Chapter 8 Nervous System

Transcription

1 Chapter 8 Nervous System Two message centers: Functions of these systems: 1. * 2. * Overview of the Nervous System Parts: General Functions: Functions Sensory input: Sensation via nerves Integration: interpretation of data by brain and spinal cord Motor Output: Motor response Divisions of the Nervous System The central Nervous System (CNS) Peripheral Nervous System (PNS) Consists of Cranial and spinal nerves Two subdivisions Afferent (sensory) Efferent (motor)

2 Nervous Tissue: Neurons Neuroglia 5 types of Neuroglial cells Structure of a Neuron: Cell Body: Dentrites: Axon: Myelin Sheath: Function: Insulation and conduction of nerve impulse Formed by: Schwann cells in the Oligodendrocytes in the Nodes of Ranvier:

3 Structural Classification of Neurons: Unipolar: axon that enters and exits the cell body Bipolar: one dendrite and one axon Found : Multipolar: many dendrites and axon Where Found? Function? Motor Neurons Efferent Sensory Neurons Afferent Interneurons Association Neurons Structural Classification Uni- Bi- polar Multi- Pathway Stimulated by

4 Motor Neuron: Sensory Neuron: Interneuron: Neuroglial Cells and Transmission of Action Potential 6 Types of Neuroglial or Glial Cells: Glia = greek word for glue Special types of that help and provide for nerve cells. neurons and. Supply and to neurons. one neuron from another. Destroy and remove neurons.

5 Name of the Cell Found in CNS or PNS Function Astrocytes Oligodendrocytes Microglia Cells Ependymal Cells Schwann Cells Satellite Cells Nerve Impulse An that travels along a nerve fiber. Travels about. Rapid and of a small portion of the plasma membrane Nerve Signal Conduction potential followed by an potential Resting Potential Electrical charge across the Inside of cell is compared to the outside Sodium ions Potassium ions

6 Depolarization Neurotransmitters open channels rushes into the cell inside of cell is now Repolarization channels open flows out of the cell Inside becomes more Refractory Period Time which the neuron is In mammals, the absolute refractory period is about and the maximum firing frequency is about impulses per second Synapses The between a nerve cell and another cell. To cross a synapse are released. Transmission across a synapse Neurotransmitters stored in in the terminal Impulse reaches terminal channels open Vesicles fuse with membrane are released Receptors bind to membrane Common Neurotransmitters (ACh) (NE) Once released must be removed from synapse (AChE) breaks down ACh

7 CNS: The Brain and Spinal Cord Gray matter- Brain Structure and Function White matter- Meninges: The Protective Coverings Dura Mater (Outermost) Arachnoid Mater Pia Mater (Innermost) Dura mater- Tough, fibrous, tissue Made of layers Separation of layers to form Collection of and extra Arachnoid Mater- connective tissue CSF in the space CSF-clear fluid, Pia Mater- Very thin layer Follows CSF Made by the lining the ventricles Fills all and the Hydrocephalus- in an infant The Spinal Cord Is an extension of the brain Exits the cranial cavity via Runs through the Ends between L & L Cauda equina (horse s tail) The Vertebral Column Made of individual vertebrae separated by Disk herniation

8 Anatomy of the Spinal Cord Inner with a central canal Outer Spinal Nerves Posterior (dorsal) root of a spinal nerve: ( ) fibers Anterior (ventral) root of a spinal nerve: ( ) fibers Spinal nerve joining of posterior & anterior roots The Human Brain: Gyri- Sulci- Major Sections of the Human Brain The cerebrum The diencephalon: Hypothalamus Thalamus Pineal gland The cerebellum The brainstem

9 Peripheral Nervous System (PNS) All the rest of the nerves of your body Two branches o Nervous System o Nervous System Nerve Anatomy = covers nerve itself = covers bundles of axons = covers individual axons Somatic NS pairs of Cranial Nerves pairs of Spinal Nerves Types of Nerves Mixed = Sensory = Motor = Cranial Nerves Spinal Nerves

10 Nerve Plexus: Name of Plexus Nerves found in plexus Services what part of the body Cranial Nerve # Name of Cranial Nerve Function Type of Nerve I Sense of Smell II Sense of sight III Movement of eyelid and eyeball IV Muscles of the eyes V Muscles for chewing (motor) & pain and touch for face and mouth (sensory) VI Muscles for eye movement VII Sense of taste (sensory) & facial expressions (motor) VIII Sense of Hearing IX Sense of taste (sensory), blood pressure, tongue movement (motor) X Innervates smooth muscle of the gut(motor) & feelings of distension/bloating (sensory) XI Movement of neck muscles XII Movement of the tongue

11 The Autonomic Nervous System Two divisions: Sympathetic ( ) Parasympathetic ( ) General Characteristics of Sympathetic and Parasympathetic Both divisions are (involuntary) Both innervate all Both have 2 and 1 Ganglion: place where of the 2 nd ANS neurons exit outside the CNS Some Important functions of the ANS Regulation of Regulation of Control of secretions from Setup of 2 ANS Neurons Neuron 1 (pre-ganglionic neuron): Cell body (spinal cord) and the axon of the CNS Synapses with neuron 2 in the Neuron 2 (post-ganglionic neuron): Cell body in the and the axon continues to the Dendrites synapse with neuron 1 in the and the axon terminals synapse with the

12 Neuron Setup in the Parasympathetic Nervous System Neuron 1 Neuron 2 The ganglion lies far from the spinal cord Neuron Setup in the Sympathetic Nervous System Neuron 1 Neuron 2 The ganglion lies close to the Spinal cord Origin of Sympathetic Nerves

13 Origin of Sympathetic Nerves Origin of Parasympathetic Nerves Functions of the Sympathetic Division prepares the body for emergencies (Fight or flight) increases heart rate raises blood pressure (vasoconstriction) dilates the pupils dilates the trachea and bronchi Converts liver glycogen into glucose shunts blood away from the skin and organs (vasoconstriction) pushes blood toward the skeletal muscles, brain, and heart Functions of the Parasympathetic Division The housekeeper division Rest and Digest Manages functions associated with a relaxed state Contraction of the pupils Promotes digestion of food Slows down the heart rate and decreased heart contraction Increased blood flow to the visceral organs (GI tract), normal peristalsis inhibits peristalsis in the gastrointestinal (GI) tract inhibits contraction of the bladder and rectum

14 Sympathetic Neurotransmitters Parasympathetic Neurotransmitters Reflexes responses Occur quickly mechanisms Cranial Reflexes: Blinking of eyes with sudden clapping near eyes Spinal Reflexes: Quick movement of hand away from the hot pan Reflex Arc 1. Sensory transducer (hitting of patellar tendon) Motor neuron 5. (muscle contraction)