Studying the brain and Neurons Chapter 2

III. A Phineas Gage Level headed, calm foreman of a railroad crew (1848). An accident caused a tamping iron to go through his head. (One of the next slides shows the path) The injury severed the connections between his limbic system and frontal cortex. He survived

III. A – cont… This caused his personality to totally change- he became volatile This injury allowed us to understand the brain before technology was available. ( I will show you a video next week about him.)

Phineas Gage

III. B. Paul Broca Performed an autopsy on the brain of a patient known as Tan (because that is all he could say) There was no physical reason for his lack of speech. Broca found an area in the brain that showed deterioration in the frontal lobe of the left cerebral hemisphere Now called Broca’s area- damage to this area cause expressive aphasia (meaning person can’t talk- think about stroke victims)

IV. Producing lesions To lesion means to damage part of the brain. Sometimes they have to surgically remove brain tissue or sever a brain connection to help a person. This has allowed doctors to study brain function.

VII- EEG Allows us to study the brain’s electrical activity via electrodes placed on the scalp. Used to study the brain during different states of arousal (sleep studies use them) It also can be used to detect abnormalities. The next two slides show an EEG- the 2nd one is one they are using on a young child to detect a hearing impairment.

"An electroencephalograph providing amplified tracings of waves of electrical activity in the brain Here it is detecting brain response to sound, making possible an early evaluation of what may be a hearing impairment. "

VIII. A. CAT SCANS 2. Procedure… of a contrast dye. 1. Creates a …. That shows a two dimensional view of the brain. 2. Procedure… of a contrast dye. CAT SCANS show the structure of the brain. Next slide shows a CAT scan of someone with Broca’s Aphasia

Figure 7.14 (A) A horizontal computerized tomography (CT) scan of a subject who presented with Broca's aphasia. The dark region at the left anterior is the location of the lesion. (B) A schematic representation of the horizontal section, with the area of the lesion shown in black. (C) A reconstruction of the brain, showing a lateral view of the left hemisphere with the lesion shown in black. (After H. Damasio and A. R. Damasio, Lesion Analysis in Neuropsychology. New York: Oxford University Press, 1989, p. 56.)

B. MRI Ignore the start of your notes and write this It uses the spin of hydrogen in water cells to read the brain (or body part) It produces more detailed images then Xrays or CAT Scans Useless information here… But if you have a pacemaker you can’t have a MRI (THINK BIG MAGNET!!)

MRI The machine used to obtain magnetic resonance images. The subject is placed in a long metal cylinder that has two sets of magnetic coils arranged at right angles to each other. An additional coil, known as a radio frequency coil, surrounds the head (not shown) and is designed to perturb the the static magnetic fields to produce the MRI.

2. fMRI Shows more detailed information than PET scans. (This isn’t so important to know)

Figure 5.11 Functional magnetic resonance imaging (fMRI) When the subject is in the scanner, the researchers will be able to communicate with him using an intercom system and a visual projection system. The image of the brain depicts, with colors of the rainbow, the amount of blood flow in each part of the brain, which indicates the amount of neural activity in each part.

How to tell a liar- MRI- ignore this I will talk about it next week Researcher Dan Langleben says two areas of the brain exhibit increased neuron acivity when a person tells even the simplest of lies. When viewing the brain with an MRI scanner, the increased activity appears as bright spots in the premotor cortex on the left side and the anterior cingulate gyrus located near the middle. The world is becoming a trickier place for people who tell lies _ even little white ones. From thermal-imaging cameras designed to read guilty eyes to brain-wave scanners that essentiallywatch a lie in motion, the technology of truth-seeking is leaping forward.

C. PET Scans A radioactive isotope is injected into the person. This allows the machine to study glucose and oxygen changes in an area of the brain. This has allowed us to study the functioning of the brain. A PET scan is used in many studies about what part of the brain is active when you read, talk, lie, think about specific subjects- the possibilities are endless!

Pet scan

Comparison

I. The neuron receives or sends messages. 2 3. 1. 4.

B. Neurotransmitters We need them because there is a space at the end of the axon (called synaptic cleft or synapse) and the message has to get to the next neuron. 1. Acetylcholine- causes contraction of skeletal muscles. Interference and/or depletion of ACh is associated with Alzheimer’s disease.

3. GABA Inhibits the firing of neurons. Valium and anticonvulsant drugs increase GABA and thus slows the firing of neurons

4. Dopamine Influences learning, movement, emotion and attention. Lack of relates to Parkinson’s Excess relates to Schizophrenia

5. Serotonin Affects mood, hunger, sleep and arousal. Undersupply relates to depression

6. Endorphins They make us happy (to Quote Legally Blonde) They are the brain’s own pain killers Narcotics such as heroin replace them- why withdrawal is so painful

Add in Norepinephrine The neurotransmitter = of adrenalin Controls alertness and arousal Undersupply related to depression END HERE!!!!

The neuron at rest is more negative inside the cell membrane relative to outside the membrane. The resting neural membrane potential is about -70mV. The resting potential results from selective permeability of the membrane, the presence of electrically charged particles called ions near the inside and outside surfaces of the membrane and resulting concentration and electrical gradients.

Resting potential Illustrated here is a portion of a neuron¡¯s cell membrane with ions dissolved on each side. Negatively charged protein molecules (A-) exist only inside the cell. Potassium ions (K+) exist mostly inside the cell. Sodium ions (Na+) and chloride ions (Cl-) exist mostly outside the cell. Because channels in the membrane that are permeable to potassium remain open, some potassium ions diffuse out, resulting in a surplus of positive charges outside the cell and a deficit of positive charges inside. For this reason, the resting membrane has an electrical charge across it of about 70 mV, with the inside negative compared to the outside. (Adapted from Koester, 1991.)

When sufficiently stimulated (to threshold) a net flow of sodium ions into the cell occurs (along with a movement of potassium ions out). Polarity is reversed to +40mV called the action potential.

Shown here are the changes that occur at a given portion of the axon (indicated as a blue rectangle) as an action potential (indicated as an orange spot) passes through on its way from the neuron¡¯s cell body to its axon terminals. (a) During the resting state, this portion of the axon is electrically polarized such that it has a charge of about -70 mV inside compared with outside, as described in Figure 5.20. (b) The approaching action potential triggers sodium channels to open, which allows Na+ to pass into the axon, causing a depolarization, which itself is the first phase (depolarization phase) of the action potential. The influx of sodium ions causes the axon to lose its electrical polarity and, at the peak, to slightly reverse its polarity such that the inside becomes slightly positive compared with the outside (by about +30 mV). (c) The action potential continues to move through this portion of the axon by triggering sodium channels to open ahead of it. In the wake of the action potential, potassium channels open, which allows K+ to move out of the axon, restoring the membrane potential to its original value; this is the repolarization phase of the action potential.

Glial cells Figure 2.1 Glial Cells. Glial cells vastly outnumber neurons in the brain. They provide support and nutrition for the neuron. One type of glial cell, shown here, provides a connection between neurons and blood vessels in the brain. Another type of glial cell produces the myelin sheath that surrounds some neuron axons.

(D) A high-power light-microscopic view of the cell body, illustrating the nucleus and the nucleolus. Note that the different stains highlight different aspects of the neuron.

Figure 5.6 Axon terminals This electron micrograph shows the terminals of many axons forming synapses on a portion of the cell body of a single neuron. Synaptic vesicles, filled with neurotransmitter molecules, reside within the button-like swelling of each axon terminal. In the central nervous system, the cell bodies and dendrites of motor neurons and some interneurons are blanketed with thousands of such terminals.

Electromicroscopic photo of clusters of neurons in the visual cortex of the brain

A synapse = A particular terminal button of an axon The synaptic cleft The receiving portion of another neuron, gland cell or muscle cell

Figure 3.05 A. Photomicrograph of a synapse in action taken with the electron microscope. Vesicles are releasing their transmitter chemical into the synaptic cleft. B. Schematic of the process.

(C) An electron micrographic image of the contacts between an axon from another neuron and a dendrite, illustrating the synapse formed by the opposition of the end foot of the axon and the dendritic spine of the dendrite.

FIGURE 2.2 The Parts of a Typical Neuron The drawing shows the location and function of key parts of a neuron. The photograph, made with the aid of an electron microscope, reveals actual cell bodies, dendrites, and axons in a cluster of neurons. The green coloring was added to provide contrast in the photograph to make the neurons more visible.