Exam 3: Autonomic Nervous System Flashcards
Somatic Nervous System
- innervates skeletal muscle and receives sensory information from senses
- volunatry
- CNS and PNS components
Autonomic Nervous System
- innervates the viscera (organs)
- influences smooth muscle, cardiac muscle, and glands of skin and viscera
- CNS and PNS components
- controls the 4 F’s ( Feeding, Fleeing, Fighting, Fornication)
- motor system
Hierarchy of ANS
- hypothalamus oversees ALL ANS activity, CEO/president
- middle management are the autonomic nervous centers in the brainstem (pons, mesencepalon, medulla)
- the ordinary workers are the preganglionic and postganglionic neurons
Somatic Motor
-uses a single neuron to go from spinal cord to skeletal muscle
Autonomic Motor
- uses two neurons to go from the spinal cord to the target tissue
- 1st is preganglionic neuron
- 2nd is postganglionic neuron
Preganglionic Neuron
- cell body located in CNS
- axon will synapse with the postganglionic neuron
Postganglionic Neuron
- cell body located in an autonomic ganglion
- this axon will connect to the target tissue (effector)
Why does ANS use 2 neurons in chain to an organ?
- ANS has a limited number of neurons
- ganglion=hub
- allows for convergence and divergence of ANS info
- more efficient with 2 neurons
Sympathetic Division of ANS
- thoracolumbar
- originates in lateral horns of T1-L2 region of spinal cord
- emergency situations
- fight or flight response
- mass activation effect-all parts of sympathetic divison may be turned on at once
Parasympathetic Division of ANS
- craniosacral
- some cranial nerves and parts of the sacral region of the spinal cord
- maintains a homeostatic environment
- “rest and digest” response
- parasympathetic activity is usually discrete and localized
Generalizations
- most organs are innervated by both sympathetic and parasympathetic divisions
- most cranial and spinal nerves contain both somatic and autonomic axons
Parasympathetic Division (CN’s and Sacral Components)
- cranial components are part of CN III (Oculomotor), VII (Facial), IX (Glossopharyngeal), and X (Vagus)
- sacral components from S2-S4 segments of the spinal cord
- pelvic splanchnic nerves are part of this division
Pelvic Splanchnic Nerves
-branches off spinal cord going directly to organs
Pathway for Axons
- Cell bodies of preganglionic motor neurons located in parts of certain cranial nerves, or in the sacral part of the spinal cord
- Preganglionic axons synapse in terminal ganglia which are located close to or on the organ being innervated
- Parasympathetic postganglionic axons travel from the terminal ganglia to the target organ
Sympathetic Division: Components
- cell bodies of preganglionic motor neurons in lateral horns of T1-L2 segments of spinal cord (preganglionic axons exit to spinal nerve then go into the
- white rami
- sympathetic trunks
- gray rami
- splanchnic nerve
- prevertebral (collateral) ganglia
- sympathetic postganglionic axons
White Rami
- runs from spinal nerve to sympathetic trunk
- entrance ramp
- axons are myelinated (white)
Sympathetic Trunks
- long chains of axons on either side of vertebral column
- sympathetic trunk (paravertebral) ganglia
Gray Rami
- runs form the sympathetic trunk to a spinal nerve
- sympathetic postganglionic axons
- exit ramp
- axons are unmyelinated (gray)
Splanchnic Nerves
-preganglionic axons that do not synapse in the sympathetic trunk ganglia
Prevertebral (Collateral) Ganglia
- splanchnic nerves synapse here
- located in front of vertebral column
Sympathetic Postganglionic Axons
-travel directly to target organ
Pathways for Preganglionic Sympathetic Axons
- all preganglionic axons enter the sympathetic trunk via the white ramus
- some synapse in the sympathetic trunk (and leave through the gray rami) to spinal nerves
- some preganglionic axons leave sympathetic trunk as splanchnic nerves, go to prevertebral ganglia to synapse
