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A+P 1 > Chapter 11: Nervous Tissue > Flashcards

Chapter 11: Nervous Tissue Flashcards

1
Q

Functions of Nervous Tissue

A
  1. Gather Information- receptors detect change (stimuli)
  2. Integration- analysis of stimuli
  3. Activation of Effectors- perform response
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2
Q

Function of Nervous Tissue: Gather Information

A

receptor: a neural structure that detects changes in the environment called stimuli

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3
Q

Function of Nervous Tissue: Integration

A

analysis of stimuli (what is their significance/ meaning)

-formulation of appropriate response(s)

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4
Q

Function of Nervous Tissue: Activation of Effectors

A

to perform the response generated during integration

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5
Q

Central Nervous System (CNS)

A
  • brain spinal cord

- perform integration (non-stop)

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6
Q

Peripheral Nervous System (PNS)

A

-contains all neural structures outside brain + spinal cord
-send information TO and FROM the CNS
ex:
to from
environment –> CNS –> effectors
l l
sensory division motor division
send info to CNS conducts info from CNS

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7
Q

Motor Division of PNS has 2 Branches:

A
  1. Somatic

2. Autonomic

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8
Q

PNS Motor Division Branch: Somatic

A

communications with “voluntary effectors” (effectors you can consciously control)
-skeletal muscles

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9
Q

PNS Motor Division Branch: Autonomic

A

communications with “involuntary effectors” (effectors you can not consciously control”

  • cardiac muscles, smooth muscle, glands
  • sympathetic- mobilizes body systems during activity
  • parasympathetic- conserves energy; promotes house-keeping functions during rest
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10
Q

Cells In Nervous Tissue?

A
  1. Neurons- send receive chemical + electrical “messages” (non-stop)
  2. Glia (neuroglia)- support + take care of neurons
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11
Q

Examples of Glia In The Central Nervous System (CNS): Astrocytes

A
  1. Astrocytes- connect CNS neurons to blood stream
    - feed neurons
    - move neuron waste in blood
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12
Q

Examples of Glia in The Central Nervous System (CNS): Oligodendrocytes

A
  1. Oligodendrocytes- from myelin sheaths which help speed transmission of electricity through a neuron
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13
Q

Examples of Glia In The Peripheral Nervous System (PNS): Schwann Cells

A

Schwann cells- form myelin sheath

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14
Q

Characteristics of Neurons

A
  1. Irritable- easily stimulated (in producing responses)
  2. Amitotic- cant divide (don’t do mitosis)
  3. long lived
  4. Very Metabolically Demanding- require large + constant amounts of glucose and oxygen
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15
Q

Parts of a Neuron: Cell Body (Soma)

A

part of the neuron that directly surrounds the nucleus

  • biosynthetic center of cell (any chemical that the neuron makes has to be in the cell body then shipped to where needed)
  • “decision maker” for neuron because it contains nucleus
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16
Q

Part of a Neuron: Dendrite

A

“branches”

  • contain large concentrations/ densities of neurotransmitter receptors
  • input regions- (bringing information to the cell body)
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17
Q

Part of a Neuron: Axon

A

(comes out of a cone-shaped structure called a hillock)
-send electrical impulses called Action Potentials from its Axon Hillock to its Axon Terminals (end of neuron) to release neurotransmitters
axon= output region

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18
Q

Classifying Neurons: based on a # of processes

A
  • multipolar neuron- more than 2
  • bipolar- 2
  • unipolar-1
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19
Q

Classifying Neurons: based on activity

A
  • sensory- send info toward CNS
  • motor- send info from CNS
  • interneurons- perform integration
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20
Q

Neurophysiology (how neurons work):

Voltage

A

A separation of charge with respect to a barrier

  • when opposite charges are separated (by barrier), energy is STORED
  • allowing opposing charges to contact one another RELEASES energy
21
Q

Membrane Potential

A

the voltage occurring at the plasma membrane’ measured in milliVolts (mV)
(neurons use plasma membrane as a barrier)

22
Q

Resting Potential; Resting Membrane Potential (RMP)

A

the membrane potential of a neuron at “rest” ( a neuron that is not currently sending or receiving information) [-70 mV] (charge of inside of the cell compared to the outside)

23
Q

Establishment + Maintenance of RMP

How is the cell -70mV?

A
  1. at “rest”, Na+ (sodium) is diffusing INTO a neuron and K+ (potassium) is diffusing OUT. However, more k+ is diffusing out than Na+ is diffusing in.
  2. because more (+) charge is diffusing out than is diffusing in, the inside of the membrane behaves as if its -70 mV compared to the outside.
    (Na+ and K+ diffusion produce (establish) RMP)
  3. Na+ and K+ ions must continue to diffuse in order for the neurons membrane potential to be maintained
  4. Proteins called Sodium-Potassium Pumps spend ATP to actively transport “diffused” Na+ and K+ back to their high-concentration areas
    (move sodium and potassium back to their original place to start again like a loop)
    -Sodium Potassium Pumps maintain membrane potential by making sue that Na+ and K+ continue to diffuse
24
Q

Changing Membrane Potential

A

depolarization- more (+)
hyperpolarization- more (-)
These are made to occur through the opening of Voltage-Gated Ion Channels (open in response to voltage)

25
Q

Depolarization

A

making membrane potential more positive
to depolarize, open gated Na+ channels

Na low
————–

26
Q

Hyperpolarization

A

making membrane potential more negative
to hyperpolarize, we would open K+ channels (allowing (+) to leave the cell

K+ high (high to low) diffuse into the outside
————-
K+ low

27
Q

Membrane Potential changes as a neuron sends 2 kinds of electrical “messages”:

A
  1. Graded Potential-share info among itself

2. Action Potential- talk to other cells

28
Q

Membrane Potential changes with 2 kinds of electrical messages: 1. Graded Potential

A

“Short Distance” messages sent from one part of a neuron to another part of that same neuron
(ex: dendrites tell soma (cell body) about messages they’ve received)

29
Q

Membrane Potential changes with 2 kinds of electrical messages: 2. Action Potential

A

sent from the axon hillock to axon terminal

-cause terminals to release neurotransmitters

30
Q

Action Potential

A

a quick reversal in membrane potential from rest (RMP) (-70mV) to +30mV and back
-releases the energy needed for the terminals to release neurotransmitters

31
Q

Events of the Action Potential

A
  1. A stimulus depolarizes (+) the neuron to Threshold (-55mV)
  2. At Threshold, voltage-gated Na+ channels open
    -neuron depolarizes to +30mV as Na+ enters neuron
    ENERGY is released
  3. At +30mV:
    -Na+ entry stops
    -Na+ gates begin to close
    -voltage-gated K+ channels open and membrane potential hyperpolarizes (goes back down)
  4. K+ gates open longer than needed to reach RMP(resting membrane potential) producing an undershoot
32
Q

An Action Potential is created at the ____, this action potential must be propagated to the ______

A
  1. Axon Hillock

2. Axon Terminals

33
Q

Propagation of an Action Potential

A
  1. At hillock, as Na+ enters, energy is released
  2. This energy makes the next part of the axon reach threshold; Na+ enters
  3. This releases energy that makes the next part of axon reach threshold + causes Na+ to enter
  4. These events continue until an action potential reaches the terminals
34
Q

An Action Potential is an “All or Nothing” event

A
  1. Threshold is reached at the axon hillock, and an action potential propagates all the way to the terminals as fast as possible or,
  2. Threshold is not reached + nothing happens
35
Q

Because all of a Neurons Action Potentials are propagated at the same speed, a neuron alters its ______ to convey information about stimulus strength

A

Firing Frequency
(each neuron sends action potentials as fast as they can go (maximum speed))
ex: where there is dim light they send a lower frequency + at bright light they send a higher frequency

36
Q

Firing Frequency is limited by

A

Refractory period

37
Q

Absolute Refractory Period

A

Period of time during which sodium gates are open and a neuron cant fire
-a neuron can not be made to fire while its sodium gates are open
(gates open at threshold), (from threshold back to Resting membrane potential (RMP))
-as soon as sodium channel is closed it can fire again

38
Q

Relative refractory Period

A

during the “undershoot” a neuron can be made to fire, but only if it receives a suprathreshold stimulus (bigger stimulus)
-whether or not it fires is relative whether you can do the extra cost

39
Q

Factors influencing propagation speed

A
  1. Axon Diameter

2. Presence of myelin

40
Q

Factors influencing propagation speed

1. Axon Diameter

A

Thicker axons offer less resistance to the flow of electricity (thicker, the more faster)
-ex: electricity flows like a milkshake, easier to drink a milkshake through a thicker straw)

41
Q

Factors influencing propagation speed

2. Presence of Myelin

A

-myelin insulating an axon, helping keep electrical charge within the axon
(does not let electricity escape, action potentials travel farther)
-unmyelinated axon; without myelin its electrical charge spills outside the axon; travels shorter

42
Q

Synapse

A

point of communication between 2 excitable cells
2 Types:
-electrical
-chemical

43
Q

Electrical Synapse

A

a membrane junction like an intercalated disc allows electricity to flow easily between cells
-fast, bidirectional (right to left, left to right)

44
Q

Chemical Synapse

A

makes use of chemicals called neurotransmitters

  • unidirectional (one cell is the sender, the other is the receiver)
  • presynaptic cell (sender)
  • postsynaptic cell (receiver)
45
Q

Transmission at a Chemical Synapse

when axon gets to terminal

A
  1. An action potential reaches an axon terminal
  2. Action potential causes Voltage-Gated Calcium Channels to open, and Calcium enters the terminal
  3. Calcium causes organelle, Synaptic Vesicles to release neurotransmitters
  4. Neurotransmitters diffuse across the Synaptic Cleft to postsynaptic cell
  5. Neurotransmitters open gated ion channels in postsynaptic cell
  6. This causes postsynaptic cell to create Graded Potentials which are sent to the postsynaptic soma (cell body)
46
Q

Excitatory Postsynaptic Potential (EPSP)

A

If neurotransmitters open gated Na+ Channels in postsynaptic cell, that cell creates a depolarizing graded potential called a Excitatory Postsynaptic Cell
-bringing closer to threshold

47
Q

Inhibitory Postsynaptic Cell (IPSP)

A

If neurotransmitters open gated K+ channels, an inhibitory postsynaptic cell is created
-pulled away from threshold (inhibition)

48
Q

EPSP’s + IPSP’s travel to the postsynaptic soma (axon hillock)

A

if they cause the hillock to reach threshold, the hillock fires

49
Q

ESPS and IPSP are summated

A

-added up
ex: -70mV RMP
+12mV EPSP 1
-8mV IPSP
+7mV EPSP 2
————————————–
-59mV
(wont fire action potential, did not reach threshold(-55mV)

A+P 1 (15 decks)

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