lecture 20 Flashcards
the three basic functions of the nervous system
sensory input
integration
motor output
describe the three basic functions of the nervous system
o Sensory input – when the senses in the body are sent to the brain. When the body is in pain a pain signal is sent to the brain
- Comes from the sensor receptors in the eyes
o Integration – this is when the brain takes the sensory input, and it receives the information to then interpret it and decide on what to do with the information
o Motor output – this is where the integration of the sensory input is then put into some kind of action.
central nervous system
CNS - the brain and spinal cord
- works to integrate and act as a control system for the body
peripheral nervous system
(PNS) - the nerves and ganglia outside of the CNA
- all of the nerves and collections of bodies/substances outside of the CNS
The PNS functional divisions
Afferent (sensory) division
Efferent (motor) division
afferent division
the sensory division, is like the sensory signal we feel if we were to touch the flame of a candle. This sensory signal is then sent to the CNS.
efferent division
the motor division, when a signal is sent from the CNS out to the body to create a movement or do something specific.
the somatic nervous system
- Somatic nervous system: signals to the skeletal muscles, is voluntary
o Example is picking up a pencil. This is efferent and somatic.
autonomic nervous system
- Autonomic nervous system: signals to cardiac muscle, smooth muscle, or glands; is voluntary
- these things the nervous system does automatically for us
neuron
a cell that generates action potentials and sends them to other cells
Neuroglia (glial cells)
generally work to support the neurons, are much smaller
o Identify which parts of a neuron receive information, which part integrates information, and which part conducts the output signal
Axon hillock -> is where the action potential begins. This is the region that tapers out almost like a hill and is where the signals are integrated.
Axolemma -> is known as the plasma membrane of the axon
Terminal branches -> where each branch of the cell can communicate with a cell
Axon terminals -> these are the ends of the axon where the neurotransmitters are
cell body of the neuron
is the control center region where most of the organelles are
dendrite of the neuron
the shorter branching projections that come off the body
* There can be hundreds of dendrites coming off each body
axon of the neuron
typically larger than the dendrite. There is only one per cell and it travels to communicate with other cells. Is a very long structure.
* An axon can travel all the way from the toe and up to the spinal cord or the brain. The axon sends signals away from the neuron.
astrocyte
is a classification of a neuron in the CNS
named for their shape, have a star shape. Most abundant of all the glial cells.
* They help support and anchor the neurons, help with exchange between neurons and capillaries (exchange of nutrients and wastes), help to clean up leaked ions, might be helping the neurons to process information
- most abundant and versatile
microglial cells
is a classification of a neuron in the CNS
- Help to monitor the health of neurons. If there is damage, they can migrate to the site of injury and transform into macrophages to help clean up the area.
ependymal cells
is a classification of a neuron in the CNS
- line up together to form a sheet, they have cilia. Looks almost like epithelial tissue cells.
* Their job is to produce and circulate cerebral spinal fluid. The cilia waves around which help to circulate this.
oligodendrocyte
a classification of a neuron in the CNS
have branches that come off and wrap around the nerve fibers in the CNS (wrap around the axons).
* What produces the myelin sheath in the CNS.
satellite cells
a classification a a neuron in the PNS
surround the neurons cell bodies
* Like astrocytes but are outside of the CNS.
- look like satellites
schwann cells
this is a type of classification of neuron in the PNS
are responsible for forming the myelin sheath in the PNS
describe the function and composition of the myelin sheath
Not all axons have one, but if it does have one, we can call it myelinated.
Formed by the plasma membrane of the glial cells wrapping around the plasma membrane.
* Protects and electrically insulates the axons (helps with signal transmission). The myelin sheath speeds up the nerve impulse transmission.
o With the sheath signals travel hundreds of times faster.
The Schwann cell will wrap around the axon many times allowing for protection
what do oligodendrocytes do for the myelin sheath
they can wrap around multiple axons (one can wrap around up to 60 at one time)
what are nodes of Ranvier
these are the gaps between the Schwann cells that are found.
* These are very important and about a millimeter apart all the way down the axon. It allows the signal to jump from one node to the next, which is referred to as saltatory conduction.
