BRAIN AND BEHAVIOR Chapter 3 Table of Contents Exit es_a_map_of_the_brain.html?utm_ source=newsletter_weekly_

Neuron and Its Parts Neuron: Individual nerve cell; 100 billion in brain  Dendrites: Receive messages from other neurons  Soma: Cell body; body of the neuron. Receives messages and sends messages down axon  Axon: Carries information away from the cell body  Axon Terminals: Branches that link the dendrites and somas of other neurons Table of Contents Exit

Fig. 2.1 An example of a neuron, or nerve cell, showing several of its important features. The right foreground shows a nerve cell fiber in cross section, and the upper left inset gives a more realistic picture of the shape of neurons. The nerve impulse usually travels from the dendrites and soma to the branching ends of the axon. The neuron shown here is a motor neuron. Motor neurons originate in the brain or spinal cord and send their axons to the muscles or glands of the body. Table of Contents Exit

Fig. 2.2 Activity in an axon can be measured by placing electrical probes inside and outside the axon. (The scale is exaggerated here. Such measurements require ultra-small electrodes, as described later in this chapter.) At rest, the inside of an axon is about –60 to –70 millivolts, compared with the outside. Electrochemical changes in a nerve cell generate an action potential. When positively charged sodium ions (Na + ) rush into the cell, its interior briefly becomes positive. This is the action potential. After the action potential, an outward flow of positive potassium ions (K + ) restores the negative charge inside the axon. (See Figure 2.3 for further explanation.) Table of Contents Exit

Fig. 2.5 A highly magnified view of the synapse shown in Fig Neurotransmitters are stored in tiny sacs called synaptic vesicles. When a nerve impulse arrives at an axon terminal, the vesicles move to the surface and release neurotransmitters. These transmitter molecules cross the synaptic gap to affect the next neuron. The size of the gap is exaggerated here; it is actually only about one millionth of an inch. Transmitter molecules vary in their effects: Some excite the next neuron and some inhibit its activity. Table of Contents Exit

The Nerve Impulse Resting Potential: Electrical charge of an inactive neuron (negative charge) Absolute Threshold: Trigger point for a neuron’s firing Action Potential: Nerve impulse Refractory Period: When a neuron is less willing to fire after firing All or none law: a neuron can’t ½ fire Table of Contents Exit

Fig. 2.4 Cross-sectional views of an axon. The right end of the top axon is at rest, with a negatively charged interior. An action potential begins when the ion channels open and sodium ions (Na + ) enter the axon. In this drawing the action potential would travel rapidly along the axon, from left to right. In the lower axon the action potential has moved to the right. After it passes, potassium ions (K + ) flow out of the axon. This quickly renews the negative charge inside the axon, so it can fire again. Sodium ions that enter the axon during an action potential are pumped back out more slowly. Their removal restores the original resting potential. Table of Contents Exit

Neurotransmitters Chemicals that alter activity in neurons; brain chemicals  Acetylcholine: Activates muscles  Dopamine: Muscle control and pleasure  Serotonin: Mood and appetite control  Endorphins: Regulate pain Messages from one neuron to another pass over a microscopic gap called a synapse Table of Contents Exit

Nerves and Neurons Nerves: Large bundles of axons and dendrites Myelin: Fatty layer that coats some axons  Multiple Sclerosis (MS) occurs when myelin layer is destroyed; numbness, weakness, and paralysis occur Table of Contents Exit qgySDmRRzxY

Neural Networks Central Nervous System (CNS): Brain and spinal cord Peripheral Nervous System: All parts of the nervous system outside of the brain and spinal cord  Somatic System: Carries messages to and from skeletal muscles and sense organs; controls voluntary behavior  Autonomic System: Serves internal organs and glands; controls automatic functions such as heart rate and blood pressure Table of Contents Exit

Two Divisions of the Autonomic System Sympathetic: Arouses body; emergency system Parasympathetic: Quiets body; most active after an emotional event Table of Contents Exit

Fig. 2.6 (a) Central and peripheral nervous systems. (b) Spinal nerves, cranial nerves, and the autonomic nervous system. Table of Contents Exit

Fig. 2.7 Subparts of the nervous system. Table of Contents Exit

Fig. 2.8 Sympathetic and parasympathetic branches of the autonomic nervous system. Table of Contents Exit

How is the Spinal Cord Related to Behavior? Reflex Arc: Simplest behavioral pattern; occurs when a stimulus provokes an automatic response Sensory Neuron: Nerve cell that carries messages from the senses toward the CNS Connector Neuron: Nerve cell that links two others Motor Neuron: Cell that carries commands from the CNS to muscles and glands Effector Cells: Cells capable of producing a response Table of Contents Exit

EEG EEG – Electro Encephalogram Shows general brain activity, but not specific structures or structure activity stadium analogy

CT/CAT scan CAT/ CT – Computed Axial Tomography or Computed tomography Uses x-rays and shows anatomical structures, but not specific structure activity

PET PET – Positron Emission Tomography how structures of the brain are activated when performing mental tasks such as hearing, reading, talking, thinking, etc.structures Uses radioactive dye Washington University School of Medicine, St. Louis

MRI MRI – Magnetic Resonance Imaging Uses radio waves and a magnetic field Gives a detailed picture of the brain’s soft tissues

fMRI fMRI – functional Magnetic Resonance Imaging measures the hemodynamic response (amount of 0 2 in the blood due to neural activity) and details activity in specific brain structures

The Brain Pinky and the brain parts OI_865LGTeU

Cerebral Cortex Definition: Outer layer of the cerebrum; contains 70% of neurons in CNS 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 Table of Contents Exit

Split Brains Corpus Callosum is cut; done to control severe epilepsy (seizure disorder) Result: The person now has two brains in one body This operation is rare and is often used as a last resort Table of Contents Exit

Figure 2.17 Corpus Callosum Table of Contents Exit

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

Motor Cortex

Sensory Cortex

When the Brain Fails to Function Properly Aphasia: Language disturbance resulting from brain damage Broca’s Area: Related to language and speech production  If damaged, person knows what s/he wants to say but can’t say the words Wernicke’s Area: Related to language comprehension; in left temporal lobe  If damaged, person has problems with meanings of words, NOT pronunciation Table of Contents Exit

Midbrain Structures are part of Limbic System: System within forebrain closely linked to emotional response and motivating behavior  Thalamus: Relays sensory information on the way to the cortex; switchboard  Hypothalamus: Regulates emotional behaviors and motives (e.g., sex, hunger, rage, hormone release)  Amygdala: Associated with fear responses  Hippocampus: Associated with storing permanent memories; helps us navigate through space Table of Contents Exit

Lower Brain – Old Brain Immediately below cerebral hemispheres  Hindbrain (Brainstem): Consists mainly of medulla and cerebellum  Medulla: Controls vital life functions such as heart rate, swallowing, and breathing  Pons (Bridge): Acts as a bridge between medulla and other structures  Influences sleep and arousal  Cerebellum: (Little Brain) Located at base of brain  Regulates posture, muscle tone, and muscular coordination Table of Contents Exit

Subcortex: Reticular Formation (RF) Reticular Formation: Inside medulla and brainstem  Associated with alertness, attention, and some reflexes (breathing, coughing, sneezing, vomiting)  Reticular Activating System (RAS): Part of RF that keeps it active and alert  RAS acts like the brain’s alarm clock  Activates and arouses cerebral cortex Table of Contents Exit

Fig This simplified drawing shows the main structures of the human brain and describes some of their most important features. (You can use the color code in the foreground to identify which areas are part of the forebrain, midbrain, and hindbrain.) Table of Contents Exit

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Midbrain Structures are part of Limbic System: System within forebrain closely linked to emotional response and motivating behavior  Thalamus: Relays sensory information on the way to the cortex; switchboard  Hypothalamus: Regulates emotional behaviors and motives (e.g., sex, hunger, rage, hormone release)  Amygdala: Associated with fear responses  Hippocampus: Associated with storing permanent memories; helps us navigate through space Table of Contents Exit

Endocrine System Glands that pour chemicals (hormones) directly into the bloodstream or lymph system Pituitary Gland: Regulates growth via growth hormone Too little means person will be smaller than average  Hypopituitary Dwarfs: As adults, perfectly proportioned but tiny  Treatable by using human or synthetic growth hormone; will add a few inches  Treatment is long and expensive Table of Contents Exit

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Endocrine System (cont.) Too much growth hormone leads to giantism  Excessive body growth Acromegaly: Enlargement of arms, hands, feet, and facial bones  Caused by too much growth hormone secreted late in growth period  Andre the Giant Pituitary also governs functioning of other glands, especially thyroid, adrenals, and gonads Table of Contents Exit

Endocrine System (cont.) Pineal Gland: Regulates body rhythms and sleep cycles.  Releases hormone melatonin, which responds to daily variations in light Thyroid: In neck; regulates metabolism  Hyperthyroidism: Overactive thyroid; person tends to be thin, tense, excitable, nervous  Hypothyroidism: Underactive thyroid; person tends to be inactive, sleepy, slow, obese Table of Contents Exit

The Adrenal Glands Adrenals: Arouse body, regulate salt balance, adjust body to stress, regulate sexual functioning; located on top of kidneys  Releases epinephrine and norepinephrine (also known as adrenaline and noradrenaline)  Epinephrine arouses body; is associated with fear  Norepinephrine arouses body; is linked with anger Table of Contents Exit

The Adrenal Glands (cont.) Adrenal Medulla: Inner core of adrenals; source of epinephrine and norepinephrine Adrenal Cortex: Produces hormones known as corticoids  Regulate salt balance  Deficiency in some types will cause powerful salt cravings  Also help body to adjust to stress  Secondary source of sex hormones Oversecretion of adrenal sex hormones can cause virilism: exaggerated male characteristics (Bearded woman)  May also cause premature puberty if oversecretion occurs early in life Table of Contents Exit

Plasticity &feature=player_embedded#! &feature=player_embedded#! Plasticity – Brain’s ability to take on new tasks when areas are damaged. Table of Contents Exit

Fig Neuroscientists are searching for ways to repair damage caused by strokes and other brain injuries. One promising technique involves growing neurons in the laboratory and injecting them into the brain. These immature cells are placed near damaged areas, where they can link up with healthy neurons. The technique has proved successful in animals and is now under study in humans. Table of Contents Exit

Fig A direct brain-computer link may provide a way of communicating for people who are paralyzed and unable to speak. Activity in the patient’s motor cortex is detected by an implanted electrode. The signal is then amplified and transmitted to a nearby computer. By thinking in certain ways, patients can move an on-screen cursor. This allows them to spell out words or select from a list of messages, such as “I am thirsty.” Table of Contents Exit