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Nervous System
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Histology of the Nervous System
Types of cells in the nervous tissue. Neurons Glial cells or neuroglias support cells. CNS: astrocyte (control chemical enviroment), oligodendrocyte (myelination), microglia (phagocyte), ependimal cells (production of CSF) PNS: Shwann cells (myelination) and satellite cells.
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Neuroglia Capillary Neuron (b) Microglial cell (a) Astrocyte
Nerve fibers Myelin sheath Fluid-filled cavity Process of oligodendrocyte (c) Ependymal cells Brain or spinal cord tissue Cell body of neuron (d) Oligodendrocyte Schwann cells (forming myelin sheath) Satellite cells Nerve fiber (e) Sensory neuron with Schwann cells and satellite cells
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Neuron Anatomy Major parts: Cell body (grey matter) or Soma
Central Nervous System (CNS): clusters = nuclei; in Peripheral Nervous system (PNS) = ganglia Neuron processes (axons): CNS: tracts PNS: nerves Neurofibrils: cytoskeleton Nissle bodies: RER that is chomatophilic Dendrites: processes that carry impulses towards the cell body. Axons: processes that carry impulses away from the cell body. Axon Hillock Axon terminals Synaptic cleft Myelin fibers (not all the axons)
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Structures of a motor neuron
Dendrites (receptive regions) Cell body (biosynthetic center and receptive region) Neuron cell body Nucleus (a) Dendritic spine Axon (impulse generating and conducting region) Nucleolus Impulse direction Nissl bodies Node of Ranvier Axon terminals (secretory component) Axon hillock Schwann cell (one inter- node) Neurilemma (sheath of Schwann) Terminal branches (telodendria) (b)
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Structure of a synapse Neurotransmitter Ca2+ Na+ Action Potential
Axon terminal of presynaptic neuron Action Potential Receptor 1 Postsynaptic membrane Mitochondrion Postsynaptic membrane Axon of presynaptic neuron Ion channel open Synaptic vesicles containing neurotransmitter molecules 5 Degraded neurotransmitter Na+ 2 Synaptic cleft 3 4 Ion channel closed Ion channel (closed) Ion channel (open)
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Myelinated fibers Made by: Structures: Oligodendrocytes in CNS
Schwann cells in PNS Structures: Myelin sheath Neurilemma: sheath of Schwann cells. Nodes of Ranvier
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Myelination of axons in the PNS by Schwann cells
cytoplasm Schwann cell plasma membrane Axon Schwann cell nucleus Myelin sheath (a) Schwann cell cytoplasm Axon Neurilemma (b) (d) Neurilemma Myelin sheath (c)
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Activity 1 Identify the parts of a neuron in a slide.
Identify the parts of a neuron in a model
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Neuron Classification
By structure Unipolar neurons: 1 process Sensory neurons, impulse CNS Bipolar neurons: 2 processes Part of receptor system: eye, ear, olfactory Multipolar neurons: several processes. Impulse CNS Activity 2: identify different neurons in the slide.
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Neuron classification by their structure
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Neuron Classification
Classification by function Sensory Afferent Association
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Classification of neurons by function
Interneurons + + – + + – Efferent fibers Afferent fiber Efferent fibers Extensor inhibited Flexor inhibited Flexor stimulated Flexes Arm movements Extensor stimulated Extends Key: + Excitatory synapse – Inhibitory synapse Right arm (site of stimulus) Left arm (site of reciprocal activation)
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Structure of a nerve Axon Blood vessels Perineurium Myelin sheath
Endoneurium Perineurium Epineurium Fascicle Fascicle Blood vessels Endoneurium Nerve fibers (a) (b)
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Neurophysiology How action potentials trigger nervous impulses.
Resting potential Action potential Depolarization of the membrane. Refractory period Repolarization of the membrane Stimuli transmission
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Measuring membrane potential in neurons
Voltmeter Plasma membrane Ground electrode outside cell Microelectrode inside cell Axon Neuron
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The basis of the resting membrane potential
Cell exterior Na+ 15 mM Na+ Cell interior Na+ K+ 150 mM ion Na+ Diffusion us Na+–K+ pump Diff -70 mV Cl– 10 mM Na+ Na+ 150 mM A– 100 mM Na+ K+ Na+ A– 0.2 mM Na+ Plasma membrane K+ 5 mM K+ Cl– 120 mM K+ Cell interior Cell exterior K+ K+
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Changes in membrane potential produced by a depolarizing graded potential
Active area (site of initial depolarization) Membrane potential (mV) – 70 Resting potential Distance (a few mm)
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Refractory periods in an AP
Absolute refractory period Relative refractory period Depolarization (Na+ enters) +30 Repolarization (K+ leaves) Membrane potential (mV) After-hyperpolarization –70 Stimulus 1 2 3 4 5 Time (ms)
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Propagation of an action potential (AP)
Voltage at 2 ms +30 Membrane potential (mV)) Voltage at 0 ms Voltage at 4 ms –70 (a) Time = 0 ms (b) Time = 2 ms (c) Time = 4 ms Resting potential Peak of action potential Hyperpolarization
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Relationship between stimulus strength and action potential frequency
potentials +30 Membrane potential (mV) – 70 Stimulus amplitude Threshold Voltage Time (ms)
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Saltatory conduction in a myelinated axon
Node of Ranvier Cell body Myelin sheath Distal axon
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Central nervous system
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The nervous system’s functions
Sensory input Integration Motor output
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Levels of organization in the nervous system
Key: Brain Central nervous system (CNS) Brain and spinal cord Integrative and control centers = Sensory (afferent) division of PNS = Motor (efferent) Key: = Structure = Function Visceral sensory fiber Peripheral nervous system (PNS) Cranial nerves and spinal nerves Communication lines between the CNS and the rest of the body Central nervous system (CNS) Parasympathetic motor fiber of ANS Sympathetic motor fiber of ANS Visceral organ Spinal cord Skin Somatic sensory fiber Sensory (afferent) division Somatic and visceral sensory nerve fibers Conducts impulses from receptors to the CNS Motor (efferent) division Motor nerve fibers Conducts impulses from the CNS to effectors (muscles and glands) Motor fiber of somatic nervous system Skeletal muscle Sympathetic division Mobilizes body systems during activity Autonomic nervous system (ANS) Visceral motor (involuntary) Conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands Somatic nervous System Somatic motor (voluntary) Conducts impulses from the CNS to skeletal muscles Peripheral nervous system (PNS) Parasympathetic division Conserves energy Promotes housekeeping functions during rest (b) (a)
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Gross Anatomy of the Brain and Cranial Nerves
Human Brain (activity 1,2) Cerebral Hemispheres of the cerebrum Diencephalon Brain Stem Cerebellum Meninges Cerebrospinal Fluid Choroid processes (ependymal cells + capillaries) Cranial Nerves (activity 3) Spinal cord Brain dissection
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Cerebrum: Cerebral Hemispheres
Mainly grey matter (soma of neurons) 5 lobes Frontal: anterior to the Central sulcus Parietal: posterior to the central sulcus, superior to the lateral sulcus, superior to the parietal-occipital sulcus Temporal: inferior to the lateral sulcus, Occipital: inferior to the parietal-occipital sulcus Insula (within the lateral sulcus, covered by the temporal and parietal lobes)
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Arrangement of gray and white matter in the CNS
Central cavity Cortex of gray matter Migratory pattern of neurons Inner gray matter Cerebrum Outer white matter Cerebellum Gray matter Region of cerebellum Central cavity Inner gray matter Outer white matter Gray matter Brain stem Central cavity Outer white matter Inner gray matter Spinal cord
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Lobes and fissures of the cerebral hemispheres
Central sulcus Precentral gyrus Postcentral gyrus Frontal lobe Parietal lobe Parieto-occipital sulcus (on medial surface of hemisphere) Frontal lobe Central sulcus Lateral sulcus Occipital lobe Temporal lobe Transverse cerebral fissure Cerebellum Pons (a) Medulla oblongata Spinal cord Gyri of insula Gyrus Cortex (gray matter) Temporal lobe (pulled down) Sulcus (b) White matter Fissure (a deep sulcus)
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Lobes and fissures of the cerebral hemispheres
Anterior Longitudinal fissure Frontal lobe Cerebral veins and arteries covered by arachnoid Parietal lobe Right Cerebral hemisphere Left cerebral hemisphere Occipital lobe Posterior (c)
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Functional and structural areas of the cerebral cortex
Primary somatosensory cortex: post central gyrus Somatosensory association area: immediate after PSC Primary motor area Broca’s area: speech Prefontral area: intellect, personality
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Functional and structural areas of the cerebral cortex
Central sulcus Primary motor area Primary somatosensory cortex 3 Somatic sensation Premotor cortex 1 2 4 Somatosensory association area 6 5 Frontal eye field 7 8 Gustatory cortex (in insula) Taste Working memory for spatial tasks Wernicke's area (outlined by dashes) Executive area for task management 45 43 44 22 Broca's area (outlined by dashes) 41 42 19 18 Primary visual cortex 22 17 Working memory for object-recall tasks 47 11 Vision Visual association area Solving complex, multitask problems Prefrontal cortex Auditory association area Hearing Primary auditory cortex (a)
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Functional and structural areas of the cerebral cortex
Premotor cortex Cingulate gyrus Primary motor area Corpus callosum 4 6 Central sulcus Primary somatosensory cortex 8 6 4 1-3 Frontal eye field 8 5 Parietal lobe Somatosensory association area Prefrontal cortex 7 Parieto-occipital sulcus 19 Occipital lobe Processes emotions related to personal and social interactions 18 18 Visual association area 34 17 Orbitofrontal cortex 28 Olfactory bulb Calcarine sulcus Primary visual cortex Uncus Olfactory tract Temporal lobe (b) Fornix Primary olfactory cortex Parahippocampal gyrus
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Motor and sensory areas of the cerebral cortex (homuculus)
Shoulder Trunk Knee Trunk Neck Hip Leg Hip Head Elbow Arm Arm Elbow Wrist Forearm Hand Fingers Hand Fingers Thumb Thumb Eye Neck Nose Brow Face Eye Lips Genitals Face Toes Teeth Gums Lips Jaw Jaw Tongue Tongue Pharynx Swallowing Motor cortex (precentral gyrus) Intra- abdominal
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B. Basal ganglia (nuclei)
Islands of grey matter within the white matter. Flank lateral and third ventricle. Function: Subcortical motor nuclei (extrapyramidal system), regulates voluntary motor control. Caudate nucleus (memory, love?), lentiform nucleus, putamen (learning reinforcement), globus pallidus. Corona radiata: projection of fibers.
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Basal nuclei Fibers of corona radiata Caudate nucleus Thalamus Corpus
striatum Lentiform nucleus Tail of caudate nucleus Internal capsule (projection fibers run deep to lentiform nucleus) (a)
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Basal nuclei Anterior Cerebral cortex Cerebral white matter
Corpus callosum Anterior horn of lateral ventricle Caudate nucleus Third ventricle Putamen Lentiform nucleus Globus pallidus Thalamus Inferior horn of lateral ventricle (b) Posterior
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C. Diencephalon Embryologically, part of the forebrain
Major structures: Thalamus Hypothalamus/Pituitary gland Epithalamus Trigunium habenulae Pineal body Posterior commussire Pretectum (pupilary light relfex) Externally Olfactory, optic tracts, optic nerves, optic chiasma, pituitary gland, mammilary bodies (part of the limbic system; emotions, long term memory, etc).
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Midsagittal section of the brain illustrating the diencephalon and brain stem,
Parietal lobe of cerebral hemisphere Septum pellucidum Corpus callosum Interthalamic adhesion (intermediate mass of thalamus) Fornix Choroid plexus Occipital lobe of cerebral hemisphere Frontal lobe of cerebral hemisphere Thalamus (encloses third ventricle) Posterior commissure Interventricular foramen Pineal body/gland (part of epithalamus) Anterior commissure Corpora quadrigemina Midbrain Hypothalamus Cerebral aqueduct Optic chiasma Pituitary gland Arbor vitae Temporal lobe of cerebral hemisphere Fourth ventricle Mammillary body Choroid plexus Pons Cerebellum Medulla oblongata Spinal cord
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D. Brain Stem Major structures: Cerebral peduncles Pons
Medulla oblongata Decussation of pyramids
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Ventral aspect of the human brain, showing the three regions of the brain stem
Frontal lobe Olfactory bulb (synapse point of cranial nerve I) Optic chiasma Optic nerve (II) Optic tract Midbrain Mammillary body Pons Temporal lobe Medulla Cerebellum Spinal cord
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E. Cerebellum Features: Function: Center midline: vermis
Arbor vitae “tree of life” Function: Balance and equilibrium
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Anterior view Posterior view
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2. Meninges Three connective tissue membranes that protect the brain and the medulla from mechanical stress. Inflammation of this tissue membrane is called meningitis. If infected, it produces encephalitis.
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Meninges Skin of scalp Periosteum Bone of skull Periosteal Dura
mater Meningeal Superior sagittal sinus Arachnoid mater Pia mater Subdural space Arachnoid villus Subarachnoid space Blood vessel Falx cerebri (in longitudinal fissure only) (a)
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Meninges Skull Scalp Superior sagittal sinus Dura mater Occipital lobe
Tentorium cerebelli Tranverse sinus Cerebellum Temporal bone Arachnoid mater over medulla oblongata (b)
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Partitioning folds of dura mater in the cranial cavity
Falx cerebri Superior sagittal sinus Straight sinus Tentorium cerebelli Crista galli of the ethmoid bone Cavernous sinus Internal carotid artery Falx cerebelli
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A. Cerebrospinal fluid Fluid, similar in composition to blood plasma, is circulated through the ventricles (cisternas). Function: mechanical stress protection of the brain and medulla, acting as a cushion. Produced in the choroid plexuses. Capillary knots in the surface of the ventricles.
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Formation, location, and circulation of CSF
Superior sagittal sinus Superior cerebral vein Arachnoid villus Choroid plexus Cerebrum covered with pia mater Subarachnoid space Arachnoid mater Septum pellucidum Meningeal dura mater Periosteal dura mater Great cerebral vein Corpus callosum Tentorium cerebelli Interventricular foramen Straight sinus Confluence of sinuses Third ventricle Pituitary gland Cerebellum Cerebral aqueduct Choroid plexus Lateral aperture Cerebral vessels that supply choroid plexus Fourth ventricle Median aperture Central canal of spinal cord Spinal dura mater Inferior end of spinal cord Filum terminale (inferior end of pia mater) (b)
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4. Spinal cord Location: from C1-C2 (continuation of the brain stem) to the conus medullaris (L1-L2). Characteristics: Protected by the meninges (S1-S2 to the filum terminale). Attaches to the vertebras by the denticulate ligaments of the pia mater and the filum termiale (coccygeal canal) Function: association and communication center. Central point of the reflex arc.
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Spinal cord external anatomy
Cervical plexus Cervical nerves C1– C8 Brachial plexus Cervical enlargement Intercostal Thoracic nerves T1– T12 nerves Lumbar enlargement Conus medullaris Lumbar plexus Lumbar nerves L1– L5 Sacral plexus Sacral nerves S1– S5 Filum terminale Cauda equina Coccygeal nerve C0
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Structure of the Spinal Cord
White matter Ventral root Dorsal root Gray matter Dorsal root ganglion Dorsal and ventral rootlets of spinal nerve Dorsal ramus of spinal nerve Ventral ramus of spinal nerve Spinal nerve Rami communicantes Sympathetic trunk (chain) ganglion (a)
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Histology of the Spinal cord
Grey matter: H form Ventral (anterior) horns Ventral root (motor) Dorsal (posterior) horns Dorsal roots (sensory) Dorsal ganglions Lateral horn (thoraxic and lumbar region) White matter
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Organization of the gray matter of the spinal cord
Dorsal root (sensory) Dorsal horn (interneurons) Dorsal root ganglion SS VS Somatic sensory neuron VM Visceral sensory neuron SM Visceral motor neuron Somatic motor neuron Spinal nerve Ventral root (motor) Ventral horn (motor neurons)
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Transversal section of the Spinal Cord
Funiculus: fiber tracts with the same origin, terminus and function
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Transversal sections of the spinal cord
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3. Cranial Nerves Part of the PNS
Mnemonic: On ocassion, our trusty truck acts funny-very good vehicle anyhow.
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Location and function of cranial nerves
Filaments of olfactory nerve (I) Frontal lobe Olfactory bulb Olfactory tract Temporal lobe Optic nerve (II) Optic chiasma Optic tract Infundibulum Oculomotor nerve (III) Facial nerve (VII) Trochlear nerve (IV) Vestibulo- cochlear nerve (VIII) Trigeminal nerve (V) Glosso- pharyngeal nerve (IX) Abducens nerve (VI) Vagus nerve (X) Cerebellum Accessory nerve (XI) Hypoglossal nerve (XII) Medulla (a)
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Sheep brain dissection
Identify the following structures Ventral: Olfactory bulb Optic nerve Mammilary body Cerebral peduncle Cranial nerves Medulla oblongata Dorsal Cererbum Cerebellum
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Sheep brain dissection
Sagital section Cerebral hemisphere Corpus callosum Frontal lobe of the cerebellum Intermedate mass of the cerebellum Cerebral peduncle Optical quiasma Parietal lobe Cerebellum Pineal body Arbor Vitae Corpora quadrigema Fourth ventricle Medulla oblongata Pons
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Sheep brain dissection
Frontal section of the brain Fornix Corpus triatum Amygdaloid nucleus Third ventricle Lateral ventricle Intermediate mass of the thalamus Thalamic nuclei hypothalamus
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Relationship of the brain stem and the diencephalon
Optic nerve Thalamus Optic chiasma Optic tract Floor of hypothalamus Infundibulum (pituitary removed) Oculomotor nerve (III) Mammillary body Crus cerebri of cerebral peduncles (midbrain) Trochlear nerve (IV) Pons Trigeminal nerve (V) Middle cerebellar peduncle Abducens nerve (VI) Facial nerve (VII) Vestibulocochlear nerve (VIII) Hypoglossal nerve (XII) Glossopharyngeal nerve (IX) Pyramid Vagus nerve (X) Decussation of pyramids Accessory nerve (XI) Spinal cord Ventral root of first cervical nerve (a) Ventral view
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Relationship of the brain stem and the diencephalon
Thalamus Optic tract Crus cerebri of cerebral peduncles (midbrain) Superior colliculus Infundibulum Inferior colliculus Pituitary gland Trochlear nerve (IV) Trigeminal nerve (V) Superior cerebellar peduncle Facial nerve (VII) Pons Vestibulocochlear nerve (VIII) Middle cerebellar peduncle Abducens nerve (VI) Glossopharyngeal nerve (IX) Inferior cerebellar peduncle Vagus nerve (X) Olive Fasciculus gracilis Hypoglossal nerve (XII) Fasciculus cuneatus Accessory nerve (XI) (b) Left lateral view
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Relationship of the brain stem and the diencephalon
Third ventricle Thalamus Superior colliculus Pineal gland Corpora quadrigemina of tectum Inferior colliculus Lateral geniculate nucleus Midbrain Medial geniculate nucleus Trochlear (IV) nerve Superior cerebellar peduncle Middle cerebellar peduncle Pons Inferior cerebellar peduncle Anterior wall of fourth ventricle Facial (VII) nerve Vestibulocochlear (VIII) nerve Choroid plexus (fourth venticle) Medulla Glossopharyngeal (IX) nerve Posterior median sulcus Vagus (X) nerve Fasciculus cuneatus Accessory (XI) nerve Fasciculus gracilis Posterior (dorsal) root of first cervical nerve (c) Dorsal view
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