PNS1 Flashcards
How many pairs of cranial nerves are there?
12
Bundles of axons in the CNS are referred to as “tracts.” What are they called in the PNS?
Nerves
Collections of nerve cell bodies in the CNS are called Nuclei. What are they called in the PNS?
Ganglion
What does each of the following stand for? What is the purpose of each?
- GSA
- GVA
- GSE
- GVE
- GSA = General Somatic Afferent nerves, which cary signals from joints, skin, and skeletal muscle to CNS
- GVA = General Viserosensory Afferent nerves, which carry signals from viscera and vessels to CNS
- GSE = General Somatomotor Efferent nerves, which carry signals from CNS to skeletomuscle
- GVE = General Viscerosensroy Efferent nerves, which carry signals from CNS to glands, smooth muscle, & cardiac muscle
At what vertebral level does the spinal cord terminate? What does it terminate into?
The cord tapers caudally at the L1-L2 intervertebral level and terminates into the CONUS MEDULLARIS.
Arising from each segment of the spinal cord are the (1) GSA & (2) GSE fibers which, respectively, supply
- a specific area of body wall called the?
- and a specific muscle mass called the?
- The GSA supply the specific area of body wall called the DERMATOME
- The GSE supplies the specific muscle mass called the MYOTOME
What are the two main differences b/t ROOTS and RAMI?
Roots: 1. Lie within the vertebral column
2. Afferent and Efferent Fibers in roots = segregated
Rami: 1. Outside of vertebral column
2. Contain a mixture of somatic afferent and efferent fibers.
Which is larger the Ventral primary ramus or the Dorsal primary ramus? What is the muscle group that each supplies?
- The Ventral (anterior) Ramus is larger and supplies the HYPAXIAL Muscles. Note: Also supplies anterolateral body wall and extremities
- The Dorsal (posterior) Ramus is smaller and supplies the EPAXIAL Muscles. Note: Also supplies skin of the posterior scalp, facet joints and the posterior ligaments of the spine
In the somatic system, how many neurons are there between the CNS and either the skeletal muscles innervated by GSE fibers or Sensory recptors innervated by GSA fibers?
ONE
-There is Only 1 neuron b/t the CNS and the PNS endpoint
Cutaneous receptors are responsible for transducing action potentials from what part of the body to the CNS? What are the receptors that are responsible for creates the action potential that the cutaneous receptors receive? What is unique about these receptors?
Cutaneous nerves carry information from EXTEROCEPTORS, in the SKIN, to the CNS.
-EACH exteroceptor is sensitive to a PARTICULAR form of physical energy or STIMULUS.
What stimuli do each of the following exteroceptors respond to?
- Mechanoreceptors?
- Thermoreceptors?
- Nociceptors?
- Deformation or displacement of skin
- Changes in temperature
- Responds to stimuli that damage tissue
(–>PAIN)
The Cutaneous Receptors are continuous with peripheral processes of what?
-The soma of the above peripheral processes are located in the Dorsal or Ventral root ganglia?
(Pseudounipolar) Sensory Neurons;
-These Sensory Neurons have soma that are located in the DORSAL Root (Spinal) Ganglia.
What is a dorsal root (spinal) GANGLION?
Each Dorsal Root GANGLION is a collection of Pseudounipolar Sensory Neurons located on the dorsal root in an intervertebral foramen, just proximal to the mixed spinal nerve.
- Note: In the Dorsal (posterior) Root there are only Afferent fibers b/c the dorsal root receives information from the periphery and passes it onto the Dorsal Horn in the CNS
- Ganglion = collection of functionally related nerve cell bodies that are located OUTSIDE of the CNS
Once in the CNS the inputs from the Dorsal Root Ganglia are segregated how?
by Modality (or function).
What is Referred VISCERAL Pain?
It is pain felt far away from the visceral source caused by communication between Visceral Afferent nerves (viscera & vessels) and Somatic Afferent nerves (joints, skin & skeletal muscle).
-Ex. Pain from a heart attack is carried by Visceral Afferents from the source (the heart) but along its journey back to the CNS the Visceral Afferent comes in close contact with (and communicates with) a Somatic Afferent from the Left arm causing this Somatic Afferent also to signal pain to the CNS. This is why pain is felt in the left arm during a heart attack even though there is nothing wrong with the left arm.
The spinal nerves contributing to the brachial and lumbosacral plexuses innervate what?
Brachial Plexus: Innervates upper limbs
Lumbosacral plexus: Innervates lower limbs
Individual peripheral nerve fibers consist of what 3 components?
- Axons
- Neurolemma (myelinated or unmyelinated)
- ENDONEURIAL connective tissue (Endonerium)
Individual peripheral nerve fibers are bundled into FASCICLES surrounded by what dense connective tissue?
Perinerium
In addition to peripheral nerve fascicles what 3 other components are ensheathed by the outermost, thick EPINEURIUM to form each PERIPHERAL NERVE?
In addition to the fascicles peripheral nerves consist of
- Vasa Nervosum (blood vessels)
- Fatty tissue (cushioning)
- Lymphatics (Fight infections)
What caudal portion of the brain stem does the spinal cord descend from and through what foramina does it exit the skull?
The spinal cord descends from the MEDULLA OBLONGATA and exits the skull via FORAMEN MAGNUM.
The cord descends through the VERTEBRAL CANAL enclosed within what until the S2 level?
As the spinal cord descends through the Vertebral canal it is surrounded by a closed DURAL (Thecal) sac, which consists of the 3 meningeal layers (dura, arachnoid & pia), and descends to the S2 level of the spine.
T or F: Each pair of spinal nerves is derived by the convergence of fibers from both the dorsal and ventral aspects of an individual segment of the cord?
What fiber type is associated with the dorsal and the ventral horns respectively?
True.
- The Dorsal Horn receives Somatic Afferent fibers from the DORSAL (posterior) ROOT
- The Ventral Horn gives rise to Somatic Efferent fibers in the VENTRAL (anterior) ROOT
Somatomotor fibers (GSE) stimulate voluntary and what other type of contraction of skeletal muscle?
Somatomotor (GSE) fibers stimulate voluntary and REFLEX contraction of skeletal muscle
What are the two main types of information somatosensory fibers transmit to the CNS?
- Touch, pain, pressure & temp from the body wall
- Proprioception from muscles, tendons & joints. Proprioception gives the ability to know where a finger or body part is without visualizing it.
The mixed ventral and dorsal rami converge briefly to form what SMALL, mixed spinal nerve that is susceptible to spinal nerve injuries and branches into the segregated dorsal and ventral roots inside the spinal column?
The INTERVERTEBRAL (IV) FORAMEN is a small, mixed spinal nerve b/t rami and roots of the PNS.
What is a DERMATOME?
How does the fact that dermatomes overlap prevent perceptual anesthesia?
- A dermatome is the Specific Area of SKIN innervated by Somatic Afferents arising from a single pair of spinal nerves from a specific spinal cord segment.
- Dermatomes overlap so that the LOSS of a single spinal nerve or dorsal root will not cause ANESTHESIA
Exteroceptive and PROPRIOCEPTIVE inputs enter the spinal cord via the central processes of the neurons in the Dorsal Root Ganglia.
-Where are PROPRIOCEPTORS located?
Proprioceptors are located in Muscles, Tendons & Joints.
Contraction of skeletal muscle is a direct result of stimulus by what?
- Where are they located?
- What are the majority of these neurons and what does there stimulation cause?
LOWER MOTOR NEURONS cause contraction of skeletal muscle and are located in either the Brainstem or Spinal Cord.
Most lower motor neurons are a particular type that innervate muscle that allow for skeletal movement. -What is the particular motor neuron?
-What is the particular muscle fiber whose contraction generates tension allowing for skeletal movement?
Most of these Lower Motor Neurons are
ALPHA MOTOR NEURONS innervating EXTRAFUSAL MUSCLE FIBERS whose contraction generates Tension allowing for skeletal movement.
