Transcript SBI4U - 9.3
Section 9.3:The Central Nervous System (CNS) Pages 427 - 434 Recap • Current in wire vs. Current in nerves • Action Potentials • Depolarization, Repolarization • Sodium-potassium Pump Active Transport • Synaptic Transmission The Central Nervous System • Includes the brain and the spinal cord • The brain is a concentration of nervous tissue acts as the coordinating centre of the nervous system The Spinal Cord • Carries sensory nerve messages from receptors to the brain • Relays motor nerve messages from the brain to muscles, organs, and glands • A cross-section shows that the spinal cord consists of two types of nerve tissue – white matter and grey matter The Spinal Cord • Core of the spinal cord: contains unmyelinated interneurons (grey matter) • Periphery of cord: both sensory and motor neurons are myelinated (white matter) • Interneurons consist of nerve tracts that connect the spinal cord with the brain • Dorsal nerve tracts: bring sensory information into the spinal cord • Ventral nerve tracts: carry motor information from the spinal cord to the muscles, organs, and glands The Spinal Cord Carry sensory information to spinal cord Carry motor information from spinal cord to muscles, organs and glands The Brain Has Layers • The brain is covered by a three-layer protective membrane called the meninges ▫ Outer layer: dura mater ▫ Middle layer: arachnoid mater ▫ Innermost layer: pia mater • These three membrane layers form the blood-brain barrier, which determines what chemicals will reach the brain The Brain • Our hearing, vision, and sense of smell is unimpressive • Our ability to conceptualize and reason is extremely unique • The human brain is made of 3 distinct regions: the forebrain, the midbrain, and the hindbrain The Forebrain • Contains olfactory lobes – sense smell • Cerebrum (forebrain) – coordinating centre where speech, reasoning, memory, and personality reside • Surface of the cerebrum is called the cerebral cortex – made of grey matter of many folds and fissures • The right side of the forebrain visual patterns or spatial awareness • The left side of the brain linked to verbal skills The Forebrain • Your ability to learn is heavily dependent on the dominance of one of the hemispheres • Corpus callosum allows both hemispheres to communicate • Each hemisphere can be further subdivided into 4 lobes: frontal, temporal, occipital, and parietal Table 1. page 429 The Hindbrain • Joins with the spinal cord • Consists of the cerebellum, pons, and medulla oblongata • Controls breathing movements, the diameter of blood vessels, and heart rate The Hindbrain Pons: relays information between the two regions of the cerebellum and between the cerebellum and the medulla Medulla oblongata: connection between the peripheral and the central nervous system that controls involuntary muscle action Cerebellum: controls limb movements, balance, and muscle tone Human Brain Compared to Chordates Human body drawn in proportion to how many motor nerves control it Case Study: Phineas Gage • 1948 – Thunderous explosion in Cavendish, Vermont • Gage accidently set off blasting caps • A meter long bar entered below the left eye and exited through the skull • Recovered and lived for an additional 12 years • Vision, hearing, balance all remained intact Any Questions?