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A&P Course Objectives - Exam 2 Terms


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neuromuscular junction
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
synaptic knob
the dilated tip of a nerve fiber that contains synaptic vesicles
motor end plate
a depression in the sarcolemma, near the middle of the muscle fiber, that receives the synaptic knob; contains acetylcholine receptors
synaptic cleft
a gap of about 60 to 100 nm between the synaptic knob and the motor end plate
synaptic vesicle
a secretory vesicle in the synaptic knob that contains acetylcholine
junctional folds
invaginations of the membrane of the motor end plate where ACh receptors are especially concentrated; locatedd across the active zones
acetylcholine (ACh)
the neurotransmitter released by a somatic motor fiber that stimulates a skeletal muscle fiber (also used elesewhere in the nervous system)
ACh receptor
an integral protein in the sarcolemma of the motor end plate that binds to ACh
acetylcholinesterase (AChE)
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
cells and organs specialized to detect changes in the body and its external environment
cells and organs (mainly muscle and gland cells) that carry out the body's responses
central nervous system (CNS)
consists of the brain and spinal cord, which are enclosed and protected by the cranium and vertebral column
peripheral nervous system (PNS)
onsists of all the nervous syste except the brain and spinal cord. it is composed of nerves and ganglia
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
a knotlike swelling in a nerve where the cell bodies of neurons are concentrated
sensory (afferent) division
carries sensory signals by way of afferent nerve fibers from sensory receptors (cells and organs that detect stimuli) to the CNS
visceral sensory division
carries signals mainly from the viscera of the thoracic and abdominal cavites, such as the heart, lungs, stomach and urinary bladder
somatic sensory division
carries signals from receptors in the skin, muscles, bones and joints
motor (efferent) division
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)
visceral motor division (autonomic nervous system)
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
sympathetic division
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
parasympathetic division
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
somatic motor division
carries signals to the skeletal muscles. this output produces muscular contractions that are under involuntary control as well as involuntary contractions called somatic reflexes
sensory (afferent) neurons
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
adenelyl cyclase
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
cyclic AMP (cAMP)
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
protein kinase A
protein phosphorylation
addition of an inorganic phosphate group in an organic molecule
protein dephosphorylation
excitability (irritability)
the ability to respond to environmental changes called stimuli
responding to stimuli by producing traveling electrical signals that quickly reach other cells at distant locations
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
primary site for receiving signals from other neurons
Nissl bodies
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
axon hillock
one side of the soma that is a mount from which the axon (nerve fiber) originates
neuroglia (glial cells)
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
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
most abundent in CNS at over 90%
ependymal cells
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
myelin sheath
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
external to the myelin sheath; the outermost coil of the Schwann cell
nodes of Ranvier
since each glial cell myelinates only part of an axon the myelin sheath is segmented. these are the gaps between the segments of myelin
the myelin-covered segments from one gap to the next
initial segment
the short section of nerve fiber between the axon hillock and the first glial cell
trigger zone
collectively, the axon hillock and initial segment; plays an important role in initiating a nerve signal
neuron doctrine
the theory that the nervous system is not a continuous "wire" or tube, but a series of separate cells separated by synapses
electrical potential
the difference in the concentration of charged particles between one point and another
autonomic nervous system (ANS)
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
visceral reflexes
unconscious, automatic, stereotyped responses to stimulation
preganglionic neuron
has a soma in the brainstem or spinal cord whose axon terminates in the ganglion; it synapses there with a postganglionic neuron
postganglionic neuron
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
sympathetic chain
ganglia (paravertebral ganglia) along each side of the vertebral column
spinal nerve route
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
sympathetic nerve route
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
adrenal cortex
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
vagus nerve
carries about 90% of all parasympathetic preganglionic fibers
nicotinic receptors
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
muscurinic receptors
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
cerebral cortex
is involved in many emotional responses and has extensive connections with the hypothalamus, a site of several nuclei of autonomic control
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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