Chapter 2: Structure and Function of NS/ Chapter 3: Chemical Signaling Flashcards
Autonomic Nervous System
Sympathetic- thoracic and lumbar autonomic nerves (sensory and motor)
Parasympathetic- sacral autonomic nerves and cranial nerves (sensory and motor)
Somatic Nervous System
spinal and cranial nerves- motor and sensory nerves
Embryonic Development
Forebrain –> telencephalon, diencephalon
Midbrain –> mesencephalon
Hindbrain –> metencephalon, myelencephalon
Telencephalon
neocortex
basal ganglia
limbic system
Diencephalon
thalamus
hypothalamus
Metencephalon
cerebellum
pons
Myelencephalon
medulla
Physiological Response to Stress
picture on phone
Synthesis, Release, and Inactivation
- Synthesis
- A+B–> NT (with help of enzymes)
- stored in vesicles - Release
- Receptor Activation
- Intracellular signaling
- ionotropic
- metabotropic - Inactivation
- degradation (using enzymes in synapse)
- reuptake (more common)
3 classes of neurotransmitter
- small molecule NT (about the size of amino acid)
- peptide NT (3-40 amino acids put together)
- unconventional NT
Small molecule NT
- Acetylcholine
- Amino Acids: glutamate, GABA
- Biogenic Amines: serotonin, dopamine, norepinephrine, epinephrine
- Purines: adenosine, ATP
- synthesized in final form
- synthesis in NT
- enzymes localized to NT
- often a rate-limiting step
- formed in nerve terminal - site of action close to release site
- reuptake mechanism and vesicle recycling
Peptide NT
- Opioids
- Hypothalamic RF’s
- Vasopressin, Oxytocin
- synthesis of precursor
- synthesis required in soma
- transcription, translation
- transport to NT - site of action often distant from release site
- released into blood - enzymatic termination, no vesicle recycling
The synaptic vesicle cycle
- vesicles are constantly being recycled
- exocytosis:
- mobilization, docking/ priming, fusion/ release - endocytosis:
- clathrin- mediated
- clathrin- independent (faster)
- incomplete fusion (kiss- and- run)
Unconventional NTs
- not stored in vesicles
- not released by exocytosis
- signaling still depends on Ca2+ to initiate signals
- nitric oxide (NO): gas
- endocannabinoids: fatty acids
Autoreceptors
- a receptor for the same transmitter released by the axon
- terminal autoreceptors (on nerve terminal)
- release- modulating: inhibitory - somatodendritic
- activity modulating: like postsynaptic receptors
ex. 5-HT receptor on 5-HT releasing receptor
2 primary mechanisms inactivate neurotransmission
enzymatic breakdown
reuptake
Enzymatic Breakdown
- in the synapse (AChE)
- in the nerve terminal (MAO, COMT)
- in blood (peptidases)
Reuptake
- energy dependent pumps move transmitter
- into the nerve terminal
- into glia
- eg. glutamate, GABA
Ionotropic Receptors
ligand-gated ion channels
- fast transmission
- no intermediate chemical steps
- directly changes membrane permeability
- 5 subunits surrounding pore
Metabotropic Receptors
G protein-coupled receptor
- slow activation, long-lasting effects
- alters intracellular biochemistry
- 7 membrane spanning coils
- NT binding sites
Cyclic AMP system
Effector- adenylyl cyclase
2nd messenger- cAMP
Kinase- PKA
Phospholipase C system
Effector- PLC
2nd messenger- IP3, DAG
Kinase- PKC
Other types of receptors
Tyrosine kinase- growth factor
Steroid hormone- intracellular
Nerve Synapse
Synthesis:
- drug serves as NT precursor
- drug inhibits NT synthesis
- drug prevents storage of NT in vesicles
Release:
- drug stimulates release of NT
- drug inhibits release of NT
Receptors:
- drug stimulates postsynaptic receptors
- drug blocks postsynaptic receptors
Release:
- drug stimulates autoreceptors; inhibits release of NT
- drug blocks autoreceptors; increases releases of NT
Inactivation:
- drug inhibits NT degradation
- drug blocks reuptake
