James Parise Chapter 2 Neuroscience and Behavior Biological Psychologists – Branch concerned with the links between psychology and behavior and mental processes. Neurons: Nerve cells – Dendrites – Axon – Cell Body – Myelin Sheath Dendrites – Bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body. – Receive information. Axons – Fibers that pass the impulses to other neurons or to muscles or glands. – Pass information on – Can be very long Myelin Sheath – Layer of fatty acid that insulates some neurons and helps speed their impulses. – Very important—multiple sclerosis. Action Potential – Brief electrical charge that travels down the axon. – Electricity generated from chemical events-exchange of electrically charged atoms called ions. Fluid Interior (of resting axon) – Excess of negatively charged potassium ions. Fluid Exterior (of resting axon) – Has positively charged sodium ions Resting Potential – this positive-outside/negative-inside state of the axon. Selectively Permeable – Axon's surface is very selective in what it allows inside. Refractory Period – Resting pause...the neuron pumps the positively charged sodium atoms back outside. – Then it can fire again. – Can occur 100-1000 times per second. Neuron receives signals...
Excitatory—Pushing on a neuron's accelerator Inhibitory—Pushing on a neuron's break – If the excitatory signals minus the inhibitory signals exceed threshold(minimum intensity) an action potential will occur. How Neurons Communicate Synapse- The gap (1 millionth of an inch wide) that separates the axon terminal of one neuron from the receiving neuron Neurotransmitters – Action potential reaches the terminals at the axon's end (axon terminal), it triggers the release of chemical messages. – Cross the synaptic gap and bind to receptor sites on receiving neuron. Reuptake – Excess neurotransmitters- sending neuron reabsorbs them. Neurotransmitters – Acetylcholine – Endorphines – Dopamine – Serotonin Acetylcholine – Vital role in learning and memory – Messenger at every junction between motor neuron and skeletal muscle – A Ch released to muscle cells- they contract – Transmission blocked- muscle can't contract – Alzheimer's Disease Endorphins – Associated with pleasure and to alleviate pain – “Natural Opiates” Agonists – Excite – Drug molecule that is similar enough to neurotransmitters to mimic it's effects – Or..block neurotransmitter's reuptake. Antagonists – Inhibits the neurotransmitter's release – Or..similar enough to neurotransmitter to block its effect – Not similar enough to stimulate the receptor Blood Brain Barrier – Enables brain to reject unwanted chemicals circulating in blood – Some chemicals don't have right shape to slither through – Hard to design therapeutic drugs- blocks them
Parkinson's Tremors – Result from death of nerve cells that produce dopamine – Give them dopamine..doesn't work. Won't cross. – L-dopa- can sneak through Nervous System – Neurons communicating with other neurons form our body's primary information system Central Nervous System (CNS) – Brain – Spinal Cord Peripheral Nervous System (PNS) – Links the CNS with the body's sense receptors, muscles, and glands – Somatic and autonomic – Sensory and motor axons carrying the PNS info are bundled into electric cables- nerves 3 Types of Neurons Sensory- send information from body's tissues and sensory organs inward to the brain and spinal cord. Interneurons- Internally communicate between sensory and motor neurons. Motor- Carry outgoing information from the CNS to the muscles and glands. Somatic Nervous System – Controls the movements of our skeletal muscles – Voluntary movement Autonomic Nervous System – Controls the glands and muscles of our internal organs – Heartbeat, digestion, glandular activity – Dual system: sympathetic nervous system and parasympathetic nervous system Sympathetic Nervous System – Arouses us for defensive action – If something alarms/enrages us...accelerated heartbeat, slow digestion, raise blood sugar, dilate arteries, cool you with sweat – Makes you alert and ready for action Parasympathetic Nervous System – When the stress subsides – Produces the opposite effects: conserves energy by calming heartbeat, lowering blood sugar, etc. They work together to keep us in a balanced state. Spinal Cord – Information highway connecting the peripheral nervous system to the brain – Ascending neural tracts send up sensory information – Descending neural tracts send back motor control information
Reflexes – Automatic responses to stimuli – Single sensory neuron- interneuron in spinal cord- motor neuron – Move your hand away from flame before your brain receives and responds to the information that causes you to feel pain Neural Networks – Neurons cluster into work groups – Interconnected neural cells – With experience, networks can learn – Practicing piano, jump shot Clinical Observations – Oldest method- observe the effects of brain diseases and injuries Manipulating the Brain – Stimulate various parts of brain- note effects – Lesion- surgically destroy tissue in specific brain areas in animals Reordering Brain's Electrical Activity – Electroencephalogram (EEG)- amplified recording of the waves of electrical activity that sweep across the brain's surface – Electrodes on scalp Neuroimaging Techniques – CT Scan (computed tomography)- examines the brain by taking x-ray photos that can reveal brain damage. – PET Scan (Position Emission Tomography)- depicts brain activity by showing each brain area's consumption of its chemical fuel. – MRI (Magnetic Resonance Imaging)- uses magnetic fields and radio waves to produce computer generated images that distinguish among different types of soft tissue. – Allows to see structures in the brain. Lower Level Brain Structures – Brainstem – Thalamus – Crebellum – Limbic System Brainstem – Begins where spinal cord enters skull and swells slightly..forming the medulla – Medulla- base of the brain stem: controls heartbeat and breathing – Cross-over-point: most nerves to and from each side of the brain connect with the body's opposite side – Reticular Formation- filters incoming stimuli and relays important info to other areas of the brain. Thalamus
– –
Located on the top of the brainstem Sensory switchboard (all senses but smell)
Cerebellum – “little brain” – Rear of brainstem – Most obvious function- coordinating voluntary movement The Limbic System – Amygdala – Hypothalamus – Pituitary Gland Doughnut shaped system of neural structures at the boarder of the brainstem and cerebral hemispheres Amygdala – Influences aggression and fear – Not the only control center for fear/aggression Hypothalamus – Neural structure that lies below thalamus – Directs several maintenance activities (hunger, thirst, body temperature, sexual behavior) – Controls endocrine system (hormones) Cerebral Cortex – Intricate covering of interconnected neural cells- forms a thin surface layer on cerebral hemispheres – Body's ultimate control/information processing area Structure of Cortex – 1/8 of an inch thick – 20 to 23 billion nerve cells – Gial Cells: Guide neural connections, provide nutrients and insulating myelin sheath, and mop up ions and neurotransmiters – Wrinkled surface Four Lobes – Frontal Lobe – Parietal Lobe – Occipital Lobe – Temporal Lobe Frontal Lobe – Associated with reasoning, planning, parts of speech, movement, emotions, and problem solving – Just beyond forehead Parietal Lobe – At the top and to the rear – Associated with movement, orientation, recognition, perception of stimuli
–
Includes sensory cortex
Occipital Lobe – Associated with visual processing – Basic of the head Temporal Lobe – Dedicated to hearing, auditory perception, and the storage of memories – Just above the ears Fissure: Folds that seperate lobes Functions of the Cortex – Motor Functions – Sensory Functions – Association Areas – Language Motor Functions – Motor Cortex: Strip at back of frontal lobe, form ear to ear across top of brain. – Controls voluntary movements and opposite hemisphere controls opposite side of body Sensory Functions – Sensory Cortex (somatosensory)- Strip at the front of the parietal lobes that registers body sensations. Association Areas – Areas of cerebral cortex that aren't involved in primary motor or snesory functions - Involved in higher mental functions (reading, remembering, thinking, and speaking) Phinneas Gage – Frontal lobe damage can alter personality – Accident where railroad tie went in cheek and through frontal lobe – Can't tell right from wrong Language – Results in intricate coordination of many brain areas – Aphasia: Damage to cortical areas cause impaired use of language Broca's Area – Left Frontal Lobe – Struggle to form words but they could sing Wernicke's Area – Left Temporal Lobe – Speak only meaningless words Angular Gyrus – Reading aloud
– –
Receives information from visual area and recodes it in auditory form Nerve fibers interconnect brain areas
Brain Reorganization – Plasticity: The brain's capacity for modification – Capacity of one brain area to take over the functions of another damaged brain area Splitting the Brain – Corpus Callosum: Wide band of axon fibers connecting the 2 hemispheres of the brain – Split Brains: Cutting the corpus callosum in patients with severe epileptic seizures to control seizures Left Brain---Speech, language, logic, writing Right Brain---Art, music, emotion Endocrine System – Interconnected with the nervous system – Second of body's communication system Glands – Secrete another form of chemical messengers – Hormones-- Originate in one tissue, travel through bloodstream and affect other tissues including the brain – Hypothalamus – Thyroid Gland – Pituitary Gland – Parathyroids – Adrenal Glands – Pancreas – Testis/Ovaries Adrenal Glands – On top of kidneys – Ordered by autonomic nervous system to release epinephrine and norepinephrine Epinephrine/Norepinephrine – Increase heart rate, blood pressure, and blood sugar- providing an energy surge Pituitary Gland – Master Gland – Releases hormones that influence growth – Its secretions also influence the release of hormones by other endocrine glands.