Lecture 8 & 9: Neurons of The Nervous System and Electrical Activity Flashcards
What two parts are the nervous system divided into
Central Nervous System (CNS)
Peripheral nervous system (PNS)
What does the CNS contain
Brain
Spinal Cord
What does the PNS contain
sensory (afferent) neurons
Efferent neurons
Describe the sensory / response procedure
PNS detects stimuli
CNS integrates information
CNS determines a response
CNS sends output signals through PNS
Afferent or sensory neurons transmit sensory information where
CNS
What are efferent neurons also referred to as
motor neurons
What does the Somatic Motor division control
Skeletal muscles
What does the Autonomic division control
Smooth and cardiac muscles, exocrine glands, endocrine glands
What system is the autonomic division found in and what is another name for it
the PNS
Visceral nervous system
Autonomic neurons are further divided into _____ and _____ branches
Sympathetic and parasympathetic branches
Define Sympathetic neurons
Division of the Autonomic nervous system that is responsible for the fight or flight response
Define Parasympathetic neurons
Divisions of the autonomic nervous system that is responsible for day to day activities
What division of the PNS is the autonomic neurons located
Efferent division
Neurons are specialized to carry what and do what with other cells
Electrical signals and communicate
Neurons secrete what
neurotransmitters
The dendrites of a neuron does what
receive incoming info from neighbouring neurons
Neurons are more complex in what nervous system
CNS
What part of the neuron contains the DNA for protein synthesis
Cell body
in a neuron where is an AP fired
Axon hillock
Are the nodes of Ranvier always present?
No, only if myelin is
What type of signals can cross a synaptic cleft
chemical
Where are electrical signals converted into chemical signals and due to what
synaptic terminal and due to influx of Ca2+
What is a distinctive feature of sensory neurons
have longer axons/dendrites to cover longer distances
Describe a pseudopunipolar and bipolar sensory neurons
Pseudo = axon fused to dendrite Bipolar = dendrites and an axon
What type of neurons have the most dendrite branches?
Interneurons
Define an Anaxonic neuron
Doesn’t have an axon
Give A distinctive feature of motor neurons
have long axons and multiple dendrites
What do Glial Cells do and do they outnumber neurons?
provide support for neurons, outnumber neurons by 10-50 to 1
What are the 6 types of Glia cells and where are they located
Oligodendrocytes (CNS) Ependymal cells (CNS) Microglia (CNS) Astrocytes (CNS) Satellite cells (PNS) Schwann cells (PNS)
What is microglia role in the CNS
The immune cells
What do astrocytes make up
the Blood Brain Barrier
How many axons can one Schwann cell myelinate
one axon
Neurons have a ____ density of ion channels
high
The activation of ion channels =
the rapid change in membrane potential
Ion channels are based off
1) ions they let in
2) Where they are located
3) The Gating mechanisms
The 5 types of gating mechanisms are
1) Voltage gated
2) Receptor channels (Ligand-gated channels)
3) Phosphorylation gated
4) Stretch gated
5) Temperature gated
What are the two types of electrical signaling?
1) Graded potentials
2) Action potentials
Describe the 7 guidelines of graded potential
1) Signals that are communicated from one neuron to the next
2) Causes small subthreshold changed in membrane potential
3) Can be depolarizing or hyperpolarizing
4) Slow moving
5) Proportional to the size of the stimulus (can be summed
6) Gradually dissipates as it travels through a cell “like a ripple on a pond”
7) Signal degrades because of electrical resistance in the cytoplam
What are 6 guidelines about action potentials
1) Wave of depolarization
2) All OR NOTHING
3) Always depolarizing
4) Fast, large, amplitude
5) Requires threshold to be met
6) Can not be summed
The 9 steps to the ionic basis of action potential are
1) RMP
2) Cell is depolarized by graded potential
3) Membrane depolarizes causing Voltage-gated Na+ channels to open quickly allowing Na+ into the cell and causing Voltage-gated K+ channels to begin to slowly open
4) Rapid Na+ into the cell depolarizes the cell
5) Na+ Channels inactivate and slower K+ channels fully open
6) K+ leaves the cell
7) K+ Channels remain open and additional K+ leaves the cell causing hyperpolarization
8) Voltage-gated K+ channels close, less K+ leaks out of the cell. NA+ channels begin to recover
9) Cell returns to resting ion permeability and RMP
What three states are the basis of voltage gated NA+ channels regarding action potential
a) Activated
b) Inactivated
c) Closed
The 5 Phases of Action potential are
1) Supra threshold EPSP (Excitatory postsynaptic potential) is met
2) Rising Phase;
a) Voltage gated K+ channels begin slowly opening
b) Voltage gated Na+ channels open upon reaching threshold allowing Na+ to enter, thus depolarizing
3) Falling Phase: Peak met causing Na+ channels to close and K+ channels to all open causing K+ to move out thus repolarizing the cell
4) Recovery Phase: The slow K+ channels remain open even after reducing the RMP, L+ keeps leaving causing hyperpolarization
5) Cell returns to RMP
What are the two types of refractory period and describe each
Absolute refractory period: Can not trigger AP
Relative Refractory Period: Can trigger AP but requires a stronger stimulus
What are the 3 patterns of action potential
a) Single
b) Tonic (Constant and uniform)
c) Bursting (crazy shit then break)
Describe the 2 influences of Extracellular K+
Hyperkalemia: Increased extracellular K+ concentration = RMP closer to threshold
Hypokalemia: Decreased extracellular K+ concentration = RMP more negative resulting in a strong stimulus needed to meet threshold
Compare myelinated axons to unmyelinated axons
Myelinated: much faster, only permeable @nodes of Ranvier
Unmyelinated: Slower, Strength of EPIP dissipated by time it reaches hillock
what are the two ways to speed up the velocity of action potentials along an axon
1) Myelination
2) Axon Diameter
Describe the relationship between axon diameter and velocity
Increases velocity as the axon radius becomes larger
Inverse square relationship
