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Flashcards in Neural Tissue Deck (104):
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What are the 2 communication systems?

1. Nervous system
2. Endocrine System

1

Nervous system characteristics

-System that coordinates all body systems
-Accomplished by the transmission of signals
-Body part ---> central nervous system
-Central Nervous system --> body system
-Electrochemical signaling

2

Endocrine system characteristics

-Slower scaled system
-Uses chemicals in the blood stream called hormones

3

General make up of the nervous system (5)

1. Organs
2. Connective Tissue
3. Blood Vessels
4. Neurons
5. Neuroglia

4

2 groups or divisions of the Nervous System

1. Central Nervous System
2. Peripheral Nervous System

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The brain and the spinal cord

Central Nervous System

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The cranial and spinal nerves and ganglia

Peripheral Nervous System

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Components of the Central Nervous System (5)

1. Brain and Spinal Cord
2. Covers by meninges
3. Starts as a hollow tube
4. Bathed in cerebrospinal fluid
5. Integration center

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Components of the Peripheral Nervous System (3)

1. Consists of all cranial and spinal nerves that contain sensory and motor fibers
2. Connects CNS to muscles, glands, and all sensory receptors
3. Brings information to and from CNS

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2 divisions of the Peripheral Nervous System

1. Afferent Division = sensory
2. Efferent Division = motor

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2 divisions of the Efferent Division

1. Somatic Division
2. Autonomic Division

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General function of the Nervous System (5)

1. Receptors- detect stimuli
2. Sensory- afferent PNS
3. Integrative- CNS
4. Motor- Efferent PNS
5. Effector- Muscle/gland

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2 types of Nervous Tissue

1. Neurons
2. Neuroglial Cells

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-Structural and functional units
-Excitable
-Amitotic

Neurons

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-Accessory nerve cells
-Act like connective tissue

Neuroglial Cells

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3 Parts of a Neuron

1. Soma
2. Dendrites
3. Axon

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What is the Soma

-Cell body
-Mononucleate

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The soma consists of... (4)

1. Nissl Bodies - ribosomes clusters, give gray color
2. Axon Hillock- connects soma to axon
3. Perikaryon- Region around the nucleus
4. Neurofibrils- Cytoskeleton that extend into dendrites/axons and gives it its shape

19

Dendrite characteristics (4)

1. Respond to neurotransmitters
2. Short, branched, unmylelinated
3. Specialized for contact with other neurons
4. Conducts impulses toward the cell body

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Axon characteristics (4)

1. only 1 per cell
2. Conducts nerve impulses AWAY from the soma
3. Can give off collaterals
4. Many wrapped in myelin sheath, glial cells wrapped around the axon

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Where do axons end?

In synaptic terminals

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What do axons produce?

Neurotransmitters

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Neurotransmitters may contact these 3 things...

1. Another neuron
2. Muscle fibers
3. Glands

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The movement of cellular materials (NOT SIGNALS) through the axon

Axonal Transport
AKA Axoplasmic flow

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Away from soma, neurotrasmitters, organelles, and nutrients

Anterograde

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Towards soma, degraded materials to be recycled and extracellular substances

Retrograde

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-Cytoplasm of the axon

Axoplasma

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What does the axoplasma consist of? (2)

-Few organelles
-Cytoskeletal proteins

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What is the role of the cytoskeletal proteins? (3)

1. Form cytoskeleton
2. Maintain shape
3. Generate axonal transport

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-Plasma membrane of axon

Axolemma

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What does the axolemma consist of? (4)

1. Collaterals
2. Telodendria
3. Synaptic terminal
4. Synaptic Vesicles

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Side branches of axolemma

Collaterals

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Terminal Extensions of axolemma

Telodendria

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Part of axolemma that contains synaptic vesicles where neuron contacts postsynaptic cell

Synaptic Terminal

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Structural classification of neurons (4)

1. Anaxonic
2. Bipolar
3. Unipolar
4. Multipolar

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-Small neurons
-Axons can not be distinguished from dendrites
- In CNS- especially interneurons that coordinate special senses

Anaxonic

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-Several small dentrites converge onto one
-Dendrite and axon separated by soma
-Unmyelinated
-Sensory neurons of special sensory organs

Bipolar

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-Several small dendrites converge into one large one
-Dendrite and axon continuous
-Usually myelinated
-Majority of sensory neurons in PNS

Unipolar

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-Many dendrites extend from soma
-Long axon
-Myelinated
-Majority of motor neurons in PNS
-Spinal interneurons in CNS

Multipolar

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Characteristics of Afferent Neurons (4)

-Have sensory function
-Cell body usually are outside CNS
-Have receptor ends on dendrites or are associated with receptor cells in sense organs
-Carry impulses from peripheral body parts --> brain or spinal cord

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Receptors in Afferent neurons... (3)

1. Exteroceptors
2. Proprioceptors
3. Interoceptors

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Receptor that does...
-touch
-temperature
-pressure
-light
-chemicals

Exteroceptors

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Receptor that...
-monitors muscle and skeletal position

Proprioceptos

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Receptor that...
-monitor internal systems (digestion, respiration, and urinary system)

Interoceptors

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Neurons that...
-Only in CNS
-Classified based on effects (excitatory, inhibitory)
-Most abundant
-Link 2 or more neurons

Interneurons

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Neurons that...
-Have motor function
-Cell body is usually inside CNS
-Carries impulses from the brain or spinal cord to peripheral body parts

Efferent Neurons

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The 2 divisions of efferent neurons...

1. Somatic
2. Autonomic/Visceral

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Type of efferent neurons that controls skeletal muscle

Somatic Neurons

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Type of efferent neurons that are in smooth muscle and glands

Autonomic/Visceral

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Neuroglial Cells in PNS (2)

1. Satellite Cells
2. Schwann Cells

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Neuroglial Cells in CNS (4)

1. Astrocytes
2. Oligodendrocytes
3. Ependymal Cells
4. Microglia

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CNS Neuroglial Cell that...
-Largest and most common
-Star shaped

Astrocytes

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Functions of Astrocytes (5)

1. Structure and repair
2. Metabolism
3. Regulate ions and nutrients
4. Guide nutrients to targets
5. From blood brain barrier

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CNS Neuroglial Cell that...
-Like astrocytes but smaller

Oligodendrocytes

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Functions of Oligodendrocytes (2)

1. Form myelin in CNS
-Sequester debris

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CNS Neuroglial Cell that...
-Smallest and least common
-Derived from myeloid cells

Microglia

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Functions of Mircoglia (3)

1. Help support neurons
2. Phagocytosis
3. Increase in number during injury or disease

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CNS Neuroglial Cell that...
-Columnar/cuboidal
-Microvilli on luminal surface
-Joined by gap junctions

Ependymal

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Functions of Ependymal (3)

1. Help produce cerebrospinal fluid
2. Form porous layer
3. Monitor CSF composition

60

PNS Neuroglial Cell that...
-Associated with soma
-Assist with exchange of nutrients
-Isolates neuron from extraneous stimuli

Satellite

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PNS Neuroglial Cell that...
-Produce myelin in PNS
-Encloses axons of longer peripheral nerves

Schwann Cells

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Functions of Schwann cells... (3)

1. Support neurons
2. Prevent contact
3. Myelinate large PNS axons

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Characteristics of unmyelinated axons... (3)

1. Appear gray
2. Many axons associate with a single schwann cell
3. CNS- no glial cells

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Characteristics of Myelinated Axons... (3)

1. Appear white
2. CNS- Oligodendrocytes myelinate part of several axons
3. PNS- Schwann cell myelinates part of one axon

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Myelin Structure (3)

1. Myelin
2. Neurilemma
3. Nodes of Ranvier

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Part of myelin structure that...
-Plasma membrane of Schwann cell wrapped around an axon

Myelin

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Part of myelin structure that...
-Part of the Schwann cell that contains the cytoplasm

Neurilemma

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Part of myelin structure that...
-Gaps in myelin sheath

Nodes of Ranvier

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Process that starts at week 14 and completed by age 2 or 3 years

Myelination process

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Myelin Functions (2)

1. Isolate Axons
2. Increase rate of action potential

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Regeneration of Nerve fibers in PNS

-Can regenerate a fraction of the axons
-Schwann cells participate in process
-Called Wallerian degeneration

72

Process of Nerve Fiber Regeneration (9)

1. Injury separates axon from the cell body (distal portion of the axon will deteriorate along with myelin sheath
2. Macrophages clean up
3. Some Schwann cells remain and reproduce
4. Get thin basement membrane & layer of CT around Schwann cells
5. Forms hollow tube leading to original connection of axon
6. Proximal end sprouts
7. Sprout may grow into tube
8. Remaining Schwann cells produce new myelin around growing axon
9. New axon grows 3-4 mm/day

73

Characteristics of repair in CNS (5)

1. More limited
2. Degeneration occurs after injury
3. Oligodendrocytes do not proliferate
4. Proximal end sprouts but has no tube that follows
5. Astrocytes produce scar tissue and chemicals blocking regrowth

74

4 Factors of Nerve Impulse

1. Irritability
2. Excitability
3. Action Potential
4. Nerve Impulse

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Ability to respond to stimuli

Irritability

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Ability to transmit an impulse

Excitability

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An electrical impulse changing the permeability of a membrane

Action potential

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Action potential moving down an axon

Nerve Impulse

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Impulse travels faster when... (2)

1. Axon is myelinated
2. Has a larger diameter

80

Functions of synapse

Control and transmission point

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Synapse is the site of communication between... (4)

1. Sensory structure and neuron
2. Neuron & effector
3. 2 neurons
4. Any 2 cells with gap junctions

82

2 types of Synapses

1. Electrical
2. Chemical

83

Characteristics of Electrical Synapse

- Gap functions cause the exchange of charged ions between 2 cells

84

Example of Electrical Synapse

Intercalated disks in cardiac muscle

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Characteristics of Chemical Synapse

-Chemicals are released by one cell and travel to another

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Examples of Chemical Synapses (2)

1. Neuromuscular Junction
2. Neuron-neuron contact

87

How chemical synapses work

1. Synaptic vesicles house neurotransmitter
2. Only exist in the presynaptic cell
3. Release neurotransmitter into the synaptic cleft
4. Receptors on post-synaptic membrane register the neurotransmitter
5. Proliferates AP from one cell to the next
6. Communication in one direction only

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-Receive impulses from afferent fibers (input)
- Impulses carried away on efferent neurons (output)
-Afferent fibers can branch many times as they enter a pool

Neuronal Pool

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Types of Neuronal Pools (5)

1. Convergence
2. Divergence
3. Serial Processing
4. Parallel Processing
5. Reverberation

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Type of Neuronal Pool that...
-One neuron to another in a series

Serial Processing

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Type of Neuronal Pool that...
-When impulse leaves a pool it may spread out into several output fibers
-Allows impulse to be amplified

Divergence

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Type of Neuronal Pool that...
-Single nerve in pool may receive impulses from 2 or more incoming fibers
-if lead to the same nerve, they are said to converge
-Allows summation o impulses from different sources

Convergence

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Type of Neuronal Pool that...
-Processing information from several neurons at once

Parallel Processing

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Type of Neuronal Pool that...
-Positive feedback continues activity of circuit

Reverberation

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-Process in which one neuron may receive either excitatory & inhibitory stimuli from multiple neurons
-The net effect of all this input results in a net charge and if this charge is positive enough it will result in an AP

Facilitation

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The point where an action potential can be produced is...

Threshold

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-If a neuron is excited but still below threshold
-No impulse but the nerve is more excitable to next impulse
-This nerve is said to be....

Facilitated

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Central Nervous System Structures... (3)

1. Nuclei
2. Center
3. Tracts

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Collection of neuron cell bodies

Nuclei

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Collection of neuron cell bodies working together

Center

101

Bundles of axons

Tracts

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Peripheral Nervous System structures

1. Ganglia
2. Nerves

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Collection of cell bodies (PNS)

Ganglia

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Bundles of axons (PNS)

Nerves