Ch 2 - ANS Flashcards
Two Divisions of the Nervous System
Central Nervous System (CNS) = Brain and the spinal cord
Peripheral Nervous System (PNS) = Everything outside of CNS
Sensory (Afferent) Nervous System
- Brings information INTO the NS
- Begins with events in sensory receptors in the periphery
- Simplistic Pathway: Receptors -> Brainstem -> Diecephalon -> Cortex
Motor (Efferent) Nervous System
- Carries information from the NS TO the periphery
- 2 components = Somatic (Voluntary) & Autonomic (Involuntary)
- Efferent information results in contraction of muscle or secretion by glands
2 Components of the CNS
Somatic: Voluntary, largely involves skeletal muscles
Autonomic (ANS): Involuntary, largely smooth muscle & glands
Somatic Nervous System
- Voluntary; Conscious control
- SINGLE MOTORNEURON and the skeletal muscle innervated: Each muscle fiber is innervated by a single motor neuron
- Cell body of the motor neuron is located in the CNS
- Neurotransmitter: Acetylcholine (ACh)
- Receptor: Nicotinic
- Action potential in motor neuron -> EPP in muscle fiber -> depolarization of muscle -> contraction
Neurotransmitter of Somatic Nervous System
Acetylcholine (ACh)
Neurotransmitter Receptor of Somatic Nervous System
Nicotinic
3 Divisions of the ANS
- Sympathetic
- Parasympathetic
- Enteric = is the intrinsic innervation of the GI tract
The neurotransmitter of every Preganglionic Neuron is
Acetylcholine (ACh)
The receptor of every Preganglionic Neuron is
Nicotinic
Origin of the Sympathetic Division ANS
T1-L3 (Thoracocolumbar/Adrenergic Division)
Origin of the Parasympathetic Division ANS
CN 3, 7, 9, 10, & S2-S4 (Craniosacral)
Overall function of the Sympathetic Division
Mobilize the body for activity
Responds to stressful situations
Location & Projection of Preganglionic Neurons in the Sympathetic Division
Location: Intermediolateral cell column (T1-L3)
Projection:
• Via ventral roots and white communicating rami to the sympathetic trunk or paravertebral ganglia
• Via splanchnic nerves to prevertebral (collateral) ganglia
- They synapse at both locations w/ postganglionic neurons
Location & Projection of Postganglionic Neurons in the Sympathetic Division
Location:
• Sympathetic trunk (paravertebral ganglia)
• Prevertebral (collateral) ganglia
Projection:
• In sympathetic trunk: Via gray communicating rami to spinal nerves
• In prevertebral ganglia: project to abdominal & pelvic viscera
Interneurons in the Sympathetic Division are called
Small Intensely Fluorescent (SIF) cells
Interneurons in the Sympathetic Division are located in
Sympathetic ganglia
The neurotransmitters of Sympathetic Division Interneurons are
Dopamine; they are inhibitory
Norepinephrine is the NT of these neurons
Postganglionic Sympathetic Neurons. Exception are sweat glands & some blood vessels which have cholinergic innervation
Dopamine is the NT of these cells
SIF cells
Neuro-Effector Junctions in sympathetic division are analogous to neuromuscular junctions of the somatic NS, however there are these differences
- NMJ has a discrete arrangement where there is a single motor neuron innervating muscle. In contrast, in the ANS, postganglionic neuron is diffuse w/ a branching pattern w/ beads, or varicosities, line branches.
- There is overlap in the branching networks from different postganglionic neurons, s/t target tissues may be innervated by many postganglionic neurons
- In the ANS, postsynaptic receptors are widely distributed on the target tissues, and there is no specialized region of receptors analogous to the motor end plate of skeletal muscle
The Adrenal Medulla
- Innervation originates from T5-T9
- No postganglionic neuron
- Specialized ganglion in the sympathetic division of the ANS
- Secretes 80% epinephrine & 20% norepinephrine
- ACh is NT of Preganglionic & Nicotinic is receptor
Pheochromocytoma
- Tumor of the adrenal medulla
- Secretes mainly norepinephrine
Location of Alpha1 Adrenergic Receptors
- Vascular smooth muscle of the skin
- Splanchnic regions (organs)
- GI system
- Bladder
- Radial muscle of the eye (mydriasis - when your pupils dilate)
Action of Alpha1 Adrenergic Receptors
Produce excitation; contraction/constriction
Location of Alpha2 Adrenergic Receptors
Platelets
Walls of GI tract
Action of Alpha2 Adrenergic Receptors
Produce inhibition, eg: Relaxation/dilation
Location of Beta1 Adrenergic Receptors
Sinoatrial (SA) & Atrioventricular (AV) node
Cardiac muscle
Fat cells (increase lipolysis)
Kidney (renin secretion)
Action of Beta1 Adrenergic Receptors
Excitation; increased HR, increased conduction, increased contractility
Location of Beta2 Adrenergic Receptors
Vascular smooth muscle of skeletal muscle (relaxation)
Bronchial smooth muscle (dilation)
Walls of GI tract & bladder
The parasympathetic division is aka
Craniosacral or Cholinergic System
The overall function of the Parasympathetic division is
Restoration & conservation of energy
The NT for the parasympathetic division
ACh as NT for both pre & post ganglionic synapses
Location of Nicotinic Cholinergic Receptors
- Autonomic ganglia of symp & parasymp system
- Neuromuscular junction
- Adrenal medulla
Location of Muscarinic Cholinergic Receptors
M1: salivary glands, stomach
M2: heart
M3: endocrine & exocrine glands, ciliary muscles, vascular smooth muscle
Action of Muscarinic Cholinergic Receptors
Inhibitory in heart (lower Heart Rate, lower conduction velocity in AV node)
Excitatory in smooth muscle & glands (higher GI motility, higher secretion
Length of preganglionic axons are short in the
Sympathetic Division
Length of preganglionic axons are long in the
Parasympathetic Division
Length of postganglionic axons are short in the
Parasympathetic Division
Length of postganglionic axons are long in the
Sympathetic Division
Location of autonomic ganglia in Sympathetic Division vs Parasympathetic Division
Sympathetic Division: Paravertebral & Prevertebral
Parasympathetic Division: In or near effector organs
Neurotransmitter in effector organs of Sympathetic Division vs Parasympathetic Division
Sympathetic: Norepinephrine (except sweat gland)
Parasympathetic: ACh
MOA of Alpha 1 Adrenergic Receptor
Formation of IP3 & Increase in Ca2+
MOA of Alpha 2 Adrenergic Receptor
Inhibit adenylate cyclase & decrease in cAMP
MOA of Beta 1 Adrenergic Receptor
Activation of adenylate cyclase & production of cAMP
MOA of Beta 2 Adrenergic Receptor
Activation of adenylate cyclase and production of cAMP
Formation of IP3 & Increase in Ca2+ is the MOA of which Adrenergic Receptor?
Alpha 1
Inhibition of adenylate cyclase & decrease in cAMP are the MOA of which Adrenergic Receptor?
Alpha 2
Activation of adenylate cyclase & production of cAMP are MOA of which Adrenergic Receptor?
Beta 1 & 2
Parasympathetic Cholinergic Varicosities; the small clear vesicles release
Small, clear vesicles: release the classic NT ACh
Parasympathetic Cholinergic Varicosities; the large dense-core vesicles
Non-classic neurotransmitters:
• Vasoactive intestinal peptide [VIP]
• Nitric oxide [NO]
-> Varicosities contain nitric oxide synthase and can synthesize NO on demand
MOA of Muscarinic receptor in SA node
Inhibition of adenylate cyclase, (α₂) which leads to the opening of K⁺ channels, causing repolarization, thereby ↓ing HR
MOA of Muscarinic receptor in smooth muscle & glands
Formation of IP₃ and increase intracellular Ca²⁺; (α₁)
