Physiology > Autonomic Nervous System > Flashcards
Autonomic Nervous System Flashcards
Anatomical division of ANS
Cranial autonomic
3, 7, 9, 10
Thoraco-lumbar: Lateral horn cells of all thoracic and upper 4 lumbar
Sacral: Lateral horn cells of sacral 2, 3, 4
Spinal cord segments that don’t give autonomic fibres
Not all cranial nerves Cervical segments Lumbar 5 Sacral 1 and 5 Coccygeal
Functional division of ANS
- Thoraco-lumbar: Symapthetic system
- Cranio-sacral: Parasympathetic system
No parasympathetic fibres supply:
Limbs
Thoracic and abdominal parities
Skin
Cranial nerve 1
Olfactory nerve
Cranial nerve 2
Optic nerve
Cranial nerve 3
Occulomotor nerve
Cranial nerve 4
Trochlear nerve
Cranial nerve 5
Trigeminal nerve
Cranial nerve 6
Abducens nerve
Cranial nerve 7
Facial nerve
Cranial nerve 8
Vestibulochoclear nerve
Cranial nerve 9
Glossopharyngeal nerve
Cranial nerve 10
Vagus nerve
Cranial nerve 11
Accessory nerve
Cranial nerve 12
Hypoglossal
Greater splanchnic nerve pre-ganglionic fibres relay in:
Celiac, mesentric and renal ganglia
Lesser splanchnic nerve pre-ganglionic fibres relay in:
Hypogastric ganglion
Sympathetic to head and neck
Origin, relay, functions
Origin: Lateral horn cells of upper 2 thoracic segments
Relay: Superior cervical sympathetic ganglion
Functions: 3 eye, 3 skin and 1 salivary
- Mydriasis: Dilation of pupil (motor to dilator pupillae muscle)
- Retraction of lids (motor to superior and inferior tarsal muscles)
- Exophthalmus: (motor to muller’s muscle so eye protrudes forward)
- Vasoconstrictor to blood vessels of head and neck via alpha-receptors
- Hair erection (motor to errctor bili muscle)
- Secretory to sweat glands (via cholinergic sympathetic fibres)
- Secretory to salivary glands (trophic secretion)
Horner’s syndrome
Causes and manifestations
Cause:
Lesion of the sympathetic pathway to the head and the manifestations occur
ipsilateral to the lesion.
lesion in the cervical paravertebral ganglia.
Manifestations:
a) Miosis: (persistent constriction of the pupil) due to:
i) Paralysis of the dilator pupillae muscle.
ii) The unopposed parasympathetic action on the pupil.
b) Ptosis: (dropping of the upper eyelid).
This is due to paralysis of the superior tarsal muscle.
c) Enophthalmos:
This is due to paralysis of the Muller’s muscles.
d) Anhydrosis: (dryness of one half of the face)
So, no sweating on the same side of lesion in the neck and face.
e) Vasodilatation on the skin vessels on the same side.
Sympathetic to thoracic viscera
Origin, relay, functions
Origin: Lateral horn cells of upper 5 thoracic segments
Relay: 3 cervical ganglia and upper 5 thoracic lateral ganglia
Functions: 2 heart and 2 lungs
-Increase all cardiac properties (Contractility, rythmicity, excitability and conductivity)
-Vasodilitation to coronary blood vessels (indirect)
- Bronchodilitation
- Vasoconstriction to pulmonary arteries
Sympathetic to abdominal viscera
Origin, relay, functions
Origin: Lateral horn cells of lower 6 thoracic segments and upper 2 lumbar segments. The pre-ganglionic fibres form the greater splanchnic nerve
Relay: In the superior mesentric, renal and celiac ganglia (collateral)
Function:
-Decrease evaculation of GIT (Relaxation of smooth muscles and contraction of sphincters)
-Glycogenolysis to increase blood glucose levels
-Contraction of splenic capsuls to add more blood
-Suprarenal glands to cause release of adrenaline and noradrenaline
Sympathetic to pelvic viscera
Origin, relay, functions
Origin: Lateral horn cells of upper 4 lumbar segments. Pre-ganglionic fibres form the lesser splanchnic nerve
Relay: Hypogastric ganglion
Function:
- Vasoconstrictor to the blood vessels of the pelvic viscera including those of the
external genitalia thus, it causes shrinkage of the penis and clitoris.
-Urine retention: Because, it is:
Inhibitory to the wall of the urinary bladder. Motor to the internal urethral sphincter.
- Retention of feces: Because, it is:
Inhibitory to the wall of the rectum. Motor to the internal anal sphincter.
- Ejaculation of semen: Because, it is:
Motor to the smooth muscles of the vas deferens, seminal vesicles,
ejaculatory ducts and prostate.
- It produces variable effects on the uterus (motor and inhibitory
effects depending on the stage of menstrual cycle (with estrogen it causes contraction with progesterone - inhibitory)
Sympathetic to upper limbs
Origin, relay,
Origin: From lateral horn cells of 4th to 8th thoracic segments
Relay: Middle and inferior cervical ganglia and upper 2 thoracic ganglia
Sympathetic to lower limbs
Origin, relay
Origin: Lateral horn cells of 10th thoracic to 2nd lumbar
Relay: In lumbar, sacral and coccygeal ganglia
Sympathetic to thoracic and abdominal parities
Origin, relay,
Origin: Lateral horn cells of all thoracic and lumbar segments
Relay: In its corresponding ganglia
Function of sympathetic to upper limbs, lower limbs, abdominal and thoracic parities
3 skin and muscle
- Vasoconstrictor to cutaneous blood vessels
- Vasodilator to skeletal blood vessels
- Secretory to the seat glands (eccrine sweat glands are cholinergic innervation while apocrine sweat glands are adrenergic innervation)
- Motor to erector Bili muscle
- Orbelli phenomenon
Sweat glands types and sites
Sympathetic to eccine sweat glands is cholinergic
Adrenergic sympathetic fibres supply:
- Palms od hand and soles of feet
- Apocrine sweat glands (like axilla)
Orbelli phenomenon:
During muscular exercise, sympathetic stimulation accelerate the chemical reactions in the active muscles. Leads to vasodilatation of blood vessels in the skeletal muscles lead to:
- Stronger muscle contraction
- Delayed fatigue
- Early recovery after exercise
Alarm response includes:
- Increase in mental activity
- Dilated pupils and retraction of upper eye lid
- Increase in heart properties, increase in blood pressure, increase blood supply to active muscles and organs and decrease blood supply to less active areas
- Dilatation of bronchi and bronchioles and increase rate and depth of respiration
- decrease activity of GIT
- Increase rate of blood coagulation due to increased fibrinogen
- Orbelli phenomenon
- increase cellular metabolism, circulatory catecholamines, blood sugar and sweat secretion
(parasympathetic)
Visceral structures in the head are supplied by
Oculomotor, facial and glossopharyngeal nerves
(parasympathetic)
Thoracic and abdominal viscera are supplied by:
Vagus nerve
About ….% of all parasympathetic nerve fibres are present in the vagus nerve
75
Sacral parasympathetic
Arises from lateral horn cells of 2nd, 3rd and 4th sacral segments to form the pelvic nerve
Oculomotor
Origin, relay and functions
Origin: Arise from Edinger Westphal nucleus in the midbrain
Relay: Ciliary ganglion. Post-ganglionic fibres are short ciliary nerves
Functions:
- Pupillary constriction: Motor to the constrictor pupillae muscles
- Accommodation for near vision (relaxation of suspensory ligaments so increases the convexity of the lens)
Facial nerve branches
Chorda tympani nerve
Greater superficial petrosal nerve
Chorda tympani
Origin, relay and functions, supply
Origin: From the superior salivary nucleus at the junction of pons and the medulla
Relay: In the submandibular ganglia.
Supply: The postganglionic fibres innervate the submandibular and sublingual salivary glands
Functions:
- Increase profuse watery salivary secretion
- Vasodilator to salivary blood vessels
- Vasodilator to the blood vessels of the anterior 2/3 of the tongue
Greater superficial petrosal nerve
Origin, relay and functions, supply
Origin: Arise from the lacrimal nucleus in pons
Relay: In the sphenopalatine (pterigo) ganglion
Supplies: Post ganglionic fibres innervate the lacrimal glands and the small buccal and nasal glands
Functions:
- Increases the lacrimal secretions
- Vasodilitation of lacrimal blood vessels
- Vasodilitation of the blood vessels in the mucous membrane covering palate and nasopharynx
Glossopharyngeal nerve
Origin, relay and functions, supply
Origin: Inferior salivary nucleus and emerges as lesser superficial petrosal nerve
Supply: Posterior 1/3 of tongue and the parotid gland
Relay: Otic ganglion
Function:
- Profuse watery secretion of the parotid gland
- Vasodilatation of blood vessels of the parotid gland
- Vasodilatation of the blood vessels of the posterior 1/3 of the tongue
Vagus nerve
Origin, relay, functions
Origin: Dorsal vagal nucleus (dorsal motor nucleus of the vagus) in the medulla
Relay: Relays in the terminal ganglia of the organs it supplies (eg cardiac ganglia)
Functions: 3 heart, 3 lungs, GIT
- Inhibitory to all cardiac properties (doesn’t innervate the ventricles)
- Decreases cardiac metabolism and oxygen consumption
- Constriction of coronary blood vessels due to decreased accumilation of metabolites
- Broncoconstriction
- Secretory to the mucus glands in bronchi and bronchioles (viscid mucus)
- Motor to plain muscles of GIT and inhibitory to their sphincters
- Evacuation of gall bladder as it is motor to it and inhibitory to its sphincters
- Secretory to gastric, pancreatic and intestinal glands
Pelvic nerve
Origin, relay and functions
Origin: Arise from the lateral horn cells of 2nd, 3rd and 4th sacral segments
Relay: In the hypogastric ganglion and terminal ganglion of the pelvic plexus
Functions:
- Urination (Contract urinary bladder and relax sphincter)
- Defecation (Contraction of rectal muscles and relaxation of sphincters)
- Erection of penis and clitoris by vasodilatation
- Secretion of seminal fluid from prostate gland and seminal vesicles
