Ch. 5 — For Exam 1 Flashcards
The brain receives ____% of cardiac output (800 ml per minute), and uses ____% of body oxygen
20%; 20%
CNS vasculature must be _________ to supply oxygen and b/c CNS stores little or no ________
Continuous; glucose
True or False:
CNS blood flow rates change minimally /c increases in the level of celebration (flow rates are mostly determined by vascular pressure differences)
True
What are the two arterial supply systems of CNS?
- Vertebral arteries (aka vertebrobasilar system)
2. Internal carotid arteries
What arteries are…
- paired
- enter skull thru foramen magnum on the ventrolateral surfaces of the spinal cord
Vertebral arteries
The vertebral arteries has paired _____________ arteries, which unit to from a single midline artery and the ______________ artery.
Anterior spinal aa.; posterior inferior cerebellar aa.
The union of the vertebral arteries forms the _______ a., which is a ingle midline a. That courses to the midbrain.
Basilar a.
What are the 3 branches of the basilar a.?
- Anterior inferior cerebellar a.
- Short pontine branches
- Superior cerebellar aa.
At the midbrain, the basilar a. Bifurcated to form the two __________ arteries
Posterior cerebral arteries
What 3 areas does the posterior cerebral a. Supply?
- Caudal diencephalon
- Medial & lateral occipital lobes (visual cortex)
- Posterior inferior temporal lobe
Which arteries pass thru the cavernous sinus to the base of the brain /c several branches?
Internal carotid arteries
What are the two branches of the internal carotid artery that enter thru the cavernous sinus?
- Ophthalmic A.
2. Posterior Communicating a.
The internal carotid a. Terminates lateral to the __________ as what two terminal branches?
Optic chiasm
- Middle cerebral a.
- Anterior cerebral a.
Which artery…
- passes laterally thru the lateral fissure to supply the lateral orbital gyri and lateral parts of the frontal, parietal, and temporal lobes
Middle cerebral a.
Some branches of the ________a. Pierce to supply to basal ganglia, diencephalon, and internal capsule.
Middle cerebral
Which artery….
- passes anteriorly to supply the orbital and medial aspects of the frontal lobe and medial aspect of the parietal lobe
Anterior cerebral a.
The R and L anterior cerebral arteries are connected in the midline by what?
Anterior communicating artery
What is the Circle of Willis?
An arterial ring at the base of the brain
What does the circle of Willis allow for?
Anastomoses btw the vertebrobasilar and carotid arteries
The circle of Willis may act as what?
A safety valve if one portion of the circle becomes obstructed
What 5 arteries/ artery pairs are included in the Circle of Willis?
- Posterior cerebral arteries (paired)
- Posterior communicating arteries (paired)
- Internal carotid arteries (paired)
- Anterior Cerebral arteries (paired)
- Anterior communicating arteries.
Valveless venous channels btw two layers of the dura mater
Dural sinuses
What drains into the superior sagittal sinus?
Upper, lateral, and medial cortex
The superior sagittal sinus is located superiorly in the midline and flows toward the ________ region
Occipital
The superior sagittal sinus drains into the __________ sinus, which drains laterally into the ______ sinus.
Transverse; sigmoid
Venous blood ultimately drains into the _________ vein at the base of the skull
Internal jugular
Deep cerebral venous blood flows to what 4 things?
- Great vein of Galen
- Straight sinus
- Transverse, sigmoid sinus
- Internal Jugular vein
- connect some dural sinuses /c veins that are superficial to the skull
- can be a route for spread of infection from face or nasopharynx
Emissary veins
Vascular insufficiency for more than several minutes can result in __________
Infarction (necrosis)
- ex. Stroke, CVA
Vascular insufficiency can be caused by what two things?
- Occlusion (via thrombus or embolus)
2. Hemorrhage (usually more severe)
- temporary neurological dysfunction
- warning sign of vascular insufficiency
Transient ischemic attack (TIA)
What substances do not pass from the blood into the brain?
Large proteins and penicillin
True or False:
Neuro damage can break down the blood-brain barrier
True
What part of the neuron usually receives and integrates signals?
Dendrite-soma
What part of the neuron functions to conduct or transmit the signal away from the cell?
Axon
What part of the neuron is the effector segment (where the action is passed on)?
Synapse
A peripheral neuron which conveys information (sensory) to the CNS about the external environment
First-order neuron
The peripheral process begins in sensory tissues such as what? (4 things)
- Retina
- Skin
- Muscles
- Joints
The charged state of a cell at rest (not conducting an impulse)
Resting potential
The resting potential is a comparison of the difference btw the ______ and ________ of the cell (intracellular and extra cellular fluid)
Inside; outside
What 3 things diffuse freely across the semipermeable plasma membrane through non-gated open channels?
- Sodium
- Chloride
- Potassium
Sodium and Chloride are highly concentrated _______ the cell. Potassium and organic anions are highly concentrated _______ the cell.
Outside; inside
What does the sodium-potassium pump do?
- pumps 3 sodium’s out of the cell for every 2 potassium’s pumped in
- requires ATP
What establishes the electrical potential difference across the cell membrane?
The sodium potassium pump
What is the electrical potential difference of the cell membrane?
-60 (outside the cell) to -90 (inside the cell)
Allows the calculation of the magnitude of potential at which ions are in equilibrium across a membrane
Nernst equation
The Nernst equation only considers ______ channels, not ______ channels
Open; gated
The resting membrane potential is mostly due to what?
Potassium
Why does sodium only contribute a small amount to the cells resting potential?
B/c sodium channels are gated, so they are not open in a resting cell
- enables a neuron to respond to and transmit info as an electrical signal
- a stimulus may cause a change in the resting membrane potential (depolarization) by opening or closing channels (allowing passive diffusion of concentrated ions)
Excitability of a neuron
Always permit passage of ions; involved in maintaining resting potentials
Open channels
Have a molecular gap or gate which can open to permit passage of particular ions and will not allow passage of other types of ions
Gated channels
The process by which a channel is opened during activity
Gating
What are 3 types of gating?
- Chemical channels
- Modality-specific channels
- Voltage-gated channels
Have gates which respond to chemicals or transmitters
Chemical channels
Have gates which open when the membrane potential changes
Voltage-gated channels
Respond to specific modalities such as touch
Modality-specific channels
What are the two types of membrane responses?
- Hyperpolarization
2. Depolarization
Membrane becomes more negative on its inside
Hyperpolarization
Membrane becomes less negative on the inside, may even become positive
Depolarization
What are the 5 functional organizations of the neuron?
- Receptive segment
- Initial segment
- Conductive segment
- Transmissible segment
- Tropic segment
The reception of a stimuli (chemically or modality gated) results in a __________
Local potential
The most common receptive segment is _____
Dendrite-soma unit
The postsynaptic receptor membrane is responsive to neurotransmitters from the _________ vesicles
Presynaptic
At the dendrite-soma unit, chemically gated channels open to allow ________ to flow in and ______ to flow out. The result is a ___________ potential which is _________.
Sodium; potassium
Receptor (local); graded (short duration and short distance)
What is an excitatory postsynaptic potential (EPSP)?
A partial depolarization at the dendrite-soma unit, which is insufficient to generate an action potential
When a closely successive stimuli brings the membrane closer to depolarization after an EPSP
Temporal summation
When closely placed local potentials have an additive effects in overlapping margin areas after an EPSP
Spatial summation