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