Lecture 17- the autonomic nervous system Flashcards
what is the purpose of the autonomic nervous sytem?
innervates organs whose functions are not usually under voluntary control
where does the sensory info get processed?
hypothalamus, limbic system, spinal cord, medulla
reflexes are important for autonomic control, what can they evoke changes in?
autonomic output (negative feedback or feedforward)
what is the autonomic system?
actions involving involuntary control
what are examples of conscious control?
pee
heart rate can be controlled through meditation
what do visceral effectors do?
they adjust their activity to match the bodys needs to maintain homeostasis
they don’t need the ANS in order to function
what is the general autonomic nerve pathway?
CNS –> preganglionic fiber –> autonomic ganglion –> postganglionic fiber –> effector organ
what is a ganglion?
a mass or group of neuronal cell bodies. knot of cell bodies
in post ganglions do we have synapses?
we have networks of synapses (SOOO MANY)
what does the autonomic nervous system divide into?
sympathetic nervous system
parasympathetic nervous system
in the sympathetic nervous system where do the cell bodies and axons of preganglioinics originate?
thoracic (T1) and lumbar (L2) regions of the spine
what can be said about sympathetic nervous system preganglionic and postganglionic fibers?
preganglionic fibers are short
postganglionic fibers are long
what makes the sympathetic nervous system diverse?
there are many routes and many places for a preganglion to synapse
what are the 3 routes of axons after they exit spinal cord?
- make a synapse in a sympathetic chain ganglion
- pass through SCG and synapse in the adrenal medulla
- pass through SCG and synapse in a collateral ganglion
what neurotransmitters do most preganglionic fibres and postganglionic fibers release in the sympathetic nervous system?
preganglionic fibres release ACh
postganglionic fibres release norepinephrine
what kinds of receptors does the postsynaptic ganglion and the target cell have? SNS
nicotinic receptors (for ACh)
adrenergic receptors (for norepinephrine)
why might the postganglionic neuron release ACh? SNS, its uncommon
releases ACh in sweat glands
what structure is a modified sympathetic ganglion?
adrenal medulla
where do parasympathetic nervous system fibres originate from?
cranial and sacral areas of CNS
what is the structure of preganglionic fibres and postganglionic fibres in parasympathetic nervous system?
preganglionic fibers are longer
postganglionic fibers are very short
what neurotransmitters do most preganglionic fibres and postganglionic fibers release in the parasympathetic nervous system?
preganglionic fibers release ACh
postganglionic fibers release ACh
what is the difference between the sympathetic nervous system and parasympathetic nervous system?
SNS branches many times sto synapse on many different postganglionic neurons more divergence
PNS branches to synapse on postganglionic neurons, thus has more control over target organs because theres less divergence
how many cranial nerves are in PNS? how many have parasympathetic function
12 total
4 have PNS function
what are the 4 cranial nerves with parasympathetic function?
oculomotor nerve: control the lens and pupil of the eye
facial nerve: tear glands, salivary glands, nasal glands
glossopharyngeal nerve: salivary glands
vagus nerve: innervates the viscera (organs)
why is the vagus nerve considered to be wondering? many of these sensory afferents project topographically to what tract in the brainstem? what number cranial nerve is it?
innervates all organs except adrenal medulla and some parts of the colon
nucleus of the solitary tract in brainstem
10th cranial nerve
where is the sensory info processed in vagus nerve? what information does it carry?
processed within the nucleus of the solitary tract
carries efferent (PNS) information to regulate organ function
what has a longer lasting effect?
SNS
because ACh quickly breaks down and norepinephrine breakdown is slower (it circulates around for awhile)
what does the SNS activate?
adrenal medulla to release large amounts of epinephrine
how do we predict the effect of SNS and PNS?
SNS is fight or flight
PNS is rest and digest
if youre really stressed out, in what state will the SNS and PNS be in?
SNS will be heightened but PNS will never turn off, the volume of it will just decrease
effect of sympathetic nervous system and parasympathetic nervous system on the heart?
SNS: increased rate, increased contraction
PNS: decreased rate, decreased force of contraction
effect of sympathetic nervous system and parasympathetic nervous system on eyes?
SNS: dilation of pupil and not at all significant for refocusing lens
PNS: constriction of pupil and adjustment of eye for near vision
effect of sympathetic nervous system and parasympathetic nervous system on exocrine pancreas?
SNS: inhibition of pancreatic exocrine secretion
PNS: stimulation of pancreatic exocrine secretion
effect of sympathetic nervous system and parasympathetic nervous system on salivary glands?
SNS: stimulation of small volume of thick saliva rich in mucus
PNS: stimulation of large volume of watery saliva rich in enzyme
compare and contrast the effects of SNS and PNS on the heart, eyes, and salivary glands
antagonistic (working against eachother) heart, eyes
complimentary (did teh same thing) salivary glands: both increased saliva, different types of saliva but still both produced itw
what is a good example of a complimentary response in PNS and SNS?
male sexual response:
PNS responsible for erection
SNS responsible for ejaculation
what parts of the body only receive sympathetic intervention?
adrenal medulla
sweat glands
smooth muscle of most blood vessels
what 4 CNS centres contribute to autonomic regulation?
limbic system
hypothalamus
brain stem
spinal cord
