PNS And Spinal Cord Flashcards
What functional nerves are in the posterior horn?
Somatic afferent and visceral afferent
What functional nerves are in the anterior horn?
Visceral efferent and somatic efferent
What are the three meninge layers of peripheral nerves?
- Epineurium: most prominent around whole trunk; gives tensile strength
- Perineurium: continuous with arachnoid; blood-nerve barrier
- Endoneurium: surrounds individual fibers
What is the function of myelin?
Insulates axon membrane to increase conductivity velocity
What produces myelin in the CNS? PNS?
CNS: oligondedroglia cells
PNS: Schwann cells
What is the term for the areas between the myelin and what do these areas do?
Nodes of Ranvier; conduct the signal as it jumps from node to node
Which fibers are thicker: preganglionic autonomic or postganglionic autonomic?
Preganglionic autonomic
Which fibers are thicker: sharp pain or slow pain?
Sharp pain
Chemoreceptors are typically responsible for what?
Taste, smell, pH, metabolite concentrations
Photoreceptors are responsible for what?
Rentinal visual receptors
Thermoreceptors?
Temperature
Mechanoreceptors?
Respond to physical deformation: touch, muscle length and tension, auditory, vestibular receptors
Nociceptors?
Pain
T/F: Joints have one type of receptor that responds to position and movement.
False
Many types of receptors
What are the two components of all receptors?
- Receptive area
2. Synaptic area: where message is sent toward CNS
What is the main function of a receptor?
Turn a physical stimulus into an electrical signal the nervous system can understand
What is a receptor potential?
Describes the intensity and duration of a stimuli
What is a receptive field?
This allows the CNS to perceive the location of the stimulus.
What is the likely function of free nerve endings in muscles?
Detect muscle pain
What are the two types of encapsulated receptors in the muscles?
Muscle spindles: detect muscle length
Golgi tendon organs: detect muscle tension
What is the conus medullaris?
It is the caudal end of the cord before it narrows into the nonfunctional filum terminale
Where are the spinal cord enlargements and what are they for?
Cervical enlargement: C5-T1
Lumbar enlargement: L2-S3
More motor neurons to supply upper and lower extremities
The dorsal rootlets _______ the cord in the _____________.
Enter; posterolateral sulcus
The ventral rootlets _______ the cord from the ____________.
Leave; anterolateral sulcus
Which root has a ganglion at the coalescence of the dorsal and ventral roots?
Dorsal root ganglion: contains cell bodies of sensory neurons
How do you deduce the level of a cord lesion?
Each spinal nerve innervates one dermatome level
What is the pathway of a sensory signal?
Receptor -> afferent fibers enter dorsal root -> terminate in posterior horn or ascend to medulla
What is the pathway of a motor signal?
Signal from brain -> Anterior horn -> leave thru ventral roots
What is a reflex?
Stereotyped motor outputs, involve neural circuits only in cord
NO BRAIN
What structure do the two sides of the cord communicate through?
Anterior white commissure
What structure divides the posterior funiculi at the C and T levels?
posterior intermediate sulcus
What is the common configuration of the spinal cord?
H-shaped gray matter surrounded by white matter funiculi
What structure is only found above T6 in the spinal cord?
The posterior intermediate sulcus
What happens to the spinal cord shape as it goes from cervical to sacral?
Gets narrower from C->T
Gray matter gets larger from T->L
What is the substantia gelatinousa related with?
Pain and temperature
Which horn contains motor neurons that control skeletal muscle?
Anterior horn
What are alpha neurons and where are they found?
Muscle moving motor nuerons; found in the anterior horn
Why do the alpha neurons cluster into small groups?
Each group is indicative of innervating an individual muscle
What are the two specialized columns in the cervical anterior horns?
Spinal accessory nucleus: forms accessory nerve (caudal medulla to C5)
Phrenic nucleus: innervates diaphragm (C3,4,5… keeps the body alive)
What types of neurons are found in the intermediate gray matter (between the horns)?
Preganglionic sympathetic neurons (T1-L3) ANTERIOR
Clarke’s nucleus (T1-L2): relays proprioception of legs to cerebellum; POSTERIOR
Sacral parasympathetic nucleus (S2-S4): supply pelvic viscera; ANTERIOR
Where would you do a spinal tap?
Lumbar since spinal cord is degenerated to filum terminale
What suspends the spinal cord in the column?
denticulate ligaments
How many neurons are involved in the stretch reflex?
2 neurons and one synapse between them
What is an interneuron?
Interneurons are in all reflexes except the stretch reflex. They are in between the receptor and effector neurons
Which artery is responsible for the anterior horn? Posterior horn?
Anterior spinal artery; posterior spinal arteries
