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202T2 > ANS > Flashcards

ANS Flashcards

1
Q

Describe the map of the ANS

A

Sympathetic is sandwiched between the parasympathetic

Brainstem and S2-S4 region of spinal cord are parasympathetic and T1-L2 region is parasympathetic

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2
Q

Briefly describe the ANS as part of the nervous system, include its action in involuntary control and its divisions

A

Part of peripheral NS

Involuntarily control:

  • Regulates operation of the internal organs
  • Maintains internal environment
  • Innervates smooth muscle, cardiac muscle and glands

Divisions: sympathetic, parasympathetic and enteric

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3
Q

What are disynaptic pathways?

A

They describe the way in which ANS neurons synapse as their axons do not pass directly to effector organs.

Cranial nerve nuclei/grey matter of spinal cord along with its myelinated preganglionic axon synapse at symp/parasymp ganglion. Postganglionic axon (unmyelinated) synapse with effector organ (smooth muscle, cardiac muscle, glands0

EXCEPTION: Sympathetic innervation of the adrenal medulla (they pass through ganglion into splanchnic nerves to synapse in prevertebral ganglia)

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4
Q

What is the function of the sympathetic and parasympathetic NS?

A

SYMPATHETIC FUNCTION
Fight, flight, fright
Maximises use of metabolic resources

PARASYMPATHETIC FUNCTION
Opposite to sympathetic division (Rest and digest)
Switched on during resting
Increases/conserves metabolic resources

WORK TOGETHER TO CONTROL THE INTERNAL ENVIRONMENT

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5
Q

Consider the neurotransmission. Describe it within autonomic ganglia

A

ACh is main neurotransmitter
Binds to nicotinic receptors on postganglionic neuron
- Ionotropic ligand-gated (fast): ACh opens pore, depolarises neuron

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6
Q

Consider the neurotransmission. Describe it within postganglionic sympathetic neurons

A

Noradrenaline is main neurotransmitter (sweat glands use ACh)
Binds to adrenergic receptors of effector organ
- Metabotropic G-protein coupled (slow)

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7
Q

State, with examples, the subtypes of the adrenergic receptors on effector organs

Give drugs which effect such receptors

A

a1- blood vessel smooth muscle
Prazosin is an antagonist used to treat hypertension

b1- on heart
Atenolol is an antagonist used to treat hypertension

b2- on bronchial smooth muscle
Salbutamol is an agonist used to treat asthma

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8
Q

The sympathetic system is a huge system. State where it has its effects

A 
Cardiac muscle 
Bronchi of lungs
Sweat glands
Hair follicles
Blood vessels
Abdomino-pelvic viscera
Eye
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9
Q

Consider the neurotransmission. Describe it within the adrenal medulla

A

ACh is main neurotransmitter
Binds to nicotinic receptors on chromaffin cells
Causes release of adrenline/noradrenaline into circulation
- DIRECT activation of sympathetic effector organs

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10
Q

Describe the sympathetic trunk/chain

A

Interconnected paravertebral ganglia
Extends from cervical to sacral levels

Preganglionic fibres enter sympathetic trunk through white rami communicans (from T1-L2)

ANATOMY:
Lateral horn- cell bodies of preganglionic neurons
White ramus communicans- myelinated preganglionic axons
Grey ramus communicans- unmyelinates postganglionic axons
symp trunk

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11
Q

Consider the neurotransmission. Describe it within postganglionic parasympathetic neurons

Give an exampled of an antagonistic drug

A

ACh is main neurotransmitter
Binds to muscarinic receptors to the effector organs
- Metabotropic G-protein coupled (slow)

Atropine- cholinergic-muscarinic anatagonist (lowers parasympathetic activity) used to treat bradycardia, dilate pupils, reduce glandular secretions

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12
Q

Describe the cervical sympathetic trunk

A

3 ganglia in cervical sympathetic trunk

-Superior/middle/inferior (Stellate ganglion= fused inferior cervical and T1 ganglia, exists in 80%)

Postganglionic fibres exit via grey rami communicans to spinal nerves (sympathetic supply to upper limbs)

“Piggy back” DOWN common carotid artery to heart (sympathetic supply to heart)

“Piggy back” UP internal/external carotid artery to head

  • Internal carotid plexus: to eye (dilation, eye lid move) and to lacrimal gland (inhibits secretion)
  • External carotid plexus: to submandibular and parotid glands (inhibits secretions)
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13
Q

What is the ratio of postganglionic fibres to preganglionic?

What type of responses are sympathetic ?

A

Postganglionic fibres much more numerous than preganglionic
1:10 ratio

Sympathetic responses are mass responses
Allows coordinated activity at multiple levels

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14
Q

What is the distribution os postganglionic fibres from sympathetic trunk and from prevertebral ganglia?

A

FROM SYMP TRUNK:

  1. To the periphery (sweat glands, hair follicles, blood vessels) via grey rami communicans back into spinal nerves
  2. To the viscera (heart, lungs, head) via medial branches/plexus

FROM PREVERTEBRAL GANGLIA
Postganglionic fibres form plexus around viscera

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15
Q

What is Horner’s syndrome?

A

Disruption of the sympathetic supply to the head

Any party of pathway- hypothalamus to preganglionic neurons e.g. lesions with brainstem/ cervical spinal cord (in MS)

Pupil

Eyelid

Skin of face

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16
Q

Describe the fibres involved in the thoracic sympathetic chain

A

Preganglionic fibres exit via thoracic splanchnic nerves, by piercing diaphragm, to abdomen (Greater>Lesser>Least>to prevertebral ganglia)

Celiac ganglion- stomach/duodenum
Superior mesenteric ganglion- SI
Aorticorenal ganglion- kidney
Ganglia close to abdominal aorta

12 thoracic sympathetic trunk ganglia

Postganglionic fibres exit via grey rami communicans to spinal nerves and medial branches to heart and lungs
Postganglionic fibres form prevertebral plexus around viscera

17
Q

Describe the lumbar sympathetic fibres

A

4 lumbar sympathetic trunk ganglia

Postganglionic fibres exit via grey rami communicans to spinal nerves

Preganglionic fibres exit via lumbar splanchnic nerves to pelvis

Synapse in prevertebral ganglia. Inferior mesenteric ganglia- large intestine

18
Q

Describe the sacral sympathetic fibres

A

4 Sacral sympathetic trunk ganglia

Postganglionic fibres exit via:

  • Grey rami communicans to spinal nerves (lower limb)
  • Sacral splanchnic nerves to pelvic organs
19
Q

The parasympathetic system is a small(er) system. State where it has its effects

A 
Cardiac muscle 
Bronchi of lungs
Sweat glands
Hair follicles
Blood vessels
Abdomino-pelvic viscera
Eye
Salivary and lacrimal glands
20
Q

Consider the cranial parasympathetic system. Describe the nerves involved.

A

Preganglionic neuronal cell bodies in cranial nerve nuclei

MIDBRAIN
CN3- Oculomotor nerve (Edinger-Westphal nucleus)

PONS
CN7- Facial nerve (Superior salivatory nucleus)

MEDULLA
CN9- Glossopharyngeal nerve (Inf. salivatory nucleus)
CN10- Vagus nerve (Nucleus ambiguous, dorsal motor nucleus), passes to heart, lungs and abdominal viscera

21
Q

Consider the cranial parasympathetic system. State the ganglia that oculomotor , facial and glossopharnygeal nerve pass through and their effector organ

What is special about the location of the ganglia and effector organ?

A

Oculomotor nerve synapses at the ciliary ganglion and sphincter pupillae for pupil constriction

Facial nerve synapses at the pterygopalatine ganglion and lacrimal gland for tears. Alternatively, it can synapse at the submandibular ganglion and submandibular gland for watery saliva.

Glossopharyngeal nerve synapses at the optic ganglion and the parotid gland for watery saliva

! Close proximity of ganglia to effector organ

22
Q

Describe parasympathetic preganglionic fibres

A

Neurons within brainstem or grey matter of spinal cord (forms S2-S4 spinal nerves)

All ganglia located close to target organ
Brainstem - cranial nerves - short postgang fibre- head, heart, lungs, abdomen

Spinal cord - pelvic splanchnic nerves - short postgang fibre- pelvic organs

23
Q

Describe the sacral parasympathetic fibres

A

From sacral spinal cord
Preganglionic fibres exit via pelvic splanchnic nerves to pelvic organs
From pelvic plexus over viscera
Preganglionic fibres synapse in walls of target organs

24
Q

Describe the enteric nervous system

A

(from most superficial to least)
Longitudinal muscle
Auerbach’s plexus - regulates muscle contraction
Circular muscle
Meissner’s plexus- regulates glandular secretions
Mucosa

Contains 10-100 billion neurons
Retains functions after all central connections severed
TRULY AUTONOMIC

25
Q

Describe the sacral parasympathetic function

A

Urination form bladder

  • contraction of bladder wall
  • inhibition to bladder sphincter

Defecation from rectum
-inhibition of rectal sphincter

Sexual function
-vasodilation in erectile tissues (example of balance between parasympathetic and sympathetic divisions)

26
Q

Outline the control of the ANS

A 
Cerebral cortex (involuntary response ie blushing and pallor in fear)
THEN
Hypothalamus -autonomic regulation
Autonomic centres in brain
Preganglionic neurons
Postganglionic neurons
Effector organs 
Sensory ganglia
Autonomic centres in brain
Hypothalamus -autonomic regulation

202T2 (11 decks)

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