Psychology Chapter 4

neurons or nerve cells

they are separated differently to other cells, as tehy communicate with one another through synapses

they are constantly active and motor our internal and external environment, creating mental experiences and control behavior

they work together

central nervous system

made up by brain and spinal cord, they integrate and syntehsize neural information

peripheral nervous system

made up of nerves which relays information to and from the brain to other parts of teh body

neuron

a single cell of teh nervous system

nerve

a bundel of neurons within teh peripheral system

sensory neurons

bundled together to form nerves carrying information form sensory organs into central nervous system

motor neurons

bundled neurons into nerves carrying messages out from central nervous system to operate muscles and glands

interneurons

exist only in central nervous system and carry messages from 1 set of neurons to another

they collect, organize, and integrate messages from various sources

cell body

widest part of a neuron it contains the cell nucleus and other basic machinery common to all bodily cells

dendrites

thin, tube-like extensions which branch and function to receive input to neuron

• motor and sensory neuros; etend directly off teh cell body and branch out to form bushlike structures to increase surface area of cell and increase signal recieving

• sensory; branch out form one axon, expanding into sensory organ and repsonds to signals

axon

thin tube-like etension from cell body which carries messages to other neurons or for motor-neurons to muscle cells

axon terminal

most axons form many branches some distance from teh cell body, and each branch ends with a small swelling called the axon terminal. tehy release chemical transmitter molecules onto neurons or muscle cells

myelin sheath

axons of some neuron are surrounded by a casing, myelin sheath, which is a fatty substance produced by glial cells. it helps to speed up the movement of neuron pulses

action potentials

wave of charge in electrical charge across the axon membrane. Initiated by a chance in structure of cell membrane at one end of axon; thousands of channels open up allowing more NA+ions to move, enough travel inwards causing a temporary postive charge

• motor and interneurons: triggered at the junction between the cell body and the axon, they travel rapidly across the axon to the terminal

• sensory; triggered at the dendritic end of axon and travel through or past the cell body to the terminal

same strength buy varying rates, thus a neuron varies the strength of its effect on neurons or muscle cells

cell membrane

encloses each neuron, a sporus skin. it permits certain chemicals to flow into and out of cell while blocking others

intracellular fluids

in neuron a solution with water and dissolved chemicals

extracellular fluid

outside of neuron solution of water and dissolved chemicals

soluble protein molecules A-

with negative charge in intracellular fluid K+, NA+ and Cl- in extracellular fluid

resting potential

the negative charge inside and positive charge outside creates and electrical charge across membrane, making action potential possible

depolarization phase

the sudden electrical shift of action potential, the channels close na+ but not for K+, creating a temporary postive charge inside

repolarization phase

the channels close na+ but not for K+ however due to temporary chance the K+ are repelled by positive charge inside and thus pushed outwards, returning to normal charge

sodium potassium pump

each membrane has one that moves sodium out and potassium in

cells threshold

sodium channels open in response to depolarizations when equal to the same critical value

speed of action potential

influenced by the large diameter, less resistance thus increases speed. also influenced by the myelin sheath, the thicker the better the rate which neuron pulses can be sent increases

myelination

process of developing myelin begins before birth but not done until into adulthood, neurons in sensory system do it first then motor nerves

synapse

the junction between each axon terminal and the cell body or dendrite or receiving neuron

neurotransmitter

when an action potential reaches an axon terminal it causes the terminal to release a packets of a chemical substances, they move across the space between cells and alter the receiving neurons which influence its production of action potentials, increasing or decreasing the likelihood of a neuron to fire

parkinson’s

muscle tremors and severe difficulty in initiating and coordinating movements caused by degeneration of dopamine-producing neurons whose axons originate and terminate in specific brain areas

synaptic cleft

seperates the axon terminal from the membrane of the cell that it influences

presynaptic membrane

the membrane of the axon terminal that faces the cleft

postsynaptic cleft

the cell on the other side of the cleft

vesicles

a small fluid-filled bladder in the body, each contain several thousand molecules of chemical neurotransmitters

dopamine

infleunce’s movement and motivated behavior, high levels = schizophrenia, low levels = parkinsons

acetylcholine

released at neuromuscular junction associated with the activation of muscles within brain, alter the way other brain structures process information

neuromodulator

alter the way other brain structures process information

serontonin

influence sleep and mood

GABA

gamma-aminobutyric acid, slows or weakens neuron signals anxiety

How do neurotransmitter molecules move across the synaptic cleft?

They diffuse through the fluid in the cleft.

What happens when neurotransmitter molecules reach the postsynaptic membrane?

They attach to special receptors on the postsynaptic membrane. Opening ion channel, allowing ions to pass through.

What effect does ion flow have on a muscle cell?

It triggers a biochemical process that causes the muscle cell to contract.

What effect does ion flow have on a postsynaptic neuron?

It changes the polarization of the neuron,

excitatory synapse

the trasmmitter opens ino channells for NA+ in postsynaptic membrane, causing depolarizatoin of receiving neuron, more positive which increases rate of action potentials

inhibitory synapse

transmitter opens fro CL- and K+ causing hyperpolarization, more negative, drcreaisng rate of action potentails

neruogensis

process of creating new neurons for the first 2 weeks after conception

differentation

last stage of neuron development , they grow in size and increase number of dendrites and axon terminal and number of synapses formed

selective cell death/ apoptosis

neurons die =, so do synapses not not this process, which begins before birth and continuous into teen years

mirror neurons

organized systems of neurons that are designed to faster social learning, help us behave in ways that mirror what we observe. They are important in imitative learning, where the specific behaviors a model performs are as important as the goal the model attains.

They may allow you to understand another’s intentions, which is important for social cognition

Methods to identify the functions of the brain

1. observing behavioral deficits that occur when a part of the brain is destroyed or is temporarily inactivated

2. observing behavioral effects of artificially stimulating specific parts of the brain

3. recording changes in neural activity that occur in specific parts of the brain when a person or animal is engaged in a particular mental or behavioral task

Electroencephalography (EEG)

Analyzing Electrical Brain Activity

Recording of the electrical activity of the cortex using multiple scalp electrodes.

Event-Related Potentials (ERPs)

Analyzing Electrical Brain Activity

An encephalographic measure of local changes in the brain electrical activity in response to specific stimuli.

Magnetoencephalography (MEG)

Analyzing Electrical Brain Activity

Detects the magnetic field changes produced by the cortical electrical activity.

Transcranial Magnetic Stimulation (TMS)

Analyzing Electrical Brain Activity

The localization of a brain function by temporarily blocking the electrical activity of an area by exposure to a magnetic field.

TMS uses magnetic pulses from a coil placed on the scalp to temporarily disrupt neuronal activity, mimicking a reversible brain lesion. It’s used to map functions of the cerebral cortex.

TMS can be used to show the functional connections between specific areas within movement-control portions of the cerebral cortex and the muscles controlled by those areas.

Transcranial Direct Current Stimulation (tDCS)

Analyzing Electrical Brain Activity

The localization of brain function by temporarily stimulating electrical activity directing weak electrical currents to specific areas of the brain.

it has been found to alter perceptual, cognitive, and motor functioning. tDCS has also been effective in alleviating some brain disorders

Magnetic Resonance Imaging (MRI)

Analyzing Anatomical Structure

High-resolution image of brain anatomy measuring energy changes of brain tissue after an exposure to a strong magnetic field.

Diffusion Tension Imaging (DTI)

Analyzing Anatomical Structure

Measures the diffusion of water in the brain tissue, permitting the imaging of the white matter tracts.

Positron Emission Tomography (PET)

Analyzing Functional Metabolic Activity

Assesses the metabolic activity of glucose or oxygen in the brain by following the path of a radioactive tracer injected intravenously.

Functional Magnetic Resonance Imaging (fMRI)

Analyzing Functional Metabolic Activity

Assesses indirectly the metabolic activity of the brain through measuring the changes of the blood flow.

flexion reflex

contraction of flexor muscles, which bend limb at each joint, causing it to be pulled toward the body

it occurs fast as it doe snot require the brain

examples of TMS

Sara Torriero, 2007

interested in neural foundation of observeable learning; learning form watching others 

• one group of students received TMS on dorsolated prefrontal cortec, right before watching someone solve. aproblem and were unable to have observable learning 

electroencephalogram, EEE

used as an index wheter a person is aurosed, relax, or asleep 

even related potential, ERP

brief change in EEE after stimulus, comparing average ERP with different scalp locations, reveals a pattern of activty in brain as person responds so stimulus

activation of the brain

blood vessels enlarge so more blood enters, whcih carry oxygen and glucose, supplying enough energy sources to increase neural atcivty

postron emission topography

1st neuroimaging method in 1970, enjecting radioactive substance into blood, measuing the radioactivty that is emitted from each part of the brain

functional magnetic resoure imaging fMRI

1990, creating magnetic field around teh person’s head, causing hemoglobin molecules that carry oxygen in teh blood to give off radio waves of a certain frequency 

\these are then detected to asses teh amount of blood in each part of the brain

lesions

areas fo damage in brain

producing lesion electrically

thin wire electrode, insulted everywhere except for teh top, is surgically inserted in brain and currents ent through to destroy neurons next to tip 

helps to identify different brain nuclei which are crucial for basic motivational and emotional states

producing lesion chemically

thin tube, cannula, inserted in brain and small amount of chemical injected to destory neurons whose cell bodies are close to it 

helps to identify different brain nuclei which are crucial for basic motivational and emotional states

electrical stimulation

thin wire electrode has a weaker current than for lesions, but it produces action potentials

it is activated through radio waves

exhibit drive and emotional states

chemical stimulation

a cannula placed permantely and before behavioral testing, a tiny amount of a neurotransmitter substance or other chemical activates neurons 

exhibit drive and emotional states

sensory-perceptual hierarchy

involved in data-processing receiving sensory data about internal and external environment, it analyses for the bodily needs 

bottom= sensory receptors 

top = perceptual centres in brain

motor-control hierarchy

involved with teh control of movement

top= executive centres making decisions about the activity the person should engage in, what muslce to use

bottom= translate those decisions into patterns of muscle movements

nerve classes

1. cranial nerves: proect directly from brain 

2. spinal nerves: project diretcly from psinal cord

roles and patterns of action potentials

the action potentials from teh sensory neurons are the data that perceptial areas of central nervous system use to understand teh internal and external state

somatosensation

sensation conveyed by physical sensation, pain etc

skeletal muscles

muscles that are attahced to bones and produce externally observed movement of body, when contracted 

make up somatic, body, part of peripheral motor system 

they initiate activity 

visceral muslces and glands

muslces attached to bones and dont move skeletal when contracting 

glands structures that produce secretion such as salivary glands or sweat glands 

they make up autonomic portion of peripheral motor system 

they modulate not inititate 

sympathetic diviison of autonomic system

responds to stressful stimulation and helps prepare body for ‘fight ro flight’ situation

increase in heart rate and blood pressure, higher energy, increase blood flow, and inhibition fo digestion processes

parasympathteic divions of autonomic system

serves regenerative, energy conserving functions, with opposite effects of sympathetic division

ascending tracts

in spinal cord which carry somatosensation information through spinal nerves to brain

descending tracts

carry motor control commands from brain through spinal cord to muscles