Nervous System 7 - Autonomic Nervous System Flashcards
What are the 3 main functional parts of the PNS?
Somatic nervous system (SNS)
Autonomic nervous system (ANS)
Enteric nervous system (ENS)
What are the major differences between the somatic nervous system and the autonomic nervous system?
Sensory inputs
Target/effector organs
Pathways
Neurotransmitters
The responses of the target/effector organs to these neurotransmitters.
Label and describe how the somatic nervous system detects and responds to stimuli?
Label and describe how the autonomic nervous system detects and responds to stimuli?
List the differences between the SNS and ANS?
Identify the features of the SNS?
Neuron
Synapse
- One lower motor neuron.
- No synapse between neurons = no ganglia.
- The lower motor neuron originates in the ventral (anterior) horn of the spinal cord.
Identify the features of the SNS?
Axon
Myelinated
- Long axon transmits nerve impulses from the spinal cord to the skeletal muscle it innervates via the neuromuscular junction.
- Lower motor neuron = highly myelinated (appears white) = rapid nerve impulse transmission from the spinal cord to the target/effector.
Identify the features of the ANS?
Neuron
Synapse
- Two neurons in the pathway from the spinal cord to the target/effector.
- Synapse occurs at an autonomic ganglion.
Explain the first and second order neuron in the autonomic nervous system?
First-order neuron:
- Called the preganglionic neuron.
- Its cell is located in the CNS.
- Contains preganglionic fibres (axon).
Second-order neuron:
- Called the postganglionic neuron
- Its cell is located in an autonomic ganglion outside the CNS.
- Contains postganglionic fibres (axon) = unmyelinated (appears grey).
Explain the myelination in the autonomic nervous system and their effect?
Axons are either lightly myelinated (meaning a thin layer of myelin) or unmyelinated.
Effect:
Slower nerve impulse transmission compared to the SNS.
Identify the features of the SNS and ANS?
What is the main difference between the sympathetic & parasympathetic division in the autonomic nervous system?
Sympathetic division:
- Enables the body to cope with stress.
- Activated in conditions of ‘fight, flight or fright’.
Parasympathetic division:
- Referred to as being the ‘resting and digesting’ commander.
- Most active when an individual is calm and relaxed.
Do both divisions of the ANS contain preganglionic & postganglionic neurons and explain how they are structured?
Both the divisions contain the first and second order neurons.
Preganglionic neuron:
- First neuron in the pathway.
- Runs from the spinal cord to an autonomic ganglion to synapse with the second neuron.
Postganglionic neuron:
- Second neuron in the pathway.
- Runs from the autonomic ganglion to the target/effector.
What is dual innervation?
Most targets/effectors of the ANS receive dual innervation, meaning they receive innervation from both the parasympathetic and sympathetic divisions.
Where are the cell bodies of the preganglionic neurons found in the sympathetic ANS and explain their structure?
Location:
Found only in the lateral horn of the spinal cord from segments T1 to L2 (or L3).
Structure:
- Short preganglionic fibres.
- Long postganglionic fibres.
Where are the cell bodies of preganglionic neurons located in the sympathetic autonomic nervous system?
Located in the thoracic and upper lumbar segments of the spinal cord (T1-L3) = ‘thoracolumbar output’ to describe their site of origin.
What is the location of the axons of preganglionic neurons in the sympathetic autonomic nervous system.
The axons of these neurons (preganglionic fibres) leave the spinal cord via the ventral roots of the spinal nerves and travel only a short distance to the sympathetic ganglia.
What are ganglia and where are they located in the sympathetic autonomic nervous system?
Most ganglia are located along the vertebral column, in the two paravertebral chains (‘para’ = next to) called the right and left sympathetic chain (or sympathetic trunk).
What are the names of the 3 adjacent ganglia in the cervical sympathetic trunk?
Superior cervical ganglion
Middle cervical ganglion
Inferior cervical ganglion.
What is the function of rami communications?
Small branches that connect the sympathetic trunk and spinal nerves.
Where do the preganglionic fibres that travel to the abdominal and pelvic organs synapse at & what are their nerves called?
These fibres travel to the prevertebral ganglia (‘pre’ = in front of) to synapse.
Splanchnic nerves (‘splanchnic’ = related to viscera).
What do postganglionic fibres form & where are they located in the body?
Postganglionic fibres form multiple plexuses (webs of intertwining nerves) that are scattered throughout the body.
What are the targets/effectors of the sympathetic nervous system and what are examples of organs?
Sympathetic nervous system = part of autonomic nervous system = its targets/effectors are involuntary organs and tissues.
Examples:
Smooth muscles in the walls of hollow organs, cardiac muscle and glands.
Where are the cell bodies of preganglionic neurons located in the parasympathetic autonomic nervous system?
Located in the brainstem and the sacral spinal cord (S2-S4), so we can use the term
***aka = ‘craniosacral output’to describe their site of origin.
How many cranial nerves contain parasympathetic fibres and which cranial nerves are these?
Oculomotor (CN III)
Facial (CN VII)
Glossopharyngeal (CN IX)
Vagus nerve (CN X)
What is the name of the preganglionic neurons located in the sacrum, where do they originate from, and what is their function?
Name:
Pelvic splanchnic nerves
Origin:
Originate at the S2-S4 levels of the spinal cord.
Function:
Innervating pelvic organs and the distal aspect of the gastrointestinal tract.
What are parsympathetic ganglia?
They are the locations of the cell bodies of the postganglionic neurons of the parasympathetic nervous system.
What is the location of ganglia found in the parasympathetic autonomic nervous system?
Cranial nerves III, VII and IX:
In a few specific locations within the head.
Vagus (CN X) and pelvic splanchnic nerves:
Very close to, or inside the walls of, their targets/effectors.
What is the function of postganglionic fibres & where are they located in the body?
Form multiple plexuses (webs of intertwining nerves) that are scattered throughout the body.
What do most autonomic nerve plexuses contain?
End up containing both sympathetic and parasympathetic fibres.
What are the targets/effectors of the parasympathetic nervous system and what are examples of organs?
Parasympathetic nervous system = part of the autonomic nervous system = its targets/effectors are involuntary organs and tissues.
Example:
Smooth muscle in the walls of hollow organs, cardiac muscle and glands.
Why are the sympathetic & parasympathetic nervous system referred to as antagonistic?
They typically have opposite effects at their targets/effectors.
What does it mean by targets/effectors of the ANS have dual innervation?
This means that they are supplied by both sympathetic and parasympathetic neurons.
Describe the effects of the parasympathetic and sympathetic divisions on organs and body systems?
What are visceral reflexes & what do they involve?
Visceral reflexes are unconscious, automatic, stereotyped responses to stimulation, involving visceral receptors and targets/effectors and somewhat slower responses.
What is the process of the visceral reflex?
- Receptors:
Detect stretch, tissue damage, blood chemicals, body temperature and other internal stimuli. - Afferent neurons:
Carry signals to the (CNS). - Efferent Parasympathetic Neurons:
Carries motor signals away from the CNS to the target/receptor. - Target/Effector:
Makes adjustments in response to innervation from the efferent parasympathetic neurons.
What are the 2 roles of ANS?
- Produces motor responses.
- Responds to visceral sensory input.
Complete the sentence:
Senses associated with the viscera are ___________.
Unconscious
What is this phenomenon when strong visceral sensations rise to the level of conscious perception & provide an example?
Referred Pain:
When the sensations are often felt in unexpected places.
Example:
Strong visceral sensations from the heart will be felt as pain in the left shoulder and left arm.
What is the broadly accepted theory of ‘referred pain?’
The visceral sensory fibres from the affected organ enter at the same level of the spinal cord as the somatosensory fibres from the referred pain location.
