ANS Flashcards
somatic nervous system
subject to voluntary control
innervates skeletal muscle with the exception of: diaphragm and some pharyngeal and upper esophageal muscles like swallowing
autonomic nervous system
involuntary branch of peripheral nervous system
innervates the heart, smooth muscle, most glands, and adipose tissue
special case of autonomic nervous system
trained spy can hide autonomous responses better than average joe
ANS and varicosities
ANS has many varicosities affecting the whole organ
ANS divisions
has two: sympathetic and parasympathetic that maintain the balance of organ systmes for different functional states
antagonistic control of ANS
sympathetic and parasympathetic have tonic activities meaning most internal organs are under antagonistic control of both divisions with one being excitatory and one being inhibitory
what happens when the body gets ready for exercise or threats
blood flow shunted to skeletal muscles and heart
bronchiles dialate
liver releases glucose
GI tract and urogenital systems inhibited
sympathetic nervous system roles
mobilizes body resources for activity- fight or flight system
4E’s
exercise
excitation
emergency
embarasement
role or parasympathetic system
promotes maintenance activities and conserves body energy
illustration of parasympathetic
person after a meal relaxing
blood pressure, heart rate, respiratory rate are low
Gastrointestinal tract activity is high
pupils are constricted
autonomic pathway neuron pathway
two neurons that synapse in an autonomic ganglion
CNS- preganglionic neuron- autonomic ganglion- postganglionic neuron- target tissue
autonomic control centres in the brain
sub cortical bc not conscious
hypothalamus
midbrain
pons
medulla
spinal chord
hypothalamus
water balance, temp, hunger
midbrain
pupillary reflex
pons
respiration
urinary bladder
medulla
respiration
cardiac
vomiting
swallowing
spinal chord
visceral reflex
what neurotransmitter relays impulses to postganglionic neurons
acetylcholine
what neurotransmitter do sympathetic nerves use at the target organ
norepinephrine
what neurotransmitter do parasympathetic nerves use at the target organ
acetylcholine
origins of sympathetic system
sympathetic pathways originate in the thoracic and lumbar regions of the spinal chord which provides sympathetic innervation of the entire body
T1-L2
where are sympathetic ganglia found
primarily in two chains that run along either side of the bony vertebral column with additional ganglia along the descending aorta at the origin of major abdominal arteries
ex. celiac and mesentric ganglia
sympathetic pre and postganglia
short preganglionic axons and long postganglionic axons. the ganglia are farther away from their target organs
routes of pre ganglionic fibres
have several routes to reach their targets
preganglionic fibres routes
enter the paravertebral sympathetic trunk (chain of ganglia)
-synapse in the trunk and postsynaptic fibers join somatic nerves to the body (vessels and sweat glands)
-through the trunk to cervical ganglia where they synapse to give rise to postganglionic fibers that innervate the head and thoracic viscera
-through the trunk to form splanchnic nerves which reach and synapse in the collateral ganglia to innervate abdominal viscera
-through the trunk to reach the adrenal glands
-synapse in the trunk and continue as sacral spanchnic nerve to pelvic organs
collateral ganglia
celiac, mesenteric
where are preganglionic sympathetic neurons
in spinal chord segments T1-L2
what enters the ganglionic chain
presynaptic fibres- white ramus
what joins the corresponding spinal nerves to targets
postganglionic fibres- grey ramus
what serves as the postsynaptic symathetic neurons
adrenal medulla
-neurons do not have axons but instead release transmitters into the blood to circulate the body
-20% norepinephrine and 80% epinepherine
what are the components of the parasympathetic system
cranial and sacral
what cranial nerves innervate the salivary glands and eye muscles
III, VII, IX
what is the vagus nerve and what does it do
CN X
descends and wanders through the thoracic and abdominal cavities inneravting all viscera there
what is the sacral chord and what does it do
S2-4 gives rise to parasympathetic fibres that innervate the pelvic organs
do the cranial nerves join the somatic nerves
no and as a result peripheral arterioles and sweat galnds are innerated by sympathetic nerves only
what percentage of parasympathetic fibres does the vagus nerve contain
75%
parasympathetic innervation to all visceral organs except for the pelvic organs
what provides parasympathetic innervation to the pelvic organs
the sacral cord s2-4
where are parasympathetic ganglia located
either in or near their target organs
long preganglionic axons and short postganglionic axons
how does sympathetic nerves dialate arterioles in skeletal muscle byt constict vessels in gut? parasympathetic slow down heart but speed up gut?
the diversity of cholinoceptors and adrenoceptors on target organs forms the basis of different response patterns
how do receptor subtypes work to produce diversified responses
they are structurally related to bind and respond to same transmitter but they are coupled with different cellular proteins and induce different signalling cascades for dramatically different effects
adrenergic receptors and their subtypes
bind to norepinephrine and epinephrine
alpha receptors- subtypes a1 and a2
beta receptors- subtypes B1,B2,B3
where is a1 present and what does it do
in arterioles and excitatory
where is b1 and what does it do
in heart and excitatory
where is b2 and what does it do
in bronchiles and skeletal muscles and inhibitor
muscarinic receptors
all effector cells stimulated by postganglionic cholinergic fibres (parasympathetic fibres to target organs)
acetylcholine at these receptors can be inhibitory or excititory dependig on subsypes M1,M2,M3
M1 + M3 receptor and what it does
excitatory and present in exocrine glands and GI smooth muscles
M2 and what it does
inhibiotry and present in heart and bladder
what adrenogenic receptors are used in sympathetic response
a1- arterioles- excitatory
b2- skeleal and bronchioles dialate-inhibitory- more blood flow and oxygen
bladder in parasympathetic response
is inhibited by M2 in muscranic receptors which are due to aceetylcholine
receptor subtypes responding differently to same neurotrasmitter
coupled to diffrerent cellular proteins and induce different signalling cascades for different effects
