Chapter 12 - Nervous Tissue Flashcards
neurons
functional unit of the nervous system (transmits info)
neuroglia
cells that support and maintain neuronal function
structural classification of neurons is based on…
the number of processes (axons or dendrites) extending from the cell body
-unipolar, bipolar, or multipolar neurons
describe sensory or afferent neurons
- Convey AP into the CNS (central nervous system)
- Occurs through cranial or spinal nerves
describe motor or efferent neurons
- Convey AP from CNS to the periphy
- Cause muscles to do something
describe interneurons
-Mainly located in CNS between sensory and motor neurons
what are the two types of electrical signals that neutrons use?
1.Graded potentials Short distance communication Only within dendrites and cell body – doesn’t travel down axon Determine if AP will ocurr 2.Action potentials Allow for communication over long distances
what is Resting Membrane Potential (RMP)?
- ion channels open or close in response to specific stimui
- More positive charge outside the cell = RMP
- The RMP is negative (-70mV)
Explain the process of maintaining a -70 mV RMP.
- Na+/K+ ATPase pumps out 3 Na+ for every 2 K+ pumped in (net increase of + charge outside cell)
- Leakage channels randomly opened or closed
- More K+ leaks out than Na+ leaks in
explain electrochemical gradiets
- when ion channels are open, specific ions can cross PM down the electrochemical gradient.
- Cations (positive charge) move towards a negatively charged area; Anions (negative charge) move towards a positively charged area
what are the 3 types of gated channels?
- ligand-gated
- voltage gated
- mechanically gated
explain ligand-gated channels.
- respond to a neurotransmitter
- concentrated near synapses, dendrites and cell body of sensory neurons
explain voltage gated channels.
Channels respond to changes in membrane
explain mechanically gated channels
respond to a mechanical or physical deformation
what is a polarized cell?
a cell that exhibits a resting membrane potential
polarized cells have the ability to produce what kind of potential. Explain.
- graded potential
- Open an ion channel, changes the membrane potential
- Spreads for a short distance
depolarizing graded potential
Stimulus causes the cell to be less negatively charged
hyperpolarizing graded potential
Stimulus causes cell to be more negatively charged
When does an action potential occur
if the Axon Hillock reaches -55 mV (threshold)
where do graded potentials occur?
dendrites and cell body, do not travel down the axon
how do graded potentials differ from action potentials?
- travel short distances
- can be added together to create a smaller or larger graded potential
define action potential
- a signal which travels the length of the neuron
- If neuron reaches a threshold potential, an AP is produces and spreads down to axon terminals
- If stimulus is not strong enough = no AP
what are the 2 phases of an action potential?
- depolarizing phase
2. repolarizing phase
what occurs when a graded potential reaches its threshold (-55 mV)
- Voltage-gated Na+ channels open
- Na+ rushes into cell inside becomes more positive
- Membrane potential reaches +30 MV - During the repolarization phase, K+ channels open and K+ rushes outward.
- The cell returns to a more negative state