Chapter 11 pt 1) Fundamentals of Nervous System

Question 1

The Nervous System (Overview and Functions)

Answer 1

• Master control of the body
• Communicate via Electrical and Chemical Signals
  
  • Signals are Rapid and Specific
  • Response is usually immediate
• Three Functions of Nervous system
  
  1. Sensory Input) Gather information and through sensory receptores (affrent pathway)
  2. Integration) Processing and interpretation of sensory input (Control center)
  3. Motor Output) Activation of effector organs (muscles/glands). Produces a response. (effrent pathway).

Question 2

Two Divisions of the Nervous System

Answer 2

• CNS) Central Nervous System
  
  • Brain and Spinal cord
  • Inegration and Control Center. Determines motor output
• Prepherial Nervous System
  
  • Any nervous tissue ouside of CNS
  • Consists of nerves that extend from the brain and spinal chord
    
    • Spinal nerve) connects to spine
    • Cranial nerve) connects to brain.

Question 3

Prepherial Nervous System (Two Divisions)

Answer 3

• Sensory (Afferent) Division
  
  • Somatic sensory fibers) convay inpulses from skin, muscles, and joints to CNS.
  • Viseral Sensory Fibers) Convay Impules from visceral (internal) organs.
• Motor (Efferent) Division
  
  • Transmits Impules from CNS to motor nuerons.
  • Two divisions) Somatic and Autonomic

Question 4

Somatic Nervous System

Answer 4

• Nerve Fibers conduct impules from CNS to skeletal muscles
• Called the Voluntary Nervous System
  
  • Concious Control of Skeletal Muscles.

Question 5

Autonomic Nervous System

Answer 5

• Visceral Motor Nerve Fibers
• Regulates smooth muscles, cardiac muscles, and glands
• Called the Involuntary Nervous system
• Two divisions
  
  • Sympathetic) Fight Or Flight System
  • Parasympathetic) Rest and Digest System.
  • Two systems work oppiosite to eachother

Question 6

Histology of Nervous Tissue

Answer 6

• Nuerons) Excitible cells that transmit signals
• Nurogalieal cells) Support, protect and insulate Nuerons
  
  • Four main types in CNS
    
    • Astrocytes
    • Microglial Cells
    • Ependymal Cells
    • Oligodendrocytes

Question 7

Astrocytes

Answer 7

• Most abundant, versitile, and highly branched galial ce;;s/
• Cling to nuerons, synaptic endings, and capaliries
• Many functions which include
  
  • Support and Bracing of Nuerons
  • Exchanges between capaleries and nuerons
  • Guide Migration of Young Nuerons
  • Control enviornment around nuerons
  • Respomd to nerve impules and nuerotransmiters

Question 8

Microgalial cells

Answer 8

• Small, Ovoid Cells with thorny processes that touch and moniter nuerons.
• Migrate toward injured nuerons and can transform and phagocytize (remove) microrganisms and nueronal debris.

Question 9

Epedymal cells

Answer 9

• Line fluid filled cavities in CNS and provide a barrier between cerebrospinal fluid and other fluid
• Can be columnar or squamous, some are cilliated

Question 10

Oligodendrocytes

Answer 10

• Form thick Myelin Sheaths which insulare nerve fibers.

Question 11

Nueroglia In PNS

Answer 11

• Sataleite Cells) Surround nueron cell bodies in PNS
  
  • Similar function to Astrocytes
• Schwann Cells) Completely surround prepherial nerve fibers and form mylin sheaths
  
  • Similar function to oligodendrocytes

Question 12

Nuerons

Answer 12

• Structural Units of nervous system
• Last for a persons entire lifspan without dividing. (olfactory eptheliam does)
• All have a Cell body and one or more processes
  *

Question 13

Cell Body (Perikaryon or Soma)

Answer 13

• Biosynthetic Center
  
  • Synthesises Protiens, Membranes, And Chemicals
  • Done in Rough ER (Also called Nissil Bodies)
• Most are located in CNS
  
  • Nuclei) Clusters of nueron cell bodies in CNA
  • Ganglia) Clusters of Nueron Bodies in PNS

Question 14

Nueron Processes

Answer 14

• Extend from the body of the nerve
  
  • CNS) Contains cell bodies and processes
  • PNS) mostly cell processes
• Tracts) Bundels of nueron processes in the CNS
• Nerves) Bundles of nueron processes in the PNS
• Two types
  
  • Axons and Dendrites

Question 15

Dendrites

Answer 15

• Short, tapering, branched processes
  
  • Contain same organelles as cell body
• Recive (input) regoin of the nueron
  
  • Never goes out
  • Convay messages to cell body as Graded Potential
• Contain Dendric spines
  
  • bulbous or spiky
  • point of contact (synapse) with other nueron.

Question 16

The Axon (Structure)

Answer 16

• Only one per nueron. Attached to cone shaped area called Axon Hitchcock.
• Axon can be short or almost the entire length of the cell
  
  • Some over 1 meter long
• Occasionally branched at a place called axon collaterals.
• At the ends of axons there are thousands of branches
  
  • These brances are called Axon Terminals

Question 17

Axon (Funtions and Charcteristics)

Answer 17

• Conduction region of nueron
• Nuerons generate nerve impules and then transmit them along the cell membrane (axolemma) to Axon Terminal.
  
  • Terminal) place that secretes nurotransmitters
  • Nuerotransmiters excite or inhibit nuerons
• Lack Golgi apperatus and ER

Question 18

Transport On the Axon (2 ways)

Answer 18

• Molecules and Organelles are moved along axons by motor protiens in two directions
• Anterograde) away from the cell body
  
  • EX) Midochondria, Cytoskeletal elements, membrane componants, enzymes.
• Retrograde) Toward Cell body
  
  • EX) organelles that need to be destroyed, signal molecules, viruses, and toxins (to be destroyed)

Question 19

Myelin Sheath

Answer 19

• Myelin) protien-lipid substance that protects and electrically insulates the axon.
  
  • Increases nerve tansmission speed
• Mylinated Fibers) Most long or large diamater Axons
• Nonmylinated Fibers) conduct impules more slowly.

Question 20

Mylenation in PNS

Answer 20

• Function of Schwarnn cells
  
  • Cell coils around Axon and wraps itself tight
  • Outer collar of Perinuclar Cytoplasm contains nucleus
• No protien channels or carriers so they are good at electrical insulation.
• Signal Jumps on Nodes of Ravier (gaps between adjacent Schwann cells)

Question 21

Myelination in CNS

Answer 21

• Formed by Oligodendrocytes but not the whole cell
  
  • Each cell can wrap 60 axons at once
  • Myelin sheath gap is present

Question 22

Structural Classification of Nuerons (3 types)

Answer 22

• Multipolar) Have three or more processes (one axon)
  
  • Most common; major in CNS
• Bipolar) 2 processes, 1 axon and one dendrite
  
  • Rare, (Retina and Olfactory Mucosa)
• Unipolar) 1 short T like process, 2 axons
  
  • Also called psuedounipolar
• Prepherial Process) Associated with Sensory Receptor
• Central Process) Enter the CNS
  
  • Found in Ganglia.

Question 23

Functional Classification of Nuerons

Answer 23

• Sensory (afferent) Transmit impulses from sensory receptors to CNS
• Motor (Efferent) Carry impulses from CNS to effectors.
  
  • Multipolar. Most cell bodies are located in CNS
• Internuerons) Association Nuerons
  
  • Between sensory and motor nuerons
  • Shuttle signals through the CNS pathway. Most are in CNS
  • 99% of the bodies nuerons are internuerons.

Question 24

Membrane Potentials

Answer 24

• Nuerons have a resting membrane potential that they can rapidly change
• Nerves respond to stimilus by creating an action potential (nerve impulse).
  
  • Impulse is the same regardless of the channel it came through.

Question 25

Roles of Membrane Ion Channels

Answer 25

• Leakage (nongated) channels) Always open
• Gated Channels) Protien changes shape to open
  
  • When channels are open ions diffuse quicky across membrane.
  • Diffuse doen chemical and electrical gradients. (electrochemical gradient)
• Three types
  
  • Chemically Gated) Open when chemical binds
  • Voltage Gated) Open in response to changes in membrane potential
  • Mechanically Gated) open in close in response to receptors.

Question 26

Resting Membrane Potential

Answer 26

• Of a resting nueron) -70mV
  
  • cytoplamsic side is slightly negative
  • actual voltage varries from -40 to -90 mV
• Membrane is said to be polarized
• Potential is made by
  
  • Diffrences in ionic compisition of ECF and ICF
  • Diffrences in plasma membrane permabiltiy.

Question 27

Diffrences in Ionic Compisition

Answer 27

• ECF) has more Na+ than ICF
  
  • Balanced by clorine ions (Cl-)
• ICF has higher concentration of K+ than ECF
  
  • Balanced by negativly charged protiens.
• K+ plays the most improtant role in RMP

Question 28

Diffrences in Membrane Permiability

Answer 28

• Impermiable to large, anionic protiens.
• Slightly Permiable to Na+
  
  • Sodium diffuses into cell down concentration gradient
• Membrane is 25 times more permiable to K+ than sodium
  
  • Potassium diffuses out of cell
• Permiable to Cl-
• More potassium diffused out than sodium goes in
  
  • As a result the inside of the cell is more negavitve
  • This charge makes RMP
• Sodium Potassium Pump
  
  • Mantains concentration gradient of Na+ and K+
  • Three Na+ pumped out and two K+ pumped in

Question 29

Changing Membrane Potential

Answer 29

• Membrane Potential Changes when
  
  • Ion concentration changes
  • Membrane permiabilty to ions change
• Changes produce two signals
  
  • Graded Potential) short distance signals
  • Action Potential) long-distance axons
• Changes in RMP send, inegrate, and recive information.
• Changes in membrane potential are relative to RMP
  
  • Deplorization) decrese in membrane potential
    
    • Inside is less negative
    • Impulse probability increases
  • Hyperpolarization) Increase in membrane potential
    
    • Inside is more negative
    • Impule probability decreses.

Question 30

Action Potential

Answer 30

• Long distance signal sending
• Occurs in mucle cells and Axons of nuerons
• Breif reversal of membrane potential with change in voltage. Carries signal long way
• Also refered to as a Nerve Impulse.

Question 31

Four Steps of Action Potential

Answer 31

1. Resting State) All Na+ and K+ channels are closed
   
   • Only leakage channels are open.
   • Na+ channels have two voltage sensitive gates
     
     • Activation gates) closed at rest
     • Inactivation gates) open at rest, channel is blocked so Na+ can’t enter
   • K+ channel is closed at rrst
2. Deplorization) Na+ channels open
   
   • Na+ rushes in and gates open
   • Eventually all channels open (at -55 to -50 mv) and ICF is less negative.
3. Repolarization) Na+ channels inactivate and K+ channels open
   
   • K+ exits cell down concentration graident
4. Hyperpolarization) Some K+ channels remain open
   
   • Inside of membrane becomes more nagative
   • causes slight hyperpolarization

• Once channels close Na+/K+ pumps restore orginal balance.

Question 32

Graded Potentials

Answer 32

• Short Lived, Local messages that can die off
  
  • Stronger the stimulus, the more voltage changes and the further the current flows.
• Trigegred by the stimulius that opens gated ion channels.
  
  • Once channel opens, deplorization spread
    *