Nervous System (Systems Anatomy) PDF

Nervous System Systems Anatomy 1 Neural Tissue Spinal Cord 2 KINE 1P90 SP2023 1  Nervous System Characteristics Controls and adjusts the...

Nervous System Systems Anatomy 1 Neural Tissue Spinal Cord 2 KINE 1P90 SP2023 1  Nervous System Characteristics Controls and adjusts the activity of the body Provides swift but brief responses The nervous system includes: Central Nervous System (CNS) brain and the spinal cord Peripheral Nervous System (PNS) Associated with the tissue outside the CNS Afferent and efferent divisions 3 CENTRAL NERVOUS SYSTEM Brain Central Nervous System (CNS) Spinal cord – Responsible for integrating, processing, and coordinating sensory input & motor output – the seat of intelligence, memory, learning, and emotion Peripheral Nervous System (PNS) – Provides sensory information to the CNS & PERIPHERAL NERVOUS SYSTEM carries motor commands away from the CNS Peripheral nerves Afferent division: Brings sensory information to the CNS Efferent division: Carries motor commands to muscles and glands Afferent arrives. Efferent exits. Figure 13.1 4 KINE 1P90 SP2023 2  Overview of the Nervous System CENTRAL NERVOUS SYSTEM Information (brain and spinal cord) processing Sensory information Motor commands afferent division efferent division PERIPHERAL NERVOUS SYSTEM Somatic nervous Autonomic system nervous system Parasympathetic Sympathetic division division Special sensory Visceral sensory Somatic receptors receptors sensory Smooth muscle receptors Skeletal Cardiac muscle muscle Glands RECEPTORS EFFECTORS Figure 13.2 5 Cellular Organization in Neural Tissue Specialized to conduct electrical signals through the body Two cell types: 1. Neurons responsible for the transfer and processing of information in the nervous system Consist of a soma, axon, and dendrites 2. Neuroglia Supporting cells, protect the neuron 6 KINE 1P90 SP2023 3  1. Neuron Structure Figure 13.4 7 Structural Classification of Neurons Figure 13.11 8 KINE 1P90 SP2023 4  Synapses Site of intercellular communication Figure 13.10b 9 STRUCTURE OF A SYNAPSE 10 KINE 1P90 SP2023 5  NEURONAL ORGANIZATION CIRCUITS Figure 13.15 11 2. Neuroglia Functions: Provide the framework for the neural tissue Maintain the intercellular environment Act as phagocytes Have the ability to reproduce 12 KINE 1P90 SP2023 6  Neuroglia Cell Types Neuroglia Cells of the CNS Astrocytes Oligodendrocytes Microglia Ependymal cells Neuroglia Cells of the PNS Satellite cells Schwann cells 13 Classification of Neuroglia Neuroglia Peripheral Nervous System Central Nervous System Oligodendrocytes Satellite Schwann Ependymal Cells cells Astrocytes Microglia cells Surround neuron cell Surround all axons in Myelinate CNS Maintain blood-brain barrier; Remove cell Line ventricles bodies in ganglia; PNS; responsible for axons; provide provide structural support; debris, wastes, (brain) and central regulate O2, CO2, myelination of structural regulate ion, nutrient, and and pathogens canal (spinal cord); nutrient, and peripheral axons; framework dissolved-gas concentra- by phagocytosis assist in producing, neurotransmitter levels participate in repair tions; absorb and recycle circulating, and around neurons in process after injury neurotransmitters; form scar monitoring ganglia tissue after injury cerebrospinal fluid Figure 13.5 14 KINE 1P90 SP2023 7  Neuroglia Astrocytes Have a large number of cytoplasmic processes Control the chemical content of the interstitial environment Maintain the blood–brain barrier Isolate the neurons from general circulation Scaffolding – structural framework Repair damaged neurons Guide neurogenesis 15 Blood Brain Barrier: tight junctions and astrocytes Similar to Fig 5-3 S-K 16 KINE 1P90 SP2023 8  Neuroglia Oligodendrocytes similar to astrocytes Smaller cell body Fewer and shorter cytoplasmic processes Wrap axons in myelin (insulation) White matter = myelinated axons Grey matter = neuron bodies, dendrites, unmyelinated axons 17 MYELINATION CENTRAL CANAL IN THE CNS Ependymal cells Gray matter Neurons Microglial cell Myelinated axons Internode Myelin White (cut) Oligodendrocyte Astrocyte Axon matter Myelin sheath gap Unmyelinated axon Basal lamina Capillary Figure 13.6 18 KINE 1P90 SP2023 9  Neuroglia of the PNS Satellite cells Regulate the exchange of material between the cell body and the environment Schwann cells Also called neurolemmocytes Form a myelin sheath 19 PERIPHERAL AXONS & SCHWANN CELLS Node of Ranvier Fig. 13- 9 20 KINE 1P90 SP2023 10  Anatomy of a Peripheral Nerve Blood vessels Connective Tissue Layers Epineurium covering peripheral nerve Perineurium (around one fascicle) Endoneurium Schwann cell Myelinated axon Fascicle a A typical peripheral nerve and its connective tissue wrappings Figure 14.5a 21 THE SPINAL CORD 1. CONDUCTS NERVE IMPULSES TO & FROM THE BRAIN 2. PROCESSES SOME SENSORY INFORMATION TO ALLOW REFLEX [MOTOR] ACTIONS 22 KINE 1P90 SP2023 11  Central Nervous System Brain Integrates and processes information Can function with the spinal cord Can function independently of the spinal cord Spinal cord Integrates and processes information Can function with the brain Can function independently of the brain Fig. 13- 1 23 Gross Anatomy of the Spinal Cord Cervical spinal C1 C2 C3 C4 nerves C5 C6 C7 C8 45 cm in length T1 T2 T3 T4 Passes through the foramen magnum T5 T6 T7 Extends from the brain to L1 Thoracic spinal T8 T9 Consists of: nerves T10 T11 Cervical region T12 L1 Thoracic region L2 Lumbar region Lumbar spinal L3 L4 Sacral region nerves L5 Coccygeal region S1 Sacral spinal S2 S3 nerves S4 S5 Coccygeal nerve (Co1) a Superficial anatomy and orientation of the adult spinal cord. The numbers to the left identify the spinal nerves and indicate where the nerve roots leave the vertebral canal. The spinal cord, however, extends from the brain only to the level of vertebrae L1–L2. 24 KINE 1P90 SP2023 12  Gross Anatomy of the Spinal Cord Cervical spinal nerves C1 C2 C3 C4 C5 C6 Cervical C7 C8 enlargement T1 T2 T3 T4 31 spinal segments T5 T6 T7 Each segment consists of: Thoracic T8 Posterior median sulcus spinal T9 Dorsal root nerves T10 T11 Lumbosacral enlargement Dorsal root ganglia T12 Conus medullaris L1 Ventral root L2 Spinal nerve Lumbar spinal L3 L4 Inferior tip of spinal cord nerves L5 Cauda equina S1 Sacral spinal S2 S3 nerves S4 S5 Coccygeal Filum terminale nerve (Co1) (in coccygeal ligament) a Superficial anatomy and orientation of the adult spinal cord. The numbers to the left identify the spinal nerves and indicate where the nerve roots leave the vertebral canal. The spinal cord, however, extends from the brain only to the level of vertebrae L1–L2. Figure 14.1a 25 Spinal Meninges Dura Mater Tough fibrous outermost layer of the meninges Stabilizes the spinal cord within the vertebral canal Arachnoid Mater Middle meningeal layer Separated from the pia mater by subarachnoid space Cerebrospinal fluid flows within this space Pia Mater Deepest meningeal layer Blood vessels are found in this layer Firmly bound to the brain tissue and the spinal cord tissue 26 KINE 1P90 SP2023 13  Spinal Meninges Gray matter White matter Dorsal root ganglion Ventral root Spinal nerve Dorsal root Meninges Pia mater Arachnoid mater Dura mater *Subarachnoid space CSF Figure 14.2a 27 Spinal cord Anterior median fissure Pia mater →3 Denticulate ligaments Arachnoid mater (reflected) →2 Dura mater (reflected) →1 Spinal blood vessel Dorsal root of sixth cervical nerve Ventral root of sixth cervical nerve c Anterior view of spinal cord shows meninges and spinal nerves. For this view, the dura and arachnoid membranes have been cut longitudinally and retracted (pulled aside); notice the blood vessels that run in the subarachnoid space bound ©to2015 the Pearson Education, outer surface of the Inc. delicate pia mater. Figure 14.2c 28 KINE 1P90 SP2023 14  Sectional Anatomy of the Spinal Cord Gray Matter Central canal (filled with CSF) Consists of somas (cell bodies) surrounding the central canal Consists of glial cells White Matter Consists of axons Nerves are organized into tracts or columns Located outside the gray matter area 29 Sectional Anatomy of the Spinal Cord Organization of Gray Matter Somas are organized into groups called: 1. Sensory nuclei 2. Motor nuclei Transverse view shows: Posterior gray horns Lateral gray horns Anterior gray horns Gray commissure 30 KINE 1P90 SP2023 15  Sectional Organization of the Spinal Cord Posterior median sulcus Posterior From dorsal root gray horn Posterior gray commissure Somatic Sensory Visceral nuclei Lateral gray horn Visceral Motor Anterior nuclei gray horn Somatic To ventral Anterior gray root commissure Anterior median fissure b The left half of this sectional view shows important anatomical landmarks; the right half indicates the functional organization of the gray matter in the anterior, lateral, and posterior gray horns. Figure 14.4b 31 Sectional Anatomy of the Spinal Cord Organization of White Matter Consists of columns of nerves (funiculi) Posterior white column Anterior white column Lateral white column Columns convey either: Sensory tracts (ascending tracts) Motor tracts (descending tracts) 32 KINE 1P90 SP2023 16  Posterior white Leg column (funiculus) Hip AFFERENT Trunk [SENSORY] Arm Lateral white column (funiculus) Flexors Extensors Hand Forearm Arm Shoulder EFFERENT Trunk [MOTOR] Anterior white Anterior white column (funiculus) commissure c 33 PERIPHERAL DISTRIBUTION OF SPINAL NERVES Fig. 14- 6 34 KINE 1P90 SP2023 17  Motor Commands Postganglionic fibers To skeletal to smooth muscles, muscles of back glands, etc., of back Dorsal Visceral Somatic Dorsal root root motor motor ganglion Dorsal ramus Ventral ramus To skeletal muscles of body wall, limbs Ventral root Postganglionic fibers to smooth muscles, glands, etc., of body wall, limbs Spinal nerve White ramus Sympathetic ganglion (preganglionic) Rami communicantes Gray ramus Postganglionic fibers (postganglionic) to smooth muscles, glands, visceral organs Sympathetic nerve in thoracic cavity KEY Somatic motor Preganglionic fibers to commands sympathetic ganglia innervating aboomino- Visceral motor commands pelvic viscera Figure 14.6 35 Sensory Information From interoceptors From exteroceptors, of back proprioceptors of back Dorsal Somatic Visceral root sensory sensory Dorsal ramus Ventral ramus From exteroceptors, proprioceptors of body wall, limbs Dorsal root ganglion From interoceptors of body wall, limbs Rami communicantes Ventral KEY root Somatic sensations Visceral From interoceptors sensations of visceral organs Figure 14.6b 36 KINE 1P90 SP2023 18  Occipital bone Spinal cord emerging from Spinal Nerves foramen magnum Cervical plexus (C1–C5) Cervical spinal nerves (C1–C8) 31 pairs of spinal nerves: Brachial plexus 8 cervical nerves (C5–T1) 12 thoracic nerves 5 lumbar nerves Thoracic 5 sacral nerves spinal nerves (T1–T12) 1 coccygeal nerve Lumbar plexus Lumbar (T12–L4) spinal nerves (L1–L5) Sacral plexus Sciatic (L4–S4) nerve Sacral spinal nerves (S1–S5) Coccygeal nerves emerging from © 2015 Pearson Education, (Co1) Inc. sacral foramina 37 Reflexes Reflex An immediate involuntary motor response Reflex Arc The neural “wiring” of a single reflex Begins at a sensory receptor and ends at a peripheral receptor 38 KINE 1P90 SP2023 19  Reflexes Pathway of a Reflex Arc 1. Activation of a sensory receptor 2. Relay of information to the CNS 3. Information processing 4. Activation of a motor neuron 5. Response by the effector 39 A Reflex Arc 1 Arrival of 2 Activation of a Dorsal Sensation sensory neuron root relayed to stimulus and activation the brain by of receptor collateral REFLEX ARC Receptor Stimulus Effector Ventral 3 Information processing root in CNS 4 Activation of a 5 Response motor neuron by effector KEY Sensory neuron (stimulated) Excitatory interneuron Motor neuron Figure 14.13 (stimulated) 40 KINE 1P90 SP2023 20  Reflexes Spinal Reflexes Stretch reflex 1. Stimulus stretches a muscle 2. Activates a sensory neuron 3. Information is processed in the spinal cord 4. Motor neurons are activated 5. Muscle (effector) contracts 41 1 Stimulus. Stretching of muscle stimulates 2 Activation of a muscle spindles sensory neuron 3 Information processing at motor neuron 4 Activation of motor neuron 5 Response. Contraction of muscle a Steps 1–5 are common to all stretch reflexes. Figure 14.16a 42 KINE 1P90 SP2023 21  Stretch Receptor (muscle spindle) Stimulus Spinal cord REFLEX ARC KEY Effector Sensory neuron (stimulated) Motor neuron Contraction (stimulated) b The patellar reflex is controlled by muscle spindles in the quadriceps muscle group. The stimulus is a Response reflex hammer striking the muscle tendon, stretching the spindle fibers. This results in a sudden increase in the activity of the sensory neurons, which synapse on spinal motor neurons. The response occurs upon the activation of motor units in the quadriceps group, which produces an immediate increase in muscle Figure 14.16b tone and a reflexive kick. 43 BREAK 44 KINE 1P90 SP2023 22  Brain Brain anatomy Meninges Ventricles +CSF Cranial Nerves Arteries Autonomic Nervous System 45 GROSS ANATOMY Fig. 16- 16 46 KINE 1P90 SP2023 23  The Cerebrum The cerebrum consists of: Two hemispheres Several lobes Frontal, parietal, occipital, and temporal Gyri and sulci – increase surface area Hemispheric Specialization Left hemisphere Speech center, writing, language, mathematics Right hemisphere Analysis by touch, spatial visualization 47 ANTERIOR Longitudinal Right cerebral fissure hemisphere Left cerebral Cerebral veins and hemisphere arteries covered by arachnoid mater Central sulcus Parieto-occipital Cerebellum sulcus POSTERIOR a Superior view. Figure 16.16a 48 KINE 1P90 SP2023 24  The Cerebrum The cerebral lobes Frontal lobe Conscious control of skeletal muscles Occipital lobe Perception of visual stimuli Parietal lobe Conscious perception of touch, pressure, vibration, pain, temperature, and taste Temporal lobe Conscious perception of auditory and olfactory stimuli 49 Precentral gyrus Postcentral gyrus Central sulcus Parietal Lobe Frontal lobe of left cerebral hemisphere Occipital lobe Lateral sulcus Temporal lobe Cerebellum Pons Medulla oblongata Figure 16.17b 50 KINE 1P90 SP2023 25  Major Divisions of the Brain (6) Left cerebral hemisphere Gyri CEREBRUM Sulci Conscious thought processes, Fissures intellectual functions Memory storage & processing Conscious and subconscious regulation of skeletal muscle contractions Spinal cord CEREBELLUM Coordinates complex somatic motor patterns Adjusts output of other Figure 16.1 somatic motor centers in brain and spinal cord 51 DIENCEPHALON THALAMUS Relay and processing centers for sensory information HYPOTHALAMUS Centers controlling emotions, autonomic functions, and hormone production EPITHALAMUS MESENCEPHALON Brain stem Processing of visual and auditory data Generation of reflexive somatic motor responses Maintenance of consciousness PONS Relays sensory information to MEDULLA OBLONGATA cerebellum and thalamus Relays sensory information to thalamus and the brain Subconscious somatic and stem visceral motor centers Autonomic centers for regulation of visceral function (cardiovascular, respiratory, and Fig. 16.1 digestive system activities) 52 KINE 1P90 SP2023 26  Central sulcus Postcentral gyrus Precentral gyrus Diencephalon Corpus callosum 1. Thalamus 2. Hypothalamus Frontal lobe 3. Epithalamus Pineal gland (melatonin) Temporal lobe Cerebellum Mesencephalon Pons Medulla oblongata Figure 16.13a 53 Organization of the Brain Gray Matter & White Matter Organization The cerebrum consists of: Gray matter consists of cell bodies Cerebrum & cerebellum white matter is covered by the cortex (superficial layer of gray matter) 54 KINE 1P90 SP2023 27  The Cranial Meninges Protects & supports the brain Surround the brain and the spinal cord Dura mater endosteal Cranium meningeal Cerebral cortex Arachnoid Cerebral mater cortex Pia mater Cerebellum Medulla oblongata Spinal cord Fig 16.3 55 ANTERIOR Loose Cranium connective Dura mater tissue and periosteum Subarachnoid of cranium space Epicranial aponeurosis Arachnoid mater Scalp Cerebral cortex covered by pia mater POSTERIOR Figure 16.4 56 KINE 1P90 SP2023 28  Superior sagittal Cranial sinus Meninges Dura mater Subdural Arachnoid mater space Arachnoid Arachnoid trabeculae granulation Pia mater Falx cerebri Cerebral vein Subarachnoid space Cerebral cortex Folds of the Dura mater * Dural sinuses = large veins 57 Dura Mater - Falx and Sinus Superior sagittal sinus Inferior sagittal sinus Cranium Dura Mater Falx cerebri Tentorium cerebelli Diaphragma sellae → sphenoid Falx cerebelli Straight sinus Transverse sinus Figure 16.3b 58 KINE 1P90 SP2023 29  VENOUS RETURN JUGULAR VEIN 59 VENOUS RETURN Superior sagittal sinus Transverse sinus Sigmoid sinus JUGULAR VEIN 60 KINE 1P90 SP2023 30  The Cranial Meninges 2. Arachnoid Matter Smooth, does not follow sulci and gyri Subarachnoid space (network of collagen and fibres) CSF and arteries and veins 3. Pia Mater Attached to the surface of the brain Follows the sulci and gyri of the brain Helps to anchor the larger blood vessels of the cerebrum 61 Subdural Subarachnoid Cranial space space Meninges Dura mater Arachnoid mater Arachnoid trabeculae Pia mater Cerebral vein Cerebral Perivascular space cortex b A detailed view of the arachnoid mater, the subarachnoid space, and the pia mater. Note the relationship between the cerebral vein and the subarachnoid space. Figure 16.5b 62 KINE 1P90 SP2023 31  Ventricular System of the Brain Ventricles are fluid-filled cavities Filled with cerebrospinal fluid (CSF) Lined with ependymal cells Fluid transports nutrients to the CNS and transports waste away from the CNS CSF also provides cushion for the CNS CSF made in choroid plexus - Ependymal cells highly permeable capillaries 63 Ventricular System of the Brain Lateral ventricles in cerebral hemispheres Septum Interventricular pellucidum foramen Third ventricle Aqueduct of midbrain Inferior horn of lateral Fourth ventricle ventricles Cerebellum Central canal d Diagrammatic coronal section showing the interconnections between the ventricles Figure 16.2d 64 KINE 1P90 SP2023 32  Anterior horns of lateral ventricles Lateral ventricles Interventricular foramen Third ventricle Posterior horns of lateral ventricles Inferior horns of lateral ventricles Aqueduct of midbrain Medulla oblongata Fourth Central canal ventricle a Orientation and extent of the ventricles as seen in a lateral view of a transparent brain Fig. 16.2 65 Arachnoid granulations Circulation of Cerebrospinal Fluid Superior sagittal sinus Made in the choroid Aqueduct of midbrain plexus ~500ml/day Choroid plexus of fourth ventricle Central canal Circulating CSF ~150ml ……so CSF is replaced every 8 hours Filum terminale Figure 16.7 66 KINE 1P90 SP2023 33  Superior Dura mater sagittal sinus Cranium (endosteal layer) Arachnoid granulation Fluid movement Arachnoid trabecula Cerebral Dura mater cortex (meningeal layer) Pia mater Subdural space Subarachnoid Arachnoid space mater Figure 16.7 67 BASIC ARTERIAL SUPPLY TO THE BRAIN Middle cerebral Arteries of the Circle of Willis 1. Anterior communicating 2. Anterior cerebral 3. Internal Carotid 4. Posterior communicating 5. Posterior cerebral 6. Basilar 7. Vertebral 68 KINE 1P90 SP2023 34  The Arterial Supply to the Brain Anterior communicating Internal carotid (cut) Anterior cerebral Posterior communicating Posterior cerebral Posterior cerebral Superior cerebellar Basilar Pontine Vertebral Anterior inferior cerebellar Posterior inferior cerebellar Anterior spinal Figure 22.13a 69 The Cranial Nerves There are 12 pairs of cranial nerves innervate the periphery emerging from the brain (not the spinal cord) found on the ventrolateral surface of the brain numbered beginning at the anterior aspect of the brain They are numbered CN I to CN XII 70 KINE 1P90 SP2023 35  Cranial Nerves Olfactory nerve (N I) Optic nerve (N II) Oculomotor nerve (N III) Trochlear nerve (N IV) Trigeminal nerve (N V) Abducens nerve (N VI) Facial nerve (N VII) Vestibulocochlear nerve (N VIII) Glossopharyngeal nerve (N IX) Vagus nerve (N X) Hypoglossal nerve (N XII) Accessory nerve (N XI) Figure 16.23b 71 72 KINE 1P90 SP2023 36  NERVE PRIMARY FUNCTION Olfactory nerve (N I) Special sensory (smell) Optic Nerve (NII) Special sensory (vision). Retina of the eye Oculomotor Nerve (N III) Motor, eye movements. Intrinsic eye muscles (diameter of the pupil). External muscles Trochlear Nerve Motor, eye movements (N IV) Trigeminal Nerve Sensory and motor, opthalmic branch (sensory), (N V) maxilary branches (sensory), mandibular branch Abducens Nerve (N VI) Motor, eye movements, lateral movements Facial Nerve (N VII) Sensory and motor, taste receptors on the tongue, and motor nuclei of pons, motor control of facial expression Vestibulocochlear Nerve (N VIII) Special sensory, balance and equilibrium, and hearing Glossopharyngeal Nerve (N IX) Sensory and motor, sensory on the tongue, pharynx, and palate, carotid arteris, motor form the motor nuclei of the medulla oblongata, pharynx and parotid salivary gland 73 Nerve Primary Function Vagus Nerve (N X) Sensory and motor. Sensory of the pharynx, auricle, diaphragm, visceral organs. Visceral motor and motor nuceli in the medulla oblongata Motor to muscles of the palate and pharynx, motor to respiratory, cardiovascular, and digestive organs Accessory Nerve (N XI) Motor. Voluntary swallowing muscles of the soft palate and pharynx and muscles that control the vocal cords. Controls muscles of the neck and back. Hypoglossal Nerve (N XII) Motor, tongue movements “SOME SAY MARRY MONEY BUT MY BROTHER SAYS BIG BRAINS MATTER MORE” 74 KINE 1P90 SP2023 37  AUTONOMIC NERVOUS SYSTEM Outline: Somatic vs autonomic Sympathetic vs parasympathetic 75 Overview of the Nervous System Reminder… CENTRAL NERVOUS SYSTEM Information processing afferent division efferent division PERIPHERAL NERVOUS SYSTEM includes Somatic nervous Autonomic system nervous system Parasympathetic Sympathetic division division Special sensory Visceral sensory Somatic sensory receptors receptors receptors Smooth muscle Skeletal muscle Cardiac muscle Glands RECEPTORS EFFECTORS Figure 13.2 76 KINE 1P90 SP2023 38  Autonomic Nervous System (ANS) Functions outside of our conscious awareness system makes routine adjustments in our body’s systems Regulates body temperature Coordinates cardiovascular, respiratory, digestive, excretory, and reproductive functions 77 Somatic vs. Autonomic (General comparison) Somatic Autonomic single neuron between two neurons between CNS CNS and skeletal muscle and organ cells only innervates skeletal innervates smooth and muscle cardiac muscle, glands, etc. leads ONLY to excitation can be either excitatory or usually voluntary inhibitory myelinated axons usually involuntary Pre-ganglionic axon myelinated 78 KINE 1P90 SP2023 39  *sympathetic trunks Cervical SNS PSNS Thoracic Lumbar Sacral S-K 79 Vander Fig 6-40 PSNS SNS Pre-ganglion *trunks Post-ganglion 80 KINE 1P90 SP2023 40  Sympathetic Parasympathetic CNS Preganglionic neuron PNS Preganglionic KEY Sympathetic fiber Neurotransmitters ganglion Acetylcholine Norepinephrine or Epinephrine Ganglionic neurons Circulatory system Postganglionic Parasympathetic fiber ganglion TARGET Figure 17.10 81 SNS Adrenal Medulla 82 KINE 1P90 SP2023 41  SNS - “Fight or Flight” SNS dominant in stressful situations ‘extra ability’ in times of stress total body response to a crisis e.g., increase heart rate, blood flow to brain, pupils dilate, gastrointestinal tract inhibited Inhibits non-essential activities (digestive and urinary activities) sympathetic trunks play a role in coordination 83 PSNS Parasympathetic NS controls “rest and digest” functions operate more independently 84 KINE 1P90 SP2023 42  Parasympathetic NS Functions Stimulation generally results in: Relaxation Food processing Energy absorption Major effects of parasympathetic stimulation Pupil constriction Secretion of digestive enzymes from: Salivary glands, gastric glands, duodenal glands, pancreas, and liver 85 Vander Fig 6-40 PSNS SNS 86 KINE 1P90 SP2023 43  Vagus Nerve Major nerve of the PSNS involved in cardio-respiratory regulation heart and lung function 87 KINE 1P90 SP2023 44