PharmacologyANS Flashcards
Breakdown of Peripheral NS
- Sensory neurons and motor neurons
- Motor neurons have somatic, autonomic and enteric (腸の)NS
Effectors (muscle/glands) for somatic NS
skeletal muscle
Effectors (muscle/glands) for autonomic NS
smooth and cardiac muscle, glands
Effectors (muscle/glands) for enteric NS
fx: gastrointestinal innervation
smooth muscle, glands and endocrine cells of GI tract
NT released from CNS
Ach, nicotinic Ach ONLY!!!
NT released in parasympathetic NS
CNS -Ach(nic)—Ach(mus)—> salivary glands etc
NT released in sympathetic NS
CNS -Ach(nic)—NA—> blood vessels etc (most common)
CNS -Ach(nic)—Ach(mus)—> sweat glands etc
CNS -Ach(nic)——> adrenal medulla
α-, ß1- or ß2-adrenoceptors
Deactivation by reuptake
Adrenaline can be directly released from adrenal medulla
Ach deactivation by
acetylcholinesterase
What’s special about penis regarding NT?
cavernous nerves release nitric oxide (NO) in the penis.
- relaxes the smooth muscle of the corpora cavernosa via cyclic guanosine monophosphate allowing expansion of the lacunar spaces and erection
All the preganglionic nerve fibres
(for both sympathetic and parasympathetic) are myelinated and release acetylcholine from the nerve terminals
How is (post)ganglionic neurons activated?
Ach depolarizes the ganglionic neurons by activating nicotinic receptors
Afferent sensory fibres carry info to
centers in the hypothalamus and
medulla
IG: What is the drug for erectile dysfunction
Sildenafil, used in male sexual dysfunction, inhibits phosphodiesterase type 5 and, by increasing the concentration of cGMP, facilitates erection.
Sympathetic NS characteristics
- Sympathetic from thoracolumbar region (T1-L3)
- synapse either in the paravertebral ganglia or in the prevertebral ganglia and plexuses in the abdominal cavity
Parasympathetic NS characteristics
- the preganglionic fibers leave the central nervous system via the cranial nerves (especially Ill, VII, IX and X) and the third and fourth sacral spinal roots.
- often travel much further than sympathetic fibers before synapsing in ganglia, which are often in the target regions itself
How do agonist-R complex get activated?
AR + transducer -> ART*
arrow represents intrinsic efficacy (Kar)
What is Ach released from and its effect?
- All preganglionic autonomic nerves (i.e. both sympathetic and parasympathetic).
- Some postganglionic sympathetic nerves (i.e. thermoregulatory sweat glands and skeletal muscle vasodilator fibres).
- Nerve to the adrenal medulla.
- Somatic motor nerves to skeletal muscle endplates. Some neurones in the central nervous system.
Effect:
vasodilation
bradycardia (slow down of heart rate)
Ach R/cholinoceptors
2 subtypes
1) nicotinic … determined by measuring the sensitivity of various tissues to the drugs nicotine (ligand gated)
2) muscarinic … determined by measuring the sensitivity of various tissues to the drugs muscarine (GPCR)
Postganglionic relationship between NA and Ach
NA (sympathetic) and Ach (para) negatively linked to each other
=> inhibitory effect of adrenaline on acetylcholine release
Tissue response (slow/medium/fast) depending on NT from para and sym
from para/sym
slow VIP/NPY
medium NO/NA
fast Ach/ATP
Many noradrenergic and cholinergic terminals have
presynaptic inhibition
meaning NT excites to other place but have negative feedback to its own NT release (self regulated)
IG: Noradrenergic/cholinergic terminals in heart
heterotropic presynaptic inhibition
meaning neurotransmitter X andY give negative feedback to each other while X stimulate another place and Y inhibit the same place (X and Y fight)
IG: Postsynaptic Synergism example
examples of non-adrenergic+ non-cholinergic (co-)transmitters
1)Noradrenaline/NPY in blood vessels
X excite a target, Y positively excites it too
2)Noradrenaline/ATP in blood vessels
Ach/GnRH in sympathetic ganglia
Ach/SP in enteric ganglia
One NT X have fast response, while Y have slower response to the same target
3) Ach/VIP in salivary gland
X excites target A (glands), Y excites target B (blood vessel)
Types of parasympathetic drugs
parasympathomimetics (increase Ach activity)
and parasympatholytics (decrease)
can act directly or indirectly
Atropine
muscarinic receptor blocker
Muscarinic receptor
- Mostly founds on glands and are dose dependent
- The effects of acetylcholine are usually excitatory, but an important exception is the heart, which receives inhibitory cholinergic fibers from the vagus.
Parasympathetic drugs
Drugs that mimic the effects of acetylcholine are called cholinomimetics and can be divided into two groups: drugs that act directly on receptors (nicotinic and muscarinic agonists); and anticholinesterases, which inhibit acetylcholinesterase and so act indirectly by allowing acetylcholine to accumulate in the synapse and produce its effects.