Chapter #14: Autonomic Nervous System Flashcards
Branches of the Peripheral Nervous System
Somatic and Autonomic
Somatic Nervous System (SNS)
system responsible for voluntary muscle movements and somatic reflex arcs (mostly voluntary)
Autonomic Nervous System (ANS)
-Almost all effectors are visceral (automatic)
-Do we have voluntary control over our visceral organs?
-no, we do not think about heart rate or digesting
-General function: helps maintain a stable internal environment
-Ex: regulation of heart rate, blood vessel diameter, pupil size, body temperature, increases/decreases stomach secretions
3 distinct differences between ANS and SNS
- Effector organs
- Efferent pathways and ganglia
- Neurotransmitter effects
Difference between effector organs
SNS - skeletal muscle tissue
ANS - cardiac muscle, smooth muscle, & glands
Difference between effector pathways and ganglia
SNS - single neuron extends from CNS to effector
-Motor neuron cell bodies located in CNS, axons in PNS extend to skeletal muscle
ANS - consists of two-neuron chain to reach effector
-Preganglionic neuron
-Postganglionic neuron
-Ganglia
Preganglionic neuron (ANS)
cell body in CNS, axon synapses with second motor neuron
-motor neuron, never sends sensory information
Postganglionic neuron (ANS)
cell body is outside the CNS, axon extends to effector organ
-motor neuron, never sends sensory information
Ganglia (ANS)
site of synapse between the preganglionic neuron and postganglionic neuron
Difference between neurotransmitter effects
SNS - all release acetylcholine (ACl) at synapses
-Effect is always excitatory
ANS - release norepinephrine or acetylcholine
-Effect can be excitatory or inhibitory
2 divisions of the ANS
Parasympathetic and sympathetic
Parasympathetic
-“Rest and Digest”
-Function: Directs “housekeeping” activities concerning digestion & waste elimination, heart rate & blood pressure, airway diameter, pupil diameter, reproduction, etc.
-Origin of Fibers: the brain and the sacral spinal cord
Preganglionic fibers are long, postganglionic fibers are short
-Location of Ganglia: in or near the effector organ
Is energy use high or low when the parasympathetic division is active?
low because it’s resting, not much energy is needed to use
Cranial portion of Parasympathetic Division
-Function: supplies parasympathetic fibers to head, neck, thoracic & abdominal regions
-Preganglionic fibers run in oculomotor, facial, glossopharyngeal, and vagus cranial nerves (oculomotor nerve, facial nerve, glossopharyngeal nerve, and vagus nerve)
Oculomotor nerve
-innervates smooth muscle in eyes & muscle associated with lens
-What is the effect? rest & digest, pupils become smaller, control muscles associated with iris & lens
Facial nerve
-stimulates large glands of head (salivary glands, nasal glands, lacrimal glands)
-What is the effect? stimulatory, want more saliva & fluids
Glossopharyngeal nerve
-activates parotid salivary gland
-What is the effect? stimulate the carotid, producing more saliva
Vagus Nerve
-provide fibers to neck and almost every organ in thoracic & abdominal cavities
-Cardiac plexus: supplies fibers to heart
-effect: slower/resting heart rate
-Pulmonary plexus: supplies fibers to lung
-effect: maintain slow/resting respiratory rate
-Esophageal plexus: serves esophagus
-Fibers extend into abdominal cavity from esophageal plexus - innervates liver, gallbladder, stomach, small intestine, pancreas, proximal half of large intestine
-effect: stimulatory - organs become more active
Sacral Portion of Parasympathetic division
-Form pelvic splanchnic nerves
-Function: serves pelvic organs (bladder & gonads) and distal portion half of large intestine
-What is the effect on each organ? stimulatory, waste removal is at its highest, bladder and large intestine become more active, ovaries and testes become more active and produce more gonads
Sympathetic division
-“Fight or flight”: Activated when we are excited/scared/embarrassed
-Function: Mobilizes the body for action by affecting heart rate and blood pressure, airway diameter, pupil diameter, digestion & waste elimination, reproduction, etc. (generally inhibitory)
-Origin of Fibers: thoracolumbar region of spinal cord (T1-L2)
-Preganglionic fibers are short, postganglionic fibers are long
-Cell bodies of this division form lateral horns of spinal cord
-Location of Ganglia: close to the spinal cord
How is the sympathetic division more complex than the parasympathetic division?
-Innervates smooth muscle, cardiac muscle, and glands in body cavities
-Also innervates smooth muscle and glands in superficial regions
-Sweat glands, arrector pili, smooth muscle in blood vessel walls
-controls how much blood goes to which parts of your body during fight or flight
Anatomy of sympathetic division
-Preganglionic fibers leaving the spinal cord form the sympathetic trunk
-Importance: the sympathetic trunk allows preganglionic axons to travel to spinal nerves that are higher or lower than where they originate
-Sympathetic trunk is located on both sides of the spinal cord
Pathway to sympathetic trunk
1) Preganglionic fiber exits the spinal cord
2) Fiber passes through white ramus comminucans
-Function: white ramus communicans guides the preganglionic fiber to the sympathetic trunk
3) Fiber enters the sympathetic trunk ganglion
-Function: sympathetic trunk ganglion is where the preganglionic fiber synapse with the postganglionic fiber