Lecture 8 - CNS PDF

Mon, Oct 21 Nervous System, Part 1: The Central Nervous System Development of the nervous system Layout of the nervous system Cells of the central nervous system (brain and spinal cord) Brain regions A bit about the spinal cord Reading: Ch. 13, Sec 1 and 2  Development of t...

Mon, Oct 21 Nervous System, Part 1: The Central Nervous System Development of the nervous system Layout of the nervous system Cells of the central nervous system (brain and spinal cord) Brain regions A bit about the spinal cord Reading: Ch. 13, Sec 1 and 2  Development of the Nervous System The layout of the nervous system (like everything in the body) is dictated by what happens when we’re an embryo By Week 6: All animals (including humans) The neural crest starts forming develop from the body’s sensory neurons 3 embryonic layers: The neural tube starts forming the brain, spinal cord, and motor neurons In the 4th week of development, part of the top layer pulls into the middle layer to form the nervous system Figures from Human Anatomy, 9th Ed. by Elaine Marieb (2022)  Development of the Nervous System The layout of the nervous system (like everything in the body) is dictated by what happens during embryonic development The neural tube divides into segments over the coming weeks to form the fetal brain and spinal cord Development of the Nervous System The head-end of the neural tube wraps and twists around itself as it grows to form a newborn brain From Human Anatomy, 9th Ed. by Elaine Marieb Fig. 13.2 Layout of the Mature Nervous System  Layout of the Mature Nervous System m e S o if ic p e c (brain and spinal cord) S l u s i m u t S curs Oc Usually opens some sort of gated Na+ channels (they open only in urons response to that nse te specific stimulus integra a respo Interne Cells of the Central Nervous System Space containing Ventricles cerebrospinal fluid mal Ependy Cells line the Neurons ventricle s form action potentials and synapses! Oligodendrocytes make myelin Br intersain Microglia tit fluid ial brain defense and housekeeping Fig. 5-3, p. 110 Cerebrospinal Fluid: Produced in the ventricles deep in the brain Percolates around the brain and spinal cord Absorbed in the spinal column From: ”Human Physiology, 7th Edition” by Lauralee Sherwood (2012) Cells of the Central Nervous System Space containing Ventricles cerebrospinal fluid mal Ependy Cells line the Neurons ventricle s form action potentials and synapses! Astrocytes form the blood- brain barrier Oligodendrocytes Capillary make myelin Br intersain Microglia tit fluid ial brain defense and housekeeping Fig. 5-3, p. 110  The Blood-Brain Barrier Endothelial In the brain and spinal cord, cells astrocytes send projections to capillaries Cause tight junctions to form between the cells that make up the capillary walls Tight junctions close the capillary pores, prevent paracellular flow (i.e., substances can’t move around cells) Now the only exchange between the blood and the brain fluid can Pores occur via transcellular flow (substances have to move through the A typical capillary of the body capillary cells using membrane transport mechanisms we already learned about is very leaky by design — highly specific!!) Protective Layers of the CNS Skin and sensory nerves Skull and Vertebrae Meninges 3 protective membranes: - Dura Mater — “tough mother” - Pia Mater — “gentle mother” - Arachnoid Mater — “spidery mother” Cerebrospinal Fluid (CSF) - Provides a cushion for brain and spinal cord - Provides nutrients, removes waste products from the brain tissue  Regions of the Central Nervous System Cerebral Cortex Cerebral cortex Thought, Consciousness, Movement, Integration “gray matter” is on surface “white matter” underneath Basal nuclei (lateral to thalamus) Basal Nuclei Fine-tune muscle activity, inhibit inappropriate actions Thalamus Thalamus (medial) Relay of all sensory information, except the sense of smell Hypothalamus Hypothalamus Seat of homeostatic control, master gland of the endocrine system Cerebellum Pituitary Cerebellum Many regulatory hormones! Coordination of movements, “muscle memory” Midbrain Brain Stem Many basic processes Brain stem Pons essential for animal life (digestive centers, respiratory centers, cardiovascular centers) Medulla Spinal Cord Nerve pathways, many reflexes The Cerebral Cortex is Divided Into Lobes  The Cerebral Cortex is Divided Into Lobes Primary motor cortex Supplementary motor area (voluntary movement) Somatosensory cortex (on inner surface—not visible; (somesthetic sensation programming of complex movements) Central and proprioception) sulcus Posterior parietal cortex Premotor cortex (coordination (integration of somatosensory of complex movements) and visual input; important for complex Prefrontal association cortex movements) (planning for voluntary activity; decision making; Wernicke’s area personality traits) (speech understanding) Parietal lobe Frontal lobe Broca’s area (speech formation) Primary auditory cortex surrounded by higher-order auditory cortex (hearing) Occipital lobe Primary visual cortex Limbic association cortex surrounded by higher- (mostly on inner and bottom order visual cortex (sight) surface of temporal lobe; motivation and emotion; memory) Temporal lobe Cerebellum Spinal cord Brain stem (a) Regions of the cerebral cortex responsible for various functions Fig. 5-8a  The Spinal Cord White Matter: Gray matter: Tracts of Axons Many, many Interneurons Dorsal Root s r ve Sensory t ne n s Information ere r ve Action Af f t ne Potentials ren Ventral root fe Coming Ef From The Sensory Receptors Motor Information Action Potentials Going Spinal nerves (30 pairs) To The part of the peripheral Effectors nervous system