Lecture 2 - Peripheral Nervous System & Spinal Cord Flashcards
From medial to lateral, list the path of a spinal nerve.
Posterior/Anterior horn → root → nerve → ramus
Afferent (sensory) nerves are in the _____ portion of the spinal cord, while efferent (motor) nerves are in the _____ portion.
- posterior (dorsal)
- anterior (ventral)
List the 4 spinal nerve types.
- visceral efferent (VE) (vessels) ←ventral, lateral horns
- somatic efferent (SE) (skeletal muscles) ← ventral horn
- somatic afferent (SA) (skin) ← dorsal horn
- visceral afferent (VA) (smooth muscles) ← dorsal
3 functional components of spinal cord gray matter:
- posterior horn (SA, VA)
- lateral horn (VE)
- anterior horn (SE)
The outermost extension of the dura that covers peripheral nerves and lends them tensile strength is the _______.
epineurium
The _______ dural layer surrounding peripheral nerves is continuous with the arachnoid mater, and possesses a blood-nerve barrier.
perineurium
Individual nerve fibers are surrounded with an _______ covering.
endoneurium
Myelin forms the membrane of _____ cells, covers up to ____ cm of an axon, and increases ________ _____ of action potentials.
- glial
- 1
- conduction velocity
In the CNS, myelin is produced by _________ cells. In the PNS, it is produced by _____ cells.
- oligodenroglial
- Schwann
The region of a neuron where an axon begins is called the ______ ______. Action potential is summated here, then carried down the axon. On myelinated neurons, it jumps across sections of myelin to exposed axon regions called _______ ___ ______.
- axon hillock
- nodes of Ranvier
“Jumping” conduction of action potentials with depolarization occuring at nodes of Ranvier down an axon is called ______ ______. It can be bi-directional.
saltatory conduction
In the PNS, Schwann cells wrap _____ neuron in myelin. In the CNS, oligodendrocytes can wrap ______ neurons in myelin.
- 1
- many
Schwann cells possess a cytoplasmic-like wrapping in the myelin sheaths called a _______. Oligodendrocytes lack this.
neurilemma
The larger the diameter of a myelin sheath, the _____ the conduction velocity.
faster
- Fastest to slowest: Ia (muscle spindle), Ib (golgi tendon organ), α (lower motor neurons), Aβ (corpuscles), γ (intrafusal fibers), δ (sharp pain, cold), C fibers (heat, pain)
__________ sense taste, smell, pH, and metabolite concentrations.
chemoreceptors
_______ are retinal visual receptors for light.
photoreceptors
______ sense temperature changes.
thermoreceptors
__________ sense physical deformation, touch, muscle length/tension, and are part of auditory/vestibular receptors.
mechanoreceptors
______ sense pain.
nociceptors
Muscle spindles are types of __________, which sense position of the body in space.
proprioceptors
Visceral receptors:
Hollow organs, such as blood vessels, possess _________ to sense changes in pressure. Other visceral receptors, such as the carotid body, detect chemical changes (ex: partial pressure of O2), and are _______.
- mechanoreceptors
- chemoreceptors
Receptor Organization:
Stimuli are detected at the _______ area. Messages are then sent through the _______ area (often a cleft). Physical stimuli (such as neurotransmitters) are then converted into electrical signals, generating _____ _____ that is decipherable by the nervous system.
- receptive
- synaptic
- receptor potential
Receptor potentials (electrical signals) tell the nervous system the ______ and ______ of a stimulus.
- intensity
- duration
Information about the location of a stimulus is recorded in the ______ _______. This information is preserved via “______” patterns in the ascending sensory pathways.
Ex: can feel specific pinprick location on patch of skin
- receptive field
- wiring
Receptor Adaptation:
Except in nociceptors (for pain), a prolonged stimulus _____ the sensitivity of receptors to that stimulus.
decreases
Receptors that adapt slowly are called ____ _____ receptors (ex: muscle spindle ). If they adapt quickly, they are ______ _______ receptors (ex: hair receptor quickly stops caring if hair is moved).
- slow adapting
- rapidly adapting
TRUE or FALSE:
The CNS can change the sensitivity of receptors.
True
_____ _____ ______ on muscles detect pain, or act as chemoreceptors for the extracellular environment.
free nerve endings
2 types of encapsulated receptors:
- muscle spindles (fastest conduction)
- golgi tendon organs (GTO) (very fast conduction)
______ ______ detect muscle LENGTH. Their anatomy is a group of intrafusal muscle fibers inside a central _______. The center also has _____ endings.
- muscle spindles
- capsule
- sensory
In muscle spindles, intrafusal fibers are attached to ______ fibers so the all muscle nerve fibers are stretched when a muscle moves.
extrafusal
At muscle-tendon junctions, muscle TENSION is detected by ______ _____ ______.
golgi tendon organs
_____ ______ ______ are receptor complexes consisting of collagen bundles within a capsule perforated by sensory fibers. Muscle contraction distorts the capsule, stimulating the fibers.
golgi tendon organs
The spinal cord is organized into segments according to ______ ______.
nerve roots
31 segments = 8C, 12T, 5L, 5S, 1Co
At the posterolateral sulcus, ______ rootlets exit the spinal cord. The anterolateral sulcus provides an exit for _____ rootlets.
- dorsal
- ventral
When rootlets coalesce, dorsal and ventral _____ are formed. The dorsal portion has a ____ _____ _____ (collection of sensory neuron cell bodies). After this, the _____ nerves are formed.
- roots
- dorsal root ganglion
- spinal
Except C1, each spinal nerve innervates one ________. These sensory regions help deduce levels of cord lesions.
dermatome
The caudal end of the spinal cord is known as the _____ _______.
conus medullaris
The spinal cord features two “enlargement” regions of increased motor neurons to supply the extremities. These are the _______ enlargement (arms) and ______ enlargement (legs).
- cervical (C5-T1) (brachial plexus)
- lumbar (L2-S3) (lumbosacral plexus)
______ fibers enter the spinal cord via dorsal roots. They stay ipsilater, and may terminate in the _______ horn, or ascend to the ______.
- sensory (afferent)
- dorsal (posterior)
- medulla
______ neurons are located in the ______ horn, leave via the ventral roots, and are modulated by descending fibers.
- motor (efferent)
- ventral (anterior)
Stereotyped motor outputs involving neural circuits within the spinal cord are called ______. One sensory signal directly determines the motor output without cranial input.
reflexes
Cervical & Thoracic Spinal Cord:
Sulci of the cervical/thoracic spinal cord on the posterior side include the posterior _______ sulcus, posterior _____ sulcus, and _________ sulcus. (Names hint position)
- median
- intermediate
- posterolateral
Cervical & Thoracic Spinal Cord:
Anterior cervical/thoracic sulci include the _______ sulcus and anterior ______ ______.
- anterolateral
- median fissure
Lumbosacral spinal cord:
Anatomical features of the lumbosacral spinal cord include the posterior _______ ______ and the posterior & anterior roots of _____ ______.
- median sulcus
- cauda equina
The anterior median fissure of the spinal cord houses the _____ _____ artery. At the innermost portion of the fissure rests the anterior ______ _______, where the two sides of the spinal cord communicate.
- anterior spinal
- white commissure
The spinal cord houses the gray matter in an ___-shape, and white matter in _______ surrounding the gray mater.
- H
- funiculi
Gray matter in the spinal cord consists mostly of ______.
interneurons
The posterior spinal gray matter houses the _____ ____ for pain/temperature.
substantia gelatinosa
The entrance to the posterior gray matter in the spinal cord is called ________ tract.
Lissauer’s
The anterior horn of the spinal cord houses ______ ______ neurons that individually innervate single skeletal muscle FIBERS.
lower motor (or alpha)
In the anterior horn, muscle SPINDLES are innervated by _______-______ neurons.
gamma motor
Two specialized columns in the anterior horn [at the cervical level] are the _____ ______ nucleus for the CN XI and the ______ nucleus for the phrenic nerve.
- spinal accessory
- phrenic
All preganglionic sympathetic neurons are located at levels ____-____, exit the _______ horn.
- T1 - L3
- anterior
All sacral preganglionic parasympathetic neurons are located at levels ____-_____, exit the ________ horn.
- S2 - S4
- anterior
A collection of neurons in the medial surface of intermediate gray matter from T1 - L2 that relays proprioceptive information to the cerebellum from the legs is _______ nucleus.
Clarke’s
Embryologically, in month ____, the spinal cord extends the entire length of the embryo. At birth, the spinal cord only extends to L1, and inferior innervation is supplied by the _____ ______ (“horse tail”) and _______ _______.
- 3
- cauda equina
- filum terminale
Pia-arachnoid extensions that suspend the spinal cord are called _______ ________.
denticulate ligaments
Conus medullaris is anchored the end of the dural sheath and coccyx via _______ _______.
filum terminale
What are the 4 components of a reflex arc? Give the location of each.
- receptor
- afferent neuron (dorsal root ganglion)
- efferent neuron (CNS)
- interneurons (gray matter b/w dorsal & ventral horns)
- note: interneurons NOT present in stretch reflex
The simplest reflex, the ______ reflex, is monosynaptic: 2 neurons with 1 synapse. It is important for posture.
- AKA, “deep tendon reflex”
stretch
If a skeletal muscle receives excessive tension, motor neurons can be inhibited via _____ _____ _____. These are a form of the reflex arc. At times, these can also be excitatory.
golgi tendon organs
The artery that lies in the anterior median sulcus of the spinal cord and is supplied by the vertebral arteries is called the ______ _______ artery.
anterior spinal
The artery that branches from the posterior inferior cerebellar artery (PICA) into the posterolateral sulcus of the spinal cord is called the _____ ______ artery.
posterior spinal
Add lower levels, the anterior and posterior spinal arteries are no longer sufficient for blood supply, and are aided by the _______ arteries.
radicular
One of the most prominent radicular arteries at T12 that supplies large amounts of the lumbosacral cord is known as the _______ _______ artery (of Adamkiewicz).
greater radicular
The lateral funiculi and anterior horns are supplied by the ______ _____ artery.
anterior spinal
The dorsal columns and posterior horns are supplied by the ______ _______ artery.
posterior spinal
