nervous system- receives information, processes information, and sends out signals to the muscles and glands to elicit an appropriate response
nervous tissue- responsible for the communication between the cells of the body by forming a system of electrical impulses that communicate very rapidly
nuclei- collections of cell bodies inside the central nervous system
tracts- collection of nerve axons in the central nervous system
peripheral nervous system- includes all nerves not in the brain or spinal cord, connects all parts of the body to the central nervous system
brainstem- includes the midbrain, pons, and medulla
cranial nerves- project from the brainstem, generally innervate the face, head, and neck
spinal nerves- project from either side of the spinal cord, spread out to innervate the rest of the body, including the trunk and extremities
ganglia- collections of cell bodies inside the peripheral nervous system
nerves- collection of nerve axons in the peripheral nervous system
sensory (afferent) division- peripheral nervous system receives impulses from the sensory organs
motor (efferent) division- relays signals or impulses from the central nervous system to muscles and glands, can be divided into somatic and autonomic
somatic nervous system- generally under conscious (voluntary) control
autonomic nervous system- generally not under conscious control, controls the glands and smooth muscles of the internal organs, can be divided into sympathetic and parasympathetic
sympathetic nervous system- activates and prepares the body for vigorous muscular activity, stress, and emergencies
parasympathetic nervous system- generally operates during normal situations, permits digestion, and conserves energy
neurons- nerve cells that conduct electrical impulses and relay information throughout the body, do not undergo mitosis, can survive an entire lifetime, and can only go a few minutes without oxygen, Information is received and sent in the same direction
neuron cell body- synthesizes all nerve cell products, consists of a large nucleus with surrounding cytoplasm containing the normal organelles
dendrites- the receiving end of a neuron, numerous short extensions that emanate from the cell body, which receive information from other neurons and conduct those nerve impulses toward the cell body
axon- conducts nerve impulses away from the cell body to its axon terminals, can vary in length, composed of cell components but lack rough ER, depends upon the neuron’s cell body to send the necessary proteins down the length of the axon
neurotransmitters- produced by the cell body, chemicals stored inside secretory vesicles at the end of the axon terminals, carry the transmission of the nerve impulse from one neuron to another
synapse- a gap between two neurons, a path for neurotransmitters to cross neurons, fluid filled
presynaptic neuron- before the synapse, signal sending
postsynaptic neuron- a neuron found after the synapse, receiving neuron
multipolar neurons- have three or more extensions from the cell body, one axon and many dendrites, may be called motor neurons
bipolar neurons- a central cell body with two extensions, found as special receptor cells in the visual and olfactory systems
unipolar neurons- one extension off the cell body that branches into two: one central process running to the CNS and another peripheral process running to the sensory receptor. These neurons are sensory neurons in the peripheral nervous system.
sensory neurons (afferent)- unipolar, carry information from the peripheral to the central nervous system, most carry impulses from the skin or internal organs to the CNS
interneurons- found only in the central nervous system, typically multipolar neurons and transmit impulses within different parts of the central nervous system, connect neurons
motor neurons (efferent)- multipolar neurons, send messages from the central nervous system to the peripheral
nerve- consists of hundreds of thousands of axons wrapped together in a connective tissue
neuroglial cells- highly important for neuron function, support cells for neurons
Schwann cells- a special type of neuroglial cell found in the peripheral nervous system (PNS) and composed of a myelin sheath
myelin sheath- a white fatty layer, rolled around the axon, insulating the nerve fiber from others and increasing the speed of nerve impulses
nodes of Ranvier- gaps between the Schwann cell insulating sections
saltatory conduction- a way for the nerve impulse to jump to the next node
satellite cells- surround the cell bodies of peripheral neurons, helping to regulate the cell body environment
axonal regeneration- the Schwan cell grows ahead of the axon, creating a path for the axon to follow as it grows very slowly
ependymal cells- circulate cerebrospinal fluid and allow fluid exchange between brain, spinal cord, and cerebrospinal fluid
oligodendrocytes- act as the insulation for central nervous system axons
astrocytes- control the chemical environment of neurons by wrapping around the blood capillaries
blood brain barrier- the physical barrier of the astrocytes around the blood capillaries, allows the passage of only certain substances into the central nervous system
microglial cells- protect the CNS by scavenging dead cells and infectious microorganisms.
nerve impulse- an electrochemical charge moving along an axon created by the movement of unequally distributed ions on either side of an axon’s plasma membrane
polarized- at rest, one side of the plasma membrane has a different charge than the other side
resting potential- When the axon is not conducting an impulse, equal to about -70mV
sodium potassium pump- uses active transport to carry ions across the plasma membrane, for every three sodium pumped out, two potassium are pumped in.
action potential- the axon is stimulated to conduct a nerve impulse, rapidly changes the polarity, happens when the membrane becomes depolarized
Resting Potential- both sodium and potassium gates are closed.
Depolarization- The sodium gates open, and sodium rushes into the axon during the depolarization phase of the action potential. Voltage travels to zero and then on up to +40 mV.
Repolarization- The sodium gates close, and potassium gates open allowing potassium to rush out of the axon. This returns a negative voltage to the inside of the axon
Afterpolarization/hyperpolarization- Potassium gates close slowly, & there’s an undershoot of the potential. The voltage drops below -70mV and then back to -70mV as resting state begins.
self-propagating- the ion channels are prompted to open whenever the membrane potential decreases (depolarizes) in an adjacent area, travels the axon like a wave
acetylcholinesterase- breaks down the neurotransmitter acetylcholine
inhibition- Prevention of continuous stimulation
neurotransmitter examples- dopamine, epinephrine, norepinephrine, acetylcholine
neuromuscular junctions- in the peripheral nervous system, located where a motor neuron ends on a muscle instead of another neuron, contains acetylcholine
reflexes- nearly instantaneous, automatic, and involuntary motor responses
brainstem- regions include the midbrain, pons, and the medulla, control blinking the eye
reflex arc- the neural pathway that a nerve impulse travels,
dorsal root- where sensory info travels into the spinal cord, contains the axons of sensory neurons
grey matter- contains the cell bodies of the neurons, where neurons synapse with other neurons
white matter- contains the axons of neurons, surrounds the grey matter
dorsal root ganglion- contains cell bodies of sensory nerves
posterior horn- where sensory neurons synapse on cells
anterior horn- where motor neuron cell bodies are located
ventral root- where motor neurons leave the spinal nerve
spinal reflexes- occur faster than a conscious decision because they have fewer neurons, and don’t have to travel to the brain and back
stretch reflexes- a type of muscle reflex that protects the muscle against increases in length that may tear or damage muscle fibers, helps maintain upright posture
muscle spindles- specialized muscle cells that are constantly monitoring the amount of stretch in a muscle, triggers a reflex when overstretched
patellar reflex- prevents overstretching of the quadriceps
flexor withdrawal reflex- contracts the biceps and prevents contraction of the triceps to flex the elbow and remove it from heat