Flashcards in Intro to nervous system Deck (64):
Clusters of neuronal cell bodies are called ______.
Organized bundles of neuronal processes are termed ________.
Groups of peripheral nerve cell bodies are termed ______.
What defines a ganglion cell?
Any neuron whose soma is situated int he PNS.
What are the divisions of the 31 vertebrae?
What vertebrae control the upper limbs?
C5 - T1
What vertebrae control the lower limbs?
L2 - S3
Are there synapses in sensory ganglia?
Describe sensory (afferent) neuron structure.
Single unipolar cell body extends a process out to the tissues for sensory reception and a central process inward to the dorsal portion of the spinal cord or brain stem.
Sensory axons in a spinal nerve pass to the spinal cord through a _________, and the corresponding nerve cell bodies for a ______________ for the nerve.
dorsal (posterior) root, sensory dorsal root ganglion
Are sensory neurons unipolar or multipolar?
Are motor neurons unipolar or multipolar?
Describe motor neuron structure.
Multipolar motor neurons in VENTRAL regions of the spinal cord extend their axons outward through spinal and cranial nerves. Distance from CNS to the peripheral target is bridged by one or two neurons depending on the tissue being innervated.
Motor neurons leave the spinal cord through the _________.
Ventral (anterior) root of the nerve
What is the structure of somatic innervation?
Direct single-neuron pathway to skin and deeper musculoskeletal tissues.
What is the structure of autonomic innervation?
Indirect two-neuron pathway to cardiac muscle, smooth muscle, and glands, etc.
First neuron is in the CNS. It synapses in the PNS on a motor ganglion cell.
The sympathetic nervous system is also referred to as what?
Thoracolumbar division (axons leave at T1 - L2)
The parasympathetic nervous system is also referred to as what?
Craniosacral division (axons leave at S2 - S4)
What are GSE fibers?
General Somatic Efferent fibers: motor outflow to VOLUNTARY STRIATED muscles. They are large multipolar neurons in the ventral portion of the spinal cord. *Single neuron pathway*
What are GSA fibers?
General Somatic Afferent fibers which carry sensory inflow from non-visceral tissues. *Single neuron pathway*
What is exteroception?
Perception of the external environment, conveyed from sensory receptors int the skin. Related to temperature, touch, pressure, and pain.. These reach consciousness and are well localized.
What is proprioception?
Perception of self from stretch, acceleration, and other receptors in muscles, joints, and tendons. Can reach consciousness if desired.
What are GVE fibers?
General Visceral Efferent: fibers carry motor outflow to cardiac muscle, involuntary smooth muscle, and glands. *Two neuron pathway* originating with multipolar cells in the ventral spinal cord. Called "pre-ganglionic because they synapse with motor ganglion cells in the periphery. After the ganglion = post-ganglionic.
Describe the structure of the sympathetic motor pathway.
Preganglionic neurons leave through T1-L2 via ventral roots. These bundles are called "white" ramus communicans. Immediately outside of the spinal cord they reach a sympathetic chain/trunk of motor ganglion cells that serve ALL body levels.
All ganglion cells in the chain receive synaptic input from pre-ganglionic neurons in the ________ spinal cord.
Every spinal nerve receives a ________, a small bundle of postganglionic axons from ganglion cells in the chain. These fibers complete the general visceral motor pathway, running with the spinal nerve to reach sweat glands, the arrector pili muscles that raise the hair follicles in the skin, and invol- untary smooth muscle cells in the walls of blood vessels.
"grey" ramus communicans
It is important to remember that, although all spinal nerves receive post- ganglionic gray rami from the sympathetic chain, only the T1-L2 spinal nerves provide preganglionic white rami to the chain.
What are GVA fibers?
General Visceral Afferent fibers that carry inflow from sensory endings in the viscera and large blood vessels. *A single neuron pathway* Unipolar cells in dorsal root ganglia send central processes through dorsal roots into the dorsolateral cell column of the spinal cord. Peripheral processes reach outward along the path taken by GV motor fibers.
As a rule, visceral pain fibers retrace the paths taken by_______ to an organ, and visceral monitoring afferents follow _______ pathways.
sympathetic motor outflow,
The ventral root is formed by axons of ______ neurons growing ____ to striated voluntary muscle.
The dorsal root is formed by processes of _____ dorsal root ganglion cells growing:
1. Centrally: into dorsal portions of the cord segment
2. Peripherally: out toward sensory endings in skin and deeper musculoskeletal tissues
What kinds of fibers do primary rami contain?
Sensory AND motor
How does the dorsal primary rami (DPR) appear and what does it supply?
Smaller, supplies the deep muscles of the back and the skin that overlies them.
How does the ventral primary rami (VPR) appear and what does it supply?
Larger, supplies the walls of the chest muscle and overlying skin. Runs along intercostal space and splits to the intercostal nerve -> anterior cutaneous branch and lateral cutaneous branch.
What defines a simple reflex arc?
Involvement of 1-2 spinal cord segments. Communication via interneurons on the ipsilateral (same) side of the appropriate segment. e.g. knee jerk
What defines a complex reflex arc?
Distribution of information among several cord segments. Incoming sensory info is often transferred across the midline to initiate activity on the contralateral side.
What are the 2 layers of skin during development and which one is lost at the end of the second trimester?
Periderm is lost
What is the proliferative unit?
Stem cells (self-renewing) and other differentiating cells in the stratum basale.
What determines whether a daughter cell will remain in the stratum basale or commit to being a keratinocyte in the stratum spinosum?
Orientation of the metaphase plate during mitosis
Where are stem cells in finger and toenails?
The matrix at the base of the nail
Where are stem cells located in hair follicles
What are tonofilaments and what do they attach to?
Bundles of keratin filaments that bind to desmosomes to strengthen the stratum corneum
What component of keratohyalin granules contributes to the bundling of keratin into tonofilaments?
What do lamellar bodies (membrane-coating granules) do/contain?
Contain cholesterol sulfate and acylglucosylceramide which collectively make a lipid envelope in the stratum corneum. The lamellar bodies are *stored* in granulosum cells.
What role do keratinocytes play in forming Vitamin D?
Keratinocytes contain a Vitamin D precursor that transforms into a more active form with UV
What are Langerhans cells?
Dendritic cells common in the stratum spinosum that pass between adjacent keratinocytes
They are antigen-presenting cells and act as a first line of defense.
What is the process called of melanocyte transfer of melanin to keratinocytes?
Cytocrine secretion via their dendrites
How do melanocytes appear on histology compared to keratinocytes?
Melanocytes appear more "empty"
How is melanin formed?
Tyrosinase converts tyrosine
Melanin is _____/_____, Phaeomelanin is _____
What is a mole?
Concentrated foci of melanocytes
What are the 2 types of skin cancer?
1. Squamous and basal cell carcinoma (keratinocyte transformation)
2. Melanoma (melanocyte transformation)
What do Merkel cells do/where are they located?
Provide sense of touch, located in stratum basale.
Innervated by myelinated fibers that become unmyelinated as they cross the BM.
What are Meissner's corpuscles and what do they do?
Spiraled unmyelinated axon surrounded by a modified Schwann cell. Found in dermal papillae of fingertips, palms, lips, face - sensitive to *light* touch.
What do Pacinian Corpuscles detect?
Deep pressure and high frequency vibration. Less frequent in skin
In what layer do free nerve endings end? What do they detect?
Stratum granulosum. Detect hot/cold, pain, pressure, and itch.
What do eccrine sweat glands secrete?
Isotonic sweat from secretory cells but duct cells take up Na and Cl to make final sweat hypotonic.
What does the pilosebaceous unit include?
The hair, the hair follicle, and the sebaceous gland, all derived from the epidermis, plus the arrector pili muscle.
What is hair made of?
Dead keratinized epithelial cells
What are the phases of hair growth?
Anagen (active growing 90%)
Catagen (reduced growth 1%)
Telogen (rest 10%)
What are sebaceous glands? What are they associated with?
Holocrine glands that secrete oil. One associated with each hair follicle.
What are apocrine sweat glands?
Special glands associated with hairs in the axillae (armpits) and groin.
Unlike the eccrine sweat glands, the product of apocrine sweat glands empties into the superficial portion of the hair follicle instead of emptying directly onto the skin surface.
When do apocrine sweat glands become active?