hyperpolarized, producing an excitatory postsynaptic potential (EPSP) and the heart rate slows.
Nicotinic acetylcholine receptors Muscarinic acetylcholine receptors
Two main classes of cholinergic receptors
Glutamate
Type of neurotransmitter found in the brain and spinal cord that is always excitatory
Glycine
Type of neurotransmitter found in the brain and spinal cord that is always inhibitory
Monoamine Oxidase Inhibitors
Used in treatment of depression because they keep the amount of monoamines in the high synapse high and thus promote their effectiveness.
Black Widow Spider Venom
Venom triggers explosive release of ACH from storage vesicles at the neuromuscular junction and all cholinergic sites. Can cause nausea, cramps, lack of coordination, and difficulty breathing.
Anticholinesterases (neostigmine or physostigmine)
What is Myasthenia Gravis treated with ?
Inhibits
When a person has Botulism the toxin _________ acetylcholine release at the neuromuscular junctions
K+/K+
When muscarinic receptors on pacemaker cells get activated the G-protein dissociates and activates _______ channels to open leading to the diffusion of _________ out of the cardiac cell.
curare
Which of the following binds to and blocks acetylcholine receptors at the neuromuscular junction causing flaccid paralysis?
botulinum toxin
Which of the following inhibits acetylcholine release at the neuromuscular junction causing flaccid paralysis?
Neuroglandular junction
synapse between a neuron and a glandular cell.
Inactivation of monoamines
-Re-uptake into presynaptic neuron endings. - Enzymatic degradation in presynaptic neuron by monoamine oxidase, can also degrade in the synaptic cleft
How muscarinic ACh receptors slow our heart rate
-Vagus nerve synapses with cardiac pacemaker cells and releases ACh that binds to muscarinic receptors. -G-protein dissociates and activated K+ channels to open leading diffusion of k+out of the cardiac cell. -The cell becomes hyperpolarized, producing an IPSP and the heart rate slows.
Botulism
A form of food poisoning caused by botulinum toxins.
EPSP (excitatory postsynaptic potential)
A graded depolarization of the postsynaptic membrane which moves the membrane potential toward threshold.
IPSP (Inhibitory postsynaptic potential)
A graded hyperpolarization of the postsynaptic membrane, making it more difficult for the postsynaptic cell to reach threshold.
Ligand
A molecule that binds with a receptor protein
Acetylcholine Receptors
A neurotransmitter receptor that responds to ACh are called cholinergic receptors. Can be excitatory or inhibitory.
Acetylcholinesterase activity
A number of pesticides and nerve gas work by inhibiting ____________?
Muscarinic ACh receptors
A type of GPCR found in heart and function to slow heart rate.
Step seven in neurotransmitter ACh release
ACh is broken down to acetate and choline by the enzyme Acetlycholinesterase, which is located on the postsynaptic membrane.
Acetylcholinesterase
ACh is broken down to acetate and choline by what enzyme?
Final step in neurotransmitter ACh release
ACh will continue to be released until APs cease at the synaptic end bulb. Calcium channels close and the calcium is pumped out of the synaptic end bulb, which stops the release of ACh. i
Postsynaptic membrane
Acetylcholinesterase (AChE) is located on or in the
Step four in neurotransmitter ACh release
Ach diffuses across the synaptic cleft and binds with the ion channels on the postsynaptic membrane ( neuron, gland, muscle).
Cyclic AMP
Activates the enzyme protein kinase, which functions to phosphorylate energy phosphate group and other proteins.
Tubocurarine
Active ingrediant of Curare. - Used to poison in blow darts and arrows by South American Indians to paralyze their prey.
G Protein Complex
Attached to the ligand gated receptor and consists of 3 subunits designated to alpha, beta, and gamma.
Myasthenia Gravis
Autoimmune disease where antibodies block and destroy ACh receptors on the neuromuscular junctions, results in progressive weakening of the skeletal muscles from less acetylcholine receptors
Antidepressant drug functions
Block the re-uptake of serotonin into the presynaptic endings, and thereby increase the effectiveness of serotonin at the synapse.
Cocaine
Blocks the re-uptake transporters for dopamine, norepinephrine, and serotonin resulting in continual stimulation.
True
Caffeine vasoconstricts arteries true/false?
Electrical Synapse
Cells have no space between them-are physically connected which allow for stimulation that is direct.
ACH receptors
Curare based drugs are often used during surgery to relax skeletal muscles. What do they bind to and block?
Step two in neurotransmitter ACh release
Depolarization causes voltage gated calcium channels to open and extracellular calcium ions enter the axon terminal.
Serotonin
Derived from amino acid tryptophan
neurotransmitter
Effects of a _____________ on the postsynaptic membrane depends on the properties of the receptor and not on the nature of the neurotransmitter
G protein coupled
Eighty percent of prescription drugs target.....
Glutemate
Excitatory neurotransmitter located in the brain and spinal cord. Important in learning memory and allows Na+ and or Ca+ to enter the postsynaptic cell.
Gap Junctions
Presynaptic and postsynaptic membranes are locked together at...
Tetrodotoxin
Found in pufferfish, blocks voltage gated Na+ channels. Also causes muscle paralysis and could lead to death by asphyxiation.
Electrical Synapse
Found in the CNS and PNS, but rare; present in cardiac, some smooth muscle cells and some neurons in the brain.
Adenosine (see pg 11)
Generated by metabolically active neurons and glial cells which increase the extracellular concentration of adenosine the longer you are awake.
G protein
Ligand gated receptors that contain a G protein complex that when stimulated, activate intracellular signaling pathways.
Fugu
Made by pufferfish, but poison is removed. The poison is found in the ovaries and liver.
Spatial Summation
Many neurons release neurotransmitters on a single postsynaptic neuron - A number of synapse are active at the same time and the graded depolarization spreads rapidly across the postsynaptic membrane to reach threshold action potential.
Botox
Medically used for : -Facial wrinkles -severe underarm sweating -cervical dystonia -Blepharospasm- uncontrolled blinking Strabismus- Misangled eyes
Chemical synapse
Most abundant type of stnapse
Types of chemical synapses
Neuromuscular junction Neuroglandular junction Neuron-neuron synapses
Chemical synapse
Neurotransmitters are released from the presynaptic axon terminals at structures called the terminal boutons. The Neurotransmitters
GABA
Principle inhibitory neurotransmitter in the brain. Effects augmented by alcohol and allows Cl- to enter the postsynaptic cell Remember that the function of a neurotransmitter is determined by the receptor to which it binds.
Selective serotonin reuptake inhibitors drugs (SSRIS)
Prozac, Paxil, & Zoloft
Serotonin function
Regulation in mood
EPSP
Results from opening ligand gated channels allowing positive ions to move into the cell (Na+ or Ca2+) Also can reach action potential if threshold is reached.
IPSP
Results from opening ligand gated ion channels in the membrane such as K+ moving out or Cl- moving in channels. Also responsible for postsynaptic inhibition
Muscarinic ACh Receptors
Simulated by ACh and by muscarine (poison in some mushrooms). Inhibited by atropine
Nicotine ACh Receptors
Simulated by ACh and by nicotine. Inhibited by curare
Temporal Summation
Single neuron releases successive waves of transmitter on a postsynaptic neuron. -Ligand channels open and the degree of graded depolarization increases.
atropine
Substance that will inhibit muscarinic receptors
curare
Substance that will inhibit nicotinic receptors
Neuromuscular Junction
Synapse between a motor neuron and a muscle fiber.
Neuron-neuron synapses
Synapse between the axon of one neuron and the dendrite cell body, or axon or a 2nd neurons.
Vagus Nerve
Synapses with cardiac pacemaker cells and releases ACH that binds to muscarinic receptors.
Hyperpolarization
Takes the membrane potential farther from threshold.
spatial summation
Term for when a single neuron releases successive waves of transmitter on a postsynaptic neuron.
temporal summation
Term for when many neurons release neurotransmitters on a single postsynaptic neuron.
Hypothalamus
The arousal system is regulated by a group of neurons in the _______________ and involves the reticular activating system originating in the brain stem.
Step one in neurotransmitter ACh release
The arrival of an action potential causes the depolarization of the synaptic end bulb.
Synapse
The junction between a neuron and a second cell, can be categorized as either an electrical or chemical synapse.
Step three in neurotransmitter ACh release
The rise in Ca+ triggers the synaptic vesicles to release acetylcholine into the synaptic cleft by exocytosis
Monoamine Oxidase Inhibitors
These inhibitors block monoamine oxidase, the enzyme that breaks down monoamine and allows for more of these neurotransmitters to be available.
Dopamine
a neurotransmitter responsible, among others, for motivation, pleasure and positive feelings. Abundance of this neurotransmitter in the brain is responsible for the pleasure effects associated with the use of cocaine.
Chemical Synapse
cells that have a space (synaptic cleft) between them and use a neurotransmitter to cross the space.
Neurotransmitters
classified as excitatory or inhibitory based on their effects on the postsynaptic membranes.
Gap Junctions
contain pores that permit the passage of ions and molecules between cells that allow two-way transmission of impulses.
Summation
integration of EPSPs and IPSPs in the postsynaptic neuron Ex: A single EPSP is usually not strong enough to result in an action potential but individual EPSPs can combine through the process of summation and cause an AP.
Caffeine
principle mode of action- blocks (antagonist) adenosine receptors in the brains arousal system