Describe the sensory arm of the ANS, noting the general types of receptors supplying input.
parasympathetic - promotes maintenance functions, conserves energy (rest and digest)
slow down heart rate
sympathetic - mobilizes body during stress and physical activity (fight or flight)
increases heart rate, dilates pupils, sexually aroused
What effectors can be activated by a visceral reflex arc?
smooth muscle, cardiac or glands
Compare and contrast the motor pathways of the somatic nervous system (SNS) and the autonomic nervous system (ANS).
BOTH begin the the CNS
SNS -
- consists of a single neuron (lower motor neuron)
- motor fibers are myelinated
- effectors are skeletal muscles
- NT is ACh
vs
ANS
- two motor neurons
step 1) the first neuron in the pathway is the preganglion nerve
step 2) the preganglionic nervous synapses within an automatic ganglion with a postganglionic neuron
step 3) the postganglionic neuron is the second neuron in the pathway
step 4) postganglionic axons extend from the ganglion to the effectors
What is a preganglionic neuron? a postganglionic neuron?
preganglionic fibers are myelinated and first neuron while postganglionic fibers are unmyelinated and second neuron
Which division of the ANS is sometimes called the thoracolumbar division? the craniosacral? Explain these designations.
sympathetic ; parasympathetic
Contrast the sympathetic and parasympathetic motor pathways, noting differences in origin, length of preganglionic and postganglionic fibers, location of ganglia, and neurotransmitter profiles.
in good notes
What are the CNS origins of the parasympathetic division?
from neuron cell bodies in the brain stem and sacral regions of the spinal cord
Which body regions and organs are served by parasympathetic preganglionic fibers originating with CNs III, VII, and IX?
CN 3- smooth muscles in the eye
CN 7 - stimulate the secretory activity of nasal, lacrimal, and salivary glands
CN 9- activate salivary glands (parotid glands)
Which body regions and organs are served by parasympathetic preganglionic fibers originating with CN X?
vagus
- innervates the heart, lungs and esophagus
- passes into the abdominopelvic cavity where it innervates abdominal viscera
Which body regions and organs are served by sacral parasympathetic outflow?
rectum, bladder and genitalia
Where specifically does the sympathetic division arise?
the division arises from the ventral roots of the spinal nerves T1- L2 cell bodies of the preganglionic neurons are located in the lateral horn of these cord segments
Trace the pathway of sympathetic preganglionic fibers from the spinal cord to a paravertebral ganglion
ventral roots —– ventral ramus —– white ramus communicans —- paravertebral ganglion
What are the three things that can happen to a preganglionic fiber in a paravertebral ganglion?
- It can synapse with a postganglionic neuron in the paravertebral ganglion at the same level
- It can ascend/descend the chain and synapse in another chain ganglion at a higher/lower level
- It can pass through the sympathetic trunk and synapse in a collateral ganglion anterior to the vertebral column
Which is more numerous –white rami communicantes or gray rami communicantes? Explain your answer.
gray
What is a cholinergic fiber? an adrenergic fiber?
cholinergic- fibers that release ACh
adrenergic - fibers that release Norepinephrine at a synapse
Which fibers of the ANS are cholinergic? Which are adrenergic?
cholingeric- preganglionic and all parasympathetic postganglionic fibers at synapses with their effectors
adrenergic - fibers that release norepinephrine at a synapse; released by postganglionic fibers
Identify the two types of cholinergic receptors. What is the general effect of activation (by ACh binding) of each receptor type.
- ) nicotinic - the effect of ACh binding to nicotinic receptors is always stimulatory —- excitation of the neuron or effector cell
- ) muscarinic - associated with ion channels, effect of AC binding to muscainic receptors depends on the type of ion channel that open/closes
* short lived effect due to the present of AChE in the synapse
Identify the classes and subclasses of adrenergic receptors.
Alpha :
* a1 - located in blood vessels serving the skin, mouse, abdominal viscera, kidneys, salivary glands, almost all sympathetic effectors but the heart - effects are generally EXCITATORY
* a2 - located in some vascular smooth muscle, on blood platelets, on beta cells (secrete insulin) & acing cells (digestive secretions) of the pancreas - effects are generally INHIBITORY Beta: acts y increasing intracellular cAMP levels
* B1 - located in cardiac muscles - effect is EXCITATORY * B2 - found in smooth muscle in walls of blood vessels, respiratory passages, digestive tract, bladder, urinary passages - norepinephern binding is INHIBITORY --- relaxation of smooth muscle * B3- in adipose tissue - effect is to stimulus lipolysis
When activated, which of the receptor subclasses (#26) generally produce excitation of the target cell? which generally cause inhibition?
Excitation - a1, b1, b3
Inhibition - a2, b2
Describe the physiologic effects of sympathetic activation.
Adrenal medullary cells secrete epinephrine and NE into the blood when the sympathetic division is mobilized
- increasing heart rate , raising blood glucose levels and metabolic rate
Explain why blood vessels are said to exhibit sympathetic (vasomotor) tone.
it determines whether the blood vessels constrict (dilator)
Explain why the heart at rest is said to exhibit parasympathetic (vagal) tone.
the parasympathetic is meant to control the body at rest
