Anatomy and Physiology of the Body Systems with Medical Terminology PDF

Anatomy and Physiology of the Body Systems with Medical Terminology 1ST SEMESTER (A.Y. 2023-2024) Daniel Dominick G. Te, MSPT, PTRP, PT THE NERVO...

Anatomy and Physiology of the Body Systems with Medical Terminology 1ST SEMESTER (A.Y. 2023-2024) Daniel Dominick G. Te, MSPT, PTRP, PT THE NERVOUS SYSTEM Nerve Physiology OVERVIEW OF THE NERVOUS SYSTEM Organization of the Nervous System Nervous system is one of the smallest and yet the most complex of the 11 body systems. Neurology - deals with normal functioning and disorders of the nervous system Neurologist - a physician who diagnoses and treats disorders of the nervous system I. Central Nervous System (CNS) - brain and spinal cord II. Peripheral Nervous System (PNS) - spinal nerves, cranial nerves Nerve - a bundle of hundreds to thousands of axons plus associated connective tissue and blood vessels that lie outside the brain and spinal cord; 31 pairs of SN and 12 pairs of CN Sensory Receptor - refers to a structure of the nervous system that monitors changes in the external or internal environment Two divisions: Sensory Division - or afferent division - conveys input into the CNS from sensory receptors in the body - division provides the CNS with sensory information about the somatic senses (tactile, thermal, pain, and proprioceptive sensations) and special senses (smell, taste, vision, hearing, and equilibrium) Motor Division - or efferent division - conveys output from the CNS to effectors (muscles and glands) - subdivisions: Somatic Nervous System (SNS) - conscious control / voluntary - conveys output from the CNS to skeletal muscles only Autonomic Nervous System (ANS) - involuntary - conveys output from the CNS to smooth muscle, cardiac muscle, and glands - Two main branches: Sympathetic Nervous System - “fight or flight” Parasympathetic Nervous System - “rest and digest”  Enteric Nervous System - confined to the wall of the gastrointestinal (GI) tract Functions of the Nervous System 1. Sensory function - detect internal stimuli, such as an increase in blood pressure, or external stimuli (aka. sensing changes) 2. Integrative function - processes sensory information by analyzing it and making decisions for appropriate responses—an activity known as integration (aka. interpreting them) 3. Motor function - may elicit an appropriate motor response by activating effectors (muscles and glands) through cranial and spinal nerves (aka. motor function) HISTOLOGY OF NERVOUS TISSUE Nervous tissue comprises two types of cells—neurons and neuroglia. I. Neurons - nerve cells that possess electrical excitability Stimulus - any change that initiates an action potential Action potential - nerve impulse Parts of a Neuron 1. Cell Body - perikaryon or soma, contains a nucleus surrounded by cytoplasm that includes typical cellular organelles such as lysosomes, mitochondria, and a Golgi complex Nissl bodies - free ribosomes and prominent clusters of rough endoplasmic reticulum Neurofibrils - in the cytoskeleton; composed of bundles of intermediate filaments that provide the cell shape and support Microtubules - in the cytoskeleton; assist in moving materials between the cell body and axon Lipofuscin - yellowish-brown pigment in the cytoplasm Ganglion - collection of neuron cell bodies outside the CNS Nerve fiber - a general term for any neuronal process (extension) that emerges from the cell body of a neuron. 2. Dendrites - receive signals 3. Axon - send signals Axon hillock - axon is a long, thin, cylindrical projection that oft en joins to the cell body at a cone-shaped elevation Initial segment - part of the axon closest to the axon hillock Trigger zone - an area where nerve impulses arise at the junction of the axon hillock and the initial segment Axoplasm - cytoplasm of an axon Axolemma - plasma membrane surrounding the axoplasm Axon collaterals - side branches that may branch off, typically at a right angle to the axon Axon terminals - axon and its collaterals end by dividing into many fine processes Synapse - site of communication between two neurons or between a neuron and an effector cell Synaptic end bulbs - tips of some axon terminals swell into bulb-shaped structures Varicosities - others exhibit a string of swollen bumps Synaptic vesicles - both synaptic end bulbs and varicosities contain many tiny membrane-enclosed sacs Neurotransmitter - a molecule released from a synaptic vesicle that excites or inhibits another neuron, muscle fiber, or gland cell Two types of transport systems: 1. Slow axonal transport - moves materials about 1–5 mm per day (anterograde/forward) - conveys axoplasm in one direction only—from the cell body toward the axon terminals - supplies new axoplasm to developing or regenerating axons and replenishes axoplasm in growing and mature axons 2. Fast axonal transport - moves materials at 200-400m per day (anterograde/forward & retrograde/retrograde) - moves materials in both directions—away from and toward the cell body Structural Classification of Neurons: 1. Multipolar neurons - have several dendrites and one axon 2. Bipolar neurons - one main dendrite and one axon 3. Unipolar neurons - have dendrites and one axon that are fused together to form a continuous process that emerges from the cell body. These neurons are more appropriately called pseudounipolar neurons because they begin in the embryo as bipolar neurons. Functional Classification of Neurons: 1. Sensory neurons - afferent neurons; either contain sensory receptors at their distal ends (dendrites) or are located just after sensory receptors that are separate cells. 2. Motor neurons - efferent neurons; convey action potentials away from the CNS to effectors (muscles and glands) in the periphery (PNS) through cranial or spinal nerves 3. Interneurons - association neurons; mainly located within the CNS between sensory and motor neurons, and integrate (process) incoming sensory information from sensory neurons and then elicit a motor response by activating the appropriate motor neurons. II. Neuroglia - structural support of the nervous system Gliomas - brain tumors derived from glia tend to be highly malignant and to grow rapidly CNS: Astrocytes - star-shaped; largest and most numerous Protoplasmic astrocytes - have many short branching processes and are found in gray matter Fibrous astrocytes - have many long unbranched processes and are located mainly in white matter Functions: 1. Astrocytes contain microfilaments that give them considerable strength, which enables them to support neurons. 2. endothelial cells create a blood–brain barrier, which restricts the movement of substances between the blood and interstitial fluid of the CNS. 3. In the embryo, astrocytes secrete chemicals that appear to regulate the growth, migration, and interconnection among neurons in the brain. 4. Astrocytes help to maintain the appropriate chemical environment for the generation of nerve impulses. 5. Astrocytes may also play a role in learning and memory by influencing the formation of neural synapses Microglia - microglial cells function as phagocytes/WBC Ependymal cells - produce cerebrospinal fluid; line the ventricles of the brain and central canal of the spinal cord Oligodendrocytes - produce myelin; responsible for forming and maintaining the myelin sheath around CNS axons  *Myelin sheath - a multilayered lipid and protein covering around some axons that insulates them and increases the speed of nerve impulse conduction. PNS: Schwann cells - produce myelin; encircle PNS axons; a sincle cell can enclose as many as 20 or more unmyelinated axons (axons that lack a myelin sheath) Satellite cells - regulate exchange of materials (neuronal cell bodies and interstitial fluid); flat cells that surround the cell bodies of neurons of PNS ganglia Myelination Axons can either be myelinated or unmyelinated. Neurolemma - outer layer of the Schwann cell, which encloses the myelin sheath Nodes of Ranvier - gaps in the myelin sheath appear at intervals along the axon Collections of Nervous Tissue Cluster of Neuronal Cell Bundle of Axons Gray and White Matter Bodies White matter - contains of Ganglion - cluster of neuronal Nerve - bundle of axons in the aggregates of myelinated cell bodies in the PNS PNS axons Gray matter - contains cell bodies, dendrites, and axon Nucleus - cluster of neuronal Tract - bundle of axons in the terminals of neurons, cell bodies in the CNS CNS unmyelinated axons, and neuroglia  ELECTRICAL SIGNALS IN NEURONS: AN OVERVIEW Graded Potentials - short-distance communication Action Potentials - long-distance communication Process: 1. As you touch the pen, a graded potential develops in a sensory receptor in the skin of the fingers. 2. The graded potential triggers the axon of the sensory neuron to form a nerve action potential, which travels along the axon into the CNS and ultimately causes the release of neurotransmitter at a synapse with an interneuron 3. The neurotransmitter stimulates the interneuron to form a graded potential in its dendrites and cell body. 4. The nerve action potential travels along the axon, which results in neurotransmitter release at the next synapse with another interneuron. 5. Once interneurons in the cerebral cortex, the outer part of the brain, are activated, perception occurs and you are able to feel the smooth surface of the pen touch your fingers. 6. A stimulus in the brain causes a graded potential to form in the dendrites and cell body of an upper motor neuron, a type of motor neuron that synapses with a lower motor neuron farther down in the CNS in order to contract a skeletal muscle. The graded potential subsequently causes a nerve action potential to occur in the axon of the upper motor neuron, followed by neurotransmitter release 7. The neurotransmitter generates a graded potential in a lower motor neuron, a type of motor neuron that directly supplies skeletal muscle fibers. The graded potential triggers the  formation of a nerve action potential and then release of the neurotransmitter at neuromuscular junctions formed with skeletal muscle fibers that control movements of the fingers. 8. The neurotransmitter stimulates the muscle fibers that control finger movements to form muscle action potentials. The muscle action potentials cause these muscle fibers to contract, which allows you to write with the pen. Membrane potential - an electrical potential difference (voltage) across the membrane Resting membrane potential - voltage in excitable cells Current - flow of charged particles  Ion Channels Electrochemical gradient - a concentration (chemical) difference plus an electrical difference RESTING MEMBRANE POTENTIAL Resting Membrane Potential - exists because of a small buildup of negative ions in the cytosol along the inside surface of the membrane, and an equal buildup of positive ions in the extracellular fluid along the outside surface of the membrane - Such separation of positive and negative electrical charges is a form of potential energy, measured in volts or millivolts (mV) - RMP in neurons: -40 to -90mV (typical -70 mV) - A cell that exhibits a membrane potential is said to be polarized. Electrodes - devices that conduct electrical charges. Voltmeter -the recording microelectrode and the reference electrode which detects the electrical difference (voltage) across the plasma membrane. Major Factors: 1. Unequal distribution of ions in the ECF and cytosol 2. Inability of most cytosolic anions to leave the cell 3. Electrogenic nature of the Na+/K+ ATPases GRADED POTENTIALS Graded Potential Hyperpolarizing graded potential - makes - a small deviation from the resting membrane the membrane potential more negative (more potential that makes the membrane either polarized) more polarized (inside more negative) or less Depolarizing graded potential - makes the polarized (inside less negative) membrane potential less negative (less - Vary in amplitude, depending on the strength polarized) of the stimulus - Most graded potentials occur in the dendrites Decremental conduction - mode of travel by and cell bodies which graded potentials die out as they spread - occurs when a stimulus causes along the membrane mechanically-gated or ligand-gated channels Summation - process by which graded to open or close in an excitable cell’s plasma potentials add together membrane ACTION POTENTIALS Action Potential (AP) - or impulse is a Hyperpolarization - after-hyperpolarizing sequence of rapidly occurring events that phase; temporarily becomes more negative decrease and reverse the membrane potential than the resting level and then eventually restore it to the resting state Threshold - cut-off for depolarization to occur (about -55 mV in neurons) Phases: Subthreshold stimulus - AP will not occur Depolarization - depolarizing phase; Threshold stimulus - AP will occur membrane potential becomes positive Suprathreshold stimulus - several AP will Repolarization - repolarizing phase; form membrane potential is restored to resting state All or None Principle Propagation of Action Potentials - an AP either occurs completely, or it does not Propagation - AP keeps it strength as it occur at all spreads along the membrane, and it depends - an action potential is generated in response on positive feedback to a threshold stimulus but does not form when there is a subthreshold stimulus Two types of Propagation: 1. Continuous Conduction - propagation of Depolarization Phase AP that occurs along myelinated axons Voltage-gated Na+ channels open rapidly 2. Saltatory Conduction - occurs in Influx of Na+ causes the depolarizing unmyelinated axons and in muscle fiber phase of the action potential Inflow of Na+ changes the membrane Factors That Affect the Speed of potential from -55 mV to +30mV Propagation 1. Amount of myelination Repolarization Phase 2. Axon diameter Voltage-gated Na+ channels are closed 3. Temperature Voltage-gated K+ channels open slowly, causing outflows of K+ ions Classification of Nerve Fibers Sodium-potassium pump 1. A fibers - Largest diameter of myelinated axons Refractory Period - Associated with touch, pressure, position Period of time after an action potential begins of joints, some thermal and pain during which an excitable cell cannot generate sensations, and motor neurons of another action potential in response to a skeletal muscle normal threshold stimulus 2. B fibers Absolute refractory period - even a very - Myelinated axons strong stimulus cannot initiate a second - Constitute autonomic motor neurons action potential 3. C fibers Relative refractory period - period of time during which a second action potential can - Smallest diameter of unmyelinated axons be initiated, but only by a larger-than normal - Associated with pain, touch, pressure, stimulus heat and cold, and autonomic motor fibers to the heart, smooth muscles, and glands  SIGNAL TRANSMISSION AT SYNAPSES Gap junctions are common in visceral smooth muscle, cardiac muscle, and the developing embryo. Synapse - a region where communication Advantages: occurs between two neurons or between a 1. Faster communication neuron and an effector cell 2. Synchronization Presynaptic neuron - refers to a nerve cell that carries a nerve impulse toward a synapse or the cell that sends a signal Chemical Synapses Postsynaptic cell - cell that receives a signal Neurons are close, but do not touch Separated by the synaptic cleft Postsynaptic neuron - carries a nerve Uses neurotransmitters for communication impulse away from a synapse between cells Effector cell - responds to the impulse at the Postsynaptic potential - a type of graded synapse potential produced when postsynaptic neuron receives the chemical signal Axodendritic - from axon to dendrite Axosomatic - from axon to cell body Structure of Neurotransmitter Receptors Axoaxonic - from axon to axon Ionotropic Receptors - type of ligand-gated channel that has a neurotransmitter binding site Electrical Synapses and an ion channel Action potentials (impulses) conduct directly Metabotropic Receptors - contains a between the plasma membranes of adjacent neurotransimitter binding site but lacks an ion neurons through structures called gap channel junctions  Removal of Neurotransmitter 1. Diffusion 2. Enzymatic degradation 3. Uptake by cells Spatial and Temporal Summation of Postsynaptic Potentials Spatial summation - summation of postsynaptic potentials in response to stimuli that occur at different locations in the membrane of a postsynaptic cell at the same time Temporal summation - summation of postsynaptic potentials in response to stimuli that occur at the same location in the membrane of the postsynaptic cell but at different times NEUROTRANSMITTERS 1. Small-molecule neuropeptides (acetylcholine, amino acids, biogenic amines, ATP and other purines, nitric oxide, and carbon monoxide) Excitatory Inhibitory Excitator & Inhibitory Glutamate - brain synapses Gamma aminobutyric Acetylcholine - ionotropic acid (GABA) - CNS or metabotropic receptors Aspartate Glycine Norepinephrine - arousal, dreaming, and mood ATP and other purines - both Epinephrine CNS and PNS Nitric oxide - brain, spinal cord, Dopamine - emotional adrenal glands, and nerves to the responses, addictive penis behaviors, and pleasurable experiences Carbon monoxide - vasodilation, Serotonin - sensory memory, olfaction, vision, reception, temperature thermoregulation, insulin release, regulation, mood, control, and anti-inflammatory appetite, and sleep 2. Neuropeptides (3-40 amino acids linked by peptide bonds)  NEURAL CIRCUITS The CNS contains billions of neurons organized into complicated networks called neural circuits, functional groups of neurons that process specific types of information. 1. Simple Series Circuit - presynaptic neuron stimulates a single postsynaptic neuron 2. Diverging Circuit - nerve impulse from a single presynaptic neuron causes the stimulation of increasing numbers of cells along the circuit Divergence - a single presynaptic neuron may synapse with several postsynaptic neurons; permits one presynaptic neuron to influence several postsynaptic neurons (or several muscle fibers or gland cells) at the same time 3. Converging Circuit - postsynaptic neuron receives nerve impulses from several different sources Convergence - several presynaptic neurons synapse with a single postsynaptic neuron 4. Reverberating Circuit - the incoming impulse stimulates the first neuron, which stimulates the second, which stimulates the third, and so on. Branches from later neurons synapse with earlier ones 5. Parallel after-discharge circuit - a single presynaptic cell stimulates a group of neurons, each of which synapses with a common postsynaptic cell. REGENERATION AND REPAIR OF NERVOUS TISSUE Plasticity - capability to change and adapt Regeneration - capability to replicate or repair damaged neurons CNS Neurogenesis - birth of new neuron from undifferentiated stem cells; in the CNS PNS: Chromatolysis - alteration where in Nissl bodies break up into fine granulations about 28 to 28 hours after injury to a process of a normal peripheral neuron Wallerian de-generation - degeneration of the distal portion of the axon and myelin sheath Regeneration tube - guides growth of a new axon from the proximal area across the injured area into the distal area previously occupied by the original axon  Anatomy and Physiology of the Body Systems with Medical Terminology 1ST SEMESTER (A.Y. 2023-2024) Daniel Dominick G. Te, MSPT, PTRP, PT THE NERVOUS SYSTEM Neuroanatomy SPINAL CORD ANATOMY Protective Structures I. Vertebral Column II. Meninges: 1. Dura mater - Most superficial - a thick strong layer composed of dense irregular connective tissue - forms a sac from the level of the foramen magnum in the occipital bone, where it is continuous with the meningeal dura mater of the brain, to the second sacral vertebra 2. Arachnoid mater - Middle of the meningeal membranes - a thin, avascular covering comprised of cells and thin, loosely arranged collagen and elastic fiber - spider’s web arrangement of delicate collagen fibers and some elastic fibers - Subdural space - interstitial fluid between the dura mater and the arachnoid mater 3. Pia mater - Innermost meninx - a thin transparent connective tissue layer that adheres to the surface of the spinal cord and brain - Denticulate ligaments - thickenings of the pia mater - Subarachnoid space - shock-absorbing cerebrospinal fluid between the arachnoid mater and pia mater  External Anatomy of the Spinal Cord Spinal Cord - roughly oval in shape, being flattened slightly anteriorly and posteriorly - begins as a continuation of the medulla oblongata and ends at about the second lumbar vertebra in an adult - contains cervical and lumbar enlargements that serve as points of origin for nerves to the limbs: Cervical Enlargement - superior enlargement from the fourth cervical Lumbar Enlargement - inferior enlargement from the ninth to the twelfth thoracic vertebra Conus Medullaris - inferior to the lumbar enlargement, the spinal cord terminates as a tapering, conical structure Filum Terminale - arising from the conus medullaris is an extension of the pia mater that extends inferiorly, fuses with the arachnoid mater, and dura mater, and anchors the spinal cord to the coccyx Spinal Nerves - paths of communication between the spinal cord and specific regions of the body - Part of the PNS, with parallel bundles of axons and neuroglial cells - Roots - two bundles of axons that connect each spinal nerve to a segment of the cord by even smaller bundles of axons called rootlets: Posterior or dorsal root - contains sensory axons (afferent) Anterior or ventral root - contains motor neuron axons (efferent) Cauda Equina - which means “horse’s tail” is the roots of these lower spinal nerves angle inferiorly alongside the filum terminale in the vertebral canal like wisps of hair - The adult human body has 31 pairs of spinal nerves: C1-C7 (8 pairs) L1-L5 (5 pairs) Coccyx (1 pair) T1-T12 (12 pairs) S1-S5 (5 pairs) Internal Anatomy of the Spinal Cord Two grooves penetrate the white matter of the spinal cord and divide it into right and left sides: Anterior median fissure - a wide groove on the anterior (ventral) side Posterior median sulcus - a narrow furrow on the posterior (dorsal) side Gray commissure - forms the crossbar of the H Central canal - center of the gray commissure is a small space that extends the entire length of the spinal cord and is filled with cerebrospinal fluid Anterior white commissure - anterior to the gray commissure which connects the white matter of the right and left sides of the spinal cord Nuclei - in the gray matter of the spinal cord and brain, clusters of neuronal cell bodies form functional groups Gray matter in the spinal cord is divided into horns: Horns - gray matter on each side of the spinal cord is subdivided into regions Posterior gray horns - contain axons of incoming sensory neurons as well as cell bodies and axons of interneurons  Anterior gray horns - contain somatic motor nuclei, which are clusters of cell bodies of somatic motor neurons that provide nerve impulses for contraction of skeletal muscles Lateral gray horns - between the posterior and anterior gray horns which are present only in thoracic and upper lumbar segments of the spinal cord; contain autonomic motor nuclei, which are clusters of cell bodies of autonomic motor neurons that regulate the activity of cardiac muscle, smooth muscle, and glands The white matter into columns: 1. Anterior white columns 2. Posterior white columns 3. Lateral white columns Tracts - bundles, which may extend long distances up or down the spinal cord Sensory tracts - consist of axons that conduct nerve impulses toward the brain Motor tracts - consisting of axons that carry nerve impulses from the brain The internal organization of the spinal cord allows sensory input and motor output to be processed by the spinal cord in the following way:  SPINAL NERVES Associated with the spinal cord Part of the PNS,with parallel bundles of axons and neuroglial cells The human body has 31 pairs of spinal nerves Mixed nerve - posterior root contains sensory axons and the anterior root contains motor axons Connective Tissue Coverings of Spinal Nerves 1. Endoneurium - innermost layer that consists of a mesh of collagen fibers, fibroblasts, and macrophages 2. Perineurium - middle layer that consists of up to 15 layers of fibroblasts within a network of collagen fibers 3. Epineurium - outermost layer that consists of fibroblasts and thick collagen fibers Distribution of Spinal Nerves Branches - consists of fibroblasts and thick collagen fibers 1. Anterior rami - serves the muscles and structures of the upper and lower limbs and the skin of the lateral and anterior surfaces of the trunk 2. Posterior rami - serves the deep muscles and skin of the posterior surface of the trunk 3. Meningeal branch - reenters the vertebral cavity through the intervertebral foramen and supplies the vertebrae, vertebral ligaments, blood vessels of the spinal cord, and meninges Plexuses - networks of peripheral nerves 1. Cervical plexus 2. Brachial plexus 3. Lumbar plexus 4. Sacral plexus Intercostal Nerves - or thoracic nerves; anterior rami of nerves T2–T12 do not form plexuses Dermatomes The skin over the entire body is supplied by somatic sensory neurons that carry nerve impulses from the skin into the spinal cord and brain. The area ofthe skin that provides sensory inputto the CNS via one pair of spinal nerve. Myotomes Muscle or groups of muscle supplies by one pair of spinal nerve Myotome Action Muscles C5 Shoulder abduction and Deltoids, supraspinatus,teresminor, lateral rotation infraspinatus C6 Elbow flexion,wrist extension Biceps brachii, brachialis,wrist extensors C7 Elbow extension,wrist flexion Triceps brachii, anconeus,wrist flexors C8 Wrist ulnar deviation,finger Flexor carpi ulnaris, extensor carpi ulnaris, flexion flexor digitorum profundus,flexor pollicis longus T1 Finger abduction and Extensor digitorum, dorsal interossei, extension lumbricals L2 Hip flexion Iliopsoas, sartorius,tensorfascia latae, pectineus L3 Knee extension Quadriceps femoris L4 Ankle dorsiflexion Tibialis anterior, extensor digitorum longus L5 Big toe extension Extensor hallucis longus, extensor hallucis brevis S1 Ankle plantarflexion and Gastrocnemius, soleus, tibialis posterior, eversion peroneus longus, peroneus brevis  CERVICAL PLEXUS - Formed by the roots (anterior rami) of the first four cervical nerves (C1–C4), with contributions from C5 - Nerves of the cervical plexus supply the skin and muscles of the head, neck, and upper part of the shoulders; they connect with some cranial nerves and innervate the diaphragm BRACHIAL PLEXUS - The roots (anterior rami) of spinal nerves C5–C8 and T1 - Extends inferiorly and laterally on either side of the last four cervical and first thoracic vertebrae - Nerves of the brachial plexus supply the upper limbs and several neck and shoulder muscles. LUMBAR PLEXUS - The roots (anterior rami) of spinal nerves L1–L4 - Nerves of the lumbar plexus supply the anterolateral abdominal wall, external genitals, and part of the lower limbs.  SACRAL AND COCCYGEAL PLEXUSES - The roots (anterior rami) of spinal nerves L1–L5 and S1–S4 form the sacral plexus - Nerves of the sacral plexus supply the buttocks, perineum, and part of the lower limbs - The roots (anterior rami) of the spinal nerves S4–S5 and the coccygeal nerves form the coccygeal plexus - Nerves of the coccygeal plexus supply the skin of the coccygeal region  SPINAL CORD PHYSIOLOGY Sensory and Motor Tracts Lateral reticulospinal Medial reticulospinal tracts Sensory tracts - ascending tracts Posterior column - convey nerve impulses Reflexes and Reflex Arcs for touch, pressure, vibration, and conscious Reflex - a fast, involuntary, unplanned proprioception sequence of actions that occurs in response to Spinothalamic tract - conveys nerve a particular stimulus impulses for sensing pain, temperature, itch, Reflexes may be spinal or cranial and somatic and tickle or autonomic (visceral): Motor tracts - descending tracts Spinal reflex - integration takes place in the Direct motor pathways - pyramidal spinal cord gray matter pathways; convey nerve impulses that Cranial reflex - integration occurs in the originate in the cerebral cortex and are brainstem rather than the spinal cord, destined to cause voluntary movements of Somatic reflexes - involve contraction of skeletal muscles skeletal muscles Lateral corticospinal Autonomic reflexes - involve responses of Anterior corticospinal smooth muscle, cardiac muscle, and glands Corticobulbar tracts Indirect motor pathways - extrapyramidal Reflex arc - pathway followed by nerve pathways; convey nerve impulses from the impulses that produce a reflex brainstem to cause automatic movements Components: and help coordinate body movements with visual stimuli 1. Sensory receptor 2. Sensory neuron Rubrospinal 3. Integrating center Tectospinal 4. Motor neuron 5. Effector  Somatic Spinal Reflexes Stretch Reflex - causes contraction of a skeletal muscle (the effector) in response to stretching of the muscle and is ipsilateral Ipsilateral Reflex - sensory nerve impulses enter the spinal cord on the same side from which motor nerve impulses leave it; monosynaptic Reciprocal Innervation - components of a neural circuit simultaneously cause contraction of one muscle and relaxation of its antagonists Tendon Reflex - a feedback mechanism to control muscle tension by causing muscle relaxation before muscle force becomes so great that tendons might be torn and is ipsilateral Flexor Reflex - withdrawal reflex; the incoming and outgoing impulses propagate into and out of the same side of the spinal cord Intersegmental reflex arc - nerve impulses from one sensory neuron ascend and descend in the spinal cord and activate interneurons in several segments of the spinal cord Crossed Extensor Reflex - start to lose your balance as your body weight shift s to the other foot Contralateral reflex arc - sensory impulses enter one side of the spinal cord and motor impulses exit on the opposite side  BRAIN ORGANIZATION, PROTECTION, AND BLOOD SUPPLY Primary Brain Vesicles Prosencephalon Mesencephalon Rhombencephalon Secondary Brain Vesicles Diancephalon - forms the thalamus, hypothalamus, epithalamus, and third ventricle Mesencephalon - midbrain, gives rise to the midbrain and aqueduct of the midbrain (cerebral aqueduct) Metencephalon - becomes the pons, cerebellum, and upper part of the fourth ventricle Myelencephalon - forms the medulla oblongata and lower part of the fourth ventricle Major Parts of the Brain Brainstem - continuous with the spinal cord and consists of the medulla oblongata, pons, and midbrain Cerebellum - posterior to the brainstem Diencephalon - superior to the brainstem which consists of the thalamus, hypothalamus, and epithalamus Cerebrum - the largest part of the brain; supported on the diencephalon and brainstem  Protective Coverings of the Brain Cranial meninges - continuous with the spinal meninges, have the same basic structure, and bear the same names 1. Dura mater Falx cerebri - separates the two hemispheres (sides) of the cerebrum Falx cerebelli - separates the two hemispheres of the cerebellum Tentorium cerebelli - separates the cerebrum from the cerebellum 2. Arachnoid mater 3. Pia mater Blood-Brain Barrier (BBB) - Tight junctions that seal together the endothelial cells of brain blood capillaries and a thick basement membrane that surrounds capillaries - Allows certain substances in blood to enter brain tissue and prevents passage to others - Lipid-soluble substances, steroid hormones, alcohol, barbiturates, nicotine, caffeine, and water molecules easily cross the BBB CEREBROSPINAL FLUID - Clear, colorless liquid composed primarily of water that protects the brain and spinal cord from chemical and physical injuries - also carries small amounts of oxygen, glucose, and other needed chemicals from the blood to neurons and neuroglia - Total volume: 80-150 mL in adults - Functions of CSF: 1. Mechanical protection - shock-absorbing medium that protects the delicate tissues of the brain and spinal cord from jolts that would otherwise cause them to hit the bony walls of the cranial cavity and vertebral canal 2. Chemical protection - provides an optimal chemical environment for accurate neuronal signaling 3. Circulation - medium for minor exchange of nutrients and waste products between the blood and adjacent nervous tissue  Formation of CSF in the Ventricles Majority of CSF production is from the choroid plexus, a network of blood capillaries in the walls of the ventricles BRAINSTEM AND RETICULAR FORMATION I. Medulla Oblongata - Begins at the foramen magnum and extends to the inferior border of the pons, a distance of about 3 cm - Its white matter contains all sensory (ascending) tracts and motor (descending) tracts that extend between the spinal cord and other parts of the brain - Pyramids - formed by the large corticospinal tracts that pass from the cerebrum to the spinal cord - Decussation of pyramids - crossing of axons - Medulla oblongata nuclei: Cardiovascular (CV) Center - regulates the rate and force of the heartbeat and the diameter of blood vessels Medullary respiratory center - adjusts the basic rhythm of breathing Vomiting center - causes vomiting, the forcible expulsion of the contents of the upper gastrointestinal (GI) tract through the mouth Deglutition center - the medulla promotes deglutition (swallowing) of a mass of food that has moved from the oral cavity of the mouth into the pharynx (throat) Centers for sneezing, coughing, hiccupping Sneezing - spasmodic contraction of breathing muscles that forcefully expel air through the nose and mouth Coughing - involves a long-drawn and deep inhalation and then a strong exhalation that suddenly sends a blast of air through the upper respiratory passages Hiccuping - caused by spasmodic contractions of the diaphragm (a muscle of breathing) that ultimately result in the production of a sharp sound on inhalation Inferior olivary nucleus - receives input from the cerebral cortex, red nucleus of the midbrain, and spinal cor Gustatory nucleus - receives gustatory input from the taste buds of the tongue Cochlear nucleus - receive auditory input from the cochlea of the inner ear Vestibular nucleus - receive sensory information associated with equilibrium from proprioceptors (receptors that provide information regarding body position and movements) in the vestibular apparatus of the inner ear II. Pons - Directly superior to the medulla and anterior to the cerebellum  - Pontine respiratory group – control breathing III. Midbrain - mesencephalon - Extends from the pons to the diencephalon - cerebral peduncles - paired bundles of axons in the anterior part - tectum - four rounded elevations in the posterior part Superior colliculi – visual center Inferior colliculi – auditory center - Substantia nigra - large and darkly pigmented - Red nucleus - look reddish due to their rich blood supply and an iron-containing pigment in their neuronal cell bodies Reticular Formation Reticular Formation - consists of small areas of gray matter and white matter Reticular activating system (RAS) - consists of sensory axons that project to the cerebral cortex, both directly and through the thalamus - Most important function: Consciousness Helps maintain attention Inactivation produces sleep Active during arousal Prevents sensory overload THE CEREBELLUM Cerebellum - occupies the inferior and posterior aspects of the cranial cavity Vermis - central constricted area Cerebellar hemispheres - lateral lobes Lobes: Anterior lobe - govern subconscious aspects of skeletal muscle movements Posterior lobe - govern subconscious aspects of skeletal muscle movements Flocculonodular lobe - contributes to equilibrium and balance It connects to the brainstem by three paris of cerebellar peduncles: Superior cerebellar peduncle - contain axons that extend from the cerebellum to the red nuclei of the midbrain and to several nuclei of the thalamus Middle cerebellar peduncle - are the largest peduncles; their axons carry impulses for voluntary movements from the pontine nuclei (which receive input from motor areas of the cerebral cortex) into the cerebellum Inferior cerebellar peduncle - Primary Functions: Balance/equilibrium Coordination Muscle tone DIENCEPHALON: THALAMUS - makes up 80% of the diencephalon, consists of paired oval masses of gray matter organized into nuclei with interspersed tracts of white matter - Interthalamic adhesion - joins the right and left halves of the thalamus - Seven major groups of nuclei: 1. Anterior Nucleus - emotions andmemory 2. Medial Nuclei - emotions, learning, memory, and cognition 3. Lateral Group - emotions and help integrate sensory information Lateral dorsal nucleus - expression of emotions Lateral posterior nucleus - help integrate sensory information Pulvinar nucleus - help integrate sensory information 4. Ventral Group Ventral anterior nucleus - movement control Ventral lateral nucleus - movement control Ventral posterior nucleus - somatic sensations Lateral geniculate nucleus - sight from the retina to the primary visual area of the cerebral cortex Medial geniculate nucleus - hearing from the ear to the primary auditory area of the cerebral cortex 5. Intralaminar Nuclei - arousal and integration of sensory and motor information 6. Midline Nucleus - memory and olfaction 7. Reticular Nucleus - monitors, filters, and integrates activities of other thalamic nuclei - superior to the midbrain and contains nuclei that serve as relay stations for most sensory input to the cerebral cortex - contributes to motor functions by transmitting information from the cerebellum and basal nuclei to the primary motor area of the cerebral cortex - plays a role in the maintenance of consciousness DIENCEPHALON: HYPOTHALAMUS - small part of the diencephalon located inferior to the thalamus - Major groups of nuclei: 1. Mammillary region - relay stations for reflexes related to the sense of smell 2. Tuberal region - the widest part of the hypothalamus 3. Supraoptic region - lies superior to the optic chiasm 4. Preoptic region - anterior to the supraoptic region, participates in regulating certain autonomic activities - Major functions: Control of the ANS Regulation of eating and drinking Production of hormones Control of body temperature Regulation of emotional and behavioral Regulation of circadian rhythms patterns DIENCEPHALON: EPITHALAMUS - a small region superior and posterior to the thalamus - consists of the pineal gland and habenular nuclei - Pineal gland - secretes the hormone melatonin - Habenular nuclei - emotional response to olfaction THE CEREBRUM Cerebrum - “Seat of intelligence” - Provides us with the ability to read, write, speak - Tomake calculations and compose music - To remember the past, plan the future, and imagine things that have never existed before - Consists of the: outer cerebral cortex Internal region of white matter Cerebral Cortex - a region of gray matter that forms the outer rim of the cerebrum - Gyri - folds - Fissures - deepest grooves between folds - Longitudinal fissure - separates the cerebrum into right and left halves called cerebral hemispheres - Sulci - shallow grooves - Corpus callosum - a broad band of white matter that internally connects the two cerebral hemispheres Lobes of the Cerebrum Frontal lobe Parietal lobe Temporal lobe Occipital lobe Insula/Insular lobe Cerebral White Matter 1. Association tracts - contain axons that conduct nerve impulses between gyri in the same hemisphere 2. Commissural tracts - contain axons that conduct nerve impulses from gyri in one cerebral hemisphere to corresponding gyri in the other cerebral hemisphere. 3. Projection tracts - contain axons that conduct nerve impulses from the cerebrum to lower parts of the CNS (thalamus, brainstem, or spinal cord) or from lower parts of the CNS to the cerebrum Basal Ganglia/Nuclei - help initiate and terminate movements, suppress unwanted movements, and regulate muscle tone - Main nuclei: 1. Globus pallidus 2. Putamen 3. Caudate nucleus - Accessory structures: 1. Substantia nigra 2. Subthalamic nucleus Limbic System - ring of structures on the inner border of the cerebrum and floor of the diencephalon - called the “emotional brain” because it plays a primary role in a range of emotions, including pain, pleasure, docility, affection, and anger - Main components: Limbic lobe - a rim of cerebral cortex on the medial surface of each hemisphere Dentate gyrus - between the hippocampus and parahippocampal gyrus Amygdala - several groups of neurons located close to the tail of the caudate nucleus Septal nuclei - within the septal area formed by the regions under the corpus callosum and the paraterminal gyrus Mamillary bodies - two round masses close to the midline near the cerebral peduncles Olfactory bulbs - are flattened bodies of the olfactory pathway that rest on the cribriform plate Fornix, stria terminalis, stria medullaris, medial forebrain bundle, and mammillothalamic tract - linked by bundles of interconnecting myelinated axons - Functions: Plays a primary role in a range of emotions, including pain, pleasure, docility, affection, and anger Functions in the sexual drive Also involved in olfaction and memory  FUNCTIONAL ORGANIZATION OF THE CEREBRAL CORTEX Sensory areas - receive sensory information and are involved in perception, and conscious awareness of sensation Motor areas - control the execution of voluntary movements Association areas - deal with more complex integrative functions such as memory, emotions, reasoning, will, judgment, personality traits, and intelligence CRANIAL NERVES CRANIAL NERVE COMPONENTS PRINCIPAL FUNCTIONS I. Olfactory Special sensory Olfaction (smell). II. Optic Special sensory Vision (sight). III. Oculomotor Motor Somatic Movement of eyeballs and upper eyelid. Motor (autonomic) Adjusts lens for near vision (accommodation). Constriction of pupil. IV. Trochlear Motor Somatic Movement of eyeballs. V. Trigeminal Motor Somatic Touch, pain, and thermal sensations from scalp, face, and oral cavity (including teeth and anterior two-thirds of tongue). Motor (branchial) Chewing and controls middle ear muscle. VI. Abducens Motor Somatic Movement of eyeballs. VII. Facial Mixed Sensory Taste from anterior two-thirds of tongue. Touch, pain, and thermal sensations from skin in external ear canal. Motor (branchial) Control of muscles of facial expression and middle ear muscle. Motor (autonomic) Secretion of tears and saliva VIII. Vestibulocochlear Special sensory Hearing and equilibrium. IX. Glossopharyngeal Mixed Sensory Taste from posterior one-third of tongue. Proprioception in some swallowing muscles. Monitors blood pressure and oxygen and carbon dioxide levels in blood. Touch, pain, and thermal sensations from skin of external ear and upper pharynx. Motor (branchial) Assists in swallowing. Motor (autonomic) Secretion of saliva. X. Vagus Mixed Sensory Taste from epiglottis. Proprioception from throat and voice box muscles. Monitors blood pressure and oxygen and carbon dioxide levels in blood. Touch, pain, and thermal sensations from skin of external ear. Sensations from thoracic and abdominal organs. Motor (branchial) Swallowing, vocalization, and coughing. Motor (autonomic) Motility and secretion of gastrointestinal organs. Constriction of respiratory passageways. Decreases heart rate. XI. Accessory Motor Branchial Movement of head and pectoral girdle XII. Hypoglossal Motor Somatic Speech, manipulation of food, and swallowing  AUTONOMIC NERVOUS SYSTEM - Part of the nervous system that regulates cardiac muscle, smooth muscle, and glands - Consists of autonomic motor neurons - Operates without conscious control - Consists of: Sympathetic Nervous System Parasympathetic Nervous System Enteric Nervous System