chapter 3 Flashcards
what is the central nervous system (CNS)?
brain and spinal cord. coordinating center for information.
what is the nervous system?
it is a elaborate communication system with more than 100 billion nerve cells in the brain.
what is the peripheral nervous system (PNS)?
nerves that carry information from CNS to the body.
within the PNS what is the somatic?
the skeletal muscles, bones, skin, and sensory information.
within the PNS what is the automimic?
the control of the internal organs. like blood flow or heart rate (involuntary)
what is the glial cell or the neuroglial cell?
nonconducting cells for structural support and metabolism of nerve cells.
what does the neuron do?
conducts nerve impulses. its a functional unit of nerve.
what is the dendrite part of the neuron?
cytoplasm projection that carries impulses toward the cell body.
what is the axon part of the neuron?
cytoplasm extension that carries impulses away from cell body. one axon per neuron, may have many branches. larger diameter makes impulse travel faster.
what is the myelin sheath part of the neuron?
insulated covering over the axon. prevents loss of ions.
what is the Schwann cells in the neuron?
it produces myelin sheath.
what is the nodes of Ranvier in the neuron?
it is the gaps between the myelin sheath sections on the axon. impulses jump between nodes which makes impulse faster.
what is the neurilemma part of the neuron?
the delicate membrane surrounding PNS nerves. promotes regeneration of damaged nerves. CNS does not have this permanent damage.
what is the sensory afferent neuron?
carries impulse to CNS.
what is the ganglia or ganglion
clusters of nerve cell bodies outside of CNS which make up sensory receptors.
what are the sensory receptors?
modified dendrites activated by environmental stimulus. gives info to neuron.
what are the interneurons or association neurons?
they link neurons to other neurons.
~only in brain and spinal cord. intercept sensory information.
~connect sensory neurons to motor neurons.
what are the motor neurons or efferent neurons?
carried impulse from CNS to effector.
what is the effector?
cell or organ that responds to a stimulus like the muscles, organs, and glands.
what is the reflex arch?
reflexes are involuntary.
what is the reflex arc?
neural circuit through spinal cord. the simplest nerve.
what are the 5 components with the reflex arch?
- sensory receptor
- sensory neuron
- interneuron
- motor neuron
- effector (muscle)
what is action potential and the steps associated?
the voltage difference across a nerve when it is excited.
1.nerve receives stimulus
2. sodium flows into cell and charge is reversed- depolarization
3.sodium channels close and potassium channels open. change outside cell becomes positive again- repolarization.
4. potassium gates are slow to close. outside of the cell becomes more positively charged then the resting membrane- hyperpolarization.
5. sodium- potassium pump restores resting membrane condition. refractory period 1-10ms.
6. membrane must return to resting potential before another action potential can occur.
what is resting potential?
voltage difference across a nerve when it is excited.
what does -70mv mean?
difference between number of positive charges on the inside relative to the outside of the membrane.
what does -90mv mean?
even fewer positives on the inside.
what is saltatory conduction?
action potential only at the nodes of ranvier. makes nerve impulse faster.
what is the threshold level?
the minimum level of stimulus required to produce a response.
what is the all-or-none response?
a nerve responds completely or not at all.
change in the stimulus is due to the frequency of impulses sent. so what is the warm glass verses hot class analogy?
warm does not send impulses as frequently. each nerve has many individual neurons. the number of neurons that fire also cause the intensity of response to change.
what is the synapse?
region between neurons or neurons and effectors.
what is the presynaptic neuron?
neuron that takes impulse to the synapse.
what is the post synapse?
neuron that carries impulse away from synapse.
what are the neurotransmitters?
chemicals released by presynaptic neuron that binds to receptors of postsynaptic neuron. more synapses= slower transmission speed.
what is acetylcholine?
makes post synaptic membrane more perkable to na+
what is cholinesterase?
an enzyme that breaks down acetylcholine. once acetylcholine is broken down na+ channels close and neuron is in recovery phase.
what is summation?
accumulation of neurotransmitters from 2 or more neurons.
