The Brain The Spinal Cord Spinal Cord Mass

The Brain

The Spinal Cord • Spinal Cord – Mass of nerve tissue located in the vertebral canal – Extends from Medulla Oblongata to 2 nd lumbar vertebrae – Transmits electrical information to and from the brain, limbs, trunk, and organs of the body – Protected by ligaments, fat, meninges, and cerebral spinal fluid • Spinal Nerves – Pathways of communication between spinal cord and specific nerves of the PNS – Connects CNS to sensors, muscles, and glands

The Brain Stem Basics • Responsible for basic life functions: breathing, heartbeat, and blood pressure • Part of the brain between the spinal cord and diencephalon • Contains: – Midbrain – Pons – Medulla

The Brain Stem Details • Midbrain – Station for info that passes between spinal cord and cerebrum or cerebellum and cerebrum – Relays impulses for vision, hearing, and touch • Ex: eye movements and startle reflex • Pons – Bridge that joins cerebellum with cerebrum • Medulla (Oblongata) – Contains sensory and motor neurons – Regulates heart rate and breathing – Reflex for swallowing, vomiting, coughing, sneezing, hiccupping

The Diencephalon Basics • Responsible for relaying sensory information between brain regions • Connects structures of the endocrine system with the nervous system • Contains: – Thalamus – Hypothalamus – Pineal Gland

The Diencephalon Details • Thalamus – Structure where all sensory impulses (except smell) pass through – Transmits motor information from cerebellum to cerebrum • Hypothalamus – Regulates homeostasis • Sleep, hunger thirst, temp, blood pressure, fluids, emotions, behavior, etc • Pineal Gland – Apart of the endocrine system – Secretes melatonin • Promotes sleepiness

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The Cerebellum • Divided into right and left hemispheres • Connects to the brainstem • Constantly receives sensory impulses • Essential in coordinating movements so they appear skilled, smooth, and graceful, not stiff and jerky • Maintains muscle tone, posture, balance • Damage from trauma/disease disrupts muscle coordination

The Cerebrum • Divided into right and left hemispheres – Hemispheres connected by corpus callosum • Each hemisphere is divided into 4 lobes: – Frontal, Parietal, Temporal, Occipital • Covered by the cerebral cortex – Composed of gray matter (unmyelinated nervous tissue) – During embryonic development folds/rolls to fit into cranial cavity • Gyri (JI-ri): Folds • Sulci (pl. )/Sulcus (singular): Shallow grooves • Fissures: Deep grooves between folds – Longitudinal fissure separates cerebral hemispheres

Protecting the CNS • Meninges – 3 layers of connective tissue that cover spinal cord and brain – The dura mater is the outer most layer and the toughest • Blood – Brain Barrier – Semipermeable network of blood vessels and nervous tissue – Prevents passage of harmful substances and pathogens from blood into brain – Allows O 2, CO 2, alcohol, and anesthetics into brain tissue • Cerebrospinal Fluid – Fluid that circulates around spinal cord and ventricles of the brain – Carries O 2, glucose, and other chemicals from the blood to nervous tissue – Removes wastes and toxins produced by brain and spinal cord

Review 1) What structure connects the cerebrum’s hemispheres? 2) What structure bridges the cerebrum’s right and left hemispheres? 3) What main structure helps to maintain homeostasis? 4) If your medulla was damaged in a car accident what would happen? Why? 5) What connects the CNS to sensors, muscles, and glands? 6) What structure is found between the spinal cord and diencephalon? 7) Compare and contrast the ways the brain is protected from pathogens, injury, and disease. 8) Which structure allows for the pupillary reflex? 9) What structure maintains muscle tone, posture, balance? 10) What main structure connects the endocrine and nervous system?