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82 Cards in this Set
- Front
- Back
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What is the main function of the nervous system?
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Enables organisms to receive and respond to stimuli.
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Neurons
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are the functional units of the nervous system, they convert stimuli into electrochemical signals that are conducted throughout the nervous system
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What are the three main parts of a neuron?
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dendrites
cell body axon |
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Dendrites
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receive information and transmit it toward the cell body
(they are cytoplasmic extensions) |
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Soma
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cell body, contains the nucleus and controls the metabolic activity of the neuron
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Axon
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nerve fiber
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Axon hillock
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connects the cell body to the axon
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Myelin
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insulating substance
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Glial cells
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produce myelin
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Where do oligodendrocytes produce myelin?
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central nervous system
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Where do Schwann cells produce myelin?
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peripheral nervous system
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What are the gaps called between segments of myelin?
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nodes of Ranvier
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What are the ends of axons called?
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synaptic terminals
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What do synaptic terminals release into the synaptic cleft?
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neurotransmitters
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Where is the synaptic cleft located?
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between the axon terminal of one cell and the dendrites of another
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What is multiple sclerosis (MS)?
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demyelinating disorder, where the myelin of the brain and spinal cord is selectively targeted
-results in weakness, lack of balance, vision problems and incontinence |
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What are action potentials?
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impulses that travel along the axon
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What do action potentials cause?
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release of neurotransmitters into the synapse
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What is the resting potential?
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Potential difference between the extracellular space and the intracellular space when a neuron is at rest.
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What is a typical resting potential?
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-70 mM
(inside of the cell is more negative than the outside) |
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How is the potential difference maintained?
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Sodium-potassium pump
(aka: Na+-K+ ATPase) |
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T/F
During resting potential the concentration of K+ is greater on the inside. |
T
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How does the cell become polarized?
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K+ diffuses down its concentration gradient into the cell, creating a net negative charge on the inside.
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What type of transport does the Na+/K+ pump do?
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3 Na+ out for every 2 K+ in
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T/F
A nerve cell receives both excitatory and inhibitory impulses from other cells. |
T
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What does depolarization cause?
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the inside of the cell becomes less negative
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What is the minimum threshold membrane potential?
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the level at which an action potential is created (-50 mV)
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How does an action potential begin?
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when voltage-gated Na+ open in response to depolarization
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What happens when voltage-gated Na+ channels open in response to depolarization?
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it allows Na+ to rush down its electrochemical gradient into the cell
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What causes repolarization?
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voltage-gated K+ channels open and allow K+ to rush out, down its electrchemical gradient
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Hyperpolarization
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more polar than normal (more negative)
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Refractory period
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immediately after an action potential when it may be impossible to initiate another action potential
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T/F
Neuronal information is coded by the frequency and number of action potentials rather than the size of the action potential. |
T
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Electrical gradient
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Na+ wants to go into the cell because it is more negative inside the cell
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Chemical gradient
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Na+ wants to go into the cell because there is less Na+ inside the cell
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Where is tetrodotoxin found?
(TTX) |
Puffer fish
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What does tetrodotoxin do?
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blocks voltage-gated Na+ channels thereby blocking neuronal transmission
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T/F
The harder you hit your thumb with a hammer the more action potentials will travel up your pain fibers, but the size and duration of each individual action potential will remain the same. |
T
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What is the membrane potential of an action potential?
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+ 35 mV
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How do local anesthetics work?
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blocking of the voltage-gated Na+ channels
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Why do local anesthetics work well on pain neurons?
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pain neurons have small axonal diameters and little or no myelin
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Where does action potential get initiated?
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axon hillock
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What makes the backward travel of action potential impossible?
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refractory periods
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T/F
Different axons can propagate action potentials at different speeds. |
T
the greater the diameter of the axon and the more heavily it is myelinated: the faster the impulse travels |
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How does myelin increase the conduction velocity?
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by insulating segments of the axon so that the membrane is permeable to ions only in the nodes of Ranvier
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Saltatory conduction
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action potential "jumps" from node to node
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Effector cells
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postsynaptic cells found in muscles and glands
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What are the vast majority of synapses in humans?
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chemical synapses
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How does cocaine affect one?
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blocks neuronal uptake carriers
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What does acetylcholinesterase do?
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inactivates the neurotransmitter acetylcholine
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Synapse
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the gap between the axon terminal of one neuron and the dendrites of another
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What are afferent neurons?
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sensory neurons
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What are efferent neurons?
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motor neurons
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What does amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease) affect?
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motor neurons
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Interneurons
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participate only in local circuits
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Nerves
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bundles of axons covered with connective tissue
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What makes up the central nervous system?
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brain and spinal chord
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What makes up the peripheral nervous system?
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somatic and autonomic
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What makes up the autonomic
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sympathetic and parasympathetic
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What are the three regions of the brain?
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forebrain, midbrain and hindbrain
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What is gray matter?
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cell bodies
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What is white matter?
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myelinated axone
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What can the forebrain be divided into?
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telencephalon and diencephalon
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What does the corpus callosum allow?
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communication between the right and left cerebral cortices
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What does the diencephalon contain?
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thalamus and hypothalamus
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What does the thalamus do?
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it is a relay and integration center for the spinal cord and cerebral cortex
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What does the hypothalamus control?
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visceral functions like hunger, thirst, sex drive, water balance, blood pressure and temperature regulation
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What does the midbrain do?
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it is a relay center for visual and auditory impulses and plays an important role in motor control
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What is the hindbrain of?
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cerebellum, pons and medulla
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What does the cerebellum do?
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-modulate motor impulses initiated by the motor cortex
-important in maintenance of balance, hand-eye coordination and the timing of rapid movements |
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From what does the pons act as a relay center?
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to allow the cortex to communicate with the cerebellum
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What does the medulla oblongata control?
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breathing, heart rate and gastrointestinal activity
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What makes up the brainstem?
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midbrain, pons and medulla
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Into what regions is the spinal cord divided?
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cervical, thoracic, lumbar and sacral
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What type of reflex is the knee-jerk reflex?
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monosynaptic
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Give an example of the withdrawal reflex (it is polysynaptic)?
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A person steps on a nail
-the injured foot pulls back in pain while the other foot steps forward to maintain balance |
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What does the autononmic nervous sytem control (ANS)?
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Involuntary nervous system-regulates the body's internal environment without the aid of conscious conntrol
-controls cardiac and smooth muscle |
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Where is smooth muscle located?
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blood vessels, digestive tract, bladder and bronchi
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"Fight or flight" is part of which nervous system?
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sympathetic
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"Rest and digest" is part of which nervous system?
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parasympathetic
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"One very important parasympathetic nerve that innervates many of th thoracic and abdominal viscera is called the ..."
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vagus nerve
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What do both the ganglionic and postganglionic neurons release?
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acetycholine
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