Chapter 16-17 - Nerve Tracts and Autonomic Nervous System Flashcards
Three ways sensory and motor pathways vary in complexity (sensory)
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
Two types of sensory and motor pathways
Ascending - conduct sensory impulses to brain
Descending - conduct motor impulses from the brain
The way sensory and motor pathways vary in complexity (somatic motor pathways)
- Upper motor neuron - in CNS
2. Lower motor neurons - from CNS to effector
Sensory and motor pathways vary in complexity (AUTONOMIC MOTOR PATHWAYS)
- Upper motor neuron - in CNS
- Preganglionic neuron - from CNS to peripheral ganglion
- Postganglionic neuron - from ganglion to effector
- Sides cross in medulla
- Sensory impulses from skin, muscles, tendons and joints
- Perceived as fine touch, pressure, and body position
Posterior column pathway
What pathway is the posterior column pathway apart of?
Ascending pathway
What has tracks in the posterior white column?
Posterior column pathway
- Sides cross in spinal cord
Spinothalamic pathway
Sensation of pain and temperature
Lateral tract in the spinothalamic pathway
Spino in first part of the word
Ascending
Sensation of crude touch and pressure
Anterior tract in the spinothalamic pathway
Two tracts to the Spinocerebellar pathway
- Anterior tract - slides cross in spinal cord
2. Posterior tract - do not cross over
Proprioception for fine coordination
Spinocerebellar pathway
What does the thalamus lack?
Synapses
Because the thalamus doesn’t have synapses, what are the consequences?
- Never makes it to cortex
- Subconscious processing
Pathway that control voluntary movement
Corticospinal pathway
How is the corticospinal pathway generally direct?
Upper motor neurons synapse onto lower motor neurons
Three tracts in the Cortiocospinal pathway
- Corticobubular tract - motor cranial nerves
- Lateral corticospinal tract - motor spinal nerves, crosses over in medulla
- Anterior corticospinal tracts - motor spinal nerves, does not cross over
Stimulate and inhibit same lower motor neurons as corticospinal
Medial pathway
Three tracts in the medial pathway
Vestibulospinal tracts - position and movement of head
Tectospinal tracts - reflexive head movement
Reticulospinal tracts - gross movements and muscles tone of trunk and proximal limb
Pathway that controls muscle tone and precise movement of distal upper limbs
Lateral pathway
The tract in the Lateral Pathway
Rubrospinal tract
What does the rubrospinal tract do?
- Start in red nucleus, crossover
- Extend to cervical region of spinal cord
- Skeletal muscles of distal upper limb
- Functions continuously and independently
- No conscious effort needed
Autonomic Nervous System
What activities does the autonomic nervous system control?
Visceral activities (HR, BP, breathing rate, body temperature, and response to stress)
The differences between autonomic NS and somatic NS
Autonomic NS - two neurons (results in additional synapses and ganglia)
Somatic NS - one peripheral motor axon (no peripheral synapsing or ganglia)
Two neurons in the Autonomic Nervous System
- Preganglionic
2. Postganglionic
Location of preganglionic
- Soma in CNS
- Axon leaves CNS and forms synapse in autonomic ganglia
Location/Function of postganglionic
Soma in autonomic ganglia; axon goes to visceral effector
Two divisions of the autonomic NS
- Sympathetic - for stressful situations
2. Parasympathetic - restores body to restful state
How do the sympathetic and parasympathetic systems relate?
- May work together
- Each controlling one stage in a sequence of events
How can the sympathetic and parasympathetic divisions work antagonistically?
- Cause different behaviors for different situations
- Certain organs are only innervated by one division
Where is the sympathetic division?
- Preganglionic fibers originate from thoracic and upper lumbar region
- T1-L2
- Soma in CNS
- In sympathetic division
- The process of preganglionic fibers
- Exit CNS
- Joint ventral root
- Travel with motor neurons in spinal nerve
- Leave spinal nerve
- Enter SYMPATHETIC GANGLIA
The sympathetic ganglia are made out of what?
Made out of the soma of postganglionic neurons
Two types of sympathetic ganglia with meanings
- Chain ganglia - a sequence of ganglia running parallel to spinal column on either side
- Collateral ganglia - in other areas of body
The amount of ganglia throughout the body
- three cervical
- 12 thoracic
- 2-5 lumbar
- 4-5 sacral
- 1 coccygeal
What does fusion of sympathetic chains cause?
Individual variability
Sympathetic chains are arranged how?
One on each side
The chain ganglion is innervated by what?
Presynaptic fibers from nerves T1 to L2 ONLY
What are chain ganglion not innervated by?
- No cervical nerve input
- No input from nerve L3 or inferior
Cervical, sacral, and many lummbar ganglia are NOT innervated by what?
Their corresponding spinal nerves
Thoracic nerves innervate ?
Cervical ganglia
Thoracic nerve innervates ?
Thoracic ganglia
These things innervate the lumbar and sacral ganglia
Only T12, L1, L2
Preganglionic fibers leave the spinal nerve and enter the chain via the ___
white ramus
One in the white ramus, chain preganglionic fibers
Take one of three paths
Three paths taken in the chain preganglionic fibers
- 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
Where do the chain postganglionic fibers exit?
- Exit via gray ramus to spinal nerve to the effector
- Exit via sympathetic nerve to the effector
Process of presynaptic fibers going to the collateral ganglia
- Presynaptic fibers go straight through chain ganglion with synapsing
- Synapse with postganglionic fibers in collateral ganglia
- Postganglionic fibers usually go to abdominal viscera
Major collateral ganglia
- Celiac
- Superior mesenteric
- Inferior mesenteric
What do collateral ganglia do?
Deal for the most part with digestive processes
A modified collateral ganglia
Adrenal (suprarenal) medullae
What do the preganglionic fibers of Adrenal Medullae do?
- Go through both the chain and collateral ganglia to get to it
- Straight into the medulla of the adrenal gland
- Adrenal medullae
- Postganglionic fibers have been modified into glandular cells known as ______
Chromaffin cells
The chromaffin cells stimulate the production of the hormones _____ and _____
Epinephrine (E) and Norepinephrine (NE)
The hormones E and NE go where?
Go directly to the blood?
Sympathetic activation process
- CNS stimulates preganglionic neurons
- Always release ACh on to a nicotinic receptor - Postganglionic neurons
- Release NE on to an adrenergic receptors
Stimulates postganglionic neurons or adrenal medulla
Nicotinic receptor
Stimulates target issues on postganglionic neurons
Adrenergic receptor
Effects of Sympathetic Division
- Increase alertness
- Energy and euphoria
- Excites cardiovascular and respiratory centers
- Increased muscle tone
- Mobilization of energy
Summary of sympathetic system
- Preganglionic fiber is short; postganglionic is long
- Synapsing occurs in sympathetic chain or collateral ganglia
- Preganglionic fiber release Ach
- Postganglionic fiber release NE
- Prepares body for emergencies
- Effects widespread and is persistent
Where is the parasympathetic system?
Originates from neurons in midbrain, pons, medulla and sacral region of spinal cord
Where does the parasympathetic system exit?
- Exit CNS via cranial nerves 3, 7, 9, and 10 and Sacral nerves 2-4
Preganglionic fibers in the Parasympathetic NS
- Cranial nerves 3, 4, and 9 go to ganglia near target organs (eyes and facial glands)
- Cranial nerves 10 and S2-4 converge in a large autonomic plexus, exit plexus and then go to target organs (heart, lungs, GI tract, urinary tract, and sexual organs)
Postganglionic fibers in parasympathetic system
- Usually very short
- Close to, or even within, target organs
- Effects or parasympathetic system is more focused and localized
Functions of the parasympathetic system
- Constricts pupils
- Stimulates 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 and force of contraction
- Sexual arousal
Parasympathetic activation
- CNS stimulates preganglionic neurons
- Always release Ach onto a nicotinic receptor (stimulates postganglionic neruons) - Postganglionic neurons
- Release Ach onto a muscarinic receptor (stimulates target tissues)
Overview of parasympathetic activation
- All neurons (pre and postganglionic release Ach)
- Quickly “clean up” after release by Acetylcholinesterase
- Short lived effects that are localized
Summary of Parasympathetic
- Presynaptic neurons are long and secrete Ach
- Postsynaptic neruons are short; produce Ach; either excitatory or inhibitory
- Innervate organs in head and abdominal pelvic region
- All ganglia in or near targets
When most organs receive innervation from both division
Dual innervation
Two components to dual innervation
- Cranial area
2. Thoracic and abdominal regions
Explain cranial area in dual innervation
- Sympathetic reaches via chain ganglia
2. Parasympathetic reaches via cranial ganglia
Explain thoracic and abdominal region dual innervation in dual innervation
- Sympathetic and parasympathetic mingle at plexuses
Examples of thoracic and abdominal regions of dual innervations
- Cardiac plexus
- Esophageal plexus
Simple functional units of the ANS
Visceral Reflexes
What do visceral reflexes do?
- Provide an autonomic motor response
- Common for digestive system
Two types of visceral reflexes with their meanings
Long reflexes - go to the CNS for processing
Short reflexes - are processed in the autonomic ganglion
Control of autonomic activity
- Many control centers in medulla
- Hypothalamus regulates body temperature
- Limbic system and cerebral cortex control ANS when person stressed
