Fail's Exam 1 Flashcards
functions of the cerebrum
consciousness, perception, voluntary movements, and executive functions
brainstem general function
homeostatic functions, cranial nerves have sensory/motor function, arousal and sleep, neuronal pathways to/from cerebrum
cerebellum general function
motor coordination, timing and planning of complex movements
where are the paleocortex and archicortex found in the brain?
cerebral cortex “old cortex”
includes the hippocampus, limbic cortex, and olfactory regions
where is the neocortex found in the brain? what distinguishes it from other kinds of cerebral cortex?
found in the cerebral cortex
regional (perception, motor, executive functions, auditory cortex, motor cortex, visual cortex)
histological specialization (6 distinct layers)
Distinguish between an ion channel receptor and a receptor that works through second messengers. How are they similar? How are they different?
ion channel - iontropic, fast response
GPCR - metabotropic, slow response, acts by 2nd messengers
What are some of the consequences of activating G-protein linked receptors (what cellular effects might they have)?
there is a possibility of many possible behaviors
Distinguish between a ligand-gated ion channel and a voltage-gated ion channel.
ligand-gated - requires ligand (NT) to open channel
voltage-gated - requires change in membrane potential to open channel
By what mechanisms are neurotransmitters removed from the synaptic cleft? Which are most important*?
diffusion
*uptake by surrounding cells
*enzymatic degradation
effect of Fluoxetine (Prozac)
prevents the reuptake of serotonin at serotonergic synapses
antidepressant –> keeps serotonin in the synapse = happy
effect of organophosphates
inhibit AChE
Ach not being taken back up = increased activity at cholinergic synapses = constant muscle contraction
Describe the relative concentrations of Na+, K+, and Ca2+ in the intraneuronal versus extracellular fluid.
Intraneuronal fluid: high concentrations of Na+ and Ca2+
Extracellular fluid: high concentrations of K+
Define “excitatory” in a neurotransmitter sense. What happens at an excitatory synapse that makes a neuron more likely to produce an action potential?
excitatory: depolarization due to influx of Na+ that allows initiation of action potential
What is the most common excitatory neurotransmitter in the central nervous system?
glutamate
Define “inhibitory” in a neurotransmitter sense. What happens at an inhibitory synapse that makes a neuron less likely to produce an action potential?
inhibitory: hyperpolarization due to influx of K+, no action potential
What is the most common inhibitory neurotransmitter in the brain?
GABA
What is the most common inhibitory neurotransmitter in the spinal cord?
glycine
Neurotransmitter: ACh
Iontropic/Metabotropic
Predominant Effect on Postsynaptic Membrane:
found at the NMJ
iontropic (nAChR) - conductance for Na & Ca
metabotropic (mAChR) - M2 inhibitory & M3 excitatory
Neurotransmitter: Dopamine
Iontropic/Metabotropic
Predominant Effect on Postsynaptic Membrane:
metabotropic (GPCR)
excitatory & inhibitory
motor behavior & mood
Neurotransmitter: GABA
Iontropic/Metabotropic
Predominant Effect on Postsynaptic Membrane:
ionotropic (Cl- ion channel)
inhibitory only in the brain
Neurotransmitter: Glutamate
Iontropic/Metabotropic
Predominant Effect on Postsynaptic Membrane:
iontropic (AMPA)
iontropic (NMDA) - admits both Na & Ca
metabotropic (GPCR)
excitatory only in CNS
Neurotransmitter: Glycine
Iontropic/Metabotropic
Predominant Effect on Postsynaptic Membrane:
ionotropic (Cl- channel)
inhibitory only to the spinal cord
Neurotransmitter: Norepinephrine
Iontropic/Metabotropic
Predominant Effect on Postsynaptic Membrane:
adrenergic receptors (GPCR)
alpha 1, 2 and beta 1 and 2
sympathetic neurons associated with mood, attention, sleep-wake cycles
alpha 1 receptor
constriction of smoth m.
alpha 2 receptor
primarily inhibitory
beta 1 receptor
increase cardiac function (strength of contract & speed of conduction)
beta 2 receptor
smooth m. relaxation (e.g. bronchial walls)
Describe the arterial blood supply to the canine brain.
vertebral a.
internal carotid aa.
what does the cerebral arterial circle surround
optic nn. & chiasm & pituitary on base of brain
Rete mirabile
modified intracranial parts of internal carotid a.; NOT in dogs or horses; speculations with brain cooling
what arteries make up the cerebral arterial circle
rostral cerebral aa.
middle cerebral aa.
internal carotid aa.
caudal communicating aa.
caudal cerebral aa.
rostral cerebellar aa.
what does the rostral cerebral aa. supply
medial aspect of hemisphere
what does the middle cerebral aa. supply
lateral aspect of cerebrum
what does the caudal cerebral aa. supply
occipital region (medial & lateral) of cortex
what arteries come off the basilar a.
labyrinthine aa.
caudal cerebellar aa.
main supply to the spinal cord
ventral spinal a.
what does the central branch of the ventral spinal a. supply
what is its clinical significance
gray matter of spinal cord
fibrocartilagenous embolism (FCE)
what do the dorsal spinal aa. supply
white matter
what do the vertebral aa., intercostal aa., lumbar aa., median sacral a. give rise to
spinal brr –> radicular brr
Name the layers of the meninges and describe their relationships to one another.
dura mater - superficial/tough
arachnoid - middle layer, subarachnoid space, connected to dura via fibroblasts and to pia via arachnoid trabeculations
pia mater - deepest laye
Describe the anatomical differences between spinal and cranial meninges.
Cranial meninges have the two dura mater layers (periosteal and meningeal layers) that are fused except at the dural sinuses
Cranial meninges dural reflections create broad dividing sheets w/in braincase
Cranial epidural space is potential space only
Subarachnoid space has expanded regions “cisternae” in cranial meninges
Epidural space of spinal cord
real space
Subdural space
potential
Subarachnoid space
real
epidural space of the cranium
normally no epidural space of cranium but can have a epidural hematoma
potential
components of choroid plexus
capillaries + c.t. + simple cuboidal epithelium with tight junctions
why is the choroid plexus endothelium leaky
lack of tight junctions
difference between the blood-brain barrier and blood-CSF barrier
BBB has tight junctions on endothelial cells
blood-CSF barriers endothelium is leaky, no astrocytes, but has has tight junctions in choroid epithelium
how is CSF produced
produced by ependymal of choroid plexus via active secretion and by ependymal which line ventricles
Trace CSF’s circulation through the ventricular system to the subarachnoid space and to its ultimate reabsorption back into the circulatory system.
CSF circulate through ventricles and central canal
CSF passes through subarachnoid space (high P) via lateral apertures of 4th ventricle
CSF absorption at arachnoid granulations → into venous sinuses (low P) → internal jugular v.
-passive, one-way, dependent on pressure gradient (CSF > venous)
Describe how changes in blood osmotic pressure can affect CSF production.
CSF production influenced by blood osmotic pressure (Increase in blood osmotic pressure decreases CSF production)
what is CSF not influenced by
blood pressure or pressure of CNS w/in ventricles
Describe how changes in hydrostatic pressure in the venous system can affect CSF reabsorption, with reference to the function of specific anatomical elements.
Reabsorption of CSF is dependent on presence of hydrostatic pressure between subarachnoid space (high P) and venous sinus (low P)
- Increase in hydrostatic pressure increases CSF reabsorption
- Increase in venous pressure will decrease CSF reabsorption
CSF reabsorbed by arachnoid granulations into venous sinuses which drain into internal jugular v.
Define hydrocephalus. Describe conditions under which it might develop.
Hydrocephalus: dilation of ventricular system, “water head”
Obstruction to the outflow of CSF can occur at the arachnoid granulations (e.g.,
as a consequence of meningitis) or somewhere more proximal in the circulation of CSF (e.g., a mass in the midbrain compressing the mesencephalic aqueduct).
What is the blood-brain barrier?
what does it protect the CNS from?
______ makes up tight junctions
where is it found?
-barrier between blood and ECF of CNS
- protects CNS from dangerous blood constituents (K, glutamate, albumin)
-astrocytic end feet/pericytes with tight junctions in CNS endothelial cells
-brain & spinal cord
What is the blood-CSF barrier?
between blood & CSF
tight junctions in epithelium, not endothelium
what can pass through the BBB
gases, substances with specific transporters (e.g. glucose/AA), lipid-soluble substances, very small molecules
major dural sinuses…
falx cerebri has ____ & _____
tentorium cerebelli has ______
diaphragma sellae has _______
dorsal sagittal sinus
straight sinus
transverse sinuses
cavernous sinuses
what are the dural reflections
falx cerebri
tentorium cerebelli
diaphragma sellae
what is the clinical significance of the tenorial incisure (notch)
increase intracranial pressure can cause the brain to herniate through the notch compressing the brainstem
needle placement for CSF collection in small animals
cerebellomedullary cistern (cisterna magna - between cerebellar & medulla)
needle placement for CSF collection in large animals
cerebellomedullary cistern or lumbar cistern
needle placement for epidural anesthesia in small animals
L7-S1 epidural space
needle placement for epidural anesthesia in large animals
Cd1-2 more common than S5-Cd1 epidural space
