Chapter 2: The Neuron, Synaptic Transmission, and Neurotransmitters Flashcards
Human Nervous System Consists of Two Divisions?
- Central nervous system (CNS)
-brain and spinal cord - Peripheral nervous system (PNS)
-nerves that originate in the spinal cord and connect to organs in the body
-contains automatic and sympathetic nervous systems
-should pay attention to effects of drugs on autonomic nervous system
most drugs block effects of which system?
parasympathetic nervous system
what is the function of the Spinal Cord?
Made up of neurons and fiber tracts that:
-sensory information
-motor output flow
-provide autonomic (involuntary) control of vital body organs
-contains the reflex arc
three neurons in reflex arc?
- Inner Neuron- connects horns
- Sensory Neuron
- Motor Output Neurons
Primary divisions of the brain?
- Hindbrain
- Midbrain
- Forebrain
what is the definition of the spinal cord?
Information highway of structures/messages sent back and forth from spinal cord to rest of body
how are human brain more evolved than other mammals?
it is not that our brains are different but rather we have tighter control over the same functions
what is The brain stem ?
the portion of the brain consisting of the medulla, pons, and midbrain, which connects the spinal cord to the forebrain
what is the cerebellum?
Behind the brain stem is a large, bulbous structure—the cerebellum. A highly convoluted structure, the cerebellum is connected to the brain stem by large nerve tracts. The cerebellum is necessary for the proper integration of movement and posture.
most of the drugs effect which portions of the brain?
the lower brain systems
including the side effects on the para/sympathic nervous systems as well
Most of neurons in which nuceli contain dopamine?
substantia nigra and ventral tegmental area (VTA) in the forebrain
What is the Limbic System?
Second major subdivision of the telencephalon
Amygdala and the hippocampus
Contributes to regulation of mood, affect, emotion, responses to emotional experiences
Reward circuit
which two cells make up the Central nervous system?
- Neurons
- Non-Neural Cells aka GLIAL cells
Each occupy about 50% of the volume
However, there are 10x more glial cells because they are 1/10the the size of neurons
explain functions of each of the glial cells.
- oligodendrocytes
-providing myelin
-in communications with the axons, shuttling lactate back to the axon for respiratory processes - astrocytes
-forming blood brain barrier
-supports neurons by soaking up toxic compounds around cytoplasm - microglial cells (or ependymal)
-acts as a immune system for the CNS despite the CNS not really having one
How do we get neurotransmitters?
Through Synthesis
(by altering or building upon simpler molecules)
What is synthesis?
Formation of transmitters
STEPS:
1. Precursors are the main ingredient
-Brought to the neuron by the bloodstream
-Taken up by cell body and/or terminal
- Enzymes put the ingredients together
-converted from amino acid into neurotransmitter
what are the precursors to neurotransmitters? how do they get into the CNS?
amino acid
they get in through transportation because they are large molecules which are polar
what are the 3 parts of a neuron?
- cell body (soma)
-endoplasmic reticulum (folded membranes, smooth/rough)
-nucleus (DNA)
-ribosomes (transport genetic codes)
-mitochondria
-cytoplasm (jelly like substance)
-golgi complex (modifies and packages neurons) - dendrites
-specialized RECIEVING apparatus of the cell
-contains receptors - axon
-transmitting apparatus of the cell
-usually branches into many terminals
-can be myelinated or unmyelinated
what are receptors?
protein complexes that cross the membrane
THOUSANDS across cell surface
all inputs are being summed as an electrical potential of the axon helic (the point at which the axon leaves the cell body) these are the electrical channels which start the channel
what allows for fast transportation between the myelin?
the gaps or nodes
-needed to regenerate the action potential
-fast transmission
it is efficient to only need to pump ions in the gaps rather than the entire myelin (unmyelinated axons do not have this)
illustrate the basics of synaptic transmission.
- action potential is transmitted down axon to presynaptic terminal
- the depolarization at the presynaptic terminal opens ion channels for calcium to enter ion
- calcium enters vessles (containing neurotransmitters) to fuse with membrane and open/release transmitter molecules into the synaptic cleft
- After release, neurotransmitter molecules bind to and activate receptors on the pre- and postsynaptic membrane (entirely based on diffusion)
- Transmitter effects are terminated either by breakdown of transmitter within the synaptic cleft or by reuptake back into the axon terminal to be recycled
how are neurotransmitters released into vesicles?
through process of Exocytosis
where Vesicles fuse with presynaptic membrane and release transmitters into the synapse
what is known as “binding”?
Attachment of transmitter to receptor
Different Varieties of Neurotransmitter Receptors?
- Ionotropic
-ion channel
-fast response - Metabotropic, or G protein-coupled
-Initiates a second signal (messenger) inside the neuron
-do not form ion pore
Different Inactivations/Terminations of Synaptic Transmission?
- Metabolism
-enzymes in synapse that break transmitter down - Re-uptake
-transporter proteins transport it back
these processes help terminate the signal and cell to conserve energy by allowing recycling
how is glutamate handled in extracellular fluid?
taken up by astrocytes
what is meant by Receptor Specificity?
Each receptor is specific for a particular neurotransmitter
Each neurotransmitter binds to several receptor subtypes which can produce different effects
how does the neuron communicate across the synapse?
scientists have been divided by it being either electrical or neurochemical.
it was shown to be neurochemical
first neurotransmitter to meet the defined criteria? what is it?
Acetylcholine (ACh)
-easiest to study
-found in CNS, synapses in sympathetic systems, neuromuscular junction
-via choline from diet
describe the Acetylcholine (ACh) Synapse.
ACh is made in the axon terminal from acetyl coenzyme A (acetyl CoA) and choline and stored in vesicles for release.
After release, ACh binds to its receptors and is immediately broken down at the receptors by acetylcholinesterase (AChE) into choline and acetate.
the 2 Cholinergic Receptors?
- Nicotinic
-very fast - Muscarinic
-not fast
Where Is ACh Produced?
(1) The forebrain cholinergic complex composed of neurons in the medial septal nucleus and nucleus basalis which projects to the telencephalon
(2) the midbrain cholinergic complex, composed of cells in the pedunculopontine and laterodorsal tegmental nuclei, which ascends to the thalamus and other diencephalic loci (not shown) and descends to the pons, medulla, cerebellum, and cranial nerve nuclei.