Chapter 8 Nervous System PDF

Nervous System - carries information about the uniform diameter and may vary different tissues of the body to the in length from a few millimeters - a communic...

Nervous System - carries information about the uniform diameter and may vary different tissues of the body to the in length from a few millimeters - a communication system. CNS and delivers commands from to more than a meter. Axons of - communication occurs through the CNS to other body tissues that sensory neurons conduct electrical signals (arrow) that spread alter body activities. action potentials towards the over the cell membrane of neurons - subdivision: CNS. Axons of motor neurons and cause changes at the synapse, a. Sensory Division or Afferent conduct action potentials away the communication junction between (toward) Division – conducts action from the CNS. Axons also the neuron and its neighboring cell. potentials from sensory receptors to conduct action potentials from the CNS. one part of the brain or spinal o Sensory Neurons - cord to another part. An axon neurons that transmit may remain unbranched or may FUNCTIONS action potentials from the branch to form Collateral periphery to the CNS. Axons. Axons can be The nervous system is involved b. Motor Division or Efferent Division surrounded by a highly in some way in nearly every body function. – conducts action potentials from the specialized insulating layer of We can consider the nervous system as a CNS to effector organs, such as cells called the myelin sheath. communication system, receiving muscles (voluntary) and glands signals from and sending commands to (involuntary). different areas of the body. By way of this o Motor Neurons – neurons 1. Multipolar neurons – many communication, the nervous system helps that transmit action dendrites and a single axon. Most to coordinate the body functions to potentials from the CNS neurons of CNS and nearly all maintain homeostasis. toward the periphery. motor neurons. Subdivision bases on the type of 1. Receiving sensory input. Sensory effector being innervated: 2. Bipolar neurons have two receptors monitor numerous external a. Somatic (bodily) Nervous processes: one dendrite and one and internal stimuli. We are aware of System - transmits action axon. Some sensory organs sensations from some stimuli, such as potentials from the CNS to (retina of the eye and nasal cavity). vision, hearing, taste, smell, touch, skeletal muscles. pain, body position, and temperature. b. Autonomic (self- 3. Pseudo-unipolar neurons have a Other stimuli, such as blood pH, blood governing) Nervous process (axon) extending from the gases, and blood pressure, are System - transmits action cell body. Branches shortly after the processed at a subconscious level. potentials from the CNS to cell body: one extends to the 2. Integrating information. The brain cardiac muscle, smooth periphery, and the other extends to and spinal cord are the major organs muscle, and glands. the CNS. for processing sensory input and i. Sympathetic initiating responses. The input may Division – fight W/ a small, dendrite-like produce an immediate response, be and flight sensory receptors at the periphery stored as memory, or be ignored. ii. Parasympatheti where axon receives sensory 3. Controlling muscles and glands. c Division – rest information from and transmits that Skeletal muscles normally contract or digest information in the form of action only when stimulated by the nervous potentials to the CNS. Most system. Thus, by controlling skeletal sensory neurons. muscle, the nervous system controls Enteric Nervous System (ENS) – a the major movements of the body. unique part of the peripheral nervous The nervous system also participates system. Has both sensory and motor Glial Cells (nerve glue) a.k.a Neuro in controlling cardiac muscle, smooth neurons contained wholly within the Glia muscle, and many glands. digestive tract. The ENS can function 4. Maintaining homeostasis. The without input from the CNS or other - the supportive cells of the CNS and nervous system plays an important parts of the PNS, although it is normally PNS; do not conduct action role in maintaining homeostasis. This integrated with the CNS by sensory potentials. function depends on the nervous neurons and ANS motor neurons. - instead, carry out different activities system’s ability to detect, interpret, that enhance neuron function and and respond to changes in internal CELLS OF THE NERVOUS SYSTEM maintain normal conditions within and external conditions. In nervous tissue. response, the nervous system can a. Neurons - more numerous than neurons. stimulate or inhibit the activities of b. Glial Cells Most glial cells retain the ability to other systems to help maintain a divide, unlike neurons. constant internal environment. Neurons (nerve) a.k.a Nerve Cell 5. Establishing and maintaining - receive stimuli, conduct action Four Types of Glial Cell in the CNS mental activity. The brain is the potentials, and transmit signals to 1. astrocytes center of mental activity, including oher neurons or effector organs 2. ependymal cells consciousness, memory, and - three parts: 3. microglia thinking. a. Cell Body – w/ a single nucleus 4. oligodendrocytes. ( the source of information for DIVISION OF THE NERVOUS gene expression. Astrocytes SYSTEM b. Dendrites (trees) – short, often - major supporting cells in the CNS. highly branching. Most - can stimulate or inhibit the signaling The nervous system can be divided into dendrites are extensions of the activity of nearby neurons. two major divisions: neuron cell body, but dendrite- - participate with the blood vessel 1. Central Nervous System like structures also project from endothelium to form a permeability a. brain the peripheral ends of some barrier, called the blood-brain b. spinal cord sensory axons. Dendrites barrier, between the blood and the 2. Peripheral Nervous System - usually receive information CNS. consists of all the nervous tissue from other neurons or from - help limit damage to neural tissue; outside the CNS, including sensory receptors and however, the repair process can form nerves and ganglia transmit the information a scar that blocks regeneration of toward the neuron cell body. damaged axons. PNS c. Axons - a single long cell - the communication link between the process extending from the Ependymal Cells CNS and the various parts of the neuron cell body. Axon Hillock - line the fluid-filled cavities body. – area where the axon leaves (ventricles and canals) within the cell body. Each axon has a CNS. - some produce cerebrospinal fluid, propagate action potentials from one cell, which tends to attract the K+ back into and others, with cilia, help move the area of the CNS to another. the cell. cerebrospinal fluid through the CNS. - in the PNS: bundles of axons and associated connective tissue that ❸ Sodium-potassium pump maintains Microglia form nerves. resting levels of ions across the cell - immune cells of the CNS. membrane: To compensate for the - help protect the brain by removing ELECTRICAL SIGNALS AND constant leakage of ions across the bacteria and cell debris. NEURAL PATHWAYS membrane, the sodium-potassium pump (Na+–K+ pump) is required to maintain Oligodendrocytes the greater concentration of Na+ - provide an insulating material that Resting Membrane Potential outside the cell and K+ inside the cell. surrounds axons. The pump actively transports K+ into the cell and Na+ out of the cell. The importance Two types of Glial Cells in the PNS Cells of the body have electrical of this pump is indicated by the astounding 1. Schwann Cells – provide insulating properties. These properties are evident at amount of energy it consumes. It is material around axons the cell membrane, a boundary that estimated that the sodium-potassium pump 2. Satellite Cells – found around the prevents the free movement of ions into consumes: cell bodies of certain neurons. and out of the celI. Flow of ions through ion Typical cell: 25% of all the ATP Provides support and nutrition to channels is due to: Neurons: 70% of the ATP the neurons and protect the neurons i. their differences in from heavy-metal poisons, such as concentration across the membrane. Neuron Communication lead and mercury. ii. their electrical charges, because of the attraction Neurons, as well as muscle cells, are Myelin Sheaths between opposite charges. excitable cells, meaning that the resting membrane potential changes in - specialized layers that wrap around There are two basic types of ion channels: response to stimuli. In muscle cells, this the axons of oligodendrocytes in the 1. leak channels – always open change in the resting membrane potential CNS and Schwann cells in the PNS. 2. gated channels – closed until results in contraction; but in neurons, this opened by specific signals. change is a means by which the cell Myelinated Axons - axons with these 3. chemically gated channels are communicates with other cells. We can myelin sheaths. opened by specific chemicals; organize our discussion of neuron 4. voltage-gated channels are communication into three stages: - repeatedly wraps around a segment opened by a change in the of an axon to form a series of tightly electrical property of the cell ❶ Generation of action potentials, wrapped cell membranes. membrane; depolarization ❷ Action potential propagation along the - an excellent insulator that prevents cell membrane, and almost all ion movement across the Resting Membrane Potential ❸ Communication with target cell at the cell membrane. - small voltage difference called synapse. - Nodes of Ranvier – gaps in the potential in an unstimulated cell myelin sheath every millimeter - cell membranes – polarized Action Potentials between the myelinated areas. Ion Inside: (-) charge Resting membrane potential of a movement can occur here. Outside: (+) charge neuron changes in response to stimuli. - increases the speed and efficiency - generated primarily by the uneven These stimuli activate gated ion channels. of action potential generation along distribution of K+, Na+, and negatively The opening and closing of gated ion the axon. charged proteins across the cell channels can change the permeability membrane characteristics of the cell membrane and Unmyelinated Axons – lack the myelin hence change the membrane potential. sheaths however, these axons rest in ❶ Distribution of ions and proteins across In neuron communication, these indentations of the oligodendrocytes in the cell membrane: changes can lead to action potentials, the CNS and the Schwann cells in the PNS. In a resting cell: electrical signals that are conducted A typical small nerve, which consists of Inside the cell: higher concentration of K+; along the cell membrane from one axons of multiple neurons, usually contains w/ more negatively charged proteins region of the cell to another. The more unmyelinated axons than inside the cell that are isolated in the channels responsible for the action myelinated axons. cytoplasm due to impermeability to cell potential are voltage-gated Na+ and K+ membrane, !! hence the negative charge channels. Organization of Nervous Tissue inside the cell membrane Outside the cell: higher concentration of ❶ When the cell membrane is at rest, the Na+ voltage-gated channels are closed. Nervous tissue varies in color due to the ❷ When a stimulus is applied to a muscle location and arrangement of the parts of ❷ Movement of ions through leak cell or neuron, following neurotransmitter neurons and glial cells. Nervous tissue channels: activation of chemically gated channels, exists as: In neurons: K+ leak channels are 50-100x Na+ channels open very briefly, and Na+ greater than Na+ leak channels, !! hence diffuses quickly into the cell. This Gray Matter the greater permeability to K+ than to Na+, movement of Na+, which is called a local - consists of groups of neuron cell which also means that K+ has the greater current, causes the inside of the cell bodies and their dendrites, where influence on the resting membrane membrane to become positive, a change there is very little myelin. potential. called depolarization. This depolarization - in the CNS: K+ and Na+ moves down their results in a local potential. If depolarization o Cortex – gray matter on the concentration gradient. As positively is not strong enough, the Na+ channels surface of the brain charged K+ leaks out of the cell via the leak close again, and the local potential o Nuclei – clusters of gray matter channels, the charge inside the cell disappears without being conducted along located deeper within the brain. membrane becomes even more the neuron cell membrane. If - in the PNS: negative. Because opposite charges are depolarization is large enough, Na+ o Ganglion (ganglia, swelling or attracted to each other, the negatively enters the cell so that the local potential knot) – cluster of neuron cell charged molecules inside the cell tend to reaches a threshold value. This threshold bodies. attract the positive K+ back into the cell. depolarization causes voltage-gated Na+ As a result, K+ is moving into as well as channels to open. Threshold is most often White Matter out of the cell. The resting membrane reached at the axon hillock, near the cell - bundles of parallel axons with their potential is the point of equilibrium at which body. The opening of these channels myelin sheaths, which are whitish in the tendency for K+ to move down its causes a massive, 600-fold increase in color. concentration gradient out of the cell is membrane permeability to Na+. Voltage- - in the CNS: it forms nerve tracts, or balanced by the negative charge within the gated K+ channels also begin to open. As conduction pathways, which more Na+ enters the neuron, unnecessary for action potentials to become more negative, or depolarization continues at a much faster travel along the entire cell membrane. hyperpolarized, and an action pace. Eventually a brief reversal of charge Several hundred times fewer ions potential is inhibited from occurring. takes place across the cell membrane— cross the cell membrane during Of the many neurotransmitters or the inside of the cell membrane becomes conduction in myelinated cells than in suspected neurotransmitter substances, positive relative to the outside of the cell unmyelinated cells. Much less the best known are acetylcholine (ACh) membrane. energy required for the sodium- and norepinephrine. ❸ The charge reversal causes Na+ potassium pump to maintain the ion channels to close and Na+ then stops distribution. Neurotransmitters normally: entering the cell. Also during this time, - do not remain in the synaptic cleft more K+ channels are opening and K+ Speed of action potential conduction varied indefinitely. Thus, their very short- leaves the cell. The outward flow of K+ on myelinated axons relatve to the axon term effects on the target cell. repolarizes the cell membrane to its resting diameter - become reduced in concentration membrane potential. Depolarization and a. medium-diameter, lightly when they are either rapidly broken repolarization constitute an action myelinated axons, (autonomic down by enzymes within the potential. At the end of repolarization, the neurons) - 3-15 meters per second synaptic cleft or are transported charge of the cell membrane briefly (m/s), back into the presynaptic terminal. becomes more negative than the resting b. large-diameter, heavily myelinated membrane potential; this condition is called axons (sensory and motor neurons) Ex: hyperpolarization. The elevated – 15-120 m/s; allows rapid responses In synapses where acetylcholine is permeability to K+ lasts only a very short to changes in the external the neurotransmitter, such as in the time. environment. neuromuscular junction, an enzyme https://youtu.be/oa6rvUJlg7o?si=W4_Lb- called acetylcholinesterase breaks K4XfNVFbV1 Synapse down acetylcholine. The breakdown - junction where the axon of one products are then returned to the neuron interacts with another neuron presynaptic terminal for reuse. In summary, the resting or with cells of an effector organ, such Norepinephrine is either actively membrane potential is set by the activity of as a muscle or gland. transported back into the presynaptic the leak channels. On stimulation, - three major components: terminal or broken down by enzymes. chemically gated channels are opened and a. the end of the axon forms a initiate local potentials. If sufficiently strong, presynaptic terminal, The release and breakdown or the local potentials activate voltage-gated b. the membrane of the dendrite or removal of neurotransmitters occurs so channels to initiate an action potential. effector cell is the postsynaptic rapidly that a postsynaptic cell can be Action potentials occur in an all- membrane, stimulated many times a second. or-none fashion. That is, if threshold is c. the space separating the reached, an action potential occurs; if presynaptic and postsynaptic Drugs can modulate the action of threshold is not reached, no action membranes is the synaptic neurotransmitters at the synapse. potential occurs. Action potentials in a cell cleft. Cocaine and amphetamines – increase are all of the same magnitude—in other the release and block the reuptake of words, the amount of charge reversal is Communication bet. neuron and its norepinephrine, resulting in always the same. This means that the target cell occurs thru chemical signals. overstimulation of postsynaptic neurons variation in stimulation is not due to Neurotransmitter (neuro-, nerve + and deleterious effects on the body. stronger or weaker action potentials, transmitto, to send across) – chemical Drugs that block serotonin reuptake are because all action potentials have the substances that act chemical signals and particularly effective at treating same pattern of changes in the membrane are stored in synaptic vesicles in the depression and behavioral disorders. potential. Instead, stronger stimuli produce presynaptic terminal. a greater frequency of action potentials. Neuronal Pathways Thus, neural signaling is based on the number of action potentials. ❶ When an action potential reaches the presynaptic terminal, voltage-gated Within the CNS, neurons are Ca2+ channels open, and Ca2+ moves organized to form pathways ranging from Action Potential Conduction into the cell. relatively simple to extremely complex. Once an action potential is ❷ This influx of Ca2+ causes the Two simplest pathways are: generated, it is conducted along the cell release of neurotransmitters by a. Converging Pathways – two or more membrane. The pattern of action potential exocytosis from the presynaptic terminal. neurons synapse with the same conduction along a neuron cell membrane ❸ The neurotransmitters diffuse across postsynaptic neuron. Allows may occur in one of two ways: the synaptic cleft toward the postsynaptic information transmitted in more than 1. continuous conduction – membrane. one neuronal pathway to converge unmyelinated axons; w/o glial cells ❹ The neurotransmitters bind to into a single pathway (much slowly). An action potential in specific receptor molecules on the b. Diverging Pathways – axon from one part of a cell membrane postsynaptic membrane. The binding of one neuron divides and synapses stimulates local currents in adjacent neurotransmitters to these membrane with more than one other postsynaptic parts of the cell membrane. The local receptors causes chemically gated neuron. This allows information currents in the adjacent membrane channels for Na+, K+, or Cl− to open or transmitted in one neuronal pathway produce an action potential. By this close in the postsynaptic membrane. to diverge into two or more pathways. means, the action potential is conducted along the entire axon Both the specific channel type cell membrane. and whether or not the channel opens or Within the CNS and in many PNS 2. saltatory (to leap) conduction – closes depend on the type of synapses, it takes more than a single mylinated axons; w/ glial cells (much neurotransmitter in the presynaptic action potential to have an effect. A rapidly). An action potential at one terminal and the type of receptors on the single presynaptic action potential usually node of Ranvier causes a local postsynaptic membrane. The response does not cause a sufficiently large current to flow through the may be either stimulation or inhibition postsynaptic local potential to reach surrounding extracellular fluid and of an action potential in the postsynaptic threshold and produce an action potential through the cytoplasm of the axon to cell. in the target cell. Instead, many the next node, stimulating an action presynaptic action potentials are potential at that node of Ranvier. By Ex: needed in a process called summation. this means, action potentials If Na+ channels open, the “jump” from one node of Ranvier to Summation of signals in neuronal postsynaptic cell becomes the next along the length of the axon. pathways allows integration of multiple depolarized, and an action potential Saltatory conduction greatly subthreshold local potentials. will result if threshold is reached. increases the conduction velocity Summation of the local potentials can If K+ or Cl− channels open, the because the nodes of Ranvier make it bring the membrane potential to inside of the postsynaptic cell tends to threshold and trigger an action potential. 3. lateral horns – small, Knee-Jerk Reflex (a.k.a Patellar Reflex) There are two types of summation: associated with the autonomic - classic example of Stretch Reflex – nervous system. simplest reflex. Occurs when muscles 1. Spatial Summation occurs when the 4. central canal – fluid-filled space contract in response to a stretching local potentials originate from in the center of the spinal cord; force applied to them. different locations on the where CSF flows postsynaptic neuron—for example, ❶ The stimulus for this reflex is stretching from converging pathways. Each column of the spinal cord contains of the quadriceps femoris muscle, the 2. Temporal Summation occurs when ascending and descending tracts, or extensor muscles. When the patellar local potentials overlap in time. pathways. ligament is tapped, the quadriceps femoris This can occur from a single input muscle tendon and the muscles that fires rapidly, which allows the Ascending tracts – consist of axons that themselves are stretched. Sensory resulting local potentials to overlap conduct action potentials toward the brain, receptors within these muscles are also briefly. Descending tracts – away from the brain. stretched, and the stretch reflex is activated. Spatial and temporal summation can ❷ A sensory neuron monitoring the stretch lead to stimulation or inhibition, depending Spinal nerves receptor conducts action potentials to the on the type of signal. Collectively, this - arise from numerous rootlets along spinal cord. integration of multiple inputs determines the dorsal and ventral surfaces of the ❸ Sensory neurons synapse with motor whether the postsynaptic neuron will spinal cord. neurons in the gray matter of the spinal generate an action potential. - formed as the ventral and dorsal roots cord segment. Descending neurons within unite just lateral to the spinal cord the spinal cord also synapse with the CENTRAL AND PERIPHERAL - each spinal nerve has both sensory neurons of the stretch reflex, allowing for NERVOUS SYSTEM and motor axons. conscious modification to their activity. 1. ventral rootlets – combine to ❹ Motor neurons from the spinal cord Central Nervous System (CNS) form a ventral root on the extend to the same muscle of the leg, - consists of the brain and spinal cord ventral (anterior) side of the stimulating them to contract, extending the - the brain is housed within the skull; spinal cord leg, producing the characteristic knee-jerk the spinal cord is in the vertebral 2. dorsal rootlets – combine to response. column. form a dorsal root on the dorsal (posterior) side of the spinal Peripheral Nervous System (PNS) cord. Withdrawal Reflex (a.k.a Flexor Reflex) - consists of all the nerves and ganglia dorsal root ganglion Function is to remove a limb or another outside the brain and spinal cord. (swelling or knot) – region body part from a painful stimulus. The - collects information from numerous of dorsal root; contains the sensory receptors are pain receptors, and sources both inside and on the cell bodies of pseudo- stimulation of these receptors initiates the surface of the body and relays it by unipolar sensory reflex. way of sensory neurons to the CNS, neurons which axons where one of three results is possible: originate in the periphery of 1. information is ignored the body. They pass ❶ Painful stimuli initiate action potentials 2. triggers a reflex, through spinal nerves and at the pain receptors. 3. evaluated more extensively. the dorsal roots to the ❷ The sensory neurons monitoring these - Motor neurons in the PNS relay dorsal horn of the spinal receptors conduct action information from the CNS to muscles cord gray matter. In the potentials through the dorsal root to the and glands in various parts of the dorsal horn, the axons spinal cord. body, regulating activity in those either synapse with ❸ The sensory neurons synapse with structures. The nerves of the PNS can interneurons or pass into interneurons, which in turn synapse with be divided into two groups: 12 pairs of the white matter and motor neurons. cranial nerves and 31 pairs of spinal ascend or descend in the ❹ These neurons stimulate muscles, nerves. spinal cord. usually flexor muscles, that remove the limb from the source of the painful stimulus. SPINAL CORD Reflexes SPINAL NERVES (a.k.a Mixed - an involuntary reaction in response Nerves) Extends from the foramen magnum to the L2 vertebra. Spinal nerves to a stimulus applied to the periphery and transmitted to the CNS. - arise along the spinal cord from the communicate between the spinal cord and - allow a person to react to stimuli more union of the dorsal roots and ventral the body. quickly than is possible if conscious roots thought is involved. - contain axons of both sensory and Cauda Equina – the inferior end of the somatic motor neurons and thus are spinal cord and the spinal nerves exiting called mixed nerves. there resemble a horse’s tail. Reflex Arc - neuronal pathway by which a reflex - some also contain parasympathetic or occurs. sympathetic axons. A cross section reveals that the spininal - basic functional unit of the nervous - most exit the vertebral column cord consists of a superficial white matter system because it is the smallest, between adjacent vertebrae. portion and a deep gray matter portion. simplest pathway capable of receiving - categorized by the region of the a stimulus and yielding a response vertebral column from which they White Matter – myelinated axons. The - five basic components: emerge—cervical (C), thoracic (T), white matter in each half of the spinal cord ❶ sensory receptor; lumbar (L), sacral (S), and coccygeal is organized into three columns: ❷ sensory neuron; (Co). 1. dorsal column (posterior) ❸ in some reflexes, interneurons, which - are numbered (starting superiorly) 2. ventral column (anterior) are neurons located between and according to their order within that 3. lateral colum communicating with two other neurons; region. The 31 pairs of spinal nerves ❹ motor neuro are therefore C1-C8, T1-T12, L1-L5, Gray Matter – collection of neuron cell ❺ effector organ (muscles or glands). S1-5, and Co. bodies. Shaped like the letter. 1. dorsal horns (posterior) - w/ Dermatome – area of skin supplied with cell body of autonomic motor The simplest reflex arcs do not involve sensory innervation by a pair of spinal neurons; sensory interneurons. Most reflexes occur in the spinal cord or brainstem rather than in nerves. Each of the spinal nerves except 2. ventral horns (anterior) – w/ cell the higher brain centers. C1 has a specific cutaneous sensory body of somatic motor neurons distribution. whose axons form the ventral roots Spinal nerves is organized into three Obturator Nerve – innervates the muscles between the cerebrum and the major plexuses of the medial thigh and the skin over the cerebellum. o Plexuses (braids) – where same region. - functional bridge between the neurons of several spinal nerves Femoral Nerve – innervates the anterior cerebrum and cerebellum, but on come together and intermingle. thigh muscles and the skin over the the anterior surface it resembles an Reorganizes the neurons so that anterior thigh and medial side of the leg. arched footbridge. branches of nerves extending Tibial Nerve – innervates the posterior - several nuclei of the medulla from each plexus contain thigh muscles, the anterior and posterior oblongata extend into the lower part of neurons from different spinal leg muscles, and most of the intrinsic foot the pons: segments. muscles. It also innervates the skin over 1. breathing, swallowing, and the sole of the foot. balance are controlled in the 1. Cervical Plexus Common Fibular Nerve – innervates the lower pons 2. Brachial Plexus muscles of the lateral thigh and leg and 2. chewing, salivation 3. Lumbosacral Plexus some intrinsic foot muscles. It also innervates the skin over the anterior and The major nerves of the neck and limbs are lateral leg and the dorsal surface (top) of Midbrain branches of these plexuses. Spinal nerves the foot. - superior to the pons, is the smallest T2 through T11 do not join a plexus. The tibial and common fibular nerves are region of the brainstem Instead, these nerves extend around the bound together within a connective tissue - dorsal part of the midbrain consists of thorax between the ribs, giving off sheath and together are called the Sciatic four mounds of tissue called the branches to muscles and skin. Motor Nerve. colliculi (hill). nerve fibers derived from plexuses a. Inferior Colliculi – major relay innervate skeletal muscles, and sensory BRAIN centers for the auditory nerve nerve fibers in those plexuses supply pathways in the CNS. sensory innervation to the skin overlying b. Superior Colliuli – visual those muscles. In addition to the major Major regions: reflexes and receive touch and plexuses, the small coccygeal plexus 1. Brainstem auditory input. supplies motor innervation to the muscles 2. Cerebellum ex: of the pelvic floor and sensory cutaneous 3. Diencephalon Turning the head toward a innervation to the skin over the coccyx. 4. Cerebrum tap on the shoulder, a sudden loud noise, or a Brainstem bright flash of light is a Cervical Plexuses C1 to C4. reflex. Branches from this plexus - connects the spinal cord to the - w/ nuclei involved in coordinating eye innervate several of the muscles attached remainder of the brain. movements and controlling pupil to the hyoid bone, as well as the skin of - three parts: diameter and lens shape. the neck and posterior portion of the 1. medulla oblongata - contains Substrancia Nigra (black head. 2. pons substance) - black nuclear mass; part 3. midbrain. of the basal nuclei; involved in Phrenic nerve – innervates the regulating general body diaphragm. Contraction of the diaphragm is - contains several nuclei involved in movements. largely responsible for our ability to vital body functions, such as the - contains ascending tracts from the breathe. control of heart rate, blood spinal cord to the cerebrum and pressure, and breathing. descending tracts from the cerebrum - damage to small areas of the to the spinal cord or cerebellum. Brachial Plexus C5 to T1 brainstem can cause death, whereas Five major nerves emerge from the damage to relatively large areas of the Reticular Formation brachial plexus to supply the upper limb cerebrum or cerebellum often do not. - group of nuclei scattered around the and shoulder. Nuclei for all but the first two cranial brainstem nerves are also located in the - regulates cyclical motor functions, Axillary Nerve – innervates two shoulder brainstem. such as respiration, walking, and muscles and the skin over part of the chewing. shoulder. Medulla Oblongata - major component of the reticular Radial Nerve – innervates all the muscles - most inferior portion of the brainstem activating system – important role in in the posterior arm and forearm as well as and is continuous with the spinal cord. arousing and maintaining the skin over the posterior surface of the - extends superiorly from the level of consciousness and in regulating the arm, forearm, and hand. Lies very close to the foramen magnum to the pons. sleep-wake cycle. the medial side of the humerus in the - contains ascending and descending proximal part of the arm and is susceptible nerve tracts, which convey signals to Ex: to damage in that area. and from other regions of the brain. Stimuli such as a ringing alarm clock, - contains discrete nuclei with specific sudden bright lights, smelling salts, or functions: cold water splashed on the face can Musculocutaneous Nerve (muscle + 1. regulation of heart rate arouse consciousness. skin) – innervates the anterior muscles of 2. blood vessel diameter Conversely, removal of visual or the arm and the skin over the radial surface 3. breathing, swallowing, auditory stimuli may lead to of the forearm. vomiting, drowsiness or sleep. 4. coughing, sneezing, General anesthetics suppress the Ulnar Nerve innervates two anterior 5. balance, coordination reticular activating system. Damage forearm muscles and most of the intrinsic 6. to cells of the reticular formation can hand muscles. It also innervates the skin Pyramids – two prominent enlargement cause coma. over the ulnar side of the hand. The ulnar on the anterior surface of medulla nerve can be easily damaged where it oblongata. It consist of descending nerve Cerebellum a.k.a Little Brain passes posterior to the medial side of the tracts, which transmit action potentials from elbow. The ulnar nerve at this location is the brain to somatic motor neurons of the called the “funny bone.” The median nerve Cerebellar Penducles (pes, foot) – spinal cord and are involved in the innervates most of the anterior forearm several large connections that attached the conscious control of skeletal muscles. muscles and some of the intrinsic hand cerebellum to the brainstem. Routes of muscles. It also innervates the skin over communication bet. cerebellum and other the radial side of the hand. parts of the CNS. Pons - superior to medulla oblangata Lumbosacral Plexus (L1 to S4) - contains ascending and descending Four major nerves exit the lumbrosacral nerve tracts, as well as several nuclei, plexus to supply the lower limb. which some relay information  Diencephalon Each cerebral hemisphere is divided into - sensory tracts cross from one side of lobes the body in the spinal cord or 1. Frontal Lobe – control of voluntary brainstem to the other side of the - bet. brainstem and cerebrum. motor functions, motivation, body. Thus, the left side of the brain - main components: aggression, mood, and olfactory receives sensory input from the 1. thalamus (smell) reception. right side of the body, and vice 2. epithalamus 2. Parietal Lobe – principal center for versa. 3. hypothalamus receiving and consciously perceiving - may also terminate in the brainstem or most sensory information, such as cerebellum. touch, pain, temperature, and Thalamus balance. Spinothalamic Tract – transmits action - largest part of the diencephalon. potentials dealing with sensations such as - consists of a cluster of nuclei Central Sulcus – seperates the pain and temperature to the thalamus and shaped like a yo-yo, with two large, frontal and parietal lobes on to the cerebral cortex. lateral parts connected in the center Dorsal Column – transmits action by a small interthalamic adhesion. 3. Occipital Lobe – functions in potentials dealing with sensations such as - where most sensory input that receiving and perceiving visual input touch, pressure, and proprioception ascends through the spinal cord and and is not distinctly separate from the (body position). brainstem is projected other lobes. Spinocerebellar Tract – transmit - ascending neurons synapse with 4. Temporal Lobe – involved in information about proprioception to the thalamic neurons sending their axons olfactory (smell) and auditory cerebellum. to the cerebral cortex. (hearing) sensations and plays an - influences mood and registers an important role in memory. unlocalized, uncomfortable Psychic Cortex – anterior and perception of pain. inferior portions of temporal lobe Sensory Area of the Cerebral Corte associated with abstract thought and judgment. Epithalamus (epi, upon) - small area superior and posterior to Lateral Fissure – separates temporal - the terms area and cortex are used the thalamus lobe from the rest of the cerebrum. interchangeably. - consists of few small nuclei involved - ascending tracts project to specific in the emotional and visceral 5. Insula – deep within the lateral regions of the cerebral cortex, response to odors fissure. Fifth lobe; involved in the - consist of: perception of taste. sensory fiber > thalamus > cerebral cortex Pineal Gland (pinecone-shaped) - an endocrine gland that may Primary Sensory Areas – area of the influence the onset of puberty cerebral cortex where sensations are - role in controlling some long- SENSORY FUNCTIONS perceived. term cycles that are influenced Primary Somatosensory Cortex by the light-dark cycle CNS constantly receives a variety of stimuli (General Sensory Area) – in the parietal - influence annual behaviors, originating both inside and outside the lobe posterior to the central sulcus. such as migration in birds and body. Sensory fibers color and density change of carrying GENERAL sensory fur in some mammals Sensory input to the brainstem and input, such as pain, pressure, diencephalon: maintain homeostasis. and temperature, synapse in Hypothalamus Input to the cerebrum and cerebellum: the thalamus, and thalamic - most inferior part of the diencephalon keeps us informed about our neurons relay the information to - contains several small nuclei v. environment and allows the CNS to the primary somatosensory important in maintaining homeostasis. control motor functions. cortex. - central role in the control of body Sensory fibers from temperature, hunger, and thirst A small portion of the sensory input results specific parts of the body project - controlsensations such as sexual in perception, the conscious awareness to specific regions of the pleasure, rage, fear, and relaxation of stimuli. primary somatosensory after a meal cortex so that a topographic - emotional responses that seem Ascending Tracts (Sensory) map of the body, with the head inappropriate to the circumstances: most inferior, exists in this part of nervous perspiration or emotional the cerebral cortex. eating - spinal cord and brainstem contain a - Infundibulum (funnel) – extends number of ascending tracts, or Primary Sensory Areas: from the floor of the hypothalamus to pathways. Visual Cortex – occipita the pituitary gland. - transmit information via action Auditory Cortex – temporal potentials from the periphery to Taste Area – insula - plays a major role in controlling the various parts of the brain. Association Areas – adjacent to the primary secretion of hormones from the sensory areas; involved in the process of Pituitary Gland - each tract is specialized; involved recognition. - Mammillary (nipple) Bodies form with a limited type of sensory input, externally visible swellings on the such as pain, temperature, touch, Somatosensory Association Area posterior portion of the hypothalamus. position, or pressure, because each Visual Association Area Involved in emotional responses to tract contains axons from specific Auditory Association Area odors and in memory. specialize sensory receptors Sensory receptor > visual cortex (perceive) - name indicate origin and > visual association area (compare and Cerebrum (brain) termination; w/ prefix spino-, decide) indicating that they begin in the spinal - largest part of the brain. cord. Ex: - most consist of two or three neurons Sensory action potentials originating Longitudinal Fissure – divide cerebrum in sequence, from the periphery to the in the retina of the eye reach the into left & right hemispheres brain. visual cortex, where the image is Gyri (gyrus, gyros, circle) – numerous - almost all neurons relaying perceived. Action potentials then pass folds on the surface of each hemisphere information to the cerebrum from the visual cortex to the visual Sulci (sing. sulcus; furrow or ditch) – terminate in the thalamus. Another association area, where the present intervening grooves; greatly increase the neuron then relays the information visual information is compared to past surface area of the cerebral cortex. from the thalamus to the cerebral visual experience (“Have I seen this cortex. before?”). On the basis of this comparison, the visual association  area “decides” whether the visual 2. Substantia Nigra – group of input is recognized and judges Prefrontal Area – accociation area; where darkly pigmented cells in the whether the input is significant. motivation and foresight to plan and initiate midbrain. If you pass a man walking down a movements occur. Well developed only in - important in planning, organizing, street, you usually pay less attention primates, especially humans. Involved in and coordinating motor movements to him if you’ve never seen him before motivation and regulation of emotional and posture. than if you know him, unless a unique behavior and mood. Large size of this characteristic of the unknown person area in humans may account for our Complex Neural Circuits – link the basal draws your attention. emotional complexity and our relatively nuclei with each other, with the thalamus, well-developed capacity to think ahead and with the cerebral cortex. These SOMATIC MOTOR FUNCTIONS and feel motivated. connections form several feedback loops, some of which are stimulatory and Descending Tracts others inhibitory. Somatic Motor System 1. Stimulators Circuits – - of the brain and spinal cord maintains facilitate muscle activity, the body’s posture and balance, as Corticospinal Tracts – begin in the especially at the beginning of a well as movement of the trunk, head, cerebral cortex and terminate in the spinal voluntary movement, such as limbs, tongue, and eyes. cord. Considered direct because they rising from a sitting position or - allows communication through facial extend directly from upper motor neurons beginning to walk. expressions and speech. in the cerebral cortex to lower motor 2. Inhibitory Circuits – facilitate neurons in the spinal cord. the actions of the stimulatory Involuntary Movement – reflexes circuits by inhibiting muscle mediated through the spinal cord and Other tracts are named after the activity in antagonist muscles. brainstem; occur without conscious part of the brainstem from which they Inhibit random movements of thought. originate. Although they originate in the the trunk and limbs. Inhibitory brainstem, these tracts are indirectly circuits also decrease muscle Voluntary Movements controlled by the cerebral cortex, basal tone when the body, limbs, and - consciously activated to achieve a nuclei, and cerebellum. These tracts are head are at rest. specific goal; though details occur called indirect because no direct automatically. connection exists between the cortical Basal Nuclei Disorders – difficulty rising Ex: and spinal neurons. from a sitting position and difficulty initiating Once you start walking, you walking. Increased muscle tone and don’t have to think about the exaggerated, uncontrolled movements moment-to-moment control of Tracts in the lateral columns – most when they are at rest. Specific feature: every muscle because neural important in controlling goal-directed limb “resting tremor,” a slight shaking of the circuits in the reticular formation movements, such as reaching and hands when a person is not performing and spinal cord automatically manipulating. a task. Parkinson disease, Huntington control your limbs. Lateral Corticospinal Tract – disease, and Cerebral Palsy control speed and precision of - result from the stimulation of neural skilled movements of the hands. Cerebellum circuits consistin of two motor neurons: Tracts in the ventral columns 1. Upper Motor Neurons – have Reticulospinal Tract – maintain - attached by cerebellar peduncles to cell bodies in the cerebral cortex posture, balance, and limb the brainstem. whose axons form descending position through their control of Cerebellar Cortex – composed of tracts that connect to lower neck, trunk, and proximal limb gray matter and has small gyri and motor neurons. muscles. sulci. 2. Lower Motor Neurons – have cell bodies in the ventral horn of - consists of gray nuclei and white the spinal cord gray matter or in How Descending Tract Works nerve tracts cranial nerve nuclei whose - involved in maintaining balance and axons leave the CNS and extend cerebral cortex > brainstem > cross over at muscle tone and in coordinating thru spinal or cranial nerves to pyramid > spinal cord > interneuron to fine motor movement. If the skeletal muscles. It form motor synapse upper to lower motor neuron > cerebellum is damaged, muscle tone units. skeletal muscle fiber decreases, and fine motor movements become very clumsy. Begins in the cerebral cortex and - major function of the cerebellum is Motor Areas of the Cerebral Cortex descends into the brainstem. At the inferior that of a end of the pyramids of the medulla 1. comparator Primary Motor Cortex oblongata, the axons cross over to the 2. participating with the - posterior portion of the frontal lobe, opposite side of the body and continue into cerebrum in learning motor anterior to the central sulcus. the spinal cord. skills - control voluntary movements of skeletal muscles. Crossover of axons in the Comparator – sensing devices; compares - upper motor neuron axons project brainstem or spinal cord to the opposite the data from two sources: motor cortex from specific regions of this cortex to side of the body is typical of descending and peripheral structures. specific parts of the body so that a pathways. Thus, the left side of the brain topographic map of the body exists. controls skeletal muscles on the right side of the body, and vice versa. The ❶ Action potentials from the cerebral Premotor Area – frontal lobe; organized upper motor neuron synapses with motor cortex descend into the spinal cord, motor functions before they are actually interneurons that then synapse with lower synapsing with lower motor neurons to initiated in the primary motor cortex. motor neurons in the brainstem or spinal initiate voluntary movements. Ex: If a person decides to take a cord. The axon of the lower motor neuron ❷ Collateral branches are also sent step, the neurons of the extends to the skeletal muscle fiber. from the motor cortex to the cerebellum, premotor area are first providing information representing the stimulated, and the intended movement. Basal Nuclei determination is made there as ❸ In addition, simultaneously, reaching to which muscles must the cerebellum are action potentials contract, in what order, and to - group of functionally related nuclei. from proprioceptive neurons, which what degree. Action potentials - two primary nuclei are: innervate joints, tendons, and muscles and are then passed to the upper 1. Corpus Striatum – located provide information about the position of motor neurons of the primary deep within the cerebrum body parts. motor cortex, which initiate each ❹ The cerebellum compares planned movement. information about the intended movement from the motor cortex to to repeat a word that you hear involves the 3. Delta Waves – as sleep deepens, sensory information from the moving following sequence of events: progressively more delta waves structures. 1. Action potentials from the ear reach occur; occur during deep sleep, in ❺ If a difference is detected, the the primary auditory cortex, where infants, and in patients with severe cerebellum sends action potentials to the word is perceived. brain disorders. motor neurons in the motor cortex and the 2. The word is recognized in the 4. Theta Waves – are usually observed spinal cord to correct the discrepancy. auditory association area and in children, but they can also occur in comprehended in portions of the adults who are experiencing The result of the cerebellar sensory speech area. frustration or who have certain brain comparator function is smooth and 3. Action potentials representing the disorders. coordinated movements. word are then conducted through nerve tracts that connect the sensory Neurologists use these patterns to Ex: If you close your eyes, the cerebellar and motor speech areas. diagnose and determine the treatment comparator function allows you to touch 4. In the motor speech area, the for the disorders. your nose smoothly and easily with your muscle activity needed to repeat the finger. If the cerebellum is not functioning, word is determined. Memory your finger tends to overshoot the target. 5. Action potentials then go to the premotor area, where the movements are programmed. Three division of storing memory: Alcohol - inhibits the function of the 6. Finally, action potentials are 1. Working cerebellum. conducted to the primary motor – brain briefly stores information Another function of the cortex, where specific movements required for the immediate are triggered. performance of a task. cerebellum involves participating with the – lasts only a few seconds to cerebrum in learning motor skills, such as Speaking a written word involves a slightly minutes and occurs mostly in the playing the piano. Once the cerebrum and cerebellum “learn” these skills, the different pathway: frontal cortex specialized movements can be 1. The information enters the visual – limited by the number of bits of cortex, then passes to the visual information (about seven) that accomplished smoothly and automatically. association area, where it is can be stored at any one time. OTHER BRAIN FUNCTIONS recognized. 2. The information continues to the When new information is presented, sensory speech area, where it is old information, previously stored in Communication Between the Righ understood and formulated as it is to working memory, is eliminated. What and Left Hemisphere be spoken. From the sensory speech happens to a telephone number you just area, it follows the same route for looked up if you are distracted? Right Cerebral Hemisphere receives repeating words that you hear: sensory input from and controls muscular 3. through nerve tracts to the motor 2. Short-term activity in the left half of the body. speech area, – lasts longer than working Left Cerebral Hemisphere receives input 4. to the premotor area, memory from and controls muscles in the right half 5. and then to the primary motor – retained for a few minutes to a of the body. cortex. few days. – stored by a mechanism involving Commissures (joining together) – increased synaptic transmission. Brain Waves and Consciousness – susceptible to brain trauma, connection enabling sensory information received by one hemisphere to be shared such as physical injury or with the other. diff. levels of consciousness = diff. patterns decreased oxygen, and to of electrical activity in the brain. certain drugs that affect neural Corpus Callosum – largest commissures; function, such as general a broad band of nerve tracts at the base of Electrodes – when placed on a person’s anesthetics. the longitudinal fissure. scalp and attached to a recording device can record the brain’s electrical activity, 3. Long-term Language & other functions, producing an electroencephalogram – transferred to long-term memory, such as artistic activities, are not shared (EEG). where it may be stored for only a equally between the two hemispheres. few minutes or become These electrodes are not permanent, by consolidation, a Researchers believe: positioned so that they can detect gradual process involving the Left Hemisphere – more analytical individual action potentials, but they can formation of new and stronger hemisphere; mathematics and speech detect the simultaneous action synaptic connections. Right Hemisphere – three-dimensional or potentials in large numbers of neurons. – length of time memory is stored: spatial perception and musical ability Most of the time, EEG patterns depend on how often it is are irregular, with no particular pattern, retrieved and used Speech because the brain’s electrical activity is – further subdivided based on the normally not synchronous. type of the memory: At other times, however, EEG a. Declarative a.k.a Explicit - located in the left cerebral cortex. patterns can be detected as wavelike Memory – retention of facts, patterns known as Brain Waves. such as names, dates, and Two major cortical areas involved in places, as well as related speech: Brain Waves – intensity and frequency emotional undertones. Emotion 1. Sensory Speech Area (Wernicke differ, based on the state of brain activity. and mood apparently serve as Area) – parietal lobe; understanding gates in the brain and determine and formulating coherent speech The different levels of consciousness in what is stored in long-term 2. Motor Speech Area (Broca Area) – an awake and a sleeping person are declarative memory. frontal lobe; movement necessary for marked by different types of brain b. Procedural a.k.a Reflexine speech waves. Memory – development of motor 1. Alpha Waves – observed in a normal skills, such as riding a bicycle. Aphasia (a-, without; phasis, speech) – person who is awake but in a quiet, Only a small amount of absent or defective speech or language resting state with the eyes closed. procedural memory is lost over comprehension; results from damage to 2. Beta Waves – higher frequency than time. these part of the brain or associated brain alpha waves and occur during region. Common cause: stroke, 25–40% of intense mental activity. During the - involves structural and functional stroke survivors exhibit aphasia. beginning of sleep, a rapid transition changes in neurons that lead to takes place from a beta rhythm to an long-term enhancement of synaptic Speech-related functions involve both alpha rhythm. transmission. sensory and motor pathways. For example, Memory Engrams a.k.a Memory Traces – Ex: Pressure on the portion of the right aqueduct > fourth ventricle > subarachnoid whole series of neurons; involved in the primary motor cortex involved in hand space > (some) central canal of spinal cord long-term retention of a given piece of movements can cause decreased function > blood information, a thought, or an idea. in the left hand. The frontal lobe is also Repeating the information and involved with mood; thus, pressure in that ❶ CSF is produced by the choroid associating it with existing memories help area can result in mood changes—for plexuses of the ventricles. us transfer information from short-term example, a normally happy person may ❷ The CSF flows from the lateral to long-term memory. become irritable. Subdural hematoma is ventricles into the third ventricle. more common in people over age 60 ❸ CSF then flows through the cerebral Limbic (bounary) System and because their veins are less resilient and aqueduct into the fourth ventricle. Emotions more easily damaged. ❹ The CSF exits the fourth ventricle through small openings in its walls and roof Limbic System Arachnoid (spiderlike) Mater and enters the subarachnoid space. A - group of olfactory cortex and certain - very thin, wispy. small amount of CSF enters the central deep cortical regions and nuclei of the - Subdural Space – space bet. dura canal of the spinal cord. cerebrum and the diencephalon mater and arachnoid mater. Normally ❺ Masses of arachnoid tissue, called - influences long-term declarative only a potential space containing a arachnoid granulations, penetrate the memory, emotions, visceral very small amount of serous fluid. superior sagittal sinus, a dural venous responses to emotions, motivation, sinus in the longitudinal fissure, and CSF and mood. Spinal cord extends only to second passes from the subarachnoid space into - Olfactory Nerves – major source of lumbar vertebra. Spinal nerves surrounded the blood through these granulations. sensory input to the limbic system. by meninges extend to the end of the - responds to olfactory stimulation by vertebral column. Because there is no Hydrocephalus – blockage of the openings initiating responses necessary for spinal cord in the inferior portion of the in the fourth ventricle or the cerebral survival, such as hunger and thirst. vertebral canal, a needle can be aqueduct can causing CSF to accumulate - connected to, and functionally introduced into the subarachnoid space at in the ventricles > creates increased associated with, the hypothalamus. that level without damaging the spinal cord. pressure that dilates the ventricles and Health professionals use such a needle to compresses the brain tissue, which Lesions in the limbic system can inject anesthetic into the area as a spinal usually results in irreversible brain result in voracious appetite, increased block or to take a sample of cerebrospinal damage. If the skull bones are not (often perverse) sexual activity, and fluid in a spinal tap. The cerebrospinal fluid completely ossified when the docility (including loss of normal fear and can then be examined for infectious agents hydrocephalus occurs, as in a fetus or anger responses). (meningitis) or for blood (hemorrhage). newborn, the pressure can also cause severe enlargement of the head. MENINGES, VENTRICLE, AND Pia Mater (affectionate mother) Hydrocephalus is treated by placing a CEREBROSPINAL FLUID - very tightly bound to the surface of the drainage tube (shunt) from the ventricles to brain and spinal cord. the abdominal cavity to eliminate the high Meninges (membrane) - Subarachnoid Space – bet. internal pressures. arachnoid mater and pia mater. Filled with cerebrospinal fluid and contains Three connective tissue CRANIAL NERVES blood vessels. membranes, meninges, surround and protect the brain and spinal cord. Includes: Two general categories of cranial nerve 1. Dura Mater Ventricles function: sensory and motor. 2. Arachnoid Mater A. Sensory Functions 3. Pia Mater - in the CNS a. special senses – vision - fluid-filled cavities; may be small or b. general senses – touch large and pain in the face Dura Mater (tough mother) B. Motor functions - most superficial and thickest Lateral Ventricle – large cavity in cerebral a. somatic motor – innervate - adheres tightly to the cranial bones. hemisphere skeletal muscles in the - Epidural Space – located within the Third Ventricle – smaller in center of head and neck vertebral canal bet. dura mater and dienphalon bet. two halves of the thalamus b. parasympathetic – the vertebrae. innervate glands, smooth - the injection site for epidural Foramina (holes) – connect third ventricle muscle throughout the anesthesia of the spinal nerves, often to lateral ventricle. body, and cardiac muscle of given during childbirth. the heart - consists of two layers, mostly in Fourth Ventricle – base of the cerebellum. contact but in some areas separate to Continuous with the central canal of the form: spinal cord. Opens into the subarachnoid Cranial nerves: w/ sensory neurons, a. Dural Folds — extends space through foramina in its walls and somatic motor neurons, and into the longitudinal fissure roof. parasympathetic neurons of the ANS. bet. two cerebral hemispheres and bet. Cerebral Aqueduct – narrow canal; Sensory Only cerebrum and cerebellum. connect fourth ventricle to the third 1. Olfactory Help hold the brain in ventricle. 2. Optic place within the skull. 3. Vestibulococklear Nerves b. Dural Venous Sinuses – Cerebrospinal Fluid (CSF) collect blood from the small Somatic Motor Only (although these motor veins of the brain and nerves do provide proprioceptive - bathes the brain and spinal cord, empty into the internal information) providing a protective cushion jugular veins, which exit the 1. Trochlear around the CNS. skull. 2. Abducens - fills the brain ventricles, the central canal of the spinal cord, and the 3. Accessory Damage to the veins crossing 4. Hypoglossal Nerves subarachnoid space between the cerebral cortex and the dural venous sinuses can cause bleeding Both Sensory and Somatic Motor Choroid (lacy) Plexuses – produces the into the subdural space, resulting in a Functions CSF. These plexuses are specialized subdural hematoma, which can put 1. Trigenimal Nerve – has the structures located in the ventricles and pressure on the brain. The pressure can greatest general sensory composed of ependymal cells. result in decreased brain function in the distribution. Only cranial nerve affected area. supplying sensory information to choroid plexuses (produces) > lateral ventricle > third ventricle > cerebral  the brain from the skin of the Anatomy of the Sympathetic neurotransmitters from activating their face. Division target tissues. Sensory information Sympathetic Preganglionic Neurons Functions of the Autonomic from the skin over the rest of the Cell Bodies – are in the lateral horn of the Nervous System body is carried to the CNS by spinal cord gray matter bet. T1 to L2 spinal nerves. Injections of segments. The sympathetic (fight-or-flight) division of anesthetic by a dentist are Axons of the preganglionic neurons exit the autonomic nervous system prepares a designed to block sensory through ventral roots and project to either person for physical activity (table 8.8). transmission through branches sympathetic chain ganglia or collateral These actions include increasing heart rate of the trigeminal nerve from the ganglia. and blood pressure, dilating respiratory teeth. These dental branches of