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What does the CNS and PNS comprise of? -PNS: cranial nerves, spinal nerves (roots+branches), peripheral nerves, and ANSWER CNS: Spinal cord and brain neuromuscular junctions Can you explain the functional organization of the PNS? -Sensory (afferent) and Motor (efferent division ANSWER Broken down to
Sensory: broken down further into Somatic and Visceral: -Somatic: General sensation in skin, body wall and limbs of:Touch Pain PressureVibration Temperature proprioception -Visceral: General sensation in viscera of: StretchPain TemperatureChemical changes Irritation
Nausea Hunger Motor: broken down further into somatic and autonomic Somatic: motor innervation to skeletal musclesautonomic: motor innervation to all smooth/cardiac muscles and glands: broken down further to sympathetic and parasympathetic What does axodendritic mean? Axosomatic? -actually make contact with axons ANSWER axodendritic- dendrites axoSOMAtic- dendrites make contact with soma What is anterograde and retrograde transport? -synthesized materials from soma to rest of cell. ANSWER anterograde- Freshly retrograde- Worn out materials returned to soma for degradation (lysosomes) Also involved in "target cell recognition" Explain generally how transport mechanisms work in neuronal cells (Make sure to namethe three structures involved) - ANSWER Microtubules are the supporting structures for neuronal transport. Motor proteins (kinesins) transport cellular cargo (e.g. vesicles)across the cellular road system, which consists of, among other components, microtubules. failure of proteins involved in transport have been linked to motor neuron disease(lateral sclerosis, amyelotrophic lateral sclerosis, or ALS)
What are synapses? What kinds of synapses are there? Give some characteristics -ANSWER Points of contact between neurons Electrical (scarce) "Gap junctions" between dendrites or somas of contiguous neurons - NO
- occurs on initial segment of axon (strong veto)
- occurs at excitatory boutons of other neurons (near presynaptic cleft) dendrodendritic: can be excitatory or inhibitory (2 types)
- one way means one of the two spines contains synaptic vesicles-reciprocal means both of the 2 spines contain synaptic vesicles somatodendritic- dendrite makes contact with soma somatosomatic- soma with other somas What are the four types of neuroglial cells in the CNS? - ANSWER Astrocytes OligodendrocytesMicroglia Ependyma What are the functions and characteristics of Astroycytes? -structural support for brain ANSWER -Provide -Provide glucose to neurons -Some processes form GLIAL LIMITING MEMBRANES -Some processes are part of synaptic contacts between neurons-Some processes contact capillaries -Very numerous Mop up K+ accumulation in extracellular spaces that accumulates during intenseactivity Participate in neurotransmitter recycling
Part of healing process in CNS injusry (gliosis) Spontaneous proliferation can give rise to a brain tumor (glioma) What are the functions and characteristics of oligodendrocytes? -MYELIN: wrap myelin sheets around axons in white matter of brain. ANSWER Form Form SATELLITE CELLS in gray matter of brain (involved in ion exchange with neurons)Unmyelinated axons are abundant in GRAY matter.
What is myelination? What cell myelinates? How long does myelination occur for in yourlife? How many axons can the cell myelinate? What disease is associated with myelin sheath breakdown? -continues well into 2nd decade of life. ANSWER -Formation starts in middle period of gestation and
-A single oligodendrocyte can lay myelin on 36+ axons. -At intervals between wrappings, axons are relatively exposed - NODES. -Myelination greatly INCREASES the speed of impulse conduction -Depolarization jumps from node to node.
- M.S. is associated with myelination breakdown What are the functions and characteristics of microglia? -microglia are very small ANSWER RESTING ACTIVATED microglia enlarge and become motile phagocytes. Activation occurs in response to INFLAMMATION or by MYELIN SHEATH BREAKDOWN What is the function and characteristics of ependymal cells? - ANSWER Line the
What is the diameter range and velocity range for unmyelinated nerves? myelinated? -ANSWER Unmyelinated Nerves: -diameters range from 0.5 to 2.0 micrometers. -Velocities range from 0.5 to 2.0 m/sec -Conduction velocity is proportional to axon diameter.-Greater volume - faster current -Wider axons have more ion channels. Myelinated nerves: -diameters range from 2.0 to 25 micrometers.-Wider fibers have longer internode segments - longer jumps creates faster conduction
Name the 5 different spinal nerve sets from superior->inferior: how many are in eachset? - ANSWER Cervical (C1-C8) Thoracic (T1-T12) Lumbar (L1-L5)Sacrum (S1-S5) Coccygeal (1) Where are spinal nerves formed at? (What two structures form the spinal nerves andwhat two structures leave the spinal nerve?) - ANSWER the anterior and posterior nerve roots exit the vertebral canal and and join at the junction to form the spinal nerve. the spinal nerve then divides into the anterior and posterior rami What is a nerve plexus? -composed of afferent and efferent fibers arising from the merging of anterior rami and ANSWER a branching network of intersecting nerves blood vessels.
What do the cervical plexuses innervate? Specifically what do the efferent and efferentbranches innervate? - ANSWER Efferent: muscles of neck and back; diaphragm (phrenic n.) Afferent: - skin of neck, upper thorax, scalp, and ear. What do the brachial plexuses innervate? What kind of paralysis is associated with thebrachial plexus? - ANSWER Begins as the anterior rami of spinal nerves C5-C8 & T1. Sensory & motor innervation to upper limb. Klumpke's paralysis (spinal birth injury at level of C8/T1 can be associated withcongenital Horner's syndrome.
What do the lumbosacral plexuses innervate? -spinal nerves T12 and L1-L4 (lumar plexus) and S1 to S4 (sacral plexus) ANSWER Begins as the anterior rami of Supply innervation to skin and muscles of the pelvis and lower limb. What are the epineurium, perineurium, and endoneurium surround? -Epineurium - loose, vascular connective tissue sheath surrounding fascicles (bundles of ANSWER nerve fibers). Perineurium - epithelial tissue (tight junctions) that surrounds each fascicle. Endoneurium - network of reticular collagenous fibers surrounding individual Schwanncells.
What percentage of nerve fibers are enclosed in myelin? What cells form myelin in thePNS? - ANSWER less than 50% Schwann (neuroglial) Speed of unmyelinated neurons vs myelinated neurons? -m/sec (impulse conduction is continuous ANSWER Unmyelinated: 15
Regeneration complete - fiber has norma appearance, but myelin segments are shorterthan originals.
What is the regenerating speed for larger nerves? Finer nerves? What happens tolikelihood of function recovery as we get closer to CNS? - ANSWER Larger nerves- 5mm/day finer- 2mm/dayless likely
What are two general characteristics of innervation to skeletal muscles? -Branches enter muscles about 1/3 down length at motor points. ANSWER
60% of axons in the branches to a given muscle are MOTOR. What is a motor unit? -brainstem together with the squad of muscle fibers it innervates. ANSWER A MOTOR UNIT is a motor neuron in the spinal cord or
Large muscles: 1200+ muscle fibers Small muscles: ≤ 12 muscle fibers What are the three types of skeletal muscle fibers? Can you give characteristics foreach? - ANSWER Slow twitch oxidative fibers -Small, rich in mitochondria and capillaries, fatigue-resistant. -Deeply placed, suitable for sustained postural activities, ex. standing. Fast glycolytic fibers -Large, mitochondria-poor, capillary-poor.-Produce brief, powerful contractions
-Predominate in superficial muscles. Intermediate fibers (fast, oxidative-glycolytic)-Properties are in-between those of other 2 types.
What is the motor end plate? What are the vesicles loaded with? What happens oncethat vesicle diffuses across? - ANSWER At the myoneural junction, each axonal branchlet forms an elongated terminal bouton containing thousands of synaptic vesiclesloaded with ACETYLCHOLINE (Ach).
Ach is extruded at great speeds and diffuses across the synaptic cleft to activatereceptors on the sarcolemma.
Sarcolemma becomes depolarized, signal carried into muscle fiber by T tubules, Ca+2released, causing sarcomere contraction.
What are some characteristics of neuromuscular spindles? What kind of muscle fibersdo they contain? - ANSWER Up to 1 cm in length
per muscle: several dozen to several hundred
-Abundant in muscles rich in slow fibers: along vertebral column, femur, tibia, intrinsichand. -Scarce where faster fibers predominate Contain intrafusal muscle fibers -Large fibers emerge from poles and anchor to connective tissue-Small ones anchored to collagenous spindle capsule
What is the efferent nerve of the muscle spindle called? Afferent? What are the twotypes of fibers that apply to the afferent nerve? - ANSWER Fusimotor axons divide to supply striated segments at both ends of intrafusal muscles. Sensory (afferent):
Within a connective tissue capsule, a single Ib caliber nerve fiber forms elaboratesprays that intertwine with tendon fiber bundles.
12+ muscle fibers insert (in series) into intracapsular tendon fibers. Ib fiber nerve endings are activated by tension developing during muscle contraction. Rate of impulse discharge is related to applied tenion; therefore, tendon endings signalthe FORCE of the muscle contraction.
What is an important function of the Golgi Tendon Organ that we went over? -Important function: to DAMPEN inherent tendency of moving limb segments to oscillate. ANSWER
What are free nerve endings? Where are they distributed and where are they located? -ANSWER Abundant in muscle tissue Distributed to intramuscular connective tissue and fascia. Conduct PAIN sensation from direct injury or accumulation of metabolites, such aslactic acid.
What are joints innervated with? What do they mediate and how does this occur? -ANSWER Joint ligaments, capsules and outer parts of intra-articular menisci are richly supplied with UNMYELINATED freely ending nerve fibers. When stimulated, they mediate PAIN and operate an excitatory reflex response toprotect the capsule.
Ex. If wrist is suddenly stretched by forced extension, motor fibers in the median andulnar nerves of the wrist are reflexly activated to cause wrist flexion.
Describe the general organization of skin innervation. What is the advantage to thisorganizational structure? - ANSWER Cutaneous branches of the spinal nerves divide
into many, many fine twigs that enter a dermal nerve plexus located at the base of thedermis.
Within the plexus, individual nerve fibers divide and overlap extensively with othersbefore terminating at higher levels of the skin.
Advantage: injury to a cutaneous nerve results in an area of anesthesia that is actuallysmaller than the anatomic territory that the injured nerve serves.
REDUNDANCY What are sensory units? - ANSWER Analogous to the motor unit. Consists of a "parent" unipolar nerve cell, a "stem" fiber, and the stem fiber's family ofnerve endings.
A given stem fiber forms the same kind of nerve ending at all of its terminals. Sensory units interdigitate so that different modalities of sensation can be perceivedfrom a given patch of skin.
What is a receptive field? What kind of relationship does receptive field size and sensoryacuity ave? - ANSWER The region from which a sensory unit can be excited.
Inverse relationship between the SIZE of the receptive field and sensory acuity (ex. 2point touch) Finger pads: RFs about 5 sq mm Forearm: RFs about 2 sq cm What are the functions of nerve endings? What happens to their perineural and myelin
What is the Merkel Cell-Neurite Complexes? Where are they located? What's specialabout their unit and can you give an example? - ANSWER Merkel cells are tactile menisci in the basal epithelium of epidermal pegs and ridges. Expanded nerve terminals are supplied to the Merkel cells. These complexes discharge continuously in response to sustained pressure (ex. holdinga pen, wearing spectacles) and are markedly sensitive to edges of objects held in the hand. Slowly adapting. What are the three kinds of encapsulated nerve endings? -Corpuscules, Ruffini Endings, and Pacinian Corpuscles ANSWER Meissner's
What kind of nerve ending is the meissner's corpuscle? Where do you find them, whatdesign do they have, slow/fast adapting, and can you give an example? - ANSWER Encapsulated Nerve Ending Most numerous in finger pads, lying in intermediate epidermal ridges. Several axons zigzag among stacks of teloglial lamellae Rapidly adapting Together with Merkel cell complexes, provide ability to exquisitely detect textures - ex.cloth, wood, BRAILLE!
- Elevations as little as 5 micrometers can be detected. What kind of nerve ending are the Ruffini Endings? Where are they found, what do theydo, fast/slow adapting, and what is their structure? - ANSWER Encapsulated nerve
ending Found in both hairy and glabrous skin. Respond to drag (shearing stress) Slowly adapting Structure is similar to that of Golgi tendon organs - a collagenous core in which severalaxons liberally branch.
What kind of nerve ending are the pacinian corpuscles? Where are they found, what istheir structure, slow/fast adapting, and what are they especially responsive to? - ANSWER Encapsulated Nerve Endings Subcutaneous- About 300 found in hand, along side fingers and palm A thin connective tissue sheath Onion-like layers of perineural epithelium with capillaries Innermost: a central, unmyelinated axon surrounded by several teloglial lamellae Rapidly adapting ("event detectors") Especially responsive to vibration (bone) Explain the basic autonomic pathway of two neurons that synapse in an autonomicganglion - ANSWER
Facial (CN 7) Glossopharyngeal (CN 9) Vagus (CN 10) Sacral: sacral segments of spinal cord Ocularmotor nerve (CN III) has what post ganglionic cell? What does that cell innervate?- ANSWER CILIARY GANGLION
Post-ganglionic fibers innervate Pupil sphincter (constriction)Ciliary muscle of uveal tract (accommodation of crystalline lens)
Facial Nerve (CN VII) has what post ganglionic cell? What does that cell innervate? -ANSWER PTERYGOPALATINE GANGLION and SUBMANDIBULAR GANGLION.
Post-ganglionic fibers innervatePterygopalatine → lacrimal and nasal glands Submandibular → submandibular and sublingual glands Glossopharyngeal Nerve (CN IX) has what post ganglionic cell? What does that cellinnervate? - ANSWER OTIC GANGLION
Post-ganglionic fibers innervate parotid gland Vagus Nerve (CN X) has what post ganglionic cell? What does that cell innervate? -ANSWER mural or intramural ganglia of heart, lungs, lower esophagus, stomach, pancreas, gall bladder, small intestine, and parts of colon
Where do sacral parasympathetic fibers descend from and to? -matter of segments S2, S3 and S4, they descend in the cauda equina ANSWER Lateral gray
Where do sacral parasympathetic preganglionic fibers synapse on? -ganglion cells in wall of distal colon and rectum ANSWER On
on pelvic parasympathetic ganglia What do postganglionic parasympathetic fibers innervate? -(bladder) and tunica media of internal pudendal artery (middle layer of artery that leads ANSWER detrusor muscle to external genitalia) What kind of presynaptic neurons are used in PNS/SNS? What kind of ganglionicreceptor?What kind of effector organ receptor? - ANSWER PNS/SNS- both have cholinergic neurons (releases ACh) Both have nicotinic receptors on their ganglion cell, but SNS releases norepinephrine asa result while the PNS releases more ACh
As a result SNS has an adrenergic receptor on its effector organ while PNS hasmuscarinic receptor
What are the 4 sympathetic junctional receptors? Are they pre or post-junctional? Whateffects do they have? - ANSWER Post-junctional α 1
Peripheral small arteries and large arterioles Iris dilator muscleSphincters of alimentary tract and bladder neck Vas deferens Pre-junctional α 2
