1 Nervous System Components: Brain, spinal cord, nerves, sense organs, and associated structures. Functions: yWorks with endocrine system to coordinate body activities. yIntegrates and processes information from sense organs. ySends signals (instructions) to muscles and glands. yResponds to internal stimuli. Homeostatic Role: yRegulates most organ activities along with endocrine system.

2 Human Nervous System

3 Functions of Nervous Tissue 1. Sensory Input: Conduction of signals from sensory organs (eyes, ears, nose, skin, etc.) to information processing centers (brain and spinal cord). 2. Integration: Interpretation of sensory signals and development of a response. Occurs in brain and spinal cord. 3. Motor Output: Conduction of signals from brain or spinal cord to effector organs (muscles or glands). Controls the activity of muscles and glands, and allows the animal to respond to its environment.

4 Nervous System Allows Us to Respond to Our Environment

5 Cells of Nervous Tissue 1. Neuron: Nerve cell. Structural and functional unit of nervous tissue. xCarry signals from one part of the body to another. 2. Supporting cells: Nourish, protect, and insulate neurons. xThere are roughly 50 supporting cells for every neuron. xIn humans, Schwann cells wrap around the axons of neurons, forming a myelin sheath that is essential for transmission of nerve impulses.

6 Neuron Structure yCell body : Contains nucleus and most organelles. yDendrites: Extensions that convey signals towards the cell body. xShort, numerous, and highly branched yAxon: Extension that transmits signals away from the cell body to another neuron or effector cell. xUsually a long single fiber. xAxon is covered by a myelin sheath made up of many Schwann cells that are separated by small spaces (Nodes of Ranvier).

7 Structure of the Neuron

8 Neuron Structure xMyelin sheath and nodes of Ranvier greatly speed up nerve impulses, which jump down axon from node to node. Speed of signal Myelinated axon100 meters/second Unmyelinated axon 5 meters/second xMultiple sclerosis: A disease in which a person’s immune system destroys the myelin sheaths on their neurons. Loss of muscle control Impaired brain function Death

9 Neurons and Synapses Types of Neurons SensoryMotor Interneurons

10 Spinal Cord Brain Sensory Neuron Sensory Neurons zINPUT From sensory organs to the brain and spinal cord. Drawing shows a somatosensory neuron Vision, hearing, taste and smell nerves are cranial, not spinal

11 Spinal Cord Brain Sensory Neuron Motor Neuron Motor Neurons zOUTPUT From the brain and spinal cord To the muscles and glands.

12 Spinal Cord Brain Sensory Neuron Motor Neuron Interneurons zInterneurons carry information between other neurons only found in the brain and spinal cord.

13 Structures of a neuron

14 The cell body yRound, centrally located structure yContains DNA yControls protein manufacturing yDirects metabolism yNo role in neural signaling zContains the cell’s Nucleus

15 Dendrites zInformation collectors zReceive inputs from neighboring neurons zInputs may number in thousands zIf enough inputs the cell’s AXON may generate an output

16 Dendritic Growth zMature neurons generally can’t divide zBut new dendrites can grow zProvides room for more connections to other neurons zNew connections are basis for learning

17 Axon zThe cell’s output structure zOne axon per cell, 2 distinct parts ytubelike structure branches at end that connect to dendrites of other cells

18 Myelin sheath zWhite fatty casing on axon zActs as an electrical insulator zNot present on all cells zWhen present increases the speed of neural signals down the axon. Myelin Sheath

19 How neurons communicate zNeurons communicate by means of an electrical signal called the Action Potential zAction Potentials are based on movements of ions between the outside and inside of the cell zWhen an Action Potential occurs a molecular message is sent to neighboring neurons

20 Neuron to Neuron zAxons branch out and end near dendrites of neighboring cells zAxon terminals are the tips of the axon’s branches zA gap separates the axon terminals from dendrites zGap is the Synapse Cell Body Dendrite Axon

21 Synapse zaxon terminals contain small storage sacs called synaptic vesicles yvesicles contain neurotransmitter molecules Sending Neuron Synapse Axon Terminal

22 Neurotransmitter Release zAction Potential causes vesicle to open zNeurotransmitter released into synapse zLocks onto receptor molecule in postsynaptic membrane

23 Locks and Keys zNeurotransmitter molecules have specific shapes positive ions (Na+ ) depolarize the neuron negative ions (Cl - ) hyperpolarize zWhen NT binds to receptor, ions enter zReceptor molecules have binding sites

24 Some Drugs work on receptors zSome drugs are shaped like neurotransmitters zAntagonists : fit the receptor but poorly and block the NT ye.g. beta blockers zAgonists : fit receptor well and act like the NT ye.g. nicotine.

25 Summary z3 types of neurons zThe cell membrane zIon movements zAction potentials zSynapse zNeurotransmitters zReceptors and ions zAgonists and antagonists

26 In this experiment you are required to say the color of the word, not what the word says. For example, for the word, RED, you should say "Blue." z Green z Red  Blue