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Anatomy & Physiology 200 > Nervous Tissue > Flashcards

Flashcards in Nervous Tissue Deck (126):
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What structures protect the brain?

Cerebrospinal fluid Meninges (three layers: pia, arachnoid and dura)

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Outer cortex

Aka cerebrum or neocortex. Contains frontal, temporal, occipital and parietal lobes

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What is the frontal lobe primarily responsible for?

Short and long term memory, personality, intelligence, music, artistry

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What is the parietal lobe primarily responsible for?

Reading, writing, comprehension, analytical reasoning.

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What are the temporal lobes primarily responsible for?

Auditory functions

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What are the occipital lobes primarily responsible for?

Vision

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What are the parts of the brain stem?

Pons Medulla oblongata Midbrain

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Pons

Part of the brain stem. Relay centre for signals.

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Medulla oblongata

Centre for autonomic control and vital functions (breathing, HR, BP etc)

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Midbrain

Contains important nerve tracts and the substantia nigra.

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Substantia nigra

In midbrain. Contains neurons that produce dopamine Damaged in Parkinson's.

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Dienchephalon

Contains: Thalamus Hypothalamus Epithalamus

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Thalamus

In diencephalon Relay station for signals

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Hypothalamus

In diencephalon Centre for autonomic control. Non-vital functions (controls via hormone production)

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Epithalamus

In diencephalon Centre for sleep and circadian rhythms

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Cerebellum

Cauliflower Located posterior-inferior. Coordination of sensory input and motor output. Ensures that what's being ordered is being done. Allows for smooth, refined, synchronized movements.

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Three types if nerve cells (by function)

Sensory (afferent) -- input Associative -- integrative Somatic (efferent) -- output

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Cranial nerves

12 specialized nerves that exit out base if brain

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Ganglia

Small masses if nervous tissue found outside of the brain and spinal cord.

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Nuclei

Collection of nerve cell bodies within the brain and spinal cord

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Ganglion cyst

Collection of fluid, built up around a soft tissue structure. Idiopathic. Tend to form around tendons or joints in wrists, hands or feet.

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Enteric plexus

Bundles of nerves that regulate digestive organs Consists if nerve riots that exit the spinal cord and innervate GI tract and structures.

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Spinal cord

Encased in vertebral column Houses approximately 100 million neurons 31 pairs of spinal nerves that exit the spinal cord at each and every level (bilaterally).

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Functions of the nervous system

Sensory -- afferent Integrative -- interneuron or association neuron -- simple or complex reflexes -- most complex and intricate Motor -- efferent. -- can be sympathetic, parasympathetic, voluntary or involuntary.

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Three steps of a simple reflex

1. sensory neurons detect 2. Action potentials sent to brain and/or spinal cord via Afferent neurons. CNS determines what is to be done (Integration) 3. Command sent via Efferent neurons

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Three steps of a complex reflex

1. Sensory neurons detect. Signal sent to brain via afferent neurons 2 Brain registers input and fires signal to other parts of brain to integrate, analyze and respond. Decision making by committee 3. Command sent via efferent neurons

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Central Nervous System

CNS a. Brain (any tissue above the foramen magnum) and encased within the cranial cavity + b. Spinal Cord (foramen magnum to sacrum -- located within vertebral column)

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Peripheral Nervous System

PNS All nervous tissue outside of the CNS Subdivided into Somatic, Autonomic and Enteric

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Somatic Nervous System

SNS Voluntary Includes: Sensory nerves from special senses Motor neurons to conduct from CNS to skeletal muscle

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Autonomic Nervous System

ANS Involuntary Includes: Sensory receptors from internal organs Motor neurone from CNS to smooth muscles, internal organs Further divided into Sympathetic and Parasympathetic systems

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Sympathetic Nervous System

Part of autonomic nervous system Responsible for fight or flight

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Parasympathetics Nervous System

Part of ANS Responsible for rest & digest, feed & breed Responsible for normalizing and bringing body back to homeostasis after activity

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Dual Innervation

Seen in ANS. One organ is innervated by both sympathetic and parasympathetic neurons

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Enteric Nervous System

Involuntary ENS Only involved with GI tract Sensory and somatic/motor pathways

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Two types of nervous tissue

Neurons Neuroglia

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Nerve impulse

An action potential which involves a neuron

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Speed of nerve impulse

1/1000 of a second

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Dendrites

Finger-like projections of a neuron which receive input

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Axons

The long, thin, cylindrical projection of a neuron. The shaft.

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Axon hillock

Where axon meets neuronal body

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Trigger zone

Area of axon hillock where action potentials are triggered

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Axoplasm

cytoplasm of axon

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Axolemma

Membrane of axon

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Telodendria

AKA the Axon Terminal End of the axon, often bulge out into synaptic end bulb

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Initial segment

Portion of axon closest to axon hillock

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Axon collaterals

Branches off the axon that contribute to other circuits

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Perikayon

Nerve cell body, or soma Contains the nucleus and organelles

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Nissl bodies

Bundles of rough ER which produce proteins specific to neurons

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Synapse

Gap where two or more neurone meet

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Neuroglia cells

Main role is to support, nourish and protect neurons

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Glioma

Brain tumour arising out of glial cells

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What are the neuroglial cells of the CNS?

1. astrocytes 2. oliogodenrocytes 3. microglia 4. ependyma

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Astrocyte

CNS neuroglia Helps form the blood brain barrier Star shaped

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Blood brain barrier

Tightly sealed lining that helps maintain the selective permeability of capillaries in the nervous system to help prevent leakage or attack.

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Oligodendrocyte

Forms the myelin sheath around CNS axons (similar to Schwann cells of PNS)

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Microglia

Phagocytes of the nervous system. Akin to macrophages

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Ependymal

Line inside of spinal canal and ventricles of the brain. Main role is production and circulation of cerebral spinal fluid

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What are the neuroglial cells of the PNS?

Schwann cells Satellite cells

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Schwann cells

Form myelin sheath of the PNS

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Satellite cells (neuro)

Supports and protects neuronal cell bodies in the PNS Help with dendritic and axon repair Helps regulate substances between neuron and interstitial fluid

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Unipolar neuron

Two projections of axons, one sensory and one ending in synaptic bulbs that continue onto CNS

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Bipolar neuron

One axon and one dendrite Can be found in retina, olfactory and auditory nerves

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Multipolar neuron

Most common in CNS Has one axon and multiple dendrites

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Purkinje neuron

Found in cerebellum. Very luscious looking dendrites

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Pyramidal neuron

Found only in cerebral cortex. Pyramidal neuronal cell body

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Gray matter

Nervous tissue that contains: cell bodies dendrites axon terminal unmyelinated axons neuroglial cells Superficial in brain (cortex) and deep in spinal cord

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White matter

The portion of nervous tissue that contains myelinated axons. Deep in brain, superficial in spinal cord.

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Myelination

Covering and insulation of axons by neuroglial cells (oligodendrocytes and Schwann cells) that allows for increased rate and efficiency of impulse transmission.

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Neurolemma

The sheath of the oligodendrocyte or Schwann cell (like sarcolemma)

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Nodes of Ranvier

Gaps between myelin sheaths between which the action potential jumps.

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Multiple Sclerosis

Progressive, degenerative, autoimmune condition of the myelin sheaths of the CNS. Sheaths replaced by fibrous plaque (sclerotic) Progressive weakness, double vision, fatigue, parasthesias, and other neurological deficits.

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What are the two types of motor neuron?

Upper motor neuron (UMN) Lower motor neuron CNS --> UMN --> LMN --> muscle/gland/organ

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Membrane Potential

The electrical voltage difference across the cell membrane. Means the cell is polarized

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Resting membrane potential

-70mV

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Sodium Potassium Pump

Pumps 3 Na+ out for every 2 K+ in to help establish resting membrane potential.

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Electrogenic

Producing a change in the electrical potential of a cell. Na+, K+, Sodium-postassium pump

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What are the main ions involved in nerve impulses?

Sodium (Na+) -- concentrated higher outside cell -- most abundant cation in extracellular fluid Potassium (K+) -- concentrated higher inside the cell -- most abundant cation in intracellular fluid Chloride (Cl-) -- concentrated outside the cell -- most abundant anion found in extracellular fluid Also: Phosphate (PO4-) large, mostly inside the cell Calcium (Ca+) -- concentrated outside cell -- most abundant (cation) mineral inside the body

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Four kinds of ion channels in the nerve cell

Leakage Voltage gated Ligand gated Mechanically gated

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Leakage gated channels

Alternate between open and closed Most membranes have more K+ channels than Na+, so more permeable to K+ Concentrated ate axon hillock and axon membranes, although present everywhere on membrane Plays key role in Resting potential

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Voltage gated channels

Open and close in response to a change in membrane potential. Play key role in Action potential Concentrated at axon and axon hillocks

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Ligand gated channels

"Lock & key" Open and close in response to chemical, hormonal or ionic stimuli and/or NT signal. Involved in graded potential Concentrated at axon terminals, and dendrites and cell bodies

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Mechanically gated channels

Open and close in response to mechanical stimulus -- i.e. vibrations, pressure, stretch. Involved in graded potentials Concentrated at axon terminals, dendrites and cell bodies.

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What are the two types of potentials

Graded and action

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Graded Potential

Small deviation from resting potential (of -70mV) Can be depolarizing (less neg.) or hyper polarizing (more neg.) Involve ligand gated and mechanically gated channels No conduction and therefore localized Begin at dendrites and cell bodies No refractory period and thus subject to summation

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Two types of summation

Spatial Temporal

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Spatial Summation

At trigger zone, many synapses summated together at the same time

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Temporal Summation

Repetitive successive summation

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Action Potential

Involve voltage gated and leakage channels Have refractory period and therefore not affected by summation ==> All or Nothing Arises from trigger zones at axon hillock

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What is the sequence of an Action Potential

Resting (voltage gated Na+ channels resting; voltage gated K+ channels closed) Stimulus causes depolarization Once depolarization reaches threshold (-55 mV), Na+ channels open --> Depolarization Phase Rush of Na + into cell changes potential from -55 to +30 mV Voltage-gated K+ channels open; Na+ channels inactivating Exodus of K+ out of cell --> Repolarization +30 to -90 mV Voltage-gated K+ channels close. Resting potential of -70mV achieved

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How much of what does the sodium potassium pump pump?

3Na+ Out, 2K+ in. Makes cell more negative

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All or Nothing law

When depolarization reaches threshold, AP is generated. AP is always the same size and amplitude, regardless.

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Threshold

Minimum amount of voltage needed to generate an action potential (-55mV in a neuron)

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Refractory Period

The time frame following an AP in which no other AP can be generated.

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2 types of refractory periods

a) Absolute. (no how no way. Coincides with the time Na+ channels open -- Depolarization) b) Relative. (try harder. Coincides with the time Na+ channels closed but K+ channels open. Repolarization)

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What are the two categories of neurotransmitters?

Small molecule neurotransmitters Neuropeptides

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What are the categories of Small Molecule Neurotransmitters

1. Acetylcholine 2. Amino Acids 3. Catecholamines (Biogenic Amines) 4. Serotonin 5. Nitric Oxide

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Acetylcholine

Excitatory NT at NMJ. Propogates AP further.

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Amino Acid (small molecule neurotransmitters)

Excitatory -- help lower threshold for activation 1. Glutamate (glutamic acid) 2. Aspartate (aspartic acid) Inhibatory -- blocks/inhibits propagation of AP by increasing threshold for activation 3. GABA (gamma amino butyric acid) 4. Glycine -- inhibitory effects at NMJ

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What are all catecholamines derived from?

The amino acid Tyrosine

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Catecholamines

AKA biogenic amines 1. Epinephrine (E) -- released by adrenals/ arousal, energy and muscle tone. AKA adrenaline 2. Norepinephrine (NE) -- mood and arousal. AKA noradrenaline 3. Dopamine (DA) -- mood and pleasure.

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Relationship between Dopamine and Parkinson's and Schizophrenia

Parkinson's: death of substantial nigra --> not enough DA Schizophrenia: too much DA

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Serotonin

5-HTP Hydroxytryptamine Sensory perception, appetite, mood, sleep regulation

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Nitric Oxide

NO (not N2O) Both inhibitory and excitatory depending on receptors involved. Also causes vasodilation.

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Membrane potential is created by:

1. Difference between 3 sodium out and 2 potassium in. 2. Presence of large negative proteins inside cell. (Made partly of COOH- which is really negative) 3. Lots of Phosphate floating around cytosol (waiting to make ATP)

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Two types of nerve impulses

Continuous Saltatory

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Continuous nerve impulse

No myelin sheath Nerve impulse travels along membrane by opening and closing of adjacent ion channels.

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Saltatory nerve impulse.

Nerve impulses jump from node of ranvier to node of ranvier along myelinated axon. Speedy fast.

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Three types of nerve axons

A B C

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A Nerve Fibres

100% myelinated. Super fast. 130 m/sec Sensory nerves and motor neurons of skeletal muscle Thickest

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B Nerve Fibres

100% myelinated 15 m/sec ANS and visceral organs.

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C Fibre Nerves

Not myelinated 2 m/sec Reproductive, excretory, digestive Long refractory period

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Two types of synaptic junctions

Chemical Electrical

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Electrical synapses

Use gap junctions Found in ANS, smooth muscle and cardiac muscles. Signal passes through connexon protein Fast communication. Synchronization of signals n

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Chemical synapses

AP arrives at presynaptic neuron Voltage gated Ca+ channels open. Ca+ flows inward, stimulates exocytosis of NT. NT flows across synapse and attaches to ligand gates channels. Inhibits or excites.

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Neuropeptides

Enkephalins -- blocks pain Endorphins -- blocks pain Substance P -- enhance perception of pain

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Types of neural circuits

Simple series Divergence Convergence Reverberating Parallel after discharge.

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Simple series circuit

One neuron stimulates another, which in turn stimulates another. Unusual.

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Divergent neural circuits

One neuron stimulates a few others, each of which stimulates multiple others.

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Convergent neural circuits

Multiple neurons stimulate one single neuron. Spatial Summarize effect.

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Reverberating neural circuit

Similar to simple circuit, but neurons reverberate backwards to stimulate earlier neurons. Extended, coordinated movements like breathing.

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Parallel after discharge neural circuit

Single presynaptic cell stimulate multiple neurons, which all synapse back to a common post synaptic cell.

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Neural plasticity

Capability to adapt and change

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Neurogenesis

Birth and growth of new neurons from undifferentiated stem cells.

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Epidermal growth factor (EGF)

Recently discovered chemical that can trigger mitosis in neuronal cells

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Chromatolysis

(de)granulation of nissl bodies within the neuron as part of repair process

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Wallerian degeneration

Degeneration if distal portion of axon and myelin sheath as part if repair.