Nervous System INervous System IChapter 11Chapter 11

Nervous SystemNervous System

The nervous system is the master controlling The nervous system is the master controlling and communicating system of the bodyand communicating system of the body

Every thought, action, and emotion reflects its Every thought, action, and emotion reflects its activity.activity.

Three overlapping functionsThree overlapping functions Millions of sensory receptors to monitor changes Millions of sensory receptors to monitor changes

occurring both inside and outside the body. (called occurring both inside and outside the body. (called sensory input)sensory input)

It processes and interprets sensory input and decides It processes and interprets sensory input and decides what should be done at each momentwhat should be done at each moment

It causes a response (called motor output), by It causes a response (called motor output), by activating effector organsactivating effector organs

This next slide is on pg 389 in your book!This next slide is on pg 389 in your book!

Nervous SystemNervous System

Central Nervous System Central Nervous System and Peripheral Nervous and Peripheral Nervous

System.System. Central Nervous System (CNS) composed Central Nervous System (CNS) composed

of the brain and spinal cordof the brain and spinal cord Peripheral nervous system (PNS) Peripheral nervous system (PNS)

composed of the nervous (cranial and composed of the nervous (cranial and spinal) that connects the CNS to other spinal) that connects the CNS to other body parts. body parts.

Together these systems provide three Together these systems provide three general functions sensory, integrative and general functions sensory, integrative and motor. motor.

Autonomic and Somatic Nervous Autonomic and Somatic Nervous SystemsSystems

Autonomic: Autonomic: PortionPortion of the of the nervous system nervous system that controls the that controls the actions of the actions of the viscera.viscera. (such as heart, (such as heart, stomach, intestines, and stomach, intestines, and various glands)various glands)

Somatic: Somatic: PortionPortion of the of the nervous system nervous system that controls skin that controls skin and skeletal and skeletal muscles.muscles.

Two Divisions of Autonomic Two Divisions of Autonomic Nervous SystemsNervous Systems

Sympathetic Sympathetic Division:Division: Mobilizes body Mobilizes body systems. Arises systems. Arises from the thoracic from the thoracic and lumbar regions and lumbar regions of the spinal cord.of the spinal cord.

Parasympathetic Parasympathetic Division: Division: Conserves Conserves energy and energy and promotes promotes housekeeping housekeeping functions during rest. functions during rest. Arises from the Arises from the brain and sacral brain and sacral regions of the spinal regions of the spinal cord. cord.

The nervous system is composed The nervous system is composed predominantly of neural tissue. predominantly of neural tissue.

It also includes some blood vessels and It also includes some blood vessels and connective tissue. connective tissue.

Neural Tissue consists of two cell typesNeural Tissue consists of two cell types Nerve cells called Nerve cells called NeuronsNeurons NeurogiliaNeurogilia or glial cells or glial cells

Nervous SystemNervous System

Neurons and Neuroglial CellsNeurons and Neuroglial Cells

NeuronsNeurons-- A nerve A nerve cell that consists of a cell that consists of a cell body and its cell body and its processes. processes.

Neuroglial-Neuroglial- specialized cell that specialized cell that produces myelin, produces myelin, communicates communicates between cells, and between cells, and maintains the ionic maintains the ionic environment, as well environment, as well as other functions.as other functions.

They are specialized to react to physical and They are specialized to react to physical and chemical changes in their surroundings. chemical changes in their surroundings.

While variable in size and shape, all neurons While variable in size and shape, all neurons have three parts. Dendrites receive information have three parts. Dendrites receive information from another cell and transmit the message to from another cell and transmit the message to the cell body. The cell body contains the the cell body. The cell body contains the nucleus, mitochondria and other organelles nucleus, mitochondria and other organelles typical of eukaryotic cells. The axon conducts typical of eukaryotic cells. The axon conducts messages away from the cell body. messages away from the cell body.

The information is in the form of of bioelectric The information is in the form of of bioelectric signals called nerve impulses.signals called nerve impulses.

Nerves are bundles of axons. Nerves are bundles of axons.

NeuronsNeurons

NeuronsNeurons

                                                                                            

You need to use a plain white sheet of You need to use a plain white sheet of paper and properly draw, color, and label paper and properly draw, color, and label a neuron.a neuron.

You may use the drawing in this You may use the drawing in this PowerPoint or on pg 392 in your book.PowerPoint or on pg 392 in your book.

Draw, Color and Label

NeuronsNeurons vary in size and shape, and in function. vary in size and shape, and in function. Structure is differentStructure is different..

BipolarBipolar- a cell body with two processes, one axon - a cell body with two processes, one axon and one dentrite. (Specialized parts of eyes, nose and and one dentrite. (Specialized parts of eyes, nose and ears.)ears.)

UnipolorUnipolor- Cell body with a single process that divides - Cell body with a single process that divides into two branches and functions as an axon.(cell body into two branches and functions as an axon.(cell body in ganglion outside the brain or spinal cord)in ganglion outside the brain or spinal cord)

MultipolarMultipolar- Cell body with many processes, one of - Cell body with many processes, one of which is an axon, the rest dendrites.( Most common which is an axon, the rest dendrites.( Most common type of neuron in the brain and spinal cord)type of neuron in the brain and spinal cord)

Classification of Classification of NeuronsNeurons

When function is different…When function is different… Sensory neuronSensory neuron conducts nerve impulses from conducts nerve impulses from

receptors in peripheral body parts into the brain receptors in peripheral body parts into the brain or spinal cordor spinal cord

InterneuronInterneuron-Transmits nerve impulses between -Transmits nerve impulses between neurons within the brain and spinal cordneurons within the brain and spinal cord

Motor NeuronsMotor Neurons- conduct nerve impulses from - conduct nerve impulses from the brain or spinal cord out to effectors- muscle the brain or spinal cord out to effectors- muscle or glands. or glands.

Classification of Classification of NeuronsNeurons

The SynapseThe Synapse

The operation of the nervous system depends The operation of the nervous system depends on the flow of information through chains of on the flow of information through chains of neurons functionally connected by synapses.neurons functionally connected by synapses.

The synapse is a junction between two cells. The synapse is a junction between two cells. A synaptic cleft is the gap between parts of the A synaptic cleft is the gap between parts of the

two cells at a synapse. two cells at a synapse. Synapse can occur between two neurons, a Synapse can occur between two neurons, a

receptor cell and a neuron, or a neuron and an receptor cell and a neuron, or a neuron and an effector. effector.

Between adjacent neurons, there is a Between adjacent neurons, there is a microscopic gap called the synaptic microscopic gap called the synaptic cleft. cleft.

However small, the electrical signal However small, the electrical signal carrying a message cannot bridge carrying a message cannot bridge the synaptic cleft as it is.the synaptic cleft as it is.

The Synapse The Synapse TransmissionTransmission

The SynapseThe Synapse

The neuron conducting impulses toward the The neuron conducting impulses toward the synapse is the presynaptic neuronsynapse is the presynaptic neuron

The neuron transmitting the electrical signal The neuron transmitting the electrical signal away from the synapse is the postsynaptic away from the synapse is the postsynaptic neuron. neuron.

There are two varieties of synapses: There are two varieties of synapses: ElectricalElectrical ChemicalChemical

The Electrical The Electrical SynapseSynapse

Less common variety.Less common variety. They intimately connect the cytoplasm of They intimately connect the cytoplasm of

adjacent neurons and allow ions and small adjacent neurons and allow ions and small molecules to flow directly from one neuron to the molecules to flow directly from one neuron to the next.next.

Found in regions of the brain responsible for Found in regions of the brain responsible for certain stereotyped movements. certain stereotyped movements. Jerking of the eyesJerking of the eyes Involved in emotions and memory.Involved in emotions and memory. Abundant in embryonic nervous tissue.Abundant in embryonic nervous tissue.

The chemical synapse are specialized for The chemical synapse are specialized for release and reception of chemical release and reception of chemical neurotransmitters.neurotransmitters.

The solution to this is the synapse, an The solution to this is the synapse, an elegant way of bridging the gap chemically. elegant way of bridging the gap chemically. The electrical impulse triggers the release of The electrical impulse triggers the release of certain chemical substances into the gap. certain chemical substances into the gap. These substances are called These substances are called neurotransmitters and are carried over the neurotransmitters and are carried over the small synaptic cleft by diffusion.small synaptic cleft by diffusion.

The Chemical The Chemical SynapseSynapse

Once on the other side of the cleft, Once on the other side of the cleft, the neurotransmitters bind to certain the neurotransmitters bind to certain proteins, called receptors, that are proteins, called receptors, that are attached to the cell surface of the attached to the cell surface of the receiving cell. The binding of the receiving cell. The binding of the transmitter to the receptor leads to transmitter to the receptor leads to the generation of a new electrical the generation of a new electrical impulse. The gap has been bridged!impulse. The gap has been bridged!

The Synapse The Synapse TransmissionTransmission

The SynapseNerve Signaling – An The SynapseNerve Signaling – An IntroductionIntroduction

http://Synaptic Cleft Videohttp://Synaptic Cleft Video

Synapse TransmissionSynapse Transmission

Impulses usual travel from dendrite or cell body, then Impulses usual travel from dendrite or cell body, then along the axon to a synapse.along the axon to a synapse.

Axons have synaptic knobs at their distal ends that Axons have synaptic knobs at their distal ends that secrete neurotransmitters.secrete neurotransmitters.

The neurotransmitter is released when a nerve impulse The neurotransmitter is released when a nerve impulse reaches the end of an axon, this opens two channels Nareaches the end of an axon, this opens two channels Na++ and Caand Ca2+2+

This surge of CaThis surge of Ca2+ 2+ acts as a messenger, directing synaptic acts as a messenger, directing synaptic vesicles to empty contents.vesicles to empty contents.

Then the neurotransmitter diffuses across the synaptic Then the neurotransmitter diffuses across the synaptic cleftcleft

A neurotransmitter reaching the dendrite or cell body on A neurotransmitter reaching the dendrite or cell body on the distal side of the cleft triggers a nerve impulse. the distal side of the cleft triggers a nerve impulse.

The Synapse The Synapse TransmissionTransmission

NeurotransmitterNeurotransmitter

Different neurotransmitters are being Different neurotransmitters are being released on different occasions. The released on different occasions. The intensity and strength of the intensity and strength of the electrical impulse will decide which electrical impulse will decide which neurotransmitter to be released.neurotransmitter to be released.

NeurotransmittersNeurotransmitters

NeurotransmitterNeurotransmitter

Not all neurotransmitters are known, but Not all neurotransmitters are known, but among the more profoundly mapped among the more profoundly mapped

Some medical disorders are caused by the Some medical disorders are caused by the dysfunction of neurotransmission in the dysfunction of neurotransmission in the central nervous system, for example lack central nervous system, for example lack of certain neurotransmitters. of certain neurotransmitters.

One such disorder is Parkinson's disease.One such disorder is Parkinson's disease.

NeurotransmittersNeurotransmitters