Transcript Chapter 2
Chapter 2 Neuroscience and Behavior Neural Communication • Biological/neuroscience Psychology –branch of psychology concerned with the links between biology and behavior –Want a better understanding of sleep and dreams, depression and schizophrenia, hunger, sex, stress and disease Neural Communication • Neuron – a nerve cell – the basic building block of the nervous system • Dendrite – the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body – Brings in info • Axon – the extension of a neuron, ending in branching terminal fibers, through which messages are sent to other neurons or to muscles or glands • Myelin [MY-uh-lin] Sheath – a layer of fatty cells that encase the fibers of many neurons – Speeds up neutral impulses – MS Neural Communication • Action Potential – a neural impulse; a brief electrical charge (Ion) that travels down an axon – Outside the Axon= positive ions – Inside the Axon= negative ions – Even positive and negative= resting potential, which acts like a gate . – Depolarization= unfreezes or ungates the axon allowing the message to go through – Refractory period= resting period, when extra atoms are pushed out – Some signals excite and some inhibit • Threshold – the level of stimulation required to trigger a neural impulse – All or nothing Neural Network Neural Communication • Synapse – junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron – tiny gap at this junction is called the synaptic gap or cleft • Neurotransmitters – chemical messengers that cross the synaptic gaps between neurons – Excite or inhibit – Lock and key – Reuptake • • Neurotransmitters • Each pathway uses different neurotransmitters, each neurotransmitter has a different function • Acetylcholine ( ACH) - muscle contraction, learning and memory – Alzheimer's • Endorphins– “morphine within” – natural, opiatelike neurotransmitters – linked to pain control and to pleasure • Dopamine- alertness and movement – Parkinson's – schizophrenia Neurotransmitters • Serotonin- mood, hunger,sleep and arousal • depression • Norepinephrine- controls alertness and arousal • Gamma-aminobutryic acid (GABA)inhibitory neurotransmitter • Glutamate- A major excitatory neruo., memory – Migraines – Seizures Dopamine pathways How Drugs Effect Neurotransmitters • Many drugs mimic the neurotransmitter –Agonists excite –Antagonists inhibit Neurotransmitter molecule Receptor site on receiving neuron Receiving cell membrane Agonist mimics neurotransmitter Antagonist blocks neurotransmitte The Nervous System The Nervous System Nervous system Central (brain and spinal cord) Peripheral Autonomic (controls self-regulated action of internal organs and glands ) Skeletal (controls voluntary movements of skeletal muscles ) Sympathetic (arousing ) Parasympathetic (calming ) The Nervous System • The Nervous System –Body’s communication system –2 parts- Central and Peripheral –The Nervous System uses 3 types of neurons • 1. Sensory • 2. Interneurons • 3. Motor neurons Central Nervous System • Peripheral Nervous System • • The Peripheral System 2 components –1. Somatic Nervous Systemcontrols our skeletal muscles –2.Autonomic Nervous Systemglands,muscles of our internal organs –Heartbeat, digestion, hormones –1. Sympathetic Nervous Systemdefense actions ( increases heartbeat, muscles contract…..) –2. Parasympathetic- it conserves energy Central Nervous System ( CNS) • Spinal Cord and Brain • Spinal Cord connects peripheral system to the brain • Reflexes Brain Sensory neuron (incoming information) Interneuron Motor neuron (outgoing information) Muscle Skin receptors Spinal cord The Brain Tools of Discovery • Manipulating the brain – • Lesions • electromagnetic charges • chemical and magnetic stimulation • Clinical Observations - looking at damaged brains • Recording Electrical Activity EEG ( electroencephslogram) • an amplified recording of the waves of electrical activity that sweep across the brain’s surface EEG Tools of Discovery • Neuroimaging– CT ( Computed tomography) Scan• X- Ray photographs – PET ( Positron emission tomography) Scan • Looks at sugar glucose to determine brain activity – “HOT SPOTS” – MRI- ( Magnetic Resonance Imaging) • generated images that distinguish among different types of soft tissue; allows us to see structures within the brain. PET Scan PET Scan MRI The Brain Lower Level Brain Structure • Lower Brain Lower Brain• performs life saving operations freeing the higher brain regions to think, dream, memorize.. • We are unaware of most of its functions Lower Level Brain Structure The Brainstem 1. Brainstem- • where spinal cord enters the skull • Crossover point for nerves • responsible for automatic survival functions 2. Medulla- Heartbeat and breathing Lower Level Brain Structure The Brainstem 3. Reticular Formation• Filter and relay station • Controls arousal 4. Thalamus- • Sensory input station,except smell • Receives higher brains replies • Controls electrical cycles. Slows during sleep;speeds up while awake Lower Level Brain Structure The Brainstem • 5. The Cerebellum • Coordinates voluntary movements –Balancing, walking………. • Nonverbal voluntary movement • 6. Pons – Regulates sleep The Limbic System • The Limbic System –associated with emotions such as fear and aggression and drives such as those for food and sex –includes the hippocampus, amygdala, and hypothalamus. The Limbic System • 1. Hippocampus• Processes memory • Forms new memories • 2. Amygdala• Aggression and fear The Limbic System • 3. Hypothalamus- – Controls pituitary gland (hormones) – directs several maintenance activities • eating • drinking • body temperature – Triggers autonomic nervous system – Pleasure Center – Reward Deficiency Syndromealcoholism, binge drinking, drug abuse Psychosurgery? • What is psychosurgery? The Cerebral Cortex • Thin layer covering your cerebral hemispheres- wrinkly thing • Neural cells • Controls body and info • The bigger the better The Cerebral Cortex Structure and Functions 1. Each hemisphere is divided up into 4 lobes • • • • Frontal Occipital Temporal Parietal 2. Glial Cells- - • neural nannies • Support the 22 billion nerve cells The Cerebral Cortex 1. Frontal Lobe- speaking, muscle movement, making plans, judgments • Motor Cortex- outgoing messages to the body The Cerebral Cortex 2.Parietal Lobe- sensory cortex • Sensory Cortex-registers and processes body sensations • Receives info from skin receptors • More sensitive= bigger area 3.Occipital Lobe- receives visual from opposite sides The Cerebral Cortex 4.Temporal Lobes- receive auditory simulation from opposite sides • Don’t need real sounds Functional MRI scan of the visual cortex activated by light shown in the subject’s eyes` Visual cortex Auditory cortex The Cerebral Cortex • Association Areas- areas of the cerebral cortex that are not involved in primary motor or sensory functions involved in higher mental functions such as learning, remembering, thinking, and speaking Association Areas • Aphasia – impairment of language, usually caused by left hemisphere damage either to Broca’s area (impairing speaking) or to Wernicke’s area (impairing understanding) • Broca’s Area – an area of the left frontal lobe that directs the muscle movements involved in speech • Wernicke’s Area – an area of the left temporal lobe involved in language comprehension • Angular Gyrus-auditory sounds The Cerebral Cortex Brain activity when hearing, seeing, and speaking words Brain Reorganization • Plasticity- neural tissue can reorganize in response to damage • Orgasm in foot • Most plastic when young Our Divided Brain Corpus callosum • Corpus Callosum – largest bundle of neural fibers – connects the two brain hemispheres – carries messages between the hemispheres Split Brain • a condition in which the two hemispheres of the brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them • “alien hand syndrome” Hemispheric Differences • Specialization • Each hemisphere has its own specialties • Most people are stronger in one hemisphere • Left- logical, verbal, sequential • Right- emotional, expressive, better at spatial relations Handedness • 90% right handed Percentage of 14% left-handedness 12 The percentage of lefties sharply declines with age 10 8 6 4 2 0 10 20 30 40 50 Age in years 60 70 80 90 Neural and Hormonal Systems • Endocrine System – the body’s “slow” chemical communication system – a set of glands that secrete hormones into the bloodstream Endocrine System • Hormones – chemical messengers, mostly those manufactured by the endocrine glands, that are produced in one tissue and affect another – Growth, reproduction, metabolism, mood……… Endocrine System • Adrenal Glands – a pair of endocrine glands just above the kidneys – secrete the hormones epinephrine (adrenaline) and norepinephrine (noradrenaline), which help to arouse the body in times of stress – Increases heart beat, blood pressure, blood sugar….. Gives us energy Endocrine System • Pituitary Gland – under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands – Master gland Other Hormones /Glands 1. Pineal Gland• Produces melatonin • regulates circadian rhythms • Seasonal Affective disorder 2. Thyroid• Maintains metabolic activities • Lack of thyronixe= mental retardation in children 3. Pancreasreleases insulin and glucagon which regulates blood sugar Other Hormones /Glands • 4. Gonads- –Testis and Ovaries –Release estrogen and testosterone