Term
| The Role Of the Nervous System |
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Definition
| The NS detects environmental changes that impact the body, then responds to those changes. It is responsible for all our behaviors, memories, and movements. |
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Term
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Definition
| The Central Nervous System (CNS), which is the brain and spinal cord (it processes environment) and the Peripheral Nervous System, which is everything else, including the spinal nerves, ganglia,enteric plexus, and sensory receptors. The PNS breaks down even more into the somatic NS, the Autonomic NS, and the Enteric NS (it senses environment) |
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Term
| 3 fundamental steps of NS |
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Definition
1. A sensory function detect internal and external stimuli (PNS)
2. An interpretation is made (cns)
3. A motor response occurs (PNS) |
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Term
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Definition
Nerve Cell-- receives, processes, and transmits info by manipulating the flow of charge across their membranes (they cant regenerate, once a neuron is lost, it will not reproduce)
They are the real functional unit of the NS, forming complex processing networks within the brain and spinal cord that bring all regions of the body under CNS |
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Term
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Definition
| Support and provide nutrition to the brain but do not manipulate info. They maintain the internal environment so that neurons can do their job. Neuroglia can regenerate if loss. They are the glue that supports and maintains the neuronal network. They are smaller than neurons, but greatly outnumber them |
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Term
| The peripheral NS breaks down into? |
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Definition
Somatic NS
Autonomic NS
Enteric NS |
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Term
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Definition
The SNS consists of:
1. somatic sensory (afferent-towards) neurons that convey info from sensory receptors in the head, body wall, and limbs towards the CNS
2. Somatic motor (efferent-away) neurons that conduct impulses away from the CNS towards skeletal muscles under voluntary control in the periphery
3. Interneurons that conduct impulses between afferent and efferent neurons within the CNS |
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Term
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Definition
| Interneurons are any neurons that conduct impulses between afferent and efferent neurons within the CNS |
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Term
| The Autonomic NS (involuntary) |
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Definition
The ANS consists of:
1. Sensory neurons that convey information from autonomic sensory receptors located primarily in visceral organs like the stomach or lungs to the CNS
2. Motor Neurons under involuntary control conduct nerve impulses from the CNS to smooth muscle, cardiac muscle, and glands. The motor part of the ANS consists of two branches; the sympathetic and parasympathetic divisions |
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Term
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Definition
| small masses of neuronal cell bodies located outside the brain and spinal cord, usually closely associated with cranial and spinal nerves. |
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Term
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Definition
| "the brain of the gut"; involuntary controls GI propulsion, and acid and hormonal secretions, it was once considered part of the ANS. There are over 100 million neurons in enteric plexuses |
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Term
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Definition
| A cell body, dentrites, axon, axon terminals, myelin sheath (some) |
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Term
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Definition
| has a nucelus surrounded by cytoplasm, contains orgallelles (in neurons the rough ER is called Nissl bodies) it has a striped tiger appearance, but no miotic apparatus is present, since neurons dont undergo miosis |
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Term
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Definition
| Neurons gather info at dentrites and process it in the dendritic tree and cell body. Dentrites are the recieving end of the neuron. They are short, highly branched structures that conduct impulses toward the cell body. They also contain organelles |
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Term
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Definition
| Axons conduct impulses away from the body towards another neuron or effector cell. The Axon hillock is where the axon joins the cell body. The initial segemnt is the beginning of the axon. The trigger zone is the junction between the axon hillack and the initial segment |
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Term
| Axon Terminals and Synaptic End Bulbs |
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Definition
| The axon and its collaterals end by dividing into many fine processes called axon terminals. The tips of some azon terminals swell into the bulb-shaped structures called synaptic end bulbs |
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Term
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Definition
| The site of communications between 2 neurons or btwn a neuron and another effector cell |
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Term
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Definition
| the gap between the pre and post synaptic cells |
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Term
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Definition
| synaptic end bulbs and other varicosites on the axon terminals of presynaptic neurons contain many tiny membrane-enclosed sacs called synaptic vesicles that store packets of NTs |
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Term
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Definition
1. Conveys axoplasm in one direction only-- from the cell body toward to axon terminals
2. It supplies new axoplasm (the cytoplasm in axons) to developing or regenerating axons, and replenishes axoplasm in growing and mature axons |
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Term
| Fast Axonal Transport (FAT) |
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Definition
1. moves materials in both directions
2. Fast axonal transport that occurs in an anterograde (forward) direction moves organelles and synaptic vesicles from the cell body to the axon terminals. FAT that moves backwards moves membrane vesicles and other cellular materials from the axon terminals to the cell body to be degraded or recycled (tropic chemcials) |
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Term
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Definition
| have several dendrites and only one axon and are located throughout the brain and spinal cord. Most of the neurons in the human body are mulitpolar |
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Term
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Definition
| have one main dentrite and one axon. they are used to convey special senses of sight, smell, hearing, and balance. As such, they are found in the retina of the eye, and the olfactory area of the brain |
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Term
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Definition
| contain one process which extends from the body and divides into a central branch that functions as an axon and dentritic root. Unipolar structure is often employed for sensory neurons that convey touch and streching info from the extremeties. |
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Term
| Sensory or Afferent Neurons |
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Definition
| Convey action potentials into the CNs via cranial and spinal nerves. Most are unipolar |
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Term
| Motor or Efferent Neurons |
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Definition
| Convey action potentials away from the CNS to effectors (muscle and glands) in the periphery through cranial and spinal nerves. Most are multipolar. |
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Term
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Definition
| they do not generate or conduct nerve impulses. they support neutrons by forming the blood brain barrier, forming the mylein sheath, making the CSF, and participating in phagocytosis |
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Term
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Definition
| Astrocytes, oligodendrocytes,microglia, and ependymal cells |
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Term
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Definition
| support neurons in the CNS and maintain the chemical environment (sodium and potassium) They are the most common |
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Term
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Definition
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Term
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Definition
| participate in phagocytosis, and protect brain cells from toxins |
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Definition
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Term
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Definition
| Satellite Cells and Schwann Cells |
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Term
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Definition
| Support neurons in the PNS |
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Term
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Definition
| Produce myelin in PNS, the outer nucleated cytoplasmic later of the schwann cell, which encloses the myelin sheath is the neurolemma. When an axon is injured, the neurolemma aids regeneration by forming a regeneration tube that guides and stimulates regrowth of the axon |
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Term
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Definition
| process of forming a myelin sheath, which insulates and increases nerve impulse speed. Oligodendrocytes in CNS form it, Schwann cells in PNS form it. MS is a disease where the body attacks myelin sheath |
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Term
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Definition
| the gaps in the myselin sheath |
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Term
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Definition
| White matter of the brain and spinal cord is formed from aggregations of myelinated axons from many neurons |
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Term
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Definition
| (gray because it lacks myelin) of the brain and spinal cord is formed from neuronal cell bodies and dentrites. |
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Term
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Definition
| are used for short distance communication only. Graded potentials have different names depending on the type of stimulus and where they occur. They are voltage variable aptitudes that can be added together (summate) or cancel each other out-- the net result is a larger or smaller graded potential. Graded Potentials occur mainly on dendrites and cell body of a neuron--they do not travel down the axon |
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Term
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Definition
| allow communcations over long distances within the body. It is a signal which travels the length of the neuron. During an AP, the membrane potential reverses and then eventually is restored to its resting state. If a neuron receives a threshold stimulus, a full strength nerve impulse is produced and spreads down the axon of the neuron to the axon terminals. If a stimulus is not strong enough, no nerve impulse will result |
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Term
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Definition
| respond to a NT and are mainly concentrated at the synapse (produce graded potentials) |
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Term
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Definition
| respond to changes in the transmembrane electrical potential and are mainly located along the neuronal axon. (Produce APS) |
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Term
| Mechanically Gated Channels |
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Definition
| respond to mechanical deformation (applying pressure to a receptor)(produce graded potentials) |
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Term
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Definition
| They are also gated, but they are not active, and they open and close randomly |
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Term
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Definition
| -70 mv.A cell that exhibits RMP is said to be polarized. in this state the cell is primed, and is ready to produce an action potential, but it must first produce graded potentials to depolarize the cell to threshold. |
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Term
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Definition
| Increase in mv, sodium rushes into the cell |
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Term
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Definition
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Term
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Definition
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Term
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Definition
1. Depolarizing Phase
2. Repolarizing Phase
(-70 is RMP, -55 is threshold. =30 is peak of AP |
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Term
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Definition
| Graded potentials that result in depolarization of the neuron from -70 mV to threshold (about -55mv) will cause a sequence of events to rapidly unfold. Voltage gated NA+ channels open during the steep depolarization phase allowing sodium to rush into the cell making it more positive. |
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Term
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Definition
| Potassium channels open and potassium rushes out of the cell, the process of k leaving overshoots the RMP but eventually the RMP of -70 is restored. If the K+ channels remain open, hyperpolarization can occur, (-90mv) |
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Term
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Definition
| If a stimulus reaches threshold, the action potential will always be the same.A stronger stimulus will not cause a larger impulse |
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Term
| Absolute Refractory Period |
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Definition
| A time which a cell cannot generate another AP, no matter how strong the stimulus is. This period coincides with the period of sodium channel activation and inactivation.(depolarization and repolarization) |
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Term
| Relative Refractory Period |
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Definition
| a period in time during which a second action potential can be generated, but only by a larger-than-normal stimulus. It coincides with the period when the voltage gated potassium channels are open after inactivated sodium channels have returned to their resting state. (hyperpolarization)Graded potentials do not exhibit a refractory period. |
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Term
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Definition
| propagation of An AP down an unmyelinated axon (slow) |
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Term
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Definition
| propagation of an AP down a myelinated axon (fast) |
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Term
| Speed of an Action potential is affected by? |
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Definition
1. Myelination
2. Axon diameter
3. Temperature
4. Frequency of AP
5. # of neurons recruited |
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Term
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Definition
| large, fast, myelinated neurons that carry touch and pressure sensations, many motor neurons are also this type |
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Term
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Definition
| are of medium sized and speed (15m/sec) and comprise myelinated visceral sensory and autonomic preganglionic neurons |
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Term
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Definition
| are the smallest and slowest and comprise unmyelinated sensory and autonomic motor neurons (pain) |
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Term
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Definition
Both excitatory and inhibitory neurotransmitters are present in the CNS and PNS.
The same neurotransmitter may be excitatory in some locations and inhibitory in others.
For example, acetylcholine (ACh) is a common neurotransmitter released by many PNS neurons (and some in the CNS). Ach is excitatory at the NMJ but inhibitory at other synapses.
Many amino acids act as neurotransmitters:
Glutamate is released by nearly all excitatory neurons in the brain.
GABA is an inhibitory neuro-
transmitter for 1/3 of all brain synapses.
Valium is a GABA agonist that enhances GABA’s depressive effects (causes sedation).
Other important small-molecule neurotransmitters are listed |
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Term
| Signal transmission at the synapse |
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Definition
a one-way transfer from a presynaptic neuron to a postsynaptic neuron.
When an AP reaches the end bulb of axon terminals, voltage-gated Ca2+ channels open and Ca2+ flows inward, triggering release of the neurotransmitter.
The neurotransmitter crosses the synaptic cleft and binds to ligand-gated receptors on the postsynaptic membrane.
The more neurotransmitter released, the greater the number and intensity of graded potentials in the postsynaptic cell.
In this way, the presynaptic neuron converts an electrical signal (nerve impulse) into a chemical signal (released neurotransmitter). The postsynaptic neuron receives the chemical signal and in turn generates an
electrical signal (postsynaptic
potential).
The time required for these
processes at a chemical synapse
produces a synaptic delay of
about 0.5 msec. |
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Term
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Definition
Synthesis can be stimulated or inhibited.
Release can be blocked or enhanced.
Removal can be stimulated or blocked.
The receptor site can be blocked or activated.
An agonist is any chemical that enhances or stimulates the effects at a given receptor.
An antagonist is a chemical that blocks or diminishes the effects at a given receptor. |
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Term
| Excitatory postsynaptic potential (EPSP) |
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Definition
| causes a depolarization of the postsynaptic cell, bringing it closer to threshold. Although a single EPSP normally does not initiate a nerve impulse, the postsynaptic cell does become more excitable. |
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Term
| Inhibitory postsynaptic potential (IPSP) |
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Definition
| ) hyperpolarizes the postsynaptic cell taking it farther from threshold |
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Term
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Definition
| occurs when postsynaptic potentials arrive near the same location |
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Term
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Definition
occurs when postsynaptic potentials arrive close to the same time
Whether or not the
postsynaptic cell
reaches threshold
depends on the
net effect after
Summation of all
the postsynaptic
potentials. |
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Term
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Definition
If a neurotransmitter could linger in the synaptic cleft, it would influence the postsynaptic neuron, muscle fiber, or gland cell indefinitely – removal of the neurotransmitter is essential for normal function.
Removal is accomplished by diffusion out of the synaptic cleft, enzymatic degradation, and re-uptake by cells.
An example of a common neurotransmitter inactivated through enzymatic degradation is acetylcholine. The enzyme acetylcholinesterase breaks down acetylcholine in the synaptic cleft. |
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Term
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Definition
| Neurons process info when changes occur at the trigger zone through spatial and temporal summations of IPSPs and EPSPs. An average neuron receives 10,000 synaptic inputs |
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Term
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Definition
| is the process accomplished by the postsynaptic neuron when it combines all excitatory and inhibitory inputs and responds accordingly. This process occurs over and over again as interneurons are activated in higher parts of the brain |
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Term
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Definition
| A neuronal network may contain thousands or even millions of neurons. Types of circuits include diverging, converging, reverberating, and parallel after discharge |
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Term
| Diverging Circuit and Converging circuit |
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Definition
| a small # of neurons in the brain stimulate a much larger number of neurons in the spinal cord A converging circuit is the opposite. |
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Term
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Definition
| impulses are sent back through the circuit time and time again--used in breathing, coordinated muscular activites, waking up, and short-term memory |
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Term
| Parallel after--discharge circuits |
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Definition
| involve a single presynaptic cell that stimulates a group of neurons, which then synapse with a common postsynaptic cell--used in precise activites such as mathematical calculations |
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Term
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Definition
| A large # of neurons in the brain stimulate a much smaller # of neurons in the spinal cord |
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