9 Nervous Tissue Flashcards
The nervous system includes what 7 features?
The brain Cranial nerves Spinal cord Spinal nerves Ganglia Enteric plexuses Sensory receptors
What are the basic parts of a neuron?
Several dendrites, a cell body, and a single axon.
A multipolar neuron had __ processes extending from the cell body, a bipolar neuron has __, and a unipolar neuron has __.
Many; two; one
The electrical signals produced by neurons and muscle fibres rely on ion channels such as:
Leak channels and voltage-gated channels
The resting membrane potential is due to a small buildup of __ charged ions, mainly organic phosphates and proteins, in the cytosol just inside the membrane and an equal buildup of __ charged ions, mainly sodium ions, in the extracellular fluid just outside the membrane.
Negatively; positively
An action potential consists of __ and __ phases.
Depolarizing and repolarizing
Unmyelinated axons exhibit __ conduction, and myelinated axons exhibit __ conduction.
Continuous; saltatory
What are dendrites?
Dendrites are extensions of the cell body that transmit impulses to the cell body.
What are ependymal cells?
Epithelial cells (often ciliated) that line the ventricles of the brain. They produce cerebrospinal fluid (CSF).
Describe the structure of a myelin sheath.
Consists of many layers of phospholipid membrane that belong to the Schwann cells. This sheath wraps around the axons on the myelinated neurons.
What is a threshold stimulus?
Is a stimulus that causes the membrane of a neuron to depolarize to a critical level (-55mV) to generate an action potential.
Define the term ganglia.
Are clusters of nerve cell bodies outside the CNS.
What is the function of the afferent neurons?
To conduct impulses from the sensory cells to the CNS.
What is a neurotransmitter?
Is a chemical released by a presynaptic neuron from the purpose of stimulating or inhibiting the postsynaptic neuron.
What is the function of the microglia?
They act as phagocytic cells.
What is the advantage of saltatory conduction?
Is very fast and requires less energy expenditure of the sodium-potassium pump.
Name the 2 subdivisions of the autonomic nervous system:
Sympathetic and parasympathetic nervous system
What is the refractory period?
Is the period of time following an initial stimulus during which a neuron cannot be stimulated to conduct a second impulse.
Identify the functions of the nervous system.
Sensory: senses changes within the body and the environment.
Motor: initiates muscle movement or glandular secretion.
Integrative: interprets sensory information and determines the appropriate motor response.
What is the role of the sodium potassium pump?
It actively carries sodium out of the cell and potassium into the cell. It is powered by ATP.
How does a neuron become depolarized?
The rapid influx of sodium ions through the nerve cell membrane causes depolarization.
Define white and grey matter.
White matter: groupings of the myelinated processes of many neurons.
Grey matter: contains nerve cell bodies, dendrites, and axon terminals of unmyelinated axons and neuroglia.
Why does the synaptic conduction of an impulse occur only in one direction?
Transmission must be unidirectional because neurotransmitters are released only from presynaptic terminals, and because only postsynaptic membranes have appropriate neurotransmitter receptors.
What is the meaning of the term resting membrane potential?
Is the potential difference that exists across a nerve cell membrane when it is not conducting an impulse, usually about -70mV.
Which neuroglia produce myelin in the CNS?
Oligodendrocytes
Which of the gated ion channels opens to a change in membrane potential?
Voltage
The most important factors that determine the speed of impulse propagation are:
Fibre diameter and and the presence or absence of the myelin sheath.
