Autonomic Nervous system/ PUPIL DIALATION ETC

Question 1

what are two major divisions of the nervous system ?

Answer 1

central and peripheral

nervous systems

Question 2

what is the function of PNS?

Answer 2

The PNS is responsible for delivering information to the CNS, much of which arises from a variety of sensory receptors, via its
sensory/afferent division

Question 3

what is the function of CNS?

Answer 3

The CNS, which consists of the brain and spinal cord, is
responsible for both ‘processing’ this incoming information and for initiating the appropriate responses, which are communicated to the rest of the body via the
motor/efferent division of the PNS.

Question 4

what can the motor branch of the PNS be subdivided into ?

Answer 4

somatic ( voluntary )nervous system, which innervates skeletal muscle, and the autonomic nervous system (ANS) which
supplies both smooth and cardiac muscle as well as most glands.

Question 5

what can the ANS be further subdivided into ?

Answer 5

The ANS is further
subdivided into sympathetic (thoraco-lumbar )and parasympathetic (cranio-sacral ) branches, which have opposing actions
on smooth & cardiac muscle, glands & other peripheral effectors.

Question 6

what do sea squirts do ?

Answer 6

they anchor them selves to a rock , where they will spend the rest of their lives , they digest their own brains but keep ANS components for energy use and recovery

Question 7

what is the main function of the ANS ?

Answer 7

The ANS is primarily concerned with the homeostasis of our internal environment

Question 8

what is the main function of the sympathetic branch of the ANS ?

Answer 8

gets the body ready for ‘action’ (e.g. escape from a
predator) by increasing cardiac output and respiration, releasing glucose into the blood, and getting more blood to the skeletal muscles, while shutting down unnecessary
activities such as the digestion of food and urine production.

Question 9

what is the main function of the parasympathetic branch of the ANS ?

Answer 9

Once the potentially
threatening behaviour is over (i.e. you are hiding in your cave), the parasympathetic
system slows down the cardiac and respiratory systems and replenishes the body’s depleted energy reserves.

Question 10

what innervation do most blood vessels receive ?

Answer 10

receive only sympathetic innervation which causes constriction.
Dilation is simply achieved by the absence of sympathetic stimulation.

Question 11

what are the major differences between the somatic vs 2 divisions of the autonomic motor efferent systems ?

Answer 11

. location of CNS motor neurons
. mono vs di-synaptic pathways to effector
. axon lengths vs myelination
. conduction velocity and significance 
. neurotransmitters and receptors

Question 12

what does the lateral horn in the spinal cord grey matter contain ?

Answer 12

autonomic motor neurons

Question 13

what does the ventral horn in the spinal cord grey matter contain ?

Answer 13

somatic motor neurons

Question 14

what is difference in the axons of somatic and autonomic ?

Answer 14

the axons of the somatic nervous system are large and myelinated and directly innervate skeletal muscle, the autonomic pathway is almost always a two neuron
chain.

Question 15

where is the cell body of somatic and autonomic neurons located ?

Answer 15

The cell bodies of both somatic and autonomic neurones are located within the CNS.

Question 16

what do somatic motor fibres do ?

Answer 16

somatic motor fibres directly innervate skeletal muscle with one synapse ( mono-synaptic )

Question 17

explain how the ANS is di-synaptic ?

Answer 17

autonomic motor neurons in both sympathetic and parasympathetic branches have axons that come out and make connections with neurons in PNS which are known as autonomic ( sympathetic ) ganglion cells which are innervated by preganglionic fibres and those synapses activate the autonomic ganglion cells which innervate postganglionic fibres which have axons of their own which travel to particular smooth muscle , cardiac muscle , gland cells .

Question 18

why is the somatic motor system faster than the ANS ?

Answer 18

The preganglionic axon leaving the CNS (somatic) is, compared to somatic axons is relatively thin, although it is still myelinated. The postganglionic fibre, however, is even
smaller and unmyelinated.
Due to the presence of a synapse, the small diameter of its
axons and the lack of myelin in postganglionic fibres, conduction is much slower in the ANS than in the somatic system.
somatic nervous are large and myelinated so faster conduction

Question 19

what is difference in ganglion cells of autonomic sympathetic and parasympathetic ganglion cells ?

Answer 19

parasympathetic ganglion cell has longer axon and is closer to target cells than sympathetic ganglion cell

Question 20

what is the difference in neurotransmitter released by sympathetic and parasympathetic ganglion ?

Answer 20

motor neurons of both sympathetic and parasympathetic nervous system use ACH as their neurotransmitter and that neurotransmitter is released by the parasympathetic nervous system into ganglion cells and those ganglia also use ACH as their neurotransmitter however ganglion cell of sympathetic nervous system receive input form motor neurons in the CNS and release noradrenaline into target

Question 21

what are the 4 cranial nerves with parasympathetic components ?

Answer 21

. 3rd oculomotor - from edinger - westphal nucleus innervates neurons in the ciliary ganglion supplying the sphincter pupillary muscle of the iris and ciliary muscle
. 7 th facial - innervates neurons in pterygopalatine ganglion supplying lacrimal gland and in the geniculate ganglion 2 of the salivary glands

. 9th glossopharyngeal - innervates neurons in the otic ganglion supplying the largest salivary gland

. 10 th vagus - innervates numerous ganglia supplying the heart , liver and respiratory , digestive , urinary and reproductive system

Question 22

where do preganglionic fibres of sympathetic system arise from ?

Answer 22

The preganglionic fibres of the sympathetic nervous system arise from cell bodies located
in spinal cord segments T1-12 and L1-2. It is therefore often also referred to as the
thoracolumbar system.

Question 23

where do the preganglionic axons of the sympathetic nervous system leave the spinal cord ?

Answer 23

The preganglionic axons leave the spinal cord via the ventral horns and proceed to 2
chains of paravertebral ganglia, lying very close to either side of the spinal cord. The preganglionic axons connecting the spinal cord to these ganglia, due to their myelin sheath, are referred to as the white rami communicans.

Question 24

where does the chain of

sympathetic (paravertebral) ganglia extend ?

Answer 24

extends all the way along the cord, consisting of; 3

cervical, 11 thoracic, 4 lumbar, and 4 sacral ganglia.

Question 25

what happens once a preganglionic axon reaches a paravertebral ganglion ?

Answer 25

1. It synapses in the ganglion directly opposite to where it emerged from the spinal
   cord.
2. It enters the ganglion opposite where it emerges from the spinal cord but does not synapse there.
3. It passes through the ganglia without synapsing. It synapses far from the spinal
   cord, near is target organ, in prevertebral/collateral ganglia.

Question 26

where do The postganglionic fibres in sympathetic division leaving the paravertebral ganglia go ?

Answer 26

in some cases go directly to

their target structures (e.g. heart & lungs), most, however, travel around the body within the spinal nerves.

Question 27

what is the function of Some postganglionic fibres originating from ‘higher’ ganglia, such as the superior
cervical ganglion ?

Answer 27

contribute to cranial, as well as spinal, nerves. Such fibres within the
cranial nerves include those that innervate the dilator muscle of the pupil.

Question 28

what is different about The sympathetic fibres innervating the adrenal medulla ?

Answer 28

are also part of the splanchnic
nerves, however, unlike any other autonomic fibre, they innervate their target organ
directly without forming a synapse within a ganglion.

Question 29

what is the function of splanchnic nerve ?

Answer 29

splanchnic nerve has longer pre-ganglionic axons to solar plexus ganglion supplying digestive and urinary systems

Question 30

where are the cell bodies of the parasympathetic system located ?

Answer 30

are located in,
and leave the spinal cord at, a sacral level of the spinal cord, while others are located in
the brainstem & exit via 1 of 4 cranial nerves: oculomotor (III), facial (VII), glossopharyngeal (IX) or vagus (X). The parasympathetic system is therefore also known as the craniosacral system.

Question 31

where are the ganglia of the parasympathetic system known as and located ?

Answer 31

known as terminal ganglia, lie far from the spinal cord and are located close to,, the target organ. fibres of the parasympathetic system are usually long

Question 32

how can release of the same neurotransmitter cause excitation of some effectors e.g.heart muscle and inhibition of others e.g. gastric glands ?

Answer 32

2 types of receptors

Question 33

what are the two types of receptor that sit in membrane of different effector cells?

Answer 33

some cells have beta receptor( stimulatory ) - e.g. in heart muscle
other cells have alpha 2 ( inhibitory ) -

. NE ( noradrenaline ) binds to excitatory beta receptor , receptor is a G - protein receptor that activates proteins on the other side inside cell , this activates adenyl cyclase potassium ions inside the cell stop leaving causing cell depolarisation as inside the cell is positive

NE binds to alpha 2 receptor ( inhibitory ) - when adenyl cyclase is activated potassium channels open and causes cell hyperpolarization

Question 34

what are the two classes of ACH receptors ?

Answer 34

nicotinic receptor -

muscarinic receptor -

Question 35

what is the antagonist in nicotinic receptor ?

Answer 35

nicotine which binds to nicotinic receptors which cause potassium channel to open , these nicotinic receptors are mostly present in skeletal muscle

Question 36

what are types of muscarinic receptors ?

Answer 36

M1,M5 excitatory - when ACH binds to these receptors is excited ( depolarisation ) and closes k channels ( found in parasympathetic nervous system )
M2, M4 inhibitory ( hyperpolarization ) open k channel - when ACH binds to them cell is inhibited

Question 37

what is a nicotinic receptor antagonist ?

Answer 37

curare

Question 38

what is a muscarinic receptor antagonist ?

Answer 38

atropine

Question 39

what are the 2 opposing iris muscles ?

Answer 39

. pupil dilator - when they contract the length gets shorter so pupil dilates
radical sympathetic from superior cervical ganglion
. pupil constrictor /whasphincter which is a circular muscle when they contract they get shorter
parasympathetic from ciliary ganglion 3rd cranial nerve

Question 40

how is pupil dilation achieved ?

Answer 40

not by directly stimulating the
sympathetic system innervating the dilatator, but by blockage of the parasympathetic system serving the sphincter. Since the sphincter is cholinergically innervated, its receptors are easily blocked by an anti-
muscarinic such as atropine.

Question 41

how is pupil constriction achieved ?

Answer 41

Pupil constriction is most easily achieved by drugs such as eserine/physostigmine which prevent the destruction of Ach by acetylcholinesterase.

Question 42

how is pupil dilation achieved in optometric practice ?

Answer 42

tropicamide in adults and cyclopentate in children as this also paralyses their ciliary muscle/accommodation too .

Question 43

what does it mean if patient has one pupil that is pathologically dilated ? and how do you treat it ?

Answer 43

constrictor muscle is damaged
or nerve supply to constrictor muscle isn’t working so pupil is dilated .

. stimulate neurotransmitter action in the muscle with ACH blocker ( eserine ) which prevents its degradation so increasing its availability
. if pupil constricts the muscle is working and the problem is with the nerve input the pathology is neurogenic
. if it doesn’t constrict the problem is with the muscle itself : the pathology is myogenic

Question 44

what are the examples of opposite neurogenic pathologies ?

Answer 44

. dilated pupil ( mydriasis )
.parasympathetic ganglion or nerve damage
. paralyses iris constrictor
. e.g. adie’s tonic pupil

. constricted pupil ( miosis )
. sympathetic ganglion or nerve damage
. paralyses iris dilator
. e.g. horner’s syndrome

Question 45

what is the function muller’s / superior tarsal muscle ?

Answer 45

helps elevate the upper eyelid

Question 46

what does the innervation of the iris sphincter muscle do ?

Answer 46

activates smooth muscle fibres that are circularly arranged around the pupillary margin