Ch 10 Nervous system Nervous Tissue and Brain

Ch. 10 Nervous system: Nervous Tissue and Brain

Function of Relays messages (motor) Monitors changes in body systems (sensory) Responds to stimuli (sensory) Maintain homeostasis (sensory) Integrative – information is brought to CNS info is put together

Central Nervous system Includes brain and spinal cord Control center, coordinate body activities

Peripheral Nervous sys. Nerves that carry messages to and from the central nervous system

Cells of the Nervous System Neuroganglia – glial cells, nerve glue Supports, protect and nourish the neurons

2. Neurons Parts of : Cell body Dendrites – receive impulse Axon – carries impulse away Myelin sheath- white fatty material l Schwann cells (pns) Neurilemma (outdside the sheath) Nodes of Ranvier

Types of Neurons Sensory neurons (afferent) – carries impulse to brain and spinal cord.

Types of Neurons Motor neurons (efferent) – away from brain and spinal cord.

Types of Neurons Interneurons or association neurons – relay impulses from sensory to motor neurons.

White matter vs Gray Matter White matter l White because of myelin Gray matter l Cell bodies, interneurons, nonmyelinated fibers l Nuclei – clusters of cells in CNS Ganglia – cell cluster in PNS l

The Nerve Impulse Action potential – steps in the nerve impulse 3 stages of : polarization, depolarization, repolarization

Step 1: Polarization Resting state of a neuron Sodium/possium pump – sodium ions out of cells and potassium ions into cells

Polarization continued Inside of the cell is – charged Outside of cell is + charged Due to sodium-potassium pump l 2 K+ ions go in as 3 Ca++ go out http: //faculty. washington. edu/chudler/intro b. html

Step 2: Depolarization Due to stimulation Inside of the neuron becomes + charged. Na+ rushes into the cell

Step 3: repolarization Return to resting state Due to the pumping out of K+. Na+ blocked Inside of cell negative Continues to synapse

Synapse

Brain: structure and function 4 main parts of the brain: Cerebrum Diencephalon Brain stem Cerebellum

Cerebrum Largest part of the brain Corpus collosum - Right and left hemispheres Cerebral cortex – gray matter covering the cerebrum

Cerebrum Continued Function of cerebral cortex – learning, reasoning, language, memory Markings of: gyri (elevations) and sulci (grooves)

Diencephalon Thalamus – l Relay station for sensory fibers between cerebrum and lower brain. Hypothalamus - l l l Body Temperature Emotions Hunger Thirst Circadian Rhythms

Cerebellum Coordinatin of voluntary muscle movements Muscle tone

Brain Stem Midbrain-relay station, hearing, vision Pons – relay station, breathing rate Medulla Oblongata – relay center, heart rate, blood pressure, respiration

Ventricles

Protection Bone Meninges – 3 layers of connective tissue Cerebrospinal fluid – Blood brain barrier – cells associated with blood vessels that supply the brain with blood.

Aging Brain Enlargement of the ventricular system: the volume of the ventricles Widening of sulci (the grooves) on the surface of the brain. Reduced brain weight and brain volume: loss of neurons. Neurological disorders: Alzheimer's disease, Parkinson's disease and stroke are more common in the elderly.