Module 5 Flashcards
Glial Cells
Supporting cells
Neurons
Signaling units
CNS
Central Nervous System: neurons associated with central processing and located in the brain and spinal cord.
PNS
Peripheral nervous system: neurons associated with sensory input (afferent) and motor output (efferent) and functions to connect the cns to all other parts of the body
Transmittion path of info
stimulous-receptor-afferent pathway-control center-efferent pathway-effector-response
Sensory receptors send info via PNS to CNS for processing and if needed CNS will send new info through the PNS to target organs
Somatic nervous system
Controls voluntary movement of skeletal muscle
Autonomic nervous system
Regulates involuntary functions of organs and tissues.
Sympathetic & Parasympathetic
Semi-independent nervous sys: Enteric nervous sys.
Controls the gastrointestinal tract.
Semi because it can run indep. or through modulation by the atuonomic nervous sys. and contains more nerouns than the spinal cord
Cell body or soma
Portion of cell that surrounds the nucleus and plays a major role in synthesizing proteins
Dendrites
Short branched processes that extend from cell body to receive info through receptors located on membranes that bind to chem. called neurotransmitters
Axon
a large process that extends from the cell body at point of origin-axon hillock and sends info. Contains microtubules parallel and surrounded by myelin sheeth.
Proteins walk along microtubles away (anterograde) toward (retrograd) transport
Myelin
Coil and wrap membranes around the outside of the axon for electrical insulation and speeding up action potential propagation. For CNS, uses multiple processes to mylenate multiple segments of axons.
Axon Terminal
Multiple endings convert the electrical signal into an chem. signal called “synaptic transmission”.
Neurons and ability
Amitotic-lose their ability to divide. Exceptions are olfactory and hippocampal. If damaged or lost is not easily replaced and limited recovery. High metabolic rates & need high lvls of glucose and O2 & will faint if low
Multipolar neurons
Having 3 or more processes that extend out from the cell body. 99% of neurons in humans and major neuron in CNS & efferent PNS
Bipolar neurons
2 processes that extend in opposite directions from the cell body. 1 is a dendrite. 1 is the axon. In retina of eye & olfactory sys.
Unipolar neurons
1 short process that extends from the cell body and then branches into 2 more processes that extend in opposite directions. Extend perpherally for sensory reception. Part that extends towards the CNS is the centrral process. Found in Afferent PNS
Sensory neurons
Afferrent neurons transmit info from sensory receptors in the skin or internal organs toward CNS for processing
Unipolar
Motor neurons
Efferent neurons transmit info away from CNS toward some type of effector
Multipolar
Interneurons
located between motor & sensory pathways are involved in signal integration.
Most are confined within the CNS
Synaptic Transmition
Neuron to cell or neuron across the synaptic terminal
Chem. Synapses
Occur when membranes close together but remain distinct leaving a space. Neurotransmitters are released into the synapse to the presynaptic terminal. the narrow space between the 2 regions is the synaptic cleft. Receiving end - postsynaptic terminal. When action potential arrives at arrives at pre. voltage gated Ca channels open= influx of Ca.= activation of exocytosis= release of neurotransmitters and binds to receptors in postsynaptic membrane and induces a conformational change= pore in membrane for ions to move through. Depolarizing- excitatory Hyperpolarizing- inhibitory
Electrical synapses
Occur when membranes are linked together (gap junctions). Heart muscle.
EPSP
IPSP
Excitatory Post Synaptic Potential: Cause change to initiate an action potential
Inhibitory Post Synaptic Potential: Cause change in membrane to prevent an action potential.
Afterwards it will go to resting membrane potential
Spatial Summation
Many ESPS from multiple synapses can combine at a soma to make a larger voltage change which exceeds threshold and cause action potential
Temporal Summation
ESPS from the same synapse can combine if they arrive in rapid succession
Requiring multiple EPSPs to fire an action potential are ways that neurons increase sensitivity and accuracy
Excitatory Synapses
Use glutamate or aspartate as neurotransmitters to bind to non-selective cationic channels for Na & K to pass.
Long-term Potentiation: glutamate neurotransmitter & NMDA receptor. NMDA is ligand Na & voltage regulated so permeable to Ca second messenger cascade that results in increased glutamate receptors= increase strength of synapse lasting for weeks or more.
Electrical synapses are found in the heart.
Inhibitory synapses
GABA & Glycine neurotransmitters bind to receptors that increase Cl- which moves into the cell & opposes depolarization
Modulatory synapses
Can be primed by neuromodulators to respond more powerfully to other inputs
Ex: norepinephrine has little effect on synaptic transmission but when cell is exposed to it 1st it will react more powerfully to glutamate
Microglial Cell
Glial cell
Rapidly activated in CNS to injury. Become phagocytic. Also present antigens to lymphocytes in response to infection. Could be toxic to neurons.
Ependymal Cell
Glial cell
Line the cavities of the CNS & are important barriers between the cerebral spinal fluid and brain extracellular space. Beat their celia to help circulate the cerebral spinal fluid
Oligodendrocyte
Glial cell
Provide & maintain myelin sheaths around axons. pH regulation of CNS
Multiple sclerosis: destruction of oligodendrocytes resulting in a reduction in myelin= decrease in conductivity and action potential= loss of sensory perception & motor control
Node of Ranvier
Exposed axon
Multiple sclerosis
Autoimmune disease that results in the selective destruction of oligodendrocytes via demyelination= loss of sensory perception and motor control, decreases conduction velocity and duration of action potentials
Schwann Cell
Glial cell of the PNS
the mylenating cell of the PNS of a single segment of an axon.
Satellite Cell
Glial cell of the PNS
Help regulate the external chem. environment around neurons of the PNS. (Similar to astrocyte of CNS). Highly sensitive to injury and inflammation.
Astrocyte
Have an enormous amount of processes that wrap around blood vessels and neurons. Modify extracellular environment around neurons
Glycogen Storage
Astorcyte
store all glycogen present in the CNS, used to help meet the high metabolic needs of the CNS. Main source is blood glucose
K+ Permeability
Astorcyte
Trap K+ through Na+/K+ ATPase pump and co-transporters.
Gap junctions
Astorcyte
Astocytes are coupled to each other as well as other glial cells and neurons through gap junctions. This may serve to help modulate activity and sensitivity in the CNS
Neurotransmitters
Astorcyte
Astorcytes synthesize over 20 different neurotransmitters and take up excess neurotransmitter to help terminate signals at the synapse
Growth Factors
Astorcyte
Actorcytes secrete a variety of growth factors which are important for the establishment of fully functioning excitatory synapses
Hyper-polarizing is
inhibitory
Long term potentiation
Very important subset of synapses in the brain includes a group capable of forming memories by increasing the activity & strength of synapse
Uses Glutamate the NMDA receptor
NMDA receptor is ligand & voltage regulated
Blood Flow
Astrocytes can modulate blood flow in the brain by inducing localized vasodialtion or constriction through gap junctions between astrocytes and endothelial cells of brain blood vessels
