Upgrade to remove ads
S + F Exam 4
Terms in this set (53)
Differentiate among neuronal cell bodies, axons and dendrites.
cell bodies contain the nucleus and other organelles and is the center of the nerve cell
Axons are the long extensions that transfer action potentials to other nerves or tissues
dendrites are short projections all around the cell body that receive synapses from nearby cells
What are Schwann cells and how do they interact with neurons?
Schwann cells are PNS glial cells that wrap around or encase the axons of cell bodies. They provide support and protection to the axons; myelinated axons (wrapped multiple times in Schwann cell) can transmit APs faster
What are the three CT layers surrounding a large nerve? What is the basal lamina in nerves? What is its significance in regeneration?
From outermost to innermost: Epineurium, perineurium, and endoneurium.
Basal lamina is secreted from the Schwann cells and contains fibronectin and laminin, which helps with regeneration and repair
Regeneration is a unique feature of the PNS; when damaged, depending on the damage, the basal lamina and Schwann cells help to regrow and redirect damaged nerve tissue; does not happen in the CNS
What are nervi nervorum and what do they innervate? What are vasa nervorum and what do they supply?
Nervi nervorum innervate other larger nerve cells and the vasa nervorum
Vasa nervorum are capillaries that exist adjacently to nerve cells; they provide nutrients and remove impurities from the nerves
What are the dorsal and ventral horns?
Both horns make up the gray matter of the spinal cord
The ventral horn is the source of outgoing motor nerves that travel to axial muscles
The dorsal horn receives sensory output from incoming nerves
Sensory = Afferent; Motor = Efferent
Dorsal = Afferent; Ventral = Efferent
What is the structure of sensory neurons and how do they differ from other neurons?
A sensory neuron is a unipolar-nucleated cell body that has an axon that breaks in two and extends to a target tissue; a branch connects to the spinal cord
Sensory neurons do not have dendrites, just long axons that we like to call dendrites
Distinguish between the dorsal root ganglia and sympathetic ganglia.
The dorsal root ganglion is where the sensory nerves converge towards the spinal cord; all the sensory info travels through the dorsal root ganglion
The sympathetic ganglia serves the sympathetic nervous system and the "flight or fight" responses
What are the contents of a typical peripheral nerve? Trace the course of the preganglionic and postganglionic sympathetic neurons.
Peripheral nerves extend from the dorsal root ganglion. A peripheral nerve will typically have 3 CT layers and myelinated axons.
COME BACK TO THIS
How do phospholipids organize in the cell membrane?
Phospholipids in the cell membrane arrange themselves so that the hydrophobic lipid tails exist in the inner layer formed by the bilayer
How do alpha helical portions of transmembrane proteins relate to the formation of ion channels?
Transmembrane proteins penetrate the hydrophibic regions of the inner bilayer by way of transversing alpha helices. The hydrophilic regions of the protein repulse from the hydrophobic inner layer to form a channel of hydrophilic molecules that allow ions to pass through. They are conformed to be closed or open according to the signals received by the protein receptors.
Describe the equilibrium potential for ions like K and Na. Include: the role of ion flux and concentration gradients & the significance of concentration and electrical gradients. What does it mean to be in equilibrium in this case?
Theoretical equilibrium: K+ in = K+ out
Describe the membrane potential. Include: role of various ions, differences in permeability and concentration gradients, how it differs from the equilibrium potential.
At equilibrium of a normal cell, K+ is more concentrated inside an axon and Na+ is more concentrated outside. K+ channels are open for K+ to flow freely out of the membrane; Na+ channels are highly controlled and remain closed during resting potential. Concentration and electrical gradient allow for action potentials to fire along the axon to the target.
At resting potential = -70 mV; Na+ outside, K+ inside.
What are the different types of ion channels and how are they activated? What are non-gated channels? Give an example.
Voltage gated: closed gates that open by depolarization of membrane potential
Ligand gated: opened by the binding of a neurotransmitter to the protein receptor
Mechanical gated: opened by pressure, touch, or light
Non-gated channels are pores that are open to ions to freely enter or exit the cells. K+ channels act as non-gated channels.
What are receptor potentials and how are they produced? How are they different from action potentials?
Receptor potentials measure the depolarization of a membrane. They are produced by an external stimuli forcing open gated channels. If the membrane potential is depolarized to threshold, it switches from receptor potential to action potential because the AP can travel to the next membrane. RPs initiate AP transmission.
Describe the action potential. Account for each phase of the action potential in terms of the Na and K channel activities. Why is the initial depolarization and overshoot of the action potential so large in magnitude compared to hyperpolarization?
To achieve action potential:
Na+ ion channels are opened and Na+ flows in (some Cl- flows in as well); the region inside the membrane depolarizes, going from -70 mV approaching to 0 mV. Threshold level (about -55 mV) is reached, action potential is fired, moving along to the next node or membrane. The Na+ channel is shut, and K+ flows out of the K+ channels (both voltage gated and non gated) to re-polarize (and even hyperpolarize).
Depolarization is more potent because Na+ has a greater affinity to entering the cell than K+ has leaving it.
Describe how raising or lowering the extracellular concentration of K can change neuronal excitability.
Raise it: Hyperpolarization Lower it: Depolarization
Compare myelinated vs unmyelinated axons in terms of: Schwann cell configuration, action potential formation, action potential conduction.
Myelinated axons: Wrapped repeatedly by flattened Schwann cell. Nucleus of SC flattened at the edges. Faster saltatory conductions.
Unmyelinated axons: Surrounded by a Schwann cell, with nucleus in the middle; lower APs.
What impact does demyelination have on action potential conduction?
Demyelination: degradation or unraveling of Schwann cells
Demyelinated axons lose conduction because saltatory conduction is damaged and ions can leak through the nongated channels that are usually protected by SC; ionic gradient decreases
Compare ionotropic and metabotropic transmission in terms of receptor and postsynaptic actions, duration of effect.
Ionotropic: Short term and effect transmission; NT stimulates the opening of voltage-gated channels to illicit EPSP or IPSP across membranes
Metabotropic: Long term and effect transmission; NT binds to receptor which activates G proteins to recruit secondary messengers for cell growth and metabolism
What are EPSPs in terms of transmitter, receptor, postsynaptic action and impact on the initial segment?
In EPSPs, the transmitter is usually glutamate, which binds to ionotropic Na+ and K+ channels and forces them open. EPSPs increase ion flux so that threshold is reached and the AP can run along the axon to the effector. (postsynaptic dendrites)
What is the significance of summation of EPSPs and IPSPs?
Summation is the collective energy of stimulus received from EPSP and IPSP NTs; whichever potential is more powerful will effect the axon; constantly changing
Weak PSPs indivdually, but together strong
What does the EEG measure?
Measures the synchronized summation of PSPs acting on cortical neurons.
What are G proteins and how do they play a role in the formation of second messengers?
G proteins are complexes of alpha, beta, and gamma subunits that are energized by GTP. When a metabotropic NT binds to a G-protein coupled receptor, the GTP is hydrolyzed to GDP, beta and gamma subunits detach from the complex and alpha unit binds to a cyclase, which activate cAMP or cGMP, the second messenger. cAMP transmits the info throughout the cell.
Compare the effects of ionotropic and metabotropic transmissions on altering ion channel permeability in terms of mechanism and duration of effect.
Ionotropic trans. open Na+ and K+ channels to change membrane potential; very brief period
Metabotropic trans. use G-Protein coupled receptors to affect change within a cell; longer duration
What is cAMP? Give examples of cAMP actions.
cAMP --> cyclic AMP from the dephosphorylation of ATP
Activated by adenylyl cyclase
cAMP actions: activates PKA, glycogenlysis, hormone-senstive lipases (HSL) to break down fatty acids, and alters K+ channels for longs periods of time
Why do second messenger system have a longer duration than ionotropic transmission?
Secondary messengers help amplify metabotropic transmissions so that the signal lasts longer in a cell; signal is multiplied continuously by recruited messengers
Where does IP3 come from? What generates it? What does IP3 do?
When G protein is activated, it recruits the transmembrane phospholipase C (PLC) to cleave phosphotidyl inositol (PIP) into IP3 and DAG.
IP3 activates vesicles to release their Ca2+, which stimulates contractions in muscles
What role does cAMP have in long term memory?
cAMP activates the TF CREB to regulate the ion channels that alter long term memory storage
Give the sequence of events that lead to release of transmitters into the synapse. What role does Ca++ have in this?
Na+ ion channels depolarize cell membrane and send the stimulus to neighboring membranes. As it travels, it reaches the presynaptic end of the axon or dendrite. Ca2+ gated channels are excited to open, and Ca2+ spills into the cell. The Ca2+ binds to SNARE proteins, which facilitate the exocytosis of vesicles full of NTs into the synaptic cleft. The NTs bind to receptors of the postsynaptic axon or dendrite, which can cause EPSP or IPSP.
Compare nicotinic and muscarinic cholinergic receptors in terms of location in the PNS, action and duration of effect.
Nicotinic - neurons and skeletal muscle; ionotropic receptor found on postsynaptic autonomic neurons;
Physostigmine inhibits NT breakdown
Muscarinic - body tissue and CNS neurons; metabotropic receptor that uses G proteins for prolonged stimulus;
Atropine inhibits parasympathetic overload by muscarine
What is the sequence of catecholamine synthesis from tyrosine?
Tyrosine is dehydrogenated by Tyrosine hydroxylase to form DOPA, which is decarboxylated by Dopa decarboxylase to dopamine. Depending on the enzyme activity, dopamine can be hydroxylized to NE for NT, or methylated in a second step to Epi (by PMNT)
--- (Adrenergic receptors)
How do neuropeptides compare to cholinergic and adrenergic transmitters in terms of: location of synthesis and vesiculation, postsynaptic action and duration of effects.
Neuropeptides are synthesized in the cell body of a neuron and travel in vesicles along microtubules of the axon; vesicles are released with other NT-filled vesicles, but at a lower volume; causes a long-term change in ion channels, transcription, etc. Enzymes break down neuropeptides slowly.
Describe the neural hierarchy of the ANS starting from the limbic system to the target structures of the autonomic nerves.
Nerves extend from the limbic system of the hypothalamus to nuclei within the spinal cord out the ventral root and into the spinal nerves, and end the presynaptic track at the ganglia. The postsynaptic axon entends to the effector muscle, which includes viscera, muscle, and skin.
(does not receive input from the spinal cord)
Compare how motor neurons and postganglionic sympathetic neurons innervate their target tissues.
Motor neurons are real straightforward - the axon of a cell body extends all the way from the spinal cord to the effector muscle using ACh NTs
Postganglionic sympathetic neurons extend to the effector and stimulate it with NE; there are also non-specific varicosities that dump out NE to nearby tissue
If a medicine inhibited acetylcholine esterase, what impact would there be on the innervation of muscle and the activity of sympathetic and parasympathetic systems?
Acetylcholine esterase breaks down ACh, so ACh would remain stuck to the receptors and the stimulus would continue. So it would cause an irritability of continuous stimulus to the muscles (tetanus?)
If a medicine specifically activated nicotinic receptors, what would be the impact on the motor and autonomic activities?
Nicotinic receptors are found at the target cell in motor transmissions and in the postganglionic neurons of ANS nerves. If a medicine blocked N receptors, stimuli would be unable to transfer to the target.
The inhibitor Physostigmine is used to treat myasthenia gravis
If a medicine specifically blocked muscarinic receptors, what would be the impact on the motor and autonomic activities?
a. Sedation centrally
b. Blurred vision
c. Dry mouth
f. Urinary retention
All of your parasympathetic responses (rest and digest) would not be stimulated, and lots of terrible things happen
What are the dorsal/ventral roots?
The ventral root and dorsal root are the nerve fibers that converge together to enter into the dorsal horn and exit the ventral horn
SAME DAVE = Afferent Dorsal Sensory; Efferent Ventral Motor
What structures are located in the dorsal root? What are in the ventral root?
Dorsal root contains the dorsal root ganglion, which is sensory nerve cell bodies, a pseudo-unipolar nucleus, and central/peripheral branches
The ventral root contains axons of the motor neurons whose cell bodies exist in the spinal cord
What are the dorsal/ventral rami?
The roots converge to form the spinal nerve, which then converges into the ventral rami, which innervates most of the muscle and skin of the anterior side, and dorsal rami, which innervates the back skin and muscle
Distinguish between nerve trunk pain and dysesthetic pain.
Nerve trunk pain: a localized feeling of pain caused by what is thought to be dysfunctioning nociceptors
Dysesthetic pain: feeling of discomfort and pain away from the area of damage; thought to be the axons of nociceptors that are damaged
What does the presence of cholesterol have on the cell membrane?
Cholesterol controls the permeability of small water-soluble molecules into the cell from the membrane
What are lipid rafts?
Lipid rafts are cholesterol and sphingolipid complexes that can "glide" over the membrane. They are thought to be involved in cholesterol transportation and signal transduction.
What is the sodium-potassium pump and how does it work?
The pump is the continuously closed conformation of Na+ channels K+ leakage channels that allows an axon to maintain a -70 mV interior that is more negative than the external environment; essential for action potentials.
What is the dominant ion that determines the membrane potential at rest and why is it so?
K+ because it's -79 mV, so much more influence
Why do K+ ions leak out of the cell?
K+ is more concentrated in the membrane and the open channel allows K+ to leak out toward a lower gradient. However, Na+ makes the outside very positive, so K+ is not quick to escape the membrane
How do lidocaine and Ca++ alter excitability?
Lidocaine binds to the proteins that open and close Na+ ion channels. When the gate is opened, the lidocaine quickly shuts the channel off and repolarization is slowed so that APs occur at a slower rate (numbs sensory nerves)
Ca++ increases hyperpolarization by activating K+ gated channels and inhibiting Na+ from entering the membrane. Nerves lose their excitability when there's too much Ca2+, but become irritant if there's too little Ca2+. Good balance = proper excitability.
What is the difference between absolute and relative refractory periods?
Absolute refractory period occurs when the Na+ channel remains closed despite AP stimulus; APs can only stimulate the gate when the period is complete
Relative refractory period has open K+ gated channels effluxing K+; however, a stimulus stronger than the first may overcome the threshold to stimulate another action potential
Describe the types of ion channels found in nodes of Ranvier and the intermodal regions of the axons.
the nodes of Ranvier contain voltage-gated channels; the Schwann cell region of the axon only contain nongated K+ channels; saltatory conduction
What are IPSPs in terms of transmitter, receptor, postsynaptic action and impact on the initial segment?
IPSPs may be stimulated by GABA, gamma-aminobutyric acid, or glycine that bind to ionotropic receptors to open K+ and Cl- channels. This hyperpolarizes the cell so that more stimulus is needed to fire an AP to its effector. (postsynaptic cell bodies)
What is CREB?
CREB: cAMP response-element binding: a receptor for cAMP; activated, becomes a TF that alters ion channels
What is the difference between neurons that use norepinephrine as transmitter versus those that use epinephrine?
Neurons can use epinephrine as endocrine NTs; NE is both hormone and NT
What are the specific locations of the preganglionic and postganglionic neuron cell bodies of the two parts of the autonomic nervous system?
Sympathetic: short presynaptic axon located along the spine, from T1-L2; long postsynaptic axons in cell body ganglia or adrenal medulla
Parasympathetic: long presynaptic axons located in the cranial nerves and S2-4; short postsynaptic axons near to effectors
THIS SET IS OFTEN IN FOLDERS WITH...
OS - Study Questions Test 2
Week 4: Neurons
neurology SF Test 4
YOU MIGHT ALSO LIKE...
Chapter 11 A+P
Chapter 11 Review Study Guide
OTHER SETS BY THIS CREATOR
Full Neuro Exam
MSK MANIPULATIONS AND ASSESSMENT