Nervous system Flashcards
Cell body/soma
contains the nucleus, E.R., and ribosomes
dendrites
receive incoming messages
axon hillock
integrates the incoming signals from other cells to determine if an action potential will be produced; if sum of signals is excitatory above a threshold, action potential produced
oligodendrocytes
produce myelin in the CNS
Schawann cells
produce myelin in the peripheral nervous system
Glial cells
have structural and supportive roles in the nervous system; 4 types: astrocytes, ependymal cells, microglia, oligodendrocytes/Schwann cells
astrocytes
nourish neurons, form blood-brain barrier, which controls the solutes that can enter into the brain
ependymal cells
line ventricles of the brain and produce cerebrospinal fluid, which supports the brain and absorbs shock
microglia
phagocytes that break down waste and pathogens in the CNS
Resting potential
about -70 mV, electric potential difference; selective permeability of ions (membrane more permeable to K ions, which diffuse out) and Na/K ATPase maintain negative resting potential
hyperpolarization
lowers membrane potential to make neuron less likely to fire
Summation
additive effect of multiple neurons acting on the same receiving neuron, combining excitatory signals to make it more likely to fire
temporal summation
multiple signals are integrated in relatively short period of time
spatial summation
effects based on the number and location of incoming signals
refractory period
as a result of hyperpolarization following an action potential
absolute refractory period
no amount of stimulation can cause another action potential to occur
relative refractory period
there must be greater than normal stimulation to cause an action potential, as a result of the increased negative voltage with hyperpolarization
impulse propagation
action potential travels down the axon by causing depolarization in each sequential segment of the axon, and then stimulates NT release from terminal buttons
Speed of action potential propagation down axon
increased length- higher resistance, slower conduction
greater cross section area- faster propagation, less resistance
Myelin increases speed
saltatory conduction
due to insulation of myelin, membrane only permeable to ions at nodes of Ranvier; signal hops from node to node
Effector
postsynaptic cell that is a gland or a muscle rather than a neuron
Release of NTs
stored in vesicles in nerve terminal; when action potential reaches terminal, Calcium channels open and Ca2+ flows into cell- triggers fusion of vesicle with membrane and exocytosis of NT
Reuptake carriers
bring NTs from synapse back into presynaptic neuron
white matter
consists of axons encased in myelin sheaths
grey matter
consists of unmyelinated cell bodies and dendrites
dorsal root ganglion
sensory neurons bring info in through the DRG to CNS
peripheral nervous system
includes all 31 pairs of spinal nerves and 10 pairs of the cranial nerves, consists of somatic and autonomic nervous systems
somatic nervous system
consists of sensory and motor neurons within the skin, joints, muscles
parasympathetic nervous system
role is to conserve energy, associated with resting; reduces heart rate, constricts bronchi; increases digestion by increasing peristalsis
somatic nervous system
increases heart rate, increases blood glucose, redistributes blood to muscles needed for movement, decreased digestion, decreased peristalsis, releases epinephrine, dilates pupils to let in more light
Reflexes
interneurons in spinal cord send out quick response in certain situations because it would take too much time to get a response from the brain
Monosynaptic reflex arc
single synapse between the sensory neuron that receives stimulus and motor neuron; ex. knee-jerk reflex
Polysynaptic reflex arc
at least one interneuron between sensory and motor neurons; ex. withdrawal reflex (stepping on a nail)
