lecture 9

Question 1

meninges

Answer 1

-thin membrane located between bone and nervous tissue
3 layers : Dura, arachnoid (weblike) and Pia
Help stabilize nervous tissue and protect it against bones

Question 2

subarachnoid space

Answer 2

below arachnoid, filled with CSF

Question 3

meningitis

Answer 3

infection of CSF of subarachnoid space, leads to seizures and loss of consciousness

Question 4

extensions of the dura mater that seperate part of the brain

Answer 4

falx cerebri, falx cerebelli, tentorium cerebelli

Question 5

falx cerebri

Answer 5

seperates two sides (hemispheres) of cerebrum

Question 6

falx cerebelli

Answer 6

fold of dura mater at back of head

Question 7

tentorium cerebelli

Answer 7

seperates cerebrum (top part) from cerebelum and brain stem

Question 8

cerebrospinal fluid (CSF)

Answer 8

secreted and contained within the ventricles, sub-arachnoid space (between pia and arachnoid) and central canal in spinal cord

Question 9

CSF manufactured by the

Answer 9

choroid plexus : made up of capillaries and ependymal cells

Question 10

ependymal cells

Answer 10

pump Na+ and other solutes into ventricles→concentration gradient→ draws plasma into ventrices by osmosis

Question 11

flow of CSF

Answer 11

starts in lateral ventricles→ interventricular foramina of Munro →third ventricle→ cerebral aqueduct→fourth ventricle→ median aperture→central canal→ drains from superior sagittal sinus

when there is a back up of CSF, pressure increases in the ventricles which compress brain blood vessels and leads to damage of them

Question 12

villus

(arachnoid villus)

Answer 12

protrusions of arachnoid mater

arachnoid villus : go through dura mater into sagital sinus

Question 13

function of CSF

Answer 13

mechanical protection of the brain

• shock absorbtion, buoyancy
• chemical protection of the brain
• contributes to extracellular environment of neurons (high in Na and low in K)
• transport of metabolites, waste products out of the CNS into the venous circulation

Question 14

what is the only substrate metabolized by the brain

Answer 14

• glucose
• no brain glycogen storage so we need continuous blood supply
• if we reduce blood supply to the brain, then ion pumps will fail and ion membrane gradients decrease on outside

Question 15

blood supply/ drainage to the brain

Answer 15

→supplied by the internal carotid arteries and the vertebral arteries

→drained by the internal jugular veins

Question 16

blood brain barrier

Answer 16

final layer of protection of brain, nourishment to brain

formed by : endothelial cells connected by tight junctions

tight junctions controlled by Astrocytes, control what comes in/out and at what rate

tight junction allows brain to selectively import nutrients and energy, while simultaneously excluding neurotoxic substances

Question 17

plasma membrane

Answer 17

selectively permeable to lipid soluble molecules (Eg. 02, C02, fatty acids, steroids, alcohol, nicotine, some drugs) -can pass through membrane without resistance

some solutes cannot pass through plasma membrane eg. sodium, potassium, glucose, amino acids

Question 18

facilitated diffusion

Answer 18

• movement of large or charged particles (eg. glucose, amino acids) across membrane
• carrier proteins : binding of target substance initiates change and allows passage of molecule

Question 19

function of BBB

Answer 19

• maintaining stable neural environment against fluctuations in content of circulating blood (hormones, ions or NT’s)
• chemical protection of the brain
• some areas of CNS where the BBB is “leaky”

Question 20

concussion

Answer 20

type of tramatic brain injury caused by a bump, blow or jolt to the head, or hit to the body that causes the head and brain to move rapidly back and forth

-creates chemical changes in the brain and sometimes stretching and damaging of brain cells

Question 21

changes at the neuron during concussion

Answer 21

1. stretching of axon
2. depolarization
3. K+ flux out and Ca+ flux into neuron
4. Na/K ATPase pump tries to maintain conc. gradient (requires ATP)
5. increased glycolysis to produce ATP →lactate acumulation
6. metabolite buildup causes axon sweling
7. decreased function

Question 22

long term

Answer 22

tau proteins stabilize axons

• repeated concussions= increased tau
• buildup of tau overtime is toxic to axon
• leads to neuronal dysfunction and cell death

Question 23

response to exercise and cold pressor test

Answer 23

exercise : increased HR in concussed people, lower stroke volume so need to compensate with increased HR

cold pressor test : SNS not as activated in concussed individuals