Download Adrenal Medulla

12-Mar-17
ADRENAL MEDULLA
NERVOUS SYSTEM
Anatomical Subdivision
Central Nervous
System
 Brain
 Spinal Cord
Peripheral Nervous System
 Cranial Nerves (12 pairs)
 Spinal Nerves
 Associated Ganglia
NERVOUS SYSTEM
Functional Subdivision
Somatic Nervous
System
 Controls voluntary activities
Autonomic Nervous System
 Controls involuntary activities
 Sympathetic NS
 Parasympathetic NS
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Adrenal Medulla –
modified postganglionic cells of Sympathetic NS
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Sympathetic Nervous System
General Organization
• Two Paravertebral chains of ganglia
• Prevertebral Ganglia
• Nerves from ganglia to diff. int. organs
Origin of Nerve Fibers
• T1 to L2 segments – Lateral Horn
Neurotransmitter Secreted
• Preganglionic nerve endings
 Acetylcholine
• Postganglionic nerve endings
 Norepinephrine – 80%
 Epinephrine – 20%
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Sympathetic Nervous System
Preganglionic Neuron May:
1. terminate on postganglionic neuron in the
sympathetic chain ganglia
2. ascend or descend to higher or lower ganglia and
terminate on postganglionic neuron in the
sympathetic chain ganglia
3. pass through the sympathetic chain to prevertebral
ganglia (celiac, inferior or superior mesenteric)
4. pass through the sympathetic chain ganglia to
adrenal medulla
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EPINEPHRINE / NOREPINEPHRINE
(Sympathetic Neurotransmitters / Hormones)
POSTGANGLIONIC NERVE ENDINGS
 Norepinephrine – 80%
 Epinephrine – 20%
ADRENAL MEDULLA
 Norepinephrine – 20%
 Epinephrine – 80%
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SYNTHESIS
METABOLISM
Tyrosine derivative - CATECHOLAMINES
1. HYDROXYLATION
Tyrosine
Tyrosine
Hydroxylase
2. DECARBOXYLATION
DOPA
Normetanephrine
DOPA(Dihydroxyphenylalanine)
DOPA
Decarboxylase
COMT
Norepinephrine
Dopamine
Dihyroxy
Mandelic Acid
3. HYDROXYLATION
Dopamine
Dopamine
β-Hydroxylase
Norepinephrine
4. METHYLATION
MAO
Epinephrine
Vanillyl
Mandelic
Acid
MAO
COMT
Phenylethonalamine
Norepinephrine N-methyl transferase
Metanephrine
Epinephrine
* Phenylethonalamine N-methyl transferase
is not present in Sympathetic Postganglionic Neurons
ADRNERGIC RECEPTORS
α
α1
α2
Epinephrine
Norepinephrine
β1 > β 2 > α
α1 > α2 > β 1
β
β1
β2
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Location of Adrenergic Receptors
α – receptors
α1
•
•
•
•
•
•
•
•
Arterioles of most organs
Sweat glands
Salivary glands
Iris
Uterus
Fat cells
Coronary arterioles
Liver
α2
•
•
•
•
•
•
Adrenergic axon terminals
Platelets
Brain
Intestine
Pancreatic Islets
Coronary arterioles
Excitatory & Inhibitory Effects of ‘α’ receptor
stimulation
Excitatory
• Blood Vessels
(vasoconstriction)
• Smooth muscle sphincter
of GIT & Bladder
Location of Adrenergic Receptors
β – receptors
Inhibitory
• Pancreas
– ↓ Exocrine secretion
– ↓ Insulin secretion
β1
• Heart
– Pacemaker
– Myocardium
• JG cells
• Adipose tissue
β2
• Arterioles of
•
•
•
•
•
•
•
•
Heart
Skin
Lung
Skeletal Muscles
Lung – airways
Intestine / Liver
Pancreatic Islets
Uterus
Excitatory & Inhibitory Effects of ‘β’ receptor
stimulation
β1 Excitatory
• Heart
– ↑ chronotropic
– ↑ ionotropic
• Adipose Tissue
– Lipolysis
β2 Excitatory
β2 Inhibitory
• GIT
– ↓ Motility
– ↓ Blood flow
– ↓ secretion
• Glycogenolysis
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Effects of ‘α’ and ‘β’ receptor stimulation
β – Receptor
α – Receptor
Normal State – 3 A’s
Arouse
Awake
Alert
 Vasoconstriction
 Iris dilatation
 Intestinal sphincter
 relaxation
 Pilomotor contraction
 Urinary bladder
 Sphincter contraction
 Uterus contraction
 pregnant
Epinephrine – 4th A
Anxiety
Epinephrine
Norepinephrine
Less
Pronounced
Pronounced
Pronounced
Less
Pronounced
Vasodilatation – β2
↑ Heart rate – β1
↑ Myocardial contractility – β1
Intestinal contraction – β2
Calorigenic – β2
Glycogenolysis – β2
Lipolysis – β1
Urinary bladder wall
relaxation – β2
 Uterus relaxation – β2
(pregnant & non pregnant)








α - Receptor
Vasoconstriction
Intestinal Muscle
Relaxation
Pupillary dilatation
β - Receptor
Vasodilatation
Heart
( ↑ rate & ↑ force )
Bronchial
contraction
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