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Nervous System
The Nervous System • Components – Brain, spinal cord, nerves, sensory receptors • Responsible for – Sensory perceptions, mental activities, stimulating muscle movements, secretions of many glands • Subdivisions – Central nervous system (CNS) – Peripheral nervous system (PNS)
DEFINITION DEFINITION  Nervous system is a complex, highly Nervous system is a complex, highly organised network of billions of organised network of billions of neurons $ neuroglia. It consist of neurons $ neuroglia. It consist of brain ,spinal cord, peripheral nerves. brain ,spinal cord, peripheral nerves.
FUNCTIONS OF NERVOUS FUNCTIONS OF NERVOUS SYSTEM SYSTEM  SENSORY FX-sensory receptors detect SENSORY FX-sensory receptors detect internal $ external stimuli.eg rain drop internal $ external stimuli.eg rain drop landing on your hands. landing on your hands.  Neurons carry sensory information from Neurons carry sensory information from cranial $ spinal nerve into the brain $ cranial $ spinal nerve into the brain $ spinal cord or from lower to the higher spinal cord or from lower to the higher level in the spinal cord. Also called level in the spinal cord. Also called afferent neurons. afferent neurons.
FUNCTION-Continue FUNCTION-Continue  INTEGRATIVE FX- NS integrate INTEGRATIVE FX- NS integrate sensory information by analyzing $ sensory information by analyzing $ storing$ making decision for storing$ making decision for appropriate respons .these are called appropriate respons .these are called interneurons because they interneurons because they participates in integration. participates in integration.
FUNCTION-Continue FUNCTION-Continue  MOTOR FX- The NS motor fx involves MOTOR FX- The NS motor fx involves responding to integration decision, responding to integration decision, the neurons serves this fx are called the neurons serves this fx are called motor,(efferent neurons). Because it motor,(efferent neurons). Because it carry information from brain toward carry information from brain toward the spinal cord or out of the brain. the spinal cord or out of the brain.
11-7 Functions of the Functions of the Nervous System Nervous System  Sensory input: Monitor internal and external Sensory input: Monitor internal and external stimuli (change) stimuli (change) – Touch, odor, sound, vision, taste, bp, body temp. Touch, odor, sound, vision, taste, bp, body temp.  Integration. Brain and spinal cord process Integration. Brain and spinal cord process sensory input and initiate responses sensory input and initiate responses  Motor output: Controls of muscles and glands Motor output: Controls of muscles and glands  Homeostasis. Regulate and coordinate Homeostasis. Regulate and coordinate physiology physiology  Mental activity. Consciousness, thinking, Mental activity. Consciousness, thinking, memory, emotion memory, emotion
8 Nervous System Central Nervous System (CNS) Peripheral Nervous System (PNS) Autonomic Nervous System (ANS) (involuntary) Somatic nervous System (voluntary) Sympathetic Nervous System Parasympathetic Nervous System Enteric NS
NEURONS NEURONS  the nervous system consist of a vast the nervous system consist of a vast number of cells called neurons which are number of cells called neurons which are supported by special type of connective supported by special type of connective tissue called neuroglia. tissue called neuroglia.  Single cell unit of the Single cell unit of the nervous nervous system system – 10 billion in the brain alone 10 billion in the brain alone – Receives, processes and transmits Receives, processes and transmits information information  Each neuron in the brain received signals Each neuron in the brain received signals from thousands of other neurons. from thousands of other neurons.
Neurons Neurons  Three main parts: Three main parts: – Dendrites Dendrites – Receive messages Receive messages from other neurons from other neurons – Cell body Cell body – Contains the genetic Contains the genetic information determining information determining cell function cell function – Axon Axon – Conducts electrical Conducts electrical impulses impulses
CONTINUE ----- CONTINUE ----- Presynaptic Terminals Presynaptic Terminals  Each region is specialized for its particular Each region is specialized for its particular function function  Information flows in a single direction Information flows in a single direction
Neuron Neuron  Neuron is Neuron is composed of composed of dendrites, cell dendrites, cell body, and body, and axon. axon.  Synapse Synapse  Supporting Supporting Cells--neuroglia Cells--neuroglia 12
STUCTURE STUCTURE – Soma – Cell body Soma – Cell body – Dendrites – Branches that receive Dendrites – Branches that receive messages from other neurons messages from other neurons – Axon – Trunk of neuron that sends Axon – Trunk of neuron that sends messages to other neurons messages to other neurons – Myelin Sheath – Fatty layer protects and Myelin Sheath – Fatty layer protects and speeds conduction speeds conduction – Axon terminals – Buds at end of axon from Axon terminals – Buds at end of axon from which chemical messages are sent which chemical messages are sent
Neuron - Structure Neuron - Structure
Neuron Anatomy Neuron Anatomy  Extensions outside the cell body  Dendrites – conduct impulses toward the cell body  Axons – conduct impulses away from the cell body (only 1!)
Dendrites of Motor Neurons • Short, tapering, and diffusely branched processes • They are the receptive, or input, regions of the neuron .they receive $ convey incoming impulses toward the cell bodies. • Electrical signals are conveyed as graded potentials (not action potentials)
Axons: Structure • An axon- axis is the long thin , cylindrical projection that often join the cell body at the cone shaped elevation are called axon hillock ,found in deep brain $ in groups. • Some are myelinated and some are nonmyelinated. • The membrane of axon are called axolemma.
• Usually there is only one unbranched axon per neuron • Large axon $ peripheral nerve are surronded by a myelin sheath .this consist of series of schwann cell arrange along the length of axon. • Outer layer of schwann cell is plasma mem brane .Sometimes called neurilemma. • Between plasma membrane there is small amount of fatty substance called myelin. • The tiny area of exposed axolemma between adjacent schwann cell called nodes of ranvier which help in the rapid transmissin of nerve impulse in myelinated neuron.
Axons: Function • Generate and transmit action potentials • Secrete neurotransmitters from the axonal terminals
Myelin Sheath Whitish, fatty (protein-lipid), segmented sheath around most long axons It functions in: –Myelin protects and insulates axons from one another.Protection of the axon –Electrically insulating fibers from one another –Increasing the speed of
– Electrically insulating fibers from one another – Increasing the speed of nerve impulse transmission It functions in: Myelin sheath……….
Myelin Sheath and Neurilemma: Formation • Formed by Schwann cells in the PNS • A Schwann cell: – Envelopes an axon in a trough – Encloses the axon with its plasma membrane – Concentric layers of membrane make up the myelin sheath • Neurilemma – remaining nucleus and cytoplasm of a Schwann cell
Myelin Sheath and Neurilemma: Formation Figure 11.5a-d
Nodes of Ranvier • Gaps in the myelin sheath between adjacent Schwann cells • They are the sites where collaterals can emerge • Saltatory conduction
Unmyelinated Axons • Some are non myelinated nerve fibre in CNS. • schwann cell plasma membrane surrounds nerve fibers but coiling does not take place • Schwann cells partially enclose 15 or more axons
The Synapse The Synapse  The point at which the The point at which the nerve impulse passes nerve impulse passes from 1 neuron to from 1 neuron to another. another. Junction Junction between two cells. between two cells.  Electrical and chemical. Electrical and chemical.  Synaptic vesicles Synaptic vesicles containing a chemical containing a chemical called called neurotransmitters. neurotransmitters.
11-29 The Synapse The Synapse  Site where action Site where action potentials in one potentials in one cell cause action cell cause action potentials in potentials in another cell another cell  Types Types – Presynaptic Presynaptic – Postsynaptic Postsynaptic
11-30 Chemical Synapses Chemical Synapses  Components Components – Presynaptic terminal Presynaptic terminal – Synaptic cleft Synaptic cleft – Postsynaptic membrane Postsynaptic membrane  Neurotransmitters Neurotransmitters released by action released by action potentials in potentials in presynaptic presynaptic terminal terminal – Synaptic vesicles Synaptic vesicles – Diffusion Diffusion – Postsynaptic membrane Postsynaptic membrane  Neurotransmitter Neurotransmitter removal removal
11-31 Types of Chemical Synapses Types of Chemical Synapses  Axodendritic Axodendritic – Between axon terminals of presynaptic neuron Between axon terminals of presynaptic neuron and dendrite of postsynaptic neuron and dendrite of postsynaptic neuron – Most common type of synapse Most common type of synapse  Axosomatic Axosomatic – Between axon of pre- and soma (cell body) of Between axon of pre- and soma (cell body) of post-synaptic neuron post-synaptic neuron  Axoaxonic Axoaxonic – Between two axons Between two axons – Not common Not common
11-32 Neurotransmitter Removal Neurotransmitter Removal
Synapses Neurotransmitter being released into synapse and attaching to receptors on dendrite Based on Harvard Medical School Family Health Guide
Neurotransmitters Neurotransmitters • Definition—chemical compounds released Definition—chemical compounds released from axon terminals (of a presynaptic from axon terminals (of a presynaptic neuron) into a synaptic cleft neuron) into a synaptic cleft • Neurotransmitters bind to specific Neurotransmitters bind to specific receptor molecules in the membrane of a receptor molecules in the membrane of a postsynaptic neuron, opening ion postsynaptic neuron, opening ion channels and thereby stimulating impulse channels and thereby stimulating impulse conduction by the membrane conduction by the membrane 
Neurotransmitters Neurotransmitters • Catecholamine Neurotransmitters Catecholamine Neurotransmitters – Derived from amino acid tyrosine Derived from amino acid tyrosine • Dopamine [Parkinson’s], norepinephrine, epinephrine Dopamine [Parkinson’s], norepinephrine, epinephrine • Amine Neurotransmitters Amine Neurotransmitters – acetylcholine, histamine, serotonin acetylcholine, histamine, serotonin • Amino Acids Amino Acids – aspartic acid, GABA, glutamic acid, glycine aspartic acid, GABA, glutamic acid, glycine • Polypeptides Polypeptides – Include many which also function as hormones Include many which also function as hormones – endorphins endorphins
Nerve Conduction: Specialized Nerve Conduction: Specialized Transmitter Systems Transmitter Systems  Acetylcholine (ACh) Acetylcholine (ACh) – Involved in memory Involved in memory and muscle activity and muscle activity  Dopamine Dopamine – An excitatory An excitatory transmitter transmitter  Serotonin Serotonin – Enhances mood, Enhances mood, eating, sleep, and eating, sleep, and sexual behavior sexual behavior  Endorphins Endorphins – Reduce pain and Reduce pain and increase feeling of increase feeling of well-being well-being
Structural Classification of Neurons Structural Classification of Neurons Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Multipolar neurons – many extensions(dendrites) from the cell body $ 1 axon mostly found in brain $ spinal cord Figure 7.8a
Structural Classification of Neurons Structural Classification of Neurons Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Bipolar neurons – one axon and one dendrite . They are fond in retina of eye , inner ear ,in the olfactory area of brain. Figure 7.8b
Structural Classification of Neurons Structural Classification of Neurons Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Unipolar neurons – have a short single process leaving the cell body. It carry impulses from receptors. Figure 7.8c
Neurons Neurons 3 main types of nerve cells 3 main types of nerve cells sensory neurone relay neurone motor neurone
Functional Classification of Functional Classification of Neurons Neurons Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sensory (afferent) neurons (afferent neurons) carry impulses to central nervous system (CNS) .Carry input messages from the sense organs to the spinal cord and brain  Carry impulses from the sensory receptors  Cutaneous sense organs  Proprioceptors – detect stretch or tension.
Sensory (afferent) neurons
 Motor (efferent) neurons-  Transmit impulses from the brain and spinal cord to the muscles and organs  Carry impulses from the central nervous system (efferent neurons) or carry impulses from CNS to effectors (muscles and glands). Functional Classification of Neurons Functional Classification of Neurons
Functional Classification of Functional Classification of Neurons Neurons Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Interneurons (association neurons) – It carry impulses from sensory to motor neurons (association neurons) . It provide more complex reflexes and associative functions (learning and memory). Perform connective or associative functions in the nervous system  Found in neural pathways in the central nervous system  Connect sensory and motor neurons
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Glial Cells Glial Cells  Neurons of CNS are supported by 4 type Neurons of CNS are supported by 4 type of non excitable glial cell . of non excitable glial cell .  These are continue to replicate These are continue to replicate throughout life also known as neuroglia. throughout life also known as neuroglia.  Surround neurons and hold them in place Surround neurons and hold them in place  Manufacture nutrient chemicals neurons Manufacture nutrient chemicals neurons need need  Absorb toxins and waste materials Absorb toxins and waste materials Nervous Tissue: Support Cells (Neuroglia or Nervous Tissue: Support Cells (Neuroglia or Glia) Glia)
Nervous Tissue: Support Cells Nervous Tissue: Support Cells (Neuroglia or Glia) (Neuroglia or Glia) Slide 7.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Astrocytes  These are main supporting tissues of CNS  Abundant, star-shaped cells  Brace neurons  Form barrier between capillaries and neurons  Control the chemical environment of Figure 7.3a
11-48 Neuroglia of CNS: Astrocytes Neuroglia of CNS: Astrocytes  Largest and most numerous Largest and most numerous  Functions include: Functions include: 1. Form the 1. Form the blood-brain barrier blood-brain barrier – Take up and release ions (Na, Take up and release ions (Na, K) to control the environment K) to control the environment around neurons around neurons – Regulate what substances Regulate what substances reach the CNS from the blood reach the CNS from the blood 2. Reapture and recycle 2. Reapture and recycle neurotrans-mitters neurotrans-mitters 3. Involved with synapse formation 3. Involved with synapse formation in developing neural tissue in developing neural tissue 4. Aid in repair of damaged neural 4. Aid in repair of damaged neural tissue tissue 5. Produce molecules necessary for 5. Produce molecules necessary for neural growth (BDTF) neural growth (BDTF)
Nervous Tissue: Support Cells Nervous Tissue: Support Cells Slide 7.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Microglia (CNS)  These cells derieved from monocytes.they found mainly in in area of blood vessel.  Spider-like phagocytes  Dispose of debris Figure 7.3b, c
 These cells forms the epithilial lining of the ventricles of the brain, $ central canal of the spinal cord  Line cavities of the brain and spinal cord  Circulate cerebrospinal fluid  Ependymal cells (CNS)
11-51 Neuroglia of CNS: Ependymal Cells Neuroglia of CNS: Ependymal Cells  Line brain ventricles Line brain ventricles and spinal cord and spinal cord central canal. central canal. – Specialized versions of Specialized versions of ependymal form ependymal form choroid plexuses choroid plexuses. .  Choroid plexus Choroid plexus – Secrete cerebrospinal Secrete cerebrospinal fluid. Cilia help move fluid. Cilia help move fluid thru the cavities fluid thru the cavities of the brain. of the brain.
Nervous Tissue: Support Cells Nervous Tissue: Support Cells Slide 7.7a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Oligodendrocytes(CNS)- these are smaller than astrocytes.Produce myelin sheath around nerve fibers in the central nervous system.  Having same function as schwann cell in peripheral nerves Figure 7.3d
Support Cells of the PNS Support Cells of the PNS Slide 7.7b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Satellite cells  Protect neuron cell bodies  Schwann cells  Form myelin sheath in the peripheral nervous system Figure 7.3e
11-54 Neuroglia of PNS Neuroglia of PNS  Schwann cells Schwann cells or or neurolemmocytes neurolemmocytes: : – Wrap around portion of only one axon to form myelin Wrap around portion of only one axon to form myelin sheath. sheath. – Wrap around many times. Wrap around many times. – As cells grow around axon, cytoplasm is squeezed out and As cells grow around axon, cytoplasm is squeezed out and multiple layers of cell membrane wrap the axon. Cell multiple layers of cell membrane wrap the axon. Cell membrane primarily phospholipid. membrane primarily phospholipid. – Outer surface of Schwann cell called the neurilemma Outer surface of Schwann cell called the neurilemma  Satellite cells Satellite cells: surround neuron cell bodies in : surround neuron cell bodies in ganglia ganglia, provide support and nutrients , provide support and nutrients
Nerves (F 7-4) • Nerve—bundle of peripheral axons  Tract of central axons  White matter—tissue composed primarily of myelinated axons (nerves or tracts)  Gray matter—tissue composed primarily of cell bodies and unmyelinated fibers
Nerves • Nerve coverings—fibrous connective tissue  Endoneurium—surrounds individual fibers within a nerve  Perineurium—surrounds a group (fascicle) of nerve fibers  Epineurium—surrounds the entire nerve
Nerve Impulses (F 7-6) • Definition—self-propagating wave of electrical disturbances that travel along the surface of a neuron membrane (Cont’d…)
Nerve Impulses • Mechanism  A stimulus triggers the opening of Na+ channels in the plasma membrane of the neuron  Inward movement of positive sodium ions leaves a slight excess of negative ions outside at a stimulated point; marks beginning of a nerve impulse
Neuron Function Neuron Function  Electrical Activity Electrical Activity – Used to transmit signal within neuron Used to transmit signal within neuron  Chemical Activity Chemical Activity – Used to transmit signal between neurons Used to transmit signal between neurons – Synapse – small gap that physically Synapse – small gap that physically separates neurons separates neurons  Neurotransmitters – special “chemicals” that Neurotransmitters – special “chemicals” that neurons use to transmit message across the neurons use to transmit message across the synapse synapse
Neuron Function Neuron Function  Electrical Activity Electrical Activity – Resting Potential Resting Potential  Inside negative (-70 mV) compared to outside Inside negative (-70 mV) compared to outside  Inside has high K Inside has high K+ + (negativity comes from (negativity comes from proteins & other negative ions) proteins & other negative ions)  Outside has high Na Outside has high Na+ +  Forces at work Forces at work – Electrical Electrical – Diffusion Diffusion
Neuron Function Neuron Function  Electrical Activity Electrical Activity – Graded Potential Graded Potential  Depolarization – Inside less negative (e.g., Na Depolarization – Inside less negative (e.g., Na+ + enters) enters)  Hyperpolarization – Inside more negative (e.g., Cl Hyperpolarization – Inside more negative (e.g., Cl- - enters) enters) – Action Potential Action Potential  When graded reaches approximately -55mV When graded reaches approximately -55mV  Electrical impulse that travels down cell – axon to Electrical impulse that travels down cell – axon to axon terminals axon terminals  Axon terminals release neurotransmitter Axon terminals release neurotransmitter
Neuron Function Neuron Function  Electrical Activity Electrical Activity – Restoring Resting Potential Restoring Resting Potential  Sodium-Potassium Pump – moves Na Sodium-Potassium Pump – moves Na+ + out of out of cell and K cell and K+ + into cell into cell  This requires cell to use energy This requires cell to use energy
Neuron Function Neuron Function  Chemical (Neurotransmitter) Activity Chemical (Neurotransmitter) Activity – Leads to graded potentials in neuron Leads to graded potentials in neuron  Excitatory NTs – causes depolarization in Excitatory NTs – causes depolarization in neuron neuron  Initiatory NTs – causes hyperpolarization in Initiatory NTs – causes hyperpolarization in neuron neuron
Neuron – Excitation & Neuron – Excitation & Inhibition Inhibition
Neuron Function Neuron Function A. A. Resting Membrane Resting Membrane Potential Potential - -Potential Difference: Potential Difference: difference in charge difference in charge across a membrane; across a membrane; (Volts) (Volts)
Resting Membrane Resting Membrane Potential Potential  Inside of nerve Inside of nerve cells = negative cells = negative  Outside = positive Outside = positive  -70 millivolts -70 millivolts
B. How resting potential is B. How resting potential is established established & maintained. & maintained. - - Ion Channels: Ion Channels: Regulate flow of Regulate flow of ions into & out of ions into & out of cells. cells.
established & maintained. established & maintained. (cont.) (cont.) - S Sodium/Potassium Pump: odium/Potassium Pump: - At rest = 10x’s more Na+ ions At rest = 10x’s more Na+ ions outside neuron than inside; outside neuron than inside; maintained by Na+/K+ pump maintained by Na+/K+ pump - Pumps 3 Na+ out for every 2 K+ Pumps 3 Na+ out for every 2 K+ brought in; result = more + ions on brought in; result = more + ions on outside than inside outside than inside
Na+/K+ Pump Na+/K+ Pump
B. How resting potential is B. How resting potential is established & maintained (cont.) established & maintained (cont.) - - Other Factors Other Factors: : - More Chloride ions (Cl-) inside cell More Chloride ions (Cl-) inside cell - Large - charged proteins inside (too - Large - charged proteins inside (too large to pass through cell membrane) large to pass through cell membrane)
C. Action Potential (nerve C. Action Potential (nerve impulse) impulse) - Action Potential Action Potential = depolarization + = depolarization + repolarization repolarization - - Depolarization: Depolarization: Inside becomes Inside becomes positive & outside becomes negative positive & outside becomes negative (reversal of charges from resting (reversal of charges from resting potential) potential) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + + + + + + + + + + + +
C. Action Potential (cont.) C. Action Potential (cont.) - Depolarization: Depolarization: occurs when stimulus occurs when stimulus reaches neuron membrane reaches neuron membrane - Na+ ion channels open & Na+ rushes Na+ ion channels open & Na+ rushes into the cell into the cell - Result = more + on inside Result = more + on inside
C. Action Potential (cont.) C. Action Potential (cont.) - - Repolarization: Repolarization: resting potential is resting potential is restored restored - K+ channels open & K+ flows out at K+ channels open & K+ flows out at the same time that Na+ channels close the same time that Na+ channels close - Result = net movement of + ions out & Result = net movement of + ions out & reestablishment of + charge outside reestablishment of + charge outside cell & - charge inside cell & - charge inside
D. Conduction of a Nerve D. Conduction of a Nerve Impulse Impulse 1) 1) Stimulus to localized region Stimulus to localized region 2) 2) Depolarization Depolarization 3) 3) Stimulates depolarization in Stimulates depolarization in adjacent region of membrane adjacent region of membrane 4) 4) Action potential moves along Action potential moves along surface of neuron membrane surface of neuron membrane
D. Conduction of Nerve Impulse D. Conduction of Nerve Impulse (cont.) (cont.) Also: Also: - Myelin sheaths block continuous flow Myelin sheaths block continuous flow of ions of ions - - In myelinated nerve, a.p. jumps from In myelinated nerve, a.p. jumps from one Node of Ranvier to another = one Node of Ranvier to another = Saltatory Conduction Saltatory Conduction. . - - Myelinated fibers = fastest conductors Myelinated fibers = fastest conductors in the body (130m/sec) compared to in the body (130m/sec) compared to unmyelinated fiber (10m/sec) unmyelinated fiber (10m/sec)
E. All-Or-None Response E. All-Or-None Response - - Action Potential always conducts entire Action Potential always conducts entire axon at max. strength axon at max. strength - - Threshold stimulus Threshold stimulus = minimum stimulus = minimum stimulus required to initiate action potential required to initiate action potential - - Subthreshold Subthreshold = cannot initiate an impulse = cannot initiate an impulse - - Summation Summation = series of subthreshold = series of subthreshold stimuli quickly applied to a neuron can stimuli quickly applied to a neuron can have a cumulative effect and start action have a cumulative effect and start action potential potential
F. Transmission of Impulses From Cell to F. Transmission of Impulses From Cell to Cell Cell - - Impulse crosses Impulse crosses synapse to next neuron synapse to next neuron - - Presynaptic neuron Presynaptic neuron = = neuron sending neuron sending impulse impulse - - Postsynaptic neuron Postsynaptic neuron = = neuron receiving neuron receiving impulse impulse - - Synaptic end bulb Synaptic end bulb = has = has synaptic vesicles filled synaptic vesicles filled with neurotransmitters with neurotransmitters
F. Transmission of Nerve Impulses F. Transmission of Nerve Impulses (cont.) (cont.) 1) Nerve impulse 1) Nerve impulse → → Synaptic End Bulb Synaptic End Bulb 2) Ca 2) Ca2+ 2+ channels open; Ca channels open; Ca2+ 2+ flows into the cell flows into the cell 3) Ca 3) Ca2+ 2+ causes fusion of synaptic vesicles with causes fusion of synaptic vesicles with the presynaptic membrane the presynaptic membrane 4) Neurotransmitters released into synapse, 4) Neurotransmitters released into synapse, contact membrane of postsynaptic neuron contact membrane of postsynaptic neuron
G. Excitatory vs. Inhibitory G. Excitatory vs. Inhibitory Transmissions Transmissions - - Excitatory Transmission: Excitatory Transmission: increases increases neuron’s permeability to Na+, causes neuron’s permeability to Na+, causes action potential action potential - - Example neurotransmitters: Example neurotransmitters: acetylcholine, norepinephrine acetylcholine, norepinephrine
G. Excitatory vs. Inhibitory Transmission G. Excitatory vs. Inhibitory Transmission (cont.) (cont.) - Inhibitory Transmission: Inhibitory Transmission: increases increases postsynaptic membrane’s permeability to postsynaptic membrane’s permeability to K+ (K+ leaks out, makes inside more -) K+ (K+ leaks out, makes inside more -) - Cl- also moves into cell Cl- also moves into cell - Results in Results in Hyperpolarization Hyperpolarization = outside = outside more + and inside more - compared to more + and inside more - compared to rest rest - - Example inhibitory neurotransmitters = Example inhibitory neurotransmitters = GABA, endorphins, enkephanlins GABA, endorphins, enkephanlins
How Neurons Function How Neurons Function (Physiology) (Physiology) Slide 7.17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Irritability – ability to respond to stimuli  Conductivity – ability to transmit an impulse  The plasma membrane at rest is polarized  Fewer positive ions are inside the cell than outside the cell
Starting a Nerve Impulse Starting a Nerve Impulse Slide 7.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Depolarization – a stimulus depolarizes the neuron’s membrane  A deploarized membrane allows sodium (Na+ ) to flow inside the membrane  The exchange of ions initiates an action potential in the neuron Figure 7.9a–c
The Action Potential The Action Potential Slide 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  If the action potential (nerve impulse) starts, it is propagated over the entire axon  Potassium ions rush out of the neuron after sodium ions rush in, which repolarizes the membrane  The sodium-potassium pump restores the original configuration  This action requires ATP
Nerve Impulse Propagation Nerve Impulse Propagation Slide 7.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The impulse continues to move toward the cell body  Impulses travel faster when fibers have a myelin sheath Figure 7.9c–e
Continuation of the Nerve Impulse Continuation of the Nerve Impulse between Neurons between Neurons Slide 7.21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Impulses are able to cross the synapse to another nerve  Neurotransmitter is released from a nerve’s axon terminal  The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter  An action potential is started in the dendrite
The Reflex Arc The Reflex Arc Slide 7.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Reflex – rapid, predictable, and involuntary responses to stimuli  Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector Figure 7.11a
Reflex Arcs • Nerve impulses are conducted from receptors to effectors over neuron pathways or reflex arcs; conduction by a reflex arc results in a reflex (that is, contraction by a muscle or secretion by a gland)
Reflex Arcs • Simplest reflex arcs are two-neuron arcs— consist of sensory neurons synapsing in the spinal cord with motor neurons; three-neuron arcs consist of sensory neurons synapsing in the spinal cord with interneurons that synapse with motor neurons
11-91 Five Essential Components Five Essential Components to the Reflex Arc to the Reflex Arc  Receptor – site where Receptor – site where stimulus acts stimulus acts  Sensory neuron – transmits Sensory neuron – transmits afferent impulses to the CNS afferent impulses to the CNS  Integration center – consists Integration center – consists of one or more synapses in of one or more synapses in the CNS the CNS  Motor neuron – conducts Motor neuron – conducts efferent impulses from efferent impulses from integration center to an integration center to an effector effector  Effector – muscle or gland Effector – muscle or gland – Responds to efferent Responds to efferent impulses impulses  Contracting or Contracting or secreting secreting
Types of Reflexes and Regulation Types of Reflexes and Regulation Slide 7.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Autonomic reflexes Smooth muscle regulation Heart and blood pressure regulation Regulation of glands Digestive system regulation  Somatic reflexes Activation of skeletal muscles
11-93 Types of Reflexes Types of Reflexes  Monosynaptic reflex – simplest of all reflexes Monosynaptic reflex – simplest of all reflexes – Just one synapse Just one synapse – The fastest of all reflexes The fastest of all reflexes – Example – knee-jerk reflex Example – knee-jerk reflex  Polysynaptic reflex – more common type of Polysynaptic reflex – more common type of reflex reflex – Most have a single interneuron between the Most have a single interneuron between the sensory and motor neuron sensory and motor neuron – Example – withdrawal reflexes Example – withdrawal reflexes
11-94 Types of Reflexes Types of Reflexes
The Nervous System The Nervous System  Central Nervous System Central Nervous System – Brain and Spinal Cord Brain and Spinal Cord  Peripheral Nervous System Peripheral Nervous System – Connects the CNS with the muscles, Connects the CNS with the muscles, glands, and sensory receptors glands, and sensory receptors
The Peripheral Nervous The Peripheral Nervous System System  Subdivided into: Subdivided into: – Somatic nervous system Somatic nervous system: Consists of sensory and : Consists of sensory and motor neurons that bind together to create nerves motor neurons that bind together to create nerves to transmit messages to sensory receptors to transmit messages to sensory receptors – Autonomic nervous system Autonomic nervous system: Controls glands and : Controls glands and smooth muscles in bodily organs smooth muscles in bodily organs  Sympathetic nervous system: arouses the body Sympathetic nervous system: arouses the body  Parasympathetic nervous system: slows down body Parasympathetic nervous system: slows down body processes processes
Evolution of the Brain Evolution of the Brain
Brain Structures: Brain Structures: The Hindbrain The Hindbrain  Structures: Structures: – Pons Pons: Carries nerve : Carries nerve impulses from higher to impulses from higher to lower parts of nervous lower parts of nervous system system – Cerebellum Cerebellum: Concerned : Concerned with muscular movement, with muscular movement, learning/memory learning/memory – Medulla Medulla: Plays role in : Plays role in vital body functions such vital body functions such as heart rate and as heart rate and breathing breathing
Brain Structures: Brain Structures: The Midbrain The Midbrain  Reticular Formation Reticular Formation – Involved in brain arousal, sleep, and Involved in brain arousal, sleep, and attention attention  Ascending: Sends information to and alerts Ascending: Sends information to and alerts higher brain regions higher brain regions  Descending: Higher brain centers can admit or Descending: Higher brain centers can admit or block sensory input block sensory input
Brain Structures: Brain Structures: Thalamus and Hypothalamus Thalamus and Hypothalamus  Thalamus Thalamus: Routes sensory : Routes sensory information to higher brain information to higher brain structures structures  Hypothalamus Hypothalamus: : – Major role in motivation Major role in motivation and emotions and emotions – Connects with the Connects with the endocrine system endocrine system – Involved in pain/pleasure Involved in pain/pleasure
Brain Structures: Brain Structures: The Limbic System The Limbic System  Helps to coordinate Helps to coordinate behaviors needed to behaviors needed to satisfy motivational satisfy motivational and emotional urges and emotional urges arising in the arising in the hypothalamus hypothalamus  Also involved in Also involved in memory memory
Brain Structures: The Lobes Brain Structures: The Lobes
 Motor cortex Motor cortex – Controls voluntary muscular movements Controls voluntary muscular movements  Association cortex Association cortex – Involved in perception, language, Involved in perception, language, and thought and thought Brain Structures: Regions of Cortex Brain Structures: Regions of Cortex
Brain Structures: Brain Structures: Regions of Cortex Regions of Cortex  Sensory cortex: Receives input from Sensory cortex: Receives input from sensory receptors sensory receptors – Somatic sensory cortex: Receives sensory Somatic sensory cortex: Receives sensory input for heat, touch, cold, balance and input for heat, touch, cold, balance and body movement. body movement.
Motor and Sensory Cortex Motor and Sensory Cortex
Brain Structures: Speech Brain Structures: Speech  Wernicke’s Area Wernicke’s Area – Involved in speech Involved in speech comprehension comprehension  Broca’s Area Broca’s Area – Involved in Involved in production of speech production of speech
Brain Structures: Brain Structures: The Frontal Lobes The Frontal Lobes  Involved in mental Involved in mental abilities such as abilities such as goal setting, goal setting, judgment, planning, judgment, planning, and impulse control and impulse control  Involved in Involved in emotional emotional experience experience

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NERVOUS SYSTEM.ppttttttttttttttttttttttttt

  • 1.
  • 2.
    The Nervous System •Components – Brain, spinal cord, nerves, sensory receptors • Responsible for – Sensory perceptions, mental activities, stimulating muscle movements, secretions of many glands • Subdivisions – Central nervous system (CNS) – Peripheral nervous system (PNS)
  • 3.
    DEFINITION DEFINITION  Nervous systemis a complex, highly Nervous system is a complex, highly organised network of billions of organised network of billions of neurons $ neuroglia. It consist of neurons $ neuroglia. It consist of brain ,spinal cord, peripheral nerves. brain ,spinal cord, peripheral nerves.
  • 4.
    FUNCTIONS OF NERVOUS FUNCTIONSOF NERVOUS SYSTEM SYSTEM  SENSORY FX-sensory receptors detect SENSORY FX-sensory receptors detect internal $ external stimuli.eg rain drop internal $ external stimuli.eg rain drop landing on your hands. landing on your hands.  Neurons carry sensory information from Neurons carry sensory information from cranial $ spinal nerve into the brain $ cranial $ spinal nerve into the brain $ spinal cord or from lower to the higher spinal cord or from lower to the higher level in the spinal cord. Also called level in the spinal cord. Also called afferent neurons. afferent neurons.
  • 5.
    FUNCTION-Continue FUNCTION-Continue  INTEGRATIVE FX-NS integrate INTEGRATIVE FX- NS integrate sensory information by analyzing $ sensory information by analyzing $ storing$ making decision for storing$ making decision for appropriate respons .these are called appropriate respons .these are called interneurons because they interneurons because they participates in integration. participates in integration.
  • 6.
    FUNCTION-Continue FUNCTION-Continue  MOTOR FX-The NS motor fx involves MOTOR FX- The NS motor fx involves responding to integration decision, responding to integration decision, the neurons serves this fx are called the neurons serves this fx are called motor,(efferent neurons). Because it motor,(efferent neurons). Because it carry information from brain toward carry information from brain toward the spinal cord or out of the brain. the spinal cord or out of the brain.
  • 7.
    11-7 Functions of the Functionsof the Nervous System Nervous System  Sensory input: Monitor internal and external Sensory input: Monitor internal and external stimuli (change) stimuli (change) – Touch, odor, sound, vision, taste, bp, body temp. Touch, odor, sound, vision, taste, bp, body temp.  Integration. Brain and spinal cord process Integration. Brain and spinal cord process sensory input and initiate responses sensory input and initiate responses  Motor output: Controls of muscles and glands Motor output: Controls of muscles and glands  Homeostasis. Regulate and coordinate Homeostasis. Regulate and coordinate physiology physiology  Mental activity. Consciousness, thinking, Mental activity. Consciousness, thinking, memory, emotion memory, emotion
  • 8.
    8 Nervous System Central Nervous System(CNS) Peripheral Nervous System (PNS) Autonomic Nervous System (ANS) (involuntary) Somatic nervous System (voluntary) Sympathetic Nervous System Parasympathetic Nervous System Enteric NS
  • 9.
    NEURONS NEURONS  the nervoussystem consist of a vast the nervous system consist of a vast number of cells called neurons which are number of cells called neurons which are supported by special type of connective supported by special type of connective tissue called neuroglia. tissue called neuroglia.  Single cell unit of the Single cell unit of the nervous nervous system system – 10 billion in the brain alone 10 billion in the brain alone – Receives, processes and transmits Receives, processes and transmits information information  Each neuron in the brain received signals Each neuron in the brain received signals from thousands of other neurons. from thousands of other neurons.
  • 10.
    Neurons Neurons  Three mainparts: Three main parts: – Dendrites Dendrites – Receive messages Receive messages from other neurons from other neurons – Cell body Cell body – Contains the genetic Contains the genetic information determining information determining cell function cell function – Axon Axon – Conducts electrical Conducts electrical impulses impulses
  • 11.
    CONTINUE ----- CONTINUE ----- PresynapticTerminals Presynaptic Terminals  Each region is specialized for its particular Each region is specialized for its particular function function  Information flows in a single direction Information flows in a single direction
  • 12.
    Neuron Neuron  Neuron is Neuronis composed of composed of dendrites, cell dendrites, cell body, and body, and axon. axon.  Synapse Synapse  Supporting Supporting Cells--neuroglia Cells--neuroglia 12
  • 13.
    STUCTURE STUCTURE – Soma –Cell body Soma – Cell body – Dendrites – Branches that receive Dendrites – Branches that receive messages from other neurons messages from other neurons – Axon – Trunk of neuron that sends Axon – Trunk of neuron that sends messages to other neurons messages to other neurons – Myelin Sheath – Fatty layer protects and Myelin Sheath – Fatty layer protects and speeds conduction speeds conduction – Axon terminals – Buds at end of axon from Axon terminals – Buds at end of axon from which chemical messages are sent which chemical messages are sent
  • 14.
  • 15.
    Neuron Anatomy Neuron Anatomy Extensions outside the cell body  Dendrites – conduct impulses toward the cell body  Axons – conduct impulses away from the cell body (only 1!)
  • 16.
    Dendrites of MotorNeurons • Short, tapering, and diffusely branched processes • They are the receptive, or input, regions of the neuron .they receive $ convey incoming impulses toward the cell bodies. • Electrical signals are conveyed as graded potentials (not action potentials)
  • 17.
    Axons: Structure • Anaxon- axis is the long thin , cylindrical projection that often join the cell body at the cone shaped elevation are called axon hillock ,found in deep brain $ in groups. • Some are myelinated and some are nonmyelinated. • The membrane of axon are called axolemma.
  • 18.
    • Usually thereis only one unbranched axon per neuron • Large axon $ peripheral nerve are surronded by a myelin sheath .this consist of series of schwann cell arrange along the length of axon. • Outer layer of schwann cell is plasma mem brane .Sometimes called neurilemma. • Between plasma membrane there is small amount of fatty substance called myelin. • The tiny area of exposed axolemma between adjacent schwann cell called nodes of ranvier which help in the rapid transmissin of nerve impulse in myelinated neuron.
  • 19.
    Axons: Function • Generateand transmit action potentials • Secrete neurotransmitters from the axonal terminals
  • 20.
    Myelin Sheath Whitish, fatty (protein-lipid), segmentedsheath around most long axons It functions in: –Myelin protects and insulates axons from one another.Protection of the axon –Electrically insulating fibers from one another –Increasing the speed of
  • 21.
    – Electrically insulatingfibers from one another – Increasing the speed of nerve impulse transmission It functions in: Myelin sheath……….
  • 22.
    Myelin Sheath andNeurilemma: Formation • Formed by Schwann cells in the PNS • A Schwann cell: – Envelopes an axon in a trough – Encloses the axon with its plasma membrane – Concentric layers of membrane make up the myelin sheath • Neurilemma – remaining nucleus and cytoplasm of a Schwann cell
  • 24.
  • 26.
    Nodes of Ranvier •Gaps in the myelin sheath between adjacent Schwann cells • They are the sites where collaterals can emerge • Saltatory conduction
  • 27.
    Unmyelinated Axons • Someare non myelinated nerve fibre in CNS. • schwann cell plasma membrane surrounds nerve fibers but coiling does not take place • Schwann cells partially enclose 15 or more axons
  • 28.
    The Synapse The Synapse The point at which the The point at which the nerve impulse passes nerve impulse passes from 1 neuron to from 1 neuron to another. another. Junction Junction between two cells. between two cells.  Electrical and chemical. Electrical and chemical.  Synaptic vesicles Synaptic vesicles containing a chemical containing a chemical called called neurotransmitters. neurotransmitters.
  • 29.
    11-29 The Synapse The Synapse Site where action Site where action potentials in one potentials in one cell cause action cell cause action potentials in potentials in another cell another cell  Types Types – Presynaptic Presynaptic – Postsynaptic Postsynaptic
  • 30.
    11-30 Chemical Synapses Chemical Synapses Components Components – Presynaptic terminal Presynaptic terminal – Synaptic cleft Synaptic cleft – Postsynaptic membrane Postsynaptic membrane  Neurotransmitters Neurotransmitters released by action released by action potentials in potentials in presynaptic presynaptic terminal terminal – Synaptic vesicles Synaptic vesicles – Diffusion Diffusion – Postsynaptic membrane Postsynaptic membrane  Neurotransmitter Neurotransmitter removal removal
  • 31.
    11-31 Types of ChemicalSynapses Types of Chemical Synapses  Axodendritic Axodendritic – Between axon terminals of presynaptic neuron Between axon terminals of presynaptic neuron and dendrite of postsynaptic neuron and dendrite of postsynaptic neuron – Most common type of synapse Most common type of synapse  Axosomatic Axosomatic – Between axon of pre- and soma (cell body) of Between axon of pre- and soma (cell body) of post-synaptic neuron post-synaptic neuron  Axoaxonic Axoaxonic – Between two axons Between two axons – Not common Not common
  • 32.
  • 33.
    Synapses Neurotransmitter being releasedinto synapse and attaching to receptors on dendrite Based on Harvard Medical School Family Health Guide
  • 34.
    Neurotransmitters Neurotransmitters • Definition—chemical compoundsreleased Definition—chemical compounds released from axon terminals (of a presynaptic from axon terminals (of a presynaptic neuron) into a synaptic cleft neuron) into a synaptic cleft • Neurotransmitters bind to specific Neurotransmitters bind to specific receptor molecules in the membrane of a receptor molecules in the membrane of a postsynaptic neuron, opening ion postsynaptic neuron, opening ion channels and thereby stimulating impulse channels and thereby stimulating impulse conduction by the membrane conduction by the membrane 
  • 35.
    Neurotransmitters Neurotransmitters • Catecholamine Neurotransmitters CatecholamineNeurotransmitters – Derived from amino acid tyrosine Derived from amino acid tyrosine • Dopamine [Parkinson’s], norepinephrine, epinephrine Dopamine [Parkinson’s], norepinephrine, epinephrine • Amine Neurotransmitters Amine Neurotransmitters – acetylcholine, histamine, serotonin acetylcholine, histamine, serotonin • Amino Acids Amino Acids – aspartic acid, GABA, glutamic acid, glycine aspartic acid, GABA, glutamic acid, glycine • Polypeptides Polypeptides – Include many which also function as hormones Include many which also function as hormones – endorphins endorphins
  • 36.
    Nerve Conduction: Specialized NerveConduction: Specialized Transmitter Systems Transmitter Systems  Acetylcholine (ACh) Acetylcholine (ACh) – Involved in memory Involved in memory and muscle activity and muscle activity  Dopamine Dopamine – An excitatory An excitatory transmitter transmitter  Serotonin Serotonin – Enhances mood, Enhances mood, eating, sleep, and eating, sleep, and sexual behavior sexual behavior  Endorphins Endorphins – Reduce pain and Reduce pain and increase feeling of increase feeling of well-being well-being
  • 37.
    Structural Classification ofNeurons Structural Classification of Neurons Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Multipolar neurons – many extensions(dendrites) from the cell body $ 1 axon mostly found in brain $ spinal cord Figure 7.8a
  • 38.
    Structural Classification ofNeurons Structural Classification of Neurons Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Bipolar neurons – one axon and one dendrite . They are fond in retina of eye , inner ear ,in the olfactory area of brain. Figure 7.8b
  • 39.
    Structural Classification ofNeurons Structural Classification of Neurons Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Unipolar neurons – have a short single process leaving the cell body. It carry impulses from receptors. Figure 7.8c
  • 40.
    Neurons Neurons 3 main typesof nerve cells 3 main types of nerve cells sensory neurone relay neurone motor neurone
  • 41.
    Functional Classification of FunctionalClassification of Neurons Neurons Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sensory (afferent) neurons (afferent neurons) carry impulses to central nervous system (CNS) .Carry input messages from the sense organs to the spinal cord and brain  Carry impulses from the sensory receptors  Cutaneous sense organs  Proprioceptors – detect stretch or tension.
  • 42.
  • 43.
     Motor (efferent)neurons-  Transmit impulses from the brain and spinal cord to the muscles and organs  Carry impulses from the central nervous system (efferent neurons) or carry impulses from CNS to effectors (muscles and glands). Functional Classification of Neurons Functional Classification of Neurons
  • 44.
    Functional Classification of FunctionalClassification of Neurons Neurons Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Interneurons (association neurons) – It carry impulses from sensory to motor neurons (association neurons) . It provide more complex reflexes and associative functions (learning and memory). Perform connective or associative functions in the nervous system  Found in neural pathways in the central nervous system  Connect sensory and motor neurons
  • 45.
  • 46.
    Glial Cells Glial Cells Neurons of CNS are supported by 4 type Neurons of CNS are supported by 4 type of non excitable glial cell . of non excitable glial cell .  These are continue to replicate These are continue to replicate throughout life also known as neuroglia. throughout life also known as neuroglia.  Surround neurons and hold them in place Surround neurons and hold them in place  Manufacture nutrient chemicals neurons Manufacture nutrient chemicals neurons need need  Absorb toxins and waste materials Absorb toxins and waste materials Nervous Tissue: Support Cells (Neuroglia or Nervous Tissue: Support Cells (Neuroglia or Glia) Glia)
  • 47.
    Nervous Tissue: SupportCells Nervous Tissue: Support Cells (Neuroglia or Glia) (Neuroglia or Glia) Slide 7.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Astrocytes  These are main supporting tissues of CNS  Abundant, star-shaped cells  Brace neurons  Form barrier between capillaries and neurons  Control the chemical environment of Figure 7.3a
  • 48.
    11-48 Neuroglia of CNS:Astrocytes Neuroglia of CNS: Astrocytes  Largest and most numerous Largest and most numerous  Functions include: Functions include: 1. Form the 1. Form the blood-brain barrier blood-brain barrier – Take up and release ions (Na, Take up and release ions (Na, K) to control the environment K) to control the environment around neurons around neurons – Regulate what substances Regulate what substances reach the CNS from the blood reach the CNS from the blood 2. Reapture and recycle 2. Reapture and recycle neurotrans-mitters neurotrans-mitters 3. Involved with synapse formation 3. Involved with synapse formation in developing neural tissue in developing neural tissue 4. Aid in repair of damaged neural 4. Aid in repair of damaged neural tissue tissue 5. Produce molecules necessary for 5. Produce molecules necessary for neural growth (BDTF) neural growth (BDTF)
  • 49.
    Nervous Tissue: SupportCells Nervous Tissue: Support Cells Slide 7.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Microglia (CNS)  These cells derieved from monocytes.they found mainly in in area of blood vessel.  Spider-like phagocytes  Dispose of debris Figure 7.3b, c
  • 50.
     These cellsforms the epithilial lining of the ventricles of the brain, $ central canal of the spinal cord  Line cavities of the brain and spinal cord  Circulate cerebrospinal fluid  Ependymal cells (CNS)
  • 51.
    11-51 Neuroglia of CNS:Ependymal Cells Neuroglia of CNS: Ependymal Cells  Line brain ventricles Line brain ventricles and spinal cord and spinal cord central canal. central canal. – Specialized versions of Specialized versions of ependymal form ependymal form choroid plexuses choroid plexuses. .  Choroid plexus Choroid plexus – Secrete cerebrospinal Secrete cerebrospinal fluid. Cilia help move fluid. Cilia help move fluid thru the cavities fluid thru the cavities of the brain. of the brain.
  • 52.
    Nervous Tissue: SupportCells Nervous Tissue: Support Cells Slide 7.7a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Oligodendrocytes(CNS)- these are smaller than astrocytes.Produce myelin sheath around nerve fibers in the central nervous system.  Having same function as schwann cell in peripheral nerves Figure 7.3d
  • 53.
    Support Cells ofthe PNS Support Cells of the PNS Slide 7.7b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Satellite cells  Protect neuron cell bodies  Schwann cells  Form myelin sheath in the peripheral nervous system Figure 7.3e
  • 54.
    11-54 Neuroglia of PNS Neurogliaof PNS  Schwann cells Schwann cells or or neurolemmocytes neurolemmocytes: : – Wrap around portion of only one axon to form myelin Wrap around portion of only one axon to form myelin sheath. sheath. – Wrap around many times. Wrap around many times. – As cells grow around axon, cytoplasm is squeezed out and As cells grow around axon, cytoplasm is squeezed out and multiple layers of cell membrane wrap the axon. Cell multiple layers of cell membrane wrap the axon. Cell membrane primarily phospholipid. membrane primarily phospholipid. – Outer surface of Schwann cell called the neurilemma Outer surface of Schwann cell called the neurilemma  Satellite cells Satellite cells: surround neuron cell bodies in : surround neuron cell bodies in ganglia ganglia, provide support and nutrients , provide support and nutrients
  • 55.
    Nerves (F 7-4) •Nerve—bundle of peripheral axons  Tract of central axons  White matter—tissue composed primarily of myelinated axons (nerves or tracts)  Gray matter—tissue composed primarily of cell bodies and unmyelinated fibers
  • 56.
    Nerves • Nerve coverings—fibrousconnective tissue  Endoneurium—surrounds individual fibers within a nerve  Perineurium—surrounds a group (fascicle) of nerve fibers  Epineurium—surrounds the entire nerve
  • 57.
    Nerve Impulses (F7-6) • Definition—self-propagating wave of electrical disturbances that travel along the surface of a neuron membrane (Cont’d…)
  • 58.
    Nerve Impulses • Mechanism A stimulus triggers the opening of Na+ channels in the plasma membrane of the neuron  Inward movement of positive sodium ions leaves a slight excess of negative ions outside at a stimulated point; marks beginning of a nerve impulse
  • 59.
    Neuron Function Neuron Function Electrical Activity Electrical Activity – Used to transmit signal within neuron Used to transmit signal within neuron  Chemical Activity Chemical Activity – Used to transmit signal between neurons Used to transmit signal between neurons – Synapse – small gap that physically Synapse – small gap that physically separates neurons separates neurons  Neurotransmitters – special “chemicals” that Neurotransmitters – special “chemicals” that neurons use to transmit message across the neurons use to transmit message across the synapse synapse
  • 60.
    Neuron Function Neuron Function Electrical Activity Electrical Activity – Resting Potential Resting Potential  Inside negative (-70 mV) compared to outside Inside negative (-70 mV) compared to outside  Inside has high K Inside has high K+ + (negativity comes from (negativity comes from proteins & other negative ions) proteins & other negative ions)  Outside has high Na Outside has high Na+ +  Forces at work Forces at work – Electrical Electrical – Diffusion Diffusion
  • 61.
    Neuron Function Neuron Function Electrical Activity Electrical Activity – Graded Potential Graded Potential  Depolarization – Inside less negative (e.g., Na Depolarization – Inside less negative (e.g., Na+ + enters) enters)  Hyperpolarization – Inside more negative (e.g., Cl Hyperpolarization – Inside more negative (e.g., Cl- - enters) enters) – Action Potential Action Potential  When graded reaches approximately -55mV When graded reaches approximately -55mV  Electrical impulse that travels down cell – axon to Electrical impulse that travels down cell – axon to axon terminals axon terminals  Axon terminals release neurotransmitter Axon terminals release neurotransmitter
  • 62.
    Neuron Function Neuron Function Electrical Activity Electrical Activity – Restoring Resting Potential Restoring Resting Potential  Sodium-Potassium Pump – moves Na Sodium-Potassium Pump – moves Na+ + out of out of cell and K cell and K+ + into cell into cell  This requires cell to use energy This requires cell to use energy
  • 63.
    Neuron Function Neuron Function Chemical (Neurotransmitter) Activity Chemical (Neurotransmitter) Activity – Leads to graded potentials in neuron Leads to graded potentials in neuron  Excitatory NTs – causes depolarization in Excitatory NTs – causes depolarization in neuron neuron  Initiatory NTs – causes hyperpolarization in Initiatory NTs – causes hyperpolarization in neuron neuron
  • 64.
    Neuron – Excitation& Neuron – Excitation & Inhibition Inhibition
  • 65.
    Neuron Function Neuron Function A. A.Resting Membrane Resting Membrane Potential Potential - -Potential Difference: Potential Difference: difference in charge difference in charge across a membrane; across a membrane; (Volts) (Volts)
  • 66.
    Resting Membrane Resting Membrane Potential Potential Inside of nerve Inside of nerve cells = negative cells = negative  Outside = positive Outside = positive  -70 millivolts -70 millivolts
  • 67.
    B. How restingpotential is B. How resting potential is established established & maintained. & maintained. - - Ion Channels: Ion Channels: Regulate flow of Regulate flow of ions into & out of ions into & out of cells. cells.
  • 68.
    established & maintained. established& maintained. (cont.) (cont.) - S Sodium/Potassium Pump: odium/Potassium Pump: - At rest = 10x’s more Na+ ions At rest = 10x’s more Na+ ions outside neuron than inside; outside neuron than inside; maintained by Na+/K+ pump maintained by Na+/K+ pump - Pumps 3 Na+ out for every 2 K+ Pumps 3 Na+ out for every 2 K+ brought in; result = more + ions on brought in; result = more + ions on outside than inside outside than inside
  • 69.
  • 70.
    B. How restingpotential is B. How resting potential is established & maintained (cont.) established & maintained (cont.) - - Other Factors Other Factors: : - More Chloride ions (Cl-) inside cell More Chloride ions (Cl-) inside cell - Large - charged proteins inside (too - Large - charged proteins inside (too large to pass through cell membrane) large to pass through cell membrane)
  • 71.
    C. Action Potential(nerve C. Action Potential (nerve impulse) impulse) - Action Potential Action Potential = depolarization + = depolarization + repolarization repolarization - - Depolarization: Depolarization: Inside becomes Inside becomes positive & outside becomes negative positive & outside becomes negative (reversal of charges from resting (reversal of charges from resting potential) potential) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + + + + + + + + + + + +
  • 72.
    C. Action Potential(cont.) C. Action Potential (cont.) - Depolarization: Depolarization: occurs when stimulus occurs when stimulus reaches neuron membrane reaches neuron membrane - Na+ ion channels open & Na+ rushes Na+ ion channels open & Na+ rushes into the cell into the cell - Result = more + on inside Result = more + on inside
  • 73.
    C. Action Potential(cont.) C. Action Potential (cont.) - - Repolarization: Repolarization: resting potential is resting potential is restored restored - K+ channels open & K+ flows out at K+ channels open & K+ flows out at the same time that Na+ channels close the same time that Na+ channels close - Result = net movement of + ions out & Result = net movement of + ions out & reestablishment of + charge outside reestablishment of + charge outside cell & - charge inside cell & - charge inside
  • 74.
    D. Conduction ofa Nerve D. Conduction of a Nerve Impulse Impulse 1) 1) Stimulus to localized region Stimulus to localized region 2) 2) Depolarization Depolarization 3) 3) Stimulates depolarization in Stimulates depolarization in adjacent region of membrane adjacent region of membrane 4) 4) Action potential moves along Action potential moves along surface of neuron membrane surface of neuron membrane
  • 76.
    D. Conduction ofNerve Impulse D. Conduction of Nerve Impulse (cont.) (cont.) Also: Also: - Myelin sheaths block continuous flow Myelin sheaths block continuous flow of ions of ions - - In myelinated nerve, a.p. jumps from In myelinated nerve, a.p. jumps from one Node of Ranvier to another = one Node of Ranvier to another = Saltatory Conduction Saltatory Conduction. . - - Myelinated fibers = fastest conductors Myelinated fibers = fastest conductors in the body (130m/sec) compared to in the body (130m/sec) compared to unmyelinated fiber (10m/sec) unmyelinated fiber (10m/sec)
  • 77.
    E. All-Or-None Response E.All-Or-None Response - - Action Potential always conducts entire Action Potential always conducts entire axon at max. strength axon at max. strength - - Threshold stimulus Threshold stimulus = minimum stimulus = minimum stimulus required to initiate action potential required to initiate action potential - - Subthreshold Subthreshold = cannot initiate an impulse = cannot initiate an impulse - - Summation Summation = series of subthreshold = series of subthreshold stimuli quickly applied to a neuron can stimuli quickly applied to a neuron can have a cumulative effect and start action have a cumulative effect and start action potential potential
  • 78.
    F. Transmission ofImpulses From Cell to F. Transmission of Impulses From Cell to Cell Cell - - Impulse crosses Impulse crosses synapse to next neuron synapse to next neuron - - Presynaptic neuron Presynaptic neuron = = neuron sending neuron sending impulse impulse - - Postsynaptic neuron Postsynaptic neuron = = neuron receiving neuron receiving impulse impulse - - Synaptic end bulb Synaptic end bulb = has = has synaptic vesicles filled synaptic vesicles filled with neurotransmitters with neurotransmitters
  • 79.
    F. Transmission ofNerve Impulses F. Transmission of Nerve Impulses (cont.) (cont.) 1) Nerve impulse 1) Nerve impulse → → Synaptic End Bulb Synaptic End Bulb 2) Ca 2) Ca2+ 2+ channels open; Ca channels open; Ca2+ 2+ flows into the cell flows into the cell 3) Ca 3) Ca2+ 2+ causes fusion of synaptic vesicles with causes fusion of synaptic vesicles with the presynaptic membrane the presynaptic membrane 4) Neurotransmitters released into synapse, 4) Neurotransmitters released into synapse, contact membrane of postsynaptic neuron contact membrane of postsynaptic neuron
  • 81.
    G. Excitatory vs.Inhibitory G. Excitatory vs. Inhibitory Transmissions Transmissions - - Excitatory Transmission: Excitatory Transmission: increases increases neuron’s permeability to Na+, causes neuron’s permeability to Na+, causes action potential action potential - - Example neurotransmitters: Example neurotransmitters: acetylcholine, norepinephrine acetylcholine, norepinephrine
  • 82.
    G. Excitatory vs.Inhibitory Transmission G. Excitatory vs. Inhibitory Transmission (cont.) (cont.) - Inhibitory Transmission: Inhibitory Transmission: increases increases postsynaptic membrane’s permeability to postsynaptic membrane’s permeability to K+ (K+ leaks out, makes inside more -) K+ (K+ leaks out, makes inside more -) - Cl- also moves into cell Cl- also moves into cell - Results in Results in Hyperpolarization Hyperpolarization = outside = outside more + and inside more - compared to more + and inside more - compared to rest rest - - Example inhibitory neurotransmitters = Example inhibitory neurotransmitters = GABA, endorphins, enkephanlins GABA, endorphins, enkephanlins
  • 83.
    How Neurons Function HowNeurons Function (Physiology) (Physiology) Slide 7.17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Irritability – ability to respond to stimuli  Conductivity – ability to transmit an impulse  The plasma membrane at rest is polarized  Fewer positive ions are inside the cell than outside the cell
  • 84.
    Starting a NerveImpulse Starting a Nerve Impulse Slide 7.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Depolarization – a stimulus depolarizes the neuron’s membrane  A deploarized membrane allows sodium (Na+ ) to flow inside the membrane  The exchange of ions initiates an action potential in the neuron Figure 7.9a–c
  • 85.
    The Action Potential TheAction Potential Slide 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  If the action potential (nerve impulse) starts, it is propagated over the entire axon  Potassium ions rush out of the neuron after sodium ions rush in, which repolarizes the membrane  The sodium-potassium pump restores the original configuration  This action requires ATP
  • 86.
    Nerve Impulse Propagation NerveImpulse Propagation Slide 7.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The impulse continues to move toward the cell body  Impulses travel faster when fibers have a myelin sheath Figure 7.9c–e
  • 87.
    Continuation of theNerve Impulse Continuation of the Nerve Impulse between Neurons between Neurons Slide 7.21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Impulses are able to cross the synapse to another nerve  Neurotransmitter is released from a nerve’s axon terminal  The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter  An action potential is started in the dendrite
  • 88.
    The Reflex Arc TheReflex Arc Slide 7.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Reflex – rapid, predictable, and involuntary responses to stimuli  Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector Figure 7.11a
  • 89.
    Reflex Arcs • Nerveimpulses are conducted from receptors to effectors over neuron pathways or reflex arcs; conduction by a reflex arc results in a reflex (that is, contraction by a muscle or secretion by a gland)
  • 90.
    Reflex Arcs • Simplestreflex arcs are two-neuron arcs— consist of sensory neurons synapsing in the spinal cord with motor neurons; three-neuron arcs consist of sensory neurons synapsing in the spinal cord with interneurons that synapse with motor neurons
  • 91.
    11-91 Five Essential Components FiveEssential Components to the Reflex Arc to the Reflex Arc  Receptor – site where Receptor – site where stimulus acts stimulus acts  Sensory neuron – transmits Sensory neuron – transmits afferent impulses to the CNS afferent impulses to the CNS  Integration center – consists Integration center – consists of one or more synapses in of one or more synapses in the CNS the CNS  Motor neuron – conducts Motor neuron – conducts efferent impulses from efferent impulses from integration center to an integration center to an effector effector  Effector – muscle or gland Effector – muscle or gland – Responds to efferent Responds to efferent impulses impulses  Contracting or Contracting or secreting secreting
  • 92.
    Types of Reflexesand Regulation Types of Reflexes and Regulation Slide 7.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Autonomic reflexes Smooth muscle regulation Heart and blood pressure regulation Regulation of glands Digestive system regulation  Somatic reflexes Activation of skeletal muscles
  • 93.
    11-93 Types of Reflexes Typesof Reflexes  Monosynaptic reflex – simplest of all reflexes Monosynaptic reflex – simplest of all reflexes – Just one synapse Just one synapse – The fastest of all reflexes The fastest of all reflexes – Example – knee-jerk reflex Example – knee-jerk reflex  Polysynaptic reflex – more common type of Polysynaptic reflex – more common type of reflex reflex – Most have a single interneuron between the Most have a single interneuron between the sensory and motor neuron sensory and motor neuron – Example – withdrawal reflexes Example – withdrawal reflexes
  • 94.
  • 95.
    The Nervous System TheNervous System  Central Nervous System Central Nervous System – Brain and Spinal Cord Brain and Spinal Cord  Peripheral Nervous System Peripheral Nervous System – Connects the CNS with the muscles, Connects the CNS with the muscles, glands, and sensory receptors glands, and sensory receptors
  • 97.
    The Peripheral Nervous ThePeripheral Nervous System System  Subdivided into: Subdivided into: – Somatic nervous system Somatic nervous system: Consists of sensory and : Consists of sensory and motor neurons that bind together to create nerves motor neurons that bind together to create nerves to transmit messages to sensory receptors to transmit messages to sensory receptors – Autonomic nervous system Autonomic nervous system: Controls glands and : Controls glands and smooth muscles in bodily organs smooth muscles in bodily organs  Sympathetic nervous system: arouses the body Sympathetic nervous system: arouses the body  Parasympathetic nervous system: slows down body Parasympathetic nervous system: slows down body processes processes
  • 98.
    Evolution of theBrain Evolution of the Brain
  • 99.
    Brain Structures: Brain Structures: TheHindbrain The Hindbrain  Structures: Structures: – Pons Pons: Carries nerve : Carries nerve impulses from higher to impulses from higher to lower parts of nervous lower parts of nervous system system – Cerebellum Cerebellum: Concerned : Concerned with muscular movement, with muscular movement, learning/memory learning/memory – Medulla Medulla: Plays role in : Plays role in vital body functions such vital body functions such as heart rate and as heart rate and breathing breathing
  • 100.
    Brain Structures: Brain Structures: TheMidbrain The Midbrain  Reticular Formation Reticular Formation – Involved in brain arousal, sleep, and Involved in brain arousal, sleep, and attention attention  Ascending: Sends information to and alerts Ascending: Sends information to and alerts higher brain regions higher brain regions  Descending: Higher brain centers can admit or Descending: Higher brain centers can admit or block sensory input block sensory input
  • 101.
    Brain Structures: Brain Structures: Thalamusand Hypothalamus Thalamus and Hypothalamus  Thalamus Thalamus: Routes sensory : Routes sensory information to higher brain information to higher brain structures structures  Hypothalamus Hypothalamus: : – Major role in motivation Major role in motivation and emotions and emotions – Connects with the Connects with the endocrine system endocrine system – Involved in pain/pleasure Involved in pain/pleasure
  • 102.
    Brain Structures: Brain Structures: TheLimbic System The Limbic System  Helps to coordinate Helps to coordinate behaviors needed to behaviors needed to satisfy motivational satisfy motivational and emotional urges and emotional urges arising in the arising in the hypothalamus hypothalamus  Also involved in Also involved in memory memory
  • 103.
    Brain Structures: TheLobes Brain Structures: The Lobes
  • 104.
     Motor cortex Motorcortex – Controls voluntary muscular movements Controls voluntary muscular movements  Association cortex Association cortex – Involved in perception, language, Involved in perception, language, and thought and thought Brain Structures: Regions of Cortex Brain Structures: Regions of Cortex
  • 105.
    Brain Structures: Brain Structures: Regionsof Cortex Regions of Cortex  Sensory cortex: Receives input from Sensory cortex: Receives input from sensory receptors sensory receptors – Somatic sensory cortex: Receives sensory Somatic sensory cortex: Receives sensory input for heat, touch, cold, balance and input for heat, touch, cold, balance and body movement. body movement.
  • 106.
    Motor and SensoryCortex Motor and Sensory Cortex
  • 107.
    Brain Structures: Speech BrainStructures: Speech  Wernicke’s Area Wernicke’s Area – Involved in speech Involved in speech comprehension comprehension  Broca’s Area Broca’s Area – Involved in Involved in production of speech production of speech
  • 108.
    Brain Structures: Brain Structures: TheFrontal Lobes The Frontal Lobes  Involved in mental Involved in mental abilities such as abilities such as goal setting, goal setting, judgment, planning, judgment, planning, and impulse control and impulse control  Involved in Involved in emotional emotional experience experience

Editor's Notes

  • #33 Main Idea(s) of This Slide - This slide depicts the synapses between the axon of one neuron and the dendrite of another. Here is a close-up view of the synapse between two adjacent neurons. The axon of the neuron at the top of the slide terminates in what is called an axon bulb. Inside the axon bulb are synaptic vesicles that contain neurotransmitters. The neurotransmitters are responsible for exiting the axon bulb and entering into the synapse. Once inside the synapse (space between the neurons), the neurohormones bind to the adjacent neurons “postsynaptic membrane” and cause a new depolarization wave to begin. This image on the right depicts the neurotransmitter (neurohormone) being released from the synaptic vesicle into the synapse where it can then bind to receptors on the adjacent neuron.