3A
Multiple subthreshold neurons firing simulatanously can cause an ________to occur
action potential
If enough neurotransmitters are released in the synaptic cleft, an action potential is intitiaed in an ______________
all or nothing fashion
Synaptic knobs
are the terminal region of axons
AB (mnemonic)
astrocytes -> blood brain barrier
Part of the axon that connects to the soma
axon hillcock
Where is the action potential of a neuron generated?
axon hillcokc
Synapse between cell body and axon is __________
axosomatic
Peripheral nervous system regulates autonomic systems of the body such as :
blood circulation
Nerves :
bundle of fibers of neurons that uses electrical and chemical signals to transmit sensory and motor information from one body part to another
Synapse can be either ________<__________
chemical,electrical
Inner ear consits of
cochlea, and semicircular canals
Retina
cones and rods transduce light into action potential
The sensory neurons are located in the _________
dorsal root ganglia of the spinal cord
Axons transmit information in the form of _______
electrochemical gradients
An _____________synapse causes the postsynaptic neuron to depolarize
exciatatory
In the brain, glutamate is generally an _________neurotransmitter
exciatory
Somatic nervous system:
innervates skeletal muscles, and is responsible for voluntary movements
Three types of sensory receptors to moniter internal and external envionrment
interocepters, proprioreceters, and exteroreceptors
Inside of a neuron is more________than outside
negative
Neurons have a ___________resting potential
negative, around -70mV
The peripherial nervous system consists of :
nerves outside the brain and spinal cord
Chemical synapses are most abundant in _________
nervous system
Ependymal cell function ?
neuroglial cells that line the verticies of the brain and produce cerebralspianl fluid
What happens at the terminal axons ?
neurotransmitters are released into the synapse or synaptic cleft
A neuron can only have __________axon connected to the soma
one, but....axons can branch out
Even at rest, a neuron is _______
polarized
The post synaptic action potential is as large as the ________--
pre-synaptic action potential, that is, no loss of signal strength occurs between cells (as in a electrical impulse)
Chemical synapse:
presynatic axon releases neurotransmitters unidirectionally to post synaptic cell using ion channel or something like G-coupled protein receptor
What happens after proteins are made in the Soma ?
proteins needed in the axons or dendrites are usually transported where they are needed via micortubules
A neuron converts __________into electrochemical signals that are conducted through the nervous system
stimuli
The nervous system enables organisms to recieve and respond to __________from their internal and external envionrments
stimuli
What is the function of glial cells >
supply nutrients and O2 to neurons, ....insulate neurons from each other, destroy pathogens, remove dead neurons, fix neurons to surface
Schawann cells:
supporting cells in the peripheral nervous system
Dendrites receive information from upstream cells through a _________
synapse
Neurotransmitters are stored in vesicles in the ___________
synaptic knob (axon terminal)
Forebrain
telencephalon and diecephalon.....frontal, parietal, temporal, and occipital... cerebral cortex (gray matter) cortex processes and integrates sensory input and motor repsones and is important for memory and createive thought corpus collosum- how left and right hemispheres communicate
Diencephalon contains the _________,_________
thalamus, hypothalamus
A ________synapse causes the post-synpatic neuron to hyperpolarizee
inhibitory
In the Na+/K pump;
3 Na+ are transported out of the cell, and 2K+ are pumped back into the cell
Which of the following cell types in the central nervous system are responsible for cerebrospinal fluid (CSF) production? A ependymal cells B schwann cells C astrocytes D oligodendrocytes
A
After severe head trauma, a patient's co-ordination is severely impaired. Which of the following centers of his brain has most likely been affected? A cerebellum B hypothalamus C amygdala D cerebrum
A, The cerebellum is responsible for coordination and balance. The hypothalamus is largely responsible for homeostasis. The amygdala is largely responsible for emotion and memory association. The cerebrum is responsible for language, memory, olfaction and motor responses.
The area of the brain through which conscious and unconscious sensory signals travel is known as the: A Diencephalon B Brain stem C Cerebellum D Cerebrum
A, The diencephalon is home to the epithalamus, thalamus, and the hypothalamus. It integrates sensory inputs and motor commands.
What is Saltatory Conduction?
Action potential jumps from one node of ravier to the next
Synapse between axon and axon
Axoaxonic
End of the axon where synapse forms:
Axon terminal
In most cases, neurotransmitters result in the propagation of A neurotransmitter gradient through the axon B action potential C neurotransmitter receptor movement from one end of a neuron to the other D propagation of a longitudinal wave along the myelin sheath
B, Neurotransmitters almost always stimulate response in neurons by propagating action potentials down axons.
Which of the following cell types in the perpherial nervous system are responsible for myelination? A ependymal cells B schwann cells C astrocytes D oligodendrocytes
B, Scwann cells myelinate in the perihpery
Synaptic fatigue
Because neurotransmitters are stored in limited quanities, repeated stimulation will eventually start to deplete stores....when depletion occurs, neurons can no longer send a signal
Central nervous system
Brain and spinal cord, gives exective commands
Which of the following cell types in the central nervous system are responsible for myelination? A ependymal cells B schwann cells C astrocytes D oligodendrocytes
D, oligiodendrocytes produce myelin in the central nervous system
A patient with hyperthyroidism elects to have her thyroid removed. Immediately after removal (and before any postoperative actions), which of the following will be most affected? A Control of urination B Control of digestion C Glucose homeostasis D Calcium homeostasis
D, ut of the following choices, the thyroid (and therefore, thyroid removal) plays the largest role in calcium homeostasis. In humans, when the blood calcium level rises above a baseline, the thyroid gland releases calcitonin, causing the blood calcium level to fall. Conversely, when the blood calcium level falls below a baseline, the parathyroid gland releases parathyroid hormones, causing the blood calcium level to rise. Unless there are any postoperative actions after the thyroid removal, expect calcium homeostasis to be most affected.
Exteroceptors
External environment
Which of the following correctly describes where in the eye light is transduced into neural impulses? A The lens and pupil B The iris C The rods and the cones D The cornea
In the eye, the rods and cones are photoreceptor cells that are found throughout the retina. Via photon absorption, these cells convert light - as part of the visible electromagnetic radiation - into changes in membrane potential. The rods are more numerous and are more sensitive than the cones, which provide the eye's color sensitivity. The cornea forms a protective covering on the eye's surface, whereas the iris (with the pupil forming the opening of the iris) regulates the amount of light entering the eye.
What is the purpose of the mylein sheath ?
Keeps ions from leaking out of the axon, and increases speed of the signal
In the nodes of ranvier.....you have diffusion of Na+ and K+ passively and by active transport via :
Na+ K+ pump
Polarized
Negative
Reflex arch
Neural pathway that responds to particular sensory input, in an automatic, reflexive manner (hand on hot stove)
Soma
Neuron cell body
In the peripheral nervous system, which cell myelinates and in turn increases the action potential across a nerve axon? A Microglial cell B Oligodendrocyte C Astrocyte D Schwann cell
Oligodendrocytes provide myelination in the central nervous system but not the peripheral nervous system. Astrocytes and microglial cells are support cells that clean debris from tissue surrounding nervous tissue. Schwann cells are the myelination cells of the peripheral nervous system, and thus (d) is the correct answer.
Cochlea contains
Organ of corti (specialized hair cells )
The middle ear leads to inner ear via
Oval window
What works to bring the cell back to resting potential ?
Passive diffusion and Na+ channel pumps
Oligiodendrocytes
Supporting cells of the central nervous system
Synapse
The gap between teh axon terminals of one cell and the dendries to fhte next cell
Dendritic Spines
The majority of dendrites have synapses on little appendages called dendritic spines. Spines increase surface area, are involved in learning and memory, and are abnormal in several forms of mental retardation
What is accomodation is a neuron?
The thereshold stimlus is reached, but very slowly, so action potential does not occur.
Depolarized
To become less negative
The middle ear is connected to aduitory canal via
Tympanic membrane (eardrum)
A mutation is discovered which results in the myelin sheath overgrowing and covering all the space along the axon where there would normally be Nodes of Ranvier. Which of the following would be expected of such a neuron? A close-to-normal functioning as Nodes of Ranvier are not an essential component of signal propagation down an axon B repeated spontaneous depolarization and signal transmission down the axon C inability to be stimulated by an action potential D inability to propagate an action potential down the axon
Unmyelinated neurons have their entire axons exposed and thus have no Nodes of Ranvier. However, myelinated neurons can propagate their signals only via the Nodes of Ranvier which are the only exposed areas of the axon membrane. If those nodes were covered, the action potential would be unable to propagate down the axon, making (D) the correct answer. (C) is incorrect because while propagation would be prevented, stimulation would not; the neuron can be stimulated at the dendrites and the nerve cell body, and stimulation does not require propagation within the stimulated cell.
Eye anatomy :
eyeball is covered in thick sclera beneath the sclera is the choroid layer (supplys the retina with blood) Innermost layer is retina
electrical synapse cells are joined together by ____________
gap junctions
Astrocyte is a type of :
glial cell
Ependymal cell is a type of :
glial cell
Oligiodendrocyte is a type of :
glial cell
Schwann cell is a type of :
glial cell
Concentration of K+ is ______inside the cell
higher
Concentration of Na+ is _________outside the cell
higher
Dendrites can be
highly branced to recieve information from multiple cells, or one cell
Neurons are :
highly polarized cell
The cell membrane is _________to charged ions
impermeable
The ear transduces sound energy (pressure waves) into_________
impulses (perceived by the brain as sound)
The cerebrum is largely responsible for :
language, memory, olfaction, and motor responses
Neurotrasmitters are stored within vessicles in __________quantities
limited
Concentration of K+ is __________outside the cell
lower
Conentration of Na+ is ___________inside the cell
lower
Rhodopsin
rod pigment, absorbs one wavelenghth
Polysynaptic reflixes
sensory neurons syapse with more than one motor neuron, i.e. withdraw reflex (when a person steps on a nail...the injured leg withdraws in pain...while the otehr leg extends to retain balance)
Most proteins made in the neuron are translated in the _________
soma
2 types of motor (efferent) neurons
somatic and autonomic motor neurons
Advantage of electrical synapase is _________---
they are fast, but lose amplitude from one cell to the next
What does it mean if an action potential is all or none ?
unless the membrane completely depolarizes, no action potential is generated
The luteal surge is largely due to a positive feedback loop between which of the following hormones? A Estrogen and LH B Estrogen and FSH C FSH and LH D LH and prolactin
As LH levels rise in the follicular phase of the menstrual cycle, estrogen levels are stimulated to increase. Estrogen in turn stimulates the release of LH, which results in a positive feedback loop that causes the luteal surge prior to ovulation.
Which of the following organs, if absent, would prohibit ACTH from appropriately acting? A kidney B gallbladder C small intestine D adrenal gland
ACTH (adrenocorticotropic hormone) is released from the anterior pituitary and acts on the adrenal gland to release cortisol. In the absence of the adrenal gland, ACTH would not be able to function, thus (D) is the correct answer.
An inhibitor of adrenergic neurotransmitters would be expected to act at which of the following areas? A At a sympathetic neuromuscular junction. B At the presynaptic region of a parasympathetic synapse. C At the postsynaptic region of a somatic synapse. D At the preganglionic junction of a sympathetic neuron.
Adrenergic neurotransmitters (notably epinephrine and norepinephrine) are utilized at the postganglionic neurons of the sympathetic nervous system. All of the other synapses listed in the question would use the neurotransmitter acetylcholine. Thus (A) is the correct answer.
Glucocorticoids both block the activity of insulin and stimulate gluconeogenesis. Which of the following would be an expected effect of glucocorticoid use? A elevated blood sugar levels B increased basal metabolic rate C increased sensitivity to immunological challenge D increased bone density
Although knowledge of the relationship between bone density and glucocorticoids is not expected for the MCAT and there is insufficient prompting in the question, glucocorticoids often result in osteoporisis, not increased bone density. Either way, (D) is incorrect. (B) is incorrect because the basal metabolic rate is regulated by thyroid hormones, not directly by glucose. Glucocorticoids are keeping glucose out of cells which suggests an overall lowered glucose availability for metabolism. (C) does not have a direct correlation to the issue of glucose concentrations. The answer is (A) because insulin is responsible for glucose sequestration (blocking it results in higher blood sugar levels) and gluconeogenesis results in more glucose availability in the blood. These would both have the effect of increasing blood glucose levels.
Mnemonic (calcitonin) in the thyroid
C (stands for calcitonin), d (decreases) Calcium
Which of the following is not true about the parasympathetic nervous system? A The parasympathetic system is a branch of the autonomic nervous system. B The postganglionic neurons of the parasympathetic system are located closer to the effector than those in the sympathetic system. C Epinephrine is used as a neurotransmitter. D The parasympathetic system redirects blood toward the digestive system.
C, Choices (A), (B), and (D) are all true statements. The statement in (C) is not true. The primary neurotransmitter in the parasympathetic system is acetylcholine (the receptors are cholinergic). The receptors in the sympathetic system are adrenergic and use epinephrine. Thus, the correct answer is (C).
Which of the following is regulated by the hypothalamus? A heart rate B motor performance C appetite and body temperature D sleep and arousal functions
C, The hypothalamus is largely responsible for homeostasis, which includes appetite and body temperature. The heart rate and other autonomic functions are regulated by the medulla oblongata. Motor performance, perception and balance are regulated by the cerebellum. The midbrain is involved in sleep and arousal functions.
When an action potential reaches the axon knob, _____dependant release of neurotransmitters occurs
Ca 2+
In the peripheral nervous system, which cell myelinates and in turn increases the action potential across a nerve axon? A Microglial cell B Oligodendrocyte C Astrocyte D Schwann cell
D, Oligodendrocytes provide myelination in the central nervous system but not the peripheral nervous system. Astrocytes and microglial cells are support cells that clean debris from tissue surrounding nervous tissue. Schwann cells are the myelination cells of the peripheral nervous system, and thus (d) is the correct answer.
A molecule is discovered which blocks production of TSH from the anterior pituitary. What effect would this have in the body? A Decrease prolactin release B Increase thyroid stimulation C Stop ovulation in women D Decrease metabolism
D, TSH is the hormone which stimulates the thyroid gland to release thyroid hormone. Thyroid hormone is responsible for many different effects in the body, one of which is increasing metabolism. Thus decreasing TSH production would decrease thyroid hormone and thus decrease metabolism.
Which statement correctly characterizes the Nodes of Ranvier? A They are insulated by myelin sheaths. B They are insulated by Schwann cells. C They possess a double membrane used for developing a proton motive force for action potentials D They possess gated Na and K channels involved in action potentials
D, The Nodes of Ranvier are exposed sections of the axon which lie between Schwann cells. The Nodes of Ranvier help propagate action potentials along the axon very quickly by regulating their Na and K channels.
Which of the following correctly displays the flow of ions in a neuron during different phases of an action potential? A Sodium leaves the cell during depolarization B Potassium enters the cell during depolarization C Potassium leaves the cell during repolarization D Sodium leaves the cell during repolarization
During depolarization, sodium channels are open which allows sodium to enter the cell. During repolarization, potassium channels are open and potassium leaves the cell. Thus (C) is the correct answer.
The sympathetic nervous system is associated with the :
Flight or Fight Response (and is primarily activated during periods of prolonged stress)
What are glia ?
Glia are supporting cells in the nervous system. In addition to forming myelin sheaths, they regulate the immune system, clear out neurotransmitter, maintain homeostasis, and other supportive functions.
Monosynaptic reflexes:
Have only one synapse between the sensory neuron and the motor neuron (knee-jerk reflex)
How light/image is processed by eye
Incoming light-->corena (bends and focuses light rays) --->pupil (diametr is controlled by pigmented iris) --> iris responds to intesnity of light in the surroundings (light makes pupil constrict)--->lens (controlled by cillialary muscles) -->focuses light to retina
If the pressure in the brain builds up too rapidly, it has nowhere to go.....therefore which part is affected?
Medula oblongata (which connects to the spinal cord)
Proprioceptors
Position of body in space information
The sympathetic nervous system originates with ____________in the spinal cord :
Preganglionic neurons
Which of the following hormones is NOT released as a stress-response mechanism? A Prolactin B Cortisol C Epinephrine D ACTH
Prolactin is a mammary-stimulating hormone which induces milk production in breast tissue. It is not a stress-response hormone. Cortisol, epinephrine, and ACTH are all involved in stress responses. Thus the correct answer is (A).
Myelin is formed by two type of glia:
Schwann cells and Oligodendrocytes
Regarding neural communication, which statements are TRUE? I. The dendrites of a neuron receive messages from other neurons. II. The action potential starts when potassium ions enter the axon. III. Neural communication involves an electrochemical process. IV. The dendrites of the sending neuron secrete neurotransmitters into the synapse. A I and III only B I, II, and III only C II and IV only D I, II, III, and IV
Statements (I) and (III) are true. It is true that dendrites receive messages from other neurons. It is also true that neural communication is an electrochemical process. Answer (II) is incorrect because the action potential starts when sodium ions enter the axon. Answer (IV) is also incorrect because the synaptic vesicles, not the dendrites, of the sending neuron secrete neurotransmitters into the synapse. Thus, the correct answer is (A).
An elderly gentleman has a stroke which damages a large part of his brainstem. Which of the following would not be an expected symptom for this individual? A Weakness of the left arm B Absence of the knee-jerk reflex C Tingling of the right leg D Drastic loss of vision
The knee-jerk reflex is the only option listed which does not require the brainstem. The knee-jerk reflex starts with the nerve in the knee tendon, goes to the spinal cord, and then directly back out to the muscle to cause the knee to extend. Reflexes such as these do not travel up to the spinal cord to the brain, thus they would be unaffected in a stroke, such as what occurred with this individual.
The middle ear involves: A movement of hair cells. B amplifying and modulating sounds as they enter the oval window. C carrying waves to the tympanic membrane. D vibrations through semicircular canals.
The middle ear involves three small bones which serve to modify the air vibratory signals to fluid vibratory signals which then enter the oval window. Thus (B) is the correct answer.
Axon
The nerve fiber that is connected to the soma (cell body) via axon hillock...transmits impulses away from the cell body
The nodes of ranvier are responsible for: A increasing the number of sodium channels in an axon. B increasing the speed of electric conduction down an axon. C regenerating an action potential as it travels down the axon. D stabilizing electric impulses within an axon.
The nodes of ranvier are open to the extracellular space (unlike the myelinated areas of the axon), thus ion exchange happens here and allows for regeneration of the action potential as it moves down the axon. Nodes of ranvier are NOT responsible for increased speed down the axon, however; it is the myelin sheath which allows for quick transmission of signal without significant loss of the action potential signal. Thus (C) is the correct answer.
Firing frequency
The number of action potentials in a given time
Which of the following is true as the membrane potential of a neuron crosses from negative to positive during depolarization in action potential? A Sodium reverses its direction and begins to flow out of the cell. B Sodium continues to flow into the cell until the voltage has reached a certain positive threshold. C Potassium begins to flow out of the cell. D The sodium-potassium pump ceases to function until the neuron has repolarized.
There is nothing particular special about the threshold of 0 mV during the action potential. The resting potential is approximately -70 mV and the action potential peaks at approximately +40 mV when the sodium channels begin to close and the potassium channels open. Thus, as the 0 mV barrier is crossed, sodium continues to flow into the cell making (B) the correct answer. (C) does not occur until the peak of the action potential has been reached; (D) does not occur as the pump operates independently of action potentials.
All of the following act as tropic hormones EXCEPT: A TSH B PTH C ACTH D LH
Tropic hormones are specific types of hormones which act on other endocrine glands, rather than acting directly on their target cells. For instance, TSH is released from the anterior pituitary and then acts on the thyroid (an endocrine organ) which in turn T3 and T4 which have effects on target cells throughout the body. The only hormone which is not a tropic hormone, among those listed, is PTH which acts directly on bones, the GI tract, and the kidneys. Thus (B) is the correct answer.
How does an action potential work ?
Voltage-dependant Na+ channels in the membrane are closed when the cell is at resting potential. When the membrane potential rises to a certain threshold, the Na+ channels open and brief depolarization (more +/less negative) occurs. This also causes K+ channels to open (but in a time delayed manner) and then the K+ that was originally in the cell rushes out in the extracellular enviornment, causing hyperpolarization (that is, the cell becomes more negative than resting potential)
Myelin sheath
What mammalian axons are enshathed by (insulated by) which allows axons to conduct impulses faster
An action potential starts locally and then spreads in either direction...what happens when it reaches axon terminal ?
Will cause a chemical rxn and release neurotransmitter into next cell which causes ACTION POTENTIAL of next cell.
Nuclei
a cluster containing a number of nerve cell bodies, typically linked by synapses, and often forming a swelling on a nerve fiber found in the central nervous system (CNS)
Efferent neurons (peripheral nervous system )
a neuron whose cell body is located in the spinal cord and whose axon projects outside the spinal cord to directly or indirectly control effector organs
If the cell becomes sufficiently excited or depolarized, an __________is generated
action potential
The ___________is a brief local change in the charge of a cell due to an electrical impulse
action potential
At the nodes of ranvier, the electrical impulse or ___________is :
action potential is attentuated and then sent to next schwann cell (with little attenuation)
The outer ear consists of :
auricle (pinna) and auditory canal
A synapse (electrochemical impulse) can occur between Axon and dendrite, known as _______
axodendritic
Think of neurons as
bannanas of the sea....they have high potassium inside, but extracellular levels of Na and Cl are higher
The neuron is the :
basic structural unit of the nervous system
interoceptrors
blood pressure, blood, blood pH
Soma
carries out most of the cells biological processes, home of the nucleus and most of the cells organelles including : ER, Golgi, and Ribosomes
Brain gray matter
cell bodies
What are the 3 parts of a neuron ?
cell body (soma), axon (sends info), dendrites (receive info)
Hyperpolarization occurs when:
cell has an even lower membrane potential than that at resting
Depolarization occurs when
cell has higher membrane potential than at rest
Ganglia
cluster containing a number of nerve cell bodies, typically linked by synapses, and often forming a swelling on a nerve fiber found in the peripheral nervous system (PNS)
Inhibitory inputs can cancel out _______inputs
excitatory
PTH (parathyroid hormone)
increases calcium
CNS microglia
ingest and breakdown pathogens (macrophages of the CNS )
In the brain, GABA is generally a __________neurotransmitter
inhibitory
Brain white matter
myelinated axons
Interneurons
neurons that create neural circuits, enabling communication between sensory or motor neurons and the central nervous system
afferent neurons
neurons that transmit sensory information
Gaps between segments of myelin are called :
nodes of ranveier
Glial cells
non-neuronal support cells in the nervous system
A neuron can have ______,________,________dendrites
one, none, some
The middle ear consists of :
ossicles (bones) = malleus, incus, and stapes
What causes polarization of neuron at rest ?
potential differnce is the result of an unequal distribution of ions between extracellular and intercellular evironment
The electrochemical gradient is a form of _________________that is utilized in the cell during an action potential
potential energy
Astrocyte function ?
supply nutrients and form blood brain barrier (BBB)
