The Biological Bases of Behavior Chapter 2 AP

The Biological Bases of Behavior Chapter 2 AP Psychology ~ Ms. Justice

BIG IDEAS Neural Communication 1: What are neurons, and how do they transmit information? 2: How do nerve cells communicate with other nerve cells? 3: How do neurotransmitters influence behavior, and how do drugs and other chemicals effect neurotransmitters? The Nervous System 4: What are the functions of the nervous system’s main divisions? The Endocrine System 5: How does the endocrine system transmit its messages?

BIG IDEAS The Brain 6: How do neuroscientists study the brain’s connections to behavior and mind? 7: What are the functions of important lower-level brain structures? 8: What are the functions served by the various cerebral cortex regions? 9: To what extent can a damaged brain reorganize itself? 10: What do split brains reveal about functions of our two brain hemispheres? 11: How does handedness relate to brain organization?

1: What are neurons, and how do they transmit information?

Neural Communication The body’s information system is built from billions of interconnected cells called neurons. Hi! I’m a neuron… some of my friends call me “nerve cell”

Neuron A nerve cell, or a neuron, consists of many different parts.

Parts of a Neuron Cell Body: Life support center of the neuron. Dendrites: Branching extensions at the cell body. Receive messages from other neurons. Axon: Long single extension of a neuron, covered with myelin [MY-uh-lin] sheath to insulate and speed up messages through neurons. Terminal Branches of axon: Branched endings of an axon that transmit messages to other neurons.

Action Potential A neural impulse. A brief electrical charge that travels down an axon and is generated by the movement of positively charged atoms in and out of channels in the axon’s membrane.

Action Potential

Threshold threshold: the level of stimulation required to trigger a neural impulse Each neuron receives excitatory and inhibitory signals from many neurons. When the excitatory signals minus the inhibitory signals exceed a minimum intensity (threshold) the neuron fires an action potential… or if the excitatory party animals outvote the inhibitory party poopers, the party’s on.

2: How do nerve cells communicate with other nerve cells?

Synapse [SIN-aps] - a junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. This tiny gap is called the synaptic gap or cleft (which is less than a millionth of an inch wide!)

Neurotransmitters are chemicals released from the sending neuron that travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing it to generate an action potential.

Reuptake Excess neurotransmitters in the synapse are reabsorbed into the sending neurons through the process of reuptake.

How is a flushing toilet like a neuron firing? Cat flushing a toilet music video!

How is a flushing toilet like a neuron firing? • All-or-nothing principle – the toilet either flushes completely or not at all; it doesn’t flush a little or a lot • Direction of impulse – the toilet only flushes one way, the impulse can’t come the other direction (you hope!) • Refractory period – after you flush the toilet, it won’t flush again for a certain period of time, even if you push the handle repeatedly • Threshold – you can push the handle a little bit, but it won’t flush until you push the handle past a certain point (this corresponds to the level of excitatory neurotransmitters that a neuron must absorb before it will fire) • Resting potential –the toilet is waiting to fire, and the water in the tank represents the overall negative charge inside the neuron waiting for depolarization • Action potential – opening the flap in the tank and the water rushing through the pipes • Depolarization – represented by the toilet flushing

3: How do neurotransmitters influence behavior, and how do drugs and other chemicals affect neurotransmission?

Lock & Key Mechanism Neurotransmitters bind to the receptors of the receiving neuron in a key-lock mechanism. Drugs and other chemicals affect brain chemistry at synapses, often by either amplifying or blocking a neurotransmitter’s activity.

How Neurotransmitters Influence Us A particular pathway in the brain may only use 1 or 2 neurotransmitters, and particular neurotransmitters may have particular effects on behavior and emotions: Serotonin pathways are involved with mood regulation. Dopamine pathways are involved with diseases such as schizophrenia and Parkinson’s disease.

Table 2. 1, page 53

Drugs & Other Chemicals § § § Drugs and other chemicals affect brain chemistry at synapses If it is an agonist molecule it will bind to a receptor and mimic the neurotransmitter’s effect § Some opiates are agonists and produce a temporary “high” by amplifying normal sensations of arousal and pleasure If it is an antagonist, the molecule will bind to a receptor and block a neurotransmitter’s function § Poisons like Botulin and Curare can cause paralysis because they block the neurotransmitter from sending signals to the muscles

4: What are the functions of the nervous system’s main divisions?

Nervous System: Consists of all the nerve cells. It is the body’s speedy, electrochemical communication system. Central Nervous System (CNS): the brain and spinal cord. Peripheral Nervous System (PNS): the sensory and motor neurons that connect the CNS to the rest of the body.

The Nervous System Figure 2. 7, p. 55

Peripheral Nervous System Somatic Nervous System: The division of the peripheral nervous system that controls the body’s skeletal muscles. Autonomic Nervous System: Part of the PNS that controls the glands and other muscles, such as the heart.

Autonomic Nervous System (ANS) Sympathetic Nervous System: Division of the ANS that arouses the body, mobilizing its energy in stressful situations (fight-or-flight). . Parasympathetic Nervous System: Division of the ANS that calms the body, conserving its energy (rest and digest). In everyday situations, these two systems work together to keep you in a steady internal state.

Autonomic Nervous System (ANS) Figure 2. 8, p. 56

Central Nervous System The brain’s neurons cluster into neural networks. Neurons networked with each other can have short, fast connections. Learning occurs as feedback strengthens connections. “Neurons that fire together wire together. ” Complex Neural Network A grain-of-sand-sized speck of your brain contains some 100, 000 neurons and 1 billion “talking” synapses!

Central Nervous System The Spinal Cord and Reflexes Fig. 2. 10, p. 58

5: How does the endocrine system –the body’s slower information system- transmit its messages?

The Endocrine System is the body’s “slow” chemical communication system. Communication is carried out by hormones synthesized by a set of glands. Figure 2. 11, p. 59

Hormones are chemicals synthesized by the endocrine glands that are secreted in the bloodstream. Hormones affect the brain and many other tissues of the body. For example, epinephrine (adrenaline) increases heart rate, blood pressure, blood sugar, and feelings of excitement during emergency situations.

Pituitary Gland Is called the “master gland” (and is the most influential endocrine gland). It releases hormones that influence growth and its secretions also influence the release of hormones by other endocrine glands.

6: How do neuroscientists study the brain’s connections to behavior and mind?

Clinical Observation Clinical observations have shed light on a number of brain disorders. Alterations in brain morphology due to neurological and psychiatric diseases are now being catalogued. Tom Landers/ Boston Globe

Electroencephalogram (EEG) An amplified recording of the electrical waves sweeping across the brain’s surface, measured by electrodes placed on the scalp. AJ Photo/ Photo Researchers, Inc.

PET Scan Courtesy of National Brookhaven National Laboratories PET (positron emission tomography) Scan is a visual display of brain activity that detects a radioactive form of glucose while the brain performs a given task.

MRI Scan MRI (magnetic resonance imaging) uses magnetic fields and radio waves to produce computer-generated images that distinguish among different types of brain tissue. Top images show ventricular enlargement in a schizophrenic patient. Bottom image shows brain regions when a participants lies. Both photos from Daniel Weinberger, M. D. , CBDB, NIMH James Salzano/ Salzano Photo Lucy Reading/ Lucy Illustrations

7: What are the functions of the important lower-level brain structures?

Older Brain Structures The brainstem is the oldest part of the brain, beginning where the spinal cord swells and enters the skull. It is responsible for automatic survival functions. The brainstem is also a crossover point, where most nerves to and from each side of the brain connect with the body’s opposite side.

Brainstem The medulla [muh-DUL-uh] is the base of the brainstem that controls heartbeat and breathing. Helpful mnemonic: picture an Olympic athlete wearing gold medals around her neck and covering her heart and lungs.

Brainstem The thalamus [THAL-uh-muss] is the brain’s sensory switchboard, located on top of the brainstem. It directs messages to the sensory areas in the cortex and transmits replies to the cerebellum and medulla. Hal & Amos are traffic cops….

Brainstem Reticular formation is a nerve network in the brainstem that plays an important role in controlling arousal.

Cerebellum The “little brain” attached to the rear of the brainstem. It helps coordinate voluntary movements and balance.

The Limbic System The limbic system is a doughnut-shaped system of neural structures at the border of the brainstem and cerebrum, associated with emotions such as fear, aggression and drives for food and sex. It includes the hippocampus, amygdala, and hypothalamus.

Amygdala The amygdala [ah-MIG-dah-la] consists of two lima bean-sized neural clusters linked to the emotions of fear and anger.

Hypothalamus The hypothalamus directs several maintenance activities like eating, drinking, body temperature, and control of emotions. It helps govern the endocrine system via the pituitary gland. Picture a HYPOdermic needle spraying two thirsty llamas with water to quench their thirst and cool them down.

Reward Center Sanjiv Talwar, SUNY Downstate Rats cross an electrified grid for self-stimulation when electrodes are placed in the reward (hypothalamus) center (top picture). When the limbic system is manipulated, a rat will navigate fields or climb up a tree (bottom picture).

8: What functions are served by the various cerebral cortex regions?

The Cerebral Cortex The intricate fabric of interconnected neural cells that covers the cerebral hemispheres. It is the body’s ultimate control and information processing center. Figure 2. 2, p. 67

Structure of the Cortex Each brain hemisphere is divided into four lobes that are separated by prominent fissures. These lobes are the frontal lobe (forehead), parietal lobe (top to rear head), occipital lobe (back of head), and temporal lobe (side of head). Freud Tore his Pants Off

Functions of the Cortex The motor cortex is the area at the rear of the frontal lobes that control voluntary movements. The sensory cortex (parietal cortex) receives information from skin surface and sense organs. Figure 2. 24, p. 69

Visual Function The functional MRI scan shows the visual cortex is active as the subject looks at faces. Courtesy of V. P. Clark, K. Keill, J. Maisog, S. Courtney, L. G. Ungerleider, and J. V. Haxby, National Institute of Mental Health

Auditory Function A functional MRI scan shows the auditory cortex is active in patients who hallucinate.

Association Areas More intelligent animals have increased “uncommitted” or association areas of the cortex. These areas integrate information, or link sensory inputs with stored memories

9: To what extent can a damaged brain reorganize itself?

Phineas Gage n n n A 19 th century American railroad construction foreman In 1848, survived of an accident in which a large iron rod was driven completely through his head, destroying much of his brain's left frontal lobe The first case suggesting that damage to specific regions of the brain might affect personality and behavior.

Brain and Behavior: Phineas Gage

The Brain’s Plasticity refers to the brain’s ability to modify itself after some types of injury or illness. Severed neurons usually do not regenerate, but some neural tissues can reorganize in response to damage.

10: What do split brains reveal about the functions of our two brain hemispheres?

Our Divided Brain Our brain is divided into two hemispheres.

What Does This Dancer Say About You?

Splitting the Brain A procedure in which the two hemispheres of the brain are isolated by cutting the connecting fibers: mainly those of the corpus callosum. Martin M. Rother Courtesy of Terence Williams, University of Iowa Corpus Callosum

Split Brain Patients With the corpus callosum severed, objects (apple) presented in the right visual field can be named. Objects (pencil) in the left visual field cannot.

Divided Consciousness

Try This! Try drawing one shape with your left hand one with your right hand, simultaneously. BBC

11: How does handedness relate to brain organization?

§Nearly 90% of people are right-handed §More males than females are left-handed §Almost all right-handers (96%), and 70% of left-handers process speech primarily in the left hemisphere §The remaining 30% of left-handers either process speech in the right hemisphere or use both hemispheres §Ultrasound observations of thumb-sucking reveal that more than 9 out of 10 suck the right hand’s thumb §Left-handedness is more common among musicians, mathematicians, professional baseball players, architects, and artists