Autonomic NS Flashcards
What is the autonomic nervous system?
The autonomic NS is not under the will, but automatic. It is part of both the CNS and the PNS. It can be split up in the sympathetic NS and the parasympathetic NS. Is is the opposite of the somatic NS.
What is the sympathetic NS?
The sympathetic NS is activated during short-term stress. It induce the fight and the flight mode. Some of the functions include: increased heart beat, dialated pupils and decreased digestion.
What is the parasympathetic NS?
The parasympathetic NS is activated when we are relaxing. Som of the functions include: increased digestion (motility of GIT), decreased heart beat, contricted pupils.
Describe the sympathetic signal transduction pathway.
Signal travels through cholinergic neurons from the lateral horn to the sympathetic chain (ganglion), where it innervates an adrenergic neuron signaling via nAChR. The postganglionic adrenergic neuron then innervates the effector organ, and stimulate either alpha- or beta adrenergic R. The signal is ascending from the thoracic - or the lumbar parrt of the spinal cord.
Are there any exceptions of the sympathetic signal transduction pathway?
Yes; 1) the cholinergic neuron can innervate chromaffin cells in the adrenal medulla without passing through a ganglion. Chromaffin cells secrete adrenalin. 2) innervartion of sweat glands are through two cholinergic neurons, and is not innervated by an adrenergic neuron.
Describe the parasympathetic signal transduction pathway.
Signal travels through cholinergic neurons from the cervical or the sacral part of the spinal cord to a ganglion near the effector organ, where it innervates another cholinergic neuron signaling via nAChR. The postganglionic cholinergic neuron then innervates the effector organ, and stimulate via mAChR. Long preganglionic neuron, and ganglion very close to effector organ (!)
What is the diffeerence between afferent- and efferent signaling? And which pathway through the spinal cord do they each use?
Affrent is a signal TOWARDS the CNS (adferre). It goes through the ventral root ganglion.
Efferent is a signal AWAY from the CNS (exferre). It goes through the dorsal root ganglion.
Describe the signal cascade when the parasympaticus is stimulating the heart.
Acetylcholine binds to the M2 R (mAChR). The Gi-beta-gamma subunit gates a GIRK channel inducing K^+ efflux resulting in hyperpolarization, The Gi-alpha inhibits a T-type Ca^2+ channel, also resulting in hyperpolarization. All this leads to a decreased heart rate.
Describe the signal cascade when the sympaticus is stimulating the heart.
Noradrenalin binds to a beta-adrenergic R on the pacemaker cells of the heart. The Gs-alpha subunit activates an AC, which converts ATP into cAMP. cAMP gates a funnt channel, causing Na^+ influx inducing depolarization, which gates voltage gated Ca^2+ channels, resulting in AP. This leads to increased heart rate.
