Lecture Exam 4
The sympathetic nervous system mediates the ________ response as a consequence of its ability to prepare the body to cope with threatening situations.
"fight-or-flight"
List four distinct functions of the hypothalamus.
1) controls body temperature 2) regulates hunger 3) regulates blood pressure 4) perceives pleasure, fear, rage, ect.
What seven areas of the body is the hypothalamus in control of?
1. ANS. 2. Center of emotional responses. 3. Body temperature regulation. 4. Regulation of food intake. 5. Regulation of water balance and thirst. 6. Regulation of the sleep-wake cycles. 7. Control of the endocrine functions.
In what ways are the autonomic nervous system and the somatic nervous system different?
1. The autonomic is a two-neuron system; the somatic uses one. 2. The autonomic uses smaller neuron fibers (type B or C); the somatic generally uses the type A fibers. 3. The autonomic is mostly involuntary and automatic; the somatic is voluntary. 4. The autonomic uses several neurotransmitters and many receptor types; the somatic uses only one. 5. The autonomic is a slow system; the somatic is a fast system. 6. The autonomic has opposing forces to regulate the body; the somatic does not.
How are the sympathetic and parasympathetic divisions anatomically different?
1. They have unique origin sites. 2. They have different lengths of pre and post ganglionic axons. 3. Their ganglia are located in different areas.
In what ways are the autonomic nervous system and the somatic nervous system different? Put the following events in proper order: 1) Calcium ions enter the presynaptic neuron axonal terminal 2) Neurotransmitter binds to postsynaptic membrane receptors 3) Depolarization or hyperpolarization of post-synaptic membrane 4) Opening of chemically-gated ion channels in the post-synaptic membrane 5) Nerve impulse arrives at the axonal terminal of presynaptic neuron 6) Neurotransmitter is released into synaptic cleft
5-1-6-2-4-3 [Depolarization or hyperpolarization in the final step depends on which type of channels are opened by neurotransmitter action]
Entry of _____ ions into the axonal termini triggers the release of neurotransmitter.
Ca2+
Action potentials can be generated by virtually all cells of the body because all cells possess cell membranes.
F
In contrast to the parasympathetic division, the sympathetic division has numerous postganglionic neurons in the gray matter of the spinal cord.
F
Projection fibers in the brain mainly connect the right and left hemispheres.
F
Somatosensory neurons that project from the thalamus to the cerebral cortex are termed first-order.
F
Sorting of sensory information and relaying it to the appropriate cerebral sensory area occurs in the hypothalamus.
F
Strong stimuli cause the amplitude of action potentials generated to increase.
F
The patellar stretch reflex results in contraction of flexor muscles.
F
The reticular formation acts as our emotional brain.
F
Action potentials can be generated by virtually all cells of the body.
False
Sorting of most sensory information and relaying it to the appropriate cerebral sensory area occurs in the pons.
False
The patellar stretch reflex results in contraction of flexor muscles.
False
A neuron actively transports chloride ions out of the cell. Opening of chloride channels in response to a neurotransmitter binding to receptors on this neuron will produce (an IPSP / membrane stabilization) thereby (exciting / inhibiting) the neuron.
IPSP : inhibiting
How will two bursts of action potentials that are traveling along the same neuron induce a temporal summation?
If the second burst reaches the axon terminal to induce the release of neurotransmitter before the first has decayed, the postsynaptic membrane will not have completely returned to resting membrane potential, thereby increasing the magnitude of the change in membrane potential relative to a single burst.
Why does a hyperpolarization phase generally follow a repolarization phase in an action potential?
Immediately after an action potential the potassium gates, being slow gates which do not respond to change in the electrical charge, allow additional K+ ions to flood into the cell. These K+ ions decrease the positive ion concentration momentarily below the normal -70mV and thus hyperpolarize the cell.
State the role of the limbic system. List four brain areas associated with the limbic system.
It generates emotional responses 1) hippocampus 2) amygdala 3) hypothalamus 4) olfactory cortex
Describe the structure of a neuron and the important consequences of that arrangement.
Neurons are composed of a cell body (or soma), where a majority of their cellular organelles are located, and several projections from the cell body that are classified as dendrites and axons based upon their function. The cell body itself is incapable of generating an action potential. This inability derives from the absence of voltage-dependent sodium channels in the membrane of the cell body that are required for an action potential to be generated. Projecting from the cell body are a number of dendrites that receive synaptic input from axon terminals from other neurons. Thus, dendrites receive information from other cells while axons transmit that information. At these axodendritic synapses, neurotransmitters are released from the axon terminals onto the dendrites to generate a change in membrane potential. The graded change in membrane potential at the dendrite decays as it travels across the cell body from its source. This allows for the integration of numerous synaptic inputs onto one cell body. The final integration occurs at the axon hillock. Within this structure, the voltage-dependent sodium channels required for an action potential are present in their greatest concentration. Thus when the axon hillock is depolarized above threshold, an action potential will be generated. Once initiated, the action potential will move along the axon in one direction. That action potential will travel along the axon until it reaches the axon terminal, where a synapse is formed for the transfer of the information on to the next neuron or effector organ.
Describe one distinctive function of each of the following: Primary somatosensory regions Primary motor cortex Cerebellum Medulla oblangata Thalamus Midbrain Premotor cortex Prefrontal cortex Sensory association areas Wernike's and Broca's regions Limbic system Reticular activating system Commisure Association Projection fibers
Primary somatosensory regions: capable of spatial discrimination Primary motor cortex: generate neural impulses that control the execution of movement Cerebellum: plays major role in maintaining balance Medulla oblongata: houses the reflex centers for respiration and cardiovascular functioning Thalamus: mediates sensation, motor activities, arousal, memory and learning Midbrain: serves in motor movement, auditory and visual processing Premotor cortex: helps plan movements Prefrontal cortex: planning complex cognitive behavior, personality expression, decision making and moderating social behavior Sensory association areas: forms comprehensive understanding of stimulus Broca's regions: speech preparation and production Wernike's regions: speech comprehension Limbic system: generates emotional responses Reticular activating system: sends impulses to the cerebral cortex to keep it conscious and alert Commissure: connect corresponding grey areas of the two hemispheres Association: connect different parts of the same hemisphere Projection fibers: enter the hemispheres from lower brain or cord centers
What are the basic divisions of the peripheral nervous system?
Sensory and motor divisions. Motor has two divisions: the somatic and autonomic. The autonomic has two divisions: the sympathetic and parasympathetic.
A graded potential that is the result of a neurotransmitter released into the synapse between two neurons is called a postsynaptic potential.
T
Acetylcholine is the substance released by the axonal endings of all somatic efferent fibers and by all parasympathetic nerve fiber endings.
T
Cell bodies of sensory neurons may be located in ganglia lying outside the central nervous system.
T
Cell bodies of the somatic motor neurons of the spinal nerves are located in the ventral horn of the spinal cord.
T
Cerebrospinal fluid circulates within the ventricles of the brain and in the subarachnoid space outside the brain.
T
During depolarization, the inside of the neuron's membrane becomes less negative.
T
Efferent nerve fibers may be described as motor nerve fibers.
T
Large-diameter nerve fibers conduct impulses faster than small-diameter fibers.
T
The adrenal medulla can be described as both an endocrine organ and as a sympathetic ganglion.
T
The autonomic nervous system consists of an efferent pathway with two peripheral neurons that travel in series from the central nervous system to the effector organ.
T
The autonomic nervous system is also known as the involuntary nervous system.
T
The autonomic nervous system may cause activation or inhibition, depending on the division that is active and the target that is affected.
T
Thermoregulatory responses to increased heat are mediated by the sympathetic nervous division.
T
Voltage is always measured between two points and may be called the potential between these two points.
T
Describe the voltage gating of ion channels and how this plays a role in an action potential.
The action potential is generated by the activity of a specific type of sodium channel that has very unique gating properties. There are two gates on these sodium channels; one is the activation gate and the other is the inactivation gate. Both of these gates are activated by membrane depolarization. However, the activation gate is faster acting than the inactivation gate. Thus, as the membrane depolarizes, the activation gate is opened and the inactivation gate will close the channel shortly thereafter. This short duration of time in which the sodium channel remains open is long enough to cause a large change in membrane potential due to the strong electrochemical driving force for sodium to move into the cell. This creates a positive feedback loop where the activation of one sodium channel causes the membrane to depolarize further, thereby opening other sodium channels. This regenerative process in the sodium channel is activated to produce an action potential only if the change in membrane potential is above threshold. At the same time that depolarization activates the sodium channels, there are potassium channels that are sensitive to depolarization and are stimulated to open. These channels are slow-acting as well, with respect to the activation gate of the sodium channel, meaning that the potassium channels open after a short delay. Thus, the action potential is generated by the opening of enough sodium channels, which rapidly depolarizes the membrane. That depolarization is reversed by the closure of the sodium channel's inactivation gate. The potassium channel opens more slowly and remains open for a longer period of time. The delayed opening of the potassium channel increases the rate of repolarization of the membrane following the upstroke of the action potential, and the slow closure results in the after-hyperpolarization of the membrane below resting membrane potential.
Describe the organization of the nervous system, including a description of the different branches.
The entire nervous system is organized into two main divisions: the central nervous system and the peripheral nervous system. The central nervous system (the brain and spinal cord) receives sensory input from the body, which it integrates to determine whether a response is warranted. Within the central nervous system, learning, memory, emotion, and other complex functions occur. The peripheral nervous system is divided into two main divisions: the afferent and efferent limbs. The afferent limb detects sensory (external) and visceral (internal) information and sends it to the central nervous system. The efferent limb sends information to the effector organ from the central nervous system to initiate a response. The efferent limb can be divided into two branches: the autonomic nervous system and the somatic nervous system. The somatic nervous system transmits information to skeletal muscle, whereas the autonomic nervous system sends information either through the sympathetic or parasympathetic nervous systems, which tend to be counterregulatory (produce the opposite effects). The autonomic nervous system is not under voluntary control.
A number of modified epithelial cells, acting as sensory receptors, innervate a single neuron. Some of these cells release excitatory neurotransmitters, while others release inhibitory neurotransmitters. How are these responses integrated by the neuron to determine whether an action potential will be generated or not?
These modified epithelial cells will synapse with the dendrites on the body of a neuron. As neurotransmitters are released onto those dendrites, a graded potential is produced at the postsynaptic membrane that will either depolarize (excitatory postsynaptic potential) or hyperpolarize (inhibitory postsynaptic potential) the membrane. From the synapse, the graded potential will decay as it moves along the membrane of the cell body. In contrast, action potentials do not decay as they move along an axon. Whether or not an action potential is generated is determined by the magnitude of the membrane potential once it reaches the axon hillock. The axon hillock contains the ion channels that are neccessary for the generation of an action potential. Thus, if the graded potential that originates at the dendritic synapse and travels along the cell body is still above threshold once it reaches the axon hillock, an action potential will be generated. Two types of integration, referred to as summation, are spatial and temporal. Spatial summation refers to a situation where two synapses are activated at the same time such that the graded potential generated is the sum of the two inputs. Temporal summation refers to two impulses from the same neuron where the second reaches the synapse before the first has decayed completely. However, the process of summation does not necessarily lead to the generation of an action potential. The generation of an action potential is dependent upon the nature of the impulses that are being summed (excitatory or inhibitory) and the magnitude of those impulses.
Ascending somatosensory neurons that project from the thalamus to the cerebral cortex are termed third-order.
True
Spinocerebellar tracts carry sensory information critical to the coordination of muscle movements.
True
The autonomic nervous system controls the function of BOTH involuntary muscles and glands.
True
The hypothalamus is critical for the communication between the nervous and endocrine systems.
True
Thoughts are generated in the frontal lobe.
True
Distinguish between white matter and gray matter in the central nervous system as to components and function.
White Matter: myelinated and nonmyelinated axons; connection between processing areas Grey Matter: short, nonmyelinated neurons and cell bodies; form areas that perform information processing
The part of the peripheral nervous system which sends sensory information from receptors to the brain or spinal cord is termed:
afferent
The subarachnoid space lies between what two layers of meninges?
arachnoid and pia
A neuron that has as its primary function the job of connecting other neurons is called a(n) ________.
association neuron
The sympathetic and parasympathetic are subdivisions of the ________ nervous system.
automatic
The term central nervous system refers to the ________ and _________.
brain and spinal cord
The term central nervous system refers to the:
brain and spinal cord
The fourth ventricle is continuous with the ________ of the spinal cord.
central canal
Cerebrospinal fluid is formed within what structures?
choroid plexus
The sodium inactivation gate (opens / closes) with depolarization.
closes
What ion channel(s) is/are responsible for event B in the figure above?
closure of the sodium channels and opening of the potassium channels
The large commissure that connects the right and left sides of the brain is called the ________.
corpus callosum
The cranial nerve that innervates most of the viscera in the thoracic and abdominal cavities is the ________.
cranial nerve X or vagus nerve
The ________ includes the thalamus, hypothalamus, and epithalamus.
diencephalon
Sensory neurons enter the spinal cord via the ________ horn.
dorsal
The central sulcus separates which lobes?
frontal from parietal
Collections of nerve cell bodies outside the central nervous system are called ________.
ganglia
The autonomic nervous system controls cardiac muscle, smooth muscle, and _________.
glands
________ potentials are short-lived, local changes in membrane potential that can be either depolarized or hyperpolarized.
graded
Describe the event C indicated in the figure above and how that event is initiated.
graded potential (depolarization; EPSP) that could have resulted from the opening of sodium channels; this is a subthreshold depolarization that did not trigger an AP
List three organs controlled by the vagus nerve (cranial nerve X).
heart, lungs, digestive tract
In the figure above, if the direction of event C was reversed (hyperpolarization), how would this affect the ability of the postsynaptic membrane to generate an action potential?
hyperpolarization will reduce the likelihood that an action potential will be generated
The body's thermostat is located in what brain structure?
hypothalamus
Following the opening of the activation gate of the sodium channel, the ________ gate closes shortly thereafter.
inactivation
Hyperpolarization is associated with a(n) __________ postsynaptic potential.
inhibitory
The vital centers for the control of heart rate, respiration, and blood pressure are located in the ________.
medulla
The basic divisions of the peripheral nervous system are the sensory and __________ divisions.
motor
Both motor neurons and interneurons are generally:
multipolar
A gap between Schwann cells in the peripheral nervous system is called a(n) ________.
node of ranvier
Schwann cells are functionally similar to ________ what other type of neuroglia?
oligodendrocytes
The type of glial cell that that forms myelin sheaths within the central nervous system are called:
oligodendrocytes
What ion channel(s) is/are responsible for event A in the figure above?
opening of sodium channels
Long preganglionic fibers are characteristic of neurons within the ________ division of the ANS.
parasympathetic
The three meninges from neural tissue to bone are ________, ________, and ________.
pia mater, arachnoid mater, dura mater
At rest, the plasma membrane is more permeable to (sodium / potassium).
potassium
Immediately after an action potential has peaked, which type of channels open?
potassium
Which ion channel(s) are responsible for event D in the figure above?
potassium channels
Spinocerebellar tracts carry________ inputs to the cerebellum.
proprioceptive inputs to the cerebellum
The ________ carries projection fibers that travel from the primary motor cortex to the spinal cord.
pyramidal tract
The two longitudinal ridges on the medulla oblongata where many descending fibers cross over are called the ________.
pyramids
The region of the brainstem important in the sleep-wake cycle, the arousal of the cerebral cortex, and in consciousness is known as the ________.
reticular formation
Bipolar neurons are commonly found in what structure associated with the eye?
retina
During the rapid depolarization phase of an action potential, the plasma membrane is more permeable to (sodium / potassium).
sodium
That part of the nervous system that is voluntary and conducts impulses from the CNS to the skeletal muscles is the ________ nervous system.
somatic
In the figure above, if S2 indicated a stimulus from a different source, and S1 occurred coincident with S2, what type of summation has been generated?
spatial
In ascending tracts, information is transmitted from ________ to ________.
spinal cord : brain
Identify the type of summation that is occurring in the figure above, where S refers to a stimulus from one source measured in the postsynaptic membrane.
temporal
When one or more presynaptic neurons fire in rapid order it produces a much greater depolarization of the postsynaptic membrane than would result from a single EPSP; this event is called ________ summation.
temporal
The primary auditory cortex is located in the ________ lobe.
temporal lobe
Second-order neurons of both the specific and nonspecific ascending pathways terminate in the ________.
thalamus
Saltatory conduction is made possible by what structural component associated with the neuron?
the myelin sheath
The level of membrane depolarization required to induce the sodium channel's positive feedback loop is called ________.
threshold
Which type of ion channels are located along the axon membrane?
voltage-gated channels
