Pt3 PNS Flashcards
What is the function of the PNS?
-connect CNS to limbs/organs
-deliver sensory info to CNS
-carries motor commands to peripheral tissues/systems
-contains: receptors, nerves, peripheral ganglia outside CNS
What are the 3 different receptors and their function?
- Free nerve ending (no myelin sheath)
- Complex receptors
- Special senses receptors
-axons project via cranial and spinal nerves into CNS
-reflex functions or travel cranially to synapse in areas of the brain
What are the 4 types of sensory neurons in the PNS?
- Primary/First-Order neurons (PNS)
-primary afferent neurons that receive signal & send info to CNS - Secondary/Second-Order neurons (CNS)
-conduct impulses from CC to thalamus - Tertiary/Third-Order neurons (CNS)
-conduct impulses from thalamus to primary somatosensory cortex - Quaternary/Fourth-Order neurons (CNS)
-located in sensory area of CC
What are the neurons from the motor system divided into?
- Upper motor neuron (UMN)
-inside CNS
-motor cortex - Lower motor neuron (LMN)
-cell body in CNS & axons in PNS
-except for the post-ganglionic autonomic motor neuron
-spinal and cranial nerve
What are the differences between a somatic motor neuron and an autonomic motor neuron?
Somatic motor neuron:
-1 neuron between spinal cord & target organ
-myelinated
-ACh: contraction of skeletal muscle (excitatory transmitter)
Autonomic motor neuron:
-2 neurons between spinal cord and target organ
>preganglionic neuron (myelinated)
>postganglionic neuron (unmyelinated)
-ACh or NE: contraction of smooth/cardiac muscle or inhibition/stimulation of glandular secretion (excitatory neuro-transmitter)
What are the function of spinal nerves?
-communicate the spinal cord with sensory receptors, muscles, viscera, vessels
Describe the canine spinal cord.
36 paired spinal nerves
7 cervical
13 thoracic
7 lumbar
3 sacral
20-24 caudal
What is the function of spinal nerves?
neurons innervating the limbs (LMNs) are the cervical and lumbar intumescences
1. Cranial part of the intumescence = innervates cranial and proximal muscles of the limb
2. Caudal intumescence = innervates the distal and caudal muscles of the limb
What are spinal nerves composed of?
-roots (dorsal & ventral) [primary branches]
-main trunk
-peripheral branches
What are the fibers that compose all spinal nerves?
- Somatic sensory neurons
-enter cord through dorsal roots - Visceral sensory neurons
-enter cord through dorsal root - Somatic motor neurons
-leave cord through ventral root - Visceral motor neurons (ANS)
-leaving cord through ventral horn
peripheral ganglion located distal to each dorsal root
What is the communicating branch?
-after leaving the intervertebral foramen the main trunk gives off a dorsal and communicating branch
-the communicating branch connects the sympathetic trunk ganglion (ANS)
Describe cranial nerves.
-12 pairs
-innervates head & extend into body
-most arrive in brainstem
-CN I & II attach to the forebrain (cortex, basal nuclei, thalamus, hypothalamus)
-each nerve have specific sensory &/or motor, somatic &/or autonomic functions
What are the functions of the cranial nerves?
visual reflex
-vision and visual processing
-interneuronal connections
-parasympathetic connections for pupillary light reflex
-UMN & LMNs for eye, eyelid, & head movement
List all the cranial nerves and their functions.
“Oh, Oh, Oh, to touch and feel very good velvet, such heaven!”
CN I = olfactory nerve (S)
CN II = optic nerve (S)
CN III = oculomotor nerve (M) autonomic parasympathetic
CN IV = trochlear nerve (M)
CN V = trigeminal nerve (B)
CN VI = abducens nerve (M)
CN VII = facial nerve (B) autonomic parasympathetic
CN VIII = vestibulocochlear nerve (B)
CN IX = glossopharyngeal nerve (B) autonomic parasympathetic
CN X = vagus nerve (B) autonomic parasympathetic
CN XI = spinal accessory nerve (M)
CN XII = hypoglossal nerve (M)
(S) = 1, 2
(M) = 3, 4, 6, 11, 12
(B) = 5, 7, 8, 9, 10
