Synaptic Transmission

Front 1

Events associated with transmission of impulses

Back 1

-depolarization of axon termial
-opening of voltage-gated Ca++ channels
-exocytosis of neuro transmitter into synaptic cleft
-neurotransmitter diffuses across synaptic cleft and binds to receptor sites on postsynaptc membrane

Front 2

Excitatory Neurotransmitter

Back 2

will depolarize the postsynaptic membrane and an action potential may be generated - opening of Na+ ion channel often often cause depolarization

Front 3

Inhibitory Neurotransmitter

Back 3

will hyperpolarize
- increased Cl- or K+ potassium permeability

Front 4

Summation

Back 4

whether or not an action potential is generated depends on the total excitatory and inhibitory inputs at any instant

Front 5

Fate of neurotransmitters

Back 5

1) taken back up by the presynaptic nerve
2) broken down by enzyms
3) both

Front 6

Glutamate and Aspartate

Back 6

1) amino acid
2) excitatory
3) high concentrations in the cerebral cortex

Front 7

Glycine

Back 7

1) amino acid
2) inhibitory
3) spinal cord, reticular formation

Front 8

GABA

Back 8

1) amino acid
2) inhibitory
3) widespread in the CNS
4) increases chloride or potassium permeability
5) Benzos enhance inhibitory actions of GABA

Front 9

Acetylcholine

Back 9

1)monoamine
2) excitatory
3) released from cholinergic nerves: the RAS includes cholinergic nerons that originate into the midbrain and innervate the hypothalamus, thalamus
4) nicotinic & muscarinic receptors

Front 10

Dopamine (DA)

Back 10

1) monoamine
2) "reward pathway" of brain
3) neurons origonate in the substantia nigra nd project to the striatum to regulate motor activity of the basal ganglia
5) the neurons are lost in Parkinson's disease, excess DA in the limbic system may play a role in schizophrenia

Front 11

Norepinephrine (NE)

Back 11

1) monamine
3) found in adrenergic neurons that originate in the locus ceruleus - project to the thalamus and cerebral cortex
4) important in the arousal areas
5) reduced activity may cause depression, excess may cause mania

Front 12

Serotonin (5-HT)

Back 12

1) monoamine
2) excitatory and inhibitory
3) neurons originate in the raphe nuclei in the pons projecting to reticular formation, thalamus, limbic system, cerebral cortex
5) reduced may cause depression

Front 13

Substance P

Back 13

1) neuropeptide
3) found in neurons of substantia nigra, basal ganglia, hypothalamus, and crebral cortex
4) in spinal cord involved in transmission of pain signals

Front 14

Opioid Peptides

Back 14

1) neuropeptide
3) interfere wtih pain transmission/perception in the CNS
4) bind to opioid receptors
endorphins: beta-endorphin, dynorphin
enkephalins: met-enkephalin, leu-enkephalin

Front 15

Arterial Blood Supply

Back 15

internal carotid and vertebral arteries (from subclavian arteries) ascend through cervical vertebrae adn unite to the basilar artery. The basilar artery travels along the brainstem and divides into 2 cerebral arteries which together with the 2 carotid arteries supply the circle of Willis @ base of brain

Front 16

Rate of cerebral blood flow in adults

Back 16

750 mL/min (50 mL/100g/min)
15% of resting cardiac output

Front 17

CBF

Back 17

- cerebral metabolic requirement for oxygen (CMRO2) aprox. 3.0-3.8 mL O2/100g/min
- directly proportional to the arterial PCO2
- can be influenced by temperature and autonomic innervation

Front 18

Autoregulation of CBF

Back 18

- maintained nearly constant despite flucuations in MAP b/w 60 and 150 mmHg
- outside these limits the CBF increases/decreases proportionaly with arterial pressure
- curve shifts to right in pts with HTN
- impaired or abolished by trauma, hypoxia and anesthetic agents

Front 19

Ventricular System of brain

Back 19

- four ventricles and subarachnoid space of both brain and spinal cord

Front 20

CSF

Back 20

~ 100-150 mL of CSF contained in the skull and spinal canal
- protects brain and spinal cord against trauma
- pressure nomally 10 mmHg
- isosmotic

Front 21

Choroid Plexus

Back 21

network of blood vessels surrounded by a layer of epithelial cells projecting into each of the brain ventricles esp. the lateral ventricles
- forms CSF @ ~ 500mL/day (.3 to .4 mL/min)

Front 22

Secretion of CSF is driven by what?

Back 22

active transport of Na+ from blood to CSF, this establishes an osmotic gradient, which pulls in chloride, bicarb, water, gases, K+, glucose, and amino acids

Front 23

Arachnoid villi

Back 23

finger like projctions of the arachnoid membrane into the sagittal sinus that absorb CSF into the cerebral venous blood
- rate of absorption equals the rate of formation

Front 24

BBB

Back 24

"tight" continuous endothelium of the cerebral capillaries that is permeable to water, 02, CO2, volitile anesthetics, and small lipophilic substances (opiods)

Front 25

Permeabilities of BBB

Back 25

- limited permeability to electrolytes, impereable to plasma proteins
- glucose transported in by facilitated diffusion
- circulating substances (Ach, norepi, epi, dopamine, glycine, histamine, and peptides) that act like neurotransmitters are blocked

Front 26

Difficulties of BBB

Back 26

difficulty in delivering potentially useful therapeutic agents (antibiotics)