Chapter 11 Flashcards
Nervous system
A system that rapidly communicates information throughout the body; composed of the brain, the spinal cord, nerves, and ganglia
Ganglion
A mass of nerve cells in the peripheral nervous system that resembles a knot.
Peripheral Nervous System
The parts of the nervous system outside of the brain and spinal cord; composed of nerves and ganglia.
Central Nervous System
The brain and spinal cord.
Electrical Potential
The brain and spinal cord.
Current
A moving cluster of charged particles.
Stress
A condition that upsets homeostasis and stimulates a physiological response.
Alarm
This step is your body’s immediate reaction to stress and it prepares you to fight or escape danger caused by stress. The body consumes large quantities of stored glycogen to handle the physical symptoms of stress.
Resistance
Longer stress stimuli (more than a few hours) deplete the body’s glycogen reserves, and the body must provide alternative and less efficient fuels, such as fat, for metabolism. Under sustained conditions, the body has trouble fighting off infections and maintaining hormone levels.
Exhaustion
- After a longer time period (months) the body uses all its fat storage. When this store is depleted, homeostasis is upset and the body begins breaking down protein for energy, resulting in the depletion of muscle and overall weakness that can lead to heart or kidney failure and infections.
The sensory division - PNS
transmits action potentials to the CNS.
The motor division - PNS
carries action potentials away from the CNS.
The somatic nervous system - Motor division - PNS
innervates skeletal muscle and is mostly under voluntary control.
The autonomic nervous system (ANS) - Motor - PNS
innervates cardiac muscle, smooth muscle, and glands.
The enteric nervous system
controls the digestive system.
Glial cells - CNS
are supportive cells that support and aid the neurons of the CNS and PNS.
Astrocytes - CNS
provide structural support for neurons and blood vessels. Astrocytes influence the functioning of the blood-brain barrier and process substances that pass through it. Astrocytes isolate damaged tissue and limit the spread of inflammation. Astrocytes also help maintain synaptic function.
Ependymal cells - CNS
line the ventricles and the central canal of the spinal cord. Some are specialized to produce cerebrospinal fluid.
Microglia - CNS
phagocytize microorganisms, foreign substances, and necrotic tissue.
An oligodendrocyte - CNS
forms myelin sheaths around the axons of several CNS neurons.
A Schwann cell - PNS
forms a myelin sheath around part of the axon of a PNS neuron.
Satellite - PNS
cells support and nourish neuron cell bodies within ganglia.
Myelinated axons
are wrapped by several layers of plasma membrane from Schwann cells (PNS) or oligodendrocytes (CNS). Spaces between the wrappings are the nodes of Ranvier. Myelinated axons conduct action potentials rapidly.
Unmyelinated axons
rest in invaginations of Schwann cells (PNS) or oligodendrocytes (CNS). They conduct action potentials slowly.
White matter
consists of myelinated axons; it propagates action potentials. forms nerve tracts in the CNS and nerves in the PNS.
Gray matter
consists of collections of neuron cell bodies or unmyelinated axons. Axons synapse with neuron cell bodies, which are functionally the site of integration in the nervous system. forms cortex and nuclei in the CNS and ganglia in the PNS.
Neuron communication can be described in three phases
Generation of action potential
Propagation of action potential
Communication with target cell at the synapse
A graded potential
is a small change in the resting membrane potential that is confined to a small area of the plasma membrane. The term graded potential is used because a stronger stimulus produces a greater potential change than a weaker stimulus.
The absolute refractory period
is the time during an action potential when a second stimulus, no matter how strong, cannot initiate another action potential.
The relative refractory period
follows the absolute refractory period and is the time during which a stronger-than-threshold stimulus can evoke another action potential.
A subthreshold stimulus
produces only a graded potential.
A threshold stimulus
causes a graded potential that reaches threshold and results in a single action potential.
A submaximal stimulus
is greater than a threshold stimulus and weaker than a maximal stimulus. The action potential frequency increases as the strength of the submaximal stimulus increases.
A maximal or a supramaximal stimulus
produces a maximum frequency of action potentials.
Electrical synapses
are gap junctions in which tubular proteins called connexons allow local currents to move between cells.
The enlarged ends of the axon - Chemical synapse
are the presynaptic terminals containing synaptic vesicles.
The postsynaptic membranes - Chemical synapse
contain receptors for the neurotransmitter.
The synaptic cleft - chemical syanpse
is a space separating the presynaptic and postsynaptic membranes
Convergent pathways
have many neurons synapsing with a few neurons.
Divergent pathways
s have a few neurons synapsing with many neurons.
Reverberating circuits
have collateral branches of postsynaptic neurons synapsing with presynaptic neurons.
Parallel after-discharge circuits
have neurons that stimulate several neurons arranged in parallel that stimulate a common output.
