Chapter 11: Nervous System Flashcards
What 3 things does the nervous system do?
- Sensory input: protects environment
- Integration: processes input
- Motor output: respond
What does the CNS consist of?
Brain and spinal cord
Integrative and control centers
What does the PNS consist of?
Cranial nerves and spinal nerves
Communication between CNS and rest of the body
What does the sensory division consist of?
Somatic and visceral sensory nerve fibers
Transmits info to the CNS
What does the motor division consist of?
Motor nerve fibers
Transmits info away from the cns
What does the somatic nervous system consist of?
Somatic motor (voluntary) Conducts impulses from CNS to skeletal muscles
What does the ANS consist of?
Visceral motor (involuntary) Conducts impulses from CNS to cardiac and smooth muscles and glands
What are the 2 principal cell types in the nervous system?
- Neuroglia (glial cells): supporting cells
2. Neurons: excitable cells that transmit information
Why is the nervous system fragile?
There is no connective tissue so it is held together by cells
What are astrocytes?
CNS
The most abundant, versatile, and branched glial cells.
Cling to neurons, synaptic endings, and capillaries.
Support and brace neurons.
Help determine capillary permeability.
Regulate environment of the neurons and presence of neurotransmitters.
Holds the CNS together by wrapping around other structures that are present in the nervous system.
What are microglia?
CNS. Small cells with thorny processes. Migrate toward injured neurons. Phagocytize microorganisms and neuronal debris. Rough equivalent of macrophage.
What are ependymal cells?
CNS.
Line the central cavities of the brain and spinal column.
Separate CNS interstitial fluid from cerebrospinal fluid.
Produce CSF at choroid plexuses.
Sometimes connected by tight junctions; sometimes have cilia.
Play a key role in synthesis of cerebral spinal fluid and reabsorption in the spinal cord.
What are oligodendrocytes?
CNS
Branched cells.
Processes wrap around multiple axons in CNS, forming insulating myelin sheaths.
Multiple sclerosis (demylination in the CNS).
Produce myelin.
This makes communication faster and serve as a means of protection against physical injury and the scaffolding in the repair of axons.
What are satellite cells?
PNS.
Equivalent of astrocytes.
Surround neuron cell bodies in the PNS.
Regulate conditions present in the soma.
What are Schwann cells?
PNS.
Equivalent to oligodendrocytes and do almost everything they do.
Very small cells.
Surround peripheral nerve fibers and form myelin sheaths.
Vital to regeneration of damaged peripheral nerve fibers.
What are the special characteristics of neurons?
Long-lived (100+ years)
Amitotic
High metabolic rate
Plasma membrane functions in electrical signaling and cell-to-cell interactions during development
What is the difference between the structural class of a multipolar and unipolar neuron?
Multipolar: many processes extend from cell body and all are dendrites except for one axon.
Unipolar: one process extends from the cell body and forms central and peripheral processes, which make up an axon
What neuron type is the most abundant and has a common structure?
Multipolar
What type of neuron is the 1st order neuron in all sensory pathways?
Unipolar
What type of neuron are the 2nd and 3rd order neurons in all sensory pathways?
Multipolar
What are the function and properties of dendrites?
Receive info.
Found on 2nd order neuron.
Increase surface area –> increase # of synapses.
What is the function of the soma?
Receives and transmits info
What is the function of the axon?
Outgoing info
What are the parts of the axon?
- Axon hillock: generate new AP
- Axon branches
- Terminal or bouton
- Myelin
- Nodes of Ranvier
What are Nodes of Ranvier and where are they found?
Gap between myelin that is only found on myelinated axons
How is myelin distributed on an axon?
Found in intervals
Myelin - no myelin - myelin - no myelin
What does white matter consist of and what occurs in it?
Myelinated fibers (axons). Sensory pathways travel through myelinated white matter
What does gray matter consist of and what occurs in it?
Dendrites and somas (unmyelinated).
Communication between neurons in the sensory and motor pathways.
How do myelin sheaths work in the PNS?
Myelin sheath will wrap around an axon in one location - can be multiple wrappings, but only one location.
How do myelin sheaths work in the CNS?
Oligodendrocytes are big cells: one soma with many branches that reach out to multiple different axons simultaneously.
One oligodendrocyte can wrap around multiple different axons, or the same axon in multiple locations.
Can have 50 different wrappings per cell.
Wrappings are independent of each other.
Nucleus does not have to be associated with the wrappings themselves.
How do neurons function?
Neurons are highly irritable (excitable) and respond to adequate stimulus by generating an AP, which is always the same regardless of stimulus.
What are the principles of electricity?
- More positive charges outside cell than inside cell.
- Energy is required to separate opposite charges across a membrane.
- If opposite charges are separated, the system has potential energy.
- Energy is liberated when the charges move toward one another.
What is voltage?
Measure of potential energy difference.
Average voltage in neurons: -70 mV
What is potential difference?
Voltage measured between 2 points.
What is resistance (R)?
Hindrance to charge flow (provided by plasma membrane)
Resist change
What are insulators?
Substances with high electrical resistance (Myelin)
Perfect resistor
What are conductors?
Substance with low electrical resistance (water with electrolytes)
Allow/part of change.
Integral proteins: facilitate movement of ions across membrane
