M2 Neuroscience at a Cellular Level Flashcards
The basic unit of the nervous system (Nerve cell)
Neuron
Excitable cells
Neuron
Specialized for reception of stimuli and conduction of nerve impulse
Neuron
Functions of Neuron
Reception, Integration, Transmission, Transfer of information
- Has single neurite
- Divides into two branches
- One branch is from the peripheral nervous system and the other is from central nervous system.
Unipolar
Parts of Unipolar
Fine terminal Branch and Dendrites
Found at the peripheral end of the axon
Fine Terminal Branch
found at the reception site.
Dendrites
Have two axons and no true dendrite
For example: Dorsal Root ganglion
Pseudounipolar
Has an elongated body
Bipolar
Found in:
- Retinal bipolar cells
- Sensory Cochlear
- Vestibular Ganglia
Bipolar
Most common type of neuron
- specialized to receive and accommodate huge amounts of synaptic input to their dendrites.
- Example: Found mostly in spine and brain
Multipolar
Long axon that may be as long as 1 meter or maybe more.
Golgi Type 1
Can be found in:
- Pyramidal cells
- Purkinji cells
- Motor cells
Golgi Type 1
- Have short axons
- Outnumbers Golgi type 1
Golgi Type 2
Found in:
- Cerebral cortex
- Cerebellar cortex
Golgi Type 2
a. Stores the genes
b. Control center
Nucleus
a. scattered throughout the cell body,dendrites,and axons
b. Provide energy for neuron
Mitochondria
Includes: Rough, smooth ERs and Golgi bodies
Golgi complex
has Nissi substance
Rough ER
Branches of neurons that extend from the cell body
Dendrites
They receive incoming synaptic information and thus, together with the cell body, provide the receptive pole of the neuron
Dendrites
appears as head of mushroom in microscope
Dendritic spines
conducts electrical signals from the initial segment
Axons
The initial segment: contains alot of sodium channels to initiate conduction. What is this place called?
“Trigger Zone”
The space without Nissi substance
Axon Hillock
Consists of multiple concentric layers of lipid-rich membrane
Myelin
Is divided into segments about 1 mm long by small gaps. The spaces/gaps in between them are called?
Nodes of Ranvier
Serves to increase the speed (Saltatory Conduction) of impulse conduction along the axon.
Myelination
Where two neurons come into close proximity and functional interneuronal communication occurs.
Synapse
the site of such communication
Synapse
Examples of Synapses
Axodendritic, Axosomatic, Axoaxonic
Axon terminal connects to a dendrite
Axodendritic
Axon terminal connects to a soma (cell body)
Axosomatic
Axon terminal connects to an axon
Axoaxonic
Opens in response to a neurotransmitter binding to its binding pocket on the channel
Ligand-gated ion channels
open almost instantaneously and close as quickly
Voltage gated ion channels
important in the propagation of action potentials
Voltage gated ion channels
specific to sensory neurons
Modality Gated Channels
open in response to mechanical forces (i.e., stretch, touch, and pressure) or temperature changes
Modality Gated Channels
are always open and allow small numbers of ions through the membrane at a slow, continuous rate
Leak Channels
Important for setting the electrical potential
Leak Channels
- The difference in electrical charge across the cell membrane
- measured in millivolts (mV)
Electric Potentials
- When a neuron is not transmitting information
- Typically -70mV
Resting Membrane Potential
- Mainly maintained by Na/K pump (sometimes even the leak channels)
- It is negative because anions are inside the cell.
Resting Membrane Potential
- The initial change in membrane potential
- it spreads only a short distance along the membrane before dissipating due to the activity of leak channels and the Na+/K+
Local Potential
Types of Local Potential
- Receptor potential
- Synaptic potential
generated when modality gated channels are open
Receptor Potential
is essential for rapid movement of information over long distances
Action Potential
is a large depolarizing signal that is actively propagated along an axon by repeated generation of a signal
Action Potential
Uses ALL or NONE Principle
- If the electrical signal did not reach the threshold, No AP is generated.
Action Potential
- Na and K are within their default place
- Na/K pumps are closed
- Nerve is at -70mV
Action Potential: 1st step-Resting Membrane Potential
- Due to local potential, the neuron’s experiences depolarization.
- Na/K pumps still closed
- Neuron may be at -55mV(Threshold) or less
- If the neuron hits -55mV → More depolarization
- If the neuron is less than -55mV → No depolarization
Action Potential: 2nd step Slow Depolarization
- Possible if threshold was achieved.
- Na/K pumps are now open
- Neuron reaches 35mV
Action Potential: 3rd step Fast Depolarization
- Na pumps are closed
- K pumps are is still open
- Electrical potential decreases
Action Potential: 4th step Repolarization
- K pumps are is still open
- Electrical potential decreases going back to RMP
Action Potential: 5th step Hyperpolarization
Types of Synapses
Chemical and Electrical
- Dominant type of synapse
- Uses neurotransmitters
Chemical
Mostly found on places where electrical stimulation is found such as muscles.
Electrical
Parts of Chemical Synapse
- Pre-synaptic terminal
- Synaptic Cleft
- Post Synaptic Membrane
Found at the terminal axon where neurotransmitters are first found.
Presynaptic Terminal
Where Vesicles release transport substances towards the next membrane.
Synaptic Cleft
Found at the dendrite of the adjacent neuron of the presynaptic terminal. Receives the information.
Post Synaptic Membrane
Steps of Chemical Synapse
- AP comes
- Voltage-gated Ca gates are open
- Influx of Ca promotes release of
neurotransmitters - Neurotransmitters binds to
receptor sites.
It is mostly for excitatory effect but has some inhibitory effects (vagal response to heart).
Acetylcholine
Secreted by: large pyramidal cells from the motor cortex, basal ganglia, motor neurons (skeletal muscles), preganglionic neurons of autonomic nervous system and postganglionic neurons (sympathetic nervous system)
Acetylcholine
To help control overall activity and mood of the mind, such as increasing the level of wakefulness
Norepinephrine
Secreted by: locus ceruleus in the pons and postganglionic neurons of the sympathetic nervous system
Norepinephrine
- The effect of this is usually inhibition.
- Seen in Motor system, cognition, and motivation
- Secreted by: Substantia nigra
Dopamine
- Always act as an inhibitory transmitter
- Secreted mainly at synapses in the spinal cord
Glycine
- It is believed always to cause inhibition
- Secreted by : nerve terminals in the spinal cord, cerebellum, basal
ganglia, and many areas of the cortex
Gamma-aminobutyric Acid (GABA)
- inhibitor of pain pathways in the cord
- To help control the mood of the person, perhaps even to cause
sleep. - Secreted by : nuclei that originate in the median raphe of the
brain stem
Serotonin
- It probably always causes excitation.
- Secreted by : presynaptic terminals in many of the sensory pathways entering the central nervous system and cerebral cortex
Glutamate
- Might be explained in the future explain some behavior and memory functions that thus far have defied understanding.
- Secreted by : nerve terminals in areas of the brain responsible for long-term behavior and for memory.
Nitric Oxide
- Called Glial cells
- They do not form synapses
- Play as a supporting cells to other neural activity
Neuroglia
- refers to astrocytes and oligodendrocytes
- both of which are derived from ectoderm
- these cells may have the capability, under some circumstances,
to regenerate.
Macroglia
There are two broad classes of astrocytes: protoplasmic and fibrous.
Macroglia Astrocytes
They occur in gray matter
Protoplasmic
contains glial fibrils
Fibrous
- Provide structural support to nervous tissue and act during development as guidewires that direct neuronal migration
- Aid in repairing damaged neural tissue
- Components of the blood-brain barrier
- Shaped like as star
Macroglia Astrocytes
- Predominate in white matter
- Form a compact sheath of myelin that acts as an
insulator around axons in the CNS - A single oligodendrocyte may cover 30-40 axons
Oligodendrocytes
- Same as oligodendrocytes but only found in PNS
- The only supporting cell in the PNS
Schwann cells
- Normally function as phagocytes.
- Acts as the immune system of the CNS and clean the neural
environment
Macroglial cells
- Regulate the extracellular environment
- Only in the dorsal root ganglia, sympathetic ganglia, and parasympathetic
ganglia
Satellite cells
- Line the cavities of the brain and the central canal of the spinal cord. They
form a single layer of cells that are cuboidal or columnar in shape and
possess microvilli and cilia - Ependymocytes
- Tanycytes
- Choroidal epithelial cells
Ependyma
- Cuboidal or columnar in shape with cilia and microvilli,gap junctions
- Circulate CSF,absorb CSF
Ependymocytes
- Long basal processes with end feet on capillaries
- Transport substances from CSF to hypophyseal-portal system
Tanycytes
- Sides and bases thrown into folds,tight junctions
- Produce and secrete CSF
Choroidal Epithelial cells
is generally characterized by demyelination or axon loss and
can be partial or complete.
Nerve injury
Different Classification of nerve injury are provided by Seddon and
Sunderland.
Nerve injury
involve demyelination and more specifically conduction block.
Neuropraxia
the endoneurium remains intact and serves as a conduit for the regenerating axon, which improves the likelihood of nerve recovery
Axonotmesis
the endoneurium, perineurium, or epineurium is lost, and no conduit exists for neuron regeneration.
Neurotmesis
just like neuropraxia
1st Degree
just like axonotmesis
2nd degree
Just like neurotmesis
3rd to 5th Degree
is the ability of neurons to change their function, chemical profile (quantities and types of neurotransmitters produced), and/or structure.
Neuroplasticity
is involved in learning and creation of new memories and is essential for recovery from damage to the central nervous system (CNS) and can also be maladaptive, as occurs in the neuroplasticity that occurs in chronic pain syndromes.
Neuroplasticity
is a general term used to encompass the following mechanisms:
• Habituation
• Experience-dependent plasticity: learning and memory
• Recovery and maladaptation after injury
Neuroplasticity
- one of the simplest forms of neuroplasticity
- is a decrease in response to a repeated, benign stimulus.
Habituation
the synthesis of new proteins, the growth of new synapses, and the modification of existing synapses
Experience-dependent plasticity: learning and memory
This includes compensatory actions by the body to complete a task
Recovery and maladaptation after injury
Nerve healing occurs through either remyelination or
reinnervation by way of axonal sprouting or axonal regeneration
Peripheral Neuroplasticity
- Requires the presence of uninjured axons within the injured nerve bundle.
- Requires 20% to 25% of uninjured axons to achieve recovery without residual functional weakness.
- at a rate of about 1 mm per day, or 1 inch (25.4 mm) per month
Reinnervation of peripheral neuroplasticity
in which a denervated neuron attracts side sprouts from nearby undamaged axons
Collateral sprouting
in which the injured axon issues side sprouts to form new synapses with undamaged neurons.
Regenerative sprouting
- May happen in optimal conditions, of nutrition, removal or control of disease, and/or cessation of compression.
- Schwann cells produce new myelin, and action potential speeds and strengths will improve and can even return to normal.
Remyelination of Peripheral Neuroplasticity
