Lec 4 Intro to ANS Flashcards
What is function of ANS?
mainly involuntary, regulates activities of visceral organs through effects on smooth muscle, cardiac muscle, glands
What is function of somatic nervous system?
innervates skeletal muscle, under conscious [voluntary] control
Which part of CNS is one neuron vs two neuron?
somatic = one neuron autonomic = two neurons
What are 3 branches of ANS
- enteric
- sympathetic
- parasympathetic
What is enteric division of ANS?
- complex network of neurons in wall of gut
- independent of CNS
- extensive intrinsic activity, including peristalsis
What is function of sympatheticc/parasympathetic [compared to enteric]?
- regulates activity of visceral organs and glands [exocrine and endocrine]
- depends on CNS
- viscera and glands innervated by both brands
Where are preganglionic cell bodies located in sympathetic?
thoracic and lumbar levels of spinal cord
Where are preganglionic cell bodies in parasympathetic?
medulla, sacral level of spinal cord
Which nerves carry preganglionic axons in sympathetic?
thoracic and lumbar spinal nerves
“thoracolumbar”
Which nerves carry preganglionic axons in parasympathetic?
cranial and sacral spinal nerves
“craniosacral”
Where are the ganglia located in sympathetic?
Near spinal cord – paravertebral and prevertebral ganglia [except also in adrenal gland]
Where are the ganglia located in sympathetic?
near or in wall of innervated organ
Where do sympathetic cell bodies lie?
in intermedio-lateral cell column of spine
Does one sympathetic preganglionic axon synapse on a single or multiple postganglionic cells
multiple
What type of innervation goes to adrenal gland?
- only sympathetic
- secretory cells homologous to sympathetic ganglion
What type of innervation goes to heart? Each chamber?
- atria innervated by both [sympathetic + para]
- ventricles just sympathetic
What type of innervation goes to vasculature?
- sympathetic
What type of innervation goes to liver?
- sympathetic
What type of innervation goes to skeletal muscle?
- sympathetic
What type of innervation goes to sweat glands
sympathetic
what kind of innervation goes to pancreas [B cells]?
sympathetic
What does sympathetic do to heart rate?
Accelerates
What does parasympathetic due to heart rate?
Decelerates
What does sympathetic due to heart contractile force?
increases
What does parasympathetic due to heart contractile force?
decreases [atria]
What does sympathetic due to blood vessels in skin/viscera?
contracts
What does sympathetic due to blood vessels in skeletal muscle?
dilates
What does sympathetic do to urinary bladder wall?
relaxes
What does parasympathetic do to urinary bladder wall?
contracts
What does sympathetic do to urinary sphincter?
contracts
What does parasympathetic due to blood vessels in skeletal muscle?
Nothing! parasympathetic doesnt affect blood vessels! Silly goose!
What does parasympathetic do to urinary sphincter?
relaxes
What does parasympathetic do to sweat glands?
nothing!
what does sympathetic do to thermoregulatory sweat glands?
increases
what does sympathetic do to apocrine [stress] sweat glands?
increases
what does sympathetic do to liver metabolic activity?
- increases glycogenolysis
- increases gluoneogenesis
what does sympathetic do to fat metabolic activity?
- increases lypolysis
What does sympathetic due to eye pupil?
dilates
What does sympathetic do to eye lens?
flattens - far vision
What does parasympathetic do to eye pupil?
constricts
what does parasympathetic do to eye lens?
rounds - nears vision
Two examples where dual innervation with complementary [instead of opposite] effects?
- salivary glands: both branches stimulate saliva secretion but different components
- male sexual response: erection under parasympathetic, ejaculation under sympathetic
What innervations responsible for which parts of male sexual response?
- erection under parasympathetic
- ejaculation under sympathetic
A few examples of autonomic sensory information that informs central autonomic activity
- arterial BP
- blood glucose, Co2, O2
- distension of bladder
How do sensory neurons affect autonomic activity and maintain homeostasis? Where?
- sensory neurons in viscera project to nucleus of solitary tract in medulla
- visceral info integrated along with information from higher brain region via hypothalamus
- medulla also contains nucleus whose cells projects to sympathetic + parasympathetic
- processed sensory info directs output to ANS
- mains homeostasis
What is the baoreceptor reflex?
- decrease in BP is sensed by baroreceptor in blood vessel
- sensory neuron relays info to medulla
- sympathetic activity increased and parasympathetic decreased in medullary centers
- - leads to vasoconstriction, higher CO - get homeostatic increase in BP
What is dominant resting tone
- usually is the autonomic branch that makes the organ [or tissue] contract or move
what is dominant resting tone of GI tract?
- parasympathetic because parasympathetic increases GI motility
Exception to dominant resting tone?
- heart’s dominant tone is parasympathetic which slows heart rate
- denervated [transplanted] heart has bpm 90-110
What are two main neurotransmitters released at ANS synapses?
Acetylcholine
Norepinephrine
What is acetylcholine? What do you call receptors that release it?
- hormone – neurons release acetylcholine [ACh]
- receptors that respond to ACh called cholinergic
What is norepinephrine? What do you call receptors that release it?
- hormone – neurons release NE
- receptors that respond to NE called adrenergic or noraderenergic
Where is Epinephrine released from?
- Released as hormone from adrenal medulla
- acts at ANS receptors
Which ANS releases ACh [3 types]? Is each nicotinic or muscarinic? Specific organ examples?
- all preganglionic neurons [both sympathetic and parasympathetic]
- —- nicotinic [a type of nAChR]
- all parasympathetic postganglionic neurons
- —- muscarinic [a type of nAChr]
- ——– cardiac and smooth muscles, glands, nerve terminals
- a few sympathetic postganglionic neurons
- —- muscarinic [a type of GPCR]
- ——– sweat glands
Which ANS releases NE [2 types]?
- most of sympathetic postganglionic neurons
- the rest release dopamine or acetylcholine
What are two specific cholinergic receptors?
N: nicotinic receptors [a type of nAChR]
M: muscarinic receptors [a type of GPCR]
Where are nicotinic receptors found?
- preganglionic sympathetic and parasympathetic
- somatic [skeletal muscle]
where are muscarinic receptors found?
- postganglionic parasympathetic: cardiac and smooth muscle, gland cells, nerve terminals
- postganglionic sympathetic: sweat glands
what are the two types of adrenergic receptors?
alpha: a type of GPCR [Gi/o or Gq/11]
beta: a type of GPCR [Gs]
Where are adrenergic receptors found in sympathetic system?
- cardiac and smooth muscle, gland cells, nerve terminals
Where are dopaminergic receptors found in sympathetic system?
- renal vascular smooth muscle
What is D1?
- a type of dopaminergic receptor
- a type of GPCR [Gs]
What two hormones does adrenal medulla secrete? What percentage each?
- 80% epinephrine
- 20% norepinephrine
What are 6 mechanisms that drug affects synaptic transmission
- alter transmitter synthesis
- alter transmitter release
- block receptors
- activate receptors
- potentiate effect of transmitter on receptor
- interfere with transmitter degradation or uptake
What are 2 main ways transmitter removed followign release
- enzymatic degradation
- re-uptake by releasing neuron
How does a direct agonist/antagonist work?
- acts at receptor
- mimics or blocks effect of endogenous transmitter
How does an indirect agonist work?
interferes with degradation or re-uptake of transmitter
How does an indirect agonist/antagonist work?
interferes with synthesis or release of transmitter
What is receptor sensitization?
- during prolonged under-stimulation due to receptor blockade or reduced transmitter level
- responsiveness increases
- denervation supersensitivity
What is receptor desensitization?
- excessive stimulation causes reduction in responsiveness
Over what time frame does receptor sensitization/desensitization occur?
seconds to hours
By what mech [3 ways] does sensitization/desensitization occur?
mediated by:
- conformational change in receptor
- increased/decreased receptors in membrane
- altered efficiency of receptor coupling to secondary messenger pathway
