ANS

Question 1

which parts of the brain conrol ANS ?

Answer 1

hypothalamus, spinal cord and brain stem.

Question 2

does lower brain take part in stimulating the ANS ?

Answer 2

yes it does ,especially the lower cortex in which the limbic system can transmit signals to the ANS.

Question 3

do any other reflexes stimulate the ANS ?

Answer 3

yes . ANS also is also stimulated by / operates through visceral reflexes for ex reflexes from our gut or enteric system.

Question 4

what are the 2 subdivisions through which the efferent autonimic signals are transmitted to the body organs?

Answer 4

sympathetic and parasympathetic nervous system.

Question 5

where do the sympathetic nerve fibers originate from?

Answer 5

they originate from T1 till L2 segments of spinal cord.

Question 6

where do each of the sympathetic nerve fibers terminate?

Answer 6

T1 - head
T2 - neck
T3 , T4 , T5 , T6 - thorax
T7, T8, T9, T10 , T11 - abdomen
T12, L1, L2 - legs

Question 7

where do the cell body of each preganglionic neuron originates from?

Answer 7

intermediolateral horn of the spinal cord.

Question 8

identify the special nature of sympatheic nerve endings in adrenal medulla.

Answer 8

the preganglionic sym nerve fibers enter the adrenal medulla without synapsing at all.
( pathway : intermediolateral cells -> splanchnic nerves -> adrenal medulla-> modified neuronal cells -> release nor/epinephrine ).

Question 9

where do the parasympathetic nerve fibers originate from?

Answer 9

they originate from caniosacral nerves :
cranial nerve 3, 7, 9, 10
sacral / pelvic nerve 2, 3, 4

Question 10

where do the craniosacral nerves terminate ?

Answer 10

cranial nerve 3 -> pupillary sphinter + ciliary muscles of eye
cranial nerve 7 -> lacrimal, nasal, submandibular glands
cranial nerve 9 -> parotid glands
cranial nerve10 -> Vagus nerve ; passes into the entire thoracic and abdominal regions.
sacral nerve 2 and 3 -> distribute to descending colon, rectum, urinary bladder, lower portions of ureters.

Question 11

which parasympathetic nerve fiber is the most important?

Answer 11

its the cranial nerve 10 which is the vagus nerve. about 75 % of parasympathetic nerves are supplied by vagus nerve.it distributes to the heart, lungs, esophagus, stomach, small itestine, half of the colon, liver, gallbladder, pancreas, kidneys, and upper portions of ureters.

Question 12

where are the post ganglionic neurons of parasym nervous system located?

Answer 12

at the walls of the organs.

Question 13

the preganglionic neurons synapse with which cells in the adrenal medulla ?

Answer 13

chromaffin cells; which then secrete epinephrine and norepinephrine.

Question 14

describe the condition pheochromocytoma.

Answer 14

its the tumor of adrenal medulla which happens due to excessive catecholamines and increased excretion of VMA.

Question 15

what are the effector organs of sympatheic and parasympathetic nervous system?

Answer 15

smooth , cardiac muscles and glands.

Question 16

the preganglionic neurons of both; the parasympathetic or sympathetic n.s are :

Answer 16

cholinergic

Question 17

whats the difference btw the post ganglionic neurons of the sym and parasym n.s?

Answer 17

1. the postganglionic neurons of parasym.n.s are cholinergic.
   while those of sympatheic.n.s are adrenergic ( with the exception of sweat glands and few blood vessels ).
2. the postganglionic neurons of parasym.n.s are shorter than those of the sym.n.s.

Question 18

how is acetylcholine synthesized?

Answer 18

its synthesized at the cholinergic nerve endings or varicosities where it is stored in its vessicles in its concentrated form until released upon stimulation.
synthesis:
acetyl CoA + choline/acetyl choline acetyltransferase —> acetylcholine.

Question 19

whats the fate of acetylcholine?

Answer 19

after performing its function of nerve signal transmittion to the post ganglionic neuron, acetylcholine is degraded into its constituent ions namely acetate ion and choline, by the enzyme acetylcholinesterase. the choline ion is transported back to the terminal preganglionic neuronic bulb where its used for the formation of acetylcholne again and again.

Question 20

how is norepinephrine formed?

Answer 20

its synthesis is initiated in the terminal adrenergic nerve fibers and continued in the vesicles of the same nerve fibers :
1. tyrosine –> DOPA ( by hydroxylation)
2. DOPA –> dopamine ( by decarboxylation)
3. dopamine is tranported into the vesicles.
4 dopamine –> norepinephrine (by hydroxylation)
in case of adrenal medulla theres one more step
5. 80% norepinephrine –> epinephrine ( by methylation ).

Question 21

what are the 2 main recepters that are activated by acetylcholine?

Answer 21

muscarinic and nicotinic.
muscurine is a poison obtained from toadstool.
both are activated by acetylcholne but each of these activate their own respective receptors.

Question 22

difference between nicotinic and muscarinic receptors:

Answer 22

1. nicotinic receptors are ligand gated whie muscarinic are activated by G proteins.
2. nicotinic are classified into Nn,Nm,Ng. while muscarinic are classified into M1,M2,M3,M5.
3. muscarinic receptors are present on effector cells stimulated by postganglonic cholinergic nerve fibers of either parasympathetic or sympathetic nerve fibers.
   4.nicotinic receptors are present at the synapses between preganglionic and postganglionic neurons of both the sympathetic and parasympathetic systems.

Question 23

what is the fate of norepinephrine?

Answer 23

after transmission of nerve impulse , norepinephrine removed from the synapse by either of the following 3 ways :
1. 80 to 50 % = by reuptake into the terminal nerve fibers through active transport.
2. most of the remaing: by diffusing into the blood fluids and blood stream.
3. very small amount: destruction by monoamineoxidase and catechol-O-methyl.

Question 24

what are the 2 major adrenergic receptors ?

Answer 24

alpha : 1 and 2
beta : 1, 2, 3

Question 25

which protein do alpha and beta receptors use for signalling?

Answer 25

G- protein

Question 26

what are the alpha receptors associated with?

Answer 26

blood vessels

Question 27

what is the effect of nor/epinephrine on alpha and beta receptors?

Answer 27

norepinephrine: stimulates alpha receptors to a greater extent than beta receptors.
epinephrine: stimulates both the receptors almost equally.

Question 28

Which functions of eyes are controlled by ANS?

Answer 28

1. The pupillary opening.
2. The focus of lens.

Question 29

How does the ans affects the constriction and dilation of the pupil?

Answer 29

1. Sympathetic stimulation–> constriction of meridional fibers of iris–>constriction –>pupil dilates.
2. Parasympathetic stimulation–> constriction of circular muscles–> constriction of pupil.

Question 30

how does light reflex stimulate parasym.n.s?

Answer 30

when excessive light reaches our eyes, the light reflex stimulates the parasymthetic .n.s which in return constricts our pupil in order to allow limited quantity of light to reach the retina.

Question 31

which type of ans controls most of our body glands?

Answer 31

parasympathetic.n.s ; nasal, lacrimal, salivary and many other gland secretions are controlled by it.

Question 32

which type of nervous sys. primarily controls the secretions of small and large intestines?

Answer 32

unlike many other glands being controlled by our paras.n.s , the secretions of small and large intestines are mainly controlled by the local factors/nerves of the enteric nervous system.

Question 33

what affects secretions of sweat glands ?

Answer 33

stimulation of sweat glands by sym nerves induces sweat secretion. while they remain unaffected by parasym.n.s.

Question 34

the sympathetic fibers to most sweat glands are cholinergc?
true/ false.

Answer 34

true.

Question 35

what are apocrine glands and how are they stimulated?

Answer 35

apocrine glands are sweat glands present in the axillary regions of our body that release thick, odoriferous secretion upon stimulation by sym.n.s.

Question 36

what do the secretions of apocrine gland help in?

Answer 36

they act as lubricants and help in the sliding motion on the inner side of the shoulder joint.

Question 37

what are the intrinsic set of nerves of the gi tract known as?

Answer 37

intramural plexus / the intestinal enteric n.s.
its located in the walls of gut.

Question 38

how do the paras n.s and the sympathetic n.s affect the intramural plexus?

Answer 38

they only affect the intramural plexus by increasing or decreasing their specific actions:
1. paras stimulations promote the motily of the gi tract by inducing peristalsis and opening and closing spinchters; thus allowing the propulsion of their contents.
2. strong sym stimulations reduce peristalsis and tone the sphincters.

Question 39

which type of ans mainly affects the systemic blood vessels?

Answer 39

the sym.stimulations primarily affect the blood vessels by constricting them.they specifically affect the blood vessels of the skin of limbs and the abdominal viscera.

Question 40

what are the effects of alpha and beta receptors on the blood vessels?

Answer 40

alpha= constriction.
beta= dilation.

Question 41

what are the 2 factors that affect the arterial pressure and what are the effects of sym and para.n.s on arterial pressure?

Answer 41

the factors are:
1. propulsion of blood from heart.
2. the resistence of blood flow in the peripheral n.s.
>sym stimulation increases both which increases the arterial pressure acutely.long term pressure isnt affected until the sym stimulation also simultaneously induces rtainment of water and salts in the kidney.
> moderate parasy stimulations via the vagus nerves cause reduced pumping of heart but it doesnt really affect the resistance in the periheral nerves which results in slight decrese in the arterial pressure.
> strong parasym stimulations almost stop the heart and occasionally may completely stop it for a few seconds which results in the complete loss of arterial pressure temporarily.