Nervous System Flashcards
neurons
specialized cells capable of transmitting electrical impulses
soma
cell body of a neuron, where nucleus is located
dendrites
receive incoming messages from other cells
axon hillock
integrates the incoming signals from the dendrites, plays an important role in action potentials (transmission of electrical impulses down the axon)
axon
long appendage that terminates in close proximity to a target structure (muscle, gland, another neuron)
Axons carry it Away from the soma
What produces myelin in the CNS?
Oligodendrocytes
What produces myelin in the PNS?
Schwann cells
Breaks in myelin sheath are called?
nodes of Ranvier
At the end of the axon it is called the?
Nerve terminal/synaptic bouton (knob)
Neurotransmitters
chemicals that transmit information between neurons
Space between terminal portion of the axon and dendrites of the adjacent neuron
synaptic cleft
Nerve terminal, synaptic cleft, and postsynaptic membrane are known as the…?
Synapse
Types of nerves in the PNS
Sensory, motor, or mixed–> refers to the type of information they carry
Axons can be bundled together to form?
tracts
only carry one type of information
Cell bodies of neurons in the same tract are grouped together to form?
Nuclei
Glial cells/neuroglia
cells in the nervous system that play structural and supportive roles
ex. astrocytes, ependymal cells, microglia, oligodendrocytes (CNS) and Schwann cells (PNS)
Astrocytes
nourish neurons and form the blood brain barrier, which controls the transmission of solutes from the bloodstream into nervous tissue
Ependymal cells
line the ventricles of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as a shock absorber
Microglia
phagocytic cells that ingest and break down waste products and pathogens in the central nervous system
What is all or nothing?
An action potential!
What is a cell’s resting membrane potential?
-70 mV
Potassium (K+) and sodium (Na+) help maintain the resting potential
Potassium leak channels
allows the slow leak of potassium out of the cell
Sodium leak channels
Slow leak of sodium into the cell
Na+/K+ ATPase
continually pumps sodium and potassium back to where they started: potassium into the cell and sodium out of the cell
Depolarization
raises the membrane potential, caused by excitatory input
if it hits its threshold value, will trigger an action potential
Hyperpolarization
lowering the membrane potential from its resting potential
summation
additive effect of multiple signals
Temporal summation
multiple signals are integrated during a relatively short period of time
Spatial summation
the additive effects are based on the number and location of the incoming signals
How does action potential occur
it’s at -70 mV, there’s a Na+ influx that raises the membrane potential to about 35 mV, then there is a K+ efflux that lowers the membrane potential to back to -70 mV, with the Na+/K+ pump helping to re-stabilize from the hyperpolarization
Electrochemical gradient
promotes the migration of sodium into the cell
3 states of sodium channels?
- Closed-> before the cell reaches threshold and after inactivation has been reversed
- Open –> from threshold to about 35 mV
- Inactive –> from approximately +35 mV to the resting potential
absolute refractory period
no amount of stimulation can cause another action potential to occur
relative refractory period
there must be a greater than normal stimulation to cause an action potential to occur, bc the membrane is starting from a potential that is more negative than its resting value
Impulse propagation
Action potential travels down the axon and initiates neurotransmitter release
Saltatory conduction
the signal hoping from node to node
effector
if a neuron signals to a gland or muscle, rather than another neuron
acetylcholine
a neurotransmitter that is broken down by acetylcholinesterase; responsible for parasympathetic response in the body
(we don’t want constant signaling to a postsynaptic cleft)
reuptake carriers
a way in which neurotransmitters can be brought back into the presynaptic neuron
ex. serotonin, dopamine, and norepinephrine can all go back this way
Nitric oxide
a signaling molecule that diffuses out of the synaptic cleft
supraspinal circuit
when input from the brain or brainstem is needed to process a stimuli
grey matter
consists of unmyelinated cell bodies and dendrites
Sections of the spinal cord?
Cervical, thoracic, lumbar, sacral
It is protected by the vertebral column, transmits nerves at the space between the adjacent vertebrae
Dorsal root ganglia
cell bodies of sensory neurons are found in the dorsal root ganglia
somatic nervous system
consists of sensory and motor neurons distributed throughout the skin, joints, and muscles. Sensory neurons transmit information through afferent fibers
autonomic nervous system
regulates heartbeat, respiration, digestion, and glandular secretions
first neuron in the autonomic nervous system is called the…?
preganglionic neuron
second neuron in the autonomic nervous system is called the…?
postganglionic neuron
parasympathetic nervous system
conserves energy, rest and digest
constricts pupils, stimulates flow of saliva, constricts bronchi, slows heartbeat, stimulates peristalsis and secretion, stimulates bile release, contracts bladder
functions of the sympathetic nervous system
fight or flight
dilates pupils, inhibits salivation, relaxes bronchi, accelerates heartbeat, stimulates sweating or piloerection, inhibits peristalsis and secretion, stimulates glucose production and release, secretion of adrenaline and noradrenaline, inhibits bladder contraction, stimulates orgasm
monosynaptic reflex arc
there is a single synapse between the sensory neuron that receives the stimulus and the motor neuron that responds to it
ex. knee-jerk reflex
polysynaptic reflex arc
there is at least one interneuron between the sensory and motor neurons
ex. withdrawal reflex (step on a nail), interneurons in the spinal cord provide the connections from incoming sensory information to the motor neurons in the supporting limb
