LECTURE 3: Anatomical Organization of the Nervous System Flashcards
What are the 3 anatomical organizations of the nervous system?
Central nervous system
peripheral nervous system
autonomic nervous system
what does the CNS comprised of
encephalon (brain, brainstem, cerebellum) and spinal cford
What does the PNS comprised of
Peripheral nerves (sensory and motor)
what does the autonomic nervous system control
controls autonomic functions (heart rate, respiratory rate, digestion, urination…).
What are the 2 subdivisions of the autonomic nervous system and their functions
Sympathetic: increases the activity of autonomic functions.
Parasympathic: Decreases the activity of autonomic functions.
Where do the autonomic signals originate from?
brain stem
explain a reflex
the signal does not need to reach the brain to provoke a motor action
What are the 3 major levels of the CNS and be able to labrl them
1) cortical level
2) subcortical level
3) spinal cord level
is the spinal cord just a conduit/pathway for signals?
no
What does the spinal cord contain?
- Walking circuits (Central Pattern Generator)
- Circuits for reflexes that control movements
- Circuits for body support against gravity
- Circuits for reflexes that control organ functions (e.g. blood vessels, gastrointestinal, urination…)
what are the components of the subcortical level?
Brainstem (Medulla & pons), mesencephalon, hypothalamus, thalamus, cerebellum and basal ganglia
what is another name for the subcortical level
lower brain level
what does the subcortical level control?
Controls SUBCONCIOUS body activities:
EX: arterial pressure, respiration, equilibrium, feeding reflexes, body temperature, wakefulness and sleep, hormonal regulation…
What is another name for the cortical level and where do you find it?
Higher brain level
Superficial layer of the GREY Matter (2-4 mm)
does the subcortical level ever work alone?
no, always with lower centers
what is the fucntion of the cortical level
Place of the most complicated and sophisticated functions of the NS:
Information Processing
Memory storage
Decision making
Thought Processes
what is the function of the somatosensory system and where is information transmitted to?
function:
Transmission of somatic information from receptors to CNS
Information is transmitted to: Spinal cord Reticular substance (brainstem & mesencephalon) Cerebellum Thalamus Cerebral cortex
what percentage of sensory information is disregarded
99%
explain the motor axis and its function
Important for motion
FUNCTION: Controlling body activities
ex: Skeletal muscle contraction
Smooth muscle contraction (internal organs)
The activity of exocrine & endocrine glands
what are the 3 parts of the neuron structure and their function
Cell body (soma)
Main body of the neuron
Signal processing
Dendrites
Projections of the soma
Signal input
Axon
Extends from soma to the terminal
Signal output
what are the 4 types of neurons
Unipolar neuron:
Multipolar neuron:
Pseudo-unipolar neuron:
Bipolar neuron:
explain unipolar neuron and be able to identify and where you can find it
One process (dendrite & axon on the
same side
Photoreceptors in retina (rods & cones)
explain multipolar neuron and be able to identify and where you can find it
Several dendrites & one axon
Most common cell type (e.g. motoneuron, purkinje cell)
explain pseudounipolar neuron and wehre you can find it
One process (develops from bipolar) Sensory neuron in the spinal cord
explain bipolar neuron and where you can find it
One main dendrite & one axon
Found in retina, inner ear &
olfactory
where do AP’s start?
AXON HILLOCK
explain neuronal communication
Information is transmitted within the neuron by action potentials (electrical signal).
APs propagate along nerve fiber until it comes to the fiber’s end.
Information is communicated between neurons by synapses (chemical signal)
be able to locate the pre and post synaptic terminals and neurons
> :)
be able to identify the different types of neurons
CHECK SLIDES
How is information transmitted within the the neuron?
by action potentials that propagate along nerve fiber until it comes to the fiber’s end.
How is information communicated between neurons??
by synapses (chemical signal)
Be able to loacate the axon hillock and the synapse of neurons
look slides
What is the role of Ca++ in neuronal communication?
1) Ca ++ enter cell and causes neurotransmitters to be released from vesicles
2) Amount of neurotransmitters released is directly related to the number of Ca++ ions that enter
True or false: The Amount of neurotransmitters released is NOT directly related to the number of Ca++ ions that enter
false: amount of Ca++ and amount of neurotransmitters released are directly proportional!
What is another name for a neurotransmitter>
LIGAND
explain neurotransmitter and its function
Neurotransmitter (NT) is a chemical substance synthetized in presynaptic terminal, and released in the synapse by the arrival of the AP.
By diffusing across the synapse, the NT causes the transfer of the AP to another nerve or a muscle fiber
What does the type of NT based on?
Types of NT: based on the action of the postsynaptic neuron
What are the 2 types of NT?
1) excitatory
2) inhibitory
What is the function of an excitatory NT? and give examples
Excite postsynaptic neuron
Examples Glutamate Dopamine (DA) Norepinephrine (NE) Acetylcholine (ACh) Serotonin (5HT)
what is glutamate and what its used for?
Excitatory NT and used used in every part of the brain and spinal cord
What is dopanine and its use?
Dopamine (DA) is an excitatory NT and
it controls motor behavior +pleasures +emotional arousal
What is Norepinephrine (NE) and what does it control
Norepinephrine (NE) is an excitatory nt and it controls sleep patters and focus and alertness
what is Acetylcholine and its function
excitatory NT and activates skeletal muscles
what is Serotonin (5HT) and its function
It is an excitatory NT and it is responsible for MOOD+ appetite+sleep+memory+learning
What is the function of a inhibitory NT and give example
Inhibit postsynaptic neuron
ex: GABA
TRUE OR FALSE:
Many sedative/tranquilizing drugs act by enhancing the effects of GABA
TRUE
What are the 4 steps of Synaptic Transmission(Mechanism of Neurotransmitter Release)
- AP ARRIVES AT THE PRESYNPATIC TERMINAL
- Local depolarization opens voltage-gated Ca2+ channels and Ca2+ ions flow into terminal
- Ca++ ions trigger the fusion of synaptic vesicles with the pre synaptic membrane
- Release of the transmitter into the synaptic cleft (exocytosis)
Do NT penetrate the postsynpatic neuron
NO
What does a postsynaptic membrane contain to allow AP propagation?
Postsynaptic membrane contains receptors that bind the neurotransmitter released from the presynaptic terminal
What are the 2 types of receptors on the postsynaptic membrane and what are they?
ionotropic: ion channel
Metabotropic receptor: Second messenger activator
are ion channels integrated or non integrated
INTEGRATED
What are the 2 types of iion channels in ionotropic receptors and their functions
CATION: allow cations (e.g. Na+, Ca2+) to pass. These channels excite (depolarize) the postsynaptic neuron (e.g. Glutamate receptor)
ANION: allow anions (e.g. Cl-) to pass. These channels inhibit (hyperpolarize) the postsynaptic neuron (e.g. GABA receptor)
Do ion channels close and open rapidly or slowly? and why
rapidly (< 1 sec)
providing a very rapid control of postsynaptic neurons: Fast synpactic transmission!
Explain Metabotropic Receptor (Second messenger activator)
Metabotropic Receptor (Second messenger activator) is a protein structure that causes prolonged changes in the neurons (seconds to months) by activating substances inside the postsynaptic neuron, slow synpactic transmission
Explain metabotropic receptor
Metabotropic Receptor (Second messenger activator) is a protein structure that causes prolonged changes in the neurons (seconds to months) by activating substances inside the postsynaptic neuron, slow synpactic transmission
Do ionotropic receptors have slow or fast synaptic transmission?
FAST
Do metabotropic receptors have slow or fast synaptic transmission?
SLOW
What does one of the most common types of 2nd messener system use?
G PROTEINS
explain g proteins in second messenger activator
- The G-protein is a protein complex (α, β, γ sub-units) attached to the interior portion of the receptor protein
- The binding of the transmitter on the receptor activates the G-protein, which initiates a cascade of events leading to alterations in the cellular activity
- Upon the activation of the G-protein, the alpha sub unit detaches from the complex and activates multiple functions inside the cell
what is one function of METABOTROPIC RECEPTOR (slow synaptic transmission)
Learning and memory
What does the binding of the NT on the receptor do?
opens ions channels and increases the permeability of ions
causes the postsynaptic membrane potential to change from the resting state. The new potential is called Post Synaptic Potential
What are the 2 types of post synaptic potential
excitatory post synaptic potential (EPSP)
inhibitory post synaptic potential (IPSP)
Explain excitatory post synaptic potential
The membrane potential moves towards less negative values (> Vm, depolarization).
Increased permeability to Na+ and/or Ca2+ (more positivity inside)
Caused by the activation of excitatory receptors
explain inhibitory postsynaptic potential
The membrane potential moves towards more negative values (< Vm, Hyperpolarization).
Increased permeability to Cl- and/or K+ (more Negativity inside).
Caused by the activation of inhibitory receptors
What are the 3 states of a neuron in Synaptic Excitation/Inhibition on the Postsynaptic Membrane and be able to indentify the diagram
a) resting neuron
b) Neuron in an excited state:
with a less negative membrane potential (caused by Na+ influx)
-increase in EPSP
c) Neuron in an inhibited stage:
with a more negative membrane potential (caused by K+ efflux, Cl- ion influx, or both)
-INCREASE IN IPSP
What are the 4 characteristics of postsynaptic potentials?
Sub-threshold potentials (below threshold of AP)
Summation of different PSPs (Spatial & Temporal)
EPSPs increase the likelihood of AP (signal transmission)
IPSPs decrease the likelihood of AP (no signal transmission)
True or false: EPSPs decrease the likelihood of AP
FALSE: increase the likelihood of AP
Explain why EPSP gets closer to the threshold and why IPSP gets further
EPSP: gets closer to the threshold since membrane gets more positive
IPSP: gets further from the threshold since membrane gets more negative
explain spatial summation
Excitation of a postsynaptic neuron by a single presynaptic terminal will almost never induce an AP
When many presynaptic terminals (E1 and E2) stimulate the postsynaptic neuron, their respective EPSPs will summate and may exceed the threshold to generate an AP potentialW
Each neuron may be connected to up to ________ other neurons
10 000
explain temporal summation
Successive discharges from the same a single presynaptic terminal, if they occur rapidly enough, can add to one another; that is, they can “summate” to reach the threshold for firing AP
True or false: AP’s begin near the synapses
false begin near the axon hillock
Why doesnt AP generation happen at the soma or dendrite?
Soma & dendrites have few voltage-gated Na+ channels (necessary for the generation of AP)
How to electronic signals propagate to the axon hillock
by electronic conduction (i.e. propagation in the fluids without generation of AP)
explain synaptic plasticity
Synaptic plasticity is the ability of a synapse to strengthen or weaken over time, in response to increases or decreases in its activity
What affects synaptic plasticity (3)
1) Change in the quantity ofneurotransmittersreleased
2) Change in the number of postsynaptic receptors
3) Change in the response of the postsynaptic neuron to neurotransmitter (greater postsynaptic potential)
What are the 4 types of synaptic plasticity and explain them
1) Synaptic enhancement (potentiation): increase in the efficacy of the synapse
2) Synaptic depression: decrease in the efficacy of the synapse
3) Short-term plasticity: lasts from few milliseconds to min
4) Long-term plasticity: lasts from hours to months
what are Selective serotonin reuptake inhibitors (SSRI)
ANTIDEPRESSANT
explain how Selective serotonin reuptake inhibitors work
believed to increase the extracellular level of serotonin by limiting its reabsorption into the presynaptic cell,
increasing the level of serotonin in the synaptic cleft available to bind to the postsynaptic receptors
Makes seratonin move available to the system
