Chapter 14-15

Created by nlfkjones6 

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Brain

-Center for registering sensations, correlating them with one another and with stored information, making decisions, and taking action
-Center for intellect, emotions, behavior and memory
-It also directs our behavior towards others.

Development of Brain

-The brain and spinal cord develop from ectoderm arranged in a tubular structure called the neural tube.
-The anterior part of the neural tube expands, and constrictions appear that create three regions called primary brain vesicles: prosencephalon(forebrain), mesencephalon(midbrain), and rhombencephalon(hindbrain).
-The walls of these brain regions develop into the nervous tissue of the brain, while the spaces in the tube remains as ventricles (spaces) w/in the brain.
-The mesencephalon gives rise to the midbrain and aqueduct of the midbrian(cerebal aqueduct).
-Both the prosencephalon and rhombencephalon develops in to the metencephalon and myelencephalon.
-The telencephalon develops into the cerebrum and lateral ventricles.
-The diencephalon forms the thalamus, hypothalamus, and epithalamus.
-The metencephalon becomes the pons, cerebullum, and upper forth ventricle.
-The myelencephalon foms the medulla oblongata and lower part of the fourth ventricle.
Look at TABLE 14.1

Brain development

-Three to four-week embryo: prosencephalon, mesencephalon and rhombencephalon.
-Five-week embryo: telencephalon (cerebrum), diencephalon (thalamus, hypothalamus and epithalamus), mesencephalon (midbrain), metencephalon (pons and cerebellum) and myelencephalon (medulla oblongata).

Major parts of brain

-Brain stem- continuation of the spinal cord; consists of the medulla oblongata, pons and midbrain.
-Cerebellum- posterior to the brain stem second largest part of the brain.
-Diencephalon- superior to the brain stem gives rise to thalamus, hypothalamus and epithalamus.
-Cerebrum- supported on the diencephalon and brain stem largest part of the brain.

Protective coverings of brain

-The cranium
-The cranial meninges: dura mater (outer), arachnoid mater (middle) and pia mater (inner).
-The cranial dura mater has 1 more extra layer than spinal dura mater.

Extension of the dura mater

-Three extensions of the dura mater separate parts of the brain:
a. Falx ("falks") cerebri separate the two hemispheres of the cerebellum.
b. Falx cerebelli separate the two hemispheres.
c. Tentorium cerebelli separate the cerebrum from the cerebellum.

Brain Blood Flow

-Blood flows mainly via the internal carotid and vertebral arties.
Internal jugular veins return blood from head to the heart
-Brain = ~ 2% of body weight; utilizes ~20% of oxygen used by body; one of most metabolically active organs of the body
-Internal carotid and vertebral arteries/ Internal jugular veins carry blood to/from the brain.
-Any interruption of oxygen supply harmful to brain cells
-Carbohydrate storage limited; reduction in supply of glucose -----> paralysis, epilepsy, mental retardation, death

Blood-brain barrier

- protects brain from harmful substances and pathogens by preventing passage of many substances from blood into brain tissue.
- consist of tight junctions tha seal endothelial cells of brain capillaries.
-thick basement membrane around the capillaries.
-lipid-soluble substances, such as oxygen, carbon dioxide, alcohol, and most anesthetic agents easily cross the blood-brain barrier.
-trauma, certain toxins, and inflammation can cause a breakdown of the BBB.

Cerebrospinal fluid

-Clear, colorless fluid protects brain and spinal
-Ventricles- cavities within the brain that are filled with cerebrospinal fluid
-Circulates through cavities in the brain (ventricles) and the spinal cord (central canal) and also in the subarachnoid space.
-Lateral ventricles- located in each hemisphere of the cerebrum.
-Septum pellicidum- Thin membrane that anteriorly separate lateral ventricles.
-Third ventricle- is a narrow cavity along the midline superior to the hypothalamus and btwn the right and left halves of the thalamus.
-4th ventricle- lies btwn the brain stem and the cerebellum.

function of the cerebrospinal fluid

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 cranal. The fluid buoys the brain so that it "floats" in the cranial cavity.
2. Chemical protection- CSF provides an optimal chemical environment 4 accurate neuronal signaling.
3. Circulation- CSF allows exchange of nutrients and waste products btwn the blood and nervous tissue.

Formation of CSF

-Choroid plexuses- networks of capillaries in the walls of the ventricles. Plasma is drawn from the choroid plexuses through ependymal cells that line the ventricles to produce CSF. Material cannot leak between the ependymal cells, creating a Blood Brain Barrier which permits certain substances to enter the CSF, but excludes others, protecting the brain from harmful elements.

Choroid plexuses

sites of production ...CSF originates from blood plasma -- must pass through ependymal cells

Absorption of CSF through ventricles

CSF is absorbed into the blood through arachnoid villi that extend into superior saggital blood sinus @ same rate as produced in the choroid plexuses

Ventricles

CSF-filled cavities within the brain.
Lateral ventricles: cerebral hemispheres.
Third ventricle: diencephalon.
Cerebral aqueduct: midbrain.
Fourth ventricle: brain stem and the cerebellum.

Circulation of CSF

CSF from the lateral ventricles → interventricular foramina → third ventricle → cerebral aqueduct → fourth ventricle → subarachnoid space or central canal.
-CSF is reabsorbed into the blood by arachnoid villi.
Look at FIGURE 14.4 (d)

Parts of the brain

1. Brain Stem - between spinal cord and diencephalon -- Interconnections, center for regulation of many visceral activities
Medulla Oblongata - Myelencephalon
Pons - Metencephalon
Midbrain - Mesencephalon
2. Cerebellum - Coordination of voluntary muscular movements - Metencephalon
3. Diencephalon - Relay center; integrates with endocrine
4. Cerebrum - Sensory & motor; memory and reasoning

Medulla oblongata

Pyramids- Bulges on the anterior aspect of the medulla. Formed by the large corticospinal tracts that pass from the cerebrum to the spinal cord.
-A common site for decussation of ascending and descending tracts. 90% of axons cross to opposite side
-Vital centers:
-Cardiovascular center- regulates the rate and force of the are heartbeat and the diameter of blood vessels
-Respiratory center- adjusts the rhythm of breathing
-Also includes centers for vomiting, swallowing, sneezing, coughing and hiccupping.
-Houses five pairs of cranial nerves, VIII-XII.
-Portion of the ventricle found here is the fourth ventricle.

Medulla Oblongata

Regulation of
Heart Rate Respiratory Rate
Vasoconstriction Swallowing
Coughing Vomiting
Sneezing Hiccoughing

Pons

-A bridge that connects different parts of brain together --
-Several Nuclei relay information on:
voluntary movements, equilibrium, respiration
-Nuclei of cranial nerves V, VI, VII, VIII
-Sensory Tracts & Motor Tracts
-The pons contains nuclei that relay signals from the cerebrum to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.[3]
-Within the pons is the pneumotaxic center, a nucleus in the pons that regulates the change from inspiration to expiration.

Midbrain

-Extends from the pons to the diencephalon.
-Part of the ventricle found here- cerebral aqueduct.
-Cerebral peduncles: axon motor tracts from cerebrum to pons, medulla and spinal cord.
-Tectum- situated posteriorly and contains four rounded elevations: two superior ones called superior colliculi and two inferior ones called inferior colliculi.

Tectum (Corpora Quadrigemina)

-Two pair of rounded elevations
-Superior Collicului
*Reflex center for visual activities '
*Coordinate eye movements for tracking moving objects
-Inferior Colliculi
*Relay impulses from inner ear to brain
*Startle reflex

Midbrain (cont)

-Substantia nigra: large area with dark pigments. Help control subconscious muscle activities. Loss of neurons here is associated with Parkinson disease.
-Red nucleus: Help control voluntary movements of the limbs.
-Contains cranial nerves III-IV.

Cerebellum

-Second largest part of the brain
-1/10th brain mass; ~1/2 # of brain neurons
-The central constricted area is the vermis.
-Lateral "wings" -- cerebellar hemispheres
-The anterior and posterior hemispheric lobes control subconscious aspects of skeletal movement.
-The flocculonodular lobe on the inferior side contributes to the equilibrium and balance.

Cerebellum (cont.)

-Cerebellar cortex- superficial layer of cerebellum consist of gray matter in the form of parallel folds called folia.
-Arbor vitae- tracts of white matter.
-Cerebellar nuclei- region of gray matter that give rise to axons carrying impulses from the cerebullum to the other brain centers.
-Cerebellar peduncles- three pairs: superior, middle and inferior. Attach cerebellum to the brain stem.
-Superior cerebellar peduncles- contains axon that extend from the cerebellum to the red nuclei of the midbrain and to several nuclei of the thalamus
-The middle cerebellar peduncles are the largest; their axons carry commands for voluntary movements from the pontine nuclei (which receives input from motor areas of the cerebral cortex) into the cerebullum.
-The inferior cerebellar peduncles consists of (1). Axons of the spinocerebellar tracts that carry sensory information in to the cerebellum from proprioceptors in the trunk and limbs. (2). Axons from the vestibular apparatus of the inner ear and from the vestibular nuclei of the medulla and pons that carry sensory info to the cerebullum from proprioceptors in the head. (3). Axons from the inferior olivary nucleus of the medulla that enter the cerebellum and regulate activity of cerebellar neurons. (4), Axons that extend from the cerebellum to the vestibular nuclei of the medulla and pons. (5). Axons that extend from the cerebellum to the reticular formation.
-Functions- smooth and coordinates contractions of skeletal muscles, regulate posture and balance. Due to reciprocal connections btwn this and cerebral cortex, may have a role in cognition and language processing.

Diencephalon

-Extends from brain stem to the cerebrum, surrounds the 3rd ventricle.
-Include thalamus, hypothalamus, and epithalamus.

Thalamus

-Intermediate mass
-3cm makes up 80% of the diencephalon consist of paired oval masses of gray matter organized into nuclei with interspersed tracts of white matter.
-Intermediate mass( interthalamic adhesion)- joins the right and left halves of the thalamus in about 70% of human beings.
Internal medullary lamina- Vertical Y-shaped sheet of white matter that divides the gray matter of the right and left sides of the thalamus.
-Internal capsule- a thick band of white matter lateral to the thalamus in which axons that connect to the thalamus and cerebral cortex pass through.
-Several nuclei:
-Major relay station for most sensory impulses that reach the primary sensory areas, contributes to motor functions by transmitting info from the cerebellum and basal ganglion to the primary motor area of the cerebral cortex, and plays a role in the maintenance of consciousness.
-Central relay for sensory impulses (except smell via olfactory nerve) to Cerebrum
-Awareness of pain, touch, temperature

Hypothalamus

-Inferior to the thalamus and composed of a dozen or so nuclei in 4 major regions
(1). Mammilary Region- consists of mammillary bodies (relay stations 4 reflexes related to sense of smell) and the posterior hypothalmaic nuclei.
(2). Tuberal Region- widest part of the hypothalamus, consist of the dorsomedial nucleus, ventromedial nucleus, and arcuate nucleus. Infundibulum-connects pituitary gland 2 hypothalamus (stalklike shape) median eminence- encircles the infundibulum
(3). Supraoptic region- superior to optic chasim (cross section of nerves) contains the paraventricular nucleus, supraoptic nucleus, anterior hypothalamic nucleus, and suprachiasmatic nucleus.
(4). Preoptic region- anterior to the supraoptic region, participates with the hypothalamus in regulating certain autonomic activities. Contains medial and lateral preoptic nuclei.

Functions of hypothalamus

-Control of the ANS.
-Production of hormones
-The median eminence is of great physiological importance, as it is integral to the hypophyseal portal system, which connects the hypothalamus with the anterior lobe of the pituitary gland. It is in this structure that the secretions of the hypothalamus (releasing and inhibiting regulatory hormones) collect before entering the portal system.
-Regulation of emotional and behavioral patterns, eating and drinking, body temperature, and circadian rhythms.

Epithalamus and Circumventrical organs

-Small region superior to the thalamus.
-Consists of pineal gland which secretes a hormone called melatonin and habenular nuclei.
-Melatonin induces sleep.
-Circumventricular Organs: Hypothalamus, pineal, pituitary: Lack blood-brain barrier, can monitor chemical changes in blood, coordinate homeostatic activities of endocrine/nervous such as blood pressure, fluid balance,hunger, and thrist; site of HIV entrance

Cerebum

-"seat of intelligence"
-provides us with the ability to read, write, and speak; make calculations; remember the past, plan for the future, and imagine things.
- consist of an outer cerebral cortex, an internal region of cerebral white matter, and gray matter nuclei deep w/in the the white matter.

Cerebum (cont)

-Cerebral Cortex-region gray matter that forms the outer rim of the cerebrum; 2-4 mm thick;
-Contains billions of neurons
-Gyri- Folds or convolutions
-Sulci- Shallow grooves between folds
-Fissures - Deepest grooves between folds
-Longitudinal fissure- most prominent fissure separates cerebrum into right and left halves called cerebral hemispheres
- Corpus Callosum - broad band of white matter containing axons that extend btwn hemispheres to connect them internally.

Lobes of the Cerebrum

-Each hemisphere can be futher divided into 4 lobes.
-Four lobes: frontal lobe (higher mental functions), parietal and temporal lobe (hear, smell) and occipital lobe (vision).
-Central sulcus- separates the frontal and parietal lobes.
-Precentral gyrus- primary motor area.
-Postcentral gyrus- primary somatosensory area.
-Lateral cerebral sulcus- separate the frontal bone from the temporal bone.
-Parieto-occipital sulcus- separates the parietal lobe from the occipital lobe.
-A 5th part called the insula cannot be seen from the surface of the brain b/c it lies w/in the lateral cerebral sulcus 2 deep to the parietal, frontal, and temporal lobes.

Functions fo Frontal lobe

-Functions of the frontal lobes involve the ability to recognize future consequences resulting from current actions, to choose between good and bad actions (or better and best), override and suppress unacceptable social responses, and determine similarities and differences between things or events. Therefore, it is involved in higher mental functions.
-The frontal lobes also play an important part in retaining longer term memories which are not task-based. These are often memories associated with emotions derived from input from the brain's limbic system. The frontal lobe modifies those emotions to generally fit socially acceptable norms.

Cerebral white matter

- Consist primarily of myelinated axons in 3 types of tracks
(1). Association tracts- connect between gyri in same hemisphere
(2). Commissural tracts- connect gyri in one hemisphere w/ like gyrus in opposite side. 3 important groups of commissural tracts.
a. Corpus callosum- largest fiber bundle of brain 300 million fibers
b. Anterior commissure
c. posterior commissure
(3). Projection tracts- form ascending & descending
tracts to/from the cerebrum to lower parts of CNS or
Lower parts of brain/spinal cord to cerebrum

Basal Ganglia

-Three nuclei deep within each cerebral hemisphere make up basal ganglia.
-They are globus pallidus (closer to thalamus), putamen (closer to cerebrum) together form the lentiform nucleus,caudate nucleus (larger head smaller tail). Lentiform plus caudate=corpus striatum.
-Help initiate and terminate movements, suppress unwanted movements and regulate muscle tone.

Limbic System

-A ring of structures on the inner border of the cerebrum and floor of the diencephalon.
-Includes cingulate gyrus, hippocampus, dentate gyrus, amygdala, mammillary bodies, thalamus, and the olfactory bulb.
-"emotional brain" as it governs emotional aspects of behavior.
Also involved in olfaction and memory.

Organization of Cerebral Cortex: Sensory Areas

-Precentral gyrus - Primary motor area
-Postcentral gyrus.Primary somatosensory
-Primary gustatory area- base of the postcentral gyrus
-Primary visual area- occipital lobe.
-Primary auditory area- temporal lobe.
-Primary olfactory area- temporal lobe.

Functions of Sensory Areas

-Somatosensory Association areas 5, 7 allows you to recognize an object by simply touching it.

-Prefrontal cortex- anterior portion of the frontal lobe.— personality, intellect, complex learning, recall, judgment, foresight, reasoning, conscience, abstract ideas

Primary Somatosensory association

-Primary visual area 17 receives visual information, involved in visual perception
-Primary auditory area 41,42, receives information for sound , auditory perception
-Primary gustatory area 43, information for taste and taste discrimination
-Primary olfactory area 28 medial temporal lobe receives info on smell and involved in olfactory perception

Speech areas of cerebrum

-Broca's speech (area 44 and 45) left frontal lobe translates thoughts into speech; coordinates with motor areas to enable speech
-Wernicke's (area 22 poss. 39, 40) of left temporal/parietal lobes recognizes spoken words; arrange words in coherent fashion
-Corresponding areas in right hemisphere adds emotion to speech

Association areas

-Visual association area- 18,19 occipital lobe, recognizes and evaluates what is seen.
-Auditory association area- 22 temporal lobe allows you to recognize a particular sound as speech, music, or noise.

Motor Areas

-Primary motor area 4
controls voluntary muscles in specific areas (for fingers >toes)
-Premotor area 6 serves as a memory bank for learned motor activities that are complex and sequential

Hemispheric Lateralization

TABLE 14.3

Brain Waves

-Electroencephalogram: Recording of the electrical activity within the brain. Useful for various reasons such as simple changes, diagnosing, or determining "life".
-Alpha waves 8-13 Hz
present: awake/resting w/eyes closed; absent: during sleep
-Beta waves 14-30 Hz appear when nervous system is active
Brain active w/sensory input & mental activity
-Theta waves 4-7 Hz
Occur in individuals experiencing emotional stress/some brain disorders
-Delta waves 1-5 Hz
Deep sleep in adults/awake infants
When produced by awake adults indicate brain damage.

Cranial Nerves

-Named so b/c they arise from the brain inside the cranial cavity and pass through various foramina in the bones of the cranium.
- part of the Peripheral Nervous System
-# indicate order from anterior to posterior; name indicates function or distribution
-3 cranial nerves carry axons of sensory neurons thus called sensory nerves (I, II, VIII). Olfactory (I), Optic (II), and Vestibulocochlear (VIII)
- 5 cranial nerves contain only motor neurons they leave the brain stem and are called motor nerves (III, IV, VI, XI, XII). Oculomotor (III), Trochlear (IV), Abducens (VI), Accessory (XI), and Hypoglossal (XII)
- 4 cranial nerves contain axons of both sensory and mixed neurons called mixed nerves (V, VII, IX, X). Trigeminal (V), Facial (VII), Glossopharyngeal (IX), and Vagus (X).

Olfactory Nerve

- Nerve (I)
-entirely sensory
-sense of Smell
-Olfactory bulb- olfactory nerves end in the brain in paired masses of gray matter here.
- Olfactory tracts- axons of neurons that have synapsed within the olfactory bulb.
-emerge from nose

Optic nerve

-Nerve (II)
-Sensory nerve.
-originates in eyes
-Ganglion cells in the retina of each eye join to form an optic nerve.
-Nerve of vision
-optic chiasm- crossover
-optic tract regrouped axon from each eye

Oculomotor Nerve

-Nerve (III)
-Motor cranial nerve.
-Originates in the midbrain.
-Supply extrinsic eye muscles to control movements of the eyeball and upper eyelid.
-Proprioceptive sensory axons perceive muscle movements

Trochlear Nerve

-Nerve (IV)
-Motor cranial nerve.
-Smallest of the 12 cranial nerves.
-Origin: midbrain.
-Controls movement of the eyeball via
-Superior Oblique

Trigeminal Nerve

-Nerve (V)
-Largest cranial nerve.
-Mixed nerve.
-Three branches: opthalmic, maxillary and mandibular. Deal with sensation of touch, pain and temperature.
-Motor axons supply muscles of mastication.

Abducens Nerver

-Nerve (VI)
-Motor cranial nerve.
-Originates from the pons.
-Cause abduction of the eyeball (lateral rotation).
-Lateral Rectus

Facial Nerves

-Nerve (VII)
-Mixed cranial nerve.
-Sensory portion extends from the taste buds of the anterior two-thirds of the tongue through the geniculate ganglion-cluster of cell bodies of sensory neurons that lie beside the facial nerve and end in the pons.
-Motor portion arises from the pons and deal with facial expression.

Vestibulocohlear Nerve

-Nerve (VIII)
-Sensory cranial nerve.
-Originates in the inner ear.
-Vestibular branch carries impulses for equilibrium.
-Cochlear branch carries impulses for hearing.

Glossopharyngeal Nerve

-Nerve (IX)
-Mixed cranial nerve.
-Sensory axons carry signals from the taste buds of the posterior one-third of the tongue.
-Motor neurons arise from the medulla and deal with the release of saliva.

Vagus Nerve

-Nerve (X)
-Mixed cranial nerve.
-Distributed from the head and neck into the thorax and abdomen.
-Sensory neurons deal with a variety of sensations such as proprioception, and stretching.
-Motor neurons arise from the medulla and supply muscles of the pharynx, larynx, and soft palate that are involved in swallowing and vocalization.

Accessory Nerve (XI)

-Nerve (XI)
Motor cranial nerve.
-Divided into cranial accessory and spinal accessory nerves.
Supplies sternocleidomastoid and trapezius muscles to coordinate head movements.

Hypoglossal Nerve

Nerve (XII)
-Motor cranial nerve.
-Conduct nerve impulses for speech and swallowing.

Autonomic Nervous System

-Contributes to Homeostasis by responding to Subconscious sensations and
-Exciting or Inhibiting
-Smooth Muscle
-Cardiac Muscle
-Glands

Interoceptors

-Associated with Interoceptors
-Sensory receptors located in blood vessels, visceral organs, muscles and nervous system
-Monitor conditions of the "internal" environment
-Chemoreceptors --> blood CO2
-Mechanoreceptors -->stretch in walls of organs, vessels
-Not normally consciously perceived
-Intense activation --> conscious perceptions
-Damaged viscera, chest pain due to inadequate flow of blood to heart
-Somatic pain can alter some autonomci activities

Comparsion of Somatic and Autonomic

TABLE 15.3

Anatomy of ANS

Preganglionic neuron
- Myelinated
Postganglionic neuron
- Unmyelinated

Two divisions:
Sympathetic - Thoracolumbar outflow
Parasympathetic - Craniosacral outflow

Sympathetic division

-Thoracolumbar division-
-Preganglionic neurons cell bodies in lateral horns of gray matter in
-12 thoracic segments (T1-T12), and
-2-3 lumbar levels of the spinal cord (L1-L2).
-THORACOLUMBAR OUTFLOW

Parasympathetic division

-Craniosacral Division
-Preganglion Neuron Cell Bodies
-Nuclei of Cranial Nerves III, VII, IX, X
-Lateral Gray Horn
-2nd to 4th Sacral Segments of spinal cord

-CRANIOSACRAL OUTFLOW

Sympathetic ganglia

-Sympathetic ganglia:
1.) Sympathetic trunk (vertebral chain) ganglia. Vertical row on each side
Neck - Superior, Middle, Inferior Cervical Gang
Remaining trunk ganglia w/o individual names
Postganglionic primarily innervate organs above the diaphragm
Sympathetic trunk near spinal cord
Most Preganglionic short, Postganglionic long
- 2.) Prevertebral (collateral) ganglia:
Anterior to vert. column, near large abdominal
- arteries
- celiac- largest autonomic plexus surrounds celiac trunk
-superior mesenteric- supplies small intestine and proximal colon
-inferior mesenteric,
-aorticorenal and
- renal.

Postganglionic Neurons in the Sympathetic Division

-An axon may synapse with postganglionic neurons in the ganglion it first reaches or
-up/down Sympathetic chains or
-An axon may continue, without synapsing, through the sympathetic trunk ganglion to end at a prevertebral ganglion and synapse with postganglionic neurons there or
-An axon may pass through the sympathetic trunk ganglion and a prevertebral ganglion and then to the adrenal medulla.

Sympathetic Division

-A single sympathetic preganglionic fiber has many axon collaterals and may synapse with 20 or more postganglionic neurons.

-The postganglionic axons typically terminate in several visceral effectors and therefore the effects of sympathetic stimulation are more widespread than the effects of parasympathetic stimulation.

Autonomic Plexuses

-A network of sympathetic and parasympathetic axons.
-Cardiac plexus- heart.
-Pulmonary plexus- the bronchial tree.
-Celiac plexus- largest. Supplies the stomach, spleen, pancreas, liver, gallbladder, and adrenal medullae.
-Superior mesenteric plexus- small intestine and proximal colon.
-Inferior mesenteric plexus- distal colon and rectum.
-Hypogastric plexus- urinary bladder and genital organs.
-Renal plexus- kidneys and ureters.

Pathway from Spinal Cord to Sympathetic Trunk Ganglia

-Preganglionic axons → anterior root of a spinal nerve → white ramus → sympathetic trunk ganglion.
-White rami communicantes: structures containing sympathetic preganglionic axons that connect the anterior ramus of the spinal nerve with the ganglia of the sympathetic trunk.

Organization of Sympathetic Trunk Ganglia

-Sympathetic trunk ganglia: 3 cervical, 11 or 12 thoracic, 4 or 5 lumbar, 4 or 5 sacral and 1 coccygeal.
-Postganglionic neurons from the superior cervical region-head and heart.middle cervical ganglion and the inferior cervical ganglion-heart.
-Thoracic sympathetic trunk- heart, lungs, and bronchi.

Pathways from Sympathetic Trunk Ganglia to Visceral Effectors

Axons leave the sympathetic trunk in 4 possible ways:
- spinal nerves
- cephalic periarterial nerves
- sympathetic nerves
- splanchnic nerves

Spinal Nerves

-Gray ramus: Axons of some postganglionic neurons leave the sympathetic trunk by entering a short pathway called a gray ramus and merge with the anterior ramus of a spinal nerve.
-Gray rami communicantes: structures containing sympathetic postganglionic axons that connect the ganglia of the sympathetic trunk to spinal nerves.

Cephalic Periarterial Nerves

-Some sympathetic preganglionic neurons that enter the sympathetic trunk ascend to the superior cervical ganglion where they synapse with postganglionic neurons. Some of these leave the sympathetic trunk by forming cephalic periarterial nerves.
-Serve visceral effectors in the skin of the face and head.

Sympathetic nerve

-Some axons of the postganglionic neurons leave the trunk by forming sympathetic nerves.
-Innervate the heart and lungs.

Splanchnic Nerve

-Some sympathetic preganglionic axons pass through the sympathetic trunk without terminating in it. Beyond the trunk they form nerves called splanchnic nerves which extend to prevertebral ganglia.
-T5-T9 or T10- Greater splanchnic nerve.
-T10-T11- Lesser splanchnic nerve.
-L1-L4- Lumbar splanchnic nerve.

Splanchnic Nerve 2 adrenal medulla

-Some sympathetic preganglionic axons pass, without synapsing, through the sympathetic trunk, greater splanchnic nerves and celiac ganglion into the adrenal medulla (modified sympathetic ganglia).
-Release hormones into blood- 80% epinephrine, 20% norepinephrine.

Cranial Parasympathetic Outflow

-The cranial outflow has four pairs of ganglia and are associated with the vagus nerve.
-Ciliary ganglia- lie lateral 2 optic nerve. Preganglionic axons pass with the oculomotor nerve to the ciliary ganglia. Postganglionic axons from the ganglia innervate smooth muscle fibers in the eyeballs
-Pterygopalatine ganglia-receive preganglionic axons from facial nerves and send postganglionic axons to nasal mucosa, palate, pharynx, and lacrimal glands.
-Submandibular ganglia-found near ducts of submandibular salivary glands. Receive Preganglionic from facial nerves. Send postganglionic axons 2 submandibular and sublingual salivary glands
-Otic ganglia- inferior at foramen ovale. Receive preganglionic axons from glossopharyngeal nerves and send postganglionic axons 2 parotid salivary glands
Vagus nerve carries nearly 80% of the total craniosacral flow.

Parasympathetic Division

-Craniosacral division:
-Preganglionic neurons originate
from III, VII, IX and X nuclei
and sacral spinal nerves S2-S4.
-Parasympathetic ganglia  terminal ganglia.
-Presynaptic neuron usually synapses with 4-5 postsynaptic neurons all of which supply a single visceral effector.

Sacral Parasympathetic Outflow

-Consists of S2-S4.
-Pelvic splanchnic nerves

Parasympathetic Ganglia

-Ciliary ganglia III  postganglionic to smooth muscle fibers in eyeball
-Pterygopalatine ganglia VII --> nasal mucosa, palate, pharynx, lacrimal glands
-Submandibular ganglia VII --->submandibular/sublingual salavary glands
-Otic ganglia IX -->parotid salavary glands

Parasympathetic Vagus X Nerve

-Carry 80% of craniosacral outflow X ---> many terminal ganglia
-Thorax -- Heart, Airways of Lungs
-Abdomen - liver, gallbladder, stomach, pancreas small intestine, part of colon

Parasympathetic Sacral Outflow

-Anterior roots of S2-S4
- form pelvic splanchnic nerves
-Postganglionic axons innervate
-Smooth muscle and glands of
-Walls of colon
-Ureters
-Urinary bladder
-Reproductive organs

Cholinergic Neurons

-Cholinergic neurons → acetylcholine (ACh).
-Cholinergic neurons include-
1.All sympathetic and parasympathetic preganglionic neurons.
2.Sympathetic postganglionic neurons that innervate most sweat glands.
3. All parasympathetic postganglionic neurons

Cholinergic Receptors

-Cholinergic receptors bind acetylcholine.
-Nicotinic receptors in cell membranes of dendrites and cell bodies of sympathetic and parasympathetic postganglionic neurons
-Muscarinic receptors membranes of effectors Smooth, cardiac muscle, and glands innervated by postsynaptic parasympathetic
Sweat glands receive cholinergic sympathetic postganglionic innervation

Adrenergic Neurons and Receptors

-Release norepinephrine (noradrenalin).
-Most sympathetic postganglionic neurons are adrenergic.
Two types of receptors:
Alpha receptors- Beta receptors- β
alpha1 and β1 generally excitatory
alpha2 and β2 generally inhibitory
β3 found only in brown fat --->thermogenesis

Physiology of the ANS

-Autonomic tone- a balance between the sympathetic and parasympathetic activity.
-Regulated by the hypothalamus.

Sympathetic Responses

-Stress ↑ sympathetic system ↑ fight-or-flight response.
-↑ production of ATP.
-Dilation of the pupils.
-↑ heart rate and blood pressure.
-Dilation of the airways.
-Constriction of blood vessels that supply the kidneys and gastrointestinal tract.
-↑ blood supply to the skeletal muscles, cardiac muscle, liver and adipose tissue
-↑ glycogenolysis ↑ blood glucose.
-↑ lipolysis

Sympathetic Stimulation

-Effects last longer than parasympathetic
-Postganglionic axons diverge activate many tissues
-Acethylcholinesteras quickly inactivates Ach, but Norepinephrine lingers
-Medulla hormone secretions prolong adrenalin effects

Parasympathetic Responses

-Rest-and-digest response.
-Conserve and restore body energy.
-↑ digestive and urinary function.
-↓ body functions that support physical activity.

Integration and Control of Autonomic Functions

-Direct innervation- brain stem and spinal cord.
-Hypothalamus is the major control and integration center of the ANS.
-It receives input from the limbic system.

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