Week 3 Nervous system Flashcards
What are the two different types of cells Nervous tissue is made up of:
neurons and glial cells
A neurons function is to :
Communicate
Neurons are found in the :
CNS
What are the different types of neurons:
sensory, motor, and interneurons
Glial cells function are :
they are the supporting tissue
What are the various types of glial cells?
Astrocytes, Oligodendrocytes, Ependymal, Microglia, Satellite cells, Schwann cells
Where are glial cells found?
some in CNS and some in PNS
Oligodendrocyte:
(CNS), Myelinate CNS axons, provide structural framework
Astrocyte:
(CNS)Maintain blood brain barrier, structural support, regulates ion, nutrients, and dissolved gas concentrations, absorbs and recycle neuronstransmitters, FORMS SCAR TISSUE AFTER INJURY
Ganglia:
Neuronal cell bodies outside of the CNS
Ependymal Cells:
(CNS) lines ventricles (brain) and central canal (spinal cord), assists in producing CSF
Microglia:
(CNS) removes cell debris, wastes, and pathogens by phagocytosis
Satellite cells:
(PNS) surrounds neuron cell bodies in ganglia, regulates O2, CO2, nutrients and neurotransmitter levels around neurons in ganglia
Schwann cells:
(PNS) are responsible for myelination of peripheral axons in PNS, enclosed in the myelin sheath, participates in repair process after injury
Myelin sheath :
fatty substance covering the axon, forms in sections, produced by Oligodendrocyte (CNS) & Schwann cells (PNS)
Unmyelinated sections are called :
Node of Ranvier
what is the function of the myelin sheath, why do we need it?
speeds up transmission of electrical signal by enabling saltatory conduction, it also insulates axons, & keeps ions in
What is saltatory conduction?
The process in which the electrical signal hops from one node of ranvier to the next node of ranvier, causing the transmission to speed up
Neurons communicate via ____ ____ and _____ _____.
chemical signals and electrical signals.
Chemical signal are called
neurotransmitters
Electrical signals are called:
action potentials (impulses)
Neurons convert _____ _____ into ______ _____.
chemical signals into electrical signals . chemical signal->electrical signal->chemical signal
Chemical signals are located :
between neurons, Axon terminal -> synaptic cleft-> Dendrites/Cell body
Electrical signals are located :
on neurons, Axon hillock-> Axon body-> Axon terminal
What are the two different classes of neurotransmitters:
Excitatory and Inhibitory
What is an excitatory neurotransmitter?
Excites the neuron thereby causing an ELECTRICAL signal to be generated.
What is an inhibitory neurotransmitter ?
Inhibits the neuron from firing an ELECTRICAL signal.
Examples of excitatory neurotransmitters:
Acetylcholine, Dopamine
Examples of inhibitory neurotransmitters:
GABA, Serotonin
Electrical signals are called ____ _____.
Action potentials
where do action potentials occur?
on the axon
What triggers an action potential ?
graded potential
What do action potentials result in?
neurotransmitter release
what is meaning of resting membrane potential ?
Membrane potential of the neuron when it is at rest (not firing any action potentials)
What is the value (mv) of resting membrane potential?
-70 mv
Action potential will only occur when it reaches _____ mv.
-50 mv, threshold
What is the meaning of threshold?
Minimum amount of voltage needed to initiate an action potential
How is the membrane able to reach threshold (go from -70mv to -50mv)?
Via graded potential
What does graded potential do?
Triggers an action potential to occur
What is a graded potential?
Summation of multiple neuronal outputs
What is depolarizing graded membrane potential?
When membrane potential becomes POSITIVE and is taken TOWARDS threshold
What is another name for depolarizing graded membrane potential?
EPSP (Excitatory post synaptic potential)
What causes membrane potential to depolarize?
excitatory neurotransmitters
Acetylcholine, Dopamine
What is hyperpolarizing
graded membrane potential?
When membrane potential becomes negative and is taken away from threshold
What is another name for hyperpolarizing graded membrane potential?
IPSP (Inhibitory post synaptic potential)
What causes hyperpolarizing graded potential?
inhibitory neurotransmitters (GABA, Serotonin)
What are the two types of graded potential types?
Depolarizing & Hyperpolarizing
How do depolarizing graded potentials work?
Excitatory neurotransmitter is released-> binds to receptor->this opens ligand gated NA+ (sodium) channel->NA+ enters-> membrane becomes positive (taken towards threshold)
How do hyperpolarizing graded potentials work?
Inhibitory neurotransmitter is released-> binds to receptor-> this opens the ligand gated Cl- (chloride) channel-> Cl- enters-> membrane becomes negative (taken away from threshold, action potential cannot be generated)
What are the three phases of an action potential?
Depolarization (D, 1st phase),
Repolarization (E, 2nd phase), &
Hyperpolarization (F, 3rd phase)
Graded potential occurs on :
cell body and dendrites
Depolarizing action potential is due to :
Opening of Voltage gated sodium Channels and sodium (Na+) enters / influx
What is another name for depolarization in action potential?
upstroke
At what value do the voltage gated Na+ channels close and depolarization end?
+30 mv
At what value does the depolarization process start in action potential ?
-50 mv
What is another name for repolarization?
downstroke
At what value does repolarization start?
+30 mv
At what value does repolarization end?
-70 mv
Repolarization is due to :
Opening of Voltage gated Potassium Channels and Potassium (K+) exits / efflux
Hyperpolarization is due to :
Voltage gated Potassium Channels being open due to slow closure and thus more Potassium (K+) continues to exit / efflux
At what value does hyperpolarization start?
-70 mv
At what value does hyperpolarization end?
-90 mv
How do you bring the membrane of -90mv back to resting membrane potential of -70mv?
Sodium potassium pump
Action potential will always have the _____ _______.
Same appearance
What is the all or none phenomenon in action potential
Threshold must be reached for an action potential to be generated (no threshold no action potential).
what is the self propagating event in action potentials?
when the action potential propagates itself from axon hillock down to axon terminal
What are the two things that increase the speed of an action potential?
increase diameter and increase insulation (more myelin)
What are refractory periods in action potentials?
resting periods
What are the two refractory period types?
Absolute Refectory Period & Relative Refractory Period
What is absolute refectory period?
Another action potential CANNOT be generated regardless of the strength of the stimulus
what is relative refectory period?
Another Action potential CAN be generated if the stimulus is stronger than the original
In what part of action potential is the absolute refractory period in place?
Depolarization(D) & Repolarization(E), another action potential cannot be generated during Depolarization and repolarization
In what part of action potential is the relative refractory period in place?
Hyperpolarization(F), another action potential can be generated during hyperpolarization
Why can an action potential be generated in relative refectory period, but not in absolute?
In Absolute refectory period, it is because the sodium channels are already open. In relative refectory period, the sodium channels are closed and inactive. The channels can then be forced open w/ a stronger stimulus.
synaptic transmission steps
action potential arrives at axon terminal->voltage gated Ca2+ (calcium) channels open & Ca2+ enters->Ca2+ enters axon terminal causing the neurotransmitter containing synaptic vesicles to release contents via exocytosis->neurotransmitter diffuses across synaptic cleft and binds to specific receptors on post synaptic membrane
What will happen to the postsynaptic membrane once the neurotransmitter binds to it? and what type of graded potential?
Graded Potential will be generated. the type of graded potential depends of the type of neurotransmitter released
If an excitatory neurotransmitter is released it will bind to a ____ gated ____ channel causing resting membrane potential to move ____ ____.
ligand gated sodium channel, towards threshold.
If an inhibitory neurotransmitter is released it will bind to a ____ gated ____ channel causing resting membrane potential to move ____ ____ ____.
ligand gated chloride channel, away from threshold
Excitatory neurotransmitters result in a ______ type of graded potential on the _______ ______.
depolarizing, postsynaptic membrane
Inhibitory neurotransmitters result in a ______ type of graded potential on the _______ ______.
hyper-polarizing, postsynaptic membrane
Neurotransmitters are ____ lived.
short
If neurotransmitters aren’t removed from the synaptic cleft they will ____ to the ___ and cause a change to the _____ _____. (stimulate / inhibit)
re-bind, receptors, post synaptic membrane
What are the four ways via which the neurotransmitter can be removed?
diffusion, phagocytosis, reuptake mechanisms, and enzyme degradation
What is diffusion?
when the neurotransmitters diffuse out of the synaptic cleft
What is phagocytosis?
when neurotransmitters are phagocytosed by the WBCs (microglial cell)
what is a reuptake mechanism?
Presynaptic membrane will take the neurotransmitter back into its terminal
to be repackaged for a new cycle
what is Enzyme Degradation ?
when an enzyme breaks the neurotransmitter into inactive components
The autonomic nervous system is the _____ branch of the PNS.
motor
The autonomic nervous system regulates _______ ______. (breathing, digestion)
unconscious function
what are the two subtypes of the autonomic nervous system, they work opposite of each other.
Sympathetic & parasympathetic
What are the two classes of neurons that work in the autonomic nervous system?
preganglionic and postganglionic.
Preganglionic neuron starts in the ____ and synapses in the ______.
CNS, ganglion
Postganglionic neuron starts in the ______ and goes to the ____ _____.
ganglion, target organs
Sympathetic nervous system is activated when the body senses ____ and increases activity of ___ organs.
stress, vital (“fight or flight”)
Parasympathetic nervous system is activated when the body is ____ and increases activity of _______ organs.
calm, non-vital (“rest & digest”)
In the sympathetic nervous system, the ganglions are in the ______ _____.
paravertebral chains
In the parasympathetic nervous system, the ganglions are in the ______ _____.
target organs
Preganglionic neurons in the sympathetic nervous system release:
acetylcholine
Postganglionic neurons in the sympathetic nervous system release:
norepinephrine & epinephrine
The receptors in the sympathetic system are collectively called the _____ receptors.
adrenergic
What are the two main classes of adrenergic receptors?
Alpha (1,2) & Beta (1,2,3)
In the parasympathetic nervous system the preganglionic and postganglionic neurons both release
acetylcholine
The receptors in the parasympathetic nervous system are collectively called the ______ receptors.
cholinergic
What are the two main classes of cholinergic receptors?
Nicotinic (N,M) & Muscarinic (1,2,3,4,5)