Nerve Cells and Nerve Impulses Flashcards
Cells that receive information and transmit it to other cells
Neurons
The average adult human brain contains approximately _____________ neurons.
86 billion
Who are recognized to be the founders of neuroscience?
Charles Sherrington & Santiago Ramon y Cajal
The cerebral cortex has around _______ neurons.
16 billion
The cerebellum has at least _______ neurons.
69 billion
The spinal cord has around _______ neurons.
1 billion
What did Cajal’s research on nerve cells demonstrate?
Nerve cells remain separate instead of merging into one another
The surface of a cell and the structure that separated the inside of the cell from the outside environment
Cell membrane
Most chemicals cannot cross the membrane, but protein channels in the membrane permit _______________.
Water, oxygen, sodium, potassium, calcium, chloride, and other chemicals
Cell structure that contains the chromosomes
Nucleus
Cell structure that performs metabolic activities, providing the energy that the cell uses for all activities
Mitochondrion
Cell structure that have genes separate from those in the nucleus of a cell
Mitochondrion
Sites within a cell that synthesize new protein molecules
Ribosomes
Building materials of a cell that facilitate chemical reactions
Proteins
Where can ribosomes be found?
Floating freely within the cell or attached to the endoplasmic reticulum
A network of thin tubes that transport newly synthesized proteins to other locations
Endoplasmic reticulum
The most distinctive feature of a neuron
Shape
Describe a motor neuron
Soma in the spinal cord
Receives excitation through its dendrites
Conducts impulses along its axon to a muscle
Describe a sensory neuron
Soma located on a stalk off the main trunk
Specialized at one end to be highly sensitive to a particular type of stimulation
Conducts touch information from the skin to the spinal cord
Branching fibers that get narrower near their ends
Dendrites
The term dendrite comes from the Greek root word ______
Tree
Covers the dendrite’s surface where it receives information from other neurons
Synaptic receptors
The greater the surface area of a dendrite, ___________
The more information it can receive
Short outgrowths located on dendrites that increase the surface area available for synapses
Dendritic spines
Cell structure that contains the nucleus, ribosomes and mitochondria
Cell body or soma
Soma is the Greek word for _____
Body
Cell bodies of neurons range in diameter from ____________
0.005 mm to 0.1 mm in vertebrates
Up to a millimeter in invertebrates
A thin fiber of constant diameter which conveys an impulse toward other neurons, an organ, or a muscle
Axon
The term axon comes from the Greek word _______
Axis
Axons can be ____________ in length
More than a meter
Insulating material that covers vertebrate axons and separated by Nodes of Ranvier
Myelin sheaths
Invertebrate axons do not have ___________
Myelin sheaths
The end of each branch in an axon that releases chemicals that cross through the junction between the neuron and another cell
Presynaptic terminal (end bulb or bouton)
What is an afferent axon?
Axon that brings information to a structure
What is an efferent axon?
Axon that carries information away from a strcture
Every sensory neuron is ________
Afferent
Every motor neuron is ______
Efferent
What is an interneuron or an intrinsic neuron?
Neuron wherein its cell’s dendrites and axon are contained entirely within a single structure
The ______ of a neuron determines its connections with other cells, thereby determining its function
Shape
Which part of the brain are glia are more abundant than neurons?
Cerebral cortex
Star-shaped glia that wraps around the synapses of functionally related axons
Astrocytes
What are the functions of an astrocyte?
Shields neurons from chemicals
Synchronizes closely related neurons
Generate rhythms such as the rhythm for breathing
Dilates blood vessels to bring more nutrients into the brain areas that have heightened activity
The hypothesis that the tip of an axon releases chemicals that cause the neighboring astrocyte to release chemicals of its own, thus magnifying or modifying the message to the next neuron
Tripartite synapse
Glial cells that act as part of the immune system and proliferate after brain damage, removing viruses and fungi, dead or damaged neurons, and the weakest synapses from the brain
Microglia
Glial cells that build the myelin sheaths that surround and insulate axons and supply an axon with nutrients necessary for proper functioning
Oligodendrocytes and Schwann cells
Where are oligodendrocytes located?
The brain and spinal cord
Where are Schwann cells located?
The periphery of the body
Glial cells that guide the migration of neurons and their axons and dendrites during embryonic development
Radial glia
The mechanism that excludes most chemicals from the vertebrate brain
Blood-brain barrier
A protein-mediated process that expends energy to pump chemicals from the blood into the brain
Active transport
Which chemicals are actively transported into the brain
Glucose, amino acids, purines, choline, a few vitamins, and iron
Vertebrate neurons depend almost entirely on __________ (brain’s main fuel)
Glucose
Why do neurons depend heavily on glucose?
Glucose is the only nutrient that crosses the blood-brain barrier in large quantities
Neurons need a steady supply of _________ to metabolize glucose
Oxygen
