Chapter 15 - Autonomic Nervous System Flashcards
1
Q
3 Parts Involved w/ ANS Reflex Arcs
A
- Autonomic unipolar sensory neurons associated w/ interoceptors
- CNS integrating center
- Two autonomic motor neurons (Pre- and post-ganglionic neurons)
2
Q
Somatic Motor Neurons
A
Single motor neuron type in PNS
- Cell body in CNS
- Axon -> skeletal muscle
- Excitatory
- Conscious control
3
Q
Autonomic Motor Neurons
A
2 motor neuron types in PNS: Pre-ganglionic & Post-ganglionic
4
Q
Pre-ganglionic ANS Motor Neuron
A
- Cell body in CNS
- Axon -> PNS ganglion
- Synapses w/ post-ganglionic neuron in gangion (*Adrenal medulla chromaffin cell is an exception)
- All pre-ganglionic axon terminals release excitatory ACh
5
Q
Post-ganglionic ANS Motor Neuron
A
- Cell body in ganglion
- Axon -> effector (Smooth/cardiac muscle, gland)
- Unconscious control
- Excitatory or inhibitory, depending on neuroendocrine state
6
Q
Neurotransmitters Released by Post-G ANS Motor Neuron
A
- Noradrenaline (Most sympathetic)
- ACh (Sympathetic cholinergic & all parasympathetic)
- Adrenaline & noradrenaline (chromaffin cells)
7
Q
Sympathetic Division of ANS
A
- Thoraco-lumbar flow
- Pre-g nerve cell bodies in lateral horns of spinal cord T1-L2
- Pre-g nerve cell axons exit spinal cord via anterior root
- Axons -> sympathetic paravertebral ganglion chain via white ramus communicans
8
Q
Pre-g fibers vs. Post-g fibers
A
- Pre-g fibers = white, because of myelination
- Post-g fibers = gray, due to no myelination
9
Q
4 Possible Pathways for Pre-g Axon (Within Sympathetic Chain Ganglia)
A
- Pre-g axon synapses w/ post-g neuron (Version 1)
- Pre-g axon synapses w/ post-g neuron (Version 2)
- Pre-g axon passes through sympathetic chain ganglion
- Pre-g axon passes through sympathetic chain ganglion w/o synapsing
10
Q
Pre-g axon synapses w/ post-g neuron (Version 1)
A
- Pre-g axon synapses w/ post-g neuron
- Post-g neuron axon leaves ganglion via gray ramus communicans going to spinal nerve
- Post-g fibers -> skin of neck, trunk & limbs via posterior & anterior rami
11
Q
Pre-g axon synapses w/ post-g neuron (Version 2)
A
- Pre-g axon synapses w/ post-g neuron
- Axon leaves ganglion via sympahetic nerve
- Post-g fibers -> thoracic cavity & above via sympathetic nerves (*Some go through ANS plexuses)
- From cervical ganglion, sympathetic cephalic periarterial nerve fibers innervate visceral effectors of the head
12
Q
Pre-g axon passes through sympathetic chain ganglion
A
Pre-g axon passes through sympathetic chain ganglion & forms a splanchic nerve to abdominopelvic organs
- Pre-g neuron’s axon synapses w/ post-g neuron in collateral ganglion (AKA “pre-vertebral ganglion”)
- Post-g fibers from collateral ganglia -> abdominopelvic viscera
- Effects: vasoconstriction, decreased digestive activity
13
Q
2 Types of Sympathetic Ganglia
A
- Sympathetic Trunk Ganglia (“Paravertebral Ganglia”)
2. Collateral Ganglia (“Pre-Vertebral”)
14
Q
5 Examples of Collateral Ganglia
A
- Celiac Ganglion: -> stomach, liver, gallbladder, pancreas & spleen
- Superior Mesenteric Ganglion: -> small intestine & prox. large intestine
- Inferior Mesenteric Ganglion: -> urinary bladder, sex organs & dist. large intestine
- Aorticorenal Ganglion: -> renal arteries & kidneys
- Renal Ganglion: -> cortex of kidneys & ureters
15
Q
Pre-g axon passes through sympathetic chain ganglion w/o synapsing
A
Pre-g axon passes through sympathetic chain ganglion w/o synapsing to post-g neuron; instead, connects directly to adrenal medulla cells (AKA “Splanchic nerve to adrenal medulla”)
16
Q
Parasympathetic Division of ANS
A
- Cranio-sacral flow
- Pre-g motor neuron cell bodies in brainstem/ gray matter of S2-S4
- Brainstem’s pre-g axons conveyed via cranial nerves 3, 7, 9, or 10
- S2-S4 pre-g axons conveyed via anterior roots of pelvic splanchic nerves
- 2 types of parasympathetic ganglia: Intramural (in wall of innervated organ) or terminal (near innervated organ)
- Vagal outflow -> heart, lungs, stomach, small & large intestine, gallbladder & pancreas
- S2-S4 out flow -> large intestine, reproductive organs, urteters & urinary bladder
17
Q
4 Examples of Terminal Ganglia
A
- CIliary ganglion of cranial nerve 3
- Pterygopalatine ganglion of cranial nerve 7
- Submandibular ganglion of cranial nerve 7
- Otic ganglion of cranial nerve 9
18
Q
2 Types of Neurotransmitters in the ANS
A
- Acetylcholine
2. Noradrenaline
19
Q
Acetylcholine
A
- Released by cholinergic neurons (both sympathetic & parasympathetic pre-g neurons)
- Released by ALL parasympathetic post-g neurons
- Released by SOME sympathetic post-g neurons
- Released at the NMJ
- Hydrolysed by acetylcholinesterase
20
Q
Nordarenaline
A
- Most sympathetic post-g neurons are adrenergic
- Also, hormonal noradrenaline released by the adrenal medullae
- Noradrenaline action ended by neuronal re-uptake & glial uptake
- Re-release/intracellular hydrolysis by monoamine oxidase/catechol-O-methyl-transferase
21
Q
4 Types of Receptors in ANS
A
- Nicotinic cholinergic
- Muscarinic cholinergic
- Alpha-adrenergic
- Beta-adrenergic
22
Q
Nicotinic Cholinergic Receptors
A
- Bind ACh
- Found on ALL sympathetic & parasympathetic post-g neurons
- Found on chromaffin cells
- Found in motor endplates at NMJ
- Neurotransmitter binding always excitatory
23
Q
Muscarinic Cholinergic Receptors
A
- Bind ACh
- Found on ALL parasympathetic effectors
- Found on a few sympathetic effectors
- Neurotransmitter binding can be excitatory, if Na+ channels opened (e.g., miosis), or inhibitory, if Cl- or K+ channels opened (e.g., relexation of GE sphincter)
24
Q
Alpha-adrenergic Receptors
A
- Bind adrenaline & noradrenaline
- Found in SOME sympathetic effectors
- Can be excitatory/inhibitory
- 2 receptor subtypes: Alpha1 & Alpha2
25
Beta-adrenergic Receptors
- Bind adrenaline & noradrenaline
- Noradrenaline is more potent in Alpha than Beta receptors
- Adrenaline is equally potent in both Alpha and Beta receptors
- Found in SOME sympathetic effectors
- Can be excitatory or inhibitory
- 3 receptor subtypes: Beta1, Beta2 & Beta3
26
2 Alpha Receptor Subtypes
1. Alpha1: Found in dermal & GI blood vessels, excitatory, cause vasoconstriction
2. Alpha2: Found in GI smooth muscle, inhibitory, decrease muscle tone & peristalsis
27
3 Beta Receptor Subtypes
1. Beta1: Found in heart & skeletal muscle, excitatory
2. Beta2: Found in bronchiolar smooth muscle, inhibitory
3. Beta3: Only found in brown fat/adipose tissue, play a role in thermogenesis
- Mechanism: mitochondrial metabolism uncoupled from ATP synthesis
28
Visceral Autonomic Reflexes (5 Parts)
1. Interoceptor = dendritic end of sensory neuron/ receptor cell/tissue
2. Sensory neuron
3. CNS interneurons = integrating center
4. 2 motor neurons: pre- & post- ganglionic
5. Visceral effector
29
Parasympathetic Visceral Reflexes (5 Types)
1. Urination & defecation
2. Light reflexes: illuminate one eye -> miosis in both eyes
3. Swallowing, coughing
4. Cardio-inhibitory reflexes
5. Digestive motor reflexes
30
Control of ANS by Higher Centers
- Hypothalamus regulates autonomic tone (balance between sympathetic & parasympathetic activity)
- Hypothalamic inputs: cerebral cortex, limbic system
- Hypothalamic outputs: hypothalamic nuclei
- Parasympathetic functions carried out by anterior & medial hypothalamic nuclei
- Sympathetic functions carried out by posterior & lateral hypothalamic nuclei
* Control is unconscious
31
6 Generalizations About the ANS
1. Both sympathetic & parasympathetic ANS divisions have excitatory or inhibitory effects
2. MOST organs receive "dual innervation"
3. Sympathetic division = more widespread & longer-lasting effects than parasympathetic
4. Sympathetic division: short pre-g fibers & long post-g fibers; Parasympathetic division: long pre-g fibers & short post-g fibers
5. Sympathetic Division = "Fight/Flight Activities"
6. Parasympathetic Division = "Rest/Digest Activities"
32
4 Examples of Sympathetic & Parasympathetic Effects (Excitatory & Inhibitory)
1. Sympathetic Excitatory: Increased HR & force
2. Sympathetic Inhibitory: Bronchodilation
3. Parasympathetic Excitatory: Contraction of GI smooth muscle
4. Parasympathetic Inhibitory: Decreased HR & force
33
Dual Innervation
- When organs are innervated by both sympathetic & parasympathetic fibers
- Each division creates opposite effects on the innervated organs
34
Difference in Degrees of Divergence
- Sympathetic Division: 1 pre-g axon synapses w/ 20+ post-g neurons
- Parasympathetic Division: 1 pre-g axon synapses w/ 5 post-g neurons
35
"Fight/Flight" Activities
- AKA "Sympathetic Stimulation/Activation", caused by noradrenaline release at specific locations + adrenaline & noradrenaline secretion into bloodstream
- Leads to:
- Increased alertness, energy & euphoria
- Inhibition of digestion & urine production
- Pupillary dilaton
- Cardio-acceleration
- Increased breathing rate, bronchodilation & skeletal muscle tone
- Glycogenolysis
- Lipolysis
36
"Rest/Digest" Activities
- AKA "Vegetative/Housekeeping" functions
- Leads to:
- Pupillary constriction (miosis)
- Digestion
- Decreased HR, BP & metabolic rate
- Urination & defecation
- Bronchoconstriction
37
8 Examples of Parasympathetic & Sympathetic Nerve Plexuses
1. Cardiac Plexus: Innervates heart
2. Pulmonary Plexus: Innervates airway
3. Esophageal Plexus: Innervates esophagus
4. Celiac Plexus: Innervates GI tract, spleen, kidneys & adrenal medulla
5. Superior Mesenteric Plexus: Innervates small & large intestine
6. Inferior Mesenteric Plexus: Innervates genitalia, ureters & kidneys
7. Hyposgastric Plexus: Innervates pelvic visceral organs
8. Renal Plexus: Innervates kidneys & ureters
38
6 Organs w/ Only Sympathetic Innervation
1. Sweat Glands
2. Arrector Pili Muscle
3. Kidney
4. Spleen
5. Blood Vessels
6. Adrenal Medullae
