Lecture 14 - Autonomic Nervous System Flashcards
What does the autonomic nervous system do ?
Controls all involuntary functions - heart rate, blood pressure, GI motility
other system is the somatic nervous system - different system
what do we divide the ANS into ?
the parasympathetic nervous system - rest and digest - regulation of basal activities
the sympathetic nervous system - fight or flight - response to stress situations - will increase the heart rate, BP and force of contraction - release of adrenaline
outline the structure of the sympathetic nervous system
It begins in the thoracic or lumbar domains of the CNS (spine)
Have axons that travel SHORT distance to the paraveretabral sympathetic chain - bilateral to CNS
chemical neurotransmitter to another LONGER neuron that goes to body to signal control
outline the structure of the parasympathetic nervous system
one set begins in the medullary region of CNS
first set of neurons are LONG followed by a SHORT secondary neuron to target tissue
for now the only region without nerves projecting is the cranial system
neurons from sacral region are different and may be para or sympathetic in nature
what is the ganglion
a bundle of nerve fibers where the synapse between where the two neurons are - the point of chemical communication
Outline the parasympathetic nervous system
Parasympathetic - LONG mylenated (fast) pre-ganglionic neuron - close to the CNS.
followed by a SHORT unmylenated (slow) post ganglionic nerve to target tissue (PNS)
from the medulla and sacral (contentious) regions
ganglia are located within the innervated tissue
rest and digest
cranial region does not contribute nerve firers to either system but is the final section of the CNS
Outline the sympathetic nervous system
Sympathetic - SHORT mylenated (fast) pre-ganglionic neuron - close to the CNS.
followed by a LONG unmylenated (slow) post ganglionic nerve to target tissue (PNS)
Ganglia are located in the paravertebral chain close to the spinal cord
originate in the lumbar and thoracic regions
cranial region does not contribute nerve firers to either system but is the final section of the CNS
Fight or Flight
what are the two principal neurotransmitters in the ANS
Acetylcholine - Ach
Noradrenaline - NA
where do the two primary Neurotrasmitters function in the ANS
ALL pre-ganglionic neurons are cholinergic (use Ach)
release Ach from the pre ganglioninc nerve into the synapse
Nicotinic Ach Receptors (NAchR) detect the Ach
these are ligand gated ion channels
this will activate the post ganglionic nerves
Parasympathetic Post Ganglionic nerves are also cholinergic (use Ach) - they release Ach which acts on Muscarinic Ach receptors (mAch) in the target effector tissue
what neurotransmitter does the post ganglionic parasympathetic neurons release ? what does this act on ?
Parasympathetic Post Ganglionic nerves are cholinergic (use Ach)
they release Ach which acts on Muscarinic Ach receptors (mAch) in the target effector tissue
mAch receptors are GPCR’s
five subtypes - M1, M2, M3, M4, M5
these are expressed differently in different tissues and have different antagonists
each one can have a different impact
some may produce relaxation or stimulation depending on the tissue and defectors
what neurotransmitter does the post ganglionic sympathetic neurons release ? what does this act on ?
what is the execption
MOST sympathetic post-ganglionic neurons are noradrenergic - use noradrenaline as the principal neurotransmitter
NA interacts with 2 major classes of adrenorecptors - also GPCR’s
alpha which divides into a1 and a2
beta which divides into b1, b2, b3
b1 (one heart) - b2 (2 lungs)
some specialized sympathetic neurons are cholinergic - piloerection of hair, sweat glands
why do we use GPCR’s for the ANS
they are very specific
each signal acts on unique receptors - fine tune the response
provide integrated cell response - amplification and cascade
What is a NANC
what is their purpose ?
a NON-Adrenergic, NON-Cholinergic transmitter - NANC
They can be co released with NA or Ach
examples are ATP, Serotonin, Nitric oxide NO
what is the possible/argued third division of the ANS
enteric nervous system
the control of the GI tract
the ANS has a hormonal affect as well what is this ?
Sympathetic postganglionic neurones that act on on the adrenal medulla (gland) is the homronal affect
the neurons differentiate in the adrenal medulla to form chromaffin cells - upon sympathetic stimulation they release adrenaline into the blood stream via exocytosis
chromaffin cells are innervated by preganglonic sympathetic neurons and they themselves can be considered as postganglionc sympathetic neurons
