Intro to Psychology

Neurophysiology, Neuroanatomy

The BrainThe brain is a combination of two types of cells, glial cells and neurons

The brain consists of 100 billion neurons and 1012 total cells

Neurons• Cells in the brain that communicate with

each other

• Neurons are “born” early in life

• Do not regenerate

Glial Cells• Provide support for neurons

– Structure support– Metabolic and nutritional support

• Can replace themselves

• Serve to clean up the brain, removes dead tissue and foreign objects

• Play a large role in neural development

• May even be communicating with neurons

• Role is expanding with new research

Glia and Neurons

Many different types of neurons

Pyramidal neuron Purkinje neuron

Parts of the Neuron

• Neurons communicate in two ways• Electrical signal: within a neuron• Chemical signal: between neurons• Electrical signal is sent from one part of the

neuron to the other: The signal travels from the dendrite through the cell body to the axon– Dendrites receive the signal from another neuron– Axons send the signal to other neurons

• Chemical signal is sent from the axon of one neuron to the dendrite of another neuron

Properties of the Neuron

• Neurons contain many ions and are charged

A- are large protein ions that always stay inside the cell

K+ is potassium. At rest it is mostly inside the cell

Cl- is chloride. It exists both inside and outside the cell

Na+ is sodium. It exists primarily outside the cell

• When the cell is at rest (i.e., not doing anything), it has a charge of -70 mV. This is called the resting potential.

• Because of the cell properties, many forces are acting on the cell.

• 1. Diffusion - substances tend to move from areas of high concentration to areas of low concentration.

• 2. Like charges repel each other and opposite charges attract

• Charges stay the way they are because of the cell membrane. It is selectively permeable. It does this by ion channels.

• Normally the membrane closes Na+ channels

• However, if the membrane is given an electrical charge, it causes the membrane to lose some permeability

• This opens the sodium channels• If this electrical charge is large enough,

the flood gates will open• Change in charge is potentiated down the

length of the neuron• This wave of charge is called the action

potential

Sodium / Potassium Pump• Once sodium has rushed in, the cell

quickly regains its composure

• Active process in which sodium is removed from the cell

• Sodium is exchanged for potassium

• Requires metabolic activity

• Returns charge inside cell to -70 mV

• Refractory period

Communication Between Neurons

• When the action potential reaches the terminal button, it causes a release of chemicals called neurotransmitters

• These neurotransmitters are dumped into the synapse, the space between the axon of one neuron and the dendrite of another

• Neurotransmitters come into contact with membrane of the other neuron

• Receptors on the dendrite detect the neurotransmitter

• NT binds to the receptor• This causes a temporary change in the

membrane, allowing a little sodium inside the cell

• This small charge is called the graded potential

• This is passed on to the axon and it summates

When the sum of the potentials reaches the base of the axon, a sufficient charge may be present to cause an action potential.

• Myelin – a layer of proteins that are wrapped around the axon.

• Two functions: to protect the axon, and to speed up transmission

• Without myelin, neural transmission is inefficient

• Multiple Sclerosis – an autoimmune disorder in which the myelin is destroyed.– Fatigue, pain, motor disorders, cognitive

disorders, etc.

Removal of Neurotransmitter

• After the NT is initially released, the chemical must be removed

• This is done in a couple of different ways– Biochemical breakdown of the NT– Reuptake: NT is pulled back into the

presynaptic button and packaged to be released again

Types of Neurotransmitters

• Excitatory– Glutamate– Acetylcholine

• Inhibitory – What does this mean?– GABA– Norepinephrine

• Both– Dopamine– Serotonin

Effects of Drugs

• Psychopharmacology- the study of how drugs affect behavior

• Nearly all drugs work by affecting neurotransmitter release

Effect of Prozac

Prozac is an example of a SSRI – a selective serotonin reuptake inhibitor

• Alcohol– Activates GABA receptors

• Nicotine– Activates acetylcholine receptors– Changes overall number of ACH receptors

• Cocaine– Blocks reuptake of dopamine– Stimulates release of dopamine– Anesthetic effect on cells

• Amphetamine / Methamphetamine– Similar to cocaine with no anesthetic effect

• Crack – Exactly like cocaine, just more efficient

• Heroin– Activates opiate receptors

• Marijuana– Activates cannabinoid receptors (similar to

opiate)

• Ecstasy (MDMA)– Selectively destroys neurons that release

serotonin– Serotonin is dumped out when the cell dies

Divisions of the Nervous System

• Central Nervous System: Includes Brain and Spinal Cord

• Peripheral Nervous System: All other neural tissue. Specifically, the periphery. This includes muscles, the skin, and even the organs

• PNS broken down into two parts

1. Somatic nervous system: nerve fibers that send sensory information to the central nervous system AND motor nerve fibers that project to skeletal muscle.

2. Autonomic nervous system – Controls the "insides" (the "viscera") of our body, like the heart, stomach and intestines - functions in an involuntary, reflexive manner - does things like constrict blood vessels, dilate pupils, and even makes our heart beat fast on a roller coaster, etc.-Has two components

- A. Sympathetic nervous system: - B. Parasympathetic nervous system

• Sympathetic NS- Regulates “Fight or Flight”– Prepares the body during stressful situations – Increases heart beat, blood pressure, speeds

breathing, slows digestive function

• Parasympathetic NS – Regulates "rest and digest" – Keeps the body running calmly– Shuts down the sympathetic NS when the

situation becomes less stressful

Parts of the CNS• Spinal Cord: Two types of material, white

matter (Axons) and grey matter (cell bodies)

• Spinal cord relays sensory and motor information to and from the brain

• Controls reflexes– Ex. Knee jerk reflex, pain reflex

• Afferent neurons: neurons that send their signal TOWARDS the spinal cord

• Efferent neurons: neurons that send their signal AWAY from the spinal cord

• Reflex involves two neurons, one afferent and one efferent

• Reflexive action takes place before it is sent to the brain

• Allows for extremely efficient processing

Parts of the Brain

• 3 major divisions1. Hindbrain:

Cerebellum; Pons; Medulla

2. Forebrain: Cortex, amygdala, hippocampus, thalamus, hypothalamus

3. Midbrain

Hindbrain

• Cerebellum: Extremely large area, millions of neurons– Responsible for coordination of movement– Plays a role in learning

• Pons– Important for sleep and especially dreaming

• Medulla– Controls all vital functions of the body

including breathing and heart rate

Forebrain• Thalamus

– Primary relay station of the brain– Almost all sensory information passes through

before going elsewhere

• Hypothalamus– Regulates autonomic nervous system– Regulates hormones, “4 F’s”; Feeding,

Fighting, Fleeing, and sexual behavior

• Amygdala– Responsible for many aspects of emotion– Emotional learning

• Hippocampus– Especially important for learning and memory– Resolving conflict

• Cerebral Cortex– Does just about everything– Many think that the cortex is what makes

humans the way they are– Cortex is broken up into 4 lobes:

• Frontal lobe: the front of the brain• Temporal lobe: side, the temples• Parietal lobe: kinda middle portion• Occipital Lobe: very back

• Frontal lobe– Important for planning– Thinking / decision making– Primary motor cortex: Generation of

movement– Broca’s area: Production of Speech

• Temporal lobe– Audition– Wernicke’s area: Language comprehension

• Parietal lobe– Somatosensory function (touch, vibration,

pain)– Combination of all senses with vision

• Occipital lobe– Vision: Primary visual cortex

Two Halves of the Brain• Brain is actually two

different halves. It is split down the middle, with the right and left side being very similar to the other

• The two hemispheres are connected by the corpus callosum: a bunch of axons

• Each side of the brain controls the opposite side of the body. – Ex. Moving right arm controlled by the left side

of the brain.

• Systematic differences in right vs. left.

• Most language and music on the left.– Somewhat different for left-handed people

• The right hemisphere more involved with visual imagery and creativity.

Split-brain Patients• Sometimes the corpus callosum of a

person is cut. It is often surgically cut in patients with severe epilepsy.

• Allows for the study of the role of each hemisphere

• Experiments have found crazy strange results

Studying the Brain with Animals

• Many techniques can be used to study the brain of animals

• Lesioning of the brain– Electrical lesions- electricity is passed through

an electrode until neurons die– Chemical lesions- inject chemicals like acid to

kill neurons

• Injection of drugs

• In Vitro analysis: “In the Lab” – brain tissue is removed, isolated, and studied on its own. Individual neurons can be studied

• In Vivo analysis: “In the Living” – the brain is studied in an intact animal

Studying the Brain of Humans

• EEG: electroencephalogram – electrodes are placed on the scalp. – It records the electrical activity of neurons.– Problem: It records from thousands of

neurons at a time; not very precise

EEG printout

• “CAT” scan: Computerized tomography– Computer enhanced 3-D X-Rays– Not much resolution, still life

• MRI: Magnetic resonance imaging – uses magnetic fields to get brain scans– Just get a picture

• PET scan: Positron Emission Tomography– patients are injected with radioactive glucose.

The scanner tracks where the glucose moves to. This is used as an indicator of neural activity.

- Has problems: very expensive, resolution is fairly low.

• Functional MRI (fMRI) – Registers changes in the metabolism of cells– Get 3-D picture of real time brain activity– Very expensive