Chapter 7 Flashcards
Prepare for Exam 2
Review the anatomy and functions of neurons and glia in the 1st 8 to 9 pages of the chapter.
Note: when figure numbers are mentioned, the 10th ed. Is sited 1st and the 9th is in REVIEW
What is a “resting membrane potential”? i.e. , what does this mean?
The potential difference across a cell membrane when the cell is in a unstiumlated stated, the resting potential is always negatively charged on the inside of the membrane.
What is an “excitable” tissue” Give examples.
Ability of the specialized cells to answer the stimulation by a change in membrane potential or generation on action potential. Examples include: nerve, muscle, and certain secretor cells.
Depolarization:
Appropriate stimulation causes positive charges to flow into the cell. Up flow.
Depolarzation of dentrite is excitatory.
threshold level:
The minimum amount of stimulus required to start an action potential.
Overshoot:
Continuation of depolarization until the peak of action potential has been reached.
Repolarization:
A return to the resting membrane potential.
Hyperpolarization:
If the stimulation inside the cell causes the inside of the cell to become more negative, the line will reflect downward. Hypolarization of dentries is called inhibitory.
Why are the Na and K ion channels often called gates? Why are they “voltage regulated”?
These are called voltage regulated gates because they open when stimulated by depolarization.
“All or None Law”:
Either a action potential happens or it doesn’t. If depolarization is below the threshold value, the voltage-regulated gates are closed; vise verce.
“Coding for Stimulus Intensity”:
A stronger stimulus cannot produce an action potential of greater amplitude. Nervous system is frequency modulated.
“Recruitment”
another mechanism by which the nervous system can code for stimulus strength. Stimulus activate axons low with low/high with high
“Refractory Period”:
Refractory Period is a period of time which the never / axon is not responsive to a second stimulus.
Absolute
Cannot respond to any subsequent stiumults, gates are either open or inactive
Relative:
Na cell “recover” from their inactive state, membrane is in the process of repolarizing.
Give a definition of “Cable Properties: What happens to “signal strength” with distance?
Cable properties is the ability of a neuron to transmit charges through its cytoplasm. The strength of the signal decreases with distance. Amps help along the way.
Explain “conduction” in both an “unmyelinated” and “myelinated” axon
Conduction really means that each action potential is a separate, complete event that is repeated or “regenerated” along the axon’s length. Similar to a wave.
Unmyelinated: Conduction rate is relatively slow, however, faster if the unmyelinated axon is thicker (axons are less resistant to the flow of charges)
Myelinated: Myelin has interruptions (node of Ravier which cannot be separated by more than 1 to 2 mm). AP only occurs at the Nodes and “leap” from Node to Node which is called salutatory conduction. (Saltario = Leap in latin). AP is conducted much faster because of voltage-gates channels at the Nodes.
What do “saltatory” and “propagation” mean?
Saltatory = Jump
Propagation: increase (as of a kind of organism) in numbers
What is the range of speed of conduction in various axons?
10,000 per square micrometer.
What is a “synapse”? What are they called at a neuron/muscle junction?
A Synapse is the functional connection between a neuron and a second cell (“Excitable Cells”). In the CNS this other cell is call a neuron, and in the PNS it can be either a neuron or an effector cell in a muscle or gland. These are called myoneural or neuromuscalr junctions.
There are 3 types of neuron/neuron junctions. What are their names?
The three names are: axodentritic, Axosomatic, and Axoaxonic synapses. Almost all synapses, transmission is in one direcetion: presynatpic to postsynaptic.
What are “electrical” synapses?
Electrical Synapses: Gap Junctions: cells must be the approximate equal size and much be joined by areas of contact with low electrical resistance, so impulses can regenerate from one cell to the next w/o interruption. GJ’s are composed of 12 proteins known as connexins.
What are “Chemical” synapses?
Chemical synapses: Release of chemical neurotransmitters from presynatpic axon endings. Requires that a syptice cleft stay narrow. Composed of Presynatpic endings (terminal boutons) and separated from the postsynaptic cell by a synaptic cleft. This is mechanism releases all neurotransmitters
What are “neurotransmitters”? What was the 1st one discovered? What was it called initially?
Neurotransmitters stimulate action potential in postsynaptic cells. The first one that was discovered was ACh (acetylcholine), it was initially called Vagusstoff because Otto Loewi concluded that the nerve endings of the Vagus must have released a chemical.
Understand how “Gap Junctions’ work and where you might find them in our body.
Present in cardiac muscles, some smooth muscles (uterus during labor), neurons in the brain, found between neuroglial cells. GJ’s are composed of 12 proteins known as connexins.
The axon may branch into many _________ axons and each of these ends in a _____________.
The axon is typically a long, slender process of the cell body that sends nerve impulses. It emerges from the cell body at the cone-shaped axon hillock. Nerve impulses arise in the trigger zone, generally located in the initial segment, an area just outside the axon hillock. The cytoplasm of the axon, the axoplasm, is surrounded by its plasma membrane, the axolemma. A few axons branch along their lengths to form axon collaterals, and these branches may return to merge with the main axon. At its end, each axon or axon collateral usually forms numerous branches ( telodendria), with most branches terminating in bulb-shaped structures called synaptic knobs (synaptic end bulbs, also called terminal boutons). The synaptic knobs contain neurotransmitters, chemicals that transmit nerve impulses to a muscle or another neuron.
What do “pre-synaptic”, “post-synaptic” and “synaptic cleft” refer to?
“pre-synaptic”:
“post-synaptic”:
“synaptic cleft”: UPDATE