DAT bio Chapter 11.4 Nervous system Flashcards
Structure of neuron
has three parts: the soma (cell body),
dendrites (extensions that receive signals), and
the axon (sends signals out).
What is the axon hill lock?
Place where the axon connects to the cell body.
Responsible for the
summation of graded potentials.
What is myelin sheath?
fatty insulation of the axon
that speeds up action potential propagation by
stopping ion exchange.
In the CNS myelin sheath is formed by
oligodendrocytes
In the PNC myelin sheath is formed by
schwann cells
What are the 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 an action potential
1)
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.
Steps of an action potential
2)
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 (reaches a peak of around +30mV to
+40mV).
Steps of an action potential
3)
Next is repolarization of the neuron due to
the opening of voltage-gated K+ channels,
letting K+ out. This causes the membrane
potential to become less positive since positive
ions are leaving.
Steps of an action potential
4)
When the membrane potential becomes even
more negative than the normal resting
potential, this is known as hyperpolarization.
This results in a refractory period being
established, during which another action
potential cannot be fired because the
membrane potential is very negative.
Steps of an action potential
5)
The membrane potential returns to normal
resting potential through the pumping of
Na+/K+ ATPases and K+
leak channels.
What is the 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.
What is The relative refractory period?
period after the action potential fires during which
a stronger than normal stimulus could cause
another action potential to be fired.
What is the synapese?
space between two neurons
who sends the signal the presynaptic or postynaptic
presynaptic
Steps of synaptic transmission step 1
Action potential reaches the end of the
presynaptic axon, causing voltage gated
calcium channels to open and letting Ca2+
ions into the neuron.
Steps of synaptic transmission step 2
The Ca2+ ions cause synaptic vesicles to fuse
and undergo exocytosis, releasing
neurotransmitters into the synapse.
Steps of synaptic transmission step 3`
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).
Steps of synaptic transmission step 4
These graded potentials summate at the axon
hillock and an action will fire if the summation
of graded potentials is higher than the
threshold potential of neurons.
What is excitatory postsynaptic potential (EPSP)
graded potential that depolarizes the membrane.
What does excited neurotransmitter cause in EPSP
cause Na+
ion gates to open and let Na+
ions flow into the cell.
What is inhibitory postsynaptic potential (IPSP)
graded potential that hyperpolarizes the
membrane.
What does excited neurotransmitter cause in IPSP
Inhibitory neurotransmitters cause K+ ion gates to open and let K+ ions flow out of the cell. Another IPSP type allows influx of Cl-, allowing negative Cl- ions in.
What are non neuronal cells in the nervous system that help support and surround neurons?
glial cells
Glial cells are divided into
microglial cells and macroglial cells
Microglial cells are _______that protect the ______
macrophages
CNS
Microglial cells have many subtypes
astrocytes schwann cells oligondendrocytes satellite cells ependymal cells
Astrocytes
the most abundant glial cell
and form the blood-brain barrier. They also
help recycle neurotransmitters and provide
blood supply to the CNS neurons.
Schwann cells
form the myelin sheath in the
peripheral nervous system (PNS).
Oligodendrocytes
form the myelin sheath in
the central nervous system (CNS).
Satellilte cells
same functions as
astrocytes but instead help PNS neurons.
Ependymal cells
produce cerebrospinal fluid
(CSF), which cushions the CNS.
CNS is composed of
brain and spinal cord
PNS is composed of
nerves branching off the CNS
In embryonic development we consider ____ ____ ____ in the CNS
forebrain
midbrain
hindbrain
Forebrain develops into two things
telencephalon
diencephalon
Telencelphalon gives rise to
cerebrum
diencephalon gives rise to
thalamus
hypothalamus
pineal gland
mid brain develops into
mesencephalon
mesencephalon gives rise to
midbrain
hind brain develops into
metencephalon
myelencephalon
metencephalon gives rise to
pons, cerebellum
myelencephalon gives rise to
medulla oblongata
the developed brain cortex is divided into what four lobes?
frontal lobes
temporal lobes
occipital lobe
parietal lobe
frontal lobe function
higher function decision making, problem solving
attention
memories and emotions
temporal lobe functions
speech/language
hearing
occipital lobe functoin
vision
parietal lobe
visual perception (PAT pattern folding) touch/pain/ temp sensation
Where is the cerebellum located?
underneath the occipital lobe and is responsible for the coordination of movement
The autonomic nervous system is divided into what two things
sympathetic and parasympathetic nervous system
Sympathetic nervous system is _____
fight or flight
Parasympathetic nervous system is _____
rest and digest
Sympathetic nervous sytem effects are
Release of sugar into blood for energy.
● Increase in heart rate for oxygen delivery to
brain and muscles.
● Dilation of bronchi and bronchioles to allow
more oxygen into lungs.
● Dilation of the pupil to give the brain more
visual information.
Parasympathetic nervous system effects
Relaxation of muscles.
● Decrease in heart rate.
● Maintenance of homeostasis.
● Increase in gastrointestinal activity.
what is a ganglion
cluster of nerve bodies
in the peripheral nervous system.
The autonomic
nervous system’s neurons are either
____ or _____
preganglionic or postganglionic
the preganglionic neurons comes from where?
the central
nervous system and synapses with the
postganglionic neuron at the ganglion.
Sympathetic nervous system contains
short
preganglionic nerves and long postganglionic
nerves
Parasympathetic nervous system
long
preganglionic nerves and short postganglionic
nerves
Sympathetic nervous system → uses what
acetylcholine (Ach) for preganglionic nerves and
norepinephrine (NE)/epinephrine (E) for
postganglionic nerves. The sympathetic nervous
system also can stimulate the adrenal medulla to
release NE/E into the blood.
Parasympathetic nervous system → uses
acetylcholine (Ach) for both preganglionic and
postganglionic nerves.
What takes in sound waves
outer eat
what transfer the sound from outer ear to middle ear?
tympanic membrane
Where is the malleus, incus, and stapes located?
middle ear
The middle ear is composed of three bony ossicles. name them
malleus
incus
stapes
The ossicles transfer _____ through the ear and ____ the ____
vibrations
middle ear
amplify the signal
The stapes transfers the vibrations from the middle ear to the inner ear using what
oval window
What does the cochlea use to convert mechanical signal into a neuronal signal known as transduction?
uses fluid and hair
What is the round window?
membrane covered
opening between the middle ear and the inner
ear, similar to the oval window. It helps the
fluid expand and vibrate.
The semicircular canal contains what
fluid and hairs.
gives info about persons movement (reason why we get dizzy)
Cornea
transparent; focuses light and
protects the eye.
iris
controls the size of the pupil
lens
focuses images on retina
retina
back of the eye that has photoreceptors (cones and rods)
fovea
highest concentration of
photoreceptors in the retina and responsible
for high acuity vision.
Amacrine and bipolar cells do what
take info from rods and cones and transmit that info to ganglion cells of the optic nerve fiber
optic nerve
bundle of axons that transmits visual info to the brain
optic disk
blind spot of the eye, where the optic nerve passes through to reach the brain
Sclera
protective connective tissue that surrounds the eye, the white part of the eye
Choroid
vascular connective tissue
The tongue has how many taste receptor cells
5
Taste info is sent where
thalamus and subsequently the gustatory cortex
Nose contains what
olfactory receptor cells
What does the olfactory receptor cells sense
molecules and send signals to the olfactory cortex which gives us the perception of smell. These signals also integrate in the thalamus
and orbitofrontal cortex for smell sensation.
