Nervous System PDF

ORGANIZATION OF THE NERVOUS SYSTEM Nehemiah B. Mula,MD FUNCTIONS OF THE NERVOUS SYSTEM Receiving sensory input Integrating information Controlling muscles and glands Maintaining homeostasis Establishing and maintaining mental activity DIVISION OF THE NERVOUS SYSTEM ...

ORGANIZATION OF THE NERVOUS SYSTEM Nehemiah B. Mula,MD FUNCTIONS OF THE NERVOUS SYSTEM Receiving sensory input Integrating information Controlling muscles and glands Maintaining homeostasis Establishing and maintaining mental activity DIVISION OF THE NERVOUS SYSTEM  CELLS OF THE NERVOUS SYSTEM NEURONS Electrically excitable cells of the nervous system Divided into 3 parts ○ Neuron Cell body ○ Dendrites ○ Axon  NEURON STRUCTURE NEURON CELL BODY (SOMA) Performs typical functions of any cell Has a centrally located large nucleus with a prominent nucleoli Have an extensive endoplasmic reticulum called Nissl bodies DENDRITES Extension of cell body ○ Short, highly branched cytoplasmic extension Receive information from other neurons Have dendritic spines where axons from other neurons form connections with  NEURON STRUCTURE AXONS Single axon arises from a cone-shaped area of the neuron cell body called axon hillock ○ Narrows and transitions into the initial segment ○ Axon hillock + initial segment = Trigger zone Axons have constant diameter but vary in length Cytoplasm of axon is called axoplasm and the plasma membrane is called axolemma  NEURON STRUCTURE AXONS Axon projects away from cell body until it reaches the plasma membrane of the effector Point of contact between the axon and its effector is called synapse Region of the axon ending at the synapse is called presynaptic terminal ○ Have synaptic vesicles which stores the neurotransmitters Movement of signal AWAY from the cell body is called ANTEROGRADE movement Movement of signal TOWARDS the cell body is RETROGRADE  TYPES OF NEURONS CLASSIFICATION OF NEURONS BASED ON FUNCTION SENSORY NEURONS ○ Also called Afferent neurons ○ Detect stimuli from the environment ○ Conduct action potentials toward the CNS MOTOR NEURONS ○ Also called Efferent neurons ○ Conduct action potentials from CNS towards the muscles or glands (effectors) INTERNEURONS ○ Conduct action potentials within the CNS from one neuron to another  TYPES OF NEURONS CLASSIFICATION OF NEURONS BASED ON NUMBER OF DENDRITES MULTIPOLAR NEURONS ○ Have many dendrites and a single axon ○ Motor neurons of the PNS and most neurons of CNS are multipolar neurons BIPOLAR NEURONS ○ Have 2 processes: one dendrite and one axon ○ Conduct action potentials within the CNS from one neuron to another ○ Found in some sensory organs such as the retina of the eye and nasal cavity  TYPES OF NEURONS CLASSIFICATION OF NEURONS BASED ON NUMBER OF DENDRITES PSEUDO-UNIPOLAR NEURONS ○ Start out as bipolar neurons but the 2 processes extend from the cell body fuse into a single process ○ The singles process divides into 2 branches Peripheral process has dendrites Central process extends into the CNS ○ Most sensory neurons are pseudounipolar ANAXONIC NEURONS ○ Do not have an axon and only have dendrites ○ Found within the brain  CELLS OF THE NERVOUS SYSTEM GLIAL CELLS Support cells for neurons Four types of CNS Glial cells ○ Astrocytes ○ Ependymal cells ○ Microglia ○ Oligodendrocytes  GLIAL CELLS OF THE CENTRAL NERVOUS SYSTEM ASTROCYTES Star-shaped glial cells with cytoplasmic processes extending from cell bodies Has extensions that widen and spread out to form foot processes Form the blood-brain barrier ○ Determines which substances can pass from blood into the nervous tissue ○ Allows exchange of nutrients and waste products between neurons and blood  GLIAL CELLS OF THE CENTRAL NERVOUS SYSTEM EPENDYMAL CELLS Line the ventricles or cavities with the brain and the central canal of the spinal cord Form structure of choroid plexus which secretes Cerebrospinal fluid MICROGLIA Immune cells of the CNS The phagocytize (engulf) foreign bodies and waste materials  GLIAL CELLS OF THE CENTRAL NERVOUS SYSTEM OLIGODENDROCYTES ○ Wraps around the axons of neurons within the CNS forming an insulating layer ○ Cytoplasm of Oligodendrocytes wrap around the axons many times forming myelin sheath  GLIAL CELLS OF THE PERIPHERAL NERVOUS SYSTEM SATELLITE CELLS ○ Surround the neurons of PNS ○ Provide support and nutrition ○ Protect neurons from heavy metal poisoning such as mercury and lead SCHWANN CELLS ○ Form myelin sheaths within the PNS  MYELINATED AND UNMYELINATED AXONS MYELINATED AXONS Schwann cells (PNS) or Oligodendrocytes (CNS) repeatedly wrap around a segment of axon to form tightly wrapped membranes Not a continuous covering but has gaps in between ○ Gaps are called Nodes of Ranvier Myelinated neurons allow conduction of signal to proceed via saltatory conduction ○ Allows electrical signals to travel more rapidly UNMYELINATED AXONS Not totally devoid of myelin sheath but the glial cells only wrap around it once DEVELOPMENT OF THE NERVOUS SYSTEM DEVELOPMENT OF THE NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM: SPINAL CORD CENTRAL NERVOUS SYSTEM: SPINAL CORD CENTRAL NERVOUS SYSTEM: SPINAL CORD CENTRAL NERVOUS SYSTEM: SPINAL CORD  CENTRAL NERVOUS SYSTEM: BRAIN DIVISION OF THE BRAIN FOREBRAIN CEREBRUM DIENCEPHALON ○ THALAMUS ○ HYPOTHALAMUS MIDBRAIN HINDBRAIN CEREBELLUM MEDULLA OBLONGATA PONS  CENTRAL NERVOUS SYSTEM: HINDBRAIN MEDULLA OBLONGATA Conical in shape and connects the pons superiorly to the spinal cord inferiorly Serves as conduit for ascending and descending nerve fibers Center for regulating heart rate, breathing, swallowing, and vomiting  CENTRAL NERVOUS SYSTEM: HINDBRAIN PONS Situated on the anterior surface of the cerebellum Situated inferior to the midbrain and superior to the medulla oblongata Has large number of transverse fibers on its anterior aspect connecting the 2 cerebellar hemispheres Pontine sleep center and pontine respiratory center  CENTRAL NERVOUS SYSTEM: HINDBRAIN CEREBELLUM Lies within the posterior cranial fossa Situated posterior to the pons and medulla oblongata Has 2 hemispheres connected by a median portion called the vermis Connections to the: ○ Midbrain by the superior cerebellar peduncle ○ Pons by the middle cerebellar peduncle ○ Medulla by the inferior cerebellar peduncle  CENTRAL NERVOUS SYSTEM: HINDBRAIN CEREBELLUM VERMIS ○ Involved in controlling posture, locomotion, and fine motor coordination → smooth flowing movements LATERAL HEMISPHERES ○ Function with frontal lobe for planning, practicing, and learning complex movements FLOCCULONODULAR LOBE ○ Helps control balance and eye movement  CENTRAL NERVOUS SYSTEM: HINDBRAIN CEREBELLUM The medulla, pons, and cerebellum surround a cavity filled with CSF called the fourth ventricle ○ connected superiorly to the 3rd ventricle by the cerebral aqueduct ○ Continuous with the central canal of spinal cord inferiorly  CENTRAL NERVOUS SYSTEM: HINDBRAIN CEREBELLUM Has 3 main lobes and 3 main fissures 3 lobes ○ Anterior Lobe ○ Posterior Lobe ○ Flocculonodular Lobe 3 fissures ○ Primary Fissure ○ Horizontal Fissure ○ Posterolateral Fissure  CENTRAL NERVOUS SYSTEM: MIDBRAIN MIDBRAIN Superior part of the brainstem Narrow portion that connects the forebrain to the hindbrain Narrow cavity of the midbrain is the cerebral aqueduct Serves as visual reflex center and part of the auditory pathway  CENTRAL NERVOUS SYSTEM: FOREBRAIN FOREBRAIN Comprises the: ○ Diencephalon ○ Cerebrum  CENTRAL NERVOUS SYSTEM: FOREBRAIN DIENCEPHALON Almost completely hidden from the surface of the brain Consist of the dorsal thalamus and ventral hypothalamus  CENTRAL NERVOUS SYSTEM: FOREBRAIN THALAMUS Large, egg-shaped mass of gray matter lying on each side of the 3rd ventricle Anterior end of the thalamus forms the posterior boundary of the interventricular foramen CENTRAL NERVOUS SYSTEM: FOREBRAIN  CENTRAL NERVOUS SYSTEM: FOREBRAIN THALAMUS Serves as the sensory relay center All sensory inputs will go to the thalamus first before going to the cerebrum EXCEPT olfactory or sense of smell which goes directly to the cerebrum  CENTRAL NERVOUS SYSTEM: FOREBRAIN HYPOTHALAMUS Forms the lower part of the lateral wall and floor of the third ventricle Most inferior portion of diencephalon  CENTRAL NERVOUS SYSTEM: FOREBRAIN CEREBRUM Largest part of the brain consisting of 2 hemispheres connected by a mass of white matter called corpus callosum  CENTRAL NERVOUS SYSTEM: FOREBRAIN CEREBRUM The surface of the cerebrum known as the cortex is composed of gray matter Composed of folds (gyri) and fissures (sulci)  CENTRAL NERVOUS SYSTEM: FOREBRAIN CEREBRUM Divided into 4 lobes: ○ FRONTAL ○ PARIETAL ○ TEMPORAL OCCIPITAL  CENTRAL NERVOUS SYSTEM: FOREBRAIN CEREBRUM FRONTAL LOBE ○ Voluntary motor function ○ Motivation, aggression, sense of smell, and mood ○ Prefrontal region is involved in personality and decision making PARIETAL LOBE ○ Major center for most sensory information except for smell, hearing, taste, and vision OCCIPITAL LOBE ○ Receiving and integrating visual input TEMPORAL LOBE ○ Receives and evaluates input for smell and hearing and plays an important role in memory INSULA ○ Often referred as 5th lobe located deep within the lateral fissure ○ Participates in taste information  CENTRAL NERVOUS SYSTEM: FOREBRAIN CEREBRUM Each hemisphere extends from the frontal to the occipital bones in the skull It lies above the tentorium cerebelli The hemispheres are separated by a deep cleft, the longitudinal fissure, into which the falx cerebri projects  CENTRAL NERVOUS SYSTEM: FOREBRAIN CEREBRUM At the center is the basal ganglia, core of white matter with several large masses of gray matter The basal ganglia is composed of 3 nuclei ○ Caudate ○ Putamen ○ Globus Pallidus Basal ganglia/nuclei controls muscle activity, posture and largey inhibits unintentional movement when at rest  CENTRAL NERVOUS SYSTEM: FOREBRAIN CEREBRUM Within each cerebral hemisphere is a cavity called the lateral ventricle which communicates with the third ventricle through the interventricular foramen Gray matter in the brain is situated outside while the white matter comprises the inner core  CENTRAL NERVOUS SYSTEM: VENTRICULAR SYSTEM COME, LET’s MEET TITA SYLVIA FOR LUNCH MAMAYA SA ARISTOCRAT  CENTRAL NERVOUS SYSTEM: LIMBIC SYSTEM LIMBIC SYSTEM Parts of the cerebrum and diencephalon are grouped together as the Limbic system Plays a role in motivation, emotion, learning, memory, and influences endocrine and autonomic functions PERIPHERAL NERVOUS SYSTEM  PERIPHERAL NERVOUS SYSTEM The PNS comprises the cranial and spinal nerves ○ 12 pairs of cranial nerves ○ 31 pairs of spinal nerves  PERIPHERAL NERVOUS SYSTEM CRANIAL NERVES 12 pairs of cranial nerves Each cranial nerves will exit the skull through a different foramina  PERIPHERAL NERVOUS SYSTEM SPINAL NERVES 31 pairs of spinal nerves ○ Leave the spinal cord and pass through the intervertebral foramina in the vertebral column ○ 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal nerves  PERIPHERAL NERVOUS SYSTEM SPINAL NERVES Each spinal nerve is connected to the spinal cord by 2 roots ○ Anterior root Consists of bundles of nerve fibers carrying nerve impulses away from the CNS (efferent fibers) Fibers that go to the skeletal muscles and cause them to contract (motor fibers) ○ Posterior root Consists of bundles of fibers that carry nervous impulses to the CNS (afferent fibers) Convey information about sensations of touch, pain, temperature, vibration (sensory fibers)  PERIPHERAL NERVOUS SYSTEM GANGLIA Collection of nerve bodies within the PNS Serves as synaptic relay station between neurons Has 2 types ○ Sensory ganglia ○ Autonomic ganglia AUTONOMIC NERVOUS SYSTEM  AUTONOMIC NERVOUS SYSTEM DIVISION OF THE AUTONOMIC NERVOUS SYSTEM SYMPATHETIC ○ “Fight or flight” PARASYMPATHETIC ○ “Rest and digest” Composed of a 2-motor neuron system ○ Preganglionic neuron synapses with the postganglionic neuron ○ Postganglionic neuron synapses with the effector organ receptor  AUTONOMIC NERVOUS SYSTEM SYMPATHETIC NERVOUS SYSTEM Preganglionic Neuron ○ Cell body is in the thoracic and lumbar region (thoracolumbar outflow) Postganglionic Neuron ○ Cell body is in the paravertebral or prevertebral ganglia Sympathetic NS has a SHORT preganglionic nerve fiber and LONG postganglionic nerve fiber  AUTONOMIC NERVOUS SYSTEM PARASYMPATHETIC NERVOUS SYSTEM Preganglionic Neuron ○ Cell body is in the brainstem and sacral segment (craniosacral outflow) Postganglionic Neuron ○ Cell body is in the ganglia at the walls of the effector organs Parasympathetic NS has a LONG preganglionic nerve fiber and SHORT postganglionic nerve fiber THANK YOU!