DENT Fun. I - Neurotransmitters

Neurotransmitters

Chemical messengers that cross the synaptic gaps between neurons

Peripheral Nervous System (PNS)

The sensory and motor neurons that connect the central nervous system to the rest of the body

What are the 2 subdivisions of the PNS?

- Somatic

- Autonomic

Somatic Nervous System

The division of the peripheral nervous system that controls the body's skeletal muscles via motor units

Autonomic Nervous System (ANS)

The part of the PNS that regulate the basic visceral processes of the body such as the glands and muscles of the internal organs

What are the 3 divisions of the ANS?

- Sympathetic

- Parasympathetic

- Enteric

Sympathetic Nervous System (SNS)

The component of the ANS that responds to stressful situations by initiating the fight-or-flight response via Epinephrine (E) and Norepinephrine (NE)

Parasympathetic Nervous System (PNS)

Division of the ANS that slows down body functions ("Rest & Digest") via ACh

Enteric Nervous System (ENS)

Division of the ANS located in the digestive system; Regulates secretions and intake

Central Nervous System

Brain and spinal cord

What are the 3 types of Neurons?

- Sensory

- Interneuron

- Motor

What are the 4 functional regions of Neurons?

- Input: Dendrites

- Integrative: Through Soma/Cell Body

- Conductive: Down Axon

- Output: NTs at Axon terminus

Reflex

- A simple, automatic response to a sensory stimulus, such as the knee-jerk response

- Typically just involves a sensory neuron and motor neuron

Electrical Synapses

- Synapses that transmit information via the direct flow of electrical current at gap junctions

- Very fast and bidirectional

Electrical Synapses are typically found in ____ and ____ muscle.

cardiac/smooth

Chemical Synapses

- Synapses that transmit information via the secretion of NTs

- Unidirectional

Action of a NT is dependent on the properties of the ____.

postsynaptic receptor

What are the 2 means of removing NTs from the synaptic cleft?

- Reuptake

- Enzymatic Degradation

What are the 2 features of Receptors?

- They are membrane spanning proteins

- They carry out an effector function

Ionotropic Receptors

Ligand-Gated Ion Channels

Metabotropic Receptors

- Receptors that are associated with signal proteins and G proteins

- Initiate a secondary messenger system

Excitatory Receptors

Cause depolarization of the postsynaptic neuron

Inhibitory Receptors

Cause postsynaptic cell to hyperpolarize

G-Protein Coupled Receptors are ____ than Ionotropic Receptors.

slower

Few extra steps

Neurotransmitter Release Process

(1) Synthesis and Storage of NTs

(2) Action Potential travels to Presynaptic Terminal

(3) Voltage-Gated Ca2+ Channels open

(4) Ca2+ allows vesicle docking via SNAREs and NT release

(5) NTs bind postsynaptic receptors

(6) Removal of NTs via enzymes or reuptake

SNAREs

Ca2+ dependent complexes that fuse NT vesicles to the presynaptic membrane to release NTs

EPSPs

Excitatory Postsynaptic Potentials

- Depolarize via Na+ Channels

- Typically mediated by Glutamate

IPSPs

Inhibitory Postsynaptic Potentials

- Hyperpolarize via Cl- Channels

- Typically mediated by GABA or Glycine

What are the 2 main classes of NTs?

- Small

- Large

Small Molecule NTs

- Amino Acids (Glutamate, GABA, Glycine)

- Monoamines (NE, E, Serotonin, Dopamine)

- ACh

Large Molecule NTs (Neuropeptides)

Small polypeptides that range from 3-36 amino acids

Dopamine, NE, and E all derive from ____.

Tyrosine

ACh derives from ____.

Choline

Aminobutryic Acid (GABA) derives from ____.

Glutamine

The PNS consists of ____ neurons.

cholinergic

Motor Unit

All muscle fibers that are controlled by a single motor neuron

Neuromuscular Junction (NMJ)

Synapse between the axon terminal of a motor neuron and a skeletal muscle cell

AChE

Acetylcholinesterase

- Degrades ACh

Botulinum Toxin

Inhibits ACh release

Myasthenia gravis

Chronic autoimmune disease that creates antibodies that attack the cholinergic receptors of the NMJ and produces serious weakness of voluntary muscles

Glutamine

Excitatory NT

GABA

Inhibitory NT that hyperpolarizes the cell via Cl- Channels

Glycine

Inhibitory NT that hyperpolarizes the cell via Cl- Channels