Chapter 11 Part 2) Nervous System

Question 1

Threshold and All-Or-None Phenomenon

Answer 1

• Describes how Action Potention needs a certian level of energy to start.
• Threshold) Weakest stimulis to start AP
  
  • Membrand is deplorized by 15 to 20 mv from rest
  • Na+ permibality increases which begins AP
• All or Nothing) Either signal fires or dosn’t. Will not stop.

Question 2

Propagation of AP

Answer 2

• Allows AP to be transmited along the Axon to terminals.
• This allows it to be a message.
• AP only moves in one direction, message will continue to terminal.

Question 3

Stimulius Intensity

Answer 3

• CNS tells the diffrence in Strength of AP by its Frequency.
  
  • Higher frequency means stronger stimilus.

Question 4

Refractory Periods (two)

Answer 4

• Time in which nueron cannot trigger another AP
• Absolute Refractory Period) Opening of Na+ channels to the resting of those channles.
  
  • Enforces one way transmision
  • New AP cannot Start during this time
• Refractory Periods) Follows Absolute Refractory Period.
  
  • Most Na+ channels are in resting state.
  • Some K+ channels open, Repolarization is occuring.
  • New AP can Start but signal has to be very strong.

Question 5

Conduction Velocity (Factors)

Answer 5

• Axon Diamater) Larger Diameter Axons send Signal faster
• Degree of Mylnation
  
  • Coninuoius Conduction) Slow conduction in unmylenated areas
  • Salatory Conduction) occurs in myelinated axons. about 30 times faster.

Question 6

Multiple Sclerosis

Answer 6

• Autoimmune dieseise where myelin in CNS is destroyed
  
  • Myelin turned into hardened scleroses
  • Slows nerve conduction
• Symptoms
  
  • Visual disturbances, weakness, loss of muscular control, speach distubences
• Treatment)
  
  • Drugs that modify immune system activity
  • High vitamian D levels.

Question 7

Nerve Fibers (based on conduction velocity)

Answer 7

• Group A Fibers) Largest diamater
  
  • Mylinated somotatic sensory and motor fibers of mucles, skin and joints
• Group B Fibers) Intermediate Size
  
  • Lightly Myelinated
• Group C) Smallest size
  
  • Unmylinated.

Question 8

The Synapse

Answer 8

• Junctions that mediate transfer from one nueron to another
• Presynaptic Nueron) Nueron that seds the impulse
• Postsynaptic Nueron) Nueron that recives the impulse.
  
  • May be nueron, muscle cell, or gland cell

Question 9

Synapse Calssifications

Answer 9

• Most Common
  
  • AxoDendric) Between Axon and Denrite
  • AxoSomatic) Between Axon and Synapse
• Less Common
  
  • Axoaxonal) Axon to Axon
  • Dendrodendric) dendrite to dendrite
  • Somatodendric) Dendrite to soma

Question 10

Eletrical and Chemical Synapses

Answer 10

• Electrical Synapse) Less common than chemical synapse
  
  • Nuerons are electrically conected
  • Very rapid communication
• Chemical Synapse) More Common) Specilized for release of nuerotrnsmitters
  
  • Axon Terminal sends Synaptic Vessicles filled with nuerotransmiters to Receptor Region of Postsynaptic nueron.
  • Seperated by synaptic cleft. Electrical Impulse is changed to chemical then back to electrical.

Question 11

6 Steps in Info Transfer Across the Chemical Synapse

Answer 11

1. AP arrives at Axon Terminal of Postsynaptic Nueron
2. Voltage gated Ca+ channels open and Ca+ enters terminal
3. Ca+ entery causes the synaptic vessicles to release nuerotransmiter
4. Nuerotransmitter diffuses across the synaptic cleft and binds to receptors
5. Binding created graded potential in posynaptic cell
6. Nuerotransmitters are terminated) 3 ways
   
   • Reuptake) By astrocytes or Axon Terminal
   • Degradation) by enzymes
   • Diffusion) away from synaptic cleft.

Question 12

Synaptic Delay

Answer 12

• Time for nuerotransmiter to be released and then bind to receptor.

Question 13

Postsynaptic Potentials (2 Types)

Answer 13

• EPSP) Excitatory postsynaptic potential
  
  • Nuerotransmiter opens gated channels allowing Na+ and K+ to flow
  • Can result in AP if EPSP is strong enough
• IPSP) Inhibitory postsynaptic potential
  
  • Nuerotransmiter makes membrane more permiable to K+ and Cl-
  • Reduces ability to produce an A

Question 14

Summation of Postsynaptic Nueron

Answer 14

• EPSP’s can summate together and create an AP
  
  • A singer EPSP cannot create an AP
• ISPS’s also summate into equation
• Two Types of summations
  
  • Temporal) One or more nueron fires in rapid order
  • Spatial) Postsynaptic nueron is stimulated by many nuerons simultaneously

Question 15

Synaptic Potentiation

Answer 15

• Repeated Use of synape increases ability of presynaptic cell to excite posynaptic cell.
  
  • Leads to more effective stimuli
  • Learning called Long-Term Potentiation

Question 16

Presynatpuc Inhabition

Answer 16

• Release of excitatory nuerotransmiter by one nueron is inhibited by another nueron via an axoaxonal synapse.
• Less nuerotransmiuter is released as a result.

Question 17

Nuerotransmiters (types by chemical structure)

Answer 17

• Language of Nervous System
• Acetocholiene) First identifed nuerotransmiter
• Biogenic Amines
  
  • Catecholamines) Dopamine, Norepiherine, Epinephrine
  • Indolamines) Seratonin, Histamine
  • Used In brain for behiavor or biological clock
• Amino Acids
  
  • Gualtamate, Aspartate, Glycine, GABE
• Peptides
  
  • Substance P, Endorphanes
• Purines) Monomers of Amino Acids that can affect CNS and PNS
• Gasotranmsiters) Gasses and lipids
  
  • NO and CO

Question 18

Classification of Nuerotransmitter by Function

Answer 18

• Effects) Excitatory vs Inhibitory
  
  • Determined by which receptor it binds
• Actions) Direct Vs Indrirect
  
  • Direct) Nuerotransmiter binds to direclty and opens an ion channel
  • Indirect) Nuerotransmitter acts through intercellular messangers
• Types of Receprors
  
  • Channel Linked) Ligand gated, Fast
  • G Protien) Indirect slow response because it has to activate another messanger.

Question 19

Nueral Integration

Answer 19

• Nuerons functioning together in groups to make broader nueral functions.

Question 20

Nueronal Pool

Answer 20

• Functional froups of Nuerons
• Discharge Zone) Nuerons closer to the incoming inpulse
• Facilitated Zone) Nuerons farther from incoming pulse.

Question 21

Serial Processinf

Answer 21

• Input tracells on one specific pathway to its destination
  
  • One nueron stimulates the next
• Example of this is a spinal reflex
  
  • Rapid repsonse to stimuli
  • Reflex Arcs have 5 compnants
    
    • Receptor, Sensory Nueron, CNS, Motor Nueron, Effector.

Question 22

Parallel Processing

Answer 22

• Input travels on several pathways on the way to destination
  
  • Stimilus promotes multiple responses.

Question 23

Types of Circuts

Answer 23

• Diverging Circut) One Input, many Outputs
  
  • Called an amplifying circut
• Converging Circut) Many Inputs, One Output
  
  • Concentrating circut
• Reinverbirating Circut) Signal travels through a chain of nuerons which feed back to eachohter
  
  • called an oscillating circut. Controls rythmith activity
• Parallel after-discharge) Signal stimulates nuerons in parallel fashion that converge at end of sifnel
  
  • Impules reach output cell at diffrent times.