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Anatomy Exam 2

Nervous system subdivisions


CNS includes

brain and spinal cord

PNS includes

Cranial Nerves and ganglia
• Spinal nerves and ganglia

Spinal Nerve roots

Dorsal and Ventral

Dorsal root of spinal nerve

contains visceral and somatic AFFERENT fibers


contains cell bodies of somatic and visceral afferent nerve fibers

Ventral root of spinal nerve

contains somatic and visceral efferent fibers

Lateral Horn

contains cell bodies visceral efferent fibers

Ventral Horn

contains somatic efferent fibers

Spinal nerve contains

both sensory and motor nerve fibers

functional components of spinal nerve

General Somatic Afferent
General Visceral Afferent
General Somatic Efferent
General Visceral Efferent

General Somatic Afferent

carries sensations from body wall to spinal cord: pain, touch, temp proprioception and pressure

General Visceral Afferent

carries sensations from viscera to spinal cord: mucous membranes glands blood vessels and smooth muscles and cardiac muscles

General Somatic Efferent

motor information from spinal cord to skeletal muscles

General Visceral Efferent

motor information from spinal cord to cardiac muscle, smooth muscles of viscera and glands

ANS branches

includes Sympathetic and Parasympathetic branches - together maintain homeostasis

ANS innervation

vesceral organs, BVs and secretory glands

ANS controlling centers

HT and Brain stem

Differences between PS ANS and S ANS

anatomical, neurotransmitters, physiological effects

Sympathetic Nervous system

acts in sympathy with emotions; fight or flight; more extensive of the ANS branches, ratio of afferent to efferent is 1 to 17;

effects of sympathetic nervous system

increased HR, dilated pupils, constricted arterioles in skin and intestine, dilated muscular arterioles, high BP, pale face, dry mouth, hair stands up, blood rushes to brain heart and skel muscle preferentially, closed alimentary and urinary tract sphincters, bronchi and bronchioles dilated

Sympathetic chain

where pre and post ganglionic neurons interface

Intermediolateral cell column

Lateral Horn from T1-L2, contains cell bodies of preganglionic afferent sympathetic neurons

Preganglionic sympathetic neurons pathway

myelinated neurons with cell bodies in Lateral horn, that leave the spinal cord in ventral root, join the afferent sensory fibers in spinal cord after DRG, pass via white rami communicantes to paravertebral ganglia of sympathetic trunk.

From sympathetic trunk ganglia, efferent sympathetic fibers:

synapse with excitor neuron/postganglionic sympathetic neuron in the ganglion

postganglionic sympathetic neurons

non-myelinated neurons that leave the ganglion and pass to spinal nerves as gray rami communicantes to spinal nerve and distributed to smooth muscles in wall of blood vessles, sweat glands arrector pili,

white and grey rami communicantes

the connections between preganglionic visceral efferent fibers and post ganglionic visceral efferent fibers to and from the spinal cord, white is pre- grey is post-ganglionic.

Splanchnic nerves

formed by efferent preganglionic sympathetic neurons that do not synapse on postganglionic neurons until closer to the effector organ

Greater splanchnic nerve

T5 to T9. pierces the crus of diaphragm and synapses at ganglia of celiac plexus, renal plexus and suprarenal medulla

Lesser Splanchnic nerve

T10 to T11. descends with greater splanchnic nerve synapses on post-ganglionic fibers in lower part of celiac ganglia

Least Splanchnic Nerve

T12. pierces diaphragm and synpases at ganglia of renal plexus

Cervical Ganglion

where T1 to T4 preganglionic sympathetic efferent fibers synapse with post-galglionic sympathetic fibers

cervical postganglionic sympathetic grey fibers

innervate smooth msucels and glands of head neck and upper extremities and heart

Parasympathetic Nervous system outflow

cranial nerves and sacral nerves 2-3-4

Parasympaathetic effect

reverses the change from sympathetic innervation. rest and digest; slower HR, pupils constricted, secretion of saliva and intestinal juices, sphincters relaxes, bladder contracts, glycogen synthesis allowed

Parasympathetic preganglionic cell bodies

located in brain stem and grey matter of sacral segments of spinal cord S2,3,4

Brainstem cells located in the

occulomotor nerve, facial nerve, glossopharyngeal nerve, Vagus nerve

ratio of pre to post ganglionic PARASYMPATHETIC fibers

1 to 3

ratio of pre to post ganglionic SYMPATHETIC fibers

1 to 17

Cardiac plexus

located below the arch of the aorta, formed by sympathetic and parasympathetic nerves

sympathetic innervation of the heart

from upper 5-6 segments of thoracic spinal cord lateral horn

preganglionic neurons innervating the heart end

in the cervical and third and fourth thoracic sympatehtic ganglia

cervical and third and fourth thoracic sympathetic ganglia

where upper 5-6 thoracic spinal segments' sympathetic pregangionic nerves synapse on postganglionic fibers. from here, postganglionic fibers go bilaterally to the heart

Parasympathetic innervation of the heart

vagus nerve

sympathetic innervation of the heart terminates on

SA node, AV node, cardiac muscle cells, coronary arteries

Effects of sympathetic stimulation of the heart

cardiac acceleration, increased force of contraction, dilation of coronary arteries,

adrenergic stimulation of SA node results in

rate of depolarization of pm cells, increase in atrioventricular conduction

Parasympathetic nerves of the heart terminate on

SA node, AV node, Coronary arteries

PS activation effects on heart

HR slows, force of contraction less, constriction of coronary arteries. net saves energy

mechanism of PS post synaptic innervation

acetylcholine binds muscarinic receptors to slow rate of depolarzation of PM cells and atrioventricular conduction and decreases contractility

Cardiac Plexuses

superficial and deep

Superficial Cardiac Plexus

inferior to aortic arh between aortic arch and pulmonary trunk

deep cardiac plexus

between aortic arch and trachial bifurcation

spinal thoracic segments innervating heart

T1 to T5 or T6

SA node function

initiates contraction of the heart

SA node location

subendothelial layer of heart at juntion of SVC and right atrium near superior end of crista terminalis

SA node Heart rate

70 beats per minute

SA node signal sent to

myocardial tissue of both atria

SA node positive and negative innervation by

sympathetic and parasympathetic nervous system

AV node location

internal, inferior aspect of interatrial septum near opening of coronary sinus

AV node receives signal from

SA node

AV node transmits signal

from SA node to AV bundle of His. down through fibrous skeleton of heart along membranous part of interventricular septum

Purkinje fibers

where AV bundle branches split and extend to walls of ventricles

right bundle branch of AV bundle of His stimulates:

muscles of interventricular septum, Anterior papillary muscle, wall of right ventricle

moderator band

carries electrical signal from right bundle of his (interventricular septum muscles) to anterior papillary muscle

Left bundle of His stimulate:

interventricular septum muscles, anterior and posterior papillary msucles and wall of left ventricle

referred pain

pain perceived at different location than its source

zone of referred pain

where somatic sensory neurons that share spinal ganglion with visceral sensory neurons terminate on skin

Cardiac referred pain

pain in upper left limb because of nerves of brachioplexus that shares the spinal cord segments

ganglion shared with cardiac sensory nerves

T1 through T4 or T5

angina pectoris

radiates from substernal and left pectoral regions to left shoulder and medial aspect of left upper limb

part of limb that is stimulated in angina from which nerves?

medial cutaneous nerve of the arm, medial cutaneous nerve of the forearm, ulnar nerves

coronary arteries

T1 through T3 shared by upper limb cutanous nerves

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