For the following neuron structure, provide a brief description of its purpose:
Axon
The axon transmits an electrical signal (the action potential) from the soma to the synaptic knob.
For the following neuron structure, provide a brief description of its purpose:
Axon Hillock
The axon hillock integrates excitatory and inhibitory signals from the dendrites and fires an action potential if the excitatory signals are strong enough to each threshold.
For the following neuron structure, provide a brief description of its purpose:
Dendrite
Dendrites receive incoming signals and carry them to the soma.
For the following neuron structure, provide a brief description of its purpose:
Myelin Sheath
The myelin sheath acts as insulation around the axon and speeds conduction.
For the following neuron structure, provide a brief description of its purpose:
Soma
The soma is the cell body and contains the nucleus, endoplasmic reticulum, and ribosomes.
For the following neuron structure, provide a brief description of its purpose:
Synaptic bouton
The synaptic bouton lies at the end of the axon and releases neurotransmitters.
What is the collection of cell bodies called in the CNS?
nucleus
What is the collection of cell bodies called in the PNS?
ganglion
Which two types of glial cells, if not functioning properly, will make an individual most susceptible to a CNS infection?
Astrocytes nourish neurons and form the blood brain barrier, which helps protect the brain from foreign pathogens gaining entrance.
Microglia ingest and break down waste products and pathogens.
Disruption of either of these mechanisms would increase susceptibility to CNS infection.
Guillain-Barre syndrome (GBS) is an autoimmune disease that causes demyelinated action in the PNS. What type of glial cell is being targeted in GBS?
Oligodendrocytes produce myelin in the CNS, while Schwann cells produce myelin in the PNS. Since GBS causes demyelination in the PNS, it can be inferred that Schwann cells are targeted for immune destruction.
What neural structure initiates the action potential?
Axon hillock
What entity maintains the resting membrane potential? What is the approximate voltage of the resting membrane potential?
Na+/K+ ATPase at approximately -70 mV
What is the difference between temporal and spatial summation?
Temporal summation is the integration of multiple signals close to each other in time.
Spatial summation is the integration of multiple signals close to each other in space.
During an action potential, which ion channel opens first?
How is this ion channel regulated?
What effect does the opening of this channel have on the polarization of the cell?
Ion Channel: Na+ opens first at threshold (around -50 mV)
Regulation: inactivation, which occurs around +35 mV
Effect on polarization: inactivation can only be reversed by repolarizing the cell. The opening of the sodium channel causes depolarization.
During an action potential, which ion channel opens second?
How is this ion channel regulated?
What effect does the opening of this channel have on the polarization of the cell?
Ion Channel: K+ opens second at approximately +35 mV
Regulation: closing at low potentials (slightly below -70 mV)
Effect on polarization: The opening of the potassium channels causes repolarization and, eventually hyperpolarization
What is the difference between the absolute and relative refractory period?
During the absolute refractory period, the cell is unable to fire an action potential regardless of the intensity of a stimulus.
During the relative refractory period, the cell can fire an action potential only with a stimulus that is stronger than normal.
What ion is primarily responsible for the fusion of neurotransmitter-containing vesicles with the nerve terminal membrane?
Calcium
What are the three main methods by which a neurotransmitter action can be stopped?
Enzymatic degradation
Reuptake
Diffusion
What parts of the nervous system are in the CNS?
brain and spinal cord
What parts of the nervous system are in the PNS?
cranial and spinal nerves and sensory nerves
What do afferent neurons do?
Afferent (sensory) neurons bring signals from a sensor to the CNS.
What do efferent neurons do?
Efferent (motor) neurons bring signals from the CNS to an effector.
What functions are accomplished by the somatic nervous systen?
voluntary actions- most notably, moving muscles
What functions are accomplished by the autonomic nervous system?
involuntary processes like heart rate, bronchial dilation, dilation of the pupils, exocrine gland function, and peristalsis
What are the effects of the sympathetic nervous system?
"fight or flight" response
increased heart rate and bronchial dilation
redistribution of blood to locomotor muscles
dilation of the pupils
slowing of digestive and urinary functions
What are the effects of the parasympathetic nervous system?
"rest and digest" function
slowing heart rate and constricting the bronchi
redistributing blood to the gut
promoting exocrine secretions
constricting the pupils
promoting peristalsis and urinary function
What is the pathway of neural impulses in a monosynaptic reflex?
A sensory (afferent, presynaptic) neuron fires directly onto a motor (efferent, postsynaptic) neuron.
What is the pathway of neural impulses in a polysynaptic reflex?
A sensory neuron may fire directly onto a motor neuron, but interneurons are used as well. These interneurons fire onto other motor neurons.