Neural Tissue for Final EXAM Flashcards by Enide Clerizier

what are the subdivisons of the nervous system

central nervous system
peripheral nervous system

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what organs make up the central nervous system (CNS)

brain
spinal cord

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what are the subdivisions of the peripheral nervous system

sensory divison
motor divison

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what does the sensory division do?

carries signals from receptors to CNS

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what are the subdivisions of the sensory division

Visceral sensory division
Somatic sensory division
Special senses

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what does the Visceral sensory division do?

carries signals from the viscera (heart, lungs, stomach, and urinary bladder)

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what does somatic sensory division do?

carries signals from receptors in the skin, muscles, bones, and joints

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what are the subdivisions of the motor division

Visceral motor division
Somatic motor division

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what does motor division do

carries signals from CNS to effectors (glands and muscles that carry out the body’s response).

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what does Somatic motor division do?

carries signals to skeletal muscles leading to muscular contraction and somatic reflexes (involuntary muscle contractions).

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what does visceral motor division do?

carries signals to glands, cardiac and smooth muscle. Its involuntary responses are visceral reflexes.

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what is another name for visceral motor division

autonomic nervous system

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what are the subdivisions of the visceral motor division

Sympathetic division
Parasympathetic division

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what is the responsibility of the Sympathetic division

is responsible for the fight or flight response. It tends to arouse the body for action. It increases the heart rate, heart contractility, respiratory rate, but inhibits digestive and urinary systems.

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what is the responsibility of the Parasympathetic division

is responsible for the rest and digest response. It slows heart rate, breathing but stimulates digestive and urinary systems.

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What makes up the Peripheral nervous system (PNS)

the entire nervous system except the brain and spinal cord
(nerves and ganglia)

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carries signals from receptors to CNS

Sensory (afferent) division

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what are the two components of the autonomic nervous system

Sympathetic nervous system
Parasympathetic nervous system

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what are the cells of the nervous tissue

neurons
neuroglia

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cells used for communication by the nervous tissue

Neurons

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Supporting cells of the nervous tissue

Neuroglia

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what are the three classes of neurons

Sensory neurons
Interneurons
Motor neurons

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Detect stimuli and transmit information about them toward the CNS

Sensory neurons

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Receive signals from many neurons, integrates, processes and determines the appropriate response. Lie entirely within CNS connecting motor and sensory pathways (about 90% of all neurons).

Interneurons

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Send signals out to muscles and gland cells (the effectors).

Motor (efferent) neurons

contains the nucleus and other structures common to living cells

soma

Multiple branches that come off the soma responsible for receiving signals from other neurons

Dendrites

the elongated portion of the neuron located in the center of the cell between the soma and terminals

axon

the region of a neuron that controls the initiation of an electrical impulse based on the inputs from other neurons or the environment

axon hillock

swellings that form contact points (synapses) with other cell, contains synaptic vesicles full of neurotransmitter

Axon terminals

what are the neuroglia of the central nervous system (CNS)

Ependymal cells Astrocytes Microglia Oligodendrocyte

Cuboidal epithelium with cilia on apical surface that line internal cavities of the brain. They secrete and circulate cerebrospinal fluid (CSF).

Ependymal cells

Most abundant glia in CNS. Star shaped cells that cover brain surface and most non synaptic regions of neurons.

Astrocytes

Macrophages that develop from white blood cells (monocytes) and become concentrated in areas of damage.

Microglia

Octopus like cells with arm-like processes that wrap around nerve fibers forming myelin sheaths in CNS that speed signal conduction.

Oligodendrocytes

what are the neuroglia of the peripheral nervous system

Schwann cells Satellite cells

Wind around the axon and form myelin sheaths. Assist in regeneration of damaged fibers.

Schwann cells

Surround the somas of PNS neurons inside ganglia. They provide electrical insulation and regulate the chemical environment.

Satellite cells

Consists of the plasma membrane of glial cells, made up of 20% protein and 80% lipid.

myelin

what are the function of myelin

Provides insulation around the axon and increases action potential conduction velocity.

what is the myelin formed by in the CNS

Oligodendrocytes

what is the myelin formed by in the PNS

Schwann cells

what are the factors that can affect the speed of conduction

Diameter of the fiber Presence of myelin

how does the diameter affect conduction

Larger axons have more surface area and conduct signals more rapidly.

how does the Presence or absence of myelin Presence or absence of myelin

Myelin speeds signal conduction. Many neurons have unmyelinated axons and they have slower signal conduction compared to myelinated axons.

what is the resting membrane potential of neurons

-70 mV

how is the resting membrane potential of neurons made

Caused by separation of charge (ions) across the cell membrane with the inside of membrane negative relative to outside

- Moves 3 Na+ out of the cell and brings 2 K+ into the cell using 1 ATP - Helps create and maintain the sodium and potassium ion concentration gradients across the membrane.

Na+/K+ pump

At normal resting membrane potential, an electrical gradient opposes the chemical gradient for potassium ions (K+). The net electrochemical gradient tends to force potassium ions out of the cell.

Potassium Ion Gradients

At the normal resting membrane potential, chemical and electrical gradients combine to drive sodium ions (Na+) into the cell.

Sodium Ion Gradients

Change in membrane potential at and nearby point of stimulation may be a depolarization or a hyperpolarization.

Local potential

Rapid up-and-down shift in membrane potential that can travel a long distance down an axon. Always a rapid depolarization followed by repolarization and hyperpolarization.

Action potential

Two types of change in membrane potential:

Local potential Action potential

shift in the voltage across the membrane to a less negative value

Depolarization

shift in the voltage across the membrane to a more negative value.

Hyperpolarization

label this

Period of resistance to stimulation during an action potential and for a few milliseconds after when it is difficult or impossible to initiate another action potential.

Refractory period

what are the Refractory period two phases

relative refractory period absolute refractory period.

A stronger stimulus than usual is needed to trigger a new AP. During hyperpolarization, a larger depolarization (local potential) is required to reach threshold for another action potential to be triggered

relative refractory period

No stimulus of any strength will trigger another action potential due to inactivation of voltage-gated Na+ channels.

absolute refractory period.

occurs in unmyelinated axons that have voltage-gated channels along their entire length.

continuous propagation

in myelinated axons where electrical signal seems to jump from node to node. Moves faster through “insulated” segments covered with myelin and slows down when it reaches the bare axon of the nodes.

saltatory propagation

a small gap at the end of a neuron that allows a signal to pass from one neuron to the next.

Synapses

which releases neurotransmitter and transmits the signal toward a synapse

Presynaptic neuron

responds to neurotransmitter

postsynaptic neuron

- Axon terminal of presynaptic neuron contains synaptic vesicles containing neurotransmitter. - Postsynaptic neuron membrane contains neurotransmitter receptors. The neurotransmitter receptors are ligand-gated ion gates that open when neurotransmitters bind to them.

chemical synapse

what are the events that lead to the cessation of the signal

Degradation Reuptake Diffusion

how does the cessation of the signal occur

Presynaptic cell stops releasing neurotransmitter

Enzyme in synaptic cleft breaks down neurotransmitter

Degradation

Neurotransmitter (or its breakdown products) reabsorbed into axon terminal

Reuptake

Neurotransmitter (or its breakdown products) simply diffuse away from synapse into nearby ECF

Diffusion

are chemicals secreted by neurons that have long term modulatory effects on groups of neurons

Neuromodulators

- is a simple neuromodulator - Gas that enters postsynaptic cells and activates second messenger pathways

Nitric oxide (NO)

is a voltage change from Resting membrane potential towards threshold and usually results from Na+ flowing into the cell

Excitatory Postsynaptic Potential (EPSP)

occurs when the cell's voltage becomes more negative than it is at rest

Inhibitory Postsynaptic Potential (IPSP)

is the process of adding up postsynaptic potentials and responding to their net effect which occurs in the trigger zone.

Summation

what are the two types of Summation

Temporal summation Spatial summation

Occurs when a single synapse generates EPSPs so quickly that each is generated before the previous one fades. Allows EPSPs to add up over time to a threshold voltage that triggers an action potential.

Temporal summation

Occurs when EPSPs from several different synapses add up to threshold at an axon hillock. Simultaneous input from multiple presynaptic neurons are required for the postsynaptic neuron to fire.

Spatial summation

occurs when one presynaptic neuron enhances another one

Presynaptic facilitation

occurs when one presynaptic neuron suppresses another one

Presynaptic inhibition

ability of synapses to change

Synaptic plasticity

process of making transmission easier

Synaptic potentiation

may last a lifetime and can hold more information than short term memory.

Long term memory (LTM)

memories you can put into words

Explicit