Chapter 2 - Nervous System Organization Flashcards
What are the four common features of neurons? What is the function?
- cell body
- dendrites
- axon
- terminal synaptic buttons
What is the function of neuron?
- receive and conduct electrochemical signals
Cell body of neuron
metabolic center, protein synthesis, DNA located in nucleus
Dendrites
receive info from other cells
Axon
- info/AP is conducted down this to other neurons, muscles or glands
- surrounded by myelin sheaths
Terminal synaptic buttons
- chemical communication w/ other neurons
- main proponent in the release of neurotransmitters
- contain vesicles w/ NTs
Myelin sheath
covers the axon of some neurons and helps speed of impulses
Nodes of Ranvier
gaps btwn myelin
Microglia
- glial cell in CNS
- phagocytic, clean/metabolize debris and dead cells
- increase in number when brain is injured
Astrocytes
- glial cell in CNS
- feet form BBB, provide nutrient (glucose) and structural support, also phagocytic
Oligodendrocytes
- glial cell in CNS
- form myelin sheaths
Schwann cells
- glial cell in the PNS
- form myelin sheaths
Resting membrane potential
- -70 mV
- caused by electrical imbalance btwn inner and outer surface of membrane
What ions maintain resting membrane potential?
- Na+ - outside of membrane, always excitatory
- Cl- - outside of membrane, always inhibitory
- K+ - inside of membrane, always inhibitory
- negatively charged proteins
Action potential
- electrical potential across neuron membrane that raises potential to threshold (-55mV)
What do action potentials result in?
- selectively permeable membrane to ions
- active transport of Na+ and K+
- voltage gated Na+ channels open, letting Na+ go into cell, triggers opening of K+ channels, which moves K+ out of the cell
Channel
- ions can cross the lipid belayed through the appropriately shaped channel
Gated channel
- changes shape to allow certain substances to cross membrane
- voltage and chemically gated
Pump
- changes shape to carry substances across the membrane
Depolarization
- when the membrane is getting less negative
- typically results in reaching threshold
Absolute refractory period
NO action potential can occur
Relative refractory period
requires a higher depolarization in order to reach threshold
Where do neurons communicate?
at the synapse
- NTs are released
What occurs when neurons communicate?
- rupture of vesicles that release NTs into the synaptic cleft
- NT binds to binding site and causes the pore to open on the postsynaptic cell