Due Today: 2.1.3 Map-A-Brain Swim Cap Completed Chart Conclusion Questions Rubric ________________________________________________________ BRAIN REVIEW WORKSHEET BRAIN QUIZ NEXT CLASS PERIOD! The Neuron Notes PPT 2.2.1 : The Neuron Part I Basic Neuron Design (work in Pairs) Follow Directions agmiller@avon-schools.org Printer: al-248-q1 Part II Relaying The Message (individually-may hand draw, MS Word, or Inspiration)

The Neuron Nervous System

Basic Divisions of the Nervous System: CNS Central nervous system (CNS) Brain and spinal cord - a long bundle of neurons that carries messages to and from the body to the brain that is responsible for very fast, lifesaving reflexes. Integrating and command center

Basic Divisions of the Nervous System: PNS Peripheral nervous system (PNS) Outside the CNS Nerves extending from brain and spinal cord Cranial nerves Spinal nerves Link all regions of the body to the CNS

Sensory Input and Motor Output Sensory signals picked up by sensory receptors Carried by afferent nerve fibers of PNS to the CNS – nerves that transmit info to the CNS Motor signals are carried away from the CNS Carried by efferent nerve fibers of PNS to effectors – nerves that transmit info from CNS to the PNS (organs)

Nervous Tissue Cells are densely packed and intertwined Two main cell types Neurons – transmit electrical signals Support cells - neuroglial cells Surround and wrap neurons

The Neuron The human body contains billions of neurons Basic structural unit of the nervous system Specialized cells conduct electrical impulses along the plasma membrane Longevity – can live and function for a lifetime Do not divide – fetal neurons lose their ability to undergo mitosis – do NOT have centrioles High metabolic rate – require abundant oxygen and glucose

Basic Neuron Structure

The Cell Body Many Mitochondria Contains the cell’s nucleus round, centrally located structure contains DNA controls protein manufacturing directs metabolism no role in neural signaling Many Mitochondria Nissl Bodies- groups of ribosomes – make protien

Dendrites Information collectors Receive inputs from neighboring neurons Inputs may number in thousands If enough inputs, the cell’s AXON may generate an output Surface is rough Branch near cell body

Axons Takes information away from cell body Smooth surface One axon per cell, 2 distinct parts tubelike structure branches at end that connect to dendrites of other cells Axon Terminal Releases information to the next neuron/dendrite

Myelin Sheath White fatty casing on axon Acts as an electrical insulator Made by Schwann Cells – in the PNS When present, increases the speed of neural signals down the axon

****Oligodendroglia*** Cells that make insulates the axons in the CNS – specifically the brain. One single oligodendroglia can insulate up to 50 axons Difference – one Schwann cell is needed for one axon in the PNS

Nodes of Ranvier In between the areas of myelin sheath, Nodes of Ranvier or bare patches exist. The nerve impulse will jump form node to node greatly increasing the speed of nerve transmission. can produce transmission speeds of up to 200 meters per second and explains the speed at which we can react to potentially harmful stimuli.

Neurons and Synapses Types of Neurons Sensory Motor Interneurons

Length of Fibers Location Function Sensory neuron Interneuron Motor Neuron Length of Fibers Long dendrites and short axon Short dendrites and short or long axon Short dendrites and long axons Location Cell body and dendrite are outside of the spinal cord; the cell body is located in a dorsal root ganglion Entirely within the spinal cord or CNS Dendrites and the cell body are located in the spinal cord; the axon is outside of the spinal cord Function Conduct impulse to the spinal cord Interconnect the sensory neuron with appropriate motor neuron Conduct impulse to an effector (muscle or gland)

Motor Neuron Efferent Neuron – Moving toward a central organ or point Relays messages from the brain or spinal cord to the muscles and organs

Sensory Neuron Afferent Neuron – Moving away from a central organ or point Relays messages from receptors to the brain or spinal cord

Interneurons Relays message from sensory neuron to motor neuron Make up the brain and spinal cord

Neuron Types Based on what is coming out of the cell body (also known as the soma)

BiPolar Neuron Has two processes extending from the cell body (example: retinal cells, olfactory epithelium cells. Rare

Unipolar Neuron Have but one process from the cell body. However, that single, very short, process splits into longer processes (a dendrite plus an axon). Unipolar neurons are sensory neurons - conducting impulses into the central nervous system.

Multipolar neurons Are so-named because they have many (multi-) processes that extend from the cell body: lots of dendrites plus a single axon. Functionally, these neurons are either motor (conducting impulses that will cause activity such as the contraction of muscles) or association (conducting impulses and permitting 'communication' between neurons within the central nervous system).