BIOL 0800 Reading- Chapter 6 Flashcards
(278 cards)
Why are neurons said to serve as integrators?
Because their output reflects the balance of inputs they receive from up to hundreds of thousand of other neurons
What are processes, referring to neurons?
Long extensions, which connect neurons to each other and perform the neuron’s input and output functions
What are dendrites and dendritic spines?
Highly branched outgrowths that receive most of the inputs from other neurons; and knoblike outgrowths that increase the surface area of dendrites even more, and often contain ribosomes
What is contained in dendritic spines that generally isn’t contained in dendrites? Why?
Ribosomes that allow dendritic spines to remodel their shape in responses to variation in synaptic activity
What is the axon?
Also called a nerve fiber; long process that extends from the cell body and carries output to its target cells
What is the initial segment or axon hillock?
The region of the axon that arises from the cell body; the “trigger zone” where electrical signals are usually generated
What are collaterals?
Branches of the axons that increase the cell’s sphere of influence
What is the axon terminal?
The end of each axon branch that is responsible for releasing neurotransmitters from the axon
What are varicosities?
A series of bulging areas along the axon that can also release chemical messengers from the neuron
What is myelin?
The layers of highly modified plasma membrane wrapped around the axon by a nearby supporting cell called an oligodendrocyte; shields the axon from excess electrical signal and prevents loss of the axon’s own electrical signal
What is an oligodendrocyte?
In the brain and spinal cord, supporting cell that branches to for myelin on axons; can support up to 40 different axons
What is a Schwann cell?
In the PNS, cells that form individual myelin sheaths surrounding small segments of the axons at regular intervals; don’t cover the nodes of Ranvier
What are the nodes of Ranvier?
The spaces between adjacent sections of myelin where the axon’s plasma membrane is exposed to extracellular fluid
What is the purpose of the myelin sheath?
To speed up conduction of the electrical signals along the axon and to conserve energy
What is axonal transport?
The movement of various organelles and other materials as far as a meter between the cell body and the axon terminals; depends on scaffolding of microtubule rails running along the axon and motor proteins called kinesins and dyneins
What are kinesins and dyneins?
Motor proteins that facilitate axonal transport along the microtubule “rails”
What is the difference in kinesin and dynein movement?
Kinesins usually undergo anterograde movement (from cell body to axon terminals) and dyneins usually undergo retrograde movement (from axon terminals to cell body)
What is anterograde movement with kinesins useful for?
Moving nutrient molecules, enzymes, mitochondria, neurotransmitter-filled vesicles, growth factors, and other organelles
What is retrograde movement with dyneins useful for?
Carrying recycles membrane vesicles, growth factors, and other chemical signals that can affect the neuron’s morphology, biochemistry, and connectivity; also for harmful agents can invade the central nervous system
What are afferent neurons?
Convey info from the tissues and organs of the body toward the central nervous system
What are efferent neurons?
Convey info away from the CNS to effector cells like muscle, gland, or other nerve cells
What are interneurons?
Connect neurons within CNS
What are sensory receptors?
At the peripheral ends of afferent neurons, to respond to various physical or chemical changes in their environment by generating electrical signals in the neuron
How do sensory receptors work?
Generating electrical signals in the neurons; propagate electrical signals from their receptors into the brain or spinal cord