Week 1 - Study Guide Flashcards
Identify three types of neurons of the Nervous System
Afferent - PNS
Efferent - PNS
Interneurons - CNS
What type of neuron are sensory neurons
Afferent
What type of neurons are motor commands
Efferent
What are the two types of neurons in the PNS
Afferent
Efferent
What is the neuron that is in the CNS
Interneuron
What is Afferent neurons role?
*Sensory
*Receive Incoming information
*Internal & External
*needs to be processed at the brain
What is Efferent neurons role?
*Send out motor commands
*Action Potential -motor output
* Effector organs
What is Interneuron/Association neurons role?
- Connection
- Integration
- Make sense of information going to the brain
Reflexes use…
excitatory and inhibitory
Divisions of the NS
CNS
PNS
Role of the CNS
Integrative Control Center
Where is the CNS located?
Brain and Spinal Cord
Where is the PNS located?
Everything else except the brain and spinal cord
What are the divisions of the PNS
Afferent Division
Efferent Division
What are the branches of the Efferent Division
Somatic NS
ANS
What are the branches of the ANS
Sympathetic NS - fight or flight
Parasympathetic NS - rest & digest
Afferent division of PNS
- Sensory
- Pathway bringing info to CNS
Efferent division of PNS
- Motor
- sending commands to peripheral structures
Somatic NS role
Voluntary motor output
Reflexes
Skeletal muscle
Autonomic NS role
involuntary motor output
Two cell types
Neurons
Neuroglia
What are neurons
excitable cells
sensory & afferent
What are neuroglia cells
Supporting cells
4 types of neuroglia cells
- astrocytes
- Ependymal cells
- Oligodendrocytes
- Schwann cells
Which type of Neuroglia cells belongs to the PNS
Schwann cells
Special characteristics of Neurons?
- Long-lived
- Amitotic - no cell division
- high metabolic rate
- Plasma membrane function
What are the basic parts of the neuron?
- Dendrites
- Cell body
- Axon Hillock
- Axon
- Myelin Sheath
What part of the neuron integrates information?
cell body
What parts of the neurons do incoming signals come into?
Dendrites & cell body
Where does the action potential travel
Axon
What is the long extension out from the cell body to the next cell
Axon
Cell that creates myelin in CNS only
Oligodendrocytes
Only part of it wraps around an axon
What is a feature unique to Schwann cells?
Neurilemma - a bump as you roll Myelin - think pigs in a blanket
Nodes of Ranvier
Myelin Sheath gaps in between Schwann cells
What ions are at the Nodes of Ranvier?
Na+ & K+
Saltatory Conduction
Jumps from Node to Node for faster signaling
What are the most abundant glial cells in the CNS
Astrocytes
What do astrocytes do?
- BBB
- Control Chemical environment
- form tight junctions
Neurons role
Signaling system in and out
Ependymal Cells role
- Lining cavities of CNS
- Cilia moves CSF past stationary cells
What cells belong to the PNS?
Neurons
Schwann cells
What cells belong to the CNS
Epyndemal cells
Neurons
Astrocytes
Oligodendrocytes
What cells belong to both PNS and CNS
Neurons
Schwann Cells role
Speed signal travel
Oligodendrocyte role
Speed Signal travel
What is the difference between Oligodendrocyte and Schwann cells
- Oligodendrocytes only wrap myelin around part of the axon
- Oligodendrocytes do not have a neurilemma - bump
Permeability
Whether or not it can get across the membrane
Resting membrane potential
-70mV
* more Na+ and Cl- ions outside the cell
* more K+ and anionic proteins in the cell
How is resting membrane potential maintained?
Na+/K+ pump
What is threshold
-55mV
What is the location where an threshold needs to be met before an action potential happens?
Axon Hillock
Changing membrane potential - DEPOLARIZATION
- Becomes less negative
- increase likelihood of AP
- positive ions enter cell bringing closer to threshold -55mV
Changing membrane potential - HYPERPOLARIZATION
- Becomes more negative
- decrease likelihood of AP
- getting further away from baseline of -70mV
Changing membrane potential - ACTION POTENTIAL
- stimulus
- threshold met -55mV
- NA+ channels open
- Spike to +30mV - Depolarization occurs
- Na+ close
- K+ channels open
- Repolarization occurs
- Back to baseline -70mV
- Hyperpolarization occurs
- Na+/K+ pumps bring back to baseline -70mV
which resets to resting membrane
Two main types of ion channels
Leak channels
Gated Channels
Three types of gated channels
- Chemically gated
- Voltage gated
- Mechanically gated (auditory example)
How to open a chemical gate
- Chemical has to bind to receptor to open gate
- Specificity - one shape one job
How to open a Voltage-gated channel
If Na+ rushes in -
Changes the voltage
Na+ channels open on the axon where voltage change occurs
What are two types of signals
- Graded Potential
- Action Potential
Describe Action Potentials and location
- Outgoing signals down the axon
- maintains signal whole time - on/off
- long distance signals of axons
- Voltage change -70mV to +30mV
- occurs in nerves and muscles
Describe Graded Potentials and location
- found on cell body and dendrites
- incoming short signals
- Spread and lose signal strength
- They travel to the Axon Hillock
- Need significant strength to make threshold at axon hillock -55mV
Which gate is fast?
Sodium
Which gate is slow?
Potassium
What ions are critical in NS transmissions?
Na
K
Ca
What triggers neurotransmitter release?
Calcium influx
Electrical Synapses
- less common
- Gap Junctions in Heart and developmental
- Communication is very rapid
- important in embryonic nervous tissue and some brain regions
Chemical Synapses
- Direct relationship between 1st and 2nd cell - 2. Presynaptic neurons release neurotransmitter
- postsynaptic have receptors specific to neurotransmitter
Two types of Graded POSTSYNAPTIC potentials
EPSP. (Na+. K+)
IPSP. (K+. Cl-)
A single EPSP cannot…
- induce an action potential
- EPSP required to add together - SUMMATE - in order to illicit an AP
EPSP causes
- Depolarization =
Na+ influx –> K+ efflux - Na and K flow in opposite direction
IPSP causes
- Hyperpolarization
- Opens channels for K+ and Cl-
- inhibits
What ions and what direction do they move in EPSP?
- Na+ = travels into neuron
- K+ =travels out of neuron
What ions and what direction do they move in IPSP?
- K+ = leaves the neuron
- Cl- = enters the neuron
How do EPSPs reach threshold?
Summation
Temporal Summation
- one or more presynaptic neuron transmit rapid impulses
- Repeated fire close in time
- Single cell fire rapidly
- Cells fire together repeatedly
Spatial Summation
2 different locations fire at the same time
What are forms of membrane channels found on neurons or in the nervous system
Leak channels
Gated Channels
How do we code signal intensity in the nervous system?
The CNS determines stimulus intensity by the frequency of impulses.
How many AP did you send? 1 or 100
How do we slow the signal travel in the neuron?
- Non-myelination
- Smaller diameter of axon
How do we speed the signal travel in the neuron?
- Myelination
- Thicker diameter of axon and myelin sheath
What is Saltatory Conduction?
- AP signal jumps from node to node
- Myelin sheath on axon
- Voltage gate Na+ channels only located at the nodes
- A pattern of conduction when myelinated and is 30x faster
- Faster process
What is Continuous Conduction?
- Non-myelinated axons
- slower process
- Have voltage channels that are evenly spaced
Absolute Refractory Period
- Initial part of sending AP now
- First phase from depolarization to repolarization
- from opening of Na+ channels
- closing of Na+ channels
- Opening of K+ channels
- K+ leaves
- One way transmission
- AP is all or. nothing event
Period of repolarization of the neurons during which it cannot respond to a second stimulus
What is Refractory period?
- Phase immediately following Absolute refractory period
- Repolarization is occurring
- K+ channels finishing up
- Repolarization phase
- Goes into Hyperpolarization
- Na+ / K+ pumps kick in to reset te resting membrane potential
- Threshold for AP generation is elevated
- Exceptionally strong stimulus may generate an AP
Why do Absolute refractory period and relative refractory period matter in the NS?
They wouldn’t be able to return to its resting membrane potential & generate new impulse
What ion is the chief intracellular ion in a resting neuron?
Potassium
Depolarization is –
State in which resting membrane potential is reversed as sodium ions rush in to the neuron
Absolute refractory period is –
the period of repolarization of the neurons during which it cannot respond to a second stimulus
Na+ / K+ pump is a process –
by which ATP is used to move 3 Na+ ions out and 2 K+ ions in the cell to restore resting membrane potential
Direct Action - Relationship
- Chemical released
- need receptor to bind
- gates open ion channels
Example - Neuromuscular Junction
What happens during Direct Action?
- Binds to gate - gate opens
- Promotes rapid response
- Polarization change
Indirect Action - Relationship
- Chemical released
- Receptor only activates if NT binds
- causes an action @ enzyme
- either - excitatory or inhibitory
Not a guaranteed pattern
Case study TTX- Tetanus - goes after Na+ channels
Promotes long-lasting effects
What happens during Indirect Action?
- Neurotransmitter binds to receptor
- Activated by G proteins
- 2nd messengers
- complex
Diverging Circuit
Common in Sensory and Motor Systems
- One to Many
- signal out - better processing
Converging Circuit
Common in Sensory and Motor Systems
- Many to One
Reciprocal Inhibition
REFLEXES
Excite one / inhibit another
