Blood Brain Barrier

Biol 113 Cell Neuro In the CNS - endothelial ( innermost cells) cells of the capillary are joined by tight junctions - the only way for something to get from blood - neurons is by passing through the endothelial cell membranes. - Long water-soluble cannot pass through (alcohols can because they are small water soluble) but lip-soluble ( like some medicines) molecules can go through the blood-brain barrier - Glucose is the brain’s energy source and has to be transported from the blood through the endothelial cells by glucose transporters - One technique to get molecules through to neurons is to link them to a glucose molecule and it will get transported via a glucose transporter BLOOD BRAIN BARRIER (tightness of capillary walls ) Astrocytes and Their Feet Astrocytes - (glial cells) extend like feet to cover the capillary. They can regulate the tightness of the tight junctions. Peripheral Nervous System (PNS) - Composed of the autonomic nervous system and peripheral nerves - Autonomic (automatic) part of the nervous system that regulates our heart rate ; For sympathetic and parasympathetic, cell bodies in the CNS extend an axon to a ganglion where they synapse with a neuron that goes out to target a muscle/ organ The neurotransmitter used in the ganglion is acetylcholine (ACh) (pre-ganglionic) Sympathetic NS “fight or flight”: The cell bodies (ganglia) are located just outside the spinal cord along the vertical column , the sympathetic chain of ganglia is right next to the CNS so synapsing is quite quick and speedy. So, the preganglionic fiber for the SNS is short. The postganglionic can be quite long - Sympathetic postganglionic neuron releases norepinephrine (NE) (postganglionic) on its target organ - Effects include: an increase in heart rate, blood flow to the muscles by acting on the capillaries to dilate them, an increase in swelling to cool you while you run, inhibits digestion, mobilizes glucose for energy, stimulation of adrenal glands to release epinephrine Parasympathetic PNS: parasympathetic neurons in the medulla, and spinal cord extend long axons along preganglionic fibers) to ganglia that are close to or on the organ innervate. ACh is the neurotransmitter released into the organ. Postganglionic fibers are short. - Rest and digest - Increase blood flow to muscles - Decrease heart rate and respiration Enteric NS: out on the gut forms a nerve net out here a new network of nerves with ganglia interspersed, - Drives gut peristalsis - Controlled by parasympathetic and sympathetic nervous systems - Lots of different neurotransmitters are found here, more research is needed How Neurons do what they do! The cell membrane - phospholipid bilayer ( a molecule that is constructed with a phosphate head- and lipid tails ) - Phosphate heads are exposed to/ like the aqueous medium, they are charged and hydrophilic. - Lipid tails are hydrophobic So the cell membrane is set up like this : - Embedded in this bilayer are proteins, of interest to us are proteins that can allow water-soluble or charged particles into the neuron ( or out of it) - The phospholipid bilayer is semi-fluid so that proteins can twist, squirm, and move a bit within it - Some proteins are transporters and can transport specific molecules or ions into or out of the cell using energy - Some are ion channels - which allow ions to cross the membrane - Can be specific for certain ions or less specific and allow more than one ion to pass through, their opening and closing can be regulated - Some are voltage-gated ion channels and some are ligand-gated ion channels