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64 Cards in this Set
- Front
- Back
neuromuscular junction
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a functional connection bewteen the distal end of a nerve fiber and the middle of a muscle fiber; consists of a synaptic knob and motor end plate
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synaptic knob
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the dilated tip of a nerve fiber that contains synaptic vesicles
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motor end plate
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a depression in the sarcolemma, near the middle of the muscle fiber, that receives the synaptic knob; contains acetylcholine receptors
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synaptic cleft
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a gap of about 60 to 100 nm between the synaptic knob and the motor end plate
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synaptic vesicle
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a secretory vesicle in the synaptic knob that contains acetylcholine
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junctional folds
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invaginations of the membrane of the motor end plate where ACh receptors are especially concentrated; locatedd across the active zones
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acetylcholine (ACh)
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the neurotransmitter released by a somatic motor fiber that stimulates a skeletal muscle fiber (also used elesewhere in the nervous system)
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ACh receptor
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an integral protein in the sarcolemma of the motor end plate that binds to ACh
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acetylcholinesterase (AChE)
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an enzyme in the sarcolemma and basil lamina of the muscle fiber in the synaptic region; responsible for degrading ACh and stopping the stimulation of the muscle fiber
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receptors
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cells and organs specialized to detect changes in the body and its external environment
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effectors
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cells and organs (mainly muscle and gland cells) that carry out the body's responses
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central nervous system (CNS)
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consists of the brain and spinal cord, which are enclosed and protected by the cranium and vertebral column
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peripheral nervous system (PNS)
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onsists of all the nervous syste except the brain and spinal cord. it is composed of nerves and ganglia
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nerve
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a bundle of nerve fibers wrapped in fibrous connective tissue. nerves emerge from the CNS through foramina of the skull and vertebral column and carry signals to and from other organs of the body
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ganglion
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a knotlike swelling in a nerve where the cell bodies of neurons are concentrated
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sensory (afferent) division
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carries sensory signals by way of afferent nerve fibers from sensory receptors (cells and organs that detect stimuli) to the CNS
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visceral sensory division
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carries signals mainly from the viscera of the thoracic and abdominal cavites, such as the heart, lungs, stomach and urinary bladder
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somatic sensory division
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carries signals from receptors in the skin, muscles, bones and joints
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motor (efferent) division
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carries motor signals by way of efferent nerve fibers from the CNS to effectors (cells and organs that carry out the body's responses, mainly gland and muscle cells)
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visceral motor division (autonomic nervous system)
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carries signals to glands, cardiac muscle and smooth muscle. we usually have no voluntary control over these effectors, and this system operates at an unconscious level. the responses of this system and its effectors are visceral reflexes
the autonomic nervous system has two further divisions: sympathetic and parasympathetic |
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sympathetic division
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tends to arouse the body for action, for example by accelerating the heartbeat and increasing respiratory airflow, but it inhibits digestion
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parasympathetic division
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tends to have a calming effect, slowing down the heartbeat, for example, but stimulating digestion
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somatic motor division
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carries signals to the skeletal muscles. this output produces muscular contractions that are under involuntary control as well as involuntary contractions called somatic reflexes
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sensory (afferent) neurons
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specialized to detect stimuli such as light, heat, pressure and chemicals, and transmit information about them to the CNS. these can begin in almost any organ of the body and end in the CNS
afferent refers to signal conduction towards the CNS |
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GTP
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a
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adenelyl cyclase
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an enzyme of the plasma membrane that removes two phosphate molecules from ATP and makes cyclic adenosine monophosphate (cAMP); important in the activation of the cAMP second-messenger system
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cyclic AMP (cAMP)
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cyclic adenosine monophosphate - a cyclic molecule produced from ATP by the actio of adenyl cyclase; serves as a second messenger in many hormone and neurotransmitter actions
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protein kinase A
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a
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protein phosphorylation
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addition of an inorganic phosphate group in an organic molecule
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phosphatase
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a
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protein dephosphorylation
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a
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excitability (irritability)
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the ability to respond to environmental changes called stimuli
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conductivity
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responding to stimuli by producing traveling electrical signals that quickly reach other cells at distant locations
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secretion
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when the electrical signal reaches the end of a nerve fiber, the neuron secretes a chemical neurotransmitter that "jumps the gap" and stimulates the next cell
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dendrite
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primary site for receiving signals from other neurons
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Nissl bodies
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unique to neurons; the cytoskeleton consists of a dense mesh of microtubles and neurofibrils (bundles of acin filaments) that compartmentalize the rough ER into dark-staking regions
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axon hillock
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one side of the soma that is a mount from which the axon (nerve fiber) originates
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neuroglia (glial cells)
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protect the neurons and aid their function by binding them together and provide a supportive framework for the nervous tissue
The four kinds of glial cells in the CNS are: 1. oligodendrocytes 2. astrocytes 3. ependymal 4. microglial The two kinds of glial cells in the PNS are: 1. Schwann 2. satellite |
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oligodendrocytes
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have a bulbous body with as manay as 15 armlike processes each of which reaches out to a nerve fiber and spirals around it like electrical tape wrapped repeatedly around a wire called the myelin sheath
the myelin sheath insulates the nerve fiber from the surrounding extracellular fluid and speeds up signal conduction in the nerve fiber |
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astrocytes
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most abundent in CNS at over 90%
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ependymal cells
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resembled cuboidal epithelium lining the internal cavities of the brain and spinal cord; however, they have no basement membrane and exhibit rootlike processes that penetrate into the underlying nervous tissue
produce cerebrospinal fluid (CFS) and fill |
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myelin sheath
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an insulating layer around a nerve fiber, somewhat like the rubber insulation on a wire formed by oligodendrocytes in the CNS and Schwann cels in the PNS
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neurilemma
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external to the myelin sheath; the outermost coil of the Schwann cell
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nodes of Ranvier
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since each glial cell myelinates only part of an axon the myelin sheath is segmented. these are the gaps between the segments of myelin
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internodes
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the myelin-covered segments from one gap to the next
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initial segment
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the short section of nerve fiber between the axon hillock and the first glial cell
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trigger zone
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collectively, the axon hillock and initial segment; plays an important role in initiating a nerve signal
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neuron doctrine
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the theory that the nervous system is not a continuous "wire" or tube, but a series of separate cells separated by synapses
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electrical potential
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the difference in the concentration of charged particles between one point and another
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autonomic nervous system (ANS)
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defined as a motor nervous system that controls glands, cardiac muscle and smooth muscle; also called the visceral motor system to distinguish it from the somatic motor system that controls the skeletal muscles
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visceral reflexes
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unconscious, automatic, stereotyped responses to stimulation
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sympathetic division
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prepares the body in many ways for physical activity - it increases alertness, heart rate, blood pressure, pulmonary airflow, blood glucose concentration and blood flow to cardiac and skeletal muscle, but at the same time it reduces blood flow to the skin and digestive tract
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parasympathetic division
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has a calming effect on many body functions; it is associated with reduced energy expenditure and normal bodily maintenance, including such functions as digestion and waste elimination; this can be thought of as the "resting and digestion" state
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preganglionic neuron
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has a soma in the brainstem or spinal cord whose axon terminates in the ganglion; it synapses there with a postganglionic neuron
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postganglionic neuron
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ganlion whose axon extends the rest of the way to the target cells (some call this the ganglion neuron since its soma is in the ganglion and only its axon is truly postganglionic
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sympathetic chain
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ganglia (paravertebral ganglia) along each side of the vertebral column
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spinal nerve route
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some postganglionic fibers exit by way of the gray ramus, return to te spinal nerve or its subdivisions and travel the rest of the way to the target organ; this is the route to most sweat glands, piloerector muscles and blood vessels of the skin and skeletal muscles
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sympathetic nerve route
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these nerves form a plexus around each carotid artery and issue fibers from there to effectors in the head - including sweat, salivary and nasal glands; piroerector muscles; blood vessels; and dilators of the iris
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adrenal cortex
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the outer rind of the adrenal glands that secretes steroid hormones; the inner core, the adrenal medulla, is a modified sympathetic ganglion. it consists of modified postganglionic neurons without dendrites or axons
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vagus nerve
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carries about 90% of all parasympathetic preganglionic fibers
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nicotinic receptors
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occur on the postsynaptic cells in all ganglio of the ANS, in the adrenal medulla, and in neuromuscular junctions; all cells with nicotinic receptors are excited by ACh
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muscurinic receptors
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occur on all gland, smooth muscle and cardiac muscle cells that receive cholinergic innveration; some cells with muscarinic receptors are excited while others are inhibited by it
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cerebral cortex
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is involved in many emotional responses and has extensive connections with the hypothalamus, a site of several nuclei of autonomic control
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hypothalamus
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the major control center of the visceral for primitive functions including hunger, thirst, thermoregulation, emotions and sexuality; fight or flight; output from this region travels largely to nuclei in more caudal regions of the brainstema nd from there to the cranial nerves and the sympathetic preganglionic neurons in the spinal cord
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