PS120: Autonomic Nervous System Flashcards
Define Autonomic Nervous System
the part of the nervous system that controls the involuntary acts in our body
What are involuntary acts of our body?
activity of the…
- smooth ms
- cardiac ms
- gland secretion
What are the origins of the ANS?
from limited area of CNS:
- cranial nerves 3, 7, 9, 10
- all thoracic segments
- L1, L2, L3 segments
- S2, S3, S4 segments
What are the 2 systems the ANS is divided into?
- Sympathetic NS
- Parasympathetic NS
What are the properties of SNS?
- the components of this system get activated all in one time
- (i.e) they act in sympathy with each other, hence the name sympathetic NS
- prepares body for increased activity, thus it is activated in stressful situations (emergency conditions)
- catabolic (energy consuming)
Which ANS system is energy-consuming?
The SNS; it is catabolic and activates muscular exercise, fear, flight, and fight.
What are the properties of the PNS?
- the components of this system are not activated all in one time
- (i.e.) each component acts separately.
- prepares body for recovery & repair, so it active during rest
- anabolic (energy preserving)
Why are the PNS’s parts not activated at the same time?
Generalized parasympathetic NS stimulation may be fatal.
What are the 2 types of relationship between the ANS divisions?
- Anatomical relation
- Functional relation
What are the types of anatomical relation between PNS and SNS?
- double innervation
- single innervation
What is double innervation and where is it found?
- both symp and parasymp innervation for a given organ
- majority of organs have double innervation
What is single innervation & where is it found?
there are organs that only have symp. innervation. these include:
- skin
- limbs: (blood vessels of skeletal ms.)
- abdominal & thoracic walls: (blood vessels & skin of skeletal ms.)
- ventricles of the heart
- spleen
- adrenal medulla
The adrenal medulla’s innervation is:
single (symp only)
Types of functional relations between PNS & ANS include:
- antagonism
- synergism
- similarity
- dominance
- reciprocal
Reciprocal is the same as ____ because…
Antagonism, as they both have a relationship where when one system is stimulated, the other system is inhibited.
Antagonist action in the heart:
Sympathetic: tachycardia
Parasympathetic: bradycardia
Antagonist action in the bronchi:
symp: bronchodilation
parasymp: bronchoconstriction
Antagonist action in GIT:
symp: decrease in motility
parasymp: increase in motility
define synergism
complementary action, when the two systems help each other
example of synergism:
sexual intercourse
- parasymp: causes erection of erectile tissue (clitoris & penis) and the secretion of seminal vesicle fluid & prostate gland
- symp: cause ejaculation & orgasm
define similarity
exceptionally the two systems may have similar action on the same organ
example of similarity:
symp and parasymp stimulation of salivary secretion.
- symp: leads to viscid (trophic) salivary secretion that is: (little amount, poor in water, rich in enzymes)
- parasymp: leads to watery (true) salivary secretion that is: (large in amount, rich in water, poor in enzymes)
define dominance
when one system is dominant to some organs to give them tone DURING REST
- milds continuous activity during rest
example of sympathetic dominance
vasoconstrictor tone keeping the diametre of blood vessels approximately 1/2 the max diametre; keeps ABP constant
example of parasympthetic dominance
vagal tone: parasympathetic tone to the heart to decrease high inherited rhythm of SAN
define autonomic ganglia
ganglion is a collection of nerve cells (soma of neurons) outside the CNS
Types of autonomic ganglia
- Paravertebral (lateral)
- Prevertebral (collateral)
- Terminal
What are lateral ganglia?
ganglia that lie on both sides of vertebral column, forming a sympathetic ganglion chain.
What are the characteristics of the sympathetic chain?
- each has 26 ganglia (3 cervical, 12 thoracic, 5 lumber, 5 sacral, 1 coccygeal)
- it is considered lateral ganglia
What are collateral ganglia?
ganglia that is found midway between spinal cord and viscera
Where are collateral ganglia found?
They lie at the origin of big arteries from abdominal aorta & are named after them.
What is an example of prevertebral/ collateral ganglia?
celiac superior & inferior mesenteric
What system are prevetbral ganglia run by?
both symp & parasymp.
What are terminal ganglia?
ganglia that lie within the organ of supply
What system innervates the teminal ganglia?
only parasympathetic
How many ganglia are laterl/ paravertebral?
26
What is the function of autonomic ganglia?
act as distributing centres
How do autonomic ganglia perform their function?
They relay one preganglionic fibre with many postganglionic fibres which compenstates for the limited origin of ANS in relation to its wide distribution.
What is the origin of symp & parasymp?
symp origins:
- thoracolumbar outflow
- all thoracic segments
- upper 3 lumbar segments
parasymp origins:
- craniosacral outflow
- 3, 7, 9, 10 cranial nerves
- middle 3 sacral segments
symp vs parasymp
types of ganglia
symp: lateral & collateral
parasymp: terminal & collateral
symp vs parasymp
Distribution
symp: wider distribution
parasymp: relatively localized
- no parasymp to skin, limbs, abdominal/ thoracic walls, ventricles, spleen, & adrenal medulla
Symp vs parasymp
Prepare the body for…
symp: increased activity
parasymp: recovery & repair
symp vs parasymp
active during…
symp: stress (emergency conditions) as fear, flight, or fight
parasymp: mainly rest & relaxtion
symp. vs parasymp.
relation to energy:
symp: catabolic (energy consuming)
parasymp: anabolic (energy preserving)
symp vs parasymp
Form of activity
symp: usually generalized (mass discharge, all parts are activated together)
parasymp: often localized (i.e. parts are activated separately)
symp vs parasymp
chemical transmission
symp:
- preganglionic fibres are cholinergic: secrete acetylcholine (the chemical transmitter at autonomic ganglion)
- postganglionic fibres are adrenergic: secrete noradrenaline in ALL SITES EXCEPT a) sweat glands b) blood vessels of skeletal ms… they secrete acetylcholine A.C. (cholinergic)
parasymp: ALL OF PARASYMP IS CHOLINERGIC
- preganglionic fibres are cholinergic: secrete A.C.
- postganglionic fibres are cholinergic: secretes A.C. in ALL SITES
symp vs parasymp
receptors
symp:
- end of pregangionlic receptors: cholinergic & nicotinic because it is stimulated by small doses of nicotine
- postganglionic receptors (the end at organ of supply):
a) adrenergic receptors: [alpha 1 is stimulatory everywhere & alpha 2 is inhibitory found in intestine] & [beta: b1 stimulatory in heart & beta 2 inhibtory everywhere]
b) cholinergic muscarinic: the cholinergic receptors present in sweat glands & skeletal ms blood vessels
parasymp:
- end of preganglionic: cholinergic nicotinic because it is stimulated by small dose of nicotine (same as symp. pregang.)
- end of postganglionic: cholinergic muscarinic because it is stimulated by muscarine
Sympathetic NS
Spinal segment & nerve of SNS for head & neck:
upper 2 thoracic segments
Function of SNS in head & neck:
- eye: exophthalmos (anterior protusion of eye), elevation of upper eyelid, pupilo-dilation (mydriasis), & decrease power of the lens through relaxtion of ciliary muscle
- skin: vasoconstriction, contraction of piloerector ms, secretory to sweat glands
- salivary glands: stimulate secretion of viscid saliva (small amount but rich in enzymes), vasoconstriction
Spinal segment & nerve of SNS in thorax:
upper 4 thoracic
Function of SNS in thorax:
Heart:
1. stimulatory (increase heart rate & force of contraction)
2. coronary vasodilation
Lungs:
1. bronchodilation
2. pulmonary vasocontriction
Spinal segment & nerve of SNS in abdomen:
- lower 6 thoracic
- greater splanchnic nerve
Function of SNS in abdomen:
- GIT: inhibits [wall of stomach, small intestine, proximal of large intestine, motor to sphincter, & also gall bladder]
- Blood vessels: vasoconstriction but also WEAK vasodilation
- Liver: glycogenolysis
- Spleen: contraction of splenic capsule, releasing stored blood
- Adrenal medulla: secretes 80% adrenaline, 20% noradrenaline
Spinal segment & nerve of SNS in pelvis:
- upper 3 lumbar
- lesser splanchnic nerve
Function of SNS in pelvis:
- Retention of urine
- Retention of feces
- Shrinkage of erectile tissue due to vasoconstriction of pelvic blood vessels
- Ejaculation: contraction of smooth ms. in (seminal vesicle, prostate, & vas deferens)
- Uterus: affects vary
What innervation (and ganglia of relay) is responible for inhibition of wall of distal part of large intesine?
The upper lumber, lesser splanchnic nerve, with the celiac inferior mesenteric ganglia relaying
What ganglia of relay are present in the abdomen?
celiac superior & inferior mesenteric
What spinal segments & nerves of SNS are found in upper limb?
5 to 9 thoracic
What spinal segments & nerves of SNS are found in lower limb?
10 to 12 thoracic
Ganglia of relay for upper limb SNS:
C2 to C3 & first two thoracic ganglia
Ganglia of relay for lower limb SNS:
lumber & sacral ganglia
Function of SNS in limbs:
- Skeletal ms. blood vessels: vasodilation for better contration and delayed fatigue with RAPID RECOVERY
- Skin: same as in head & neck
What is the effect called when fatigue is delayed & recovery is rapid?
Orbeli’s phenomenon
Which ganglia of relay are associated with the SNS of the head & neck?
the superior cervical ganglion
Which ganglia is associated with the SNS of the thorax?
all 3 cervical and the upper 4 thoracic ganglia
