Autonomic Nervous System Flashcards
Ligands:
Norepinephrine
ACh
Histamine
Receptors:
B-adrenergic
Muscarinic ACh
Histamine
Know: Secondary messengers
Glycine
Most abundant neurotransmitter in the spinal cord
Mainly inhibitory
Impt in Glutamate NMDA receptor
Impt festure of EPSP and IPSP
They only become action potential when they summate
They are localized
They do not propagate
How NT are removed in the synaptic cleft?
Diffusion
Reuptake : NT reenters presynaptic terminal
Enzymatic destruction
Functions of the ANS
Maintain homeostatic conditions
Coordinate body’s responses to stress, injury, exercise
Assists endocrine system to regulate reproduction
Somatic motor neuron which directly innervates skeletal muscles
Alpha motor neurons
NT : ACh
Always excitatory
Where are preganglionic fibers found in the spinal cord?
Interomedial column
*there are also in the brainstem
Innervate effector cells (not skeletal muscles, but smooth muscle cells, gland cells, cardiac muscle cells)
Postganglionic fibers
Skeletal muscles
What type of receptors: Nicotinic
Ionotropic!
Once ACh binds, the Na ions open
Mediate the fast ganglionic EPSP
Postganglionic
Nicotinic receptors
Mediate the slow EPSP, and sometimes slow EPSP
Postganglionic
Muscarinic receptor
Sympathethic
aka Thoracolumbar and Noradrenergic System
Parasympathetic
aka Craniosacral and Cholinergic System
2 exceptions in parasympathetic
-instead of noradrenaline, ACh
1 Sweat glands
2 Blood vessels of the skeletal muscles ~ vasodilation
Difference:
Sympathetic Pre and Postganglionic
More divergence
Maraming organs (e.g. presence of adrenal medulla–> releases adrenaline and noradrenaline in the bloodstream –> stimulates organs which aren’t usually stimulated (liver- breakdown of glucose for fight and flight; platelets- have receptors for adrenaline and noradrenaline, for clotting, anti-hemorrhage)
Generalized effect
It takes a while before adrenergic NTs are degraded –> results to prolonged effect, as opposed to ACh which is easily degraded in the synaptic cleft
Parasympathetic Pre and Postganglionic
More convergence
Single organ
Localized effect
Preganglionic
Sympathetic
T1-L2
NT is ACh
Parasympathetic
S2-S4
NT is ACh
Postganglionic
Sympathetic
Prevertebral ganglia
NT is Noradrenaline
Receptor is alpha or beta adrenergic
Parasympathetic
NT is ACh
Receptor is cholinergic
Preganglionic of both Sympathetic and Parasympathetic
NT is Ach
Receptors:
Nicotinic receptors
Muscarinic
and so forth
Major NT in sympathetic: Noradrenaline and Adrenaline (both are secreted from the adrenal medulla)
In the CNS: noradrenaline/norepinephrine
In the adrenal medulla: adrenaline/epinephrine and noradrenaline but more of adrenaline
Major sources of noradrenaline
Locus coeruleus
Ventral tegmental nuclei
Alpha 2 receptors
Located in the presynaptic membrane
If inhibited, noradrenaline will be controlled, reduction of blood pressure!
B1 receptor
Big effect on the heart
B2 receptors
Big effect on the lungs
To increase ventilation
e.g. Prescribing drugs to asthmatic
Prefer Beta2 agonist, than Beta nonspecific (specific to the lungs and not sa heart)
Nucleus of the solitary tract
Major afferent neuron of the Autonomic Nervous System
Autonomic Reflexes
Baroreceptor : maintains blood pressure
-carotid sinus, carotid arch
Negative Feedback
Nucleus tractus solitarius sends signals to:
Nucleus ambiguus - lowers HR
Caudal ventrolateral medulla - inhibits rostral ventrolateral medulla (WHY?)
