A&P Chapter 60
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A&P Chapter 60
The Autonomic Nervous System
What are the two systems of the Efferent System? What do they innervate?
: Autonomic (smooth muscle, cardiac muscle, glands)
: Somatic (skeletal muscle)
What are the two systems of the autonomic nervous system?
1) Parasympathetic Nervous System
2) Sympathetic Nervous System
Is the ANS involuntary or voluntary control? Somatic?
Describe the neural pathway of a neuron in the somatic pathway
CNS (ventral root) -->
myelinated axon -->
nicotinic receptor on skeletal muscle
A somatic nerve on a skeletal muscle is excitatory/inhibitory or both?
What is the primary neurotransmitter in the somatic system?
Describe the neural pathway of a ANS-SNS neuron
short preganglionic myelinated axon -->
nicotinic receptor @ ganglion -->
longer demyelinated postganglionic axon -->
Describe the neural pathway of a ANS-PNS neuron
CN 3,7,9,10, SN 2,3,4 -->
long preganglionic myelincated axon -->
nicotinic receptor @ ganglion -->
shorter demyelinated postganglionic axon -->
muscarinic receptor on effector
The autonomic nervous system produces an excitatory/inhibitory/or both response on the effector?
Both - depending on whether the stimulation is sympathetic or parasympathetic
What are the primary neurotransmitters of the ANS?
Acetylecholine and Norepinephrine
What are the 3 divisions of the ANS?
Sympathetic, Parasympathetic, Enteric
What is the highest level of ANS integration?
Hypothalamic nuclei are responsible for:
body response to stress, blood pressure control, temp regulation
Medulla and pons responsible for:
hemodynamic and ventilatory control
integrating and maintaining the automaticity of ventilation
What is the difference in terms of quality of response of the SNS and PNS?
SNS = mass reflex responses
PNS = much more limited response
What are the 3 different types of ganglia?
1) 22 paired vertebral column
2) unpaired prevertebral ganglia
3) terminal ganglia
Describe the innervation of the adrenal gland
Spinal cord -->
preganglionic myelinated axon -->
SNS stimulation of nicotinic receptor -->
intracellular transition to post ganglionic -->
release of Epinepherine (80%) and Norepinephrine AS HORMONES
What is the difference between NE as a neurotransmitter and NE as a hormone?
NE as a hormone is released directly into the blood stream - prolonged response d/t the time need for the metabolism by COMT (catecholamine-o-methyltransferase)
What are the different types of adrenergic receptors?
a1, a2, b1, b2
What does stimulation of an a2 receptor cause?
Stimulation on the a2 receptor of a presynaptic cell -->
activation of negative feedback system -->
decreased NE released
Where are beta 1 receptors located?
heart and fat cells
What is beta 1 activation cause in the heart?
increased HR, increased contractility, increased conduction velocity
Where all are Beta 2 receptors located?
blood vessels (esp coronary and skeletal arteries)
What does stimulation of Beta 2 do to the blood vessels?
What does stimulation of beta 2 do to the bronchioles?
What does stimulation of beta 2 do to the uterus?
What does stimulation of beta 2 do to the liver?
Where are alpha 1 receptors located?
intestine and bladder
What does alpha 1 activation do to blood vessels?
What does alpha 1 activation do to the pancreas?
inhibition of insulin secretion
Where are alpha 2 receptors located?
postganglionic presynaptic sympathetic nerve ending
What does activation of alpha 2 in the CNS cause?
increase in potassium conductance --> hyper polarization --> sedation
What does activation of alpha 2 on platelets cause?
Describe the steps to the synthesis of Norepinephrine
1) tyrosine is actively transported in to the adrenergic presynaptic nerve terminal cytoplasm
2) tyrosine is converted into dopamine (2 steps in the cytoplasm)
3) Dopamine is transported into the vesicles
4) Dopamine is B-hydroxylated to NE
Describe the metabolism of Norepinephrine (3 diff ways)
1) Reuptake into the presynaptic terminal for reuse (primary mechanism)
2) metabolism by COMT (in blood) and MAO (in presynaptic nerve terminal)
3) Diffusion away from synaptic cleft
What enzyme converts NE to E?
PNM - Phenylethanolamine-N-methyltransferase
How does cortisol affect PNM?
cortisol enhances PNM
Which nerve controls 75% of the PNS?
CN III innervates ______
CN VII innervates the _______
lacrimal, nasal, and submaxillary glands
CN IX innervates the ___
CN X innervates the _____
thoracic and abdominal regions of the body
Where does the synthesis of acetylcholine occur?
presynaptic cytoplasm of preganglionic and postganglionic parasympathetic nerve endings
Describe the synthesis of Ach
In the presynaptic cytoplasm
Acetyl CoA + Choline via CAT
Acetyl CoA is synthesized in mitochondria
Choline enters cell from ECF via active transport
What are the 2 exceptions to the Sympathetic Nervous System (as far as pathway)? how are they different?
1) Sympatho-adrenal branch: preganglionic cholinergic nerve directly innervates the medulla --> release of Epi and NE as hormones
2) Sympatho-cholinergic: cholinergic (as opposed to adrenergic)