The Nervous System Part 1 “Organization of the Nervous System”

Parkinson’s and Alzheimer’s disease both affect the nervous system. *The nervous system is the “wiring” that keeps the body connected and functioning. *Works with the endocrine system to keep the body in homeostatic balance. *The nervous system also enables us to learn, form memories and allow for critical and creative thinking in ways not fully understood. Parkinson’s kills dopamine producing cells, so there is nothing to stop muscle contractions. Alzheimer's affects memory cells.

Organization of the Nervous System Central Nervous System (CNS) Central Nervous System (CNS) Brain and spinal cord Brain and spinal cord makes decisions makes decisions made up of tracts of fibers made up of tracts of fibers Peripheral Nervous System (PNS) Peripheral Nervous System (PNS) Cranial and spinal nerves Cranial and spinal nerves Relays info to and from the CNS Relays info to and from the CNS made up of Nerves made up of Nerves

Organization of the Peripheral Nervous System Afferent Divisions (Sensory messages) Afferent Divisions (Sensory messages) carries info towards the CNS carries info towards the CNS Efferent Divisions (Motor messages) Efferent Divisions (Motor messages) carries info away from the CNS carries info away from the CNS

Organization of the Peripheral Nervous System Somatic Nervous System (SNS) Voluntary Somatic Nervous System (SNS) Voluntary Controls skeletal muscles Controls skeletal muscles Somatic sensory division :(afferent) stimulus from muscle receptors to the CNS. Somatic sensory division :(afferent) stimulus from muscle receptors to the CNS. Somatic motor division: (efferent) response from CNS to skeletal muscles Somatic motor division: (efferent) response from CNS to skeletal muscles Autonomic Nervous System (ANS) Involuntary Autonomic Nervous System (ANS) Involuntary Controls smooth and cardiac muscles, glands Controls smooth and cardiac muscles, glands Visceral sensory division: (afferent) stimulus from organ receptors to CNS. Visceral sensory division: (afferent) stimulus from organ receptors to CNS. Visceral motor division: (efferent) response from CNS to organs Visceral motor division: (efferent) response from CNS to organs Sympathetic and parasympathic Sympathetic and parasympathic

Divisions of Autonomic Nervous System Involuntary part of the peripheral nervous system Involuntary part of the peripheral nervous system Sympathetic Division Sympathetic Division “Fight or flight” response “Fight or flight” response Takes over to deal with immediate threats Takes over to deal with immediate threats Parasympathetic Division Parasympathetic Division “Rest and repair” division “Rest and repair” division Coordinates normal resting activities Coordinates normal resting activities

The Nervous System Part 2 “Cells of the Nervous System”

Cells of the Nervous System Neurons (nerve cells) Neurons (nerve cells) Excitable cells that transmit signals Excitable cells that transmit signals Neuroglia (glial cells) Neuroglia (glial cells) Are support cells for the neurons Are support cells for the neurons Sometimes called “nurse” cells Sometimes called “nurse” cells

Neurons Key Parts No centrioles because amitotic No centrioles because amitotic Soma or cell body -contains the nucleus Nissl bodies - ribosomes to make neurotransmitters. Dendrites(receptors) - receive signals Axon - long arm extending away from cell body, transmits signal away from cell body to next neuron Axons can have side branches called axon collaterals.

Path of Nerve Impulse Dendrite  cell body  axon  synapse 

Structural Classification of Neurons A. Multipolar Most neurons in brain and spinal cord are multipolar Most neurons in brain and spinal cord are multipolar B. Bipolar Only one axon and dendrite Only one axon and dendrite Least numerous Least numerous Found in eye, inner ear and nose Found in eye, inner ear and nose C. Unipolar One end branches toward CNS while the other goes toward PNS Two processes form a long axon Carries both sensory and motor info.

TYPES OF GLIAL CELLS A. Astrocytes B. Microglia C. Ependymal cells D. Oligodendrocytes E. Schwann cells F. Satellite cells

Astrocyte

Astrocytes- ‘star cells’ Found only in the CNS Found only in the CNS Largest and most numerous type of glia Largest and most numerous type of glia Bridge between capillaries and neurons Bridge between capillaries and neurons filter harmful substances and transport nutrients. filter harmful substances and transport nutrients. They form the blood- brain barrier (BBB) They form the blood- brain barrier (BBB)

Microglia

Microglia Found in CNS Found in CNS Small and stationary Small and stationary Fight infection in brain tissue through phagocytosis. Fight infection in brain tissue through phagocytosis.

Ependymal cells

Found only in CNS Found only in CNS Line fluid-filled cavities in the brain and spinal cord Line fluid-filled cavities in the brain and spinal cord Form Cerebrospinal fluid (CSF) Form Cerebrospinal fluid (CSF) Cilia helps keep fluid circulating through brain and spinal cord. Cilia helps keep fluid circulating through brain and spinal cord.

Myelin Whitish fatty material that increases speed of conduction in an axon Whitish fatty material that increases speed of conduction in an axon Insulates nerve fiber axons Insulates nerve fiber axons Myelinated fibers are called white matter Myelinated fibers are called white matter Non-myelinated fibers are called gray matter Non-myelinated fibers are called gray matter Destroyed in individuals with multiple sclerosis Destroyed in individuals with multiple sclerosis

Schwann Cells

Found only in PNS Found only in PNS Form myelin sheaths around cells of the PNS. Form myelin sheaths around cells of the PNS. Gaps between schwann cells are called nodes of ranvier. Gaps between schwann cells are called nodes of ranvier.

Oligodendrocytes

Oligodendrocytes Found only in CNS Found only in CNS Produce the fatty myelin sheath around the nerve fibers of CNS Produce the fatty myelin sheath around the nerve fibers of CNS Hold nerve fibers together Hold nerve fibers together

Quick Check 1. What is the difference between neurons and glial cells? 2. What does myelin do? 3. Which glial cell makes myelin in the CNS?