nervous system

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