Visceromotor Flashcards
What are the target tissues of the ANS?
Cardiac muscle - controlled by the SA node
Smooth muscle (located in blood vessels and hollow viscera
Glandular epithelium (located in skin, hollow, and solid viscera)
What structures are uniquely innervated by the sympathetic division?
- The body walls and extremities
- The adrenal medulla
- Most arterial blood vessels
How is modulation of the structures innervated only by the sympathetic division achieved?
Achieved by changes in tonic sympathetic discharge based on sensory input
What is the primary difference between the somatomotor and visceromotor pathways?
Visceromotor is a 2 neuron pathway.
What are the 2 neurons involved in the visceromotor pathway from the brainstem/spinal cord to the target tissues? where are their cell bodies?Where do their axons project?
Preganglionic: Cell body in the CNS and myelinated axon projects into an autonomic ganglion
Postganglionic: cell body in an autonomic ganglion and the unmyelinated axon projects to the target tissue.
What is the one exception to the 2 neuron pathway? Which division is it in?
On the sympathetic side, there are preganglionic neurons that synapse directly in the adrenal medulla (an endocrine gland that secretes both epinephrine and norepinephrine)
what is the organization of the synapses of the visceral motor neuron and its targets?
Unlike somatomotor system, the visceral motor neurons and their targets are not organized into discrete motor units.
terminal branches of postganglionic neurons have a series of swellings that contain neurotransmitter vesicles along their length, giving them a beaded appearance. the neurotransmitter released from these terminals cam act on effector cells at a distance of up to 100 micrometers away. Therefore the ANS exerts DIFFUSE control over target tissues.
What are the functions of the ANS?
Both divisions are tonically active, and work to maintain the internal environment within narrowly defined limits (homeostasis)
2 functions:
1) control visceral functions - regulation of cardiovascular, respiratory, digestive, urinary, and reproductive organs
2) adaptive responses to stimuli - such as light, temperature, and stress
What is the pattern of synapses between preganglionic and postganglionic neurons on the sympathetic side? What does it imply?
Preganglionic neurons branch in the periphery and synapse on many post ganglionic neurons
Postganglionic neurons receive synaptic input form many preganglionic neurons.
This tells is that the function of these neurons is diffuse.
Clinical Correlate: Reflex Sympathetic Dystrophy
- What is another name for it?
- What are the symptoms?
- What is the potential cause?
- What are the available treatments?
- Complex Regional Pain Syndrome
- Chronic, continuous, intense pain in one of the extremities; changes in the skin (color, temp, texture); joint swelling, stiffness, and motor disability (due to restriction).
- Possibly due to abnormal connections between sympathetic postganglionic neurons and nociceptive dorsal root ganglion neuron following a tissue (type 1) or nerve (type 2) injury.
- Nerve blocks that reduce sympathetic outflow.
Enteric Division
Where is it housed?
Lives in the walls of our GI tract
Enteric Division
What is it composed of?
Where do its inputs come from?
Composed of 2 separate and interconnected plexuses in the walls of the GI tract consisting of motor, sensory, and interneurons.
Relatively independent of CNS control.
Has both sympathetic and parasympathetic inputs?
Enteric Division
What is its function?
Controls the coordinated contraction and relaxation (peristalsis) of the smooth muscle within out GI tract
Involved in secretion from the glands in our GI tract
Controls blood flow in the GI tract
