Parts of the Brain & Cranial Nerves, Action Potentials Flashcards
pons
- loc middle portion of brainstem (bridge)
- ascending and descending nerve tracts
- sleep centre: REM sleep
- respiratory centre
ant portion of pons
pontine nuclei - communication b/w cerebrum and cerebellum
- neurons synapse here
post portion of pons
nuclei of cranial nerves V, VI, VII, VIII
midbrain
- most superior portion of brainstem
- nuclei of cranial nerves III, IV
- cerebral aqueduct runs through midbrain
Tectum
tectum
- 4 nuclei that form mounds on dorsal surface of midbrain
2 superior colliculi: visual reflexes (scanning, dilating pupils)
2 inferior colliculi: auditory reflexes
reticular formation
cloud of nuclei
controls sleep wake cycle : maintaining consciousness, waking up
** not exactly a structure but scattered throughout brainstem
cerebellum
contains 10% of the brain’s mass, 50% of neurons in the brain found here
- communication w other regions of CNS
cerebral peduncle
cerebral peduncle
connects cerebellum to brainstem -
superior cerebellar peduncle: midbrain
medial cerebellar peduncle: pons
inferior cerebellar peduncle: medulla oblongata
3 regions of cerebellum
- flocculonodular lobe
- vermis
- cerebellar hemisphere
flocculonodular lobe
balance
takes info from env’t and puts it together
vermis
anterior - gross motor coord. ie walking
posterior - fine motor coord. ie hand dexterity
cerebellar hemisphere
fine motor coord
takes sensory info and puts it all together
diencephalon
- loc b/w brainstem and cerebrum 3 components: thalamus hypothalamus epithalamus
thalamus
largest part of diencephalon
sensory relay station
receives sensory info and projects to cerebral cortex (all maj. senses but smell)
interthalamic adhesion
connects lateral portions of thalamus
surrounded by 3rd vent
medial geniculate nucleus
auditory impulses
lateral geniculate nucleus
visual impulses
hypothalamus
most inferior portion of diencephalon
mood & emotion portions closely related bc parts of brain that control them are so close together
-more than 12 clusters of nuclei re: homeostatic functions
infundibulum
stalk connecting hypothalamus to pituitary gland
- connects nervous to endocrine system
- composed of white matter
epithalamus
loc post & superior to thalamus
- contains habanula : nuclei concerning with emotional & visceral response to odor
(smell from env’t and response)
- pineal gland
pineal gland
pea sized
secretes melatonin
may influence onset of puberty (biological clock)
cerebrum
higher order thinking
cerebral cortex
outer layer of brain: gray matter
4 (5) lobes:
temporal, occipital, parietal, frontal, insula
gyrus
hill
sulcus
valley
fissure
deeper groove
precentral gyrus
loc ant to central sulcus
primary motor cortex, response in body
postcentral gyrus
loc post to central sulcus
primary somatic cortex
frontal lobe
- loc anterior, superior
motor function
agression
mood
parietal lobe
-loc posterior, superior
touch, pressure, taste
blood pH
most sensory info but not hearing, smell or vision
occipital lobe
- loc posterior, inferior
visual input, light info
temporal lobe
- loc anterior, inferior
olfactory
auditory
memory
insula
- loc in middle? of brain
homeostasis
self awareness
emotion
central sulcus
separates frontal & parietal lobes
pareito-occipial sulcus
exactly what it sounds like
transverse fissure
separates cerebellum & occipital lobe
lateral cerebral sulcus
separates frontal and temporal lobes
cerebral white matter
coordinates
nerve tracts connect the cortex to other parts of the cortex or CNS
3 types of tracts:
association, commissural, projection
association tracts
connects areas of cerebral cortex w/in same hemisphere
commissural tracts
connects areas of cerebral hemispheres
– corpus callosum connects L & R hemispheres of brain
projection tracts
b/w cerebrum and other parts of brains and spinal cord
– ex. internal capsule
tell me about cranial nerves
- part of the PNS
- 12
- arise from brain (not XI)
cranial nerve name mnemonic
now name the nerves themselves
oh once one takes the anatomy final very good vacations are heavenly
– olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal
cranial nerve function mnemonic
some say marry money but my brother says big brains matter more
Olfactory nerve
I sensory
origin in cerebrum
smell
2 neuron system: receptors in nose carry signal to olfactory bulb > olfactory tract > temporal lobe
Optic nerve
II sensory
origin in diencephalon
vision; collects info from retina, 2 nerves join at optic chiasm > optic tract > occipital lobe
Oculomotor nerve
III motor
somatic: movements of eyeball
parasympathetic: smooth muscle pupil constriction
Trochlear nerve
IV motor
moves a single muscle in the eye
Trigeminal nerve
V sensory & motor
3 branches:
ophthalamic - sensory: upper facial structures
maxillary - sensory: middle facial structures
mandibular - sensory: lower facial structures & ant to ear
- motor: mastication
Abducens nerve
VI motor
- movement of eyeball
Facial nerve
VII sensory & motor
sensory: taste (ant 2/3 of tongue)
motor: facial expression
parasympathetic motor: salivary & lacrimal glands
Vestibulocochlear nerve
VIII sensory has roots in brainstem and MO 2 nerves coming together: vestibular- balance cochlear- hearing
Glossopharyngeal nerve
IX sensory & motor
sensory: taste (post 1/3 tongue), monitors swallowing muscles, BP & blood gases
motor: swallowing
parasympathetic motor: parotid (saliva) glands
Vagus nerve
X sensory & motor
sensory: BP & blood gases, taste
motor: voice
parasympathetic motor: GI control, respiration, lower HR
Accessory nerve
IX motor
– has roots in spinal cord and in MO
head movements
dissipates function of vagus nerve, hence accessory
Hypoglossal nerve
XII motor
speech
swallowing
electrical properties of neurons result from
ionic conc differences across plasma membrane
permeability of membrane
membrane potential is
separation of charge aka potential difference
separation of opp charges, opp charges attract
ion concentrations at resting membrane potential
extracellular: greater conc. of Cl- , Na+ , Ca2+
cytosol: greater conc. of K+ , Proteins (Pr-)
what processes cause resting membrane potential?
- sodium/potassium pump
- membrane permeability
what is the sodium/potassium pump?
type of ATPase - breaks down ATP
an active transport protein
– needs energy bc is moving ions against their concentration gradients
how does the sodium/potassium pump work?
- ATP binds to pump and is broken down into ADP and Pi
- pump activated and 3 Na+ leave cell while 2 K+ enter cell
- ADP and Pi dissociate and pump stops
Types of ion channels
Leak (nongated) : mostly open -- responsible for resting membrane potential Gated: ion channels open/close on demand - ligand-gated - mechanically-gated - voltage-gated
What factors affect membrane permeability?
# of open channels size of ions # of gated channels
Leak channels
and where located
alternate b/w open/close at random
- K+ more numerous than Na+ channels
- conc. gradient dictates movement more that electrical gradient (charges of ions)
loc: (everywhere) cell body, dendrites, axons
Ligand-gated channels
where located?
- respond chemical stimulus where ligand bonds to receptor
loc: dendrites, cell body of neuron, target tissues
mechanically-gated channels
where located?
- respond to mechanical vibration/ pressure stimulus
loc: inner ear, touch receptors
voltage-gated channels
where located?
- respond to changes in membrane potential
domino effect - when one opens, triggers the rest to open
loc: ONLY in axon regions
how is resting membrane potential established?
- when movement of K+ out of cell = movement of K+ into cell
ie K+ diffuse out of cell w conc gradient but move back into cell w electrical gradient (Pr-)
also, Na+ moves w conc grad into cell and sodium potassium pump moves 3 Na+ out and 2 K+ in
polarization
the diff b/w inside and outside of cell membrane
aka resting membrane potential
how to create electrical signal? (broad)
need to change membrane potential
done w gated ion channels bc they can be controlled by a stimulus
whats the difference b/w action potentials and graded potentials
action: longer distance, uses voltage gated ion channels only
graded: localized, use mechanically and ligand gated channels
when does a graded potential occur?
- occurs in response to ANY change from resting membrane potential
hyperpolarization general
moving farther from zero,
getting more negative
depolarization general
moving closer to zero ie more positive
stimulus strength of GP
“graded”,
the larger the stimulus, the greater the amplitude of the GP, caused by more open gates
summation of GP
GPs can be added together to become larger in amplitude when signals are sent fast in temporal sequence
ie. having a bunch sent at really quickly OR sending many signals at the same time to diff dendrites
what are the stages of generating an action potential?
threshold
depolarization
repolarization
after-hyperpolarization
threshold
amt of charge needed for voltage gated channel to open
- must be depolarization to reach this
- can come from a large enough graded potential
from resting membrane pot. (AP)
Na+ voltage gated channel:
- activation gate closed
- inactivation gate open
K+ voltage gated channel: closed
depolarization phase (AP)
graded potential reaches threshold and:
- K+ stays closed
- Na+ activation opens (inactivation already open) and Na+ rushes into cell
repolarization phase (AP)
moving back towards resting membrane pot. :
- Na+ inactivation gate closes
- K+ gate opens and + charge leaves cell
THEN Na+ activation gate closes and inactivation gate opens (back to resting conditions)
after-hyperpolarizing phase (AP)
occurs if enough K+ leaves cell, it will become extra -ve (-90mV)
SO K+ channels close and leak channels , Na+/K+ pump works to bring resting membrane pot back to -70mV
Refractory period
the time in which an AP cannot be generated
absolute refractory period
an AP really cannot be generated here, Na+ inactivation gates must return to resting state
relative refractory period
K+ channels open buy Na+ close
- a suprathreshold stimulus is req’d to start AP (at this point we’re still at -90mV)
AP stimulus strength
- once a threshold is reached, AP size is the same
- more frequent APs are interpreted as greater amplitude
- -this is influenced by refractory period
why is the circle of willis an important structure?
anastomosis: redundancy in blood vessels that will still allow blood supply to the brain is part is blocked
latency phase
time from when stimulus is applied to when muscle begins contraction
