What neurotransmitter is released by sympathetic nerves?
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Norepinephrine.
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What neurotransmitter is released by sympathetic nerves?
Norepinephrine.
What types of body activities does the lower brain level control?
Subconscious body activities.
What type of neurons does the anterior horn contain?
Motor neurons that affect axial muscles.
What is the nature of the summated postsynaptic potential often observed?
Excitatory in nature but has not reached threshold levels.
What is synaptic fatigue?
Exhaustion of the stores of transmitter in synaptic terminals.
What is an inhibitory post-synaptic potential (IPSP)?
An IPSP is a hyperpolarization of the post-synaptic cell that depresses excitability.
What are the four types of sensory information processed by the Sensory Division of the nervous system?
Tactile, visual, auditory, olfactory.
What neurotransmitter do all postganglionic parasympathetic nerves release?
Acetylcholine
What is the function of the anterior root?
It contains motor neurons that affect axial muscles.
What types of circuits are contained within the spinal cord?
Walking circuits, withdrawal circuits, support against gravity circuits, and circuits for reflex control of organ function.
What is the effect of synaptic fatigue on areas of the nervous system?
It causes areas of the nervous system to lose excitability after a while.
Which structures are included in the lower brain level?
Medulla, pons, mesencephalon, hypothalamus, thalamus, cerebellum, and basal ganglia.
How do dendrites transmit signals?
Dendrites transmit signals by electrotonic conduction, which is the transmission of current by conduction in the fluids of the dendrites.
What function do walking circuits in the spinal cord serve?
They help in the coordination and control of walking movements.
Do dendrites transmit action potentials?
No, dendrites do not transmit action potentials. They have few voltage-gated Na+ channels.
What is the role of the spinal cord level beyond being a conduit for signals?
Integration of signals from the periphery of the body to the brain and vice versa.
What is another name for the anterior horn?
Anterior column or ventral horn.
What is required to reach the threshold for firing in a neuron?
Simultaneous firing of many synapses.
What is the purpose of withdrawal circuits in the spinal cord?
They are involved in reflex actions to withdraw from harmful stimuli.
What happens to the post-synaptic cell during hyperpolarization?
The post-synaptic cell is hyperpolarized, which depresses excitability and is inhibitory.
What is the function of the posterior horn?
It receives sensory information.
What does it mean when a neuron is said to be facilitated?
The potential is nearer the threshold for firing than normal but not yet to the firing level.
How do support against gravity circuits in the spinal cord function?
They help maintain posture and support the body against gravity.
Can IPSPs summate?
Yes, IPSPs can summate.
What is the primary function of the Integrative Division of the nervous system?
To process information and create memory.
What are the two types of motor fibers involved in the skeletal motor nerve axis?
Alpha motor fibers and gamma motor fibers.
What is the role of the stretch receptor fiber in the skeletal motor nerve axis?
The stretch receptor fiber detects muscle stretch and sends signals to the spinal cord to adjust muscle tension.
How does the rate of terminal stimulation affect the postsynaptic potential?
The more rapid the rate of terminal stimulation, the greater the postsynaptic potential.
What neurotransmitter do sympathetic nerves release at their nerve endings?
Norepinephrine
Where are muscarinic receptors found?
On all effector cells stimulated by postganglionic parasympathetic fibers.
What are some examples of subconscious body activities controlled by the lower brain level?
Arterial pressure, respiration, equilibrium, feeding reflexes, and emotional patterns.
What is the primary function of dendrites in neurons?
Dendrites allow signal reception from a large spatial area, providing an opportunity for summation of signals from many presynaptic neurons.
Why is it easier to stimulate a facilitated neuron with subsequent input?
Because the potential is nearer the threshold for firing.
What happens when excitatory synapses are repetitively stimulated at a rapid rate?
The rate of postsynaptic discharge becomes progressively less.
What causes EPSPs and IPSPs?
EPSPs and IPSPs result from increases in membrane permeability.
What is the main role of the Motor Division in the nervous system?
To respond to and move about in our environment.
What substances does the adrenal medulla release when stimulated?
Epinephrine (80%) and norepinephrine (20%).
What effect does the parasympathetic nervous system have on the heart?
It decreases heart rate.
What neurotransmitter is released by parasympathetic nerves?
Acetylcholine.
Which postganglionic sympathetic nerves do not release norepinephrine?
Nerves to sweat glands, piloerector muscles, and select blood vessels
Can excitation of a single presynaptic neuron on a dendrite induce an action potential (AP) in the neuron?
No, excitation of a single presynaptic neuron on a dendrite will almost never induce an AP in the neuron.
What is the role of circuits for reflex control of organ function in the spinal cord?
They regulate reflex actions that control various organ functions.
What physiological changes occur during mass sympathetic discharge?
Increase in arterial pressure, heart rate and contractility, blood flow to muscles, blood glucose, metabolic rate, muscle strength, mental activity, and blood coagulation.
What is the primary function of the skeletal motor nerve axis in the nervous system?
To control voluntary muscle movements.
What effect does the sympathetic nervous system have on blood vessels?
It causes vasoconstriction.
What can rapidly repeating firings of a small number of terminals achieve?
They can summate to reach the threshold for an action potential (AP).
What are nerves called that release norepinephrine?
Adrenergic nerves
Where are sympathetic ganglia located?
Close to the spinal cord.
What neurotransmitter is released by all preganglionic sympathetic and parasympathetic nerves?
Acetylcholine
What are the components of acetylcholine?
Acetyl CoA and choline
Which type of transmitters are associated with ion channels in the postsynaptic membrane?
Small molecule transmitters (e.g., Ach, NE).
How long do the responses from the 2nd messenger system last?
Prolonged responses.
What is the function of membrane enzymes in the second messenger system?
They help in the conversion of ATP to cAMP or GTP to cGMP, which act as secondary messengers.
What type of receptor is responsible for detecting pressure?
Pacinian corpuscle (expanded tip receptor).
What does the upper record in the diagram represent?
The upper record is from the presynaptic cell.
What is post-tetanic facilitation?
Enhanced responsiveness following repetitive stimulation.
What is the function of the axon in a neuron?
It is the effector part of the neuron.
What is the value of an excitatory postsynaptic potential (EPSP)?
+20 mV
What happens to a neuron when it reaches an IPSP?
The neuron becomes inhibited.
What is the concentration of Cl- inside and outside the neuron?
Inside: 8 mEq/L, Outside: 107 mEq/L
What is one peptide that acts on the gut and brain listed in the image?
Leucine enkephalin.
Why is the development of synaptic fatigue considered a protective mechanism?
It protects against excess neuronal activity.
What should you consider when thinking about the ions involved in synaptic responses?
You need to consider the equilibrium potentials of the ions.
What is the effect of the substances released by the adrenal medulla?
They cause prolonged activity, including stimulation of cardiovascular function and metabolic rate.
What effect does the parasympathetic nervous system have on blood vessels?
It causes some vasodilation.
What mechanism underlies facilitation at the squid giant synapse?
Prolonged elevation of presynaptic calcium levels following synaptic activity.
Which two types of receptors does acetylcholine excite?
Nicotinic and muscarinic receptors.
Where are parasympathetic ganglia located?
In the effector tissues.
What is the typical excitatory postsynaptic potential (EPSP) generated by each terminal on a dendrite?
Each terminal on the dendrite accounts for about a 0.5 - 1.0 mV EPSP.
What is the primary function of small molecule, rapidly acting transmitters?
To cause most acute responses of the nervous system.
What role does the G-protein play in synaptic transmission involving a second messenger?
The G-protein, upon activation, exchanges GDP for GTP and then activates other intracellular processes.
What is one path that axons of the sympathetic system can take after entering the sympathetic chain via the white ramus?
They can terminate in the sympathetic chain.
What is the role of the muscle spindle in the somatosensory system?
It acts as a kinesthetic receptor.
What is an EPSP?
An excitatory postsynaptic potential (EPSP) is an electrotonic response that decays with an exponential time course.
What effect does the build-up of calcium have in post-tetanic facilitation?
It causes more vesicular release of the transmitter.
What are the projections from the soma called?
Dendrites.
What is the resting membrane potential of a neuron?
-65 mV
What happens to a neuron when it reaches an EPSP?
The neuron becomes excited and the action potential spreads.
What is the concentration of K+ inside and outside the neuron?
Inside: 120 mEq/L, Outside: 4.5 mEq/L
What is the purpose of the mass sympathetic discharge?
To prepare the body for vigorous activity needed to deal with a life-threatening situation.
Which part of the brain is involved in the skeletal motor nerve axis?
The motor area of the brain.
What is the function of the muscle spindle in the skeletal motor nerve axis?
The muscle spindle detects changes in muscle length and helps regulate muscle contraction.
How long does a neurotransmitter open a membrane channel?
About 1 msec.
What happens to the amount of facilitation as the interval between stimuli increases?
The amount of facilitation decreases as the interval between stimuli increases.
What neurotransmitter do parasympathetic nerves release at their nerve endings?
Acetylcholine
What is the characteristic of sympathetic pathways in terms of fiber length?
They have short preganglionic fibers and long postganglionic fibers.
From which amino acid are norepinephrine and epinephrine synthesized?
Tyrosine
What receptors does norepinephrine stimulate?
Alpha and beta adrenergic receptors.
Where is the cell body of the preganglionic axon located?
In the brain stem or spinal cord.
Where is the cell body of the postganglionic neuron located?
Within the autonomic ganglia.
What initiates the synaptic transmission involving a second messenger?
The binding of a transmitter substance to a receptor protein.
Where are visceral motor neurons of the sympathetic system located?
In the intermediolateral horn of the spinal cord from T-1 to L-2.
Which receptor is responsible for detecting touch?
Meissner's corpuscle.
What is the mechanism thought to be behind post-tetanic facilitation?
Build-up of calcium ions in the presynaptic terminals.
What membrane potential is reached during an IPSP?
-70 mV
What is the concentration of Na+ inside and outside the neuron?
Inside: 14 mEq/L, Outside: 142 mEq/L
What is another name for the stress response involving mass sympathetic discharge?
The fight or flight response.
What is the adrenal medulla described as?
A large sympathetic ganglion.
How does the adrenal medulla help the body?
It helps the body deal with stress.
How long does a postsynaptic potential (EPSP or IPSP) last?
About 15 msec.
How does the presynaptic membrane potential change during facilitation?
The presynaptic membrane potential shows increased activity following closely spaced action potentials.
Where are nicotinic receptors found?
In synapses between the pre- and post-ganglionic neurons and at the neuromuscular junction.
What is the characteristic of parasympathetic pathways in terms of fiber length?
They have long preganglionic fibers and short postganglionic fibers.
How can an action potential (AP) be induced through spatial summation?
When multiple terminals are excited simultaneously, the EPSP generated may exceed the threshold for firing and induce an AP.
What is the nature of the response produced by ion channels in the postsynaptic membrane?
Rapid response – short lived.
What type of responses are produced by the 2nd messenger system in the postsynaptic membrane?
Multiple responses.
What are the effects of beta 2 receptor activation?
Beta 2 receptor activation causes bronchial dilation, dilation of blood vessels in skeletal muscles, calorigenesis, and glycogenolysis.
What happens when the G-protein is activated in synaptic transmission?
It can open ion channels, activate enzymes, or initiate gene transcription.
What is the second path that axons of the sympathetic system can take after entering the sympathetic chain via the white ramus?
They can ascend or descend a few segments before terminating.
Which part of the brain is involved in the somatosensory pathway after the spinal cord?
Medulla, followed by the pons, cerebellum, and thalamus.
Why are there no action potentials in the postsynaptic cell in the diagram?
None of the EPSPs reached the threshold.
What is synaptic delay?
The process of neurotransmission takes time, and from the delay, one can calculate the number of neurons in a circuit.
What is the value of an inhibitory postsynaptic potential (IPSP)?
-5 mV
What is the membrane potential (Vm) of a typical neuron?
-65 mV
What are the long-term changes caused by neuropeptides?
Changes in the number of neuron receptors, long-term opening or closure of ion channels, and changes in the number and sizes of synapses.
Name two neuropeptides from other tissues listed in the image.
Angiotensin II and Bradykinin.
What structures are involved in the motor nerve pathway to muscles?
Motor area, caudate nucleus, putamen, globus pallidus, subthalamic nucleus, thalamus, cerebellum, and bulboreticular formation.
What effect does the sympathetic nervous system have on the heart?
It increases the rate and contractility.
What effect does a second opening of the same membrane channel have on the postsynaptic potential?
It can increase the postsynaptic potential to a greater level.
How does the postsynaptic membrane potential change during facilitation?
The postsynaptic membrane potential shows increased response following closely spaced action potentials.
What are nerves called that release acetylcholine?
Cholinergic nerves
What is spatial summation in the context of postsynaptic potentials?
Spatial summation refers to the process where excitation of multiple presynaptic neurons on a dendrite can collectively induce an action potential (AP) in the neuron.
What is the synthesis pathway for norepinephrine and epinephrine?
Tyrosine → DOPA → Dopamine → Norepinephrine
What does the motor system of the autonomic nervous system control?
Visceral organs, blood vessels, and secretory glands.
What is the characteristic of the axon of the visceral motor neuron?
It is thinly myelinated and projects to autonomic ganglia.
What is the characteristic of the axon of the postganglionic neuron?
It is unmyelinated and projects to the visceral effector cell.
What are the potential outcomes of G-protein activation in synaptic transmission?
Opening of ion channels, activation of intracellular enzymes, and activation of gene transcription.
What is the third path that axons of the sympathetic system can take after entering the sympathetic chain via the white ramus?
They can exit via a splanchnic nerve and terminate in a prevertebral ganglia.
Why is the last EPSP larger in the diagram?
The last EPSP is larger because it occurs before the previous EPSP has fully decayed, demonstrating temporal summation.
What are the three major components of a neuron?
Soma, Axon, and Dendrite.
What is the function of dendrites in a neuron?
They are the sensory portion of the neuron.
What ion influx is associated with an excitatory postsynaptic potential (EPSP)?
Na+ influx
What is the equilibrium potential for potassium (EK)?
-86 mV
What is one effect of neuropeptides on neuron receptors?
Neuropeptides can cause changes in the number of neuron receptors.
What types of ion channels are involved in the actions of transmitter substances on the postsynaptic membrane?
Cation channels and Anion channels.
Where are alpha receptors located and what is their function?
Alpha receptors are located on blood vessels and cause vasoconstriction.
What type of substances are involved in the 2nd messenger system in the postsynaptic membrane?
Neuropeptides.
What is the role of ATP or cAMP in the second messenger system of synaptic transmission?
They act as secondary messengers that further propagate the signal within the cell.
What are the main components of the somatosensory axis of the nervous system?
Skin, spinal cord, medulla, pons, cerebellum, thalamus, somesthetic areas, motor cortex.
Where are somesthetic areas located in the brain?
In the cerebral cortex.
What is temporal summation?
Temporal summation is the successive EPSPs from the same synapse occurring before the previous EPSP has fully decayed.
What is the main body of a neuron called?
Soma.
What ion influx and efflux are associated with an inhibitory postsynaptic potential (IPSP)?
Cl- influx and K+ efflux
What is the equilibrium potential for sodium (ENa)?
+61 mV
How do neuropeptides affect ion channels?
Neuropeptides can cause long-term opening or closure of ion channels.
Which neurotransmitter belongs to Class I of small molecule, rapidly acting transmitters?
Acetylcholine.
What is the effect of beta 1 receptor activation?
Beta 1 receptor activation causes an increase in heart rate and contractility.
How does the activation of gene transcription affect the cell in synaptic transmission?
It leads to protein synthesis and structural changes within the cell.
Which part of the nervous system is responsible for processing pain, cold, and warmth?
Free nerve endings in the skin.
What is spatial summation?
Spatial summation is when EPSPs from distant synapses overlap.
Which part of the neuron extends from the soma to the synaptic terminal?
Axon.
What membrane potential is reached during an EPSP?
-45 mV
What is the equilibrium potential for chloride (ECl)?
-70 mV
What changes can neuropeptides cause in synapses?
Neuropeptides can cause changes in the number and sizes of synapses.
