Organization of the Nervous System Flashcards
Components of CNS
Brain and spinal cord
Spinal nerves are not part of the CNS
Components of PNS
All other tissue besides brain and spinal cord
Describe the flow and type of information in the Nervous System
- Information come from PNS to CNS via Afferents/sensory ( Input)
- Input information can either be unconscious ( from internal enivroment of body, not discretely aware of ) or conscious ( from temp, pain, touch, etc receptors , can be discretely sensed)
- afferent PNS info is processed in CNS
- CNS responds to stimuli/change in body and is mediated via Efferent/Motor ( output)
- Output information can either innverate voluntary ( skeletal) or involuntary muscles/viscera ( cardiac, smooth muscle) muscle
- Two divisions in involuntary motor pathway are PNS ( rest and digest) and SNS ( fight or flight). PNS and SNS are part of the ANS
- There is special nervous system for GI tract called the Enteric Nervous System or ENS.
Parts of the brain
- Cerebrum
- Diencephalon ( thalamus, hypothalamus)
- Cerebullum
- Brainstem ( midbrain, pons, and medulla oblongata)
Where does the the spinal cord proper end?
Spinal cord proper ends at L1/2
Cauda Equina and Conus Medularis
spinal nerves the continue past the spinal cord proper are called the Cauda Equina and very tip is called conus medularis
Where is the spinal cord enlarged and why
Cervical and lumbar regions of spinal cord are enlarged b/c have nerves that innervate the arms and legs
Name the 3 meninges of the CNS ( brain and spinal cord)
From outermost to innermost layer
- Dura Mater ( “tough mother”)-tough covering
- Arachnoid Mater-thin meshwork
- Pia Mater-very thin, touches spinal cord, brain
Name all the layers and spaces of the CNS
From outermost to innermost
- Extradural space-outside of menignes, has vessels, nerves, and fat. Fills space w/in v. canal
- Dura mater
- Subdural space-potential space, not a true space but can become one when something goes wrong
- Arachnoid Mater
- Subarachnoid space-has CSF, can have too little or too much or become infected
- Pia Mater
Describe the Lumbar Puncture
Clincial procedure used to test for infection
Needle is inserted at L3/4 or L4/5 level to avoid injury to spinal cord
How do efferent nerves travel to spinal cord?
Anterior/ventral root of spinal cord
somatic and visceral efferents travel this way
How do afferent nerves travel from the spinal cord?
Posterior/dorsal roots of spinal cord
somatic and visceral afferents both travel this way
Dorsal root ganglion
located in dorsal root of spinal nerve and has cell bodies of sensory neurons
What are spinal nerves?
31 pairs of nerves that exit spinal cord
They are NOT part of spinal cord as well as CNS
Number and names spinal nerves
31 pairs of spinal nerves 8 cervical spinal nerves ( C1-C8) 12 thoracic spinal nerves ( T1-T12) 5 Lumbar spinal nerves ( L1-L5) 5 sacral spinal nerves ( S1-S5) 1 coccygeal nerve
General Exit Path of Spinal Nerves based on Vertebra
C1 – C7 spinal nerves exit superior to their vertebra
C8 spinal nerve exits below the C7 vertebra
T1 and onward exit inferior to their vertebra.
General Path of Spinal Nerves
- L and R Rootlets
- L and R Anterior/Posterior Root
- L and R Posterior Root Ganglion ( only in posterior root)
- L and R Spinal Nerve ( very short)
- L and R Anterior/Posterior Rami
Difference between Anterior and Posterior Rami
Anterior ramus is larger than Posterior ramus
Anterior Ramus innervates voluntary muscles circumferentially to front of body and limbs
Posterior Ramus innervates voluntary muscles in back, deep back, skin of back
What type of neurons travel in spinal nerve, ventral and dorsal ramus
All types!!!!!
somatic and visceral afferents
somatic and visceral efferents
2 types of nerve plexuses are ______
- Visceral
2. Somatic
What is a nerve plexus
Collection of intersecting nerves in PNS that control a specific visceral or somatic target in body
Examples of somatic nerve plexuses
- Brachial plexus ( anterior rami C5-T1)-upper limb
- Lumbosacral ( anterior rami L1-S4)-lower limb and pelvic region
- Cervical plexus ( anteior rami C1-C4)-neck, face
visceral nerve plexuses
Target specific visceral organs
Get information from SNS and PNS nerves
Phrenic Nerve
nerve located in cervical plexus
contains somatic motor innervation to diaphragm
called the “wandering “ nerve b/c it starts at neck and travels down to diaphragm
Path of spinal nerves a/f exiting anterior ( mostly) and posterior rami
- Cervical Plexus ( C1-C4)
- Brachial Plexus ( C5-T1)
3 Intercostal Nerves, T1-12(segmentally organized, NOT a plexus) - lumbosacral plexus ( L1-S4)
Brachial Plexus
Brachial plexus is a very complex somatic nerve plexus, travles through neck and axilla
Its organized/divided from proximal to distaL:
- Roots
- Trunks
- Divisions
- Cords
- Branches
Terminal nerves of Brachial Plexus
- Musculocutaneous
- Median
- Radial
- Ulnar
Type of Injury to Brachial Plexus
- Injury to neck-affect top of brachial plexus-muscocutaneous nerve affected
- injury of axilla/arpmit-lowe part of brachial plexus, ulnar nerve affected
4 Important nerves in Lumbosacral Plexus
- Femoral-anterior thigh
- Obturator-medial thigh
- Sciatic-posterior thigh, leg, an foot; divides into tibial and common fibular nerve; biggest nerve of body
- Pudenal -pernium and external genitalia
Dermatome
A segment of skin controlled by a single spinal nerve segment
T4 dermatome innervates nipples
T10 innervates belly button
Reflex Arc
Spontaneous movement in response to a stimulus, involving the spinal cord/brainstem via interneuron connection between afferent and efferent neurons
Bypass higher brain centers
Can be visceral or somatic
Referred Pain
Pain received at a location that is not the site of of injury or stimulus due to sharing of same dermatome
Referred pain is not the same as radiating pain!!!
Examples:
Heart Attack, feel pain in upper limb
Appendicitis, feel pain in belly button
