Unit 3: divisions of the NS Flashcards
what is autonomic pharmacology
- drugs designed to enhance or minic the autonomic nervous system or block effects of neutrotrasnmitters at their receptor sites
division of the nervous system
- peripheral and central
PNS
- all nerves travelling between the CNS and somatic and visceral sites
- contains autonomic (involuntary) NS and sensory and somatic (voluntary NS)
CNS
- includes cerebrum, diencephalon, berebellum, brainstem and spinal cord
- relays and processes signals from the PNS, responses are relayed back to periphery
- responsible for movement, perception ie snesory, auditory, and visual (wake, language, consciousness)
branches of ANS, what they are responsible for, newuro transmitters and their receptors
- regulates involuntary responses of smooth muscle and glandular tissue
- parasympathetic and sympathetic which often have opposing effects to one another
parasympathetic
- responsible for conservation of body processes (rest and digest)
- main neurotransmitter = acetylcholine
- receptors = muscarinic and nicotinic
Sympathetic
- emergency situations, fight or flight
- main neurotransmitter = epinoephrine and norepinephrine
- receptors at alpha and beta receptors
most organs receive input from both the PSNS and SNS, what are the exceptions?
- adrenla galnds, sweat glands, pilomotor muscles, blood vessels)
how do autonomic nerve fibers interact with their target organs?
- two neuron pathway
- first neuron originates in the brainstem or spinal chord = preganglionic neuron
- the preganglionic neuron synapses outside the spinal chord with the postganglionic neuron that innvervates the target organ
describe the patterns of the sympathetic and parasympathetic innervations
- sympatheic neurons arise in the thoracic and lumbar segments of the spinal chord
- sympathetic preganglionic neurons porject onto postganglionic neurons in ganglia that lie close to the spinal chord, most notably the paravertebral ganglia and the prevertebral ganglia located near the aorta
- Parasympathetic ganlia typically lie close to the organs they innervate
** parasympathetic preganglionic neurons which arise in nucei in the brainstem and the sacral segments of the spinal chord are generally long and proejct onto short postganglionic neurons
compare the SNS and PSNS: where are the ganglia, how long are the pre/post ganglionic fibers, whats ratio of pre:post?
neurons of the PNS only realse two neurotransmitters which are ____
acetylcholine and norepinephrine
neurons are the two classifications of neurons that release the neurotransmitters of the PNS
- cholinergic neurons: release acetylcholine
- adrenergic neurons: release norepinephrine or epinephrine
what neurons release acetylcholine, what neurons release norepinephrine
- sympathetic and parasympathetic preganglionic neurons, parasympathetic postganglionic neurons, somatic motor neurons and sympathetic postganglionic neurons that innervate sweat glands
- all other sympathetic postganglionic neurons release norepinephrine
what receptors does acetylcholine stimulate
- nicotinic acetylcholine receptors on sympathetic and parasympathetic postganglionic neurons and at neuromuscular junction
- stimulates muscarinic acetylcholine receptors on sweat glands and on tissues innervated by parasympathetic neurons
what receptors does norepinephrine stimulate
- alpha and beta adrenergic receptors on tissues (except sweat glands) innervated by sympathetic postganglionic neurons
Describe parasympathetic outflow
describe sympathetic outflow
what are somatic nerves?
- nerves that control skeletal muscle voluntary movements do not have preganglionic and postganglionic neurons
- onely has one neuron and it releases Ach
- this binds to a nicotinic receptor at the neuromuscular junction
describe the preganglionic neuron
- both sympathetic and parasympathetic preganglionic neurons release Ach
- all Ach released by preganglionic neurons binds to nicotinic receptor
describe Postganglionic neurons
Sympathetic system
- sympathetic nerve that innervates sweat glands release acetylcholine binding to muscarinic receptor
- all other sympathetic nerves release norepinephrine binding to alpha or beta adrenergic receptors
** one exception is that sympathetic outflow that innervates sweat glands releases acetylcholine at postganglionic axon and binds to muscarinic receptor
Parasympathetic
- all parasmpathetic nerves release acetylcholine bidning to post ganglionic muscarinic receptor
what are the steps in synaptic transmission
- Neuron synthesizes neurotransmitters from precursors and stores the transmitter in vesicles
- Action potential travelS down the neuron, depolarizes the presynaptic nerve terminal
- Membrane depolarization activates voltage-dependent Ca2+ channels, calcium enters into the presynaptic nerve terminal
- increased cytosolic calcium enables vesicle fusion with the plasma membrane of the presynaptic neuron, neurotransmitters will be released to synaptic cleft
- Neurotransmitters diffuse across synaptic cleft and bind to postsynaptic receptors
- Binding to inotropic receptor -> channel opening and changes the permeability of the postsynaptic membrane to ions -> changes postsynaptic membrane potential
- Binding to metabotropic receptor -> activate intracellular signaling cascade (e.g.GPCR cascade leading to the formation of cAMP by adenylyl cyclase) -> this signaling cascade may activate other ion-selective channels
- Signal termination is accomplished by removal of transmitter from the synaptic cleft by cell reuptake transporters
- Signal termination can also be accomplished by enzymes (e.g. phosphodiesterase) that degrade postsynaptic intracellular signaling molecules (e.g. cAMP)
