Chapter 2 Neuroscience

A Little Exercise See in class!

Brain and Mind

Topics to Explore The Neuron The Peripheral Nervous System The Central Nervous System

Part 1 The Neuron

Neuron and Its Parts Neuron: Individual nerve cell; 100 billion in brain Dendrites: Receive messages from other neurons; have thousands of branches Soma: Cell body; metabolic center of neuron; contains genetic material Axon: Carries information away from the cell body; longest part of neuron Axon Terminals: Branches that link the dendrites and soma of other neurons Synaptic Gap: Space between the end of the axon of one neuron and the dendrites of an adjacent neuron

Picture of a Neuron

The Nerve Impulse Resting Potential: Electrical charge of an inactive neuron Threshold: Trigger point for a neuron’s firing Action Potential: Nerve impulse

Resting Potential Resting Potential: Tiny charge between inside & outside of neuron Created by electrically charged particles (ions) Some concentrated outside the cell (sodium and chloride ions) Some concentrated inside the cell (Potassium ions) How is the charge maintained? Sodium-potassium pump Selectively permeable cell membrane

Action Potential Action potential: Change in potential, primarily because of messages from other neurons Excitatory messages: Cell loses the negative charge; Depolarization Inhibitory messages: Cell becomes more negatively charged; Hyperpolarization

Resting vs. Action Potential

Graphic: Action Potential

Graphic: Action Potential

Graphic: Synaptic Gap

Neurotransmitters Neurotransmitters: Chemicals that alter activity in neurons; brain chemicals. Messages from one neuron to another pass over the synapse, the microscopic gap between neurons Receptor Site: Areas on the surface of neurons and other cells that are sensitive to neurotransmitters Antagonist: drug that decreases activity of a neurotrans-mitter

Some Neurotransmitters Acetylcholine: involved in learning, memory, and muscle contractions. Botulism toxin prevents release of acetylcholine, resulting in paralysis Dopamine: involved in arousal, mood, and movement. In Parkinson’s, receptors in brain fail to react to dopamine, leading to tremors, rigidity and problems initiating movement Serotonin and Norepinephrine: involved in arousal and mood. Cocaine blocks re-uptake of both neurotransmitters, resulting in “high” GABA (gamma-aminobutyric acid): main inhibitory neurotrans-mitter; lowers arousal and anxiety Endorphins: lower pain perception. Morphine and heroin bind to endorphin receptors, increasing endorphin activity.

Nerves and Neurons Nerves: Large bundles of neurons Myelin: Fatty layer of tissue that coats axons Multiple Sclerosis (MS) occurs when myelin layer is destroyed; numbness, weakness, and paralysis occur

Demonstration of the speed of a neural impulse. A Little Exercise Demonstration of the speed of a neural impulse.

An Organizational Pause: Organization of the Nervous System

Major Sections of the Nervous System Central Nervous System (CNS): Brain and spinal cord Peripheral Nervous System: All parts of the nervous system outside of the brain and spinal cord - Autonomic System: Serves internal organs and glands; controls automatic functions such as heart rate and blood pressure - Somatic System: Links spinal cord with skeletal muscles and sense organs; controls voluntary behavior

Organization of Nervous System

Graphic: Nervous System

Part 2 The Peripheral Nervous System The Autonomic Nervous System The Somatic Nervous System

Divisions of Autonomic System Sympathetic: Arouses body; emergency system Parasympathetic: Quiets body; most active after an emotional event

Functions of Autonomic Nervous System

Three Components of Emotion Physical component: state of physiological arousal triggered by autonomic nervous system Behavioral component: outward expression of the emotion, including facial expression & behavior Cognitive component: appraisal of the situation to determine which emotion we are experiencing and why

James-Lange Theory of Emotion

Cannon-Bard Theory of Emotion

Schachter-Singer Theory

Comparison of Three Theories of Emotion

Somatic Nervous System Motor Nervous System: transfers messages from CNS to control function of voluntary muscles Sensory Nervous System: transfers messages from sensory organs to CNS; brings information from outside the body to the brain to be processed

Structures in Somatic System Sensory neuron: neuron that transmits information from sensory organ to CNS Motor neuron: neuron that transmits information from CNS to voluntary muscle Connector neuron: neuron in spinal cord connecting sensory and motor neurons to form reflex arc. Reflex: An innate, automatic motor response to a specific sensory stimulus

Graphic: Somatic Nervous System

Motor & Somatosensory Areas in Cerebral Cortex

Motor Homunculus “homunculus” = “a diminutive human being”

Somesthetic Homunculus

A Little Exercise A demonstration of the somatosensory system, using toothpicks and little rulers.

Part 3 The Central Nervous System The Spinal Cord The Brain - The Central Core - The Limbic System - The Cerebral Cortex

The Spinal Cord Spinal Nerves: 31 of them; carry sensory and motor messages to and from the spinal cord Cranial Nerves: 12 pairs that leave the brain directly; also work to communicate messages Spinal cord functions to connect peripheral nervous system to the brain

The Central Core (aka the “old brain”) Medulla: Connects brain with the spinal cord and controls vital life functions such as heart rate and breathing Cerebellum: Regulates posture, muscle tone, muscular coordination, and procedural learning Reticular formation: Associated with levels of arousal and consciousness, as well as some reflexes (breathing, coughing, sneezing, vomiting) Thalamus: serves as a relay station for incoming sensory Information Basal ganglia: involved in physical movement

Graphic: Central Core

The Limbic System At the top border (limbus in Latin) of the brain stem. Hypothalamus: controls pituitary gland (directing activity of endocrine system) and autonomic nervous system; involved in basic drives (eating, drinking, sex) Hippocampus: involved in formation of memories Amygdala: involved in regulating emotional experiences, particularly initial emotional responses

Graphic: Limbic System

Neocortex Cerebral Cortex: Outer layer of the cerebrum Cerebrum: Two large hemispheres that cover upper part of the brain Corticalization: Increase in size and wrinkling of the cortex Cerebral Hemispheres: Right and left halves of the cerebrum Corpus Callosum: Bundle of fibers connecting cerebral hemispheres

Graphic: Relative Size

Graphic: Corpus Callosum

Left & Right Hemispheres

Left Brain/Right Brain About 95 percent of our left brain is used for language Left hemisphere better at math, judging time and rhythm, and coordinating order of complex movements Processes information sequentially Right hemisphere good at perceptual skills, and at expressing and detecting other’s emotions Processes information simultaneously

Graphic: Left vs. Right

Lobes of the Neocortex Occipital Lobe: Back of brain; vision center Parietal Lobe: Just above occipital; bodily sensations such as touch, pain, and temperature (somatosensory area) Temporal Lobe: Each side of the brain; auditory and language centers Frontal Lobe: Movement, sense of smell, higher mental functions; contains motor cortex; controls motor movement

Graphic: Lobes