A&P Lecture Test 4
What are the motor divisions of the peripheral nervous system (PNS)?
Somatic Nervous System (SNS) Visceral (Autonomic) Nervous System (ANS)
What causes a change in resting membrane potential?
Stimulation of neuron causes local disturbances in membrane potential -Chemical, light, heat, mechanical force
Nerve cells receive _________ and transmit __________ ___________.
Stimuli; Action potentials
What is the mV value of resting membrane potential?
(-70) mV -Membrane potential only considers a thin film of ions directly adjacent to membrane
Oligodendrocytes
(Glial cell of CNS) -Branched cells -Processes wrap CNS nerve fibers, forming insulating myelin sheaths *-----Increase signal conduction-Responsible for myelin production*
Astrocytes
(Glial cell of CNS) -Most abundant, versatile, and highly branched -Cover entire surface of our brains -Cling to neurons, synaptic endings, and capillaries to form a supportive network *-Help determine capillary permeability (from blood-brain barrier)* *-Guide migration of young neurons* *-Control the chemical environmet* *-Participate in information processing in the brain*
Mircoglia
(Glial cell of CNS) -Really small, ovoid cells with thorny processes -Migrate toward injured neurons -Protective function *-----Phagocytize microorganisms and neuronal debris*
Ependymal Cells
(Glial cell of CNS) -Resemble cuboidal epithelium -Line the central cavities of the brain (ventricles) and spinal column -May be ciliated and have root-like processes *-----Produce and circulate cerbrospinal fluid (CSF)*
Satellite Cells
(Glial cell of PNS) -Surrounds neurosoma in sensory ganglia *-----Provide support and nutrients*
Schwann Cells (or Neurilemmocytes)
(Glial cell of PNS) -Wrap around portion of one axon to form myelin sheath *-----Helps create insulating barrier around axons to allow for passing of electrical activity-aka produces myelin*
During depolarization, membrane potential shifts from -70 mV to ____ mV
+40 mV
A membrane Potential of ____ mV must be achieve to meet threshold.
-55 mV
What happens during deplarization?
-A chemical (ligand) binds to its receptor; opens ligand gated channels. -Flow of Na+ in cancels some of the negative charge (making the membrane potential more positive-continues even after potential has become 0. Electrochemical gradient contributes)
Autonomic Ganglion
-A cluster of neuronal cell bodies in PNS -They are essentially a junction between autonomic nerves originating from the central nervous system and autonomic nerves innervating their target organs in the periphery.
What are the different types of Neuroglia (glial cells) of the Central Nervous System?
-Astrocytes -Microglia -Ependymal -Oligodendrocytes
What are the components of the nervous system?
-Brain -Spinal cord -Nerves -Sensory nerves
What are the possible stimuli for beginning depolarization?
-Change in voltage -Neurotransmitters -Mechanical force
Voltage-Gated Ion Channels
-Channels open when the transmembrane voltage changes around them. -Amino acids in the structure of the protein are sensitive to charge and cause the pore to open to the selected ion
Axon
-Cylindrical extension that extends out from soma, may be shorter or may be longer -Branching from axon is called axon collaterals, which allow for rapid detection -Membrane of axon is the axolemma -Axoplasma
Terminal Arborization
-End of axon branches -Ends are small bulbous regions, which is the synapse -Can target several different cell types
What properties of nerve cells allow for communication between each other?
-Excitability -Conductivity -Secretory ( neurotransmitters-chemicals)
Dendrites
-Extend off of the soma (neurosoma), like tree branches -Extensions allow receiving of information from other neurons
What conditions may cause degeneration of myelin sheaths?
-Multiple sclerosis -Some cases of diabetes mellitus -Parkinson's -Alzheimer's
Neurosoma
-Nerve cell body -Chromatophilic substance (clumps of rough ER in the cell body) -Cytoskeleton compartmentalized rough endoplasm reticulum of area
Function of myelin on axons?
-Protects and insulates axons from one another -Speeds transmission -Functions in repair of axon
Permeability Characteristics of the Plasma Membrane
-Protein synthesized inside of cells are *negatively* charge -Cl- is repelled by proteins and exit through always-open non-gated Cl- channels -Gated ion channels open and close because of a stimulus
Unmyelinated Axons
-Rest in invaginations of Schwann cells or oligodendrocytes. -Not wrapped around the axon -Forms the neurilemma -Gray matter
Mechanically Gated Ion Channels
-When a mechanical change occurs in the surrounding tissue, such as pressure or touch, the channel is physically opened -Thermoreceptors work on a similar principle. When the local tissue temperature changes, the protein reacts by physically opening the channel
Ligand-Gated Ion Channels
-When the neurotransmitter acetylcholine binds to a specific location on the extracellular surface of the channel protein, the pore opens to allow select ions through -Ions in this case are sodium, calcium, and potassium
Axon Hillock
-Where the axon will begin, a small extension from the soma -Where action potentials initiate *-Key for electrical activity of any given neuron!!!!!*
Neurons are stimulated by a signal that is delivered to.....
A localized site on it's surface
How do Metabotropic Receptors work?
1. After binding of the neurotransmitter, the G protein hydrolyzes GTP and moves to the effector protein 2. When the G protein contacts the effector protein, a second messenger is generated such as cAMP 3. The second messenger can then go on to cause changes in the neuron, such as opening or closing ion channels, metabolic changes, and changes in gene transcription.
Process of Mediated - Primary Transport
1. Cytoplasmic Na+ binds to the sodium-potassium pump. 2. Na+ binding stimulates phosphorylation by ATP 3. Phosphorylation causes the protein to change its conformation, expelling Na+ to the outside. 4. Extracellular K+ binds tot he protein, triggering release of the phosphate group 5. Loss of the phosphate restores the protein's original conformation 6. K+ is released and Na+ sites are receptive again; the cycle repeats
What are the functions of the nervous system?
1. Receives sensory input from internal and external stimuli 2. Integrates and processes this information a. Brain and spinal cord process sensory input b. Initiates responses 3. Commands muscles and glands to carry out responses 4. Regulates and maintains homeostasis 5. Establishes and maintains mental activity (allows for complex mental activity)
Ionic concentration differences are a result of 3 processes
1. The Na+/K+ pump 2. Selective membrane permeability 3. Diffusion of ions
The membrane potential is maintained by the Na/K pump. For each ATP that is consumed, ___ Na+ move out and ___ K+ move in.
3; 2
Repolarization
A shift of membrane voltage back toward resting membrane potential
Hyperpolarization
A shift of membrane voltage below (more negative) than the resting potential
Cells (neurons) produce electrical signals called?
Action potential
Local electrical stimuli trigger an explosion of activity in the membrane
Action potential
The electrical signal neurons generate to communicate is call an...
Action potential
What is a glioma?
Adult brain tumors that arise from abnormalities of glial cells. -Most adult brain tumors are like this.. (Note a tumor is a cluster of rapidly dividing cells)
What will the terminal arborization contact?
Another cell
Depolarization
Any shift of membrane voltage (potential) to a more positive value
When stimulated, local potentials will spread into the axon hillock, causing .....
Membrane potential to depolarize
Nerves
Bundles of nervous tissue surrounded by connective tissue
Sensory or Afferent neurons
Carry information (action potential) away from receptors and take it back to the central nervous system
Motor or Efferent neurons
Carry processed information away from central nervous system to some target that will drive movement/change of activity (Ex. Skeletal muscles, some organs)
What are the two subdivisions of the nervous system?
Central Nervous System (CNS) -Brain and spinal cord Peripheral Nervous System (PNS) -Nerves and receptors that extend out from our CNS
In the plasma membrane, ____ is repelled by proteins and exits through what type of channels?
Cl-; always-open non-gated Cl- channels
Anaxonic Neuron (Axonemic in powerpoint)
Communicate locally; brain and retina -No axon
Where else have we seen the requirement of threshold stimulus recently?
Contraction of Skeletal Muscle
Membrane Potential (Potential Difference)
Electrical imbalances that generates a voltage difference across a membrane
What other body system does the nervous system sometimes correlate with?
Endocrine
(T/F) If depolarization reach -55 mV, a partial action potential is generated (always).
False, a complete action potential is generated
(T/F) Inside of plasma membrane is slightly positive.
False, the outside is slightly positive.
(T/F) The stronger the stimuli, the larger the the size of an action potential.
False; Stronger stimuli do not alther the size of action potentials, may cause variation in frequency though
(T/F) There are many more leak channels for Na+ than K+ and Cl-.....the channels are rarely open and are responsible for permeability when membrane is at rest.
False; There are more leakage channels for K+ and Cl- than Na+. These channels are ALWAYS open and responsible for permeability when membrane is at rest.
(T/F) Number of charged molecule and ions inside and outside of the cell are not equal at resting membrane potential.
False; the ions inside and outside of the cell are nearly equal at resting potential
(T/F) Na+, Cl-, and Ca2+ have great affect on resting potential since there are many leak channels for them.
False; these ions have little on the resting potential because there are very few leak channels for them.
Visceral (Autonomic) Nervous System (ANS)
From CNS to smooth muscle, cardiac muscle, and certain glands -Subconscious or involuntary control -Two neuron systems: First from CNS to ganglion Second from ganglion to effector -Ganglion along spinal cord
Somatic Nervous System
From central nervous system to skeletal muscles -Voluntary (can also be involuntary-reflexes) -Single neuron system -Deals with synapses (junction of nerve cell with another nerve cell, neuromuscular junction)
Local Potentials (characteristics)
Graded - Vary in magnitude, according to stimulus strength (more stimulus, larger local potential) Decremental - They get weaker as they spread through a neuron Reversible - If stimulation ceases, membrane potential returns to normal Either excitatory or inhibitory - Depends on chemical signal, can work to inhibit or excite local potentials
Leakage Channels
In certain situations, ions need to move across the membrane randomly. The particular electrical properties of certain cells are modified by the presence of this type of channel.
Trigger Zone
Initial Segment + Axon hillock
There is a high concentration of K and proteins (inside/outside) the membrane
Inside; Salty banana
Electrical properties result from _______ _____________ differences across plasma membrane and permeability of membrane (electrical potential)
Ionic concentration
Ionic Receptor
Is a channel that opens when the neurotransmitter binds to it
Metabotropic Receptor
Is a complex that causes metabolic changes in the cell when the neurotransmitter binds to it.
At equilibrium, there is little movement of ____+ or other ions across the plasma membrane.
K+
Concentration of ____ and proteins higher inside than outside of the cell; ____ higher outside the cell than inside.
K+ and proteins higher inside Na+ higher outside
Movement of K+ (in/out) through leakage channels = movement of ions (in/out) due to attraction to trapped proteins.
K+ out; ions in
During repolarization, what happens?
Membrane potential becomes negative as K+ begins to leave. -Voltage-gated K+ channels open, allowing K+ to leave (thus causing more negativity) -K+ doesn't reach equilibrium until the membrane voltage is below -70 mV
Multipolar Neurons
Most neurons in the CNS; motor neurons -Match the organization of your typical, generic neuron diagram
Efferent Pathways
Motor -Transmit signals from central nervous system to effectors (muscles, glands) -Opposes sensory (afferent) pathway
What are the different types of neurons?
Multipolar Bipolar Unipolar Anaxonic (Axonemic in the powerpoints)
White Matter
Myelinated Axon -Also in spinal cord................................to be continued
Myelination
Myelinating glia wrap several layers of cell membrane around the cell membrane of an axon segment. -A single Schwann cell insulates a segment of peripheral nerve. -In the CNS, an oligodendrocyte may provide insulation for a few separate axon segments
Depolarization causes voltage-gated ____ channels to open transiently.
Na+ -Influx of + charge further depolarizes membrane, opening more v-gated Na+ channels (self-amplifying process)
Mediated - Primary Transport
Na+ K+ ATPase uses ATP hydrolysis to carry Na+ out and K+ in -Establishes steep concentration gradient of Na+
Changes in membrane potential begin with voltage gated ___ channels opening. Which way will the ions move?
Na+; Na+ will move in to the cell
Protein synthesized inside of cells are (positively/negatively) charged.
Negatively
Why does hyperpolarization occur?
Occurs because potassium channels act slower and let out a little more positive charge than was initially brought in (This is when Na-K ATPase kicks in) Or in other words: The increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to resting level
There are high concentrations of Na and Cl (inside/outside) the membrane.
Outside; Salty banana
Unipolar Neuron
Part that extends to the periphery has dendrite-like sensory receptors; touch and pain -Differentiate from Bipolar because the cell body is on its own little branch
What path does the action potential take in the neuron?
Passes from dendrites to soma to axon
What are the different types of Neuroglia (glial cells) of the Peripheral Nervous System?
Schwann Cells (or Neurilemmocytes) Satellite Cells
Initial Segment
Section of fiber between axon hillock and first internode -Together with the hillock, they are known as the *trigger zone*.
Afferent Pathways
Sensory -Transmit signals from receptors to the central nervous system
What are the divisions of the peripheral nervous system (PNS)?
Sensory (afferent) pathways Motor (efferent) pathways
What are the functional classifications of neurons?
Sensory (or afferent) Motor (or efferent) Interneurons (or association neurons)
Bipolar Neurons
Sensory neurons in retina of the eye and nose -One singular dendrite -One axon So cell body in the middle, one branch for dendrites, one for the axon (In picture, axon end has the little bulbs at the end of the branches-aka terminal arborizations)
What is the function of Neuroglia (glial cells)?
To support and protect
Highest density of Na+ gated channels in _________ zone, aka where action potential begins.
Trigger zone.
(T/F) At rest, more K+ and Cl- are moving than Na+.
True
(T/F) Because of the threshold, action potentials are "all or none".
True
(T/F) Leak channels work in both directions
True
(T/F) Myelin is not continuous.
True, there are small little cinches called *Nodes of Ranvier*
(T/F) If leak channels alone were responsible for resting membrane potential, in time Na+ and K+ ion concentrations would eventually equalize.
True.
Gray Matter
Unmyelinated axons, cell bodies, dendrites, neuroglia -In brain and spinal cord -Deal with thoughts and feelings
