Neurobiology: Intro to Neuroscience and the Nervous System PDF

(001) INTRO TO NEUROSCIENCE AND THE NERVOUS SYSTEM DR. VIADO | 09/16/2020 OUTLINE o Sensory Ganglia I. NEUROSCIENCE...

(001) INTRO TO NEUROSCIENCE AND THE NERVOUS SYSTEM DR. VIADO | 09/16/2020 OUTLINE o Sensory Ganglia I. NEUROSCIENCE − Are fusiform swellings on the posterior root of A. Definition each spinal nerve just proximal to the root's II. THE NERVOUS SYSTEM junction with a corresponding anterior root. A. Major Division − They are referred to as posterior root B. Organization ganglia. Similar ganglia found along the C. Order of Neuron course of cranial nerves V, VII, VIII, IX, and X III. DEVELOPMENT are the semory ganglia of these nerves. IV. MAJOR CLASSIFICATIONS OF THE CNS o Autonomic Ganglia − Which are often irregular in shape, are situated along the course of efferent nerve I. NEUROSCIENCE fibers of the ANS. Neuroscience or Neurobiology − They are found in the paravertebral − Is the scientific study of the nervous system. sympathetic chains around the roots of the − Combines physiology, anatomy, molecular biology, great visceral arteries in the abdomen and developmental biology, cytology, mathematical close to, or embedded within, the walls of modelling, and psychology to understand the various viscera. fundamental and emergent properties of neurons and − Contains: neural circuits. o Sensory neurons o Motor neurons II. THE NERVOUS SYSTEM − No bony protection. A. MAIN DIVISON CENTRAL NERVOUS SYSTEM (CNS) − Made of the Brain and the Spinal cord. − Well protected by the skull and spine. − Contains Relay Neurons or Interneurons. − Composed of large numbers of neurons, which are excitable nerve cells and their processes known as axons or nerve fibers. o Neurons are supported by specialized tissue called ganglia − CNS is organized into gray and white matter o Gray matter which is gray in color, consists of nerve cells embedded in neuroglia o White matter consists of nerve fibers embedded in neuroglia and is white in color because of the presence of lipid material in nerve fiber myelin sheaths. o Although the nerves are surrounded by fibrous sheaths as they run to different parts of the body, they are relatively unprotected and are commonly damaged by trauma. PERIPHERAL NERVOUS SYSTEM (PNS) − Nerves with their Ganglia outside of the CNS. − Composed of: o 12 pairs of Cranial Nerves (innervation of the Head/Face) o 31 pairs of Spinal Nerves (innervation of the rest of the Body) o Peripheral Nerves (innervation of individual muscle, muscle group or glands. e.g. Tibial nerve, Peroneal nerve, Sciatic nerve, Figure 1. Major Divisions of the Central and Peripheral Nervous etc. Systems − Ganglia: can be divided into sensory ganglia of spinal nerves (posterior root ganglia) and cranial nerves and autonomic ganglia. PREPARED AND EDITED BY: LUMAYAG, J., MANLONGAT, A., MOJICA, S., PRUDENCIO, J., PUZON, M., QUIAMBAO, C., QUILALA, E.  (001) INTRO TO NEUROSCIENCE AND THE NERVOUS SYSTEM DR. VIADO | 09/16/2020 − The spinal nerves are associated with regions of the B. ORGANIZATION OF THE NERVOUS SYSTEM spinal cord: 1. Sensory input - monitoring stimuli occurring inside or − 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 outside the body (Receptors) goes to the CNS coccygeal. 2. Integration - Processing of the information in the Brain − Note that there are 8 cervical nerves yet only 7 cervical (Store it in memory or to correlate it to affect and action) vertebrae and that there Is 1 coccygeal nerve but 4 3. Motor output - information projected from the CNS coccygeal vertebrae. toward and effector organ − Each spinal nerve is connected to the spinal cord by two roots: the anterior root and the posterior root. o Anterior roots (efferent fibers) − The anterior root consists of bundles of nerve fibers carrying nerve impulses away from the CNS- efferent fibers. − Their cells of origin lie in the anterior gray horn of the spinal cord. o Posterior roots (afferent fibers) − The posterior root consists of bundles of afferent Figure 1. The relationship of afferent sensory stimuli to fibers that carry nervous impulses to the CNS. memory bank, correlation and coordinating centers and − Because these fibers convey information about common efferent pathway sensations of touch, pain, temperature, and Sensory (Sensation) vibration, they are called sensory fibers. − Afferent – Somatic and Visceral Nerve Fibers − The cell bodies of these nerve fibers are situated ln o Conducting impulses from receptors towards the CNS. a swelling on the posterior root called the posterior o root ganglion. Motor (Movement) − Efferent - Motor Nerve fibers o Conducts impulses away from the CNS towards the effector Muscles (Skeletal/Smooth/Cardiac) and Glands. − Voluntary (Conscious Movement) o Skeletal Muscles − Involuntary (Below the Level of Consciousness) o Visceral or Autonomic – cardiac, smooth muscles, glands (e.g. heart rate, salivation, digestion, breathing, sexual arousal, tears etc.) o Subdivided Into: 1. Sympathetic Nervous System − Controls the fight or flight mechanism (e.g heart rate will increase, dilation of pupils etc.) 2. Parasympathetic Nervous System − Controls the rest and digest mechanism (e.g. heart rate will decrease, constriction of pupils, bladder will release, etc.) C. ORDER OF NEURONS CNS − Upper Motor Neuron PNS − Lower Motor Neuron Cranial Nerves (12 Pairs) − Either purely motor or purely sensory or combined sensorimotor Figure 2. Posterior view of the spinal cord showing the origins of the roots of the spinal nerves and their relationship to the different − 12 pairs of cranial nerves leave the brain and pass vertebrae through foramina in the skull. Spinal Nerves (31 pairs) / Peripheral nerves − Both motor and sensory will pass thru the same nerve − The 31 pairs of spinal nerves leave the spinal cord and pass through intervertebral foramina in the vertebral column. PREPARED AND EDITED BY: LUMAYAG, J., MANLONGAT, A., MOJICA, S., PRUDENCIO, J., PUZON, M., QUIAMBAO, C., QUILALA, E.  (001) INTRO TO NEUROSCIENCE AND THE NERVOUS SYSTEM DR. VIADO | 09/16/2020 III. DEVELOPMENT OF THE NERVOUS SYSTEM − Spinal cord also has a canal. Before the formation of the nervous system in the embryo, − Two major bends, or flexures: Midbrain and Cervical. three main cell layers differentiate. B. THE EMBRYONIC DEVELOPMENT OF THE BRAIN − Entoderm: Gives rise to the gastrointestinal tract. The − The development of the brain is a rostrocaudal which lungs, and the liver. means from up to bottom development of the neural tube. − Mesoderm: Gives rise to the muscle, connectlve tissues, The region expands and constricts to form the three and the vascular system primary brain vesicles (forebrain, midbrain, and − Ectoderm: The third and outermost layer, formed of hindbrain) and then further development forms the 2 nd columnar epithelium, gives rise to the entire nervous brain vesicles to adult brain structures and then the system formation of adult neural canals. − Neural plate: During the third week of development the ectoderm on the dorsal surface of the embryo between the primitive knot and the buccopharyngeal membrane thickens to form the neural plate. o The plate, which is pear shaped and wider cranially, develops a longitudinal neural groove. The groove now deepens so that it is bounded on either side by neural folds. o With further development, the neural folds fuse, converting the neural groove into a neural tube. Figure 4. Brain Development IV. MAJOR CLASSIFICATIONS OF THE CNS A. BRAIN − Lies in the cranial cavity and is continuous with the spinal cord through the foramen magnum − It is surrounded by the dura mater, the arachnoid mater, and the pia mater. − These three meninges are continuous with the corresponding meninges of the spinal cord. − The CSF (cerebrospinal fluid) surrounds the brain in the subarachnoid space. − The brain is conventionally divided into three major divisions: the hindbraln, the midbrain, and the forebrain − CEREBRAL HEMISPHERES Figure 3. Formation of the neural plate, neural groove, and neural o Right and Left hemispheres. tube. o Responsible for higher functions (e.g. thinking, memory, consciousness, language, emotion, A. THE BRAIN: EMBRYONIC DEVELOPMENT sensory perception. − Brain develops from the neural tube, an embryonic o Consist of outer cortex which is made of 6 layers of precursor of the central nervous system. gray matter and inner layer which is made up of − Brain subdivides into: white matter 1. Forebrain – Cerebrum, diencephalon (Thalamus, Neocortex- Cerebral cortex has 6 layers (responsible for Hypothalamus, Epithalamus or Pineal gland) higher function) 2. Midbrain Allocortex- Less than 6 layers subdivided into archicortex 3. Hindbrain – Cerebellum, Pons and Medulla. and paleocortex **These further divide to fluid filled regions: Gyrus/Gyri- ridges of the Cerebrum a. Ventricle – Communicating network of cavity field Sulcus/sulci- grooves of the Cerebrum with cerebrospinal fluid (CSF) b. Aqueduct or canal – Allows CSF to flow between ventricle. PREPARED AND EDITED BY: LUMAYAG, J., MANLONGAT, A., MOJICA, S., PRUDENCIO, J., PUZON, M., QUIAMBAO, C., QUILALA, E.  (001) INTRO TO NEUROSCIENCE AND THE NERVOUS SYSTEM DR. VIADO | 09/16/2020 o The Central Sulcus (of Rolando) & Lateral Sulcus − It consists of a dorsal thalamus and a ventral separates the lobes of the brain hypothalamus. 1. Thalamus o Is a large, egg-shaped mass of gray matter that lies on either side of the third ventricle. o The anterior end of the thalamus forms the posterior boundary of the interventricular foramen, the opening between the third and lateral ventricles. o 2 thalami one for each which are joined by the interthalamic adhesion. o Acts as a “switch board” or “gateway” to the cerebral hemisphere (relays connections to the cerebral cortex) Figure 5. The protective covering of the brain o Have cortical loops and reciprocal connection o Function in sleep, wakefulness, coordinating information from the various sensory system, and LOBES OF THE BRAIN has links to the basal ganglia 1. Frontal lobe 2. Epithalamus/Pineal Gland − Located anterior to Central sulcus which is responsible for 3. Hypothalamus thinking/cognition/Movement (Motor) o Connected to the Pituitary Glands. 2. Parietal lobe o Chief master gland − Located posterior to Central sulcus responsible for o Forms the lower part of the lateral wall and floor of the sensation. third ventricle. − Damage to median side of the parietal lobe will affect the sensation the lower extremities. − Damage to lateral side of the parietal lobe will affect the C. BRAIN STEM sensation of the upper extremities and the face. 1. Midbrain 3. Temporal lobe o In front cerebral peduncles 1. Located inferior to the Lateral sulcus which responsible for o Composed of: hearing, emotion a. Corpora Quadrigemina (Latin for Quadruplet 4. Occipital lobe bodies) 2. Located back of the parietal lobe which is responsible for b. 2 Superior Colliculi and 2 Inferior Colliculi (Colliculi vision – Latin for hills) o Sits on the tectum which forms the roof of the midbrain INSULA: a small region of the cerebral cortex located deep o contains Nuclei which are collection of cells bodies within the lateral sulcus, which is a large fissure that which are contain in the CNS separates the frontal and parietal lobes from the temporal *Ganglia collection of cell bodies in the PNS lobe. o The midbrain is the narrow part of the brain that connects the forebrain in to the hind brain. o The narrow cavity of the midbrain is the cerebral aqueduct, which connects the third and fourth ventricles. 2. Pons 3. Medulla o Most distal or inferior o Starts at the end of the pons o Ends at the Foramen Magnum D. CEREBELLUM (LITTLE BRAIN) − Controls balance and coordination − The cerebellum lies within the posterior cranial fossa of the Figure 6. Adult structure of the Human Brain skull posterior to the pons and the medulla oblongata. − The surface layer of each cerebellar hemisphere is called the cortex and is composed of gray matter. B. DIENCEPHALON − The medulla oblongata, the pons, and the cerebellum − The diencephalon is almost completely hidden from the surround a cavity filled with CSF, called the fourth ventricle. surface of the brain. PREPARED AND EDITED BY: LUMAYAG, J., MANLONGAT, A., MOJICA, S., PRUDENCIO, J., PUZON, M., QUIAMBAO, C., QUILALA, E.  (001) INTRO TO NEUROSCIENCE AND THE NERVOUS SYSTEM DR. VIADO | 09/16/2020 − This is connected superiorly to the third ventricle by the Further protection is provided by the CSF which surrounds cerebral aqueduct. Inferiorly it is continuous with the central the spinal cord in the subarachnoid space. canal of the spinal cord It is roughly cylindrical and begins superiorly at the foramen magnum in the skull, where it is continuous with the medulla oblongata of the brain. It terminates inferiorly in the lumbar region. Along the entire length of the spinal cord, 31 pairs of spinal nerves are attached by the anterior or motor roots and the posterior or sensory root. Each root is attached to the cord by a series of rootlets, which extend the whole length of the corresponding segment of the cord Figure 7. Parts of the brainstem and cerebellum E. SPINAL CORD − Is situated within the vertebral canal of the vertebral column and is surrounded by three meninges. o dura matter o arachnoid mater o pia mater Figure 9. Brain, spinal cord, spinal nerve roots, and spinal nerves as seen on their posterior aspect. − Spinal Cord Structure Figure 8. The protective covering of the spinal cord, the o The spinal cord is composed of an inner core of gray meninges, is formed by dura, arachnoid, and pia mater. matter, which is surrounded by an outer covering of white matter. o The gray matter is seen on cross section as an H- − Meninges shaped pillar with anterior and posterior gray columns o Both the brain and spinal cord are covered with a or horns, united by a thin gray commissure containing system of membranes (meninges) and are the small central canal. suspended in cerebrospinal fluid (CSF) o Meninges are further protected by the bones of skull and the vertebral column. o These are the protective covering of the spinal cord and it is formed by dura, arachnoid and pia mater. o Subarachnoid space: the space between the arachnoid and pial membrane and contains cerebrospinal fluid (CSF). PREPARED AND EDITED BY: LUMAYAG, J., MANLONGAT, A., MOJICA, S., PRUDENCIO, J., PUZON, M., QUIAMBAO, C., QUILALA, E.  (001) INTRO TO NEUROSCIENCE AND THE NERVOUS SYSTEM DR. VIADO | 09/16/2020 Amygdala or amygdaloid nucleus is so named because it resembles an almond. It is situated partly anterior and partly superior to the tip of the inferior horn of the lateral ventricle It is fused with the tip of the tail of the caudate nucleus. Part of the limbic system. Limbic system -is not anatomically distinct but a collection of function related nuclei and cortical areas which are involved in emotion, behavior, memory, motivation. Parts of the Limbic System hippocampus - responsible for the formation of memory; sits medial aspect of the temporal lobe fornix mamillary bodies Figure 10. Spinal cord showing the anterior and posterior roots of a amygdala spinal nerve and the meninges. It also shows the H-shaped gray matter of the spinal cord OTHER STRUCTURES IN THE BRAIN Basal ganglia - is a collection of cell bodies which are contained in white matter in the CNS Caudate nucleus -Is a large C-shaped mass of gray matter that is closely related to the lateral ventricle and lies lateral to the thalamus. Divided into: -head - is large and rounded and forms the lateral wall of the anterior horn of the lateral ventricle. Sometimes referred to as the neostriatum or striatum with the putamen -body - is long and narrow and is continuous with the head in the region of the interventricular foramen. The body of the Figure 11. Brain structures comprising the (left) caudate nucleus forms part of the floor of the body of the basal ganglia and (right) limbic system lateral ventricle. -tail - is long and slender and is continuous with the body in the region of the posterior end of the thalamus. It follows the contour of the lateral ventricle and continues forward in the roof of the inferior horn of the lateral ventricle Lentiform nucleus - is formed by the Globus pallidus (inner lighter portion) together with the putamen (larger darker lateral portion). These structures are divided by a vertical plate of white matter - Globus pallidus is divided into: o external globus pallidus o internal globus pallidus Other components of the Basal ganglia are the Subthalamic nucleus & Substantia nigra PREPARED AND EDITED BY: LUMAYAG, J., MANLONGAT, A., MOJICA, S., PRUDENCIO, J., PUZON, M., QUIAMBAO, C., QUILALA, E.