Ch 4 - Nervous system Flashcards
1
Q
neurons
A
- translate electrical impulses to chemical signals
- soma/cell body - contains the nuclei
- ER and ribosomes
- dendrites - off of the soma, receive incoming messages
- axon hillock - integrates incoming signal
- determines excitatory or inhibitory
- may deliver action potential
- axon - terminates close to target (muscle, gland, neuron)
- myelin - insulation for nerve fibers
- increase speed of conduction
- produced by oligodendrocytes in CNS
- produced by Schwann cells in PNS
- nodes of Ranvier - breaks in myelin
- synaptic knob - end of axon
- enlarged and flat for max NT
2
Q
synapse
A
- synapse composed of synaptic cleft, nerve terminal, postsynaptic membrane
- synaptic cleft - between neurons. Terminal portion of presynaptic neuron. Dendrites of postsynaptic neuron
3
Q
neuron organization
A
- nerve - multiple neurons bundled in the PNS
- sensory, motor, or mixed
- ganglia - cell bodies clustered
- tracts - axons of CNS
- only carry one kind of info
- nuclei - cell bodies of neurons in a tract
4
Q
glial cells
A
- aka neuroglia
- structural and supportive cells in the nervous system
- astrocytes - nourishment, also form blood brain barrier
- ependymal cells - line ventricles and produce CSF
- microglia - phagocytic
- oligodendrocytes - produce myelin in CNS
- Schwann cells - produce myelin in PNS
5
Q
resting potential
A
- net electric potential difference across the membrane
- -70 mV, balance of -90mV and +60mV, but more permeable to potassium
- inside negative relative to outside
- potassium inside is 140mM and 4 mM outside
- potassium leak channels - facilitate outward movement of K, slow leak, leaves small negative charge inside
- as negative charge builds inside, K is pulled back inside
- equilibrium potential of potassium - no net movement of K (-90mV)
- Sodium inside if 12mM and 145 mM outside, push Na into cell
- sodium leak channels - slow leak into cell and build up electric potential
- equilibrium potential of sodium - positive because moving into cell (60mV)
6
Q
Na+/K- ATPase
A
- potassium into cell and sodium out
- 3 Na out and 2 K in
- more ATP spent on this than any other purpose
7
Q
axon hillock
A
- depolarization - excitatory input, raise membrane potential
- hyperpolarization - inhibitory input, lower membrane potential
- depolarize to a threshold in order to cause action potential (-55 to -40 mV)
- dependent on the summation of all signals
- may be several presynaptic neurons
8
Q
summation
A
- additive effect of mutiple signals
- temporal summation - multiple signals during short period of time
- spatial summation - additive effects based on number and location of signals
9
Q
ion channels during an action potential
A
- when reach threshold - voltage gated sodium channels open and Na in to depolarize
- strong electrochemical gradient
- interior more negative than outside … and interior has less Na than outside
- +35 mV and Na voltage channels are inactivated
- near resting potential will deinactivate them
- closed, open, and inactive states
- +35 mV triggers voltage gated potassium channel to open
- efflux K to reploarize cell
- overshoot resting membrane potential
- hyperpolarization
- absolute refractory period - no amount of stimulation will cause action potential
- relative refractory period - greater than normal stimulatio require for AP
10
Q
impulse propagation
A
- AP down axon to initiate NT release
- wavelike fashion of depolarization down the axon to the nerve terminal
- progressively open sodium channels to propogate potential
- momentary refraction for previous segment - ensures one direction flow
- greater cross section is less resistance and faster transmission
- length also slows down but not as important
- saltatory conduction - signal goes from node to node down axon
- due to nodes being breaks in myelin
- myelin does not allow for signal dissipation
11
Q
excitatory intensity
A
- greater intensity results in more frequent firing
- same potential difference
12
Q
synapse
A
- pre and postsynaptic neurons
- effector - postsynaptic cell (non neuron) such as a muscle or gland
- synaptic vesucles are released that contain NT
13
Q
Neurotransmitters
A
- action potential to nerve terminal
- voltage gated calcium channels open - calcium in
- increase intracellular Ca
- fusion of vesicles to cell membrane at synapse
- exocytosis of NT
- diffuse across synapse
- bind post synaptic receptor
14
Q
NT receptors
A
- ligand gated ion channel - postsynaptic cell is depolarized or hyperpolarized
- G protein coupled receptor - change levels cyclic AMP (cAMP) or influx of Ca
15
Q
NT removal from synapse
A
- broken down by enzyme
- ACh, acetylcholinesterase
- reuptake carrier
- serotonin, dopamin, norepi
- diffuse out of synaptic cleft
- nitric oxide (NO)
