chap 13

sensory areas

-information arrives in posterior half of both cerebral hemispheres, behind the central sulci -usually receive input both from the primary areas and from other brain regions -Sensory association areas integrate sensory experiences to generate meaningful patterns of recognition and awareness

spinal cord is also protected by

-fat and connective tissue located in the -Epidural space: A space between the dura mater the vertebral canal

trochlear ( IV 4 ) nerves

-Motor cranial nerve -originate in the trochlear nucleus in the midbrain to the muscle that controls movement of the eyeball

Medulla oblongata

-between the spinal cord and the diencephalon - superior part of the spinal cord, inferior part of the brain stem. -begins at the foramen magnum,Extends to inferior border of the pons, About 3 cm.

Nuclei in PONS

-pneumotaxic area -apneustic area of the respiratory center -Together with the medullary rhythmicity area, they help control breathing.

white matter

-Organized into regions _anterior and posterior gray horns divide the white matter into three broad areas called columns -Anterior (ventral) white columns -Posterior (dorsal) white columns -Lateral white columns Each column contains bundles of axons

medulla's Pyramids

-Pyramids: White matter that forms bulges on the anterior aspect of the medulla -Decussation of pyramids: superior to the spinal cord. *90% of the axons in the left pyramid cross to the right side, *90% of the axons in the right pyramid cross to the left side *explains why each side of the brain controls voluntary movements on the opposite side of the body.

Conus Medullaris/Filum terminale

-Conus Medullaris: *Inferior to the lumbar enlargement *terminates as a tapering, conical structure *1st & 2nd lumbar vertebrae -Filum terminale: * Extension of the pia mater *Blends with the arachnoid mater and dura mater *Anchors the spinal cord to the coccyx

association areas

large areas of the occipital, parietal, and temporal lobes and of the frontal lobes anterior to the motor areas

PONS

- superior to the medulla -Anterior to the cerebellum -2.5 cm (1 in.) long -bridge that connects different parts of the brain with one another, provided by bundles of axons -consists of nuclei, sensory tracts, and motor tracts

middle cerebellar peduncles

-Axons carry commands for voluntary movements into the cerebellum -primary function is to evaluate how well movements initiated by motor areas in the cerebrum are actually being carried out. -When movements are not being carried out correctly, the cerebellum detects the discrepancies -sends feedback signals to motor areas of the cerebral cortex *feedback signals help correct the errors, smooth the movements, and coordinate complex sequences of skeletal muscle contractions

Four major part

-Brain stem: *Continuous w/ the spinal cord *medulla oblongata, pons, and midbrain -Cerebellum * back of brain stem Diencephalon *top of brain stem *thalamus, hypothalamus, and epithalamus -Cerebrum *largest part of brain

The Limbic System

-Encircling the upper part of the brain stem and the corpus callosum -Ring of structures on the inner border of the cerebrum and floor of the diencephalon

Dermatomes

-Somatic sensory neurons: *skin over the entire body is supplied by these nerves that carry nerve impulses from the skin into the spinal cord and brain *Each spinal nerve contains sensory neurons that serve a specific, predictable segment of the body *If skin in a particular region is stimulated but the sensation is not perceived, the nerves supplying that dermatome are probably damaged

Function Organization of the cerebral cortex (sensory/ motor)

-Specific types of sensory, motor, and integrative signals are processed in certain regions of the cerebral cortex -Motor areas control the execution of voluntary movements Association areas deal with more complex integrative functions such as memory, emotions, reasoning, will, judgment, personality traits, and intelligence. -Sensory areas receive sensory information and are involved in perception, the conscious awareness of a sensation

Midbrain Tectum/Superior colliculi

-Tectum: posterior part of the midbrain, contains four rounded elevations -Superior colliculi : Serve as reflex centers for certain visual activities *From the retina of the eye to the superior colliculi to the extrinsic eye muscles *Responsible for reflexes that govern movements of the head, eyes, and trunk in response to visual stimuli

stretch reflex posture

-The stretch reflex can also help maintain posture,If a standing person begins to lean forward. -Gastrocnemius and other calf muscles are stretched. -Stretch reflexes are initiated in these muscles, Cause them to contract and reestablish the body's upright posture -Similar types of stretch reflexes occur in the muscles of the shin, when a standing person begins to lean backward

Roots

-Two bundles of axons,connect each spinal nerve to a segment of the cord by even smaller bundles of axons called rootlets 1.posterior(dorsal) root: *Sensory neurons *Conduct nerve impulses from sensory receptors in skin, muscles, and internal organs into the central nervous system *posterior (dorsal) root ganglion:Contains the cell bodies of sensory neurons 2.The anterior(ventral) root: *Motor neurons *Conduct nerve impulses from the CNS to effectors (muscles and glands)

cranial nerves

-arise from the brain inside the cranial cavity and pass through various foramina in the bones of the cranium -Each cranial nerve has both a number, designated by a roman numeral, and a name

lobes of the cerebrum

-central sulcus: separates the frontal lobe from the parietal lobe -parietooccipital sulcus separates the parietal lobe from the occipital lobe -Precentral gyrus: Located anterior to the central sulcus contains the primary motor area -Postcentral gyrus: Located posterior to the central sulcus contains the primary somatosensory area of the cerebral cortex -lateral cerebral sulcus separates the frontal lobe from the temporal lobe -insula, lies within the lateral cerebral sulcus, deep to the parietal, frontal, and temporal lobes

Spinal nerves

-communication between spinal cord and specific regions of the body -31 pairs of spinal nerves emerge from intervertebral foramina -Part of PNS -Connect the CNS to sensory receptors, muscles, and glands in all parts of the body -31 pairs of spinal nerves are named from where they emerge -Each pair of spinal nerves arises from a spinal segment * 8 pairs of cervical nerves Cl—C8 *12 pairs of thoracic nerves T1—T12 *5 pairs of lumbar nerves L 1—L5 *5 pairs of sacral nerves S1—S5 *1 pair of coccygeal nerves Col

Medulla Vital functions

-contains several nuclei, some control vital body functions -Regulate vital activities: *The cardiovascular center: Rate and force of the heartbeat *medullary rhythmicity area: Adjusts the basic rhythm of breathing -Nuclei associated with sensations of touch, pressure, vibration, and conscious proprioception are located in the posterior part of the medulla

cerebral cortical region

-cortical region rolls and folds upon itself. -folds are called gyri = circles, or convolutions -fissures are deepest grooves between folds -sulci are shallower grooves between folds

Protective coverings of the brain

-cranial meninges, continuous with the spinal meninges Same basic structure,Same names

Cerebral Hemispheres

-longitudinal fissure separates the cerebrum into right and left halves -falx cerebri: Within the longitudinal fissure between the cerebral hemispheres -connected internally by the corpus callosum, broad band of white matter containing axons that extend between the hemispheres

Medulla Nerves

-nuclei associated with five pairs of cranial nerves: Vestibulocochlear (VIII) nerves Glossopharyngeal (IX) nerves Vagus (X) nerves Acessory (XI) nerves Hypoglossal (XII) nerves

specific primary motor areas(4,44&45)

-primary motor area (area 4): *precentral gyrus of the frontal lobe *controls voluntary contractions of specific muscles or groups of muscles *Electrical stimulation of any point causes contraction of specific skeletal muscle fibers on the opposite side of the body -Broca's speech area (areas 44 and 45): *frontal lobe close to the lateral cerebral sulcus *articulation of speech *Neural circuits established between Broca's speech area, the premotor area, and primary motor area activate muscles of the larynx, pharynx, and mouth and breathing muscles *People who suffer a stroke in this area can still have clear thoughts, but are unable to form words

diencephalon hypothalamus

-small, inferior to the thalamus. -Controls many body activities, Major regulators of homeostasis -Sensory impulses related to somatic and visceral sense Impulses from receptors for vision, taste, and smell -Receptors continually monitor osmotic pressure, glucose level, certain hormone concentrations, and the temperature of blood -Control of the ANS *Production of hormones *Regulation of emotional and behavioral patterns *Regulation of eating and drinking *Control of body temperature *Regulation of circadian rhythms and states of consciousness

specific primary sensory areas. (touch 1-3,sight 17, sound 41&42, taste 43,smell 28)

-somatosensory area (areas 1, 2, and 3) : * posterior the central sulcus of each cerebral hemisphere in the postcentral gyms of each parietal lobe. *receives nerve impulses for touch, pressure, vibration, itch, tickle, temperature (coldness and warmth), pain, and proprioception (joint and muscle position) and is involved in the perception of these somatic sensations -primary visual area (area 17): *posterior tip of the occipital lobe, on the medial surface (next to the longitudinal fissure) *receives visual information and is involved in visual perception -primary auditory area (areas 41 and 42) : *superior part of the temporal lobe near the lateral cerebral sulcus *Receives information for sound and is involved in auditory perception -primary gustatory area (area 43): *base of the postcentral gyms superior to the lateral cerebral sulcus in the parietal cortex *Receives impulses for taste and is involved in gustatory perception and taste discrimination -primary olfactory area (area 28) : *in the temporal lobe on the medial aspect. *Receives impulses for smell and is involved in olfactory perception

Stretch Reflex

-stretch reflex causes contraction of a skeletal muscle (the effector) in response to stretching of the muscle -occurs via a monosynaptic reflex arc -Activation of a single sensory neuron that forms one synapse in the CNS with a single motor neuron -Tapping on tendons attached to muscles at the elbow, wrist, knee, and ankle joints -An example is the patellar reflex

Circulation of the CSF/ Reabsorbed

1. CSF FORMED in the choroid plexuses of each lateral ventricle, flows into the third ventricle through the interventricular foramina 2. More CSF is ADDED in the roof of the third ventricle 3.The fluid FLOWS through the midbrain (cerebral aqueduct), which passes into the fourth ventricle 4. fourth ventricle ADDS more fluid 5.CSF ENTERS the subarachnoid space through three openings in the roof of the fourth ventricle 6.CSF CIRCULATE in the central canal of the spinal cord and in the subarachnoid space around the surface of the brain and spinal cord 7.CSF is REABSORBED into the blood through arachnoid villi -CSF is reabsorbed as rapidly as it is formed by the choroid plexuses, about 20 mL/hr (480 mL/day) -the rates of formation and reabsorption are the same, the pressure of CSF normally is constant

Ventricles

CSF-filled cavities within the brain 1. A lateral ventricle is located in each hemisphere of the cerebrum 2. Anteriorly, the lateral ventricles are separated by a thin membrane, the septum pellucidum 3. The third ventricle is a narrow cavity along the midline and between the right and left halves of the thalamus 4. The fourth ventricle lies between the brain stem and the cerebellum

5 lobes of the cerebrum

Frontal Parietal Temporal Occipital lobes

motor areas

Motor output from the cerebral cortex flows from the anterior part of each hemisphere

PONS Nerves

Trigeminal (V) nerves Abducens (VI) nerves Facial (VII) nerves Vestibulocochlear (VIII) nerves

Basal Ganglia

three nuclei or masses of gray matter -Lentiform Nucleus : 1. globus pallidus: Lateral to the thalamus 2. putamen: Closer to the cerebral cortex -3. caudate nucleus: Large head, smaller body -corpus striatum : All of the structures together

PROTECTIVE STRUCTURES

1. Bony vertebrae 2. Meninges

Ipsilateral reflex

-Nerve impulses enter the spinal cord on the same side,from which motor nerve impulses leave it -All monosynaptic reflexes are ipsilateral

Cerebrospinal fluid(csf) & Volume

-Cerebrospinal fluid (CSF) : *Clear, colorless liquid *Protects the brain and spinal cord from chemical and physical injuries *Carries oxygen, glucose, from the blood to neurons and neuroglia *Circulates through cavities in the brain, spinal cord, around the brain, and spinal cord in the subarachnoid space (between the arachnoid mater and pia mater) *volume of CSF is 80 to 150 mL (3 to 5 oz) in an adult *CSF contains glucose, proteins,some white blood cells, lactic acid, urea, cations (Nat, IC+, Ca', Mg2±), and anions (Cl- and HCO3t)

Formation of the CSF in the ventricles

-Choroid plexuses: The sites of CSF production are the networks of blood capillaries in the walls of the ventricles -The capillaries are covered by ependymal cells,Form cerebrospinal fluid from blood plasma -The ependymal cells are joined by tight junctions, materials entering cannot leak between these cells, They must pass through the ependymal cells -This barrier permits certain substances to enter the CSF but excludes others, protecting the brain and spinal cord from potentially harmful blood- borne substances.

medulla's white matter

-Sensory (ascending) tracts -Motor (descending) tracts -Extend between the spinal cord and other parts of the brain

diencephalon

-Extends from the brain stem to the cerebrum,Surrounds the third ventricle -Includes: 1. Thalamus 2. Hypothalamus 3. Epithalamus

olfactory ( I 1 ) nerves

-Sensory -Contains axons that conduct nerve impulses for olfaction, or the sense of smell - paired masses of gray matter called the olfactory bulbs

Midbrain Inferior colliculi/Substantia nigra

-Inferior colliculi: Part of the auditory pathway. Impulses from the receptors for hearing in the inner ear to the brain. *Reflex centers for the startle reflex *Sudden movements of the head, eyes, and trunk that occur when you are surprised by a loud noise -Substantia nigra: Large, darkly pigmented Neurons that release dopamine. *extending from the substantia nigra, help control subconscious muscle activities *Loss of these neurons is associated with Parkinson disease

Cerebrum Outer cerebral cortex

-Internal region of cerebral white matter -Gray matter nuclei deep within the white matter Is a region of gray matter that forms the outer rim of the cerebrum -only 2-4 mm thick, contains billions of neurons

trigeminal ( V 5) nerves

-Mixed cranial nerve -The trigeminal nerve: *Emerges from two roots on the ventrolateral surface of the pons. -The ophthalmic nerve: *Sensory axons from the skin over the upper eyelid -The maxillary nerve : *Sensory nerves for nose, upper teeth, upper lip, and lower eyelid -The mandibular nerve : *Sensory axons from the a tongue, cheek, lower teeth, and mucosa of the floor of the mouth -The sensory axons from the three branches enter the trigeminal ganglion and terminate in nuclei in the pons

vagus ( X 10 ) nerve

-Mixed cranial nerve -Sensory axons arise from the skin of the external ear -Proprioceptors in muscles of the neck and throat -Sensory axons come from baroreceptors in the arch of the aorta -Chemoreceptors in the aortic bodies near the arch of the aorta -Visceral sensory receptors in most organs of the thoracic and abdominal cavities -Autonomic motor neurons originate in nuclei of the medulla and end in the lungs and heart -Parasympathetic axons supply glands of the gastrointestinal (GI) tract and smooth muscle of the respiratory passageways, esophagus, stomach, gallbladder, small intestine, and most of the large intestine

Glossopharyngeal ( IX 9 ) nerve

-Mixed cranial nerve -Sensory axons arise from the taste buds -Somatic sensory receptors on the tongue -Proprioceptors in swallowing muscles -Baroreceptors in the carotid sinus, -Chemoreceptors near the carotid arteries

facial ( VII 7 ) nerve

-Mixed cranial nerve -sensory axons extend from the taste buds and end in the pons -Somatic motor neurons arise from the pons, pass through the temporal bone, and innervate facial, scalp, and neck muscles -Axons of parasympathetic neurons which secrete tears, and saliva-producing glands

hypoglossal ( XII 12 ) nerve

-Motor cranial nerve -motor axons originate in the medulla oblongata, and supply the muscles of the tongue *axons conduct nerve impulses for speech and swallowing

Accessory ( XI 11) nerve

-Motor cranial nerve -motor cranial nerve impulses to the sternocleidomastoid and trapezius muscles to coordinate head movements -Sensory axons in the accessory nerve that originate from proprioceptors in the muscles supplied by its motor neurons and end in the medulla oblongata

oculomotor ( III 3 ) nerves

-Motor cranial nerve -oculomotor nerve extends anteriorly. divides into superior and inferior branches. both pass through the superior orbital fissure into the orbit -control movements of the eyeball and upper eyelid

Abducens ( VI 6) nerves

-Motor cranial nerve -Originates from the abducens nucleus in the pons -Somatic motor axons extend to the lateral rectus muscle of the eyeball, cause lateral rotation

Basal Ganglia functions

-Receive input from the cerebral cortex -Output back to motor areas of the cerebral cortex -extensive connections with one another -help initiate and terminate movements of the body -Suppress unwanted movements and regulate muscle tone -Influence many aspects of cortical function, including sensory, limbic, cognitive, and linguistic functions -Parkinson disease and schizophrenia

Midbrain Red Nuclei/Reticular formation/Reticular activating system

-Red nuclei: Axons from cerebellum & cerebral cortex form synapses in the red nuclei. Help control some voluntary movements of the limbs -Reticular formation: Broad region where white matter and gray matter exhibit a netlike arrangement *extends from the upper part of the spinal cord Throughout the brain stem into the lower part of the diencephalon *Neurons within the reticular formation have ascending (sensory) and descending (motor) functions -Reticular activating system: Sensory axons that project to the cerebral cortex. *helps maintain consciousness and is active during awakening from sleep. *Descending functions are to help regulate posture and muscle tone

External Anatomy of the Spinal Cord

-Roughly cylindrical, flattened slightly anteriorly & posteriorly. -Extends from medulla oblongata to the second lumbar vertebra -length of the adult spinal cord ranges from 42 to 45 cm -Two conspicuous enlargements: 1.superior enlargement: cervical enlargement,4th cervical vertebra to the first thoracic vertebra,Nerves to and from the upper limbs 2.The inferior enlargement: lumbar enlargement,9th-12th thoracic vertebra,Nerves to and from the lower limbs .

cerebrum abilities

-Seat of intelligence -read, write, and speak -Make calculations and compose music -Remember the past, plan for the future -Imagine things that have never existed before

Cervical PLexus

-first four cervical nerves (C1—C4), with contributions from C5 -Supplies skin and muscles of the head, neck -superior part of the shoulders and chest -Supply motor fibers to the diaphragm -Phrenic Nerve innervates the Diaphragm

cerebellum

-Second only to the cerebrum in size -Occupies the inferior and posterior aspects of the cranial cavity -Highly folded surface, increases the surface area of outer gray matter cortex, allowing for a greater number of neurons -accounts for a tenth of the brain mass, contains nearly half of the neurons in the brain -anterior lobe and posterior lobe govern subconscious aspects of skeletal muscle movements

optic ( II 2) nerves

-Sensory -contains axons that conduct nerve impulses for vision -Posterior to the eyeball, the two optic nerves merge to form the optic chiasm -Posterior to the chiasm, the regrouped axons, some from each eye, form the optic tracts -Most axons in the optic tracts end in the lateral geniculate nucleus of the thalamus

vestibulocochlear ( VIII 8) nerve

-Sensory cranial nerve -Sensory axons arise from the inner ear and end in the medulla and pons

diencephalon epithalamus

-Small, superior and posterior to thalamus -pineal gland *^ size of a small pea -Secretes the hormone melatonin *Melatonin sets the body's biological clock *liberated during darkness than in light,thought to promote sleepiness

Spinal cord anatomy

-Vertebrae Column: *spine is inside vertebral canal of the vertebral column. *Provide sturdy shelter for enclosed spinal cord. *vertebral ligaments, meninges, and cerebrospinal fluid provide additional protection

2 connections to the cord

-a posterior root and an anterior root -posterior and anterior roots form a spinal nerve at the intervertebral foramen -Posterior root contains sensory axons -Anterior root contains motor axons -posterior root contains a posterior root ganglion in which cell bodies of sensory neurons are located

Midbrain

-a.k.a mesencephalon Extends from pons to diencephalon. about 1 in. long -Cerebral aqueduct: Passes through midbrain, connecting the third ventricle above, fourth ventricle below. -The anterior contains paired bundles of axons a.k.a cerebral peduncles *conduct nerve impulses from motor areas in the cerebral cortex to the spinal cord, pons, and medulla, respectively

Neural tube & 3 regions

-brain and spinal cord develop from ectoderm arranged in a tubular structure. anterior part of the neural tube expands, and create three regions -primary brain vesicles: *Prosencephalon (forebrain) Cerebrum, Thalamus, Hypothalamus,Epithalamus *Mesencephalon (midbrain) *Rhombencephalon (hindbrain) Pons, Cerebellum, Medulla Oblongata

tracts

-bundles extend long distances up or down the spinal cord In the CNS -bundles of axons in the PNS. 1.Sensory (ascending) tracts:conduct nerve impulses toward the brain 2.Motor (descending) tracts:carry nerve impulses from the brain -Sensory and motor tracts of the spinal cord are continuous with sensory and motor tracts in the brain.

3 meninges

-connective tissue covering around the spinal cord and brain -spinal meninges surround the spinal cord -cranial meninges which encircle the brain -cover the spinal nerve roots up to where they exit spinal column thru intervertebral formina -Denticulate ligaments :Thickenings of the pia mater, Protect spinal cord against sudden displacement that could result in shock. 1.Dura Mater : *outter layer of meninges *dense, irregular connective tissue 2.Arachnoid Mater : * middle meninx *Avascular covering called the arachnoid mater *Subdural Space:Between the dura mater &the arachnoid mater *Contains interstitial fluid 3.Pia Mate: *innermost meninx *thin transparent *Adheres to spinal cord and brain *Many blood vessels *Subarachnoid space: btwn arachnoid mater & the pia mater *contains cerebrospinal fluid that serves as a shock absorber

BRAIN BLOOD FLOW, BLOOD& BLOOD BRAIN BARRIER

-internal carotid and vertebral arteries - main blood flow path to the brain -internal jugular veins return blood from the head to the heart -brain consumes about 20% of the oxygen and glucose -When activity of neurons and neuroglia increases, blood flow to that area also increases -interruption in blood flow for 1 or 2 minutes impairs neuronal function -deprivation of oxygen for about 4 minutes causes permanent injury -glucose isn't stored in the brain, the supply of glucose also must be continuous -blood-brain barrier (BBB) protects brain cells from harmful substances and pathogens by preventing passage of many substances from blood into brain tissue -Crosses : Glucose, oxygen, carbon dioxide, alcohol, and most anesthetic agents -Very slowly: Creatinine, urea, and most ions -Do not pass : Proteins and most antibiotic drugs -Breakdown of the barrier: Trauma, certain toxins, and inflammation

diencephalon thalamus

-makes up 80% of the diencephalon -paired oval masses of gray matter organized into nuclei with interspersed tracts of white matter -Intermediate mass: bridge of gray matter joins the right and left halves of the thalamus in about 70% of human brains -Major relay station for most sensory impulses that reach the primary sensory areas of the cerebral cortex from the spinal cord and brain stem -transmits information from the cerebellum to the primary motor area of the cerebral cortex -Relays nerve impulses between different areas of the cerebrum and plays a role in the maintenance of consciousness

Sensory and Motor tracts

-name of a tract indicates its position in the white matter and where it begins and ends -Sensory receptors propagate up the spinal cord to the brain along two main routes on each side : *The spinothalamic tract *Posterior column -spinothalamic tract conveys nerve impulses for sensing pain, warmth, coolness, itching, and tickling -posterior column tracts convey nerve impulses for touch, pressure, vibration, and conscious proprioception -sensory information is integrated (processed) by interneurons in the spinal cord and brain -Responses to the integrative decisions are brought about by motor activities (muscular contractions and glandular secretions) -Motor output to skeletal muscles travels down the spinal cord in two types of descending pathways: direct and indirect -Direct Pathways : *convey nerve impulses that originate in the cerebral cortex and are destined to cause voluntary movements of skeletal muscles -Indirect pathways : * convey nerve impulses from the brain stem to cause automatic movements that regulate muscle tone, posture, and balance, and orientation of the head and body cerebral cortex, the outer part of the brain, plays a major role in controlling precise voluntary muscular movements

Medulla Sensory

-nuclei that are components of sensory pathways for: *Gustation Nucleus (taste): Part of gustatory pathway from the tongue to the brain receives gustatory input from the taste buds of the tongue *Audition (hearing): cochlear nuclei are part of the auditory pathway from the inner ear to the brain. receive auditory input from the inner ear *Equilibrium (balance): vestibular nuclei of the medulla and pons are components of the equilibrium pathway from the inner ear to the brain. receive sensory information associated with equilibrium

The brain stem

-part of brain between the S.Cord and the diencephalon. -three structures : 1. Medulla oblongata 2. Pons 3. Midbrain

distribution of Spinal nerves branches

-passing through intervertebral foramen -Divides into several branches or Rami , Ramus -posterior (dorsal) ramus : Deep muscles and skin of the posterior surface of the trunk -anterior (ventral) ramus :Muscles and structures of the upper and lower limbs Skin of the lateral and anterior surfaces of the trunk. -Axons from the anterior rami of spinal nerves, do not go directly to the body structures they supply -Plexus: form networks by joining with various numbers of axons from anterior rami of adjacent nerves *The cervical plexus *Brachial plexus *Lumbar plexus *Sacral plexus

Reflexes and Reflex arcs

-reflex is a fast, automatic, unplanned sequence of actions that occurs in response to a particular stimulus -Some reflexes are inborn, other reflexes are learned or acquired -Spinal Reflex: When integration takes place in the spinal cord gray matter, the knee jerk -Cranial Reflex: If integration occurs in the brain stem rather than the spinal cord -Somatic reflexes: Which involve contraction of skeletal muscles -Autonomic (visceral) reflexes: Not consciously perceived -Reflex arc (reflex circuit) : *Pathway followed by nerve impulses that produce a reflex

Internal Anatomy of the Spinal Cord

-regions of white matter that surround an inner core of gray matter -Two grooves penetrate the white matter of the spinal cord and divide it into right and left sides. 1.anterior median fissure: Wide groove on the anterior (ventral) side 2.posterior median sulcus: *Narrow furrow on the posterior (dorsal) side *gray matter of the spinal cord is shaped like the letter H 3.gray commissure: crossbar of the H 4.Central Canal: *center of the gray commissure *Extends the entire length of the spinal cord *Filled with cerebrospinal fluid 5.Anterior (ventral) white commissure: *Anterior to the gray commissure *Connects the white matter of the right and left sides of the spinal cord

Limbic Lobe

-rim of cerebral cortex on the medial surface of each hemisphere. It includes the : 1. Cingulate Gyrus: above the Corpus Callosum 2. Parahippocampal Gyrus: in the temporal lobe 3. Hippocampus : Is a portion of the parahippocampal gyms that extends into the floor of the lateral ventricle. *hippocampus, together with other parts of the cerebrum, functions in memory. 4.dentate gyrus: between the hippocampus and parahippocampal gyrus 5.amygdala: composed of several groups of neurons located close to the tail of the caudate nucleus 6.septal nuclei: located within the septal area formed by the regions under the corpus callosum and the paraterminal gyms (a cerebral gyrus) 7. The Mammillary bodies of the hypothalamus: Are two roundmasses close to the midline near the cerebral peduncles 8.anterior nucleus and the medial nucleus : Participate in limbic circuits 9.olfactory bulbs : are flattened bodies of the olfactory pathway that rest on the cribriform plate. 10. The fornix, stria terminalis, stria medullaris, medial forebrain bundle, and mammillothalamic tract: linked by bundles of interconnecting myelinated axons Called the "emotional brain" *Primary role in a range of emotions, including pleasure, pain, docility, affection, fear, anger, olfaction (smell) and memory -People with damage to certain limbic system structures forget recent events and cannot commit anything to memory

BraChial PLexus

-roots (anterior rami) of spinal nerves C5—C8 and T1 -provides almost the entire nerve supply of the shoulders and upper limbs -Five important nerves arise from the brachial plexus: 1. The axillary nerve supplies the deltoid and teres minor muscles 2. The musculocutaneous nerve supplies the ante-nor muscles of the arm 3. The radial nerve supplies the muscles on the posterior aspect of the arm and forearm 4. The median nerve supplies the muscles of the anterior forearm and some of the muscles of the hand 5. The ulnar nerve supplies the anteromedial muscles of the forearm and most of the muscles of the hand

Sacral PLexus

-roots (anterior rami) of spinal nerves L4-L5 and Sl-S4 Situated largely anterior to the sacrum -supplies the buttocks, perineum, and lower limbs. The largest nerve in the body—the sciatic nerve—arises from the sacral plexus -roots (anterior rami) of spinal nerves S4-S5 and the coccygeal nerves form a small coccygeal plexus, which supplies a small area of skin in the coccygeal region -sciatic nerve consists of two nerves: *Tibial and Common Fibular: Sends information to the hamstrings Tibial sends information to the gastrocnemius

lumbar PLexus

-roots (anterior rami) of spinal nerves LI—L4 -minimal intermingling of fibers in the lumbar plexus -gives rise to its peripheral nerves -Supplies the anterolateral abdominal wall, external genitals, and part of the lower limbs -Femoral Nerve:Largest nerve,Extensor muscles of the knee joint

specific association areas(

-somatosensory association area (areas 5 and 7) : *Posterior to and receives input from the primary somatosensory area, as well as from the thalamus and other parts of the brain *Determine the exact shape and texture of an object *Determine the orientation of one object with respect to another *Sense the relationship of one body part to another *Storage of memories of past somatic sensory experience -visual association area (areas 18 and 19) : *Located in the occipital lobe *Receives sensory impulses from the primary visual area and the thalamus *Relates present and past visual experiences and is essential for recognizing and evaluating what is seen -facial recognition area ( 20, 21, 37 ) *inferior temporal lobe * Receives nerve impulses from the visual association area *Stores information about faces, and it allows you to recognize people by their faces -auditory association area (area 22): *inferior and posterior to the primary auditory area in the temporal cortex *Allows you to recognize a particular sound as speech, music, or noise -orbitofrontal cortex ( 11 ) : *lateral part of the frontal lobe *Receives sensory impulses from the primary olfactory area * identify odors and to discriminate among different odors -Wernicke's area (area 22, 39,40) *Broad region in the left temporal and parietal lobes *Interprets the meaning of speech by recognizing spoken words *translate words into thoughts -common integrative area (areas 5, 7, 39, 40) *Bordered by somatosensory, visual, and auditory association areas *receives nerve impulses from these areas and from the primary gustatory area, primary olfactory area, the thalamus, and parts of the brain stem *integrates sensory interpretations from the association areas and impulses from other areas Allowing the formation of thoughts based on a variety of sensory inputs -prefrontal cortex (frontal association area) (9, 10, 11, and 12 ) *Extensive area in the anterior portion of the frontal lobe *Makeup of a person's personality, intellect, complex learning abilities, recall of information, initiative, judgment, foresight, reasoning, conscience, intuition, mood, planning for the future, and development of abstract ideas -premotor area (area 6) : *motor association area that is immediately anterior to the primary motor area *Deals with learned motor activities of a complex and sequential nature *generates nerve impulses that cause specific groups of muscles to contract in a specific sequence -The frontal eye field area (area 8) : *sometimes included in the premotor area *controls voluntary scanning movements of the eyes—like those you just used in reading this sentence

Spinal Cord Physiology

-two principal functions : *Nerve impulse propagation & Integration of information *white matter tracts are highways for nerve impulse propagation *Up : Sensory input travels along these tracts toward the brain *Down : Motor output travels from the brain along these tracts toward skeletal muscles and other effector tissues *gray matter of the spinal cord receives and integrates incoming and outgoing information

CSF contributes to homeostasis ( serve,provide,allows)

1. Mechanical protection: CSF SERVES as a shock-absorbing medium that protects the delicate tissues of the brain and spinal cord from jolts that would otherwise cause them to hit the bony walls of the cranial cavity and vertebral canal. The fluid also buoys the brain so that it "floats" in the cranial cavity 2. Chemical protection: CSF PROVIDES chemical environment for accurate neuronal signaling. Even slight changes in the ionic composition of CSF within the brain can seriously disrupt production of action potentials and postsynaptic potentials 3. Circulation: CSF ALLOWS exchange of nutrients and waste products between the blood and nervous tissue

5 functional components of

1. Muscle Spindles : Slight stretching of a muscle stimulates sensory receptors in the muscle. monitor changes in the length of the muscle 2. In response to being stretched,Muscle spindle generates one or more nerve impulses.Propagate along a somatic sensory neuron,Through the posterior root of the spinal nerve, Into the spinal cord 3. In the integrating center: sensory neuron makes an excitatory synapse withThereby activates a motor neuron in the anterior gray horn 4. Nerve impulses arise in the motor neuron and propagate along its axon. Extends from the spinal cord Into the anterior root,Through peripheral nerves to the stimulated muscle 5.Acetylcholine released by nerve impulses at the NMJs triggers one or more muscle action potentials in the stretched muscle (effector), and the muscle contracts. Thus, muscle stretch is followed by muscle contraction, which relieves the stretching.

5 functional components of reflex arcs

1. Sensory receptor : distal end of a sensory neuron (dendrite) responds to a specific stimulus by producing a graded potential called a generator (or receptor) potential. If a generator potential reaches the threshold level of depolarization it will trigger one or more nerve impulses in the sensory neuron. 2. Sensory neuron : The nerve impulses propagate from the sensory receptor along the axon of the sensory neuron to the axon terminals. which are located in the gray matter of the spinal cord or brain stem. 3. Integrating center/Monosynaptic reflex arc : One or more regions of gray matter within the CNS. simplest type of reflex, the integrating center is a single synapse between a sensory neuron and a motor neuron. -Monosynaptic reflex arc: reflex pathway having only one synapse in the CNS Polysynaptic reflex arc : Integrating center consists of one or more interneurons, which may relay impulses to other interneurons as well as to a motor neuron 4. Motor neuron : Impulses triggered by the integrating center propagate out of the CNS along a motor neuron to the part of the body that will respond 5.Effector: The part that responds to the motor nerve impulse is the effector Its action is called a reflex Somatic reflex: The effector is skeletal muscle Autonomic (visceral) reflex : The effector is smooth muscle, cardiac muscle, or a gland

sensory input and motor output to be process

1. Sensory receptors detect a sensory stimulus 2.neurons convey this sensory input in the form of nerve impulses.extend from sensory receptors into the spinal nerve and then into the posterior root 3.. From posterior root,neurons may proceed along three possible paths 4.neurons may extend into the white matter and ascend to the brain as part of a sensory tract 5.neurons enter the posterior gray horn.extend into the white matter ascend to the brain as part of a sensory tract 6.neurons enter the posterior gray horn.turn synapse with somatic motor neurons that are involved in spinal reflex pathways 7.Anterior gray horn: *Output from the spinal cord to skeletal muscles involves somatic motor neuron *Axons from higher brain centers form motor tracts that descend from the brain into the white matter of the spinal cord *Synapsing with interneurons that in turn synapse with somatic motor neurons 8.Motor output: from spinal cord to skeletal muscles involves somatic motor neurons of of AGH. *Axons from higher brain centers form motor tracts that descend from the brain into the white matter of the spinal cord. *synapse with somatic motor neurons by first synapsing with interneurons that in turn synapse with somatic motor neurons 9. Somatic motor: *neurons convey motor output as nerve impulses along their axons *pass through AGH & anterior root to enter the spinal nerve. *Axons of somatic motor neurons extend to skeletal muscles of the body. 10.Autonomic motor: *neurons convey motor output *pass through the lateral gray horn, anterior gray horn, and anterior root to enter the spinal nerve. 11.autonomic motor: *neurons from spinal cord synapse with another group of autonomic motor neurons located in the peripheral nervous system (PNS). *axons of this second group of autonomic motor neurons in turn synapse with cardiac muscle, smooth muscle, and glands.