Functions of the Nervous System
Terms in this set (19)
List the basic functions of the nervous system.
The nervous system maintains body homeostasis with electrical signals; provides for sensation, higher mental functioning, and emotional response; and activates muscles and glands
1. Monitor changes
2. Processes and interprets
3. Effects, or causes, a response
Explain the structural and functional divisions of the nervous system.
CNS - Brain and spinal cord (12 cranial nerves)(31 spinal nerves)
PNS - Outer regions of body
Somatic Afferents - from skin, skeletal muscles and joints
Visceral afferents - from guts
Somatic motor - voluntary nervous system
Autonomic nervous system - involuntary
Sympathetic - fight or flight
Parasympathetic - Rest and digest (SalivationLacrimationUrinationDefecation) SLUD
List the types of neuroganglia and cite their functions.
Neuroglia in the CNS include
astrocytes-A type of CNS supporting cell; assists in exchanges between blood capillaries and neurons;most abundant and most versatile glial cells
microglia-small ovoid cells with relatively long "thorny" processes; type of CNS supporting cell; can transform into phagocytes in areas of neural damage or inflammation
ependymal cells-range in shape from squamous to columnar, and many are ciliated; type of CNS supporting cell; lines the central cavities of the brain and spinal cord.
oligodendrocytes-A type of CNS supporting cell that composes myelin sheaths
Two kinds of PNS neuroglia
Satellite cells surround neuron cell bodies located in the peripheral neurons system (Figure 11.3e), but their function is still largely unknown.
Schwann cells (also called neurolemmocytes) surround and form myelin sheaths around the larger nerve fibers in the peripheral nervous
Define neuron, describe its important structural components, and relate each to a functional role.
The billions of neurons, also called nerve cells, are the structural units of the nervous system;Cell of the nervous system specialized to generate and transmit electrical signals (action potentials and graded potentials).
1. They have extreme longevity. Given good nutrition, neurons can function optimally for a lifetime (over 100 years).
2. They are amitotic. As neurons assume their roles as communicating links of the nervous system, they lose their ability to divide. We pay a high price for this neuron feature because they cannot be replaced if destroyed. There are exceptions to this rule. For example, olfactory epithelium and some hippocampal regions contain stem cells that can produce new neurons throughout life. (The hippocampus is a brain region involved in memory.)
3. They have an exceptionally high metabolic rate and require continuous and abundant supplies of oxygen and glucose. Neurons cannot survive for more than a few minutes without oxygen.
Differentiate between a nerve and a tract, and between a nucleus and a ganglion
Tract- CNS, collection of axons
Nerves - PNS, collection of axons
Nuclei - CNS collection of nerve bodies
Ganglia - PNS collections of nerve bodies
Explain the importance of the myelin sheath and describe how it is formed in the central and peripheral nervous systems
Myelin Sheath -whitish fatty segmented covering that protecs insulates and increases velocity of axons. Made of oliogodendric cells in the CNS and schwann cells in the PNS
(How is it formed?)
Classify neurons structurally and functionally
Multipolar - 3 or more processes, brain & spinal cord
Bipolar - signal axon and single dendrite, retina, inner ear and olfactory
Unipolar - Pseudounipolar, extends from cell body associated with receptors at the distal end of PNS
define resting membrane potential, state its typical value for neurons and describe its electrochemical basis (i.e. Describe how it is established and maintained in neurons)
RMP - Degree of the difference of eletrical charge between points. Typical value for neuron is -70mV
RMP Established via - permeability to ions. Mainly Na+ and K+ leaky channels and maintained by the Na+/K+Pumps. -- K+: most important factor, if ONLY K+ leaky channels RMP= -90mV. -- Na+: movement of sodium changes RMP to -70mV. moves into the cell due to chemical and electrical gradient. -- Negatively charged proteins (A-): adds to the electrical gradient.
Maintaining RMP - Na+/K+Pumps: help maintain 3 Na+out, 2 K+ in. [2/3 total energy expenditure of the Neuron]
Compare and contrast graded potentials and action potentials.
Topic: Graded | Action
Location: Dendrites/soma | Hillock/axon
Distance: Short | Long
Amplitude: Various/graded | Always the same
Potential: Decays | No Decay
Stimulus: Chemical (NT) | Voltage (Depolarization)
Summation: Temporal/Spatial | No (all or none)
Voltage change: +/- | +>-
Degree of change: Small | Large
Duration: ~1 ms | many ms
Explain how action potentials are generated and propagated along neurons.
Define absolute and relative refractory periods.
Absolute Refractory Period - Incapable of generating another action potential
Relative Refractory Period - Requires greater than normal amount of stimulation to generate another action potential
Compare and contrast saltatory and continuous conduction
Saltatory - to leap, High conduction velocity, found in myelinated axons
Continuous - Conduct impulses relatively slowly, Unmyelinated
Define synapse. Distinguish between electrical and chemical synapses by structure and by the way they transmit information.
Functional junction that mediates information transfer between neurons or between neurons and effector cells.
Electrical Synapse - Neurons that are electrically coupled via protein channels (gap junctions) and allow for the direct transfer of ions. Only in brains, eyes, and cardiac.
Chemical Synapses - Specialized for release and reception of chemical neurotransmitters. Make up the bulk of synapses.
Distinguish between excitatory and inhibitory postsynaptic potentials.
Postsynaptic Potential - Neurotransmitters that mediate graded potential on the postsynaptic cell
EPSP - Excitatory Postsynaptic Potential, Excitatory neurotransmitter opens Na+ channels and depolarizes the membrane
IPSP - Inhibitory Postsynaptic Potential, Inhibitory neurotransmitters opens either K+ or Cl- channels and hyperpolarizes the membrane
Describe how synaptic events are integrated and modified.
Integration - summation, Temporal & Spatial
Synaptic potentiation - when presynaptic cell is stimulated repeatedly/continously, enhancing the release of the neurotransmitter (like working out a muscle)
Presynaptic inhibition - when another neuron inhibit the release of excitatory NT from presynaptic cell
Neuromodulation - when a neurotransmitter acts via slow changes in target cell metabolism, or when chemicals other than NTs modify neuronal activity. EX: NO & adenosine
Define neurotransmitter and name several classes of neurotransmitters.
Chemical structure - ACh, Biogenic amines(dopamine, NE, E, serotonin, histamine), AA (GABA, glutamate, aspartate), Peptides (endorphins, substance P), Purines (ATP, adenosine), Gases and lipids (NO, CO)
Function - Effects (excitatory or inhibitory), Actions (direct: open channels, indirect: alter metabolism)
Describe common patterns of neuronal organization and processing.
CNS neurons are organized into several types of neuronal pools, each with distinguishing patterns of synaptic connections called circuits.
The four basic circuit types are diverging, converging, reverberating, and parallel after-discharge.
Distinguish between serial and parallel processing.
Serial Processing is the act of attending to and processing one item at a time in a sequential/deliberate/CONSCIOUS effort.
This is usually contrasted against Parallel Processing, which is the act of attending to and processing all items simultaneously. (For example, when we look at a picture in a book of a red balloon we don't have to think "that is a balloon, it is red, the grass is green, the sky is blue, the book is old"...our mind can look at the page and UNCONSCIOUSLY, simultaneously process the entire picture and those listed details in one mere glance.)
Describe how neurons develop and form synapses.
Neuron development involves proliferation, migration, and the formation of interconnections. The formation of interconnections involves axons finding their targets and forming synapses, and the synthesis of specific neurotransmitters.
Axon outgrowth and synapse formation are guided by other neurons, glial cells, and chemicals (such as N-CAM and nerve growth factor). Neurons that do not make appropriate synapses die, and approximately two-thirds of neurons formed in the embryo undergo programmed cell death.
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