Chapter 1: Nerve Cells and Nerve Impulses

Aristotle viewpoint

thought the heart was the location of intelligence and thought

Ancient Egyptian viewpoint

thought brain was useless; scooped out brain through nostrils

Rene Descartes

Dualist

Dualism

mind and brain are two different entities

Monism

mind and brain are one

Basic Science

builds on the knowledge base of science, use of animals

Applied Science

applies knowledge from basic science

Santiago Ramon y Cajal

one of the main founders of neuroscience; nerve cells remain separate instead of merging into one another

Neurons

receive and transmit info to other cells

Glia

cells in the nervous system that support, nourish, and protect neurons

Membrane

thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ, semi-permeable

Nucleus

Control center of the cell

Mitochondria

Powerhouse of the cell, organelle that is the site of ATP (energy) production

Ribosomes

the sites within a cell that synthesize new protein molecules

Endoplasmic Reticulum

a network of thin tubes that transport newly synthesized proteins to other locations

Dendrites

Branchlike parts of a neuron that are specialized to receive information.

Cell body (soma)

contains the nucleus and other parts of the cell needed to sustain its life

Dendritic spines

short outgrowths that increase the surface area available for synapses

Motor Neuron

a neuron that sends an impulse to a muscle or gland, causing the muscle or gland to react

Sensory Neuron

neurons that carry incoming information from the sensory receptors to the brain and spinal cord

Axon

sends information from cell body to axon terminals

Myelin sheath

speeds up signal down axon

Guillain-Barre Syndrome

myelin dysfunction, weakness, numbness

Node of Ranvier

A gap between successive segments of the myelin sheath where the axon membrane is exposed; actions potentials occur here

Presynaptic terminal

(end bulb or bouton) point where an axon releases chemicals

Afferent axon

brings information into a structure

Efferent axon

carries information away from a structure

Interneuron

a neuron that carries nerve impulses from one neuron to another

Astrocytes

-Star shaped glia

-bundle and synchronize neurons in the area

-provides nutrients to the neurons from blood

-removes waste, dead neurons, etc. ("Phagocytosis")

Microglia

act as part of the immune system, removing viruses and fungi from the brain

Oligondendrocytes

in the brain and spinal cord; build the myelin sheath that surround and insulate certain vertebrate axons; also supply axon with nutrients to function properly

Schwann cells

in the periphery of the body build the myelin sheath that surround and insulate certain vertebrate axons, also supply axon with nutrients to function properly

Radial glia

guide the migration of neurons and their axons and dendrites during embryonic development

Blood-Brain Barrier

Blood vessels (capillaries) that selectively let certain substances enter the brain tissue and keep other substances out

What can cross the BBB?

small molecules, CO2, O2, lipid soluble molecules

Area Postrema

a region of the medulla where the blood-brain barrier is weak; poisons can be detected there and can initiate vomiting (bad food/drink make you throw up; emesis reflex center)

Resting potential of neuron

voltage of neurons -70mV

Hyperpolarization

increase in the negative charge inside the neuron...(more polarized)

Depolarization

Decrease in the negative charge inside the neuron...(less polarized); rapid depolarization continues to +40mV then returns to resting potential

The All-or-none law

neurons either fire or they don't at just one strength (gun, toilet)

Refractory period

can't fire another action potential (like a toilet and a gun...need time for it to reset before you fire it again)

Absolute refractory

neuron incapable of firing

relative refractory

has to have strong stimulus to fire

Glucose

a sugar that is the only nutrient that crosses the BBB in large quantities

Thiamine

vitamin B; to use glucose the body needs thiamine

Electrical gradient

inside is negatively charged; makes the positively charged sodium attract to the inside of the neuron (pos. Attract to negative); it's usually blocked

Concentration gradient

things move from greater concentration to lesser concentration, sodium ion favorable to rush into the cell

Sodium-Potassium Pump

constantly pumping potassium back into the cell and sodium out of the cell; has to normalize things

Nodes of Ranvier

short unmyelinated sections of axon where the AP travels slow; the myelin speeds it up; neurons refire here too

Action potentials

messages sent by axons

Threshold

the level of stimulation required to trigger an AP; the membrane opens its sodium channels and lets sodium ions flow into the cell; the potential shoots up far beyond the strength that the stimulus provided

A-alpha nerve fibers

the sense of body awareness that allows you to perceive your body's position in space (e.g., know where your body is even when it's under a blanket)

Biggest, thicket neurons in your body

A-beta nerve fibers

sensation of touch

A-delta nerve fibers

light pain and temperature

C-nerve fibers

dull deep pain, extreme temperature, itch

Lidocaine/Novocain

Attach to the Na+ channel and all the nerve fibers, specifically in your mouth or wherever it's given; can't feel it because sodium channels are blocked which stop AP

General anesthesia

Open K+ gates in central nervous system;

Sodium rushes in, potassium rushes out so the neurons can't fire; can't reach threshold

Voltage-gated channels

the axon channels regulating sodium and potassium

Propagation of the Action Potential

describes the transmission of an action potential down an axon

Saltatory conducting

the jumping of AP from node to node on an axon

Local neurons

neurons without an axon

Grade potential

when a local neuron receives information from other neurons, a membrane potential that varies in magnitude in proportion to the intensity of the stimulus

The Action Potential (molecular basis)

1. With a slight depolarization, Na+ channels open slightly

2. Threshold reached, Na+ channels open (fires)

3. K+ channels begin to open, Na+ channels begin to close

4. At peak, Na+ channels close. K+ channels wide open, K+ flows out

5. K+ channels begin to close

6. Cell hyperpolarizes (refractory period)

7. Ready to fire again

NOTE: Na+ depolarizes, K+ brings back to resting

Behavioral neuroscience

an approach to psychology that links psychological processes to activities in the nervous system and other bodily processes

Cognitive neuroscience

the interdisciplinary study of the brain activity linked with cognition (including perception, thinking, memory, and language)

Clinical Neuropsychology

unites the areas of neuroscience and clinical psychology, focuses on the origin of psychological disorders in biological factors

Goals of biopsych

1. Generalization

2. Reductionism