synaptic transmision Flashcards
what are the function of the nervous system
Receives, processes, encodes and rapidly transmits information about the internal and external environment from one part of body to another
Controls muscle movements and the secretions of many glands
Awareness, perception, memory, language, learning, thinking and behavior
- “wired” system
- chemical messengers (neurotransmitters) usually diffuse a very SHORT distance (synaptic cleft)
- acts rapidly for a short period of time (msec, sec, min)
nervous system
- “wireless” system
- chemical messengers (hormones) usually diffuse throughout the body (long distance, carried by the blood)
- acts SLOWLY (minutes to hours) for a long period of time (minutes, hours, days)
Endocrine system
The central nervous system consist of the _______ and ______ ______
brain
spinal cord
The peripheral nerves system consists of _________ nerves and _______ nerves
spinal nerves - carry info to from spinal cord
cranial nerves- carry info to from brain
the peripheral nervous system (PNS) is divided into two divisions:
sensory division
motor division
this PNS division is Afferent.
Conducts impulses from receptors to the CNS
– Informs the CNS of the state of the body interior and exterior
Sensory Division
this PNS division is Efferent.
Conducts impulses from CNS to effectors
motor division
the motor division is subdivided into :
somatic (voluntary) and autonomic (involuntary)
Autonomic nervous system can be further divided into:
–Sympathetic Nervous System
•“Fight or Flight”
–Parasympathetic Nervous System
•“Rest and Digest”
this system has as many neurons as the spinal cord.
it is regulated by the autonomic nervous system but cannot function on its own.
enteric nervous system
dendrites
receive incoming information
Axon
sends information to cell
group or aggregation of neuron cell bodies in the central nervous system
Nucleus
group or aggregation of neuron cell bodies in the peripheral nervous system
Ganglion
bundle of axons (surrounded by glia & connective tissue) in the PNS
Nerve
bundle of axons in the CNS (CNS has glia, but no connective tissue)
Tract/Pathway
Two cell types in the nervous system:
neurons
supporting cells/neuroglia
highly specialized,
excitable cells, generate action potential
Neurons
do not initiate or conduct nerve impulses, important for viability of the neurons, support neurons physically and metabolically, actively modulate synaptic function
Supporting cells or Neuroglia
4 types of glial cells in CNS
astrocytes
oligodendrocytes
microglia
ependymal cells
2 types of glial cells in PNS
Schwann cells
satellite cells
- Surround clusters of neuronal cell bodies in the PNS
* Unknown function
Satellite cells
- Form myelin sheaths around the larger nerve fibers in the PNS
- Vital to neuronal regeneration
Schwann cells
________ _____ cover myelinated and unmyelinated axons in the PNS
Schwann cells
surrounded by Schwann cells that don’t form myelin
Unmyelinated axons
- composed primarily of
lipids
-protects, acts as insulator, increases conduction velocity
-Nodes of Ranvier
-conduct an action potential faster than unmyelinated axons
Myelinated axons
Form myelin sheaths around
axons
One for many axons
Oligodendrocytes
Immune defense cells of CNS
act as specialized macrophages and antigen- presenting cells - release destructive chemicals
Microglia
Excessive release of chemicals form ______ is suspected to contribute to neuronal damage seen in stroke, Alzheimer’s disease, multiple sclerosis and other neurodegenerative diseases
microglia
Line the internal cavities of the CNS
cilia contributes to the flow of CFS
Stem cells
Ependymal Cells
Clear fluid fills the ventricles, central canal and the subarachnoid space
•CSF surrounds and cushions brain and spinal cord: CNS “floats” in CSF
cerebrospinal fluid
Imbalance between formation, circulation and absorption of CSF can cause accumulation of excess of CSF, this is called
hydrocephalus (“water in the brain”)
treatment of hydrocephalus (“water in the brain”) consists of ______ shunting the excess of CSF to veins elsewhere in the body
surgically
The most abundant glial cells, the main “glue” of CNS, hold neurons together in proper spatial relationship
Astrocytes
Important in the repair of brain injuries and in neural scar formation
Astrocytes
Play a role in neurotransmitter activity: take up glutamate and GABA neurotransmitters bringing their actions to a halt
Astrocytes
responsible for establishing the blood-brain barrier (BBB
Astrocytes
brain capillaries the cells are joined by
tight junctions
signal the cells forming the brain capillaries to “get tight”
astrocytes
pathways of the BBB (5)
- paracellular- water soluble agents
- lipohilic- lipid soluble
- transport protein
- receptor mediated trancytosis
- adsorptive transcytosis
negative side to BBB
limits use of drug for treatment of CNS disorders
astrocytes are capable of releasing chemicals similar to neurons (gliotransmitters) , this synapse is called
Tripartite synapse
functions of astrocytes (5)
provide substrates for ATP production Forms BBB secretes neurotrophic factors take up k, water, neurotransmitters source of neural stem cells
2 functions of ependymal
create barrier between compartments
another source of neural stem cells
oligodendrocytes forms
myelin sheaths
Cell body is called
soma
Cell processes that extend from the soma and receive input
dendrites
Cell processes that extend from the soma and primarily transmit action potentials (output)
axon
Axon originates from a special region of the cell body called
axon hillock
The myelin sheath is made by ________ in the CNS and by _________ in the PNS
oligodendrocytes
scwhann
Interspersed along the axon are gaps where there is no myelin
nodes of Ranvier
Highly abundant rough ER (site of protein synthesis)
Nissl bodies
______ increase the surface area of a neuron, allowing it to communicate with multiple other neurons.
Dendrites
A dendrite’s surface area can be expanded even more by the presence of _______
dendritic spines
dendritic spines provide membrane space to form as many synapsis as possible - found in the ______
cerebellum
The movement of material is driven by motor proteins:
kinesin (anterograde transport)
dyein (retrograde transport)
anterograde transport
from cell body to axon terminal
retrograde transport
axon terminal to the cell body
Many infectious agents such as the herpes virus utilize ______ transport
to reach their site of action.
axonal
Functional classification of neurons (3)
sensory (afferent)
motor (efferent)
internuerons
conduct action
potentials toward the CNS (coming)
Sensory or afferent
conduct action potentials away from the CNS (going)
Motor or efferent
within CNS from one neuron to another
Interneurons or association neurons
Structural classification of neurons (3)
Multipolar, bipolar, unipolar
Specific location, function, and/or neurotransmitter of neurons (5 hint: ergic)
cholinergic adrenergic serotonergic GABAergic glutaminergic
a change in membrane potential that occurs when voltage-gated ion channels in the membrane open, increasing the cell’s permeability first to Na+ and then to K+.
Action potential (AP)
So long as threshold is surpassed, additional increases in stimulus strength do not lead to increases in the amplitude of the AP - this is referred to as the:
“all-or-none law” (refers to the fact that there is no “in-between“ AP).
In the membrane of dendrites and cell body (soma) of the neuron, the voltage gated Na+ channels are sparse. These areas generate
local (graded) potentials
result from ligand binding to receptor, mechanical stimulation, temperature changes, spontaneous change in permeability
local (graded) potentials
a touch-pressure receptor in the skin, where mechanical energy is converted into electric signals.
Pacinian corpuscle
Graded potentials vary in ________ (the larger the stimulus [stretch or pressure], the larger the depolarization).When the depolarization reaches the threshold, AP is generated in the sensory nerve.
amplitude
Degree of depolarization caused by the graded potential decreases with ______ from the _______: “ripples created by a stone tossed into a pond”
distance
origin
Once an AP is initiated no further triggering event is required to activate the rest of the nerve fiber. The impulse is automatically conducted throughout the neuron without further stimulation by one of two methods of propagation:
unmyelinated nerve axon
myelinated nerve axon
if amplitude is always the same, how do neurons encode for stimuli strength?
by frequent # of AP per second
has after rate of AP conduction
myelinated
the axon with the largest diameter is conduct a faster or slower AP?
faster
Continuous conduction occurs in:
unmyelinated axons
Saltatory conduction
•Occurs in myelinated axons
When AP occurs at one node, opposite charges attract from the adjacent inactive node, bringing potential to threshold so that it undergoes an AP, and so on
schwanncells are in the _______ system
PNS
oligodenrocytes are in the ______ system
CNS
autoimmune disease in which the body defense system erroneously attacks the myelin sheath surrounding the nerve fibers. Leads to myelin damage blocking AP propagation
Multiple Sclerosis (MS)
what are symptoms of MS
visual problems, tingling and numbness, muscle weakness, impaired coordination and gradual paralysis
during this, the portion of the membrane that has just undergone an action potential cannot be restimulated.
corresponds to the time during which Na+-channel gates are not in their resting confirmation.
absolute refractory period
during this, AP can be generated, but it will require considerably stronger stimulation than usually necessary. It happens because fewer than normal voltage-gated Na+-channels are in a resting position and K+ is still leaving
relative refractory period
The ensures the one-way propagation of the action potential down the axon away from the initial site of activation.
refractory period
Junction between two neurons
The Synapse
two types of junctions between synapse
– Presynapticneuron
– Postsynapticneuron
two types of synapse
- Electrical Synapses (pass electrical signals)
2. ChemicalSynapses (use neurotransmitters)
- Found in cardiac & smooth muscle and some neurons & glia
- Allows the action potential of the presynaptic cell to be propagated to the postsynaptic cell
- Bidirectional (two-way), very fast
Electrical Synapses
Synaptic vesicles contain chemical messenger neurotransmitter (NT)
presynaptic terminal
– Space between presynaptic cell
and postsynaptic cell
– Neurotransmitterdiffusion
Synaptic cleft
where Neurotransmitter receptors are found
Postsynaptic membrane
chemical synapse
Monodirectional (one-way)
pre/postsynaptic
synaptic cleft
Events at the Synapse and Exocytosis
(5 steps)
1 AP depolarizes axon terminal
2 voltage gated Ca open and Ca enters cell
3 Ca triggers exocytosis of synaptic content
4 neurotransmitter diffuses across synaptic cleft and binds to receptor in post synaptic cell
5 neurotransmitter binding initiates response in postsynaptic cell
Some NTs increase permeability of Na+ channels, which results in a
graded depolarization
graded depolarization is often referred to
EPSP - excitatory postsynaptic potential
Some NTs increase permeability for K+ or Cl-, which results in a graded
hyper-polarization
Graded hyperpolarizations will bring theneuronalVM fartherawayfrom the threshold. This is often referred to
inhibitory postsynaptic potential or IPSP
Individual EPSPs can combine
through ______
summation
Two types of summation:
Temporal summation
Spatial summation
the same presynaptic neuron stimulates the postsynaptic neuron multiple times in a brief period
Temporal summation
multiple neurons all stimulate a postsynaptic neuron resulting in a combination of EPSPs which may yield an AP
Spatial summation
some chemicals released by neurons have little or no direct effects on their own but can modify the effects of neurotransmitters. These chemicals are called
neuromodulators.
neurotransmitter that are both excitatory and inhibitory (3)
acetylcholine
norepinephrine
dopamine
neurotransmitter that are generally excitatory (3)
glutamate
aspartate
nitric oxide
neurotransmitter that are generally inhibitory
7
GABA glycine serotonin histamine substance P endorphin enkephalin
Ionotropic receptors
- Fast transmission
- Effect is very brief (a few ms to tens of ms)
Metabotropic receptors
second-messenger mediated
_______ is the major inhibitory mediator in the brain
GABA
The _____ receptors are Na+ channels, _____ receptor channel is permeable to Ca2+ and Na+
AMPA
NMDA
Barbiturates and benzodiazepines
used to manage the seizures and also as sedatives and anesthetics
Many drugs used to treat depression either block NT reuptake or inhibit NT enzymatic break down, these types of drugs are
anti-depressants
this drug increases levels of DA and NE primarily by blocking their reuptake or promoting their release.
•Amphetamine
