Chapter 16-17: Nerve Tracts and the Autonomic Nervous System Flashcards
What are the two types of pathways?
ascending –>conduct sensory impulses to brain
descending –>conduct motor impulses from brain
Sensory and Motor pathways vary in complexity. what are the different orders for sensory? describe them
first order neuron = sensory info to CNS
second order = receives impulse from first; spinal cord or brain stem
third order = carries signal from thalamus to cerebral cortex
what are the two somatic pathways?
upper motor neuron = in CNS
lower motor neurons = from CNS to effector
what are the three autonomic motor pathways?
upper motor neuron = in CNS
Preganglionic neuron = from CNS to peripheral ganglion
Postganglionic neuron = from ganglion to effector
What are the three Ascending Pathways?
Posterior Column Pathway
Spinothalamic Pathway
Spinocerebellar Pathway
describe Posterior Column Pathway
sides cross in medulla
- sensory impulses from skin, muscles, tendons & joints
- perceived as fine touch, pressure & body position
describe Spinothalamic pathway
sides cross in spinal cord lateral tract -sensation of pain and temperature anterior tract -sensation of crude touch and pressure
describe Spinocerebellar Pathway
-anterior tract (sides cross in spinal cord)
-posterior tract (do not cross over)
-proprioception for fine coordination
-no synapse in thalamus
(Never makes it to cortex)
(subconscious processing)
What are the three descending pathways?
Corticospinal Pathway
Medial Pathway
Lateral Pathway
describe Corticospinal pathway
- controls voluntary movements
- generally direct
- upper motor neurons synapse onto lower motor neurons
What are the three tracts in the Corticospinal pathway? describe them
- ) corticobulbar tract
- motor cranial nerves - ) lateral corticospinal tract
- motor spinal nerves
- crosses over in medulla - ) anterior corticospinal tracts
- motor spinal nerves
- does not cross-over
What does the Medial pathway do?
stimulate & inhibit same lower motor neurons as corticospinal
What are the three tracts in the Medial pathway?
1.) vestibulospinal tracts
-position & movement of head
2.) tectospinal tracts
-reflexive head movements
3.) reticulospinal tracts
gross movements & muscle tone of trunk and proximal limb
What does the Lateral pathway do?
- muscle tone & precise movements of distal upper limb
- stimulate & inhibit same lower motor neurons as corticospinal
What is the tract called that is located in the Lateral pathway? describe it
rubrospinal tracts
- start in red nucleus–> cross-over
- extend to cervical region of spinal cord
- skeletal muscles of distal upper limb
Slide 16 for tree diagram of Descending Pathways
:)
describe the Autonomic nervous system (3)
- ) Functions continuously & independently
- ) No conscious effort needed
- ) Controls visceral activities
- HR, BP, breathing rate, body temperature, response to stress
Compare the Autonomic and Somatic NS
Autonomic NS:
The pathway usually consists of two neurons
-Results in an additional synapse
-May result in additional ganglia
Somatic NS:
usually has only one peripheral motor axon
-No peripheral synapsing or ganglia
For the Autonomic Nerve fibers, what are the two neurons? describe them
Preganglionic:
- Soma in CNS
- axon leaves CNS & forms synapse in autonomic ganglia
Postganglionic:
-Soma in autonomic ganglia; axon goes to visceral effector
What are the two divisions of the Autonomic NS. briefly state when they are used
Sympathetic: for stressful situations
Parasympathetic: restores body to restful state
Do the parasympathetic and sympathetic division work together or against each other? explain
May work together
-each controlling one stage in a sequence of events
Often work antagonistically
- Cause different behaviors for different situations
- Certain organs are only innervated by one division
describe the sympathetic division
- Preganglionic fibers originate from thoracic & upper lumbar region
- T1-L2
- Soma in CNS
describe the preganglionic fibers in the sympathetic division
exit CNS join ventral root travel with motor neurons in spinal nerve leave spinal nerve Enter sympathetic ganglia
What are the sympathetic ganglia made up of?
soma of postganglionic neurons
What are the two sympathetic ganglia? describe them
- ) Chain Ganglia
- A sequence of ganglia running parallel to spinal column on either side. - ) Collateral ganglia:
- in other areas of body
How many and where are the sympathetic ganglia located on the vertebrae?
3 cervical 12 thoracic 2-5 lumbar 4-5 sacral 1 coccygeal
*Fusion causes individual variability
The chain ganglion is innervated by presynaptic fibers from nerves ___-___ ONLY
T1-L2
***NO cervical nerve input
NO input from nerve L3 or inferior
(slide 25)
Cervical, sacral, and many lumbar ganglia (are/are not) innervated by their corresponding spinal nerves. Explain if needed
are NOT.
Thoracic nerves innervate cervical ganglia
Thoracic nerves innervate thoracic ganglia
ONLY T12, L1 and L2 innervate the lumbar and sacral ganglia
______________ leave the spinal nerve and enter the _____ via the ________. Once there, one of three paths are taken. What are these three paths?
Preganglionic fibers; chain; white ramus
- ) Synapse with the ganglia at the point where they enter
- ) Travel through the chain to synapse with another ganglion in the chain
- ) Pass through and go directly to collateral ganglia or a gland
Postganglionic fibers exit via the….. (2 things)
Exit via gray ramus to spinal nerve to the effector
Exit via sympathetic nerve to the effector
describe collateral ganglia
- Presynaptic fibers go straight through chain ganglion without synapsing
- Synapse with postganglionic fibers in collateral ganglia
- Postganglionic fibers usually go to abdominal viscera
What are the three major collateral ganglia?
Celiac
Superior mesenteric
Inferior mesenteric
what do the collateral ganglia do?
Deal for the most part with digestive processes
what is a Adrenal (suprarenal) medullae
a modified collateral ganglia that stimulates the production of the hormones norepinephrine and epinephrine (go directly into the blood)
for the Adrenal (suprarenal) medullae, describe the preganglionic and postganglionic fibers
Preganglionic fibers
- go through both the chain and collateral ganglia to get to it
- straight into the medulla of the adrenal gland
Postganglionic fibers have been modified into glandular cells known as chromaffin cells
(slide 34-35 for pictures)
describe sympathetic activation
1.) CNS stimulates preganglionic neurons:
-always release ACh
-on to a nicotinic receptor
(stimulates postganglionic neurons or adrenal medulla)
2.) postganglionic neurons:
-release NE on to an adrenergic receptor
(stimulates target tissues)
What are the 5 effects of the sympathetic nervous system?
Increase alertness Energy & euphoria Excites cardiovascular & respiratory centers Increased muscle tone Mobilization of energy
summarize the sympathetic (6 things)
- ) Preganglionic fiber is short; postganglionic is long
- ) Synapsing occurs in sympathetic chain or collateral ganglia
- ) Preganglionic fiber releases Ach
- ) Postganglionic fiber releases NE
- ) Prepares body for emergencies
- ) Effects widespread & persistent
Where does the parasympathetic system originate and exit?
- Originates from neurons in midbrain, pons, medulla & sacral region of spinal cord
- exit CNS via cranial nerves 3, 7, 9 & 10 and sacral nerves 2-4
For the parasympathetic preganglionic fibers, Cranial nerves III, VII, and IX go to _________________
ganglia near target organs
eyes and facial glands
For the parasympathetic preganglionic fibers, Cranial nerve X and S2-4……. (3)
- converge in a large autonomic plexus
- Exit plexus and then to target organs
- Heart, lungs, GI tract, urinary tract, sexual organs
describe the postganglionic fibers in the parasympathetic
Usually very short
Close to, or even within, target organs
Effects of parasympathetic system are more focused and localized.
What are the effects of the parasympathetic nervous system? (9)
Constrict pupils Stimulate secretion of digestive glands Secretion of hormones promoting nutrient absorption Increase motility of digestive tract Stimulate defecation Contraction of urinary bladder Constriction of respiratory passages Reduce HR & force of contraction Sexual arousal
describe parasympatheric activation
1.) CNS stimulates preganglionic neurons:
-always release Ach
-onto a nicotinic receptor
(stimulates postganglionic neurons)
2.) Postganglionic neurons:
-release Ach
-onto a muscarinic receptor
(stimulates target tissues)
3 important facts about parasympathetic activation
- All neurons (pre- and postganglionic) release Ach
- Quickly ‘cleaned up’ after release by Acetylcholinesterase.
- Short lived effects that are localized
Summarize the parasympathetic (4)
- Presynaptic neurons are long & secrete Ach
- Postsynaptic neurons are short, produce Ach; either excitatory or inhibitory
- Innervate organs in head & abdominal pelvic region
- All ganglia in or near targets
what does dual innervation mean?
Most organs receive innervation from both divisions
in the cranial area, where do both divisions receive innervation? and via what ganglia?
Sympathetic reaches via chain ganglia
Parasympathetic reaches via cranial ganglia
in the Thoracic & abdominal region, where do both divisions receive innervation?
Sympathetic & parasympathetic mingle at plexuses
Examples:
Cardiac plexus
Esophageal plexus
describe visceral reflexes (3)
Simple functional units of the ANS
Provide an autonomic motor response
Common for digestive system
What are the two types of visceral reflexes?
Long reflexes: go to the CNS for processing
Short reflexes: are processed in the autonomic ganglion
There are many autonomic control centers in the_____
medulla
the hypothalamus regulates______
body temperature
______________control ANS when ______________
Limbic system and cerebral cortex; person is stressed
