Bio Ch 37 Flashcards
Nerve net
composed of neurons in contact with one another and with contractile cells of the body wall in cnidarians
Cephalization
concentration of nervous tissue in the anterior or head region
Ganglion
cluster of neuron cell bodies
Central Nervous System (CNS)
brain, spinal cord
Peripheral Nervous System (PNS)
nerves, ganglia that lie outside the CNS
Neurons
nerve cells; functional units of the nervous system
Neuroglia
supporting cells, providing support and nourishment to the neurons
Cell body
contains a nucleus and a variety of organelles
Dendrites
short, highly branched processes that receive signals from the sensory receptors or other neurons and transmit them to the cell body
Axon
portion of the neuron that conveys info to another neuron or to other cells; can be bundled to form nerves
Nerve fibers
axons are often called this; many are covered by a myelin sheath
Myelin sheath
white insulating layer covering axons
Microglia
phagocytic cells that help remove bacteria and debris
Astrocytes
provide metabolic and structural support directly to the neurons
Schwann cells
cells that surround a fiber of a peripheral nerve and forms the myelin sheath
Nodes of Ranvier
gaps in the myelin sheath
Oligodendrocytes
in the CNS, these neuroglial cells form the myelin sheath
Motor (efferent) neurons
take nerve impulses from the CNS to muscles or glands
Sensory (afferent) neurons
take nerve impulses from sensory receptors to the CNS
Interneurons
occur entirely within the CNS; typically multipolar; convey nerve impulses between various parts of the CNS
Resting potential
membrane potential of an inactive neuron
Action potential
rapid change in polarity across a portion of an axonal membrane as the nerve impulse occurs
Saltatory conduction
action potential “jumps” from node to node (saltar in Spanish = to jump)
Refractory period
time following an action potential when a neuron is unable to conduct another nerve impulse
Synapse
junction between neurons consisting of the presynaptic (axon) membrane, the synaptic cleft, and the postsynaptic (usually dendrite) membrane
Synaptic cleft
the small gap between neurons
Neurotransmitters
transmission across a synapse is carried out by molecules called this, which are stored in synaptic vesicles
Axon hillock
area of the neuron cell body where the axon emerges
Integration
summing up of excitatory and inhibitory signals
Meninges
both the spinal cord and the brain are wrapped in 3 protective membranes known as this
Cerebrospinal fluid
the spaces between the meninges are filled with this, which cushions and protects the CNS
Ventricles
interconnecting spaces that produce and serve as reservoirs for cerebrospinal fluid
Meningitis
inflammation of the meninges; serious disorder caused by a number of bacteria or viruses that can invade the meninges
Spinal cord
bundle of nervous tissue enclosed in the vertebral column; extends from the base of the brain to the vertebrae just below the rib cage
Reflex actions
automatic responses to external stimuli
Gray matter
consists of cell bodies and unmyelinated fibers
Tracts
bundle of myelinated axons in the CNS
White matter
myelinated axons in the CNS
Amyotrophic Lateral Sclerosis (ALS)
AKA Lou Gehrig’s Disease; motor neurons in the brain and spinal cord degenerate and die, leaving patients weakened, then paralyzed, then unable to breathe properly
Brain
allows us to perceive our environment, reason, and remember
Cerebrum
largest, outermost portion of the brain in humans
Cerebral hemispheres
cerebrum is divided into 2 halves, called this
Sulci (sing, = sulcus)
shallow grooves that divide the brain into lobes
Cerebral cortex
thin, but highly convoluted, outer layer of gray matter that covers the cerebral hemispheres
Stroke
when the blood supply to the brain is disrupted; 3rd leading cause of death in the US; most common type is ischemic (sudden loss of blood supply to an area of the brain, usually due to arterial blockage or clot formation)
Basal nuclei (basal ganglia)
integrate motor commands, ensuring that proper muscle groups are activated or inhibited
Parkinson Disease (PD)
brain disorder characterized by tremors, speech difficulties, and difficulty standing and walking; results from a loss of cells in the basal nuclei that normally produce the neurotransmitter dopamine
Hypothalamus
floor of the 3rd ventricle; integrating center that helps maintain homeostasis by regulating hunger, sleep, thirst, body temperature, and water balance; controls the pituitary gland; link between nervous and endocrine systems
Thalamus
consists of 2 masses of gray matter located in the sides and roof of the 3rd ventricle; receives all sensory input except smell; “gatekeeper” for sensory info en route to the cerebral cortex; participates in higher mental functions such as memory and emotions
Pineal gland
secretes melatonin; located in the diencephalon
Cerebellum
lies under the occipital lobe of the cerebrum and is separated from the brain stem by the 4th ventricle; largest part of the hindbrain
Brain stem
contains the midbrain, pons, medulla oblongata
Midbrain
relay station for tracts passing between the cerebrum and the spinal cord or cerebellum
Pons
contains bundles of axons that form a bridge traveling between the cerebellum and the rest of the CNS; works with the medulla oblongata to regulate many basic body functions
Medulla oblongata
lies just superior to the spinal cord; contains tracts that ascend or descend between the spinal cord and higher brain centers; regulates heartbeat, breathing, swallowing, and blood pressure; contains reflex centers for vomiting, coughing, sneezing, hiccuping, and swallowing
Multiple Sclerosis (MS)
most common neurological disease of young adults; typically affects myelinated nerves in the cerebellum, brain stem, basal ganglia, and optic nerve; autoimmune disease in which the patient’s own white blood cells attack the myelin, oligodendrocytes, and eventually neurons in the CNS
Reticular Activating System (RAS)
contains the reticular formation, a complex network of nuclei and nerve fibers that extend the length of the brain stem
Limbic system
complex network of tracts and nuclei that incorporate medial portions of the cerebral lobes, the basal nuclei, and the diencephalon; blends higher mental functions and primitive emotions into a united whole
Hippocampus
seahorse-shaped structure that lies deep in the temporal lobe; well situated in the brain to make the prefrontal area aware of past experiences stored in sensory association areas
Amygdala
can cause experiences to have emotional overtones
Memory
ability to hold a thought in mind or recall events from the past
Alzheimer Disease (AD)
most common cause of dementia, or a loss of reasoning, memory, and other higher brain functions, especially in people over 65
Nerves
bundles of axons
Cranial nerves
humans have 12 pairs of these attached to the brain; some are sensory, some are motor, others are mixed sensory/motor; largely concerned with the head, neck, and facial regions of the body
Spinal nerves
humans have 31 pairs of these that emerge from the spinal cord via 2 short branches/roots
Dorsal root ganglion
cell body of a sensory neuron
Somatic system
part of the PNS that serves the skin, joints, and skeletal muscles; includes nerves that take sensory info from external sensory receptors in the skin and joints to the CNS and carry motor commands away from the CNS to the skeletal muscles
Sensory receptors
generate nerve impulses that move along sensory axons through a dorsal root ganglion toward the spinal cord
Effector
nerve impulses travel along motor axons to this, which brings about a response to the stimulus; can be a gland
Autonomic system
part of the PNS that regulates the activity of cardiac and smooth muscle and glands; carries out its duties without our awareness or intent; divided into sympathetic and parasympathetic divisions
Sympathetic division
division of the autonomic system that is active when an organism is under stress; uses norepinephrine as a neurotransmitter
Parasympathetic division
includes a few cranial nerves (e.g. the vagus nerve) and also fibers that arise from the sacral (bottom) portion of the spinal cord; often referred to as the craniosacral portion of the autonomic system; sometimes called the “housekeeper” or “rest and digest division”; uses acetylcholine (ACh) as a neurotransmitter
