ch 11.4- nervous system Flashcards
neuron
the most basic unit of the nervous
system. It has three parts: the soma (cell body),
dendrites (extensions that receive signals), and the
axon (sends signals out).
axon hillock
Area where the axon is connected
to the cell body. Responsible for the summation
of graded potentials.
myelin sheath
Fatty insulation of the axon that
speeds up action potential propagation by
stopping ion exchange. The myelin sheath is formed by
oligodendrocytes (in the central
nervous system) and
Schwann cells (in the
peripheral nervous system). Thicker myelinated neurons fire signals faster.
nodes of ranvier
Gaps between myelin sheaths
where ion exchange occurs. Propagation of the
action potential occurs here, jumping from gap to
gap (node to node) in a process called saltatory
conduction.
steps of action potential
- At resting potential, the membrane potential of
the neuron is around -70mV and is maintained by Na+/K+ ATPases, which pump three Na+ ions out and two K+
ions in, powered by hydrolysis of one ATP. K +leak channels are also present and help maintain resting potential through passive K+ leakage - When a stimulus causes threshold potential to
be reached (around -55mV in neurons),
voltage-gated Na+ channels open up, letting Na+ in, resulting in depolarization of the neuron. K+ channels are closed. - Next is repolarization of the neuron due to the opening of voltage-gated K+ channels, letting K+ out, and the closing of Na channels. This causes the membrane potential to become less positive
since positive ions are leaving. This is the absolute refractory period: no stimulus can cause an action potential. - When the membrane potential becomes even more negative than the normal resting potential, this is known as hyperpolarization. This results in a relative refractory period being established, during which another action potential can be fired, but it requires a much stronger stimulus.
- The membrane potential returns to normal resting potential through the pumping of Na+ /K+ATPases and K +leak channels.
absolute refractory period
refers to the period after the initiation of the action potential during which another action potential cannot be fired no matter how powerful the stimulus is. It is due to the inactivation of voltage-gated Na+ channels after they open.
the period of depolarization and repolarization
realative refractory period
refers to the period
after the action potential fires during which a stronger
than normal stimulus could cause another action
potential to be fired. (after repolarization)
steps of synaptic transmission
- Action potential reaches the end of the
presynaptic axon, causing voltage-gated
calcium channels to open and letting Ca2+
ions into the neuron. - The Ca2+ ions cause synaptic vesicles to fuse and undergo exocytosis, releasing neurotransmitters into the synapse.
- The neurotransmitters (described in the table on the next page) bind to ligand-gated ion channels on the postsynaptic neuron, producing graded potentials (depolarizations or hyperpolarizations
of the membrane). - These graded potentials summate at the axon hillock and an action potential will fire if the summation of graded potentials is higher than the threshold potential of neurons.
EPSP
An excitatory postsynaptic potential (EPSP) is a
graded potential that depolarizes the membrane.
IPSP
An inhibitory postsynaptic potential (IPSP) is a
graded potential that hyperpolarizes the membrane.
glutamate
Main ENT of the central nervous system
dopamine
Involved in reward motivated behavior
epinephrine
● Postsynaptic NT of the sympathetic nervous system
● Constricts blood vessels and dilates bronchioles
● Increases blood flow to skeletal muscles
● Decreases blood flow to smooth muscles
norepinepherine
Postsynaptic NT of the sympathetic nervous system
Aids epinephrine in the “fight or flight” response
acetylcholine
● Most common NT in the muscular system
● Released from presynaptic motor neurons to signal muscle fibers
● Signals muscle fibers by binding to ligand-gated sodium channels
GABA
Gamma-aminobutyric
acid (GABA)
● Main INT of the central nervous system
glycine
● INT of the central nervous system
seritonin
● INT of the brain
frontal lobe
Known for higher function
processes such as decision making, problem
solving, attention and concentration.
temporal lobe
Known for speech and hearing.
occipital lobe
vision
parietal lobe
Known for spatial perception and
sensation.
cerebellum
located underneath the occipital
lobe and is responsible for the coordination of
movement.
brainstem
midbrain
pons
medulla oblongata
reticular formation
midbrain
Relays senses to other parts of brain.
pons
Relays messages between the forebrain,
cerebellum, and medulla.
medulla oblongata
Heart and breathing rate,
blood pressure, toxin sensing. Connects the
cerebrum/cerebellum to the spinal cord.
reticular formation
Neurons throughout the
brainstem that are involved in cortical arousal,
and consciousness.
during embryonic development, the brain can be divided into what areas
forebrain
midbrain
hindbrain
forebrain of embryo
Telencephalon
Diencephalon
telencephalon
gives rise to the cerebellum
Diencephalon
gives rise to the Thalamus,
hypothalamus, and
pineal gland
midbrain of embryo
develops into the mesencephalon
mesencephalon
gives rise to the midbrain
hindbrain in embryo
develops into the metencephalon and myencephalon
metencephalon
gives rise to pons and cerebellum
myencephalon
gives rise to the medulla oblongata
what is the limbic system composed of
thalamus,
hypothalamus, hippocampus, and amygdala.
limbic system
It is
responsible for emotion, memory, learning, and
motivation.
thalamus
The “relay center” of the brain and is
located between the cerebrum and the midbrain.
Relays sensory and motor signals from the body to
the brain.
hypothalamus
Regulates hormone secretion in
the body.
hippocampus
Responsible for memory
consolidation.
amygdala
Responsible for the emotional reaction
to certain scents.
peripheral nervous system
The peripheral nervous system is divided into the
somatic nervous system (voluntary motor action and
sensory input) and the autonomic nervous system
(involuntary).
autonomic nervous system
The autonomic nervous system can be further
divided into the sympathetic nervous system (fight or
flight) and the parasympathetic nervous system (rest
and digest).
sympathetic NS
● Release of sugar into blood for energy.
● Increase in heart rate for oxygen delivery to the
brain and muscles.
● Vasodilation of skeletal blood vessels, and
vasoconstriction of the digestive system.
● Dilation of bronchi and bronchioles to allow more
oxygen into lungs.
● Dilation of the pupil to give the brain more visual
information.
parasympathetic NS
● Relaxation of muscles.
● Decrease in heart rate.
● Maintenance of homeostasis.
● Increase in gastrointestinal activity.
THROUGH THE VAGUS NERVE
ganglion
cluster of nerve bodies in
the peripheral nervous system. The autonomic
nervous system’s neurons are either preganglionic or
postganglionic. The preganglionic neuron comes
from the central nervous system and synapses with
the postganglionic neuron at the ganglion.
sympathetic NS preganglionic nerves
Acetylcholine
sympathetic NS postganglionic nerves
norepinephrine/ epinephrine
also stimulates the adrenal medulla to release NE/E into blood
parasympathetic NS preganglionic nerves
acetylcholine
parasympathetic NS postganglionic nerves
acetylcholine
acetylcholinesterase
is an enzyme that is
responsible for the breakdown of acetylcholine via
hydrolysis.
outer ear
takes in sound waves, and the
tympanic membrane transfers the sound from
outer ear to middle ear.
middle ear
composed of three bony
ossicles. The ossicles transfer vibrations through
the middle ear and amplify the signal. The
vibrations get transmitted from the middle to the
inner ear.
cochlea
uses fluid and hairs to convert the
mechanical signal into a neuronal signal, known as
transduction.
semicircular canal
has fluid and hairs just
like the cochlea but gives information about the
person’s movement. It is also the reason we get
dizzy.
cornea
Transparent; focuses light and protects
the eye.
iris
controls size of pupil
pupil
controls how much light enters the eye
lesn
focuses image on the retina
retina
Back of the eye that has photoreceptors
(rods + cones).
○ Rods function at low levels of light and are
responsible for low-light perception.
○ Cones function at high levels of light and are
responsible for color perception.
fovea
Highest concentration of photoreceptors in
the retina. Responsible for high acuity vision.
optic nerve
Bundle of axons that transmits visual
information to the brain.
optic disc
The blind spot of the eye, where the
optic nerve passes through to reach the brain.
sclera
Protective layer of tissue; the “white part”
of the eye.
