Intro to Psychology Neurophysiology, Neuroanatomy
The Brain The 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
Many different types of neurons Pyramidal neuron Purkinje 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 • Somatic nervous system: nerve fibers that send sensory information to the central nervous system AND motor nerve fibers that project to skeletal muscle.
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 divisions • Hindbrain: Cerebellum; Pons; Medulla • Forebrain: Cortex, amygdala, hippocampus, thalamus, hypothalamus • 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