Divisions of the Nervous System

Primary gustatory cortex

located within insula involved in processing taste information

Primary visual cortex

located within occipital lobe, receives and processes incoming visual information

Primary olfactory cortex

located within temporal lobe provides conscious awareness of smells

Primary auditory cortex

located within temporal lobe, receives and processes auditory information

long-term potentiation

mechanism very rapid repeated stimulation of the same neurons increases the number of postsynaptic neurotransmitter receptors and causes physical changes at the synapse that make synaptic transmission more effective new synaptic connections and repeated stimulation of the same neurons—fulfill two requirements of long-term memory. First, sufficient synapses form to encode an almost limitless number of memories. Each of the 10 billion neurons in the cortex can make tens of thousands of synaptic connections to other neurons, forming 60 trillion links. Second, a certain pattern of synapses can persist for years.

Representational hemisphere

other hemisphere: involved in visuospatial relationships seat of imagination, artistic skill, pattern perception, right hemisphere in most people

dura mater

outermost layer composed of tough, white, dense connective tissue and contains many blood vessels and nerves attaches to the inside of the cranial cavity and forms the internal periosteum of the surrounding skull bones some regions, the dura mater extends inward between lobes of the brain and forms supportive and protective partitions other areas, the dura mater splits into two layers, forming channels called dural sinuses continues into the vertebral canal as a strong, tubular sheath that surrounds the spinal cord attached to the cord at regular intervals by a band of pia mater (denticulate ligaments) that extends the length of the spinal cord on either side terminates as a blind sac at the level of the second sacral vertebra not attached directly to the vertebrae but is separated by an epidural space Tough, dense irregular connective tissue, two layers: Meningeal layer, immediately superficial to arachnoid Periosteal layer, more superficial layer the periosteum on internal surface of cranial bones Layers usually fused, but separate in specific areas - form large, blood-filled spaces, dural venous sinuses typically triangular in cross section - drain blood from the brain

terminal ganglia

there, the preganglionic fibers lead outward on cranial or sacral nerves to ganglia near or in various organs

extrapyramidal tracts

they include the reticulospinal and rubrospinal tracts

pia mater

thin and contains many nerves, as well as blood vessels that nourish the underlying cells of the brain and spinal cord. The pia mater is attached to the surfaces of these organs and follows their irregular contours, passing over the high areas and dipping into the depressions. Innermost of cranial meninges Thin layer of areolar connective tissue, tightly adheres to brain (follows contours of brain surface)

Claustrum

thin sliver of gray matter immediately internal to insula cortex processes visual information on a subconscious level

Fornix

thin tract of white matter, connects hippocampus with other limbic structures

arachnoid mater

thin, weblike membrane that does not have blood vessels and is located between the dura and pia maters over brain and spinal cord does not dip into the grooves and depressions on their surfaces. thin strands extend from its undersurface and attach to the pia mater Partially composed of collagen and elastic fibers termed arachnoid trabeculae support cerebral arteries and veins Trabeculae extending deep to reach pia mater, through the subarachnoid space contains cerebrospinal fluid

lower motor neurons

various levels of the spinal cord whose cell bodies are in the anterior horn and whose axons lead to skeletal muscles.

cervical plexuses

ventral branches of the first four cervical nerves lie deep in the neck on either side. Fibers from these plexuses supply the muscles and skin of the neck

brachial plexuses

ventral branches of the lower four cervical nerves and the first thoracic nerve give rise

lumbosacral plexuses

ventral branches of the lumbar and first four sacral nerves networks of nerve fibers extend from the lumbar and sacral regions of the back into the pelvic cavity, giving rise to a number of motor and sensory fibers associated with the lower abdominal wall, external genitalia, buttocks, thighs, legs, and feet. The major branches of these plexuses include the following

Cerebrum characteristics

Usually difficult to assign precise function to specific region overlapping and indistinct boundaries, and some aspects not easily assigned to any single region e.g., memory Innervation hemispheres receiving information from opposite side of body hemispheres projecting motor commands to opposite side of body Functional differences between hemispheres termed cerebral lateralization, e.g., regions of brain responsible for speech in left cerebral hemisphere primarily affects higher-order function

cerebral peduncles

Two prominent bundles of nerve fibers on the underside of the midbrain comprise fibers include descending tracts and are the main motor pathways between the cerebrum and lower parts of the nervous system large bundles of sensory fibers that carry impulses upward to the thalamus. motor tracts on anterolateral surface of midbrain composed of descending axon bundles of pyramidal system carry voluntary motor commands from primary motor cortex

Spinal cord subdivisions

Vertebrae Conus medullaris Cauda equina

cerebral cortex

A thin layer of gray matter constitutes the outermost portion of the cerebrum covers the gyri, dipping into the sulci and fissures. The cerebral cortex contains nearly 75% of all the neuron cell bodies in the nervous system beneath the cerebral cortex is a mass of white matter that makes up the bulk of the cerebrum mass contains bundles of myelinated axons that connect neuron cell bodies of the cortex with other parts of the nervous system

muscarinic receptors and nicotinic receptors.

Acetylcholine can combine with two types of cholinergic receptors muscarine, a toxin from a fungus that can activate muscarinic receptors, and nicotine, a toxin in tobacco that can activate nicotinic receptors

Nerve plexus organization

Axons from anterior ramus extend to body structures through different branches Terminal branch of plexus houses axons from several spinal nerves Most named nerves composed of axons from multiple spinal nerves Damage to single spinal nerve usually does not result in total loss

arachnoid granulations

CSF is continuously reabsorbed into the blood through tiny, fingerlike structures project from the subarachnoid space into the blood-filled dural sinuses

ventricles

CSF is formed in four interconnected cavities lie in the cerebral hemispheres and brainstem filled with CSF and are continuous with the central canal of the spinal cord, which extends the full length of the cord Cavities within the brain lined with ependymal cells containing cerebrospinal fluid Connected with each other and with spinal cord's central canal Four ventricles

Components of cerebral nuclei

Caudate nucleus Amygdaloid body (amygdala) Lentiform nucleus Claustrum Corpus striatum

Limbic system components

Cingulate gyrus Parahippocampal gyrus Hippocampus Amygdaloid body Fornix Olfactory bulbs, olfactory tracts, olfactory cortex process odors that can provoke emotions

Cerebrum composition

Composed of two halves, left and right cerebral hemispheres Separated by deep cleft, longitudinal fissure Hemispheres separate, except at a few locations bundles of axons, tracts, form white matter connecting regions Largest tract, corpus callosum, provides main method of communication between hemispheres

Association Areas

Connected to adjacent motor and sensory regions Process and interpret data or coordinate motor response Integrate new sensory inputs with memories

Central white matter

Deep to gray matter of cerebral cortex Composed primarily of myelinated axons Grouped into bundles, tracts - three general types: Association tracts - connect different regions of cerebral cortex within same hemisphere Arcuate fibers - short tracts, connect gyri in the same lobe Longitudinal fasciculi - longer tracts, connect gyri in different lobes Commissural tracts Prominent tracts linking right and left hemispheres largest = corpus callosum smaller = anterior and posterior commissure Projection tracts Link cerebral cortex to inferior brain regions and spinal cord Hemispheres are in constant contact through commissures, especially corpus callosum

dermatome

Each spinal nerve below C1 contains sensory fibers that reach the skin, and the region innervated Specific segment of skin supplied by single spinal nerve All spinal nerves except C1 Skin divided into segments into a dermatome map E.g., horizontal skin around umbilicus supplied by anterior ramus of T10 Can indicate potential damage to one or more spinal nerves e.g., loss of sensation on medial arm and forearm indicates C8 may be damaged Involved in referred visceral pain pain from one organ referred to a dermatome e.g., appendix innervated by axons from T10 appendicitis with referred visceral pain to T10 region

Protection of spinal cord

Encapsulated by spinal cord meninges continuous with cranial meninges Structures and spaces encircling the spinal cord (outer to inner) vertebra, epidural space, dura mater, subdural space, arachnoid mater, subarachnoid space, pia mater Epidural space Dura mater Arachnoid mater and Subarachnoid space deep arachnoid mater space filled with cerebrospinal fluid Pia mater Denticulate ligaments

White Matter

External to gray matter, composed of myelinated axons going to and from the brain

Hemisphere specialization = cerebral lateralization

Higher order centers with different but complementary functions Develops prior to 5-6 years of age, and differs between sexes and handedness

Gray matter

Inner gray matter region Dendrites and cell bodies of neurons, glial cells, unmyelinated axons Shape resembles a letter H Anterior horns Lateral horns Posterior horns

Lumbar plexuses

Located along psoas major muscle Subdivided into anterior division and posterior division Femoral nerve main nerve in posterior division, supplies anterior thigh muscles and sartorius Obturator nerve main nerve in anterior division Smaller nerves of lumbar plexus innervate: abdominal wall portions of external genitalia inferior abdominal muscles

red nucleus

Near the center of the midbrain is a mass of gray matter nucleus communicates with the cerebellum and with centers of the spinal cord, and it plays a role in reflexes that maintain posture. It appears red because it is richly supplied with blood vessels

Nerve plexus

Network of interweaving anterior rami of spinal nerves Anterior rami of most spinal nerves form plexuses on both right and left sides Four main plexuses: cervical, brachial, lumbar, sacral

Cerebral nuclei

Paired masses of gray matter buried within white matter in basal cerebral hemispheres Help regulate motor output Diseases of nuclei often associated with involuntary movements

CSF Circulation

Produced by choroid plexus, then circulates through ventricles from lateral ventricles to third ventricle through aqueduct into fourth ventricle Then enters subarachnoid space (including surrounding the spinal cord) and passes into central canal of spinal cord Excess CSF removed from subarachnoid space flows into arachnoid villi, fingerlike extensions of arachnoid mater that project through dura into dural venous sinuses collection termed an arachnoid granulation conduit for one-way flow of excess CSF into blood

The spinal cord

Provides a vital link between brain and rest of body Exhibits some functional independence from the brain Extends inferiorly from brain through vertebral canal Ends at the level of L1 vertebra Has rootlets coming off will form spinal nerves some forming interweaving nerves, nerve plexuses

Spinal cord features

Roughly cylindrical, flattened posteriorly and anteriorly Posterior median sulcus longitudinal narrow groove on posterior surface Anterior median fissure longitudinal depression on anterior surface

cerebrum and basal nuclei development

The wall of the anterior portion of the forebrain gives rise

interventricular foramina

Third ventricle communicates with the lateral ventricles through openings in its anterior end

cranial nerves detail

Twelve pair located on the underside of the brain mixed nerves first pair, which is sensory, has fibers that begin in the nasal cavity and synapse in the frontal lobe of the cerebrum. The second pair, also sensory, originates in the eyes, and their fibers synapse in the thalamus

corpora quadrigemina

Two pairs of rounded knobs on the superior surface of the midbrain mark the location of four nuclei upper masses (superior colliculi) contain the centers for certain visual reflexes, such as those responsible for moving the eyes to view something as the head turns. The lower ones (inferior colliculi) contain the auditory reflex centers that operate when it is necessary to move the head to hear sounds more distinctly

dural sinuses

Venous blood flows through these channels as it returns from the brain to vessels leading to the heart.

sensory speech area

Wernicke's area temporal lobe adjacent to the parietal lobe, near the posterior end of the lateral sulcus, usually in the left hemisphere. This area is important for understanding and formulating written and spoken language. typically located only in left hemisphere, involved in recognizing, understanding, and comprehending spoken and written language works with motor speech area for fluent communication

Spinal Arachnoid mater and Subarachnoid space

deep arachnoid mater space filled with cerebrospinal fluid

collateral ganglia

ganglia are some distance from the viscera they help control, other sympathetic ganglia are nearer to the viscera enter paravertebral ganglia synapse with neurons in these ganglia

epineurium

group of bundled fascicles, surrounded by an outermost layer of dense connective tissue give rise to a network of capillaries in the endoneurium that provides oxygen and nutrients to the neurons

withdrawal reflex

happens when a person touches something painful (and potentially damaging), as in stepping on a tack. Activated skin receptors send impulses to the spinal cord along the axons of sensory neurons. There the sensory neurons synapse with interneurons, which in turn synapse with motor neurons. The motor neurons activate fibers in the flexor muscles of the leg and thigh, which contract in response, pulling the foot away from the painful stimulus.

cerebellum, pons, and medulla oblongata development

hindbrain gives rise

falx cerebr

layer of dura mater separates left and right hemispheres

diencephalon development

posterior portion forms a section of the brain

ascending reticular activating system

refers to this functional aspect of the reticular formation. Without it the cerebral cortex cannot function consciously. Impulses judged to be important, such as those originating in pain receptors, are passed on to the cerebral cortex, while others are disregarded

transverse fissure

separates the cerebrum from the cerebellum

filum terminale

thin cord of connective tissue originating from the pia mater and dura mater descends to the upper surface of the coccyx

mammillary bodies

which are two rounded structures behind the infundibulum

cauda equina

adult spinal cord ends at the level between the first and second lumbar vertebrae, so the roots associated with the lumbar, sacral, and coccygeal nerves descend to their exits beyond the end of the cord, still within the vertebral canal. These descending roots form

General somatic efferent fibers

conduct motor impulses outward from the brain or spinal cord to skeletal muscles and stimulate them to contract

somatic nervous system

consists of the cranial and spinal nerve fibers that connect the CNS to the skin and skeletal muscles

Caudate nucleus

enlarged head and slender tail paralleling lateral ventricle helps produce pattern and rhythm of walking movements

Gray commissure

horizontal band of gray matter surrounding central canal contains primarily unmyelinated axons communication route between left and right gray matter

Cingulate gyrus

internal mass of cerebral cortex, seen only in sagittal section, surrounds diencephalon receives input from other components of limbic system

preganglionic fiber

leaves the CNS and synapses with one or more neurons whose cell bodies are within an autonomic ganglion

brain-stem

midbrain, pons, and medulla oblongata comprise attaches the brain to the spinal cord.

motor nerves

only fibers involved in motor control

optic nerves

sensory and lead from the eyes to the brain. They are associated with vision. The cell bodies of these neurons form ganglion cell layers in the eyes, and their axons pass through the optic foramina of the orbits and continue into the visual nerve pathways of the brain

longitudinal fissure

separates the right and left cerebral hemispheres

Ulnar nerves

supply muscles of the forearms and hands and the skin of the hands.

Denticulate ligaments

triangular extensions of spinal pia mater attach to dura mater help suspend and anchor spinal cord laterally

pineal gland

which forms as a cone-shaped projection from the roof of the diencephalon

lateral and anterior corticospinal tracts

( pyramidal tracts ) occupy the lateral and anterior funiculi fibers of the lateral tracts cross over in the lower medulla oblongata anterior tracts cross over at various levels of the spinal cord conduct motor impulses from the brain and synapse either directly or through interneurons with lower motor neurons, whose axons continue through spinal nerves to various skeletal muscles. Thus, they carry instructions that control voluntary movements medulla oblongata through which they pass

insula

(island of Reil) lobe deep within the lateral sulcus and is so named because it is covered by parts of the frontal, parietal, and temporal lobes. A circular sulcus separates the insula from the other lobes. small lobe deep to lateral sulcus can be observed by laterally pulling aside temporal lobe involved in: memory interpretation of taste

midbrain

(mesencephalon) short section of the brainstem between the diencephalon and the pons contains bundles of myelinated nerve fibers that join lower parts of the brainstem and spinal cord with higher parts of the brain. The midbrain includes several masses of gray matter that serve as reflex centers. It also contains the cerebral aqueduct that connects the third and fourth ventricles Cerebral peduncles Superior cerebellar peduncles Substantia nigra Tegmentum Tectum Nuclei of cranial nerves: oculomotor and trochlear

infundibulum

(pituitary stalk), which is a conical process behind the optic chiasma to which the pituitary gland is attached

General visceral afferent fibers

conduct sensory impulses to the CNS from blood vessels and internal organs.

Superior cerebellar peduncles

connect cerebellum to midbrain

superior peduncles

After integrating and analyzing the information from these two sources, the cerebellum sends correcting impulses from the dentate nucleus the thalamus and eventually to the motor cortex. These corrections are incorporated into motor impulses that travel downward through the pons, medulla oblongata, and spinal cord to lower motor neurons in the appropriate patterns to move the body in the desired way.

Distribution of spinal nerves

After intervertebral foramen, nerve split into branches called rami Posterior ramus Smaller, innervates deep muscles of back, skin of back Anterior ramus Larger, splits into multiple other branches innervate anterior and lateral trunk, upper limbs, lower limbs Rami communicantes additional rami associated with autonomic nervous system extend between spinal nerve and sympathetic trunk ganglion ganglia interconnected in sympathetic trunk parallel and lateral to vertebral column

Brain anatomy

Average weight of 1.35 to 1.4 kilograms Outer surface folded in on itself With spinal cord, composes central nervous system Associated with 12 pairs of cranial nerves Composed of four major regions: cerebrum divided into two halves, hemispheres further subdivided into five lobes diencephalon brainstem cerebellum Two tissue areas of brain and spinal cord: gray matter color from motor and interneuron cell bodies, dendrites, and unmyelinated axons white matter color from myelin on axons

Protection

Brain protected and isolated by multiple structures The cranium provides rigid support The meninges surround and partition the brain Cerebrospinal fluid cushions Blood-brain barrier prevents entry of harmful materials

motor speech area

Broca's area frontal lobe, usually in the left hemisphere, just anterior to the primary motor cortex and superior to the lateral sulcus important in generating the complex pattern of muscular actions of the mouth, tongue, and larynx, which make speech possible Bundles of axons directly and indirectly connect the motor speech area to the sensory speech area

Motor Areas

Control voluntary motor function Housed within frontal lobes Primary motor cortex located in precentral gyrus of the frontal lobe control voluntary skeletal muscle activity project contralaterally (opposite side) within brainstem or spinal cord

Cerebellar components

Convoluted surface covered by layer of cerebellar cortex Folds termed folia Left and right cerebellar hemispheres Each hemisphere with an anterior and posterior lobe separated by primary fissure Vermis narrow band of cortex, lies along midline between left and right lobes Partitioned into three regions: cerebellar cortex, outer gray matter of cortex internal region of white matter, arbor vitae deepest gray matter layer of cerebellar nuclei Three thick nerve tracts, peduncles, helps "fine-tune" skeletal muscle movements superior cerebellar peduncles connect cerebellum to midbrain middle cerebellar peduncles connect pons to cerebellum inferior cerebellar peduncles connect cerebellum to medulla oblongata

Cerebellar functions

Coordinates and "fine-tunes" skeletal muscle movements ensures skeletal muscles follow correct pattern stores memories of previously learned movements regulates activity along voluntary and involuntary motor paths adjusts movements initiated by cerebrum ensuring smooth movements Receives proprioceptive sensory information from muscles and joints helps maintain awareness of body's position and muscle tone uses information to regulate body's position maintains equilibrium and posture Monitors muscular activity may generate error-correcting signal to premotor and primary motor cortex

Sacral plexuses

Formed from anterior rami of spinal nerves L4-S4, immediately inferior to lumbar plexuses Innervate gluteal region, pelvis, perineum, posterior thigh, almost all leg and foot Sciatic nerve: largest and longest nerve in body Tibial nerve: formed from anterior divisions of sciatic nerve, innervates hamstrings, supplies plantar flexors of foot and toe flexors Common fibular nerve: supplies short head of biceps femoris muscle Deep fibular nerve: supplies anterior leg muscles and muscles on dorsum of foot Superficial fibular nerve: innervates lateral compartment muscles of leg

Spinal nerve characteristics

Formed from motor and sensory axons Enveloped in successive connective tissue wrappings Anterior root (ventral root) formed from multiple anterior rootlets arising from spinal cord contains motor axons only cell bodies found in anterior and lateral horns of spinal cord Posterior root (dorsal root) formed from posterior rootlets entering spinal cord contains sensory axons only cell bodies located in posterior root ganglion within posterior root Anterior root and posterior root unite within intervertebral foramen become spinal nerve Cervical nerves travel through intervertebral foramen superior to vertebra of same number e.g., second spinal nerve exits through foramen between C1 and C2 vertebrae Nerves inferior to C8 travel through intervertebral foramen inferior to vertebra of same number e.g., second thoracic nerve exits through foramen between T2 and T3 Roots of lumbar and sacral nerves travel inferiorly to reach respective intervertebral foramina collectively form the cauda equina

Secondary neuron

Interneuron within posterior horn of spinal cord or brainstem nucleus projects to thalamus (and a subsequent tertiary neuron) or cerebellum (end point)

Cranial Nerves

Olfactory nerve (CNI) - olfaction Optic nerve (CNII) - vision Oculomotor (CNIII) four extrinsic eye muscles elevates eyelid, constricts pupils, rounds lens of eye Trochlear nerve (CNIV) superior oblique eye muscle Trigeminal nerve (CNV) sensory from anterior scalp, face, oral cavity, and others muscles of mastication and others Abducens (CNVI) lateral rectus eye muscle Facial nerve (CNVII) taste anterior tongue, muscles of facial expression, others gland secretions from lacrimal, submandibular, and salivary glands Vestibulocochlear nerve (CNVIII) - hearing, equilibrium Glossopharnygeal (CNIX) sensory and taste to posterior tongue sensory to part of pharynx and others stylopharyngeus muscle secretions from parotid gland Vagus nerve (CNX) visceral sensory from heart, lungs, and abdominal organs general sensory from part of pharynx, larynx, others most pharyngeal and all laryngeal muscles smooth muscles and glands of heart, lungs, larynx, and most abdominal organs Accessory nerve (CNXI) - trapezius and sternocleidomastoid muscle Hypoglossal (CNXII) - intrinsic and extrinsic tongue muscles

olive

On each side of the medulla oblongata is an oval swelling large bundle of nerve fibers arises and passes to the cerebellum

Epithalamus

Partially forms posterior roof of diencephalon, covers the third ventricle Components of epithalamus Pineal gland: endocrine gland secreting melatonin helps regulate day-night cycles, circadian rhythm Habenular nuclei: involved in visceral and emotional responses to odors

Subdivisions of white matter

Partitioned into three regions, each called a funiculus, a column with both motor and sensory axons/ascending and descending tracts Posterior funiculus: between posterior gray horns and posterior median sulcus Lateral funiculus: on lateral side of spinal cord Anterior funiculus: between anterior gray horns and anterior median fissure, interconnected by the white commissure Axons within funiculus organized into smaller tracts or fasciculi conduct either sensory nerve or motor nerve signals

Conduction pathways characteristics

Pathways (either motor or sensory) travel through white matter Axons with similar functions/destinations are grouped together in bundles called tracts Nuclei (collections of neuron cell bodies, grey matter) are also found in the spinal cord as well as the brain Most pathways cross over from one side of body to other Contralateral vs. ipsilateral Tracts are paired, i.e. each tract has a mirror pathway on the opposite side of the spinal column Most pathways are composed of a series of two or three neurons - the fewer the neurons the faster the signal sensory pathways usually composed of three neurons: primary, secondary, and tertiary sensory neurons Exception - sensory pathways going to cerebellum only two neurons motor pathways usually composed of two neurons: upper motor neuron and lower motor neurons

Other nuclei in the medulla oblongata control vital visceral activities

Peripheral nerves conduct impulses originating in the cardiac center to the heart, where they increase or decrease heart rate. 2.Certain cells of the vasomotor center initiate impulses that affect smooth muscle in the walls of blood vessels and stimulate them to contract, constricting the vessels (vasoconstriction) and thereby increasing blood pressure. A decrease in the activity of these cells can produce the opposite effect—dilation of the blood vessels (vasodilation) and a consequent drop in blood pressure. 3.The respiratory center maintains the basic rhythm of breathing and adjusts the rate and depth of breathing to meet changing needs.

Blood-brain barrier

Strictly regulates which substances enter brain's interstitial fluid Helps prevent neuron exposure to harmful substances e.g., drugs, blood waste products, and variations in levels of normal substances (ions, hormones, etc.) Composition Most capillaries in brain wrapped by astrocyte extensions called perivascular feet Endothelial cells and perivascular feet both contributing to BBB Continuous basement membrane of endothelial cells Tight junctions between adjacent endothelial cells reduce capillary permeability Astrocyte "gatekeepers" controlling materials leaving neurons Barrier not absolute Lipid-soluble compounds can diffuse across endothelial plasma membranes e.g., nicotine, alcohol, some anesthetics Can be damaged by drugs such as cocaine Missing or reduced in 3 locations: choroid plexus needs to be permeable to produce CSF hypothalamus and pineal gland produce hormones requiring access to bloodstream

temporal lobes association area

The association areas of the temporal lobes and the regions at the posterior ends of the lateral sulci interpret complex sensory experiences, such as those needed to understand speech and to read. These regions also store memories of visual scenes, music, and other complex sensory patterns. The occipital lobes have association areas adjacent to the visual centers. These are important in analyzing visual patterns and combining visual images with other sensory experiences, such as when one person recognizes another. within temporal lobe, posteroinferior to primary auditory complex interprets characteristics of sound, stores memories of sound heard in the past

insula association area

The functions of the insula are not as well known as those of the other lobes because of the insula's location deep within the cerebrum. As mentioned earlier, it is the location of some sensory areas processing taste information.

Spinal nerve locations

Therefore, although there are seven cervical vertebrae, there are eight pairs of cervical nerves (numbered C1 to C8). There are twelve pairs of thoracic nerves (numbered T1 to T12), five pairs of lumbar nerves (numbered L1 to L5), five pairs of sacral nerves (numbered S1 to S5), one pair of coccygeal nerves (Co).

Sensory pathways

also known as ascending pathways signals from sensory receptors ascending to brain Primary neuron Secondary neuron Tertiary neuron

Motor pathways

also known as descending pathways signals from brain to muscles or glands

frontal lobe

anterior portion of each cerebral hemisphere. It is bordered posteriorly by a central sulcus (fissure of Rolando), which passes out from the longitudinal fissure at a right angle, and inferiorly by a lateral sulcus (fissure of Sylvius), which exits the undersurface of the brain along its sides deep to frontal bone, forms anterior part of cerebral hemisphere ends posteriorly at deep groove, central sulcus ends inferiorly at groove, lateral sulcus primarily concerned with: voluntary motor functions concentration and verbal communication decision making, planning, and personality

ventral root

anterior, or motor, root each spinal nerve consists of axons from the motor neurons whose cell bodies lie within the gray matter of the cord A ventral root and a dorsal root unite to form a spinal nerve, which extends outward from the vertebral canal through an intervertebral foramen

pons

appears as a rounded bulge on the underside of the brainstem where it separates the midbrain from the medulla oblongata dorsal portion of the pons consists mostly of longitudinal nerve fibers, which relay information between the medulla oblongata and the cerebrum. Its ventral portion contains large bundles of transverse nerve fibers, which conduct impulses from the cerebrum to centers within the cerebellum. Several nuclei of the pons relay sensory information from peripheral nerves to higher brain centers. Other nuclei may function with centers of the medulla oblongata to control breathing. Bulging region on anterior brainstem Sensory and motor tracts located here, connect to brain and spinal cord Middle cerebellar peduncles transverse axons connecting pons to cerebellum Pontine respiratory center helps regulate skeletal muscles of breathing Superior olivary complex inferior pons, involved in pathway for sound localization Cranial nerve nuclei sensory and motor nuclei for: trigeminal, abducens, facial, and vestibulocochlear nerves

cerebral aqueduct

aqueduct of Sylvius narrow canal connects the third ventricle to the fourth ventricle and passes lengthwise through the brainstem ventricle is continuous with the central canal of the spinal cord and has openings in its roof that lead into the subarachnoid space of the meninges.

subarachnoid space

arachnoid and pia maters contains the clear, watery cerebrospinal fluid completely surrounds the brain and spinal cord potential space between arachnoid and overlying dura mater becomes actual space if blood or fluid accumulates there, termed subdural hematoma

General somatic afferent fibers

conduct sensory impulses inward to the brain or spinal cord from receptors in the skin and skeletal muscles

olfactory nerves

are associated with the sense of smell and include only sensory neurons. These bipolar neurons, located in the lining of the upper nasal cavity, serve as olfactory receptor cells. Axons from these receptor cells pass upward through the cribriform plates of the ethmoid bone, conducting impulses to the olfactory neurons in the olfactory bulbs, which are extensions of the cerebral cortex just beneath the frontal lobes. Sensory impulses move from the olfactory bulbs along olfactory tracts to cerebral centers where they produce the sensation of smell.

vestibulocochlear nerves

are sensory nerves that arise from the medulla oblongata. Each of these nerves has two distinct parts—a vestibular branch and a cochlear branch. The neuron cell bodies of the vestibular branch fibers are located in ganglia near the vestibule and semicircular canals of the inner ear. These structures contain receptors that sense changes in the position of the head and, in response, initiate and send impulses to the cerebellum, where they are used in reflexes that maintain equilibrium. The neuron cell bodies of the cochlear branch fibers are located in a ganglion of the cochlea, a part of the inner ear that houses the hearing receptors. Impulses from this branch pass through the medulla oblongata and midbrain on their way to the temporal lobe, where they are interpreted.

sciatic nerves

are the largest and longest nerves in the body, formed by the common fibular nerve and the tibial nerve wrapped in a connective tissue sheath

Fasciculus gracilis and fasciculus cuneatus

are tracts in the posterior funiculi of the spinal cord fibers conduct sensory impulses from the skin, muscles, tendons, and joints to the brain, where they are interpreted as sensations of touch, pressure, and body movement. medulla oblongata most of the fasciculus gracilis and fasciculus cuneatus fibers cross (decussate) from one side to the other

oculomotor nerves

arise from the midbrain and pass into the orbits of the eyes. One component of each nerve connects to a number of voluntary muscles, including those that raise the eyelids and four of the six muscles that move the eye. second portion of each oculomotor nerve is part of the autonomic nervous system, supplying involuntary muscles inside the eyes. These muscles help adjust the amount of light that enters the eyes and help focus the lenses. This nerve is considered motor, with some proprioceptive fibers.

glossopharyngeal nerves

associated with the tongue and pharynx. These nerves arise from the medulla oblongata. They are mixed nerves, with predominant sensory fibers that conduct impulses from the lining of the pharynx, tonsils, and posterior third of the tongue to the brain. Fibers in the motor component of the glossopharyngeal nerves innervate certain salivary glands and a constrictor muscle in the wall of the pharynx that functions in swallowing.

Reflex Behavior

automatic responses to changes (stimuli) inside or outside the body carry out the automatic actions involved in swallowing, sneezing, coughing, and vomiting.

postganglionic fiber

axon of such a second neuron it extends to a visceral effector

Brain Development

begins as the neural tube that gives rise to the central nervous system three major cavities, or vesicles, at one end—the forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon) forebrain divides into anterior and posterior portions (telencephalon and diencephalon, respectively), and the hindbrain partially divides into two parts (metencephalon and myelencephalon) resulting five cavities persist in the mature brain as the fluid-filled ventricles and the tubes that connect them. Cells of the tissue surrounding the spaces differentiate into the structural and functional regions of the brain. On a cellular level, the brain develops as specific neurons attract others by secreting growth factors. In the embryo and fetus, the brain overgrows, and then apoptosis (programmed cell death) destroys excess cell

spinothalamic tract

begins at various levels of the spinal cord and conducts sensory impulses associated with the sensations of pain and touch to the thalamus

Tegmentum

between substantia nigra and periaqueductal gray matter contains red nuclei, color due to blood vessel density and iron contains reticular formation, integrates information from cerebrum and cerebellum issues involuntary motor commands to erector spinae muscles, helps maintain posture

Substantia nigra

bilaterally symmetrical nuclei, black appearance due to melanin pigmentation houses neurons producing dopamine involved in movement, emotions, pleasure and pain response pathology here in Parkinson disease

mixed nerves

both sensory and motor fibers

brainstem

brain to the spinal cord. It consists of the midbrain, pons, and medulla oblongata. These structures include many tracts of nerve fibers and masses of gray matter called nuclei

inferior peduncles

brings sensory information concerning the position of body parts such as limbs and joints to the cerebellum via the spinal cord and medulla oblongata

thalamus

bulges into the third ventricle from each side selective gateway for sensory impulses ascending from other parts of the nervous system to the cerebral cortex receives all sensory impulses (except those associated with the sense of smell) and channels them to appropriate regions of the cortex for interpretation all regions of the cerebral cortex can communicate with the thalamus by means of descending fibers. relays sensory information by synchronizing action potentials Paired oval masses of gray matter on lateral walls of third ventricle Composed of about a dozen thalamic nuclei organized into groups projecting to particular regions of cortex Interthalamic adhesion: midline mass of gray matter connecting bodies Functions Receives impulses from all conscious senses except olfaction Principal and final relay point for incoming sensory information - processed and projected to primary somatosensory cortex Information filter e.g., "filters out" sounds in a busy cafeteria while you study

Cerebrospinal fluid functions

buoyancy brain actually floats, reduces apparent weight by 95% prevents collapse of brain through foramen magnum protection provides liquid cushion, protecting delicate neural structures from sudden movements environmental stability transports nutrients and chemical messengers to brain, removes waste products (to venous circulation), and protects tissue from chemical fluctuations

basal nuclei

called the basal ganglia, are masses of gray matter deep within the cerebral hemispheres include the caudate nucleus, the putamen, and the globus pallidus, and they develop from the anterior portion of the forebrain produce the inhibitory neurotransmitter dopamine basal nuclei interact with other brain areas, including the motor cortex, thalamus, and cerebellum. These interactions, through a combination of stimulation and inhibition, facilitate voluntary movement

Long-term memory

can hold much more information long-term memory establishes new synaptic connections through increased branching of axons and dendrites can be converted from short-term memory if information repeated termed encoding may exist for limitless periods of time needs to be retrieved occasionally or can be "lost" e.g., voluntary motor activity in premotor cortex and cerebellum e.g., memory of sounds stored in auditory association area

cerebellar peduncles

cerebellum communicates with other parts of the CNS by means of three pairs of nerve tracts

primary motor areas

cerebral cortex lie in the precentral gyri of the frontal lobes just in front of the central sulcus and in the anterior wall of this sulcus distribution can be diagrammed as motor homunculus displays distorted proportions of the body, reflecting amount of cortex reflected to each part more motor activity devoted to human hand than in other animals

Parahippocampal gyrus

cerebral cortical tissue in temporal lobe function associated with the hippocampus

dominant hemisphere

cerebral hemispheres participate in basic functions, such as receiving and analyzing sensory impulses, controlling skeletal muscles on opposite sides of the body, and storing memory Most people, left hemisphere is dominant for the language-related activities of speech, writing, and reading intellectual functions requiring verbal, analytical, and computational skills other people, the right hemisphere is dominant, and in some, the hemispheres are equally dominant nondominant hemisphere specializes in nonverbal functions, in addition to carrying on basic functions. Nonverbal functions include motor tasks that require orientation of the body in space, understanding and interpreting musical patterns, and visual experiences. also provides emotional and intuitive thought processes. Petalias, shape asymmetries of frontal and occipital lobes Right frontal petalias right frontal lobe projection farther than the left frontal lobe Left occipital petalias left occipital lobe projecting farther than right occipital lobe Right-handed individual with these patterns

cerebellar cortex

cerebrum, the cerebellum is primarily composed of white matter with a thin layer of gray matter

sympathetic trunks

chains along the sides of the vertebral column. These ganglia, with the fibers that connect them

myotome

collection of muscles innervated by motor nerve fibers of a particular spinal nerve

descending tracts

conduct impulses from the brain to motor neurons reaching muscles and glands

lateral and anterior spinothalamic tracts

conduct impulses from various body regions to the brain and give rise to sensations of pain and temperature. interpreted as touch and pressure. Impulses in these tracts cross over in the spinal cord

General visceral efferent fibers

conduct motor impulses outward from the brain or spinal cord to smooth muscle and glands associated with internal organs

Special somatic efferent fibers

conduct motor impulses outward from the brain to the muscles used in chewing, swallowing, speaking, and forming facial expressions.

Special visceral afferent fibers

conduct sensory impulses inward to the brain from the olfactory and taste receptors.

Special somatic afferent fibers

conduct sensory impulses inward to the brain from the receptors of sight, hearing, and equilibrium

Association Areas of the Cortex

connect with each other and with other brain structures occupy the anterior portions of the frontal lobes and are widespread in the lateral portions of the parietal, temporal, and occipital lobes. Association areas analyze and interpret sensory experiences and help provide memory, reasoning, verbalizing, judgment, and emotions Association areas often interact. The area where the occipital, parietal, and temporal lobes meet processes sensory information from all three of these association areas. It plays a role in integrating visual, auditory, and other sensory information and then interpreting a situation

vermis

connects the cerebellar hemispheres at the midline.

corpus callosum

connects the cerebral hemispheres. A layer of dura mater called the falx cerebri separates them connect the cerebral hemispheres, enable the dominant hemisphere to control the motor cortex of the nondominant hemisphere. These fibers also transfer sensory information reaching the nondominant hemisphere to the general interpretative area of the dominant one, where the information can be used in decision making.

Amygdaloid body

connects to the hippocampus involved in several aspects of emotion, especially fear, can help store emotions depending on emotional context

peripheral nervous system

consists of the nerves that branch from the CNS includes the cranial nerves that arise from the brain and the spinal nerves that arise from the spinal cord.

cerebral hemispheres

consists of two large masses are essentially mirror images of each other

Sensory nuclei

contain interneuron bodies in posterior horns Somatic sensory nuclei receive nerve signals from sensory receptors Visceral sensory nuclei receive nerve signals from blood vessels and viscera

Motor nuclei

contain motor neuron cell bodies in anterior and lateral horns Somatic motor nuclei innervate skeletal muscle in anterior horn Autonomic motor nuclei innervate smooth muscle, cardiac muscle, glands

rubrospinal tracts

cross over in the brain and pass through the lateral funiculi conduct impulses from the brain to synapses with lower motor neurons, and help to coordinate muscle actions.

Spinal Dura mater

deep to epidural space provides stability to spinal cord fuses with connective tissues surrounding nerves Subdural space potential space between dura mater and arachnoid mater seen only in histologic preparations

Spinal Pia Mater

deep to subarachnoid space innermost meningeal layer of elastic and collagen fibers adheres to spinal cord and supports blood vessels

Primary neuron

dendrites part of the receptor that detects stimulus cell bodies located in posterior root ganglia of spinal nerves axon projecting to secondary neuron within CNS (spine or brainstem)

diencephalon

develops from the posterior forebrain and is located between the cerebral hemispheres and superior to the brainstem surrounds the third ventricle and is largely composed of gray matter Components of diencephalon: epithalamus, thalamus, and hypothalamus Provides the relay and switching centers for: sensory and motor pathways control of visceral activities

femoral nerves

divide into many branches, supplying motor impulses to muscles of the anterior thighs and receiving sensory impulses from the skin of the thighs and legs.

Vertebrae

do not exactly match up with spinal cord division due to longer vertebrae growth than spinal cord growth in adult, spinal cord shorter than vertebral canal

dorsal branch

dorsal ramus each spinal nerve turns posteriorly and innervates the muscles and skin of the back

crossed extensor reflex

due to interneuron pathways in the spinal cord that allow sensory impulses arriving on one side of the cord to pass across to the other side and produce an opposite effec

Lumbosacral enlargement

due to neurons that innervate the lower limbs

Cervical enlargement

due to neurons that innervate the upper limbs

limbic system

emotional experience and expression and can modify the way a person acts, producing such feelings as fear, anger, pleasure, and sorrow. The limbic system reacts to potentially life-threatening upsets in a person's physical or psychological condition. By causing pleasant or unpleasant feelings about experiences, the limbic system guides behavior that may increase the chance of survival. In addition, parts of the limbic system interpret sensory impulses from the receptors associated with the sense of smell (olfactory receptors) Composed of multiple cerebral and diencephalic structures, forming a ring around the diencephalon Collectively process and experience emotions

medulla oblongata

enlarged continuation of the spinal cord, extending from the level of the foramen magnum to the pons dorsal surface flattens to form the floor of the fourth ventricle, and its ventral surface is marked by descending tracts ascending and descending nerve fibers connecting the brain and spinal cord must pass through the medulla oblongata gray matter breaks up into nuclei separated by nerve fibers Most caudal part of the brainstem, continuous with spinal cord inferiorly Caudal portion with flattened, rounded shape and narrow central canal - canal enlarges and becomes fourth ventricle All tracts between brain and spinal cord passing through here Pyramids two longitudinal ridges on anterior surface that house motor projection tract, corticospinal tracts most cross to opposite side of brain (cerebral hemispheres controls movement on opposite side), through a structure called decussation of the pyramids Olive bulge immediately lateral to each pyramid, relays ascending sensory impulses to cerebellum Inferior cerebellar peduncles tracts connecting medulla to cerebellum Cardiac center regulates heart's rate and strength of contraction Vasomotor center controls blood pressure - alters diameters of arterioles increased blood pressure when vessels constrict, decreased bp when vessels relax Medullar respiratory center regulates respiratory rate Other nuclei in the medulla involved in coughing, sneezing, and salivation, swallowing, gagging, and vomiting Cranial nerve nuclei vestibulocochlear, glossopharnygeal, vagus, accessory, and hypoglossal

Terminating Autonomic Neurotransmitter Actions

enzyme acetylcholinesterase rapidly decomposes the acetylcholine that cholinergic fibers release enzyme monoamine oxidase, in mitochondria, then inactivates norepinephrine

perineurium

fascicle is enclosed in a sleeve of loose connective tissue give rise to a network of capillaries in the endoneurium that provides oxygen and nutrients to the neurons

phrenic nerves

fibers from the third, fourth, and fifth cervical nerves pass into the right and left conduct motor impulses to the muscle fibers of the diaphragm.

norepinephrine (20%) and epinephrine (80%)

fibers terminate in the glands on special hormone-secreting cells

nucleus gracilis and the nucleus cuneatus

for example, receive sensory impulses from fibers of ascending tracts and pass them on to the thalamus or the cerebellum.

sensory memory

form important association based on sensory input lasts for seconds

Lateral horns

found in T1-L2 parts of spinal cord contain cell bodies of autonomic motor neurons innervate cardiac muscle, smooth muscle, glands

frontal lobes association Area

frontal lobes provide higher intellectual processes, such as concentrating, planning, and complex problem solving anterior and inferior portions of these lobes (prefrontal areas) control emotional behavior and produce awareness of the possible consequences of behaviors. These abilities are also collectively called executive function.

fourth ventricle

in the brainstem anterior to the cerebellum located between pons and cerebellum communicates with third ventricle through cerebral aqueduct opens to subarachnoid space via medial aperture and paired lateral apertures narrows before merging with central canal in the spinal cord

autonomic nervous system

includes fibers that connect the CNS to viscera such as the heart, stomach, intestines, and various glands

conus medullaris

inferior to the lumbar enlargement, the spinal cord tapers to a structure

Tertiary neuron

interneuron residing in thalamus axon projects to primary somatosensory cortex

cerebellum

large mass of tissue inferior to the occipital lobes of the cerebrum and posterior to the pons and medulla oblongata consists of two lateral hemispheres partially separated by a layer of dura mater called the falx cerebelli Second largest part of the brain Produces fine control and coordination over muscular actions Stores memories of movement patterns e.g., playing scales on a piano

trigeminal nerves

largest and arise from the pons. They are mixed nerves, with more extensive sensory portions. Each sensory component includes three large branches, called the ophthalmic, maxillary, and mandibular divisions ophthalmic division of each the trigeminal nerve consists of sensory fibers that conduct impulses to the brain from the surface of the eye; the tear gland; and the skin of the anterior scalp, forehead, and upper eyelid. The fibers of the maxillary division conduct sensory impulses from the upper teeth, upper gum, and upper lip, as well as from the mucous lining of the palate and facial skin. The mandibular division includes both motor and sensory fibers. The sensory branches conduct impulses from the scalp behind the ears, the skin of the jaw, the lower teeth, the lower gum, and the lower lip. The motor branches supply the muscles of mastication and certain muscles in the floor of the mouth.

lateral ventricles

largest. first ventricle is in the left cerebral hemisphere and the second ventricle is in the right cerebral hemisphere. They extend anteriorly and posteriorly into the cerebral hemispheres.

lateral reticulospinal tracts

lateral funiculi, whereas the anterior and medial reticulospinal tracts are in the anterior funiculi fibers in the lateral tracts cross over, whereas others remain uncrossed anterior and medial tracts remain uncrossed Motor impulses conducted on the reticulospinal tracts originate in the brain and control muscular tone and activity of sweat glands.

Anterior horns

left and right anterior masses of gray matter house cell bodies of somatic motor neurons innervating skeletal muscle

Posterior horns

left and right posterior masses of gray matter axons of sensory neurons and cell bodies of interneurons

Spinal Epidural space

lies between dura mater and inner walls of the vertebra has areolar connective tissue, blood vessels, adipose tissue epidural anesthetics introduced here

temporal lobe

lies inferior to the frontal and parietal lobes and is separated from them by the lateral sulcus. internal to temporal bone, inferior to lateral sulcus responsible for: hearing and smell

memory consolidation

memories are stored in various parts of the cerebral cortex hippocampus plays an important role in directing memory information to the appropriate location in the cortex, although it does not actually store memories. Another area of the temporal lobe, the amygdala, assigns value to a memory, such as whether it was pleasant.

facial nerves

mixed nerves that arise from the lower part of the pons and emerge on the sides of the face. Their sensory branches are associated with taste receptors on the anterior two-thirds of the tongue, and some of their motor fibers conduct impulses to muscles of facial expression. Still other motor fibers of these nerves function in the autonomic nervous system by stimulating secretions from tear glands and certain salivary glands

muscarinic receptors

muscarinic receptors are in the membranes of effector cells at the ends of all postganglionic parasympathetic nerve fibers and at the ends of the cholinergic sympathetic fibers. Responses from these receptors are excitatory and relatively slow

third ventricle

narrow space that constitutes in the mid-line of the brain beneath the corpus callosum smaller, thinner, communicates with each lateral ventricle through the interventricular foramen

posterior and anterior spinocerebellar tracts

near the surface in the lateral funiculi of the spinal cord posterior tracts remain uncrossed, whereas those in the anterior tracts cross over in the medulla fibers originate in the muscles of the lower limbs and trunk and then travel to the cerebellum. These impulses coordinate muscular movements

cervical enlargement

neck region, a thickening in the spinal cord, supplies nerves to the upper limbs

Cauda equina

nerve roots projecting inferiorly from spinal cord, contains filum terminale thin strand of pia mater that helps anchor conus medullaris to coccyx

pyramidal cells

nervous tissue in these regions contains many large named for their pyramid-shaped cell bodies Impulses from the pyramidal cells move downward through the brainstem and into the spinal cord on descending tracts. Most of the nerve fibers in these tracts cross over from one side of the brain to the other within the brainstem. Impulses conducted on these pathways in special patterns and frequencies are responsible for movements in skeletal muscles. cells in the upper portions of the motor areas send impulses to muscles in the thighs and legs; those in the middle portions control muscles in the arms and forearms; and those in lower portions activate muscles of the head, face, and tongue. The relative (distorted) size of each area in the figure reflects the extent of the cortex devoted to it.

brain

neural centers associated with sensory functions and is responsible for sensations and perceptions issues motor commands to skeletal muscles and carries on higher mental functions, such as memory and reasoning

nicotinic receptors

nicotinic receptors are in the synapses between the preganglionic and postganglionic neurons of the parasympathetic and sympathetic pathways. They produce rapid, excitatory responses

Hippocampus

nucleus superior to parahippocampal gyrus assists in storing memories and forming long-term memory

sensory nerves

only fibers of sensory neurons, conducting impulses into the brain or spinal cord

vagus nerves

originate in the medulla oblongata and extend downward through the neck into the chest and abdomen. These nerves are mixed, including both somatic and autonomic branches, with the autonomic fibers predominant. are motor fibers that conduct impulses to muscles of the larynx and pharynx. associated with speech and swallowing reflexes that use muscles in the soft palate and pharynx. Vagal sensory fibers conduct impulses from the linings of the pharynx, larynx, and esophagus and from the viscera of the thorax and abdomen to the brain. Autonomic motor fibers of the vagus nerves supply the heart and many smooth muscles and glands in the viscera of the thorax and abdomen

accessory nerves

originate in the medulla oblongata and the spinal cord. Therefore, these nerves have both cranial and spinal branches. Each cranial branch of an accessory nerve joins a vagus nerve and conducts impulses to muscles of the soft palate, pharynx, and larynx. The spinal branch descends into the neck and supplies motor fibers to the trapezius and sternocleidomastoid muscles. This nerve is considered motor, with some proprioceptive fibers.

corticospinal tract

originates in the cerebral cortex and conducts motor impulses on so-called upper motor neurons downward through the spinal cord

cranial nerves

originating from the brain that communicate with other body parts Part of the peripheral nervous system (PNS), originate on inferior surface of brain Numbered with Roman numerals according to their position (begin with most anteriorly placed nerve), name related to function Part of the peripheral nervous system (PNS), originate on inferior surface of brain Numbered with Roman numerals according to their position (begin with most anteriorly placed nerve), name related to function

spinal nerves

originating from the spinal cord that communicate with other body parts Pathway for sensory and motor nerve signals Responsible for reflexes, quickest reactions to stimulus contain sensory and motor axons identified by first letter of spinal cord part and number 8 cervical nerves (C1-C8) 12 thoracic nerves (T1-T12) 5 lumbar nerves (L1-L5) 5 sacral nerves (S1-S5) 1 coccygeal nerve (Co1)

occipital lobe

orms the posterior portion of each cerebral hemisphere and is separated from the cerebellum by a shelflike extension of dura mater called the tentorium cerebelli. The occipital lobe and the parietal and temporal lobes have no distinct boundary. internal to occipital bone, forms posterior part of cerebral hemisphere responsible for: processing visual information storing visual memories

rapid eye movement (REM)

paradoxical sleep because some areas of the brain are active. usually lasts from five to fifteen minutes. This "dream sleep" is important. If a person lacks REM sleep for just one night, sleep on the next night makes up for it

sympathetic chain ganglia

paravertebral ganglia extend a short distance, then leave the spinal nerves through branches called white rami (sing., ramus) and enter sympathetic ganglia fibers extend through the ganglia and pass up or down the sympathetic trunk and synapse with neurons in ganglia at higher or lower levels in the chain second neurons in sympathetic pathways, the postganglionic fibers, extend from the sympathetic ganglia to visceral effectors. Most axons leaving paravertebral ganglia pass through branches called gray rami and return to a spinal nerve before extending to an effector. These branches appear gray because the postganglionic axons generally are unmyelinated, whereas nearly all of the preganglionic axons in the white rami are myelinated.

parietal lobes association area

parietal lobes have association areas that help interpret sensory information and aid in understanding speech and choosing words to express thoughts and feelings. Awareness of the form of objects, including one's own body parts, stems from the posterior regions of these lobes.

tibial and common fibular nerves

pass downward into the buttocks and descend into the thighs, where they re-emerge many branches of these nerves supply muscles and skin in the thighs, legs, and feet.

Tectum

posterior region of midbrain dorsal to aqueduct, contains two pairs of sensory colliculi, relay stations in processing visual and auditory sensation superior colliculi: control visual reflexes and tracking inferior colliculi: control auditory reflexes

parietal lobe

posterior to the frontal lobe and is separated from it by the central sulcus. deep to parietal bone forms superoposterior part of cerebral hemisphere terminates anteriorly at central sulcus terminates posteriorly at parieto-occipital sulcus terminates laterally at lateral sulcus postcentral gyrus, mass of nervous tissue posterior to central sulcus primarily concerned with: general sensory functions

dorsal root

posterior, or sensory, root can be identified by an enlargement called the dorsal root ganglion. This ganglion contains the cell bodies of the sensory neurons whose axons (peripheral processes) conduct impulses inward from peripheral body parts. The axons (central processes) of these neurons continue through the dorsal root and into the spinal cord, where they form synapses with other neurons or ascend to the brain

Parasympathetic Division

preganglionic fibers of the parasympathetic division (craniosacral division) arise from neurons in the midbrain, pons, and medulla oblongata of the brainstem and from part of the sacral region (S2-4) of the spinal cord fibers associated with parts of the head are included in the oculomotor, facial, and glossopharyngeal nerves. Those fibers that innervate organs of the thorax and upper abdomen are parts of the vagus nerves. (The vagus nerves carry about 75% of all parasympathetic fibers.) Preganglionic fibers arising from the sacral region of the spinal cord lie in the branches of the second through the fourth sacral spinal nerves, and they conduct impulses to the viscera in the pelvic cavity

cholinergic

preganglionic neurons of the sympathetic and parasympathetic divisions all secrete acetylcholine fibers are also cholinergic (one exception, parasympathetic neurons that secrete nitric oxide,

cerebrospinal fluid

protects the brain and spinal cord by absorbing forces viscous liquid that differs in composition from the fluid that leaves the capillaries in other parts of the body greater concentration of sodium and lesser concentrations of glucose and potassium than do other extracellular fluids function is nutritive as well as protective maintain a stable ionic concentration in the CNS and provides a pathway to the blood for waste CSF forms in the lateral ventricles, from where it slowly circulates into the third and fourth ventricles 500 milliliters of CSF daily. 140 milliliters are in the nervous system at any time

Sensory Areas of the Cortex

receive and interpret impulses from sensory receptors, producing feelings or sensations sensations of temperature, touch, pressure, and pain in the skin arise in the postcentral gyri of the parietal lobes posterior to the central sulcus posterior parts of the occipital lobes provide vision, whereas the superior posterior portions of the temporal lobes contain the centers for hearing. The sensory areas for taste are near the bases of the lateral sulci and include part of the insula. The sense of smell arises from centers deep in the temporal lobes. Sensory fibers from the PNS cross over in the spinal cord or the brainstem. Thus, the centers in the right central hemisphere interpret impulses originating from the left side of the body, and vice versa. However, the sensory areas concerned with vision receive impulses from both eyes, and those concerned with hearing receive impulses from both ears.

meningeal branch

reenters the vertebral canal through the intervertebral foramen and supplies (innervates) the meninges and blood vessels of the cord, as well as the intervertebral ligaments and the vertebrae

reflex arc

reflexes share the same basic components, which together are known as reflex arc begins with a sensory receptor at the dendritic end of a sensory neuron these sensory neurons enter the CNS and constitute a sensory or afferent limb of the reflex. The CNS is a processing center. Afferent neurons may synapse with interneurons, which may in turn connect with other parts of the CNS. Afferent neurons or interneurons ultimately connect with motor neurons, whose fibers pass outward from the CNS to effectors

Amygdaloid body (amygdala)

region at tail of caudate nucleus participates in: expression of emotion, control of behavioral activities, moods

hypothalamus

region of the diencephalon that includes many nuclei lies inferior to the thalamic nuclei and forms the lower walls and floor of the third ventricle The hypothalamus regulates: 1.heart rate and arterial blood pressure 2.body temperature 3.water and electrolyte balance 4.control of hunger and body weight 5.control of movements and glandular secretions of the stomach and intestines 6.production of neurosecretory substances that stimulate the pituitary gland to release hormones that help regulate growth, control various glands, and influence reproductive physiology 7.sleep and wakefulness Anteroinferior region of the diencephalon Infundibulum thin stalk extending inferiorly from hypothalamus, that attaches to pituitary gland Master control of the autonomic nervous system influences heart rate, blood pressure, digestive activities, and respiration Master control of the endocrine system oversees most of endocrine system secretes hormones that control activities in anterior pituitary gland produces antidiuretic hormone (ADH) and oxytocin Regulation of body temperature neurons detect altered temperature and signal other hypothalamic nuclei to heat or cool the body Control of emotional behavior located at the center of the limbic system, the part of the brain that controls emotional responses e.g., pleasure, aggression, fear, rage, sex drive Control of food intake monitors levels of nutrients and produces sensations of hunger Control of water intake monitors concentration of dissolved substances in blood and regulates sensation of thirst stimulated by dehydration Regulation of sleep-wake rhythms directs pineal gland to secrete melatonin regulates circadian rhythms

midbrain development

region the midbrain produces

Conversion of short-term to long-term memory

requires amygdaloid body and hippocampus hippocampus required for formation of short-term memory loss of ability to form short-term memory does not affect accessibility of long-term memory

Control of Autonomic Activity

rests mainly in the hypothalamus, although impulse integration in the autonomic nervous system's ganglia provides some independence. In contrast to control of skeletal muscle in the somatic nervous system, which is voluntary, control of the autonomic nervous system is involuntary. cerebral cortex, including the limbic system, can influence autonomic centers and increase both sympathetic and parasympathetic activities

reticular formation (RAS)

reticular activating system, extends from the superior portion of the spinal cord into the diencephalon neurons connect centers of the hypothalamus, basal nuclei, cerebellum, and cerebrum with all of the major ascending and descending tracts. responds by activating the cerebral cortex into a state of wakefulness rees the cortex from what would otherwise be a continual bombardment of sensory stimulation and allows it to concentrate on more significant information Cerebral cortex can also activate the reticular formation, intense cerebral activity keeps a person awake. In addition, the reticular formation, through connections with the basal nuclei and the motor cortex, influences motor activities to ensure that skeletal muscles move together evenly. The reticular formation also inhibits or enhances certain spinal reflexes.

gyri

ridges or convolutions separated by grooves, mark the cerebrum's surface

hypoglossal nerves

rise from the medulla oblongata and pass into the tongue. They primarily consist of fibers that conduct impulses to muscles that move the tongue in speaking, chewing, and swallowing. This nerve is considered motor, with some proprioceptive fibers. Table 11.9 summarizes the functions of the cranial nerves.

Lentiform nucleus

rounded mass positioned between external insula and lateral diencephalon composed of putamen and globus pallidus Putamen helps control muscular movements at subconscious level globus pallidus excites and inhibits thalamus to adjust muscle tone

choroid plexuses

secrete CSF tiny, reddish, cauliflower-like masses of specialized capillaries from the pia mater, covered by a single layer of specialized ependymal cells. cells are joined closely by tight junctions. block passage of water-soluble substances between the blood and the CSF (blood-CSF barrier) project into the cavities of the ventricles. selectively transfer certain substances from the blood into the CSF by facilitated diffusion and transfer other substances by active transport specialized tissue in each ventricle layer of ependymal cells and blood capillaries (within pia) Produced by secretion from ependymal cells Originates from blood plasma Composition somewhat similar to plasma

middle peduncles

send information from the cerebral cortex about the desired position of these body parts

sulcus

shallow to somewhat deep groove divide each hemisphere into lobes

lumbar enlargement

similar thickening in the lower back gives off nerves to the lower limbs. Just inferior to the

patellar reflex

simple monosynaptic reflex, so-called because it uses only two neurons—a sensory neuron communicating directly to a motor neuron. Striking the patellar ligament just below the patella initiates this reflex. The quadriceps femoris muscle group, attached to the patella by a tendon, is pulled slightly, stimulating stretch receptors in the muscle group. These receptors, in turn, trigger impulses that pass along the peripheral process of the axon of a unipolar sensory neuron, continuing along the central process of the axon into the lumbar region of the spinal cord. In the spinal cord, the sensory neuron axon synapses with a motor neuron. An impulse is then triggered on the motor neuron and is conducted along its axon to the neuromuscular junctions in that motor unit of the quadriceps femoris. The muscle fibers involved respond by contracting, and the reflex is completed as the leg extends

reflex

simplest of the nerve pathways begins with a sensory receptor and ends with an effector, and includes as few as two neurons

non-rapid eye movement (non-REM)

sleep occurs when a person is very tired, and it reflects decreasing activity of the reticular formation restful, dreamless, and accompanied by reduced blood pressure and respiratory rate sleep may range from light to heavy and is described in three stages third stage is also known as slow-wave sleep may last from seventy to ninety minutes

spinal cord

slender column of nervous tissue that is continuous with the brain and extends downward through the vertebral canal spinal cord originates where nervous tissue leaves the cranial cavity at the level of the foramen magnum cord tapers to a point and terminates near the intervertebral disc that separates the first and second lumbar vertebrae

abducens nerves

small and originate from the pons near the medulla oblongata. They enter the orbits of the eyes and supply motor impulses to the remaining pair of external eye muscles, the lateral rectus muscles. This nerve is considered motor, with some proprioceptive fibers.

trochlear nerves

smallest. They arise from the midbrain and conduct motor impulses to a fifth pair of external eye muscles, the superior oblique muscles, which are not supplied by the oculomotor nerves. The trochlear nerve is considered motor, with some proprioceptive fibers.

Categorical hemisphere

specialized for language abilities, usually contains Wernicke area and motor speech area, involved in sequential and analytical reasoning tasks the left hemisphere in most people - left-handed people with either hemisphere as categorical

spinal nerves simple

spinal cord consists of thirty-one segments, each of which gives rise to a pair nerves branch to various body parts and connect them with the CNS.

visceral branch

spinal nerves in the thoracic and lumbar regions have a fourth branch,

ascending tracts

spinal tracts that conduct sensory information to the brain

Corpus striatum

striated or striped appearance of the internal capsule includes caudate nucleus and lentiform nucleus

frontal eye field

superior part of the frontal lobe is a region motor cortex in this area controls voluntary movements of the eyes and eyelids motor cortex in this area controls voluntary movements of the eyes and eyelids. Nearby is the cortex responsible for movements of the head that direct the eyes

thoracodorsal nerve

supplies the latissimus dorsi muscle.

pudendal nerve

supplies the muscles of the perineum.

dorsal scapular nerve

supplies the rhomboid major and levator scapulae muscles.

lower subscapular nerve

supplies the subscapularis and teres major muscles.

suprascapular nerve

supplies the supraspinatus and infraspinatus muscles.

Axillary nerves

supply muscles and skin of the anterior, lateral, and posterior regions of the arm

Musculocutaneous nerves

supply muscles of the arms on the anterior sides and the skin of the forearms.

Radial nerves

supply muscles of the arms on the posterior sides and the skin of the forearms and hands

Median nerves

supply muscles of the forearms and muscles and skin of the hands.

obturator nerves

supply the adductor muscles of the thighs.

inferior and superior gluteal nerves

supply the gluteal muscles and the tensor fasciae latae muscle

lateral and medial pectoral nerves

supply the pectoralis major and pectoralis minor muscles

endoneurium

surrounds individual axons. Axons are organized in bundles called fascicles

adrenergic

sympathetic postganglionic neurons, however, secrete norepinephrine (noradrenalin) include the sympathetic postganglionic neurons that stimulate sweat glands and a few sympathetic neurons to blood vessels in skin (which cause vasodilation); these neurons secrete acetylcholine and therefore are cholinergic (adrenergic sympathetic fibers to blood vessels cause vasoconstriction).

Conus medullaris

tapering end marking end of spinal cord proper

intercostal nerves

ventral branches of the thoracic spinal nerves do not enter a plexus. Instead, they extend into spaces between the ribs under the ribs as subcostal nerves (T12). These nerves supply motor impulses to the intercostal muscles and the upper abdominal wall muscles.

ventral branch

ventral ramus forward to supply muscles and skin on the front and sides of the trunk and limbs

fissure

very deep groove Longitudinal fissure: separates the cerebral hemispheres Transverse fissure: separates cerebrum from cerebellum Lateral fissure/Sulcus: separates temporal and parietal lobes Sylvian Fissure Central fissure/Sulcus: separates the frontal and parietal lobes Fissure of Rolando Parieto-occipital fissure: separates parietal and occipital lobes

cerebrum

which develops from the anterior portion of the forebrain, is the largest part of the mature brain Origin of all complex intellectual functions Two large hemispheres on superior aspect of brain Center of: intelligence and reasoning thought, memory, and judgment voluntary motor, visual, and auditory activities

posterior pituitary gland

which hangs from the floor of the hypothalamus

epidural space

which lies between the dural sheath and the bony walls (fig. 11.2). This space contains blood vessels, loose connective tissue, and adipose tissue that pad the spinal cord. potential space between dura mater and bones of the skull contains blood vessels nourishing meninges and cranium becomes real space if blood or fluid accumulates

optic tracts

which originate from the optic chiasma

Premotor cortex

within frontal lobe anterior to precentral gyrus responsible for coordinating skilled motor activities, e.g., playing the piano

Visual association area

within occipital lobe, surrounds primary visual area helps process visual information, helps us identify things we see e.g., helps integrate visual information into recognizable face

Somatosensory association area

within parietal lobe posterior to primary somatosensory complex integrates sensory information, determines texture, temperature, pressure, and shape of objects allows us to identify known objections without seeing them

Short-term Memory

working," memories are thought to involve neurons connected in a circuit and stimulated so rapidly that the likelihood of neurons in the circuit reaching threshold is temporarily increased. As long as the circuit is facilitated, the memory persists, but if the stimulus is removed, the circuit becomes inactive