Chapter 5 Flashcards
Soma
Cell body
Dendrite
Branches of neural membrane from the cell body. receives messages from other neurons in the nervous system.
Axon
Long branch of neural membrane. The transmitting antenna of the nerve cell. Takes an electrical signal from the cell body out to its end where it delivers the message to another neuron.
Axon Hillock
Most proximal piece of the axon. The spot where the electrical signal is created.
Presynaptic terminal
The bit of neural membrane that is before the synapse and that delivers the information to the synapse.
Synaptic cleft
Space of the synapse
Postsynaptic terminal
The dendrite or cell body that receives the chemical message that has been delivered across the synapse
4 functions of Neurons
Receives chemical messages from other neurons.
Integrate all of the input into one common message.
Transmit the signal electrically from cell body to the presynaptic membrane.
transfer across the synapse.
Anterograde
in the usual direction of function
Retrograde
backwards of the usual direction of function
Bipolar neuron
Two major trunks extended away from the cell body. One major trunk is the dendritic branch and the other major trunk it the axon branch. Neurons found in our eyes. converts light into electrical signals for brain to interpret.
Psuedounipolar neuron
One major trunk that splits into two major trunks that extend peripherally and the other centrally. Peripheral branch acts like a dendrite and the central branch acts like an axon. These cells are found in the somatosensory system (allow use to feel touch on the hand, stretch of the muscle, position of a joint. cells of body sensory system).
Multipolar neuron
have many major dendritic trunks that extend away from the cell body. one axon trunk that extends away from cell body. cells found in our brain (thinking) and the cells of somatic motor system.
Interneuron
Multipolar in its construction. 4 major dendritic trunks and one major axon trunk. extremely tiny and positioned between the axon of one neuron and and the dendrite of another neuron. it delivers but can also modify the message to another big neuron.
Leak (non-gated) channel
Open all the time and ions and other formed elements can pass down their electrochemical gradient all the time. as long as they can fit they can go through.
Modality-gated channel
gate in the middle that is opened by any kind of physical modality (a mechanical touch or temperature).
Ligand-gated channel
(protein) neurotransmitter- a protein of the nervous system that when it attaches to membrane channel it opens the gate to allow ions and other formed elements to flow through the channel.
Voltage-gated channel
a change in the relative charge along the membrane can open the gate and allow ions and other formed elements to flow through. (action potential)
Resting potential
negative inside the cell and positive charge outside the cell.
Local potential
can be localized around one particular membrane channel. Small short distance change of polarity. starter signals. Have the capacity to spring the start of an action potential. depolarizing or hyperpolarizing.
Action potential
Long distance events along axons of the nerve cells. Long distance message of the nervous system. Depolarizing only
Sodium potassium pump
requires ATP, 3 sodiums (+) out for 2 potassiums (+) in. polarizes our nerve cells so they can send messages. Gets the cells ready to accept the action potential and resets the axon so it is ready for the next one.
Depolarization
reduce the polarity, make things less different. makes the cell less negative on the inside. more likely to create an action potential (excitatory).
Hyperpolarization
make the difference between the inside and the outside even greater than at rest. Less likely to create an action potential and send it so it is considered inhibitory. decreases chance of an action potential.
Local potential
two types-
Receptor potential- when a modality gated channel is opened and ions spill in.
Synaptic potential- where a neurotransmitter hooks up with a ligand gated channel and lets some ions flow. Change in polarity can be graded.
Temporal grading
one input repetitively depolarizes pieces of membrane. Repetitive touch (neurotransmitter)
Spatial grading
different inputs over a large surface area (multiple points of contact) and all change polarity. larger change in polarity. (neurotransmitter)
Passive propagation
ions enter the cell and passively spread out a very short distance
Trigger zone
place of sensation/modality or c
Active Propagation
spreads far enough that it creates a new action potential in another spot.
Refractory period
cannot create another action potential at the time. Voltage gated channels spill big in both directions but the voltage gated channels in refractory period ignore the ions so the message only moves in one direction (never goes backwards).
Propagation
to move from one spot to the next
Unmyelinated
slow paced
Myelinated
insulated (fast paced) jumps from one node to the next
Node of Ranvier
next spot that a bunch of voltage gates are located (that another action potential can be created at)
increase the pace of signal
the Bigger the neuron the faster the signal.
Thicker myelin- faster signal
Receptor zone (trigger zone)
the first place that touch (modality) is translated into an action potential. (pseudounipolar neurons)
Synaptic zone
where the synapse creates the action potential at the axon hillock. (multipolar neurons)
Motor pathway (corticospinal)
is efferent, it starts up and goes down and out
Sensory pathway (spinothalamic)
starts low and goes high, in and up is afferent (sensory)
Convergence
many signals to one neuron, and the neuron figures out what the majority message of the neurons is.
Divergence
from one neuron to many others. One brain cell could excite three different neuron cells
Glia
Non neuronal, cells that support neurons. To enhance signaling and provide direct support functions.
Help provide structure for neural cells.
May assist with transmission of information
May assist with regulation of extracellular fluid
Possible role in pathogenesis
Oligodendrocyte
Myelination of the CNS (one to many). help insulate and speed up action potentials. CNS (brain and spinal cord)
Schwann Cell
Myelination of cells in the PNS. Phagocytic function- swallows and digests injured neurons and recycles its parts during PNS injury.
Astrocyte
Biggest of the glial cells (found in the CNS) a star with many projections out from cell body. Really important in cell signaling (calcium important). Has a scavenger function- clean up function (takes away excess ligand). Part of the blood brain barrier inside the CNS (helps prevent big formed elements from leaving the brain). pathway for migrating neurons in development.
Microglia
hoover vacuums of the CNS (phagocytic function, swallowing irritating chemicals or biproducts of injury in the nervous system). takes out invaders. also swallows aging/dying neurons. Sometimes gets turned on inappropriately and swallows healthy cells (Alzheimer’s disease theory)
Neuroinflammation
good- calls microglia to injured area which helps clean up the area of injury and helps the tissue heal
Bad- lot of fluid that builds up and can cause harmful effect from squeezing the brain
Guillain- Barre
Peripheral demyelinating disease (Schwann cells)- removes insulation from axon, may injure or kill axons. after attack stops the PNS rebuilds itself
MS
auto-immune attack (oligodendrocytes) CNS. typically remyelination does not occur. remitting and relapsing in typical course. oligo cells get chewed up is the bad and then inflammation comes and goes and it gets better and then it goes through the same cycle.
Glial Tumor
Astrocytes growing out of control (squeezes neural tissue) most common location is the frontal lobe.
