neurons, action potentials Flashcards
examples of summation
spatial (EPSPs from several neurons)
temporal (several EPSPs from one neuron)
when do voltage gated Na channels close?
after hyperpolarization returns it to -70
medulla
basic vital functions: breathing, heart rate, certain reflexes
Here also the resperiatory centers are found
pons
responsible for facial movement, balance. It has many peduncles connecting brainstem to cerebellum
cerebellum
over half of all brain neurons, responsible for balance, movement (but not the initiation of movement, that would be motor cortex)
midbrain
motor regulation. Substantia nigra is here
limbic system
implicated in memory (loop of papez)
Amygdala > hippocampus > fornix > entorhinal cortex (your GPS) > cingulate cortex
diencephalon
Contains thalamus and hypothalamus
telencephalon
frontal lobe - motor control and higher thinking
parietal lobe - sensory
temporal lobe - auditory and olfactory, a bit of short term memory, language comprehension, and emotion
occipital lobe - visual information
Broca’s area - produce speech
Wernicke’s area - comprehend speech
basal nuclei
deep gray matter, also referred to as basal ganglia. These are responsible for initiating movement and many basic motions like walking
thalamus
sensory relay station for all senses except olfaction
hypothalamus
controls pituitary gland, involved in body homeostasis including temperature
white matter
bundles of myelinated axons
PNS neurons are often myelinated due to their length
gray matter
unmyelinated cell bodies and dendrites
There are deep brain nuclei (e.g. suprachiasmatic), the cortex, and in the PNS are ganglia of gray matter
frontal lobe
voluntary decisions, rational thought
also motor outputs
parietal lobe
sensory
temporal lobe
hearing, smell, memories
occipital
vision
amygdala
fear, emotional recognition
somatic neurons use which NT?
ACh only; nicotinic only
autonomic neurons use which NT
ACh at the ganglia; epi and norepi at the ends
absolute threshold
minimum stimulus required to trigger a receptor (e.g. nocicieptor), whereas the DIFFERENCE THRESHOLD is the minimum stimulus for us to notice the feeling
sensory adaptation
we ignore unchanging stimuli, but can be retriggered if stimulus changes
bottom up processing
sensory neurons > brain > identify information
top down processing
brainapplies prior knowledge and experience > forms holistic view of what’s happening
iris
colored part that regulates pupil diameter
lens
performs refraction
cornea
part of outermost keratin tunic of eye, continuous with lens
pupil
black opening in middle of eye
ciliary muscles
regulate lens curvature and thus near vs far focus
fovea centralis
area of greatest visual acuity. Actually has NO rods, only cones
retina
nervous layer of eye, has rods and cones
optic disc
your blind spot, where optic nerve and all blood vessels leave eye
when no light
rod cells are actually constantly sending APs, Na channels open, constantly depolarizing, constantly OFF bipolar cells are activated; ON inhibited
when there is light
Na channels are closed; no APs sent. This inhibits OFF bipolar yet stimulates ON bipolar
rods
more abundant than cones
of cones, red most abundant
Steps of action potential
- RMP is maintained by Na/K ATPase
- depolarization is caused by EPSP, after which voltage gated Na channels open, depolarize to 35mV
- Then, voltage gated Na shuts and voltage gated K channels open. Repolarize to -60mV (at which point they close)
- ATPase restores -70mV RMP
Voltage gated Na or K channels quicker?
Na channels close quickly; K more slowly
Glial cells
Schwann cells for PNS neurons
oligodendrocytes for CNS
astrocytes also in CNS - they guide neuron development and regulate NT levels
microglia - remove dead cells in CNS (immune function)
ependymal cells - produce CSF
**note, myelinated neurons require less energy from ATPase to repolarize
reciprocal inhibition
reflexes involving concurrent relaxation and flexion, such as the crossed extensor reflex
adrenal medulla
Its cortex secretes glucocorticoids, mineralocorticoids, some sex hormones
pacinian corpuscle
skin pressure sensor, type of mechanoceptor
auditory hair cells are also mechanoceptors
chemoreceptors
e.g. olfactory, gustatory, carotid bodies detect CO2
nociceptors
can be somatic or autonomic (the latter can cause referred pain)
electromagnetic receptors
rods and cones detect EM radiation; however other animals can detect electric/magnetic field
muscle spindle
type of proprioceptor. Other examples are golgi tendon organs, joint capsule receptors
auditory system
eardrum, malleus, incus, stapes, oval window, cochlea, vibration in endo and perilymph stimulates HAIR CELLS, these rub against tectorial membrane, causing ion channels to open, APs sent along auditory nerve.
high pitched sounds stimulate which part of cochlea?
the base, near oval window; whereas low sounds stimulate apex. Amplitude determines rate of AP firing, and in turn perception of volume
balance regulated by which part of ear?
we have three semicircular canals that are filled with endolymph and can also detect acceleration through similar hair cells
opsin
a protein, bound to 1 molecule of retinal that has one cis bond. When absorbing a photon, it is converted to the all-trans form. This eventually closes the Na channel and then there is a LACK of signals to the inhibitory bipolar neuron; an INCREASE of signals to the stimulatory one.
The NT for rods and cones is glutamate.
emmetropia
normal vision;
hyperopia - farsight. Focal length is too long and converges past the fovea centralis.
myopia - nearsight. The focal length is too short
Presbyopia - farsightedness due to lack of lens flexibility
feature detection theory
specific part of brain is activated when looking at different things
parallel processing
many parts of visual stimulus processed simultaneously
Gestalt theory
the whole is more than the sum of its parts; when we see a face, there is more than just seeing the shapes and colours.
signal detection theory
predicts how and when someone will detect a stimulus
hormone types
PEPTIDE
made in RER, stored in vesicles, cannot bypass cell membrane
STEROID
made in smooth ER, transported via protein in bloodstream, diffuses in and out of cells
absolute vs relative refractory period
absolute - when the Na channels are still open, NO AP WHATSOEVER can be initiated
relative - when in the hyperpolarization stage, technically a new AP can start, but stimulus required is greater
difference btw soma and axon hillock?
soma has lower density of voltage gated Na channels
sympathetic nervous system
dilates muscle blood vessels, however, it constricts blood flow to skin and digestive organs, enhanced FAR vision but not near
mydriasis
this is sympathetic dilation of pupil. The neurotransmitter involved is NE. For pupil constriction, it is ACh.
