The Nervous System Ch 13 Flashcards
What are the neurons?
- basic functional units of the nervous system
- high requirement for oxygen
- cannot reproduce but can regenerate cell processes if the cell body remains intact
What are neuroglia (glial cells)?
provide structural, functional support and protection to neurons
What is the neuron structure?
central cell body - (soma or perikaryon)
cell processes - dendrites - receive stimuli
- axons - conducts nerve impulses
away
What are dendrites?
- receive stimuli from other neurons and conduct the stimuli to the cell body
- May serve as sensory receptors for heat, cold, touch, pressure, stretch, or other physical changes from inside or outside the body
- short, numerous, multibranched
What are axons?
- conduct nerve impulse away from cell toward another neuron or an effector cell
- single, long process; may be covered with myelin
- white matter: tissue containing myelinated axons
What are myelinated axons?
conduct impulses faster than unmyelinated ones
What is the myelin sheath?
cell membrane of glial cells tightly wrapped around the axon
- Olligodendrocytes in the brain and spinal cord
- schwann cells in the nerves outside the brain and spinal cord
Multiple Schwann cells or the _______ cover the entire length of the axon.
oligodendrocytes
Nodes of Ranvier: gaps between adjacent _____ cells
glial
The organization of nervous system includes?
Anatomical, Direction of impulses
Anatomical includes?
central nervous system (CNS),
Peripheral nervous system (PNS),
The central nervous system includes?
brain and spinal cord - anything surrounded by spinal canal
The peripheral nervous system which extends outward form the central axis toward the periphery of the body includes?
cranial nerves which originate directly from the brain and spinal nerves which emerge from the spinal cord
What are efferent nerves?
conduct impulses away from CNS - also called motor nerves - cause skeletal muscle contraction and movement
What are afferent nerves?
conduct impulses toward CNS - also called sensory nerves - conduct sensations from sensory receptors in the skin and other locations in the body to the CNS
What is autonomic function in the nervous system?
controls and coordinates automatic functions
Ex.: slowing of the heart rate in response to an increased blood pressure
What is somatic function in the nervous system?
actions under conscious, or voluntary, control
Neuron function?
sodium potassium pump; specialized molecule that helps maintain cell resting state
- Pumps (Na+) from inside of neuron to the outside
- pump (K+) from outside of neuron to the inside
What is deplorization - action potential?
during depolarization, inside of the neuron goes from a negatively charged resting membrane potential to a net positive charge due to inflow of sodium ions
- creates large change in electrical charge from negative to positive
Depolarization is?
neuron receives external stimulus
sodium channel opens on neuron cell membrane
sodium ions flow into cell by passive diffusion
Repolarization?
sodium channels close K+ channels open K+ diffuses out of the cell resting state restored - as repolarization ends, sodium-potassium pump moves sodium and potassium ions back to their original sides resting state restored
Threshold stimulus?
stimulus must be sufficient to make the neuron respond and cause complete depolarization
- “all or nothing principle” neuron depolarizes to its maximum strength or not at all
- conduction of the action potential - spreading wave of opening sodium channels in sufficient numbers to allow sodium influx and depolarization - wave of depolarization or nerve cells
What is saltatory conduction?
rapid means of conducting an action potential
depolarization in myelinated axons can only take place at the nodes of Ranvier
Synapse?
junction between two neurons or a neuron and a target cell
Synaptic cleft?
gap between adjacent neurons
Presynaptic neuron?
neuron bringing the depolarization wave to the synapse - releases neurotransmitter
Postsynaptic neuron?
contains receptors for the neurotransmitter
Telodendron?
branched structure on presynaptic neuron
Terminal bouton?
slightly enlarged bulb on each of teledendron (synaptic end bulb, synaptic knob)
Vesicles in the knob contain the neurotransmitter
When _______ wave reaches synaptic knob vesicles fuse with the knob’s cellular membrane and dump neurotransmitter into the synaptic cleft
depolarization
Neurotransmitters diffuse across the ____ ____ toward the postsynaptic membrane
synaptic cleft
_______ on the postsynaptic membrane bind the nerotransmitter
Receptors
What are excitatory neurotransmitters?
usually cause an influx of sodium so that the postsynaptic membrane moves toward threshold
Inhibitory neurotransmitter?
move the charge within the postsynaptic cell farther away from threshold
What are the types of neurotransmitters?
acetylcholine, catecholamines, gamma-aminobutyric acid (GABA) and glycine
Acetylcholine?
can be excitatory or inhibitory depending on its location in the body