Quiz 5 Nervous System pt 1 Flashcards Preview

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Flashcards in Quiz 5 Nervous System pt 1 Deck (26):

Central Nervous System involves the:


Spinal Cord


Peripheral Nervous System involves the:


- Afferent Neurons

- Efferent Neurons

   - Sympathetic Autonomic Control

   - Parasympathetic Autonomic Control


Afferent Neurons

sensory neurons

- sense stimulus and send info about the stimulus to CNS e.g. smell, light


Efferent Neurons

motor neurons

- carry signals away from CNS, initiating action


Somatic Motor Neurons

(Efferent Neurons)

skeletal muscle


Autonomic Motor Neurons

(Efferent Neurons)

cardiac muscle (heart), glands, smooth muscles in the body; "hollow tubes"


Sympathetic Nervous System

(Autonomic Motor Neurons)


e.g. blood pressure, sweat, digestion stops


Parasympathetic Nervous System

(Autonomic Motor Neurons)


- counteracts effects of sympathetic nervous system (starts digestion again, lowers BP)

- optimal level of functioning exists in the parasympathetic nervous system


Enteric Nervous System

bowels, small intestine



- is a nerve cell, fully differentiated, and capable of transmitting a nervous (electrical) impulse


Nervous Tissue

- composed of neurons

- therefore our brain, spinal cord, and nerves are all cariations of neuronal arrangement


3 basic structures of a neuron

Cell Body (Soma): interpretation and protein synthesis; also contains nucleus

Dendrites: branched projections acting to propogate electrochemical stimulation received from other neural cells to the cell body (soma).

Axon: conducts/transmits electrical impulses away from the soma to different neurons, glands, or muscles; "nerve fibers"


White Matter/Grey Matter

White Matter: myelinated axon

Grey matter: unmyelinated axon, dendrite, or soma


Neurons and signal direction

A neuron is only capable of carrying a signal in one direction along its axon, thus the distinction between sensory and motor neurons. 

(A bundle of axons w/in CNS is referred to as a tract; a bundle of axons outside the CNS is referred to as a nerve)




- the junction between the axon terminal and there the axons lead (muscle, other neuron, gland)

- transmission of a signal across the synapse may be electric, but is more commonly chemical (involving a neurotransmitter)


Neuronal Membrane

(Channels and Pumps)

the membrane of a neuron is impermeable to most ions such as Na+, K+, Cl-, and Ca+, however, many distint channels and gates exist for their passage, but most notably:

Voltage Gated Channels: "Na+ stay high, K+ stay low"?

Na/K ATPase Pump: re-establish resting membrane (push Na+ out, K+ in)

Slow leak ion channels: K+ leaks out slowly (but faster than Na+)-- creates + outside and - inside


Resting Membrane Potential

A membrane at rest has a higher concentration of sodium on the outside and potassium on the inside of the cell.  Potassium slowly leaks out creating a negative charge on the inside of the resting membrane; measured in millivolts


Action Potential

- a rapid change in membrane potential and is the mechanism by which a nerve signal is transmitted

- muscle cells, cardiac cells, and neural cells all support an action potential though slight variations exist among the differing tissue types

- the ability to support an action potential is characterized by the term 'excitable' tissue


DEPOLARIZATION STAGE (Na+ channels open, flooding inside the cell)

REPOLARIZATION STAGE (K+ channels open, flood out of the cell)  ATP pump kicks in?


Saltatory Conduction

- occurs along the myelinated axons allowing for a more rapid and energy conserving signal transmission

- able to "skip" all the gates... jumps from one node to the next



- are chemicals released into the synapse once an action potential reaches the end of the axon

- its release is calcium dependent, and its action is determined by the postsynaptic receptor

- the resulting action may last milliseconds or days and include:

-- opening or closing of membrane channels

-- enzyme activation on the postsynaptic structure

-- altered cell metabolism

-- altered gene expression


Two Major classes of neurotransmitters exist:

Large molecule NT: neuropeptides/neurohormones

insulin, growth hormone, prolactin, melanocyte stimulating hormone

Small molecule NT: have a more rapid and shorter duration of action

     - dopamine, seratonin, histamine, acetylcholine, norepinephrine


The obvious variable in a neuron's ability to carry a signal is:

Alterations in Neuronal Transmission

Ion concentration


- neurotransmitter deficiencies, demyelination, damage to the neuron


Alterations in Neuronal Transmission cont...

neuroregeneration is possible through axonal regrowth assuming the cell body of that neuron is in tact

- also, extracellular changes of endogenous and exogenous matter must be considered with respect to ingestion, metabolism, and excretion ability

(e.g. a drop in extracellular pH will result in increased excitability of a neuron while a rise in pH will result in the opposite effect)

- Low oxygen levels may decrease synaptic activity



Alterations in Neuronal Transmission Cont

(synaptic fatigue and synaptic facilitation)

Synaptic Fatigue: ​occurs if stimulation is too rapidly repeated 

Synaptic Facilitation: occurs if repetitive stimulation is followed by a brief period of rest, then re-stimulation



- masses of soma and dendrites in a close proximity; "clusters of cell bodies" (the term plexus is used to describe groupings of various ganglia)


Two Ganglia of note:

Dorsal Root Ganglia (spinal ganglia) of the sensory neurons

Autonomic Ganglia of the autonomic motor neurons

  • sympathetic ganglia are paraspinal
  • parasympathetic ganglia are close to their effector organ

- Somatic motor neuron cell bodies are located within the spinal cord at various levels, thus no ganglia