Somatic and Autonomic Nervous System Flashcards
What structurally composes nervous system?
CNS- brain and spinal cord
PNS- peripheral nervous system- nerve fibers and cell bodies outside CNS that conduct impulses to or away from CNS
What funcitonally composes nervous system
- Somatic nervous system (SNS)- voluntary system
- carries sensation from skin and joints
- supplies innervation to skeletal muscle
- Autonomic nervous system (ANS)-involuntary/visceral nervous system
- innervates smooth muscle, glands, viscera
What is the structure and function of neurons??
- Dendrites carry impulses to cell body
- Axons carry impulses away from cell body
- Some have layers of lipid and protein (myelin sheath) that increase velocity and impulse conduction
- Communicate with eachother via synapses via release of NT
- excite/inhibit another neuron to continue/terminate impulse
What are the various types of neuron cells
- Bipolar neurons
- Unipolar neurons
- Multipolar neurons
What are bipolar neurons?
- “Special” sensory: found in olfactory epithelium, retina, inner ear
- interneurons of spinal cord
- one dendrite and one axon
What are unipolar (psudounipolar) neurons?
“General” sensory neurons of PNS
Found in spinal and cranial nerve ganglia
What are multipolar neurons?
Most common in CNS
Motor cells in anterior and lateral horns of spinal cord and autonomic ganglion cells
Multiple dendrites and only one axon (motoneuron)
What are neuroglia?
Glial cells
More abundant than neurons
Nonneuronal, nonexcitable scaffolding of nervous tissue
- Support, insulate and nourish neurons
What is structure of peripheral nervous system?
- Consists of nerve fibers/axons and nerve cell bodies that connect CNS with peripheral structures
- Axons either myelinated (schwann cells) or unmyelinated (schwann cells that do not produce myelin)
- Collection of nerve bodies outside of CNS is called ganglia
- Ganglia can be either motor or sensory
- Contains cranial (12 pairs) or spinal nerves (31 pairs)
What is structure of CNS? Difference in gray/white matter? Difference in gray/white matter in brian v spinal cord?
- Collection of nerve cell bodies called a NUCLEUS
- GRAY MATTER
- Bundle of nerve fibers/axons connecting neighboring or distanc nuclei is called a TRACT
- FORMS WHITE MATTER
- Spinal cord: gray matter internal H (butterfly) with dorsal/posterior and ventral/anterior gray horns, surrounded by white matter
- Brain: gray matter surrounds white matter
Where is gray matter in spinal cord? White matter?
Gray matter (nucleus/cellbodies) is internal H with dorsal/posterior and ventral/anterior gray horns
Surrounded by white matter (tracts)
Where is gray/white matter in brain?
Gray matter surrounds white matter
A tract is ___ ___
white matter
A collection of nerve cell bodies inside CNS is called a ____ and it is ___ ___
nucleus; gray matter
What is the somatic nervous system
- Voluntary nervous system
- Composed somatic parts CNS and PNS
- Provides general sensory and motor innervation to all parts of body
- excpet: viscera in body cavities, smooth muscle and glands
*
- excpet: viscera in body cavities, smooth muscle and glands
What do the general somatic sensory fibers transmit? Another name for them?
Afferent fibers that transmit sensations of touch, pain, temperature and position FROM sensory receptors
What do general somatic motor fibers do? Another name for them
Efferent fibers that stimulate skeletal (voluntary) muscle exclusively
How are laminae of spinal cord divided?
10 laminae
I-VI= dorasal gray matter= somatic sensory fibers
VII-IX ventral gray matter= somatic motor fibers
What are the somatic sensory fibers located in the spinal cord (which laminae)?
I-VI laminae, dorsal gray matter= somatic sensory fibers
- Dorsal root of spinal nerve carries afferent sensory signals
What are somatic motor fibers located?
VII-IX laminae, ventral gray matter= somatic motor fibers
- Ventral root of spinal nerve carries EFFERENT motor signals
- Laminae X surrounds central canal and contains neuroglial cells and does nto play role in relay of info
What are the tracts of the spinal cord?
- White matter contains axons of ascending and descending tracts
- Ascending contains sensory
- Descending contains motor
- Divided into dorsal, lateral and ventral column
Which tracts are senosry/afferent tracts?
- Dorsal column: Gracilis and Cuneatus
- Lateral spinothalamic tract
- ventral spinothalamic tract
- tract lissaeur
What is the dorsal column tract?
Gracilis and Cuneatus
- Sensory/Afferent
- Fine touch and proprioception (vibration)
- Huge and myelinated
What is lateral spinothalamic tract?
- Sensory/afferent tract
- pain (nocioceptive) and temperature (why you feel “burning” sensation first when you cut your finger)
What is ventral spinothalamic tract?
- Sensory/afferent
- Crude touch and pressure
What is tract lissauer?
Part of spinothalamic tract
What makes up the anterolateral spinothalamic tract?
Ventral and Lateral spinothalamic tracts
What is the lateral corticospinal tract?
Motor/efferent
Control limb motor
What is ventral corticospinal tract?
Motor/efferent
Posture motor
How are tracts named?
Name of tract vies clue to function
- 1st half tell where tract begins
- 2nd half tells hwere tract ends
- Corticospinal (cortex–> spine= motor)
- Spinothalamic –> spine to thalamus= sensory
Each sensory pathway consists of ___ neurons
three
What does 1st order sensory neuron do?
Links peripheral nerve to spinal cord/brainstem
What does 2nd order sensory neuron do?
Links spinal cord or brainstem to subcortical structure in brain
What does 3rd order neuron do (sensory)
LInks subcoritcal structure to cerebral cortex of brain
How many neurons compose motor pathways?
2
What are the 2 neurons in motor pathway?
Cerebral cortex to VENTRAL horn of spinal cord
Ventral horn of spinal cord to NMJ
descending neuron
3 Details of dorsal column- medial lemniscal system
- Tranmits fine touch, proprioception, vibration, pressure
- High levle of localization (detecting fly on finger), discrimination
- Large, myelinated, very fast conducting fibers
1st order neuron for dorsal column?
Enters spinal cord via dorsal root ganglion; relays sensory from dorsal column to medulla. Ascends spinal cord on IPSILATERAL side. Synapses on medulla
Pathway of 2nd order neuron for dorsal column?
Crosses to contralateral side medulla then ascends to thalamus via medial lemniscus. Synapses in thalamus
Pathway of 3rd order neuron for dorsal column?
Continues ot somatosensory cortex; postcentral gyrus in parietal lobe in brain
3 facts for anterolateral spinothalamic tract?
- Transmits pain and temperature (lateral portion); crude touch and pressure (ventral portion)
- Smaller myelinated, slower conducting fibers
- Not able to localize as well, poor discrimination (itch on back)
Pathway of 1st order neuron for anterolateral spinothalamic tract?
Enters spinal cord via dorsal root ganglion. May then ascend or descend 1-3 levels on ipsilateral side via Lissauer tract vefore synpase with 2nd order neuron in dorsal laminae 1, IV, V, VI. Pain neurons synapse in substantia gelatinosa- lamina II and III
Pathway of 2nd order neuron for anterolateral spinothalamic tract?
- Crosses to contralateral side spinal cord, ascends toward brian via either anterior or lateral spinothalamic tracts
- Synapses in thalamus (skips medulla)
Pathway for 3rd order neuron anterolateral spinothalamic tract?
Thalmus to somatosensory cortex, postcentral gyrus, or parietal lobe
What is the postcentral gyrus?
Primary somatosensory cortex
What is organization of somatosensory cortex?
- Sensory input of areas of body closer to the core are located more lateral in somatosensory cortex (nose/tongue/lip)
- Sensory input of areas of body that are far away from core are located more midline in somatosensory cortex (limbs/foot/hand/knee)
- Relative size of neurons dedicated to area is shown by size
picture of homunculus
What are other motor pathways outside of corticospinal tract known as?
Extrapyramidal tracts (think of extrapyramidal movmeents seen in ALS or Cerebral palsy)
Pathway of motor neurons in corticospinal tract?
Motor neurons exit precentral gyrus of frontal lobe, tavel through the pyramids of the medulla
- Lateral corticospinal tract- cross over to contralateral side in medulla, then descend the spinal cord via lateral corticospinal tract. Fibers innervate limbs
- Ventral corticospinal tract- remain on ipsilateral side as descends ventral corticospinal tract. Must cross over to contralateral side in spinal cord in cervial/upper thoracic area. Fibers innervate the axial muscles
What is the upper motor neuron of corticospinal tract?
Cerebral cortex to ventral horn of spinal cord
Injury above the level of medulla in corticospinal tract results in paralysis on which side of body?
paralysis on opposite side of body
Injury below level of decussation in uper motor neuron of corticospinal tract results in?
Paralysis on same side of body
When the subset of neurons in upper motor neuron of corticospinal tract (that inhibit lower motor nuerons form firing too frequently), become injured, then what results?
Spastic paralysis and positive babinski sign from loss of inhibitory neurons
What is location of lower motor neurons in corticospinal tract?
Ventral horn to NMJ
Injury to lower motor neuron on corticospinal tract causes?
Injury results in paralysis on SAME side of body
Flaccid paralysis and negative babinski sign because inhibitory neurons are intact.
What is primary motor center of brain?
Primary motor cortex
What is the organization of primary motor cortex?
- Motor input to areas of body that are far from core are more midline in motor cortex
- Motor input to areas of the body closer to the core are located more laterally in motor cortex
What types of fibers compose autonomic nervous system?
- Visceral efferent (motor) fibers that stimulate smooth (involuntary) muscle in walls of blood vessels and organs, conducting system of heart and glands
- sympathetic(thoracolumbar) divison
- parasympathetic (craniosacral) division
- Visceral afferent (sensory) fibers that conduct pain impulses from internal organs and help regulate viscerla functions
Visercal efferent (sympathetic/parasympathetic division) contain a ___ neuron system
two
pre and post synaptic neuron
Cell body of presynaptic neuron of visceral efferent is located in ?
gray matter of CNS
Cell bodies of second neuron of visceral efferent (parasym/sympathetic) reside in autonomic ganglia _____
outside the CNS
Postsynaptic axons terminate on effector organ
Cell bodies of presynaptic neurons of sympathetic visceral motor innervation is located in ______ ____ in gray matter of spinal cord
intermediolateral cell columns
Location of sympathetic visceral motor innervation on spinal cord?
Thoracolumbar region- 1st thoracic and 2/3rd lumbar segments of spinal cord
Cell bodies of postsynaptic neurons of sympatethic visceral motor innervation are located on _____ or _____ ganglia
prevertebral ; paravertebral
Paravetebral ganglia in SNS are linked to form what?
Right and left sympathetic trunks/chain on each side of vertebral column
What are prevertebral ganglia?
Plexuses that surround main branches of abdominal aorta
Relative length of SNS neurons?
Short pre, long post
Sympathetic stimulation results in wide range of responses- not well _____
localized
The adrenal (suprarenal) gland contains medullary cells that act as what?
Postsynaptic neuron
What are some effects of sympathetic visceral motor innervation?
- Fight or flight
- Skin: vasoconstriction, increases sweat gland activity, hair stands on ends, effects quick
- Head: inhibit lacrimal, nasal, salivary glands (dry mouth), stimulates eye muscle to dilate
- Thoracic organs: incrase HR, dilate BV that supply heart, dilate respiratory air tracts, inhibits muscles and glands of esophagus
- Gut: inhibits activity of muscles nad glands in viscera
- Pelvis: inhibits urination, defaction, promotes ejaculation
- Adrenal medulla: secrete great quantities of excitatory hormones into blood
Where are parasympathetic cell bodies located?
2 areas in CNS:
- CNS: cranial gray matter of brainstem
- Sacral: gray matter of spinal cord
craniosacral division
What is cranial parasympathetic outflow?
Cell bodies located in gray matter of brainstem, fibers exit CNS within cranial nerves (III, VII, IX, X)
- Provides paraympathetic innervation to head
- vagus nerve (X) provides main innervation to thoracic and abdominal viscera to left colonic flexure
What is the sacral parasympathetic outflow?
Cell bodies in gray matter of sacral segments of spinal cord (S2-S4), exit via anterior roots
- provides parasympathetic innervation to pelvic viscera, sigmoid colon and rectum
Relative size of neurons in parasympathetic system
Presynaptic long, post synaptic short
Effects of parasympathetic stimulation are very ____ and more ____ than sympathetic
specific; localized
What are some effects of parasympaethtic visceral motor innervation
- Gastric and intestin: smooth muscle contraction for peristalsis, increased secretion for digestion, allows for defacation and urination, vomiting and swallowing reflexes
- Eye: constriction of pupils
- Respiratory: coughing reflex
- Cardiac: decreases in HR and force of contraction
What is visceral afferent:
- Sensory fibers that conduct pain impulses from internal organs to help regulate visceral functions
- Responsible for autonomic reflexes
- changes in BP, HR and RR
What do visceral afferent fibers monitor for?
- Stretch
- Temperature
- Chemical changes/irritation
Interpreted as hunger, fullness, pain, nausea, weel-being
Referred pain- visceral pain ID’ed/perceived as originating form skin or outer body
Where do visceral afferent pathways travel?
Centrally along sympathetic fibers
