73. Introduction to the Autonomic Nervous System Flashcards
The nervous system can be divided into 2
Central and Peripheral (CNS and PNS)
what do we say when a signal is going towards the CNS
afferent
what do we say when a signal is going away from the CNS
efferent
PNS is split into 3 sections
Somatic efferent
Autonomic
Somatic afferent
the autonomic nervous system is split into 3
Sympathetic
Parasympathetic
Enteric
what is the overall function of the autonomic nervous system
mediates output from the CNS to the whole of the body, with the exception of skeletal (voluntary) muscle
Output is modulated by external and internal sensory input, often via reflexes involving negative feedback loops within PNS and the CNS
ANS regulates functions which are…
essential
do not require conscious effort
largely involuntary
examples - heart beat, metabolism, exo/endocrine secretions
Two neurons in series are described
preganglionic and postganglionic
why do the Sympathetic and parasympathetic divisions of the ANS often work simultaneously
to maintain homeostasis
Sympathetic is what kind of response
fight or flight and energy consuming
Parasympathetic is what kind of response
rest and digest
restorative
energy conserving
The transmitter of the preganglionic neurons, sympathetic and parasympathetic, is always what
acetylcholine (ACh)
what does acetylcholine (ACh) act on
excitatory nicotinic cholinoceptors
describe the chemical transmission of the ANS sympathetic division
- Action potential originates from the CNS
- Travels to the presynaptic terminal of the preganglionic neuron
- Triggering Ca2+ entry through voltage-gated, calcium selective, ion channels and the release of Ach by exocytosis.
- ACh binds to and opens ligand-gated ion channels (nicotinic ACh receptors) in the postganglionic neuron
- Causing depolarization and the initiation of action potentials that propagate to the postsynaptic presynaptic terminal of the neuron
- Triggering Ca2+ entry and the release, usually, of noradrenaline.
- Noradrenaline activates G-protein-coupled adrenoceptors in the effector cell membrane to cause a cellular response
SNS where does the action potential travel to on the neuron
presynaptic terminal on the preganglionic neuron
SNS when the action potential travels to the presynaptic terminal on the preganglionic neuron, what does this cause?
Ca2+ entry through voltage-gated, calcium selective, ion channels
SNS when Ca2+ enters through voltage-gated, calcium selective, ion channels what does this cause
the release of ACh by endocytosis
SNS after the release of ACh by endocytosis from the preganglionic neuron what happens and where?
ACh binds to and opens ligand-gated ion channels (nicotinic ACh receptors) in the postganglionic neuron
SNS when ACh binds to and opens ligand-gated ion channels (nicotinic ACh receptors) in the postganglionic neuron. what does this cause?
depolarization and the action potential to continue
SNS once depolarization and the action potential continuing occurs in the postganglionic neuron it travels down to the presynaptic terminal to do what which releases what
to trigger the entry of Ca2+ which causes the release of Noradrenaline
SNS Once Noradrenaline is released it activates…..
G protein coupled adrenoreceptors in the effector cells causing a cellular response
This is the same process for parasympathetic except what is released from the postganglionic neuron
Acetylcholine ACh
and in the parasympathetic system what does the postganglionic acetylcholine activate
G protein coupled muscarinic acetylcholine receptors
what is the transmission called when neither NA or ACh are used
NANC - Non-Adrenic Non-cholineric transmission
In NANC - Non-Adrenic Non-cholineric transmission. Which neurotransmittors are used instead for parasympathetic and sympathetic
Parasympathetic - NO & VIP
sympathetic - ATP & NPY
ACh - Classical Receptor Classes of the Ganglia and Effector Cells (Cholinoceptors). Name the 2 types
Nicotinic and Muscarinic
describe Nicotinic ACh receptors
Ligand-gated ion channels (LGICs),
Structurally and pharmacologically distinct from nicotinic receptors at the skeletal neuromuscular junction, or in the CNS
describe muscarinic ACh receptors
G-protein-coupled receptors (GPCRs)
describe muscarinic ACh receptors in their 5 subtypes
five subtypes: M1, M2, M3, M4 and M5 that are differentially expressed across tissues/organs
out of the five muscarnic ACh receptor subtypes. why are the most important
M1-M3
NA and adrenaline (A) are the endogenous agonists all bind to
G protein coupled receptors
Out of Ach, VIP and NO which neurotransmitter starts a rapid, intermediate and slow response
Ach is fast
NO is intermediate
VIP is slow
Out of NA, ATP and NPY which neurotransmitter starts a rapid, intermediate and slow response
ATP is fast
NA is intermediate
NPY is slow
M1 - describe
Gq
stimulates phospholipase C
increases stomach acid production
M2 describe
Gi
inhibition of adenylyl cyclase and opening of K+ channels
decrease HR
M3 describe
Gq
stimulates phospholipase C
Increases salvia mucus production and constricts lungs
