Final Exam Physio

Descartes

(1596-1650) French philosopher, discovered analytical geometry. Saw Algebra and Geometry have a direct relationship. Reduced everything to spiritual or physical. - proposed that mind and brain interact in the pineal gland.

Types of glia (aka "neuroglia")

- Glia helps support, connect, and protect the neurons of the central and peripheral nervous system. - Glia means Glue in Greek as it was thought they served as a function to hold neurons together. Idea is now obsolete. - Neurons outnumber glia. Astrocytes - Star shaped. - wraps around the dendrites connecting to functionally related axons. - A single astrocyte might surround the tips of a few hundred dendrites. - It shields the neurons from chemicals circulating around it. - By taking up the ions and transmitters released by axons and then releasing them back, an astrocyte helps synchronize closely related neurons, enabling their axons to send messages in waves. - Important for generating rhythms, such as rhythm of breathing. - Also dilate blood vessels to bring more nutrients into the most active brain areas. - help synchronize the activity of the axon by wrapping around the presynaptic terminal and taking up chemicals released by the axon. - Tripartite synapse: hypothesis that the tip of an axon releases chemicals that cause the neighboring astrocyte to release its own chemicals, thus modifying the message to the next neuron. - In some brains, astrocytes respond to hormones and thereby influence neurons. - Also control the critical period for modification of the visual cortex early in life. - in short, astrocytes are active partners of neurons. Microglia - tiny cells that act as part of the immune system. - removes waste material, viruses, and fungi from the brain. - also removes dead, dying, or damaged neurons. - prune ineffective synapses and adjust the effectiveness of others. - too much or too little pruning can result in developmental disorders during early development. - ALSO provides negative feedback to put the brakes on neuronal activity. - Loss of microglia leads to seizures.

Dualism

- Mind and body are different kinds of substances, that exist independently but somehow interact. - the idea that minds are one type of substance and matter is another.

Which chemicals cross the blood-brain barrier passively?

- Molecules that dissolve fats enter passively. - water - several ions for which the membrane has specific channels.

ESPSs, IPSPs, and Action Potential

- Neurons may have thousands of synapses along its membrane, some generating EPSPs others IPSPs. - A neuron has a spontaneous rate of firing (action potentials) that occurs even without any synaptic input. EPSPs and IPSPs can influence this rate. - The rate of firing is increased with greater EPSPs and decreased with greater IPSPs. - But any behavior is a function of many, many neurons.

Monism

- There is only one kind of existence. - the idea that the universe consists of only one type of being.

Resting potential

- condition of a neuron's membrane when it has not been stimulated or inhibited. Resting potential is maintained after slight stimulation. Hyperpolarization: increase in the negative charge inside the neuron; returns to rest after small increase. Depolarization: decrease in the negative charge inside the neuron; returns to rest after small decrease. - voltage is -70mV inside relative to outside of neuron - far more (10x) sodium (NA+) outside than inside - far more (20x) potassium (K+) inside than outside - more negatively charged ions inside (negatively polarized) WHAT CAUSES RESTING POTENTIAL? - membrane has selective permeability - sodium potassium pump - electrical gradient - concentration gradient - K+ is balanced; NA+ can't enter because NA+ gates are closed. - K+ gats are partially closed. - researchers measure resting potential by inserting a micro electrode into the cell body.

Catecholemines

- dopamine - norepinephrine - epinephrine

Amino acids

- glutamate - GABA - asparate

EPSP (excitatory postsynaptic potential)

- graded DEPOLARIZATION that results from flow of NA+ (sodium) ions INTO the neuron. EPSP can produce temporal summation to exceed the threshold. - summate in the soma. - if depolarization is past threshold, an action potential begins at the hillock.

IPSP (inhibitory postsynaptic potential)

- graded temporary HYPERPOLARIZATIOn of a membrane. - occurs when synaptic input selectively opens the gates for K+ ions to leave the cell or for Cl- to enter the cell. - summate in the soma.

selectively permeable

- membrane of a neuron is selectively permeable, MEANS letting some chemicals pass more freely than others. - WHEN A MEMBRANE IS AT REST = sodium and potassium channels are closed, permitting almost no flow of sodium and only a small flow of potassium. Stimulation can open these channels, permitting freer flow. chemicals that cross freely: - oxygen - carbon dioxide - urea - water Chemicals that sometimes cross through channels/gates that are sometimes open and sometimes closed: - sodium - potassium - calcium - chloride

Thiamine

- neurons rely heavily on glucose, the only nutrient that crosses the blood-brain barrier in large quantities. - to use glucose, the body needs vitamin B1, aka Thiamine. - prolonged thiamine deficiency, common in chronic alcoholism, leads to death of neurons and a condition called Korsakoff's syndrome, marked by memory impairments.

sodium-potassium pump

- pumps 3 NA+ (sodium) ions out of cell for every 2 K+ (potassium) ions pumped in - a protein complex that repeatedly transports three sodium ions OUT of the cell while drawing two potassium ions IN. - because of the sodium-potassium pump, sodium ions are more than 10x more concentrated outside the membrane than inside, and potassium ions are more concentrated inside than outside. - effective only because the selective permeability of the membrane prevents the sodium ions that were pumped out from leaking back again. - When sodium ions are pumped out, they stay out. - HOWEVER, some of the POTASSIUM in the neuron slowly leaks out, carrying a POSITIVE charge = increase of electrical gradient across the membrane.

Concentration gradient

- pushes NA+ (sodium) in and K+ (potassium) out - difference in distribution of ions across the neuron's membrane. - tends to push sodium into the cell.

Electrical gradient (aka polarization)

- pushes NA+ (sodium) in and K+ (potassium) out. - when at rest, the membrane of a neuron maintains an electrical gradient. - difference in electrical charge between the inside and outside of the cell. - the inside of the membrane has a slight negative charge compared to the outside, mainly because of negatively charged proteins inside the cell. This difference in voltage is called the resting potential. - When the potassium in the neuron slowly leaks out after the sodium-potassium pump, a protein complex, the leakage increases the electrical gradient across the membrane. - the electrical gradient pushes sodium into the cell as sodium is positively charged and the inside of the cell is mainly negatively charged. Opposite electrical charges attract. - ELECTRICAL GRADIENT ATTRACTS SODIUM INTO THE CELL.

Thresholds

- stimulation beyond a certain level crosses the threshold of excitation and produces a sudden, massive depolarization of the membrane.

One advantage and disadvantage of having a blood-brain barrier.

Advantage - keeps out viruses and many harmful chemicals Disadvantage - also keeps out most nutrients.

Types of Glia (simple)

Astrocytes = synchronizes the activity of a related group of axons. Stabilize and regulate the blood-brain barrier. Promote synapse formation. Microglia = removes dead neurons and prunes ineffective synapses. Oligodendrocytes = build myelin sheath in the brain and spinal cord. Schwann cells = build myelin sheath in the periphery of body. Radial Glia = guide migration of neurons and their axons and dendrites during embryonic development.

Which type of glia synchronizes the activity of a related group of axons?

Astrocytes.

Suppose researchers find that axon A can produce up to 1,000 action potentials per second (at least briefly, with maximum stimulation), but axon B can never produce more than 100 per second (regardless of the strength of the stimulus). What could we conclude about the refractory periods of the two axons?

Axon A must have a shorter absolute refractory period, about 1 ms, whereas B has a longer absolute refractory period, about 10 ms.

Animism

Belief that moment of the body was accomplished by animating spirits (prior to Descartes).

How the blood brain barrier works

Brain Barrier: - mechanism that excludes most chemicals from the vertebrate brain. - The blood vessels that exist in the central nervous system (CNS) possess unique properties, termed the blood-brain barrier, which allow these vessels to tightly regulate the movement of ions, molecules, and cells between the blood and the brain. Why we need it? Virus invades a cell - mechanisms within the cell extrude virus particles through the membrane so that the immune system can find them (the virus particles) and rid the body of the virus. Basically the cell is saying "look immune system, I'm infected with this virus. Kill me and save the others." What can pass the blood brain barrier? - the spirochete (responsible for syphilis). - particles from chicken pox may remain in the spinal cord cells, emerging decades later, causing shingles. - virus responsible for herpes hides in the nervous system. How it Works - depends on the endothelial cells that form the walls of the capillaries. - Outside the brain, cells along the capillaries are separated by small gaps, but in the brain, they join so tightly they block almost anything from passage. - Water crosses through special protein channels in the wall of the endothelial cells. - The brain uses active transport (a protein mediated process that expands energy to enable a molecule to cross a membrane), to pump glucose, amino acids, omega 3 fatty acids, and several vitamins fro the blood into the brain. Funfacts about blood brain barrier - Chemicals that dissolve fats cross freely through the cell walls. Ex. oxygen, carbon dioxide, vitamins A & D, and all the drugs that affect the brain (antidepressants and other psychiatric drugs to marijuana and heroin). - tends to become less efficient in old age, especially people with Alzheimer's.

CNS (central nervous system)

Brain and Spinal Cord; Coordinates, controls, and responds.

Axon hillock

Cone shaped region of an axon where it joins the cell body.

What do most inhibitory iontropic synapses use?

GABA, which opens Cl- gates. Glycine is found as well.

graded potentials

Graded potentials: changes in membrane potential that vary according to the size of the stimulus, as opposed to being all-or-none. - all changes in voltage before the hillock is called a graded potential. - They may either be depolarizations (excitatory) or hyperpolarizations (inhibitory), and they decay over both time and distance. A graded depolarization = an excitatory postsynaptic potential (EPSP), which results from a sodium ions entering the neuron. A graded hyperpolarization = inhibitory postsynaptic potential (IPSP), produced by flow of negatively charged chloride ions into the cell.

Structure of a neuron (w/ diagram)

Human nervous system comprises of two kinds of cells; neurons and glia - human brain contains approximately 86 billion individual neurons. Soma ("body") - contains the nucleus and other cell structures. Dendrite ("tree") - branching fibers that get narrower as they extend from the cell body toward the periphery. - receives information and sends to soma. Dendrite spines - short outgrowths that increase the surface area available for synapses. Axon - thin fiber that sends information from soma to the pre-synaptic terminals. Axon hillock - junction between axon and soma. Myelin sheath - insulating material covering axons in many neurons (but not all); speeds up communication along the axon. Nodes of Ranvier - bare areas between myelin sheath Presynaptic terminal (terminal buttons or end bulb) - the end point of the axon that releases chemicals.

Iontropic vs. metabotropic

Iontropic - synaptic effects that depend on the rapid opening of some kind of gate in the membrane - "on/off" effects the Sherrington and Eccles studied. - Effects localized to one point on the membrane - useful for things like hearing and vision when the brain needs rapid, up-to-date information Metabotropic a sequence of metabolic reactions that produce slow and long-lasting effects at a synapseemerge at 30 ms or so after the release of the NT- things like taste, smell, pain, arousal, attention, emotion, and pleasure that have more enduring effects use this.

which type of glia cell removes dead neurons and prunes ineffective synapses?

Microglia.

Structure of a neuron cont.

Motor neuron - has its soma in the spinal cord - receives excitation from other neurons. - Conducts impulses along its axon to a muscle or gland. Sensory neuron - is specialized at one end to be highly sensitive to a particular type of stimulation (touch, light, sound, etc.)

Types of glia CONT.

Oligodendrocytes - in the brain and spinal cord. - build the myelin sheaths that surround and insulate certain vertebrate axons. - supply an axon with nutrients necessary for proper functioning. - respond to neural activity by altering the myelin sheaths, thereby altering the timing of axons' responses. Therefore participating in certain types of learning and memory. Schwann cells - in the periphery of the body - build the myelin sheaths that surround and insulate certain vertebrate axons . - supply an axon with nutrients necessary for proper functioning. Radial Glia - guide the migration of neurons and their axons and dendrites during embryonic development.

Refractory period

Refractory period - time when the cell resists the production of further action potentials. - depends on: 1. the sodium channels being closed. 2. potassium is flowing out of the cell. absolute refractory period (1ms) - sodium gates are firmly closed. - the membrane cannot produce an action potential, regardless of the stimulation. - the time when the membrane cannot produce an action potential (rapid sequence of changes in the voltage across a membrane), regardless of stimulation. - caused by the sodium channels at the peak of the action potential shutting tightly and remain tightly shut for the next millisecond. Relative Refractory period (another 2-4ms) - the sodium gates are reverting to their usual state, but potassium is still out of balance. - a stronger than normal stimulus can result in an action potential. -After that millisecond, the sodium channels relax a bit, but the rapid departure of potassium ions has driven the membrane potential further into negative territory than usual. - When that happens, usually lasting 2-4 milliseconds, the membrane is in a relative refractory period. - This is the time after the absolute refractory period that requires a stronger stimulus to initiate an action potential.

Saltatory conduction

Saltatory conduction: the jumping of action potentials from node to node. - "saltare" means to jump... remember somersaults. - more energy efficient (less work on sodium-potassium pump)

Cajal

Santiago Ramon y Cajal - Spanish researcher. - wanted to be an artist but father insisted he study medicine. Used his artistic skills to illustrate his medical research. Detailed drawings of the nervous system. - Came up with the idea that the brain consists of individual cells. - Used Golgi's staining method to show that nerves cells are contiguous (close but not touching). He applied them to infant brains. - Came to the conclusion that nerve cells remain separate instead of merging into one another. A small gap separates the tip of a neuron's fiber from the surface of the next neuron. Indeed the brain DOES consist of individual cells. - Cajal and Golgi shared the 1906 Nobel Price for Physiology or Medicine. - In Cajal's acceptance speech he outlined the cellular basis of the brain, while Golgi continued to defend the theory that all nerve cells merge directly into one another.

When the membrane is at rest, are the sodium ions more concentrated inside the cell or outside? Where are the potassium ions more concentrated?

Sodium ions are more concentrated outside the cell, and potassium is more concentrated inside.

Somatic vs. Autonomic

Somatic consists of axons conveying messages from the sense organs to the CNS and from the CNS to the muscles.

CHAPTER 2 Synapse

Synapse: a specialized gap as a point of communication between two neurons anatomy of chemical events. neurons communicate by transmitting chemicals at junctions called "synapses". 3 parts of synapse - presynaptic membrane (at terminal button) - synaptic cleft - postsynaptic membrane (usually at dendrite)

propagation of the action potential (thin vs. thick)

The action potential begins at the axon hillock For unmyelinated axons - as Na+ (sodium) ions enter the axon they depolarize the neighboring area and regenerate the action potential in a flowing action down the axon (like a wave). - The action potential continues to the pre-synaptic terminals at the end of the axon. - In the thinnest axons, rate is about 1 m/sec - In the thickest axons, rate is about 10 m/sec

How do glucose and amino acids cross the blood-brain barrier?

The membrane has proteins that actively transport glucose and amino acids into the brain.

lateral

Toward the side, away from the midline

When the membrane is at rest, what tends to drive the potassium ions out of the cell? What tends to draw them into the cell?

When the membrane is at rest, the concentration gradient tends to drive potassium ions out of the cell, and the electrical gradient draws them into the cell. The sodium-potassium pump also draws them into the cell.

superior

above another part.

A modified amino acid

acetylcholine

Neuromodulator

aka neuropeptides; several cells are being talked to; synthesized in the cell body and slowly transported to other parts of the cell. They diffuse widely, slowly affecting many neurons in their region of the brain. Kinda resemble hormones in that way. released mainly dendrites, and also by the cell body and by the sides of the axon. requires repeated stimuli effects last 20 minutes or moreimportant for hunger, thirst, and other LT changes in bx and experience.

Electrical synapses (gap junctions)

allow the direct passage of an electrical signal from one cell to the next.

The Action Potential

begins at the axon hillock. A rapid change in the membrane potential of an excitable cell, caused by stimulus-triggered, selective opening and closing of voltage-sensitive gates in sodium and potassium ion channels. Stimulation beyond a certain level crosses the threshold of excitation and produces, massive depolarization of the membrane. rapid depolarization continues to about +30mV and then returns rapidly to its resting potential.

inferior

below another part.

Neurotransmitters

chemical messengers that cross the synaptic gaps between neurons

When the neuron is at rest, what are the two forces that tend to push sodium into the cell?

electrical gradient & concentration gradient.

John eccles

found ESPS and IPSP: Sherrington's student

What do most excitatory inotropic synapses use?

glutamate, the most abundant NT in the brain. ACh is also found here.

What type of potential are EPSP and IPSP?

graded potential

what happens if the depolarization does or does not reach the threshold?

if the depolarization reaches or passes the threshold, the cell produces an action potential. If it is less than threshold, no action potential arises.

Monoamines

includes two subgroups, indolemines and catecholamines.

PNS (peripheral nervous system)

nerves that connect the CNS to the rest of the body. It is made up of two parts.

2 parts of autonomic NS (nervous system) How does the body react to both parts?

pupil during sympathetic response

Autoreceptors

receptor on a presynaptic neuron that responds to the released transmitter by inhibiting further release of it.

Hormone

released into the blood and "talk to everyone"

indolemines

serotonin

Acetylcholinesterase

the enzyme that breaks down acetylcholine in the synaptic cleft.

Vesicles

the presynaptic terminal stores high concentrations of neurotransmitter molecules in vesicles; tiny nearly spherical packets filled with neurotransmitter molecules. The presynaptic terminal also holds much neurotransmitter outside the vesicle. Release of neurotransmitter is always a multiple of a quantum. quantum: minimum amount of neurotransmitter released at one time at a terminal button in vesicles (sacs).

All or none law

the principle that if a single nerve fibre is stimulated, it will always give a maximal response and produce an electrical impulse of a single amplitude. If the intensity or duration of the stimulus is increased, the height of the impulse will remain the same. - the principle that the amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it.

reuptake of neurotransmitters (aka neuropeptides)

the terminal buttons of the presynaptic neuron reabsorb the neurotransmitters - reabsorbation of NT's by the presynaptic terminal. Occurs through special membrane proteins called transporters

Reuptake of neuropeptides

they are not inactivated, they diffuse away.After ACh activates a receptor, the enzyme acetylcholinesterase breaks it down into two fragments: acetate and choline, a recycling process.

What happens to K+ (potassium) gates during IPSP?

they open

What happens to Na+ (sodium) gates during EPSP?

they open

Dorsal

toward the back, away from the ventral (stomach) side. the top of the human brain is dorsal because it has that position in four legged animals.

Anterior

toward the front end

Postieror

toward the rear end.

ventral

toward the stomach, away from the dorsal (back) side.

Rate law

variations in intensity of stimuli are due to variations in the rate at which an axon fires (if more often then more intense).