Ch 4- Nervous System Flashcards
“specialized cells capable of transmitting electrical impulses and then translating those electrical impulses to chemical signals”
Neurons
“Myelin is produced by_________ in the central nervous system and ___________ in the peripheral nervous system”
oligodendrocytes
Schwann cells
“Between the neurons, there is a small space into which the terminal portion of the axon releases neurotransmitters, which bind to the dendrites of the postsynaptic neuron. This space is known as the ”
Synaptic cleft
“In the central nervous system, axons may be bundled together to form
tracts
“The cell bodies of neurons in the same tract are grouped into ”
Nuclei
“nourish neurons and form the blood–brain barrier, which controls the transmission of solutes from the bloodstream into nervous tissue.”
Astrocytes
“line the ventricles of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as a shock absorber.”
Ependymal Cells
“are phagocytic cells that ingest and break down waste products and pathogens in the central nervous system.”
Microglia
“Neurons use all-or-nothing messages called _______ to relay electrical impulses down the axon to the synaptic bouton.”
action potentials
“The Na+/K+ ATPase maintains a resting membrane potential of ______ by moving ______ Na+ ions out of the cell for every _______ K+ ions moved into the cell at the expense of ____ATP
-70 mV, 3, 2, 1
“If the axon hillock receives enough excitatory input to be depolarized to the threshold value (usually in the range of –55 to –40 mV), an _________ will be triggered.”
Action potential
“ In __________ multiple signals are integrated during a relatively short period of time. A number of small excitatory signals firing at nearly the same moment could bring a postsynaptic cell to threshold, enabling an action potential.”
temporal summation
“In _________ the additive effects are based on the number and location of the incoming signals”
spatial summation
“If the cell is brought to threshold, ___________ open in the membrane”
Voltage gated sodium channells
“There is a strong __________ that promotes the migration of sodium into the cell. From an electric standpoint, the interior of the cell is more negative. Sodium is positive. From chemical standpoint, higher concentration of sodium out than in
Electrochemical Gradient
“When Vm approaches +35 mV, the sodium channels are _________ and will have to be brought back near the resting potential to be ________”
inactivated, activated
“Thus, these sodium channels can exist in three states: CLOSED (before the cell reaches threshold, and after inactivation has been reversed), OPEN (from threshold to approximately +35 mV), and INACTIVE (from approximately +35 mV to the resting potential).”
“The positive potential inside the cell not only triggers the voltage-gated sodium channels to inactivate, but also triggers the voltage-gated potassium channels to”
Open
“As positively charged potassium cations are driven out of the cell, there will be a restoration of the negative membrane potential called”
repolarization
“The speed at which action potentials move depends on
the length and cross-sectional area of the axon”
The effect of cross section is more significant than the effect of length
Myelin is so effective that the membrane is only permeable to ion movement at
The nodes of Ranvier
“It is important to note that all action potentials within the same type of neuron have the same”
Potential difference during depolarization
“Increased intensity of a stimulus does not result in an increased potential difference of the action potential, but rather
an increased frequency of firing.”
“the neuron preceding the synaptic cleft is called the”
presynaptic neuron
“the neuron after the synaptic cleft is called the”
Postsynaptic neuron
“If a neuron signals to a gland or muscle, rather than another neuron, the postsynaptic cell is termed an”
effector
“Prior to release, neurotransmitter molecules are stored in
membrane-bound vesicles in the nerve terminal.”
“When the action potential reaches the nerve terminal, ___________ open, allowing calcium to flow into the cell.
voltage-gated calcium channels
-This sudden increase in intracellular calcium triggers fusion of the membrane-bound vesicles with the cell membrane at the synapse, causing exocytosis of the neurotransmitter.”
“It is critical to understand the difference between______ and _______ transmission. Within a neuron, electricity is used to pass signals down the length of the axon. Between neurons, chemicals (neurotransmitters) are used to pass signals to the subsequent neuron (or gland or muscle).”
Chemical, Electrical
“Once released into the synapse, the neurotransmitter molecules diffuse across the cleft and bind to ________ on the postsynaptic membrane”
Receptors
“neurotransmitter receptors, which tend to be either________ or ________
ligand-gated ion channels or G protein-coupled receptors.”
“If the receptor is a ligand-gated ion channel, the postsynaptic cell will either be ____________. If it is a G protein-coupled receptor, it will cause either _______or ________
Excerpt From: Kaplan. “Kaplan MCAT Biology Review: Created for MCAT 2015 (Kaplan Test Prep).” iBooks.
- Depolarized or hyper polarized
- changes in the levels of cyclic AMP (cAMP) or an influx of calcium”
3 main mechanisms to remove neurotransmitters from synaptic cleft
- Break it down with enzymes (Acetylchinesterase)
- Bring it back into presynaptic neuron using REUPTAKE CARRIERS
(Serotonin, Dopamin, Norepi)
3.Neurotransmitters my diffuse out of synaptic cleft
“Generally speaking, there are three kinds of nerve cells in the nervous system: ”
“sensory neurons, motor neurons, and interneurons”
When an action requires brain or brainstem input
Supra spinal Circuits are used
“The spinal cord extends downward from the brainstem and can be divided into four divisions:”
“cervical, thoracic, lumbar, and sacral. ”
“Like the brain, the spinal cord also consists of white and grey matter. The ______ matter lies on the outside of the cord, and the ______ matter is deep within it”
White, Grey
“The axons of motor and sensory neurons”
Are IN the spinal chord
“The sensory neurons bring information in from the periphery and enter on the dorsal (back) side of the spinal cord. The cell bodies of these sensory neurons are found in the”
Dorsal Root ganglia
“Motor neurons exit the spinal cord
Ventrally
“consists of sensory and motor neurons distributed throughout the skin, joints, and muscles.”
Somatic Nervous System
“One primary difference between the somatic and autonomic nervous systems is that the peripheral component of the autonomic nervous system contains
2 Neurons (preganglionic Neuron and Post-Ganglionic Neuron)
“The soma of the preganglionic neuron is in the CNS, and its axon travels to a ganglion in the PNS. Here it synapses on the cell body of the postganglionic neuron, which then affects the target tissue.”
“A motor neuron in the somatic nervous system goes directly from the spinal cord to the muscle without synapsing. ”
____________ is the neurotransmitter responsible for parasympathetic responses in the body and is released by both preganglionic and postganglionic neurons.”
Acetylcholine
“In the sympathetic nervous system, preganglionic neurons release acetylcholine, while most postganglionic neurons release norepinephrine.”
“There are two types of reflex arcs:
monosynaptic and polysynaptic.”
“In a ___________, there is a single synapse between the sensory neuron that receives the stimulus and the motor neuron that responds to it”
monosynaptic reflex arc,
(no interneuron)
Classic Example is the knee-jerk reflex
“In a __________ there is at least one interneuron between the sensory and motor neurons. ”
polysynaptic reflex arc
Stepping on a nail and involving the withdrawal reflex
