Nervous System Function Flashcards
Central nervous system consists of which structures?
Brain & spinal cord
Peripheral nervous system consist of which structures?
cranial nerves, spinal nerves, ganglia, and also sensory & motor fibers.
Name the two divisions of the PNS
Sensory (afferent) & motor (efferent)
Sensory division of the PNS consists of which types of fibers:
somatic & visceral sensory nerve fibers which conduct impulses from receptor to CNS
Name the two motor divisions of the PNS
Somatic nervous system and ANS
Somatic nervous system function:
somatic/voluntary nerve fibers conduct impulses to skeletal muscles
What is the function of the Autonomic Nervous System (ANS)?
visceral/involuntary motor nerve fibers conduct impulses to smooth & cardiac muscles and glands
Name the main function of the Sympathetic Nervous System and some examples of how the body responds.
mobilizes body systems during activity (fight or flight); increases heart rate, blood flow, increase glucose, brachiodilation, reduced saliva, bladder restriction, dilated pupils, reduced peristalsis & secretion
Name the main function of the Parasympathetic nervous system and some examples of how the body responds.
conserves energy and promotes housekeeping during rest (rest & digest); stimulated salivary flow, lower heart rate, bronchiorestriction, stimulated peristalsis & secretion & bile release, bladder contraction, constricted pupils
Astrocytes
highly branched, most abundant glial cells, cling to neurons and capillaries, monitor/regulate/modify surrounding environment, regulate blood/brain barrier, can modulate neuron activity & strength of stimulus
Microglia
defensive cells of CNS, immune response; monitor health of neurons; are mobile and can change into macrophages if necessary
Ependymal cells
form sheets of cells and line CSF filled CNS cavities, contain cilia that beat and move CSF around which helps maintain health of CNS
Oligodendrocytes
have processes that form myelin sheaths around CNS fibers, increase velocity of impulses
Name the two types of neuroglia in PNS and their function.
Satellite cells- like astrocytes, surround cell body and monitor surrounding environment
Schwann cells- wrap axons with entire cell to form myelin sheath
Name the 4 special characteristics of neurons
extreme longevity, amitotic, high metabolic rate, possess a cell body and one or more processes
Name the clusters of neuronal cell bodies in the CNS and PNS
CNS- nuclei; PNS- ganglia
Name the clusters of axons in the CNS and PNS
CNS- tracts; PNS- nerves
Where is AP generated in axon?
Initial segment, after graded potentials converge on axon hillock
Myelin sheath function & type of conduction
Increase speed of impulses; saltatory conduction via more VGCs at nodes of Ranvier
Multipolar neurons
3+ processes; 1 axon & 2 or more dendrites; most common neuron
Bipolar neurons
2 processes; one axon and one dendrite; rare- found in ear, retina
Unipolar neurons
cell body offset from T-like axon; peripheral process assoc w/ sensory receptor and central process enters CNS (most sensory neurons are unipolar)
Sensory/afferent neurons
mainly unipolar, cell body in ganglia, transmit into CNS from PNS
Motor/efferent neurons
multipolar; cell body in nuclei & gray matter of CNS; carry impulses away from the CNS
Interneurons
remain in CNS, multipolar; connects sensory neurons to motor neurons
What causes hyperpolarization?
K+ leak channels slow closure
What are graded potentials?
short distance signals that depolarize a small part of the membrane, spreads via Na+ influx but decays over a distance due to leak channels
What is approximate threshold for an action potential?
-55mV
What is the extra state in voltage gated sodium channels?
Besides the open & closed state, they also have an inactivated state due to inactivation gate. Must return to closed state before it can reopen (absolute refractory period)
How is a strong AP created?
Increased frequency of stimulus.
How are action potentials prevented from going the wrong way?
The absolute refractory period, which is caused by the inactivation state of VGSCs.
What is the relative refractory period?
A period when most VGSCs are resetting and the threshold for generating an AP is elevated; stronger stimulus needed to overcome hyperpolarization
Multiple Sclerosis cause & remission
Auto-immune disease where oligodendrocytes are destroyed which slows impulses; remission is caused by demyelinated axons producing more Na+ channels; treated with immunosuppressants
Why are electrical synapses faster than chemical synapses?
the neurons are connected via gap junctions which allows ions to pass quickly between cells
What is a metabotropic receptor?
A GPCR in the post-synaptic neuron that binds a neurotransmitter. This binding triggers an intracellular cascade or it can alter the number of ionotropic receptors.
Excitatory Postsynaptic Potential
brings neuron closer to AP threshold; neurotransmitter binds chemically gated channel and opens for Na+ to move in
Inhibitory Postsynaptic Potential
causes hyperpolarization; neurotransmitter binds chemically gated channel allowing K+ to exit or Cl- to enter cell
What is temporal summation?
when impulses are fired more rapidly, EPSPs summate and reach threshold
Spatial summation
impulses summate from multiple synapses
Serial processing
Input travels along one pathway to a specific destination; all or nothing response (stimulus - receptor-sensory neuron-integration center- motor neuron- effector- response)
With this type of processing, input travels along several pathways and different part of circuitry deals simultaneously with the info. It’s important in higher level mental function.
Parallel processing
Diverging circuit
one input, many outputs (like a motor neuron to skeletal muscle)
Converging circuit
many inputs, one output; sensory stimuli elicit same memory
Reverberating circuit
signal travels through chain of neurons, each feeding back on previous neurons (important for controlling rhythmic activity)
Parallel after-discharge circuit
single input stimulates multiple parallel neurons which converge to a single output
