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Nervous system. Nervous system. 2 main parts 1) Central Nervous System (CNS) Brain: central processing center Spinal cord: extends down back below brain. Nervous system. 2 main parts 2) Peripheral Nervous System (PNS) Connects CNS to muscles, sensory cells, etc.

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nervous system1
Nervous system
  • 2 main parts
    • 1) Central Nervous System (CNS)
    • Brain: central processing center
    • Spinal cord: extends down back below brain
nervous system2
Nervous system
  • 2 main parts
    • 2) Peripheral Nervous System (PNS)
    • Connects CNS to muscles, sensory cells, etc.
    • 12 pairs of cranial nerves (attached to brain)
    • _________ pairs of spinal nerves (attached to spinal cord)
nervous system3
Nervous system
  • Functions:
    • 1) Monitors changes in external and internal environment
    • Receptors: gather information
nervous system4
Nervous system
  • Functions:
    • 1) Monitors changes in external and internal environment
    • Receptors: gather information
    • 2) Sends messages in response to information gathered
    • Effectors: cells that respond to message (glands, muscles)
nervous system5
Nervous system
  • 3 types of nerve cells (neurons)
    • Sensory neurons (act as receptors)
      • Found in skin, organs. Cell body of neuron outside of CNS. Long dendrites, ____________ axons
nervous system6
Nervous system
  • 3 types of nerve cells (neurons)
    • Motor neurons (carry message to effectors)
      • Cell bodies contained within CNS. Short dendrites, long axons
nervous system7
Nervous system
  • 3 types of nerve cells (neurons)
    • Association neurons (often link sensory and motor neurons)
      • Cell bodies in CNS. Connect motor and sensory neurons. Connect sensory neurons to ____________
the neuron
The neuron
  • Functional unit of nervous system
  • Neuron: dendrite (incoming messages), cell body, axon (outgoing message)
neuroglia
Neuroglia
  • Neuroglia (supporting cells)
  • Schwann cells (PNS) and oligodendrocytes (CNS)
  • Form myelin sheath, Nodes of Ranvier
neuroglia1
Neuroglia
  • Myelinated axons are whitish: called white matter in nerves/spinal cord/brain
  • Unmyelinated axons/dendrites and cell bodies are grayish: called gray matter
neuroglia2
Neuroglia
  • Secrete myelin (80% ___________)
  • Cells wrap axon in a whitish “jelly roll”: myelin sheath
neuroglia3
Neuroglia
  • Functions:
    • 1) support and protect nerve cell from injury
    • 2) nourish nerve cell (lies between blood vessels and neurons)
    • 3) electrical insulator: increases rate of impulse, insulates against firing of other neurons
    • 4) aids in regeneration of sensory nerves after ______________
neuroglia4
Neuroglia
  • Example of importance: Multiple Sclerosis (MS)
  • 2 million people worldwide
  • Body’s immune system attacks myelin sheaths
  • Result: poor nerve impulse conduction. Lose ability to _____________ muscles
  • Cause? Uncertain: genetics, viral infection
how a nerve works
How a nerve works
  • Nerve impulse:
    • electrochemical signal
    • great speed: up to _________ miles per hour
    • resting nerve has charge difference across membrane: membrane “polarized”
    • impulse: wave of depolarization caused by sudden influx of Na+ into axon
    • followed by repolarization: return to original polarized state
how a nerve works1
How a nerve works
  • Resting neuron
    • Lots Na+ outside membrane and K+ on inside
    • Charge is + outside and - inside due to Cl- and proteins on inside of membrane
    • Maintained by Na-K pumps
how a nerve works2
How a nerve works
  • Resting neuron
    • Neuron said to be polarized
    • Charge difference across membrane called _________ potential. About -70 millivolts (mV)
how a nerve works3
How a nerve works
  • Resting neuron movie
how a nerve works4
How a nerve works
  • Firing neuron
    • stimulus arrives
    • if stimulus is enough, causes neuron to fire
    • firing is production of an action potential across membrane: change in _____________ distribution
    • goes from -70 mV (resting potential) to +30 mV (at peak of action potential)
how a nerve works5
How a nerve works
  • Firing neuron
    • 1) membrane channels open to allow Na+ to rush in
    • 2) extra K+ channels open and lots of K+ flows out
    • This repolarizes membrane
    • 3) Refractory period: time during which original state is regenerated by Na-K pumps. During this time, neuron __________ fire again.
how a nerve works6
How a nerve works
  • The firing neuron movie
how a nerve works7
How a nerve works
  • Nerve firing:
    • All or none response. A nerve either fires or it doesn’t
    • Very brief. Lasts about ________ millisecond
    • Transmitted along sections of axon like “the wave” in a stadium
how a nerve works8
How a nerve works
  • Myelin sheaths speed impulse movement
    • allow action potential to jump between nodes
    • action potential only produced at nodes, not in between
how a nerve works9
How a nerve works
  • Myelin sheaths speed impulse movement
    • like stadium with sections of empty seats. “Wave” jumps to next filled section
    • called saltatory conduction
how a nerve works10
How a nerve works
  • Note speed of myelinated axons
  • Note also that axon diameter influences speed of impulse. Larger axon, ___________ speed.
neuron to neuron transmission
Neuron to neuron transmission
  • 2 neurons usually don’t touch
  • Share synapse: tiny intercellular space (synaptic cleft)
neuron to neuron transmission1
Neuron to neuron transmission
  • Chemical transmission of impulse:
    • 1)Action potential in firing axon stimulates release of synaptic vesicles into synapse
neuron to neuron transmission2
Neuron to neuron transmission
  • Chemical transmission of impulse:
    • 2) Vesicles contain neurotransmitters
    • 3) Neurotransmitters diffuse across cleft to _________ proteins in postsynaptic membrane (dendrite of other neuron or muscle cell as shown here)
neuron to neuron transmission3
Neuron to neuron transmission
  • Chemical transmission of impulse:
    • 4) Receptor proteins cause start of action potential in postsynaptic membrane
    • 5) Enzymes ______________ neurotransmitters when transmission is completed. Prepares synapse for the next impulse.
neurotransmitters
Neurotransmitters
  • Vital substances in transfer of messages between neurons
neurotransmitters1
Neurotransmitters
  • 2 main types
    • 1) excitatory transmitters: cause depolarization of postsynaptic membrane
    • 2) inhibitory transmitters: stabilize membrane against depolarization
neurotransmitters2
Neurotransmitters
  • Acetylcholine: Neurotransmitter between motor nerve axon and skeletal muscle cell
  • Example of excitatory neurotransmitter
  • Causes depolarization of muscle cell membrane and stimulation of ________________
neurotransmitters3
Neurotransmitters
  • How stop stimulus? Acetylcholinesterase: enzyme breaks down acetylcholine
  • What happens if acetylcholinesterase inhibited? Muscle contraction uncontrolled.
  • This is _________......
  • Some chemicals designed to kill by inhibiting acetylcholinesterase
neurotransmitters4
Neurotransmitters
  • Nerve gas: works by inhibiting acetylcholinesterase
  • Example, VX gas featured in “The Rock”

VX gas spheres in “The Rock”

neurotransmitters5
Neurotransmitters
  • Nerve gas: works by inhibiting acetylcholinesterase
  • Example, sarin gas
  • Used in Tokyo subway attack by religious cult in 1995 (12 dead)
neurotransmitters6
Neurotransmitters
  • Nerve gas: works by inhibiting acetylcholinesterase
  • Example, sarin gas
  • Used by Saddam Hussein and his pal “Chemical Ali” in 1988 against Kurds at Halabjah (5,000 killed)
neurotransmitters7
Neurotransmitters
  • Nerve gas: works by inhibiting acetylcholinesterase
  • Example, sarin gas
  • US Army used incinerator at Anniston AL to destroy some sarin gas (Sept. 2003)
neurotransmitters8
Neurotransmitters
  • GABA: an inhibitory neurotransmitter
  • Allows ________ into neuron membrane, making it even more negative inside.
  • Thus harder to develop action potential
neurotransmitters9
Neurotransmitters
  • Some sedatives take advantage of GABA mechanism
  • Ex, Valium: enhances binding of GABA to its receptors. Harder for neurons to fire.
neurotransmitters10
Neurotransmitters
  • Serotonin: Involved in sleep regulation and emotional states
  • Insufficient serotonin production involved in depression, Parkinson’s disease
neurotransmitters11
Neurotransmitters
  • Prozac: blocks reabsorption of serotonin to make up for _________ of production
neurotransmitters12
Neurotransmitters
  • Serotonin
  • LSD: blocks serotonin receptors in portion of brain to produce hallucinations or “trip”
neurotransmitters13
Neurotransmitters
  • Cocaine: Affects neurons in brain’s “pleasure pathways” (limbic system)
neurotransmitters14
Neurotransmitters
  • Slows reabsorption of transmitters, so pleasure messages intensified
neurotransmitters15
Neurotransmitters
  • Addiction: body adjusts to drug. Example, cocaine
  • Decrease number of neurotransmitter receptors
  • When drug removed, synapse _________ sensitive
neurotransmitters16
Neurotransmitters
  • Addiction example, nicotine
neurotransmitters17
Neurotransmitters
  • Nicotine binds to brain receptors that normally bind acetylcholine
  • Influences a number of other neurotransmitters and their receptors
  • Result is stimulating
neurotransmitters18
Neurotransmitters
  • Problem: brain cells adjust numbers and sensitivities of many brain receptors
  • If nicotine removed (stop smoking), system unbalanced. Effects unpleasant
neurotransmitters19
Neurotransmitters
  • Example, nicotine
  • Takes time to recover
synaptic integration
Synaptic Integration
  • Recall that there are two types of neurotransmitters: excitatory and inhibitory
  • So, synapses can be either excitatory or inhibitory, depending on the neurotransmitter produced
  • CNS neurons often receive input from many other neurons
synaptic integration1
Synaptic Integration
  • Example, 1 spinal cord motor neuron might have 50,000 synapses!
  • Action of that neuron depends on the total effect of both excitatory (red) and inhibitory (blue) inputs
parts of the nervous system
Parts of the Nervous System
  • Central nervous system: brain and spinal cord
parts of the nervous system1
Parts of the Nervous System
  • Brain: Hindbrain
    • 1) Medulla oblongata: continuation of spinal cord. Pathway to higher brain centers (traffic controller)
    • Contains reflex centers that control: breathing, heart rate, blood pressure, swallowing
    • Damage to this area is __________!
parts of the nervous system2
Parts of the Nervous System
  • Brain: Hindbrain
    • 2) Pons: carries impulses from one side of ______________ to other. Regulates chewing, salivation, facial expressions, eye movements
parts of the nervous system3
Parts of the Nervous System
  • Brain: Hindbrain
    • 3) Cerebellum: receives information from sense organs, muscles, cerebrum
    • Involved in equilibrium, coordination of muscles
parts of the nervous system4
Parts of the Nervous System
  • Brain: Midbrain
    • 4) Small area in humans: midbrain connects hindbrain to forebrain
slide57
5) Brain: Forebrain
  • Cerebrum: Main processing center. Regulates vision, speech, hearing, olfaction, memory, logic, consciousness, etc.
slide58
5) Brain: Forebrain
  • Thalamus: analyzes sensory information and relays it to cerebrum
  • Hypothalamus: regulates sleep, metabolism, body temperature, water balance, appetite, thirst, pleasure
  • Note connection of hypothalamus to _____________ gland
brain comparisons
Brain comparisons
  • Humans with highly developed cerebrum: largest portion of brain
parts of the nervous system5
Parts of the Nervous System
  • Spinal cord: cable of neurons running down back. Information highway!
  • Inner zone: gray matter. Interneurons and cell bodies of motor neurons
  • Outer zone: white matter. Axons and dendrites of neurons.
parts of the nervous system6
Parts of the Nervous System
  • Spinal cord: also contains reflex arcs
  • Very fast responses because information doesn’t travel to _______________ for processing
parts of the nervous system7
Parts of the Nervous System
  • 2 neuron arc: has only sensory and motor neuron involved. Example, knee jerk reflex
parts of the nervous system8
Parts of the Nervous System
  • 3 neuron arc: has sensory and motor neuron, but ________________ present also. Example, cutaneous spinal reflex
parts of the nervous system9
Parts of the Nervous System
  • Brain to spinal cord mass ratio
  • Gives rough measure of intelligence
  • Fish/amphibians 1:1
  • Cat 4:1
  • Tailed monkey 15:1
  • Human 55:1
  • ____________ 61:1
  • Who’s more intelligent??
parts of the nervous system10
Parts of the Nervous System
  • Peripheral Nervous System
    • Afferent system: carry impulse from sensory neuron to CNS. Sensory pathways.
    • Efferent system: carry impulses from CNS to muscles (effectors). Motor pathways.
parts of the nervous system11
Parts of the Nervous System
  • Peripheral Nervous System
    • Efferent system: carry impulses from CNS to muscles (effectors). Motor pathways.
      • Somatic: CNS to skeletal muscles (_________________)
      • Autonomic: CNS to smooth muscles (involuntary)
parts of the nervous system12
Parts of the Nervous System
  • Peripheral Nervous System
    • Autonomic: CNS to smooth muscles (involuntary)
    • Made of two antagonistic subdivisions (have __________ effects)
      • 1) Sympathetic
      • 2) Parasympathetic
parts of the nervous system13
Parts of the Nervous System
  • Autonomic
    • 1) Sympathetic (on edge). Speed up body functions and activities to prepare for defense
    • Increase heart rate, glucose release, decrease blood to digestive system, more blood to muscles
parts of the nervous system14
Parts of the Nervous System
  • Autonomic
    • 2) Parasympathetic (laid back)
    • _________________ of sympathetic system
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