Neurophysiology Flashcards
what is a difference in the major organelles of axons vs dendrites
dendrites and axons both have cytoskeleton and mitochondria; only axons have additional neurofilaments and microtubules
what are the functional classifications of neurons (3)
sensory, interneuron, motor
what are the structural classifications of neurons (3)
unipolar, bipolar, multipolar
examples of bipolar neurons
some special sense neurons
examples of unipolar neurons
sensory neurons
examples of multipolar neurons
motor neurons and CNS neurons
examples of sensory receptors
pacinian corpuscles, meissner’s corpuscles, golgi tendon organs, photoreceptors, taste and smell receptors
what is a synapse
a point of contact between neurons and target cells (other neurons, glands, muscles)
chemical synapses release
neurotransmitters
what are the four types of glia
microglia, Schwann cells, oligodendrocytes, astrocytes
there are ____x as many glial cells than neurons
10x (1 trillion vs 100 billion)
oligodendrocytes
myelinate axons in the CNS
schwann cells
myelinate axons in the PNS; protect unmyelinated axons in PNS
myelin is a _______ rich, ______________ compound
lipid rich, lipid/protein compound
nodes are _______ whereas internodes are _________
non-myelinated; myelinated
what is the process by which APs jump along a myelinated axon
saltatory conduction
_____________ wrap multiple axons in the _______
oligodendrocytes; CNS
_______________ wrap only one axon in the _________
Schwann cells; PNS
what are the functions of astrocytes (4-5)
structural support; regulate [K+]; reabsorb GABA/glutamate; vascular functions (constrict blood vessels; BBB)
what molecules cannot pass the BBB easily
large molecules, highly charged molecules, poorly lipid-soluble particles (also pathogens and many drugs limited from entry)
what are microglia
innate immune cells in the CNS
astrocytes are found in the
CNS
what is unique about microglia as opposed to other tissue macrophages
they can divide in situ to increase numbers when responding to an infection
what can diffuse through the lipid bilayer via passive transport, specifically by simple diffusion
small, uncharged molecules
how do small, charged molecules move through the lipid bilayer
passive transport via ion channel proteins; specifically called facilitated diffusion
what glial cells are present in the CNS
oligodendrocytes, microglia, astrocytes
what glial cells are present in the PNS
Schwann cells
describe features of ion channels (movement; ion types)
down concentration gradient; usually only 1 ion type; can be leaky or gated
what are two examples of voltage gated ion channels
Na receptor and K receptor
what is an example of a ligand gated ion channel
acetylcholine receptor (a ligand-gated Ca channel)
what is an example of a mechanically gated channel
stretch receptor in sensory neurons
how is touch/pressure converted into an electrical signal
via mechanically gated channels
what moves ions up their concentration gradient, consuming energy in the process? give an example
primary active transport; Na/K ATPase
symporters and antiporters are examples of
secondary active transport
what establishes the electrochemical gradient in cells
Na/K active transport
what is the only ion that directly influences the charge of neurons
K; because it can move across passively
the flux of K is determined by (2), which creates an electrochemical balance/gradient
concentration gradient and the electrical potential
what is the importance of the Nernst equation
allows you to calculate:
1) the membrane charge if you know the concentration of permeable ions
2) the concentration of ions if you know the membrane charge
what happens to K movement if the cell becomes less negative
K moves out; cells becomes more negative
what happens to K if the cell becomes more negative
K moves in; cells becomes less negative
what moves to restore the RMP in neurons when the charge changes
K
what determines the RMP in skeletal muscle
Cl
______ defines the RMP in neurons, whereas _______ defines the AP
K; Na (channels)
threshold value for depolarization in neurons
-55 mV
RMP in neurons
-90 mV
what is a local change in the RMP called
graded potential
what is the highest the membrane potential becomes during an AP
+45 mV
Na channels inactivate _____after they open due to _________
1 millisecond; closing of the inactivation gate
what ensures that the AP travels only in one direction
the refractory period
what are the four major neurotransmitter families
amines, acetylcholine, amino acids, neuropeptides
GABA is what family
amino acids
the nicotinic ach receptor is a _____ receptor, and is also called ________tropic
ligand-gated ion channel; ionotropic
the muscarinic receptor is a _____ receptor; and is also called _______tropic
GPCR; metabotropic
in what type of synaptic channel/receptor do ions bind directly
ionotropic; ligand-gated ion channel
in what type of synaptic channel/receptor to ions bind indirectly
metabotropic; GPCR
what ion channels cause EPSPs
Na or Ca
what ion channels cause IPSPs
K or Cl
what are 3 fates of NTs after synaptic transmission occurs
Ach broken into acetic acid and choline via acetylcholinesterase (choline taken up by pre-synaptic neuron and reused); amines are taken up by the pre-synaptic neuron and reused or broken down; GABA and glutamine diffuse away from the synapse to be metabolized by astrocytes
what vertebrae are not separated by intervertebral discs
atlantooccipital joint, atlantoaxial joint; sacral and coccygeal
the most blood vessels are present in which layer of meninges
pia
what is contained in the subdural space
serous fluid
what is contained in the subarachnoid space
CSF
what happens at vertebral segment C7
spinal nerve C8 comes out caudal to C7; then spinal nerve T1 comes out caudal to T1
where is the end of the spinal cord
L4-L6
cervicothoracic enlargement comprises spinal nerves
C6-T2
lumbosacral enlargement comprises spinal nerves
L4-S2
where is the lateral gray matter horn present
thoracic and first few lumbar/sacral segments
describe what tracts are within the dorsal, lateral and ventral columns of the white matter in the spinal cord
dorsal: sensory
lateral: sensory and motor
ventral: sensory and motor
describe what neurons are within the dorsal, lateral and ventral horn of the gray matter in the spinal cord
dorsal: sensory
lateral: autonomic
ventral: motor
what does it mean for tracts to be organized somatotopically
relationship between where the tract is and the kind of information in relays
T/F all tracts are paired
T
somatic reflexes start and end in the _____ but the synapse(s) are in the _________
CNS; PNS
T/F an interneuron is always present in a spinal reflex
F; it is not present in monosynaptic reflexes
somatic reflexes act on ____________ whereas autonomic reflexes act on ___________
skeletal muscle; smooth muscle
what are the three types of reflex arcs
monosynaptic ipsilateral
multisynaptic ipsilateral
multisynaptic contralateral
the myotatic reflex is
monosynaptic ipsilateral
another name for the knee jerk reflex
myotatic
the flexor reflex is
multisynaptic ipsilateral
another name for the withdrawal reflex
flexor reflex
the crossed-extensor reflex is
multisynaptic contralateral
spinothalamic tract
pain and temp sensation to thalamus
what is the order in which tracts are likely to be damaged (from most to least likely)
proprioceptive -> motor -> pain
what ascending tract does not decussate
spinocerebellar
what descending tract does not decussate
vestibulospinal
UMN are located
entirely in the CNS
LMN are located
in both the CNS and PNS
what is the conscious proprioceptive pathway
dorsal column
what is the unconscious proprioceptive pathway
spinocerebellar
what is the main motor pathway in domestic animals
rubrospinal
a dog is presenting with bilateral signs, indicating the lesion is likely
in the spinal cord
a dog is presenting with unilateral signs, indicating the lesion is likely
in the peripheral nerve
flaccid paresis/paralysis and neurogenic atrophy develops with
LMN damage
spastic paresis/paralysis and disuse atrophy develops with
UMN damage
doliocephalic
long and narrow skill; ex. greyhound
brachycephalic
short nasal compartment with altered sinuses; ex. pug
what causes cortical blindness
thiamine deficiency; necrosis of the occipital region
where is most CSF absorbed (I.e. where is the highest abundance of arachnoid granulations)
in the tentorum cerebelli and falx cerebri
the thalamocortex is comprised of the
cerebral cortex, thalamus, hypothalamus
the brainstem is comprised of the
midbrain, pons, medulla
the cortex consists of the
cerebral cortex, basal ganglia (nuclei), rhinencephalon (olfactory and limbic system)
frontal lobe
sensory, behaviour, voluntary movement, learning
parietal lobe
sensory and association
temporal lobe
audition, equilibrium, association
occipital lobe
visual cortex, association
piriform/olfactory lobe
olfaction, learning, memory, emotion (related to olfactory stimuli)
what are the three connections (fibres) mediated by white matter in the cortex
association fibres (connect neurons in same hemisphere); projection fibres (connect cortex to brainstem); commissural fibres (connect two hemispheres)
what are the two portions of the rhinencephalon
olfactory and limbic
how is the limbic system connected to the cortex
cingulate gyrus
where is the limbic system connected
cortex, thalamus and hypothalamus
what are the components of the basal nuclei
caudate nucleus, putamen, globus pallidus, (also claustrum)
what is the function of the basal nuclei
modulates voluntary motor signals from the cortex
what are the two nuclei of the thalamus
lateral and medial geniculate nuclei (note: red nucleus also originates in the thalamus)
lateral geniculate nuclei is responsible for _______ whereas the medial geniculate nuclei is responsible for ______
vision; audition
job of the thalamus
gets all sensory information (except olfaction) and projects it to the correct region of the cortex
signs of a thalamocortex lesion
circling, seizures, behavioural changes, cortical blindness, motor problems
what regulates the nervous and endocrine system
hypothalamus
what does the hypothalamus directly secrete into the neurohypophysis
oxytocin and vasopressin
what is the job of the midbrain
reflex movement of head in response to light and sound; contraction of iris muscle; movement of the eye; gait
when you think of pons, you think of
micturition
roles of pons
micturition control, respiration control, gives rise to trigeminal nerve; communication with cerebellum
medulla oblongata contains nuclei of cranial nerves
VI-XII
medulla oblongata is home to the
ascending RAS
roles of medulla oblongata
relays sensory info from the spinal cord and motor info from the cortex and brainstem; also involved in cardiovascular and respiratory control and is home to the RAS
cranial nerves in the thalamocortex
I, II
cranial nerves in the brainstem
III-XII
midbrain, pons and medulla are connected through the
reticular formation
job of the reticular formation
relays sensory information from entire nervous system to the thalamus, which then takes it to the cortex; involved in awakening
what is a key way to distinguish a thalamocortex lesion from a brainstem lesion
with thalamocortex will see seizures; with brainstem will NEVER see seizures but will see changes in level of arousal (depressed, obtunded, stuporous or comatose)
reflex processes (vomiting, regurgitation, sneezing) are due to the
reticular formation
the carotid sinus is innervated by CN _ whereas the aortic arch is innervated by CN _
IX (glossopharyngeal); X (vagus)
job of cerebellum
receives info about intended movement from the cortex and actual movement from the spinal cord; it then sends corrections to the cortex
is ataxia a sensory or motor sign
SENSORY
cranial nerves are considered part of the (CNS/PNS)
PNS
anosmia
no sense of smell
hypoosmia
decreased sense of smell
T/F there is 100% crossover of axons at the optic chiasm
F
if oculomotor nerve is damaged, what type of strabismus results
ventrolateral
if trochlear nerve is damaged, what are the clinical signs
dorsolateral strabismus, rotation of the fundus
if abducens nerve is damaged, what type of strabismus results
medial strabismus (also inability to retract the globe)
what are clinical signs of CNVIII damage
abnormal nystagmus, vestibular ataxia, circling, head tilt
T/F in CNVIII lesions, the head tilt is away from the lesion
F, it tilts towards the lesion
T/F when performing the cranial nerve exam, if more than one cranial nerve is affected, even if only on one side, the lesion is likely in the brain
T
when performing the cranial exam, if only one nerve is affected and the animal has a normal mental status, the lesion is
outside of the brain (i.e. in the PNS)
what is responsible for the consensual PLR
crossover in BOTH the optic chiasm and the pretectal area
the nt for all preganglionic autonomic neurons is ____ and it always binds to a _____ receptor
Ach; nicotinic
parasympathetic postganglionic neurons release ____ and all receptors are ______
ACh; muscarinic
a limited number of synapses exist where sympathetic neurons release ACh, which all act on
muscarinic receptors in sweat glands, to increase secretion of sweat (M5)
what nerves are parasympathetic
CN III, VII, IX, X and S1-S3 (pelvic nerve)
parasympathetic nerves have _______ preganglionic fibres and _______ postganglionic fibres
long; short
which muscarinic receptors are inhibitory
M2 and M4
what type of ACh receptor is present on striated skeletal muscle
nicotinic
M1 receptors act on _______ to ___________
axon terminals; increase ACh release
M4 receptors act on _______ to __________
axon terminals; decrease ACh release
M5 receptors act on _________ to ___________
sweat glands; increase secretion
M2 receptors act on __________ to ______________
heart; decrease heart rate and force of contraction
M3 receptors act on ___________(4) to ______________
glands, intestines, smooth muscles, bronchioles; increase secretion, increase motility, constrict, constrict
what nerves are part of the sympathetic ns
thoracolumbar outflow; L1-L5
where are sympathetic ganglia
paravertebral, cervical, celiac, mesentric, etc.
sympathetic ns has ________ preganglionic axons and________ postganglionic axons
short; long
what is unique about the adrenal medulla and the sympathetic NS
it has a long preganglionic axon and no postganglionic axon; secretes directly into the bloodstream
adrenergic receptors for NE/E are all
GPCRs (metabotropic)
adrenergic receptors are all excitatory except for
α2/β2
α1 receptors act on ______ to _________
smooth muscles (dilator muscle in pupil; blood vessels in skin; internal bladder sphincter, piloerector muscle); constrict
β1 receptors act on ________ to _________
heart; increase heart rate and force of contraction
β2 receptors act on _________ to ____________
smooth muscles (blood vessels in muscle, bronchioles, detrusor, GI tract; uterus); relax
how does the sympathetic NS dilate the eye
hypothalamus activates SNS -> rostral colliculus -> travels in spinal cord to T1-T3 -> exits and synapses in cranial cervical ganglion -> travels in vagosympathetic trunk to eye -> activates dilator muscle
miotic pupils, enopthalamos, partial protrusion of the 3rd eyelid, and lack of sweating on the affected side (in horses) is a sign of
Horner’s syndrome (loss of sympathetic innervation of the iris)
result of damage to the pelvic nerve or spinal cord or pons
flaccid bladder
result of damage to the spinal cord anterior to the sacral segments
spastic sphincter due to loss of UMN influencing the sphincter reflex
result of damage to the pudendal nerve or sacral segments
flaccid sphincter due to loss of LMN innervating the sphincter
result of damage to the cortex
animal pees whenever the bladder gets full due to loss of the conscious storage phase
internal vs external hydrocephalus
internal: blockage within all or part of the ventricular system (ex. occurs at cerebral aqueduct; get CSF accumulation in the ventricles); external: blockage at arachnoid granulations (get accumulation of CSF in ventricles and subarachnoid space)
Wallerian degeneration
after sublethal damage to a neuron axon, the axon degenerates (both retrograde and anterograde), a growth process is establishes, and eventually (possibly), contact with the target organ/gland/neuron will be re-established
the process of growth is guided by the stroma
axonal regeneration is better in the (CNS or PNS)
PNS
