Chapter 2 Neuroscience and Behavior

The Neuron Communication in the Nervous System takes place in the neurons Cells that are specialized to receive and transmit info (nerve cell) Cells that are specialized to receive and transmit info (nerve cell) Neuroscience: the study of the Nervous System Neuroscience: the study of the Nervous System Glial Cells: support cells that provide structural support, nutrition, and discard waste for neurons. Also produce myelin. Glial Cells: support cells that provide structural support, nutrition, and discard waste for neurons. Also produce myelin.

Types of neurons Sensory Neurons: transmit info from receptor cells in sensory organs (i.e. nose, ears, tongue, eyes, and skin) and internal organs to brain. Motor Neurons: Transmit info from the brain to muscles. Interneurons: Communicate between sensory and motor neurons.

Structures of the Neuron Cell Body: contains structures that provide energy for the cell to function. Also contains the nucleus. Dendrites: Receive messages from other neurons

Structures of the Neuron con’t Axon: Carries info to other neurons. Myelin Sheath: Protects axon from axons of other neurons. Formed by glial cells

Structures of the Neuron con’t Axons vary in size. Axons may have branches that allow it to communicate with more than one neuron. Gaps in the Myelin Sheath called Nodes of Ranvier or just nodes Neurons with Myelin Sheath communicate faster Multiple Sclerosis is the degeneration of the Myelin Sheath.

Communication Within the Neuron Messages are gathered by the Dendrites and passed along the Axon by a small electrical impulse called Action Potential. Stimulus Threshold: The minimum level of Stimulation required for a neuron to activate. While waiting, a neuron is polarized. Interior is more negatively charged than exterior. Resting charge is -70 millivolts, referred to as resting potential. Action Potential is All-or-None

Communication Within the Neuron con’t While resting, a neuron has sodium ions on the exterior of the membrane. In the interior, the neuron contains potassium ions. When the action potential is sent down the axon, channels open and the two ions briefly switch, creating a charge of +30 millivolts. This is depolarization. Refractory Period: Period the neuron is unable to fire. During this period the neuron repolarizes.

Communication Between Neurons Primary function of a neuron is to communicate information to other cells. 2 Types of Communication: Electrical and Chemical Synapse: Point of communication between two neurons. Presynaptic neuron: Neuron sending the message Presynaptic neuron: Neuron sending the message Postsynaptic neuron: Neuron receiving the message Postsynaptic neuron: Neuron receiving the message Synaptic Gap: Fluid filled space separating neurons. Synaptic Gap: Fluid filled space separating neurons. Axon Terminal: Located at the end of the axon. Where the message is sent from one neuron to the next. Axon Terminal: Located at the end of the axon. Where the message is sent from one neuron to the next.

Electrical Communication Synapse extremely narrow Ion Channels serve as a bridge between neurons Communication is instananeous

Chemical Communication: Synaptic Transmission When message reaches the axon terminal, synaptic vesicles dock with membrane and release chemical messengers called neurotransmitters. Neurotransmitters cross the synaptic gap and attach to receptor sites on the dendrites of postsynaptic neurons. Neurotransmitters must fit receptor sites exactly. Reuptake: Process of neurotransmitters being reabsorbed by presynaptic neuron. Those not reabsorbed are dissolved by enzymes. Synaptic Transmission

Types of messages Neurotransmitter gives one of two messages. Message depends on the receptor it attaches to. Excitatory message: increases the likelihood that the postsynaptic neuron will activate action potential. Inhibitory message: decreases the likelihood that the postsynaptic neuron will activate action potential.

Neurotransmitters and their effects

Acetylcholine 1 st neurotransmitter discovered Found in all motor neurons; stimulates muscles to contract Also found in brain; essential to memory, learning, and general intellectual functioning. Alzheimer’s Disease linked to a depletion of Acetylcholine

Dopamine Involved in movement, attention, learning, and pleasurable or rewarding sensations. Addictiveness of some drugs related to dopamine increasing properties. (i.e. cocaine, nicotine) Degeneration in brain linked to Parkinson’s Disease. Symptoms include rigidity, muscles tremors, poor balance. Excessive levels linked to hallucinations and Schizophrenia.

The Brain: Studying the brain Case Studies: Monitoring behavior of people with damage or disease. Limited Lesions: Removing or damaging a part of the brain. Bipolar electrodes: Surgically implanted wires or disks that stimulate areas of the brain Electroencephalogram: Records the electrical activity of the brain from millisecond to millisecond. Recorded on an EEG.

Brain Structures: Brainstem Brainstem: Includes the hindbrain and mid brain. Hindbrain connects the Spinal Cord with the rest of the brain Made up of 3 structures: Medulla: Controls breathing, heart rate, etc Medulla: Controls breathing, heart rate, etc Pons: Relays info from forebrain to cerebellum Pons: Relays info from forebrain to cerebellum Cerebellum: Controls balance & coordination Cerebellum: Controls balance & coordination Reticular Formation: Group of neurons in medulla that project up the brain and down Spinal Cord. Reticular Formation: Group of neurons in medulla that project up the brain and down Spinal Cord.

Brain Structures: Brainstem con’t Midbrain: Processes auditory and visual information. Substantia Nigra: Involved in motor control and contains a large concentration of dopamine-producing neurons. Brain Stem

Brain Structures: Forebrain Also called cerebrum; makes up 90% of brain. Outer portion called Cerebral Cortex. Divided into 2 cerebral hemispheres that are connected by the corpus callosum. Each Hemisphere has 4 Lobes: Temporal, Occipital, Parietal, and Frontal.

Brain Structures: Forebrain con’t Temporal Lobe: Primary Auditory Cortex Occipital Lobe: Primary Visual Cortex Parietal Lobe: Somatosensory Cortex- processes bodily info (i.e. touch, temp. pressure) Frontal Lobe: Involved in planning, initiating, and executing voluntary movements. Forebrain

The Brain: The Limbic System Form complex neural circuits that play critical roles in learning, memory and emotional control. 4 Key Structures: Hippocampus Hippocampus Thalamus Thalamus Hypothalamus Hypothalamus Amygdala Amygdala

The Brain: The Limbic System con’t Hippocampus: Involved in forming new memories. Neurogenesis takes place. Thalamus: Processes and distributes sensory and motor info to and from cerebral cortex. Regulates awareness, attention, and motivation Hypothalamus: Regulates both divisions of the Autonomic Nervous System. Amygdala: involved in a variety of emotional responses: fear, anger, and disgust. Limbic System Human Brain

Specialization of the Hemispheres Cerebral hemispheres work together but have different responsibilities. Lateralization of Function: The idea that different hemispheres exert more control over the other in specific functions. Cortical Localization: The idea that particular areas of the brain are associated with particular functions Cortical Localization: The idea that particular areas of the brain are associated with particular functions

Specialization of the Hemispheres con’t Broca’s Area: Lower left frontal lobe- responsible for speech. Wernicke’s Area: Left Temporal Lobe- responsible for language comprehension Aphasia- Partial or complete inability to articulate ideas or understand spoken or written language as a result of brain damage.

Cutting the Corpus Callosum Done to reduce severity of or eliminate epileptic seizures. Roger Sperry’s experiment shows that the procedure eliminates communication between to hemispheres. (P.74) Left Hemisphere superior in language abilities, speech, reading, and writing. Right Hemisphere dominate in nonverbal emotional expression and visual-spacial tasks. Creative.

Plasticity Functional Plasticity: Brain’s ability to shift functions from damaged areas of the brain to undamaged areas. Structural Plasticity: Idea that the brain’s structure is sculpted by experience.

Brain Lobes

Forebrain

Brain Stem

Limbic System

Human Brain