Ch. 4: The Nervous System Flashcards
What is the cell body?
nucleus of a neuron that also has the endoplasmic reticulum and ribosomes
also called the soma
What is the role of dendrites?
recieve incoming messages from other cells
What is the role of the axon hillock?
integrates incoming signals and wil initiate an action potential if the threshold is met
What is the role of myelin and the myelin sheath?
fatty membrane that prevents signal loss or crossing signals
increases the speed of conduction in the axon
What are oligodendrocytes?
produce myelin in the CNS
What are Schwann cells?
produce myelin in the PNS
What are the nodes of Ranvier?
small breaks in the myelin sheath with exposed areas of the axon
What are glial cells?
structural and supportive roles
type of glial cell
What are astrocytes?
noursh neurons and form blood-brain barrier
control what enters nervous tissue from blood
What are ependymal cells?
line ventricles of the brain and produce cerebrospinal fluid
What are microglia?
phagocytic cells that ingest and break down waste products and pathogens in CNS
Explain the steps of an action potential.
- resting potential -70 mV (more K+ than Na+ which makes it negative)
- depolarization, sodium gates open and sodium enters the cell
- when the cell reaches +35 mV the sodium channel closes
- repolarization, triggers potassium channels to open and let potassium out of the cell
- hyperpolarization, overshoot of K+ out of the cell
- refactory period, when no action potential can occur
absolute refactory period: no amount of stimulation can cause another action potential
relative action potential: must be greater than normal stimulation to cause an action potential
action potential moves down axon to trigger NT release
What causes an action potential to be faster?
shorter length of axon has lower resisitance and faster conduction
greater cross-sectional areas have less resistance and faster propogation (much larger effect on speed)
What is saltatory conduction?
signal hopes from the nodes of Ranvier
myelin prevents ions to travel through so the membrane is only permeable to ion flow at the nodes of ranvier
What is white and grey matter?
in the brain and spinal cord
white matter has axons with myelin sheaths
grey matter has unmyelinated cell bodies and dendrites
- in the brain the white matter is deeper than gery matter
- in the spinal cord white matter is outside the cord and grey matter is deep within
Explain the connection between the spinal cord, sensory, and motor neurons.
sensory neurons bring information to the back of the spinal cord (cell bodies of sensory neurons are in dorsal root ganglia) and motor neurons exit the spinal cord at the front of the spinal cord
What is a monosynaptic reflex arc?
single synapse between sensory neuron that recieves the stimulus and the motor neuron that responds to it
knee-jerk reflex
What is a polysynaptic reflex arc?
there is at least one interneuron between the snesory and motor neurons
withdrawl reflex
Explain what happens at the nerve terminal and the synapse.
- action potential reaches nerve terminal
- calcium channels open
- calcium influx causes versicles with NTs to the presynaptic membrane
- exocytosis of NTs into synaptic cleft
- NTs bind to receptors on postsynaptic fell (ligand-gated ion channes or G protein-coupled recpetors)
How are Neurotransmitters cleared from the postsynaptic receptors?
- enzymatically broken down
- absorbed back into presynaptic cell by reuptake chanels
- diffuse out of the synaptic cleft
