Human Anatomy: Central Nervous System, Part 1 PDF

Human Anatomy The Central Nervous System, Part 1 Course: BL3420 Instructor: Benjamin T. Enslow, M.D. Email: [email protected] Phone: (830) 391-4298 Office: Moody 214 Reading: Chapter 13; Sections 13.1b-e Slides Adapted...

Human Anatomy The Central Nervous System, Part 1 Course: BL3420 Instructor: Benjamin T. Enslow, M.D. Email: [email protected] Phone: (830) 391-4298 Office: Moody 214 Reading: Chapter 13; Sections 13.1b-e Slides Adapted From: PowerPoint® Lecture Presentations prepared by Leslie Hendon University of Alabama, Birmingham Molly Selba University of Florida Copyright © 2020 Pearson Education, Inc. All Rights Reserved Learning Objectives 1. Name the major parts of the brain. 2. Name and describe the locations of the ventricles of the brain. 3. Describe the distribution of gray and white matter in each part of the brain. 4. Identify the three subdivisions of the brain stem and list the major structures in each. 5. Describe the structure and function of the cerebellum. 6. Name the two major divisions of the diencephalon and describe their functions (note: we will not cover the epithalamus in this class) Need-to-Know Terms Brainstem Pons Midbrain Pyramidal motor tracts Pons Pontine nuclei Medulla oblongata Middle cerebellar peduncles Cerebellum Reticular formation nuclei Diencephalon Cerebrum Midbrain Cerebral hemispheres Cerebral aqueduct Tectum Ventricles Cerebral peduncles Central cavity Crus cerebri Cerebrospinal fluid Substantia nigra Lateral ventricles Red nucleus Septum pellucidum Superior colliculi Third ventricle Inferior colliculi Interventricular foramen Periaqueductal gray matter Cerebral aqueduct Fourth ventricle Diencephalon Lateral apertures Thalamus Median aperture Hypothalamus Optic chiasma Gray matter Mammillary bodies White matter Pituitary gland Cortex Nuclei Medulla Oblongata Pyramids Decussation of the pyramids Olive Inferior olivary nucleus Reticular formation  13.1b Basic Parts and Organization of the Brain The brain can be classified into four regions: Brain stem Midbrain, pons, and medulla Cerebellum Diencephalon Cerebrum Composed of two cerebral hemispheres  Ventricles of the Brain Expansions of the brain’s central cavity Filled with cerebrospinal fluid Lined with ependymal cells Continuous with each other Continuous with the central canal of the spinal cord  Lateral ventricles Septum pellucidum Paired lateral ventricles lie in the cerebral hemispheres Horseshoe shape reflects the bend of the hemispheres during development Anteriorly, the two ventricles lie close together Separated by a then median membrane called the septum pellucidum  Third Ventricle Interventricular foramen The Third Ventricle lies in the diencephalon Anteriorly it connects to each lateral ventricle through an interventricular foramen  Cerebral aqueduct The cerebral aqueduct is the thin, tube-like central cavity in the midbrain It connects the third and fourth ventricles  The fourth ventricle lies in the brain stem Three openings occur in its walls Two lateral apertures in the walls One median aperture in the roof These holes connect the ventricles with the subarachnoid space, which surrounds the whole CNS This connection allows CSF to fill both the ventricles and the subarachnoid space Lateral aperture Median aperture Lateral aperture Fourth Ventricle Central Canal The fourth ventricle connects caudally to the Lateral aperture Central Canal central canal of the spinal cord  Distribution of Gray Matter and White Matter Gray and white matter have a unique distribution in the brain White matter Lateral ventricles Gray matter- neuron cell bodies White matter- myelinated axons Brain has an inner region of gray matter adjacent to the hollow ventricles Collectively, we can refer to these inner regions of grey matter as brain nuclei These inner regions of gray matter are then surrounded by white matter Brain also has an additional layer of grey matter external to the white matter This is known as a cortex Cerebellar cortex Cerebral cortex Outer regions of grey matter Inner regions of grey matter (Cortex) (Brain nuclei)  13.1c The Brain Stem The brain stem includes Midbrain Pons Medulla oblongata  13.1c The Brain Stem Brian stem lies within the posterior cranial fossa of the skull, on the basilar part of the occipital bone Has 4 general functions: Acts as a passageway for all the fiber tracts running between the cerebrum and the spinal Midbrain cord Pons Heavily involved with the innervation of the face and the head Medulla oblongata Produces the rigidly programmed, automatic behaviors necessary for survival Spinal cord Integrates auditory reflexes and visual reflexes.  The Medulla Oblongata Brain stem, Ventral View Most caudal part of brain stem. Is continuous with the spinal cord A part of the fourth ventricle lies dorsal to the superior half of the medulla Major fiber tracts and brain nuclei: Pyramids: MIDBRAIN Two longitudinal ridges that flank the ventral midline of the medulla. Formed by large fiber tracts (pyramidal tracts) that originate in the cerebrum and descend through the brain stem and spinal cord PONS carrying voluntary motor output to the spinal cord. At the caudal end of the medulla, 70-90% of these fibers cross over to MEDULLA the opposite site of the brain at a point called the decussation of the pyramids. As a result, each cerebral hemisphere controls the voluntary Pyramids movements of the opposite side of the body. Decussation of pyramids SPINAL CORD  The Medulla Oblongata Brain stem, Left Lateral View Just lateral to each pyramid is the… Olive: Relay station for sensory information traveling to the cerebellum, especially for proprioceptive information ascending from the spinal cord. Inferior olivary nucleus (large wavy fold of gray matter viewable in cross section) DORSAL MIDBRAIN Cross section through medulla PONS Inferior olivary nucleus MEDULLA Olive Pyramid Olive Pyramid VENTRAL SPINAL CORD  The Medulla Oblongata Running through the core of the brain stem is a Cross section through medulla loose collection of nuclei called the: DORSAL Reticular formation Raphe nuclei Reticular Formation Medial nuclear group Lateral nuclear group Medial nuclear group Raphe nuclei Cardiac center: adjusts the force and rate of heartbeat Vasomotor center: regulates blood pressure via constricting or dilating the bodies vessels Medullary respiratory center: controls the rhythm and Lateral nuclear group rate of breathing Inferior olivary Inferior olivary nucleus nucleus Olive Olive Pyramids VENTRAL  The Pons Brain stem, Left Lateral View The pons is a bulge wedged between the medulla and the midbrain Dorsally, it is separated from the cerebellum by the fourth ventricle “Pons” = “bridge” Forms a ventral bridge between the brain stem and the cerebellum. MIDBRAIN PONS MEDULLA SPINAL CORD  The Pons Cross section through pons DORSAL The pons contains Pyramidal motor tracts coming from the cerebral cortex pass through the pons ventrally Cerebellar peduncles Pontine nuclei Reticular Connect portions of the cerebral cortex and formation cerebellum nuclei Send axons to cerebellum through the middle cerebellar peduncles Reticular formation nucelli in the pons are also viewable in cross section. Pyramidal motor tracts Pontine nuclei VENTRAL  The Midbrain Brain stem, Ventral View Most rostral of the three brainstem regions. Lies between the diencephalon and the pons. Central cavity is the cerebral aqueduct, which divides the midbrain into the tectum (“roof”) and the paired cerebral peduncles. DORSAL Cerebral aqueduct MIDBRAIN Tectum PONS MEDULLA Cerebral peduncles VENTRAL SPINAL CORD  The Midbrain Cerebral peduncles contain pyramidal motor tracts Cross section through midbrain descending from the cerebrum toward the spinal cord. DORSAL Ventral part of each of the peduncles that contains these tracts is called the crus cerebri. Substantia nigra (“black substance”) are the two darkly Red Nucleus Substantia nigra pigmented brain nuclei embedded in the white matter of the midbrain. Neuronal cell bodies contain dark melanin pigment. Pigment is often produced as a byproduct of synthesizing the neurotransmitter dopamine Functionally linked to other nuclei in the cerebrum (basal ganglia) and is involved in controlling voluntary motor movements. Cerebral Degeneration of these neurons is the cause of peduncles Parkinson’s disease. Crus cerebri Red nucleus is deep to the substania nigra. Reddish hue due to rich blood supply and iron pigments. Minor role in motor function, helps to bring about flexion VENTRAL of the limbs.  The Midbrain Superior colliculi- aid in visual reflexes (eye tracking) Cross section through midbrain Inferior colliculi (not shown)- aid in auditory reflexes (startle Periaqueductal gray matter DORSAL responses to loud sounds) Superior colliculi Periaqueductal gray matter- surrounds the cerebral aqueduct; contains nuclei that contribute to nerves that Red Nucleus Substantia nigra control the muscles that move the eyes. Cerebral peduncles Crus cerebri VENTRAL  13.1d The Cerebellum The “brain cauliflower” 1. Receives information from the cerebellum on the movements being planned. 2. Compares these “plans” with the current body position and movements. 3. Sends instructions back to the cerebral cortex on how to resolve any differences between intended movements and the current position of the body. Great for “fine-tuning” movements… Excellent for learning a new motor skill: -Riding a bike -Playing an instrument “Motor memory” -Hitting a softball Aids also in language processing, problem solving, task planning…. Overall, it’s cognitive functions may be to recognize, use, and predict sequences of events that we experience or perceive.  The Cerebellar Peduncles Fibers to and from the cerebellum are ipsilateral  13.1e The Diencephalon Brain stem, Ventral View The diencephalon is above the brainstem. DIENCEPHALON Forms the central core of the forebrain Surrounded by the cerebral hemispheres Composed of three paired structures BRAINSTEM: Thalamus MIDBRAIN Hypothalamus Epithalamus (not covered) PONS Border the third ventricle Primarily composed of gray matter MEDULLA SPINAL CORD DIENCEPHALON  The Thalamus Makes up 80% of the diencephalon Contains approximately a dozen major nuclei Act as relay stations for incoming sensory message Afferent impulses converge on the thalamus Synapse in at least one of its nuclei Medial dorsal Lateral dorsal Nuclei organize and amplify or tone nucleus Internal nucleus Lateral posterior down signals medullary lamina nucleus Send axons to regions of the cerebral Anterior Pulvinar Medial nuclei cortex geniculate body “Gateway to to the cerebral cortex” Reticular nucleus Lateral geniculate Every part of brain communicating with Ventral Ventral Ventral postero- body cerebral cortex relays signals through anterior lateral lateral thalamic nuclei! The main thalamic nuclei. (The reticular nuclei that “cap” the thalamus laterally are depicted as curving translucent structures.)  The Hypothalamus On underside of brain, found between the optic chiasma (where optic nerves cross and enter the brain) and the mammillary bodies (rounded projections) Pituitary gland projects inferiorly form hypothalamus. Contains approximately a dozen nuclei Main visceral control center of the body Functions include the following Control of the ANS Control of emotional responses Regulation of body temperature Regulation of hunger and thirst sensations Control of behavior Optic Mammillary chiasma body Regulation of sleep-wake cycles Pituitary Control of the endocrine system gland Formation of memory The main hypothalamic nuclei