Lab Exam 4 Nerves Flashcards

Question

Microglia

Answer 1

small macrophages that develop from white blood cells called monocytes

Answer 2

(starlike) are the most abundant and constitute over 90% of the tissue in some areas of the brain. Functions: • form a supportive framework , the blood–brain barrier • Scar tissue and fill space formerly occupied by damaged neurons (astrocytosis or sclerosis)

Answer 3

Schwann cells, or neurilemmocytes Satellite cells

Answer 4

envelop nerve fibers of the PNS • Produce a myelin sheath similar to the one produced by oligodendrocytes in the CNS • Assist in the regeneration of damaged fibers

Answer 5

surround the neurosomas in ganglia of the PNS • provide electrical insulation around the soma • Regulate the chemical environment of the neurons

Answer 6

insulating layer around a nerve fiber • It is formed by oligodendrocytes in the CNS and Schwann cells in the PNS • Its composition is like that of plasma membranes in general (20% protein and 80% lipid)

Answer 7

Production of the myelin sheath (it is completed until late adolescence)

Answer 8

DIAMETER of the fiber Signal conduction occurs along the surface of a fiber, not deep within its axoplasm Large fibers have more surface area and conduct signals more rapidly than small fibers PRESENCE or absence of myelin Myelin speeds up signal conduction

Answer 9

83% of the brain’s volume • Consists of a pair of cerebral hemispheres • Thick folds called gyri (singular, gyrus) separated by shallow grooves called sulci (singular, sulcus) • A deep median groove, the longitudinal fissure, separates the right and left hemispheres from each other • At the bottom of this fissure, the hemispheres are connected by a thick bundle of nerve fibers called the corpus callosum

Answer 10

Frontal lobe Parietal lobe Occipital lobe Temporal lobe The insula

Answer 11

voluntary motor functions motivation planning mood emotion social judgment aggression

Answer 12

primary site for receiving and interpreting signals of the general senses

Answer 13

principal visual center of the brain

Answer 14

hearing smell learning some aspects of vision and emotion

Answer 15

small mass of cortex deep to the lateral sulcus, made visible only by retracting or cutting away some of the overlying cerebrum

Answer 16

Occupies the posterior cranial fossa inferior to the cerebrum, separated from it by the transverse cerebral fissure It consists of right and left cerebellar hemispheres connected by a narrow bridge called the vermis Each hemisphere exhibits folds called folia separated by shallow sulci Its most distinctive neurons→Purkinje cells

Answer 17

1. Inferior peduncles connected to the medulla oblongata (spinal input) 2. Middle peduncles to the pons (cerebral input) 3. Superior peduncles to the midbrain (cerebellar output) The white matter exhibits a branching pattern called the arbor vitae

Answer 18

center for monitoring muscle contractions and aiding in motor coordination

Answer 19

The brain, like the spinal cord, is composed of gray and white matter

Answer 20

the seat of the neurosomas, dendrites, and synapses • forms a surface layer called the cortex over the cerebrum and cerebellum, and deeper masses called nuclei surrounded by white matter

Answer 21

lies deep to the cortical gray matter in most of the brain, is composed of bundles of axons, which here connect one part of the brain to another and to the spinal cord

Answer 22

1. Dura mater 2. Arachnoid mater 3. Pia mater They protect the brain and provide a structural framework for its arteries and veins

Answer 23

—an outer periosteal layer equivalent to the periosteum of the cranial bones, and an inner meningeal layer

Answer 24

spaces that collect blood that has circulated through the brain

Answer 25

under the cranium along the median line

Answer 26

which runs horizontally from the rear of the head toward each ear and empty into the internal jugular veins of the neck

Answer 27

The arachnoid mater is a transparent membrane over the brain surface • A subarachnoid space separates it from the pia below, and in some places, a subdural space separates it from the dura above The pia mater is a very thin, that closely follows all the contours of the brain, even dipping into the sulci • It is not usually visible without a microscope

Answer 28

Inflammation of the meninges Is one of the most serious diseases of infancy and childhood It occurs especially between 3 months and 2 years of age Causes: a variety of bacteria and viruses that invade the CNS by way of the nose and throat, often following respiratory, throat, or ear infections Signs and symptoms include: high fever, stiff neck, drowsiness, intense headache, and vomiting Diagnosed by: spinal tap (lumbar puncture) - examination of the cerebrospinal fluid (CSF) for bacteria and white blood cells

Answer 29

On the floor or wall of each ventricle is a mass of blood capillaries called a choroid plexus • Ependyma, a type of neuroglia that resembles a cuboidal epithelium, lines the ventricles and canals and covers the choroid plexuses→ produces cerebrospinal fluid clear, colorless liquid that fills the ventricles and canals of the CNS and bathes its external surface CSF production begins with the filtration of blood plasma through the capillaries of the brain

Answer 30

• The largest are the lateral ventricles, which form an arc in each cerebral hemisphere • Through a interventricular foramen, each lateral ventricle is connected to the third ventricle, (inferior to the corpus callosum) • The cerebral aqueduct passes down the core of the midbrain and leads to the fourth ventricle, between the pons and cerebellum • Caudally, this space narrows and forms a central canal that extends through the medulla oblongata into the spinal cord

Answer 31

• Because neurons have such a high demand for ATP, and therefore glucose and oxygen, the constancy of blood supply is especially critical to the nervous system • A 10-second interruption in blood flow can cause loss of consciousness • an interruption of 1 to 2 minutes can significantly impair neural function • 4 minutes without blood causes irreversible brain damage • Damaged brain tissue is essentially irreplaceable, and the brain therefore must be well protected

Answer 32

• The brain is well protected by the blood–brain barrier (BBB), which consists of tight junctions between the endothelial cells that form the capillary walls • The brain barrier system (BBS) is highly permeable to water, glucose, and lipid-soluble substances such as oxygen, carbon dioxide, alcohol, caffeine, nicotine, and anesthetics

Answer 33

what remains of the brain if the cerebrum and cerebellum are removed Its major components, from rostral to caudal, are: • Midbrain • Pons • Medulla oblongata Caudally, the brainstem ends at the foramen magnum of the skull, and the CNS continues below this as the spinal cord

Answer 34

begins at the foramen magnum of the skull and ends at a groove between the medulla and pons • All nerve fibers connecting the brain to the spinal cord pass through the medulla • Some of these are ascending (sensory) and some are descending (motor) fibers

Answer 35

measures about 2.5 cm long, appears as a broad anterior bulge rostral to the medulla • Posteriorly, two pair of cerebellar peduncles→connect the cerebellum to the pons and midbrain • Exhibits continuations of the reticular formation (sleep, respiration and posture) • Cranial nerves V to VIII begin or end in the pons

Answer 36

Is a loosely organized web of gray matter that runs vertically through all levels of the brainstem, it consists of more than 100 small neural networks The functions of these networks include : • Somatic motor control (muscle tension to maintain tone, balance, and posture) • Cardiovascular control • Pain modulation • Sleep and consciousness (Injury to the reticular formation can result in irreversible coma) • Habituation: the brain learns to ignore repetitive, inconsequential stimuli while remaining sensitive to others

Answer 37

• Each side of the brain has a thalamus (ovoid mass) • Nearly all input to the cerebrum passes by way of synapses in the thalamic nuclei • taste, smell, hearing, equilibrium, vision, touch, pain, pressure, heat, and cold • Plays a key role in motor control • signals from the cerebellum to the cerebrum • Is involved in the memory and emotional functions of the limbic system (temporal and frontal lobes)

Answer 38

• Forms the floor and part of the walls of the 3rd ventricle • From the optic chiasm to the mammillary bodies • The pituitary gland is attached to the hypothalamus by a stalk (infundibulum) Is the major control center of the endocrine and autonomic nervous systems→homeostatic regulation • Hormone secretion • Autonomic effects • Thermoregulation • Food and water intake • Sleep and circadian rhythms • Memory • Emotional behavior and sexual response

Answer 39

very small mass of tissue composed mainly of: • the pineal gland (circadian rhythms) • the habenula (a relay from the limbic system to the midbrain), and • a thin roof over the third ventricle

Answer 40

(circadian rhythms)

Answer 41

• cylinder of nervous tissue that arises from the brainstem at the foramen magnum of the skull • passes through the vertebral canal as far as the inferior margin of the first lumbar vertebra (L1) gives rise to 31 pairs of spinal nerves • The first pair passes between the skull and vertebra C1, and the rest pass through the intervertebral foramina • The cord exhibits longitudinal grooves on its anterior and posterior sides— the anterior median fissure and posterior median sulcus • The spinal cord is divided into cervical, thoracic, lumbar, and sacral regions

Answer 42

• Cervical enlargement gives rise to nerves of the upper limbs • Lumbar enlargement that issues nerves to the pelvic region and lower limbs

Answer 43

bundle of nerve roots that occupy the vertebral canal from L2 to S5

Answer 44

innervates the pelvic organs and lower limbs.

Answer 45

enclosed in three fibrous connective tissue membranes called meninges • These membranes separate the soft tissue of the central nervous system from the bones of the vertebrae and skull

Answer 46

Dura mater Arachnoid mater Pia mater

Answer 47

tough collagenous membrane, forms the dural sheath The space between the sheath and vertebral bones, called the epidural space, is occupied by blood vessels, adipose tissue, and loose connective t issue

Answer 48

simple squamous epithelium (arachnoid membrane) • the gap between the arachnoid membrane and the pia mater→subarachnoid space, is filled with cerebrospinal fluid

Answer 49

transparent membrane that closely follows the contours of the spinal cord • beyond the medullary cone→terminal filum, within the lumbar cistern • At S2, fuses with the dura mater to form a coccygeal ligament

Answer 50

Gray matter: contains little myelin • It contains the somas, dendrites, and proximal parts of the axons of neurons • It is the site of synaptic contact between neurons (neural integration) White matter: abundant of myelin • It is composed of bundles of axons, called tracts, that carry signals from one part of the CNS to another Both gray and white matter also have an abundance of glial cells

Answer 51

• The core consists mainly of two posterior (dorsal) horns, posterolateral surfaces of the cord, and two thicker anterior (ventral) horns, anterolateral surfaces • The right and left sides are connected by a gray commissure • In the middle of the commissure is the central canal, lined with ependymal cells, and filled with CSF • Spinal nerve branches into a posterior (dorsal) root and anterior ( ventral) root • The posterior root carries sensory nerve fibers • The anterior horns contain the large somas of the somatic motor neurons

Answer 52

• It consists of bundles of axons that course up and down the cord and provide avenues of communication between different levels of the CNS. • These bundles are arranged in three pairs called columns or funiculi: • a posterior (dorsal) column • Lateral column • anterior (ventral) column Each column consists of subdivisions called tracts or fasciculi

Answer 53

Pyramidal tracts - Lateral corticospinal tract - Anterior corticospinal tract Extrapyramidal Tracts - Rubrospinal tract - Reticulospinal tracts -Olivospinal tract - Vestibulospinal tract

Answer 54

Dorsal Column Medial Lemniscus System Gracile fasciculus Cuneate fasciculus Spinocerebellar Tracts • Posterior spinocerebellar tract •Anterior spinocerebellar tract Anterolateral System Lateral spinothalamic tract Anterior spinothalamic tract Spino-olivary fibers

Answer 55

• Ascending tracts carry sensory information up the cord Descending tracts conduct motor impulses down Several of these tracts undergo decussation as they pass up or down the brainstem and spinal cord—meaning that they cross over from the left side of the body to the right, or vice versa • the left side of the brain receives sensory information from the right side of the body • the right side of the brain senses and controls the left side of the body Contrallateral→when the origin and destination of a tract are on opposite sides of the body Ipsilateral → when a tract does not decussate, its origin and destination are on the same side of the body

Answer 56

A nerve is a cordlike organ composed of numerous nerve fibers (axons) bound together by connective tissue • Each nerve fiber is surrounded by a basal lamina and then a thin sleeve of loose connective tissue called the endoneurium • The fibers are gathered in bundles called fascicles, each wrapped in a sheath called the perineurium • Several fascicles are then bundled together and wrapped in an outer epineurium to compose the nerve as a whole

Answer 57

• Sensory (afferent) fibers carrying signals from sensory receptors to the CNS • Motor (efferent) fibers carrying signals from the CNS to muscles and glands *Most nerves, however, are mixed nerves, which consist of both afferent and efferent fibers and therefore conduct signals in two directions A nerve resembles a thread, a ganglion resembles a knot in the thread • A ganglion is a cluster of neurosomas outside the CNS The nerve then exits the vertebral canal through the intervertebral foramen

Answer 58

8 cervical (C1–C8) 12 thoracic (T1–T12) 5 lumbar (L1–L5) 5 sacral (S1–S5) 1 coccygeal (Co)

Answer 59

• Each spinal nerve except C1 receives sensory input from a specific area of skin called a dermatome • A dermatome map is a diagram of the cutaneous regions innervated by each spinal nerve (dermatomes overlap at their edges)

Answer 60

• The virus remains for life in the posterior root ganglia • If the immune system is compromised, the virus can travel along the sensory nerve fibers by fast axonal transport and cause shingles (herpes zoster)— characterized by a painful trail of skin discoloration and fluid-filled vesicles along the path of the nerve Postherpetic neuralgia, PHN→chronic intense pain in the site of the lesions lasting for months or even years Vaccine: varicella vaccine in children, Zostavax in adults >60 years old Treatment: • aspirin and steroidal ointments→pain relief • acyclovir (antiviral drug) can shorten the course of an episode of shingles, but only if taken within the first 2 to 3 days of outbreak *Aspirin is for adults, kids are not supposed to take aspirin! Can cause Reye Syndrome

Answer 61

• Cervical plexus in the neck • Brachial plexus near the shoulder • Lumbar plexus of the lower back • Sacral plexus • Coccygeal plexus Nerve plexus→trunks→anterior and posterior divisions→cords Somatosensory signals are for touch, heat, cold, stretch, pressure, pain, and other sensations • Proprioception (body position and movements) to maintain equilibrium (balance) and coordination The motor function of these nerves is primarily to stimulate the contraction of skeletal muscles

Answer 62

• Lesser occipital nerve • Greater auricular nerve • Transverse cervical nerve • Ansa cervicalis • Supraclavicular nerve • Phrenic nerve→innervate the diaphragm, and play an essential role in breathing

Answer 63

Is formed predominantly by the anterior rami of nerves C5 to T1 It passes over the first rib into the axilla and innervates the upper limb and some muscles of the neck and shoulder The subdivisions of this plexus are called roots, trunks, divisions, and cords • Musculocutaneous nerve • Axillary nerve • Radial nerve • Median nerve • Ulnar nerve

Answer 64

Is formed from the anterior rami of nerves L1 to L4 and some fibers from T12 It gives rise to the following nerves • Iliohypogastric nerve • Ilioinguinal nerve • Genitofemoral nerve • Lateral femoral cutaneous nerve • Femoral nerve • Obturator nerve

Answer 65

formed from the anterior rami of nerves L4, L5, and S1 through S4 • it is connected to the lumbar plexus by fibers that run through the lumbosacral trunk, the two plexuses are sometimes referred to collectively as the lumbosacral plexus • The tibial and common fibular nerves travel together through a connective tissue sheath; they are referred to collectively as the sciatic nerve • At the popliteal fossa, the tibial and common fibular nerves diverge • Tibial nerve descends through the leg→medial and plantar nerves in the foot • Common fibular nerve divides into deep and superficial fibular nerves The coccygeal plexus is formed from the anterior rami of S4, S5

Answer 66

Reflexes are quick, involuntary, stereotyped reactions of glands or muscles to stimulation Properties of a reflex: 1. Reflexes require stimulation→they are a response to stimuli 2. Reflexes are quick→involve few interneurons, or none, and minimum synaptic delay 3. Reflexes are involuntary→they occur without intent, often without our awareness, and they are difficult to suppress 4. Reflexes are stereotyped→they occur in essentially the same way every time; the response is very predictable

Answer 67

Inborn (intrinsic) reflex→rapid, predictable motor response to a stimulus • Unlearned, unpremeditated, and involuntary • Built into our neural anatomy→regulated by the brain steam and spinal cord • Learned (acquired) reflex→results from practice or repetition • Example: driving a car *The distinction between inborn and learned reflexes is not clear-cut and most inborn reflex actions can be modified by learning and conscious effort

Answer 68

• Somatic Reflexes→if they activate skeletal muscle • Autonomic Reflexes→if they activate visceral effectors (smooth or cardiac muscle, glands)

Answer 69

• Tests of somatic reflexes are important clinically to assess the condition of the nervous system • The most commonly assessed reflexes are: • Stretch reflex • Flexor reflex • Superficial reflexes • Spinal Shock→occurs when the spinal cord is transected, immediately depressing all functions controlled by the cord.

Answer 70

Muscle spindles are stretch receptors embedded in the muscles (proprioceptors) They inform the brain of muscle length and body movements→the brain sends motor commands back to the muscles that control muscle tone, posture, coordinated movement, and corrective reflexes

Answer 71

When a muscle is suddenly stretched →it contracts, increases tone, and feels stiffer than an unstretched muscle →helps to maintain equilibrium and posture

Answer 72

Tendon organs are proprioceptors located in a tendon near its junction with a muscle • The tendon reflex is a response to excessive tension on the tendon • This serves to moderate muscle contraction before it tears a tendon Tendon reflex→the reflexive contraction of a muscle when its tendon is tapped, as in the familiar patellar reflex *Tendon organs measure tension

Answer 73

quick contraction of flexor muscles resulting in the withdrawal of a limb from an injurious stimulus

Answer 74

The crossed extension reflex is the contraction of extensor muscles in the limb opposite from the one that is withdrawn • It extends that limb and enables you to keep your balance

Answer 75

Plantar Reflex→tests integrity of spinal cord from L4 – S2 and corticospinal tracts • Draw a blunt object downward along the lateral aspect of the plantar surface of the foot • Normal→toes flex • Abnormal→toes dorsiflexion of great toe and the smaller toes fan laterally (Babinski’s sign)

Answer 76

Abdominal Reflex→check the integrity of the spinal cord and ventral rami from T8 – T12 and corticospinal tracts • Stroking the skin of the lateral abdomen above the umbilicus, the reflex induces a movement of the umbilicus toward the stimulated site

Answer 77

• Brain must communicate with rest of body • Cranial nerves are part of Peripheral Nervous System (PNS) • 12 pairs • Most of them arise from the base of the brain • Numbered with Roman numerals according to their position • Name of nerve often related to its function • Lead to muscles and sense organs located mainly in the head and neck

Answer 78

Olfactory Optic Oculomotor Throchlear Trigeminal Abducens Facial Vestibulocochlear Glassopharayngeal Vagus Accessory Hypoglossal

Answer 79

The Olfactory • Sense of smell • Damage causes impaired sense of smell • Begins in the nasal cavity • Contains sensory fibers

Answer 80

The Optic Nerve • Begins at the retina of the eyes • Provides vision • Damage causes blindness in part or all of visual field

Answer 81

Oculomotor Nerve (III) Trochlear Nerve (IV) Abducens Nerve (VI) They innervate the 6 extrinsic muscles that perform voluntary eye movements

Answer 82

• Ophthalmic • Maxillary • Mandibular It is mainly Sensory! Sensation of the face

Answer 83

Facial Nerve (VII) • Sensory component→ sensation from the anterior 2/3 of the tongue • Motor component→muscles of facial expression, secretion from lacrimal and salivary glands

Answer 84

Vestibulocochlear • Vestibular branch: detect movements that are linear and angular (turning) • Cochlear branch: responsible for hearing sounds

Answer 85

Glossopharyngeal (IX) • Sensory→neurons for taste to posterior 1/3 of tongue, sensory neurons of pharynx and eardrum • Motor→stylopharyngeus muscle (swallowing) and parotid salivary glands

Answer 86

Vagus Nerve (X) • Sensory→pharynx, external acoustic meatus, diaphragm, and internal organs of the thoracic and abdominopelvic cavities • Motor→motor fibers to the palate, pharynx, and autonomic motor fibers to internal organs This nerve is almost everywhere!!

Answer 87

Accessory Nerve (XI) Entirely Motor and innervates the Trapezius and Sternocleidomastoid muscles *It actually origins from spinal cord!

Answer 88

Hypoglossal Nerve (XII) Entirely Motor and innervates the muscles that move the tongue

Answer 89

The lacrimal apparatus works to produce tears that are needed to wet the front of the eye and flush debris from the ocular surface

Answer 90

• Congenital weakness of the external eye muscles • The affected eye rotates laterally or medially • Eyes alternate in focusing objects • The brain shuts off the deviant eye→ functional blindness Which muscle is affected in this patient?

Answer 91

1. Retina: • Photoreceptors 2. Choroid: • Vascular • Brown (melanocytes) 3. Sclera: • White • fibrous connective tissue • Avascular

Answer 92

Conjunctiva —a transparent mucous membrane that lines eyelids and covers anterior surface of eyeball, except cornea Sclera: dense, collagenous white of the eye

Answer 93

Cornea: Transparent cover on anterior surface of eyeball Pupil: central opening Iris: colored diaphragm controlling size of pupil

Answer 94

Optical components Lens: suspended by suspensory ligaments from ciliary body • Changes shape to help focus light • Rounded with no tension or flattened with pull of suspensory ligaments

Answer 95

Cataract —clouding of lens • Lens fibers darken with age, fluid-filled bubbles and clefts filled with debris appear between the fibers • Induced by diabetes, smoking, drugs, ultraviolet radiation, and certain viruses • Replace natural lens with plastic one

Answer 96

Glaucoma —elevated pressure within the eye due to obstruction of scleral venous sinus and improper drainage of aqueous humor • Death of retinal cells due to compression of blood vessels and lack of oxygen • Illusory flashes of light are an early symptom • Colored halos around lights are late symptom • Lost vision cannot be restored

Answer 97

Retina • Attached to the rest of the eye only at optic disc and at ora serrata Detached retina causes blurry areas in field of vision and leads to blindness

Answer 98

• Outer layer→pigmented cells • Inner layer (neural): • Photoreceptors • Rods→dim light (night vision) • Cones→color (day vision) • Bipolar cells • Ganglion cells

Answer 99

• Congenital lack of one or more cone pigments • X-linked condition, more common in males • 8-10% of males have some form of colorblindness • Most common type is red-green color blindness

Answer 100

• The axons of the ganglion cells of the retina converge at the posterior aspect of the eyeball and exit as the optic nerve • At the optic chiasm, the fibers crossover • The optic tracts formed contain fibers from the lateral side of the eye on the same side and from the medial side of the opposite eye

Answer 101

• Divisions: • External ear (hearing) • Middle ear (hearing) • Internal ear (hearing and equilibrium)

Answer 102

Tympanic Membrane (eardrum) • Auricle (pinna) • Elastic cartilage • Rim • Lobule External acoustic meatus (Auditory canal) Ceruminous glands secrete cerumen (ear wax)

Answer 103

Malleus Incus Tympanic Membrane Oval Window Round Window Pharyngotympanic Tube

Answer 104

• Common result of a sore throat • Most common cause of hearing loss in children • Eardrum bulges and becomes inflamed and red • Treatment→Antibiotics

Answer 105

Lies in the Temporal Bone, behind the eye socket • Bony Labyrinth→ channels in the bone, contains perilymph • Membranous Labyrinth→sacs and ducts contained within the bony labyrinth, contain endolymph

Answer 106

• Saccule and Utricule (membranous sacs) • House of equilibrium receptor region called maculae→respond to the pull of gravity and report changes of head position

Answer 107

• Anterior • Posterior • Lateral • They communicate with the Utricle • Each duct has an ampulla that houses an equilibrium receptor region called crista ampullaris

Answer 108

• Cochlea (“snail”) houses the cochlear ducts which have the receptor organ of hearing→ Organ of Corti • The cochlea is divided into chambers: • Scala vestibuli • Scala media • Scala tympani

Answer 109

• Chemoreceptors→respond to chemical in an aqueous solution Smell receptors are excited by airborne chemicals that dissolve in fluids coating nasal membranes

Answer 110

• Dissolved chemicals are detected by receptor cells in taste buds (sensory organs for taste) • Gustatory epithelial cells are the receptor cells for taste (taste cells)