Biological Bases of Behavior Chapter 3 Whats In
Biological Bases of Behavior Chapter 3
What’s In This Chapter? • • • What does biology have to do with our behavior? What’s in a brain? ? ? How does the brain tell the body what to do? How does the body let the brain know what it’s doing? Can your brain do things without the body? Can your body do things without the brain knowing it?
The Brain § Lesion § tissue destruction § a brain lesion is a naturally or experimentally caused
Phineas Gage music video
How we Investigate the Brain Electroencephalogram (EEG) § an amplified recording of the waves of electrical activity that sweep across the brain’s surface § these waves are measured by electrodes placed on the scalp
How we Investigate the Brain • Electrical Stimulation of the Brain (ESB) – Mostly used with research on animals & some human brain surgery – Weak electrical currents sent into a brain structure to activate it • Transcranial magnetic stimulation (TMS) – New technique that temporarily enhance or depress activity in a specific area of the brain (about 2 centimeters in to the brain)
§ CT (computed tomography) Scan § a series of x-ray photographs taken from different angles and combined by computer into a composite representation of a slice through the body; also called CAT scan § Two-dimensional Sample image: Perfusion CT in a patient with stroke demonstrates the part of the brain with severely decreased blood flow (arrows).
What are some common uses of the procedure? • Detection of bleeding, brain damage and skull fractures in patients with head injuries. • Detects a blood clot or bleeding within the brain shortly after a patient exhibits symptoms of a stroke. • Detection of most brain tumors. • Planning radiation therapy for cancer of the brain or other tissues. • Guiding the passage of a needle used to obtain a tissue sample (biopsy) from the brain.
PET Scan PET (positron emission tomography) Scan § a visual display of brain activity (metabolic activity) that detects where a radioactive form of glucose goes while the brain performs a given task
PET Scan Process • observe blood flow or metabolism in any part of the brain. • subject is injected with small quantity of radioactive glucose • Brain cells use glucose as fuel • shows levels of activity as a color-coded brain map • red indicates more active brain areas, • Blue/green: less active areas. • gray outer surface is MRI picture of the surface of the brain inner colored structure is cingulate gyrus, part of the brain's emotional system
MRI Scan MRI (magnetic resonance imaging) § technique uses magnetic fields and radio waves § produces computer-generated images § distinguish among different types of soft tissue § allows us to see structures within the brain § A brief pulse of radio waves disorients the brain’s atoms momentarily, when the atoms return to their normal spin, they release detectable signals.
Healthy brain (left) Brain with schizophrenia (right) enlarged fluid filled brain region
Examples of PET and MRI techniques Thalamus Cortex • These 2 images show subjects who received a painful injection of the chemical capsaicin into the upper arm. show increased blood flow (the PET scan shows the thalamus and primary somatosensory cortex after the injection. The gray areas of the images (the MRI) Using this method can identify the areas of the brain that are active during specific conditions. • could be used to study just about any other cognitive function.
f. MRI Scan • Functional magnetic resonance imaging (f. MRI) – New MRI that monitors blood flow and oxygen consumption in the brain to identify areas of high activity – Higher resolution than a PET scan – Investgating the Anatomy of Sexual Arousal • p. 96 Discussion
Brain Structures • The brain has three main parts: the forebrain, midbrain, and hindbrain. • The forebrain: cerebrum, thalamus, hypothalamus, & Limbic system • The midbrain: part of the brainstem • The hindbrain: cerebellum, pons and medulla (lower part of the brainstem)
Lower-Level Brain Structures § Brainstem § § the oldest part central core of the brain beginning where the spinal cord swells as it enters the skull responsible for automatic survival functions § Medulla [muh-DUL-uh] § base of the brainstem § controls heartbeat and breathing
The Brain
Brain stem • "brain stem" is the part of your brain that was first to evolve in primitive human beings. • called a "reptilian brain" since it resembles almost the whole brain of a reptile. • source of all your instincts and feelings! • links your brain to your "spinal cord. “ • It is where all the incoming and outgoing "messages" come together and cross over.
Controls sleeping, waking, and dreaming
§ Reticular Formation (the panty hose) § a nerve network inside the brainstem that plays an important role in controlling arousal/sleep § Severe damage can induce a coma § Located in the brainstem § Thalamus [THAL-uh-muss] (411 operator) § the brain’s sensory switchboard, located on top of the brainstem; communication passes through § it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla
Cerebellum [sehr-uh-BELL-um] “Sarah the Southern Belle” § the “little brain” attached to the rear of the brainstem § it helps coordinate voluntary movement and balance § Important in walking, balance, or shaking hands
The Limbic System
§ Limbic System: a doughnut-shaped system of neural structures at the border of the brainstem and cerebral hemispheres § emotions such as fear and aggression § basic drives such food and sex § includes the hippocampus, amygdala, and hypothalamus. § Amygdala [ah-MIG-dah-la] § two almond-shaped neural clusters that are components of the limbic system and are linked to emotion (aggression/rage and fear)
Hypothalamus: § neural structure lying below (hypo) the thalamus; directs several maintenance activities § eating § drinking § body temperature § helps govern the endocrine system via the pituitary gland § is linked to emotion § “pleasure center” or “reward center”
The Limbic System § Electrode implanted in reward center § So reinforcing that the mouse pressed the pedal up to 7000 x in one hour
The Cerebral Cortex § the intricate fabric of interconnected neural cells that covers the cerebral hemispheres § the body’s ultimate control and information processing center Glial Cells- glue cells § cells in the nervous system that support, nourish, and protect neurons
Cerebral Cortex: Basic Subdivisions
Structure of the Cerebral Cortex Frontal Lobes “behind your forehead” § involved in speaking and muscle movements and in making plans (initiative) and judgments (morality) Parietal Lobes “top and rear” § include the sensory cortex Occipital Lobes “back of head” § include the visual areas, which receive visual information from the opposite visual field Temporal Lobes “above the ears” § include the auditory areas
Function of the Cerebral Cortex Motor Cortex § area at the rear of the frontal lobes that controls voluntary movements Sensory Cortex § area at the front of the parietal lobes that registers and processes body sensations
The Cerebral Cortex
The Cerebral Cortex § Functional MRI scan shows the visual cortex (occipital lobes) activated as the subject looks at faces
Visual and Auditory Cortex Occipital Lobes Temporal Lobes
Association Areas § More intelligent animals have increased “uncommitted” or association areas of the cortex
The Cerebral Cortex & Language 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 and expression
Specialization and Integration
Specialization and Integration § Brain activity when hearing, seeing, and speaking words
The Cerebral Cortex: Brain Reorganization § Plasticity § the brain’s capacity for modification, as evident in brain reorganization following damage (especially in children) and in experiments on the effects of experience on brain development § Children have a surplus of neurons § When one area is damaged, other areas may in time reorganize and take over some of its functions § “stem cell research”
Our Divided Brains Corpus callosum Corpus Callosum § large band of neural fibers § connects the two brain hemispheres § carries messages between the hemispheres § Transfer more than a billion bits of info per sec.
Our Divided Brains § The information highway from the eye to the brain § The opposite side of the brain’s hemisphere controls the opposite side of the body
Hemispheric Specialization
The Hemispheres of the Brain Clinical neurologists Gereon Fink of the University of Düsseldorf in Germany and John Marshall from the Radcliffe Infirmary in Oxford, pursued the idea that the difference between the two hemispheres lay in their style of working.
“The left brain does the work that no one in their right mind would want to do. ” -Amanda Barrow 1 st period
The Left Hemisphere (Verbal) • The left brain focuses on detail. • It is the natural home for all mental skills that need us to act in a series of discrete steps or fix on a particular fragment of what we perceive. • skills such as recognizing a friend's face in a crowd or "lining up" words to make a sentence.
LEFT Hemisphere FUNCTIONS Speech Language Logic Writing
RIGHT Hemisphere FUNCTIONS • concentrates on the broad, background picture. • It has a panoramic focus. . • good at seeing general connections • best able to represent the relative position of objects in space • handles emotional and metaphorical aspects of speech.
Right Hemisphere Functions Spatial Reasoning Art Music Emotions
• So, in a neat and complementary division of labor, one side of the brain thinks and sees in wide-angle while the other zooms in on the detail.
• To examine the functions carried out by each hemisphere, neurologists scanned the brain of subjects while they were shown a series of letter navons. A letter navon is a large letter composed of smaller letters as shown in the side box. The researchers soon found out that while the subjects concentrated on the small F's, the left hemisphere showed greater activity; when they focused on the big S, the right hemisphere became active. • Thus, they had demonstrated that the left hemisphere focused on the details, while the right perceived the overall, background picture.
Split Brain § A condition in which the two hemispheres of the brain are isolated by cutting the connecting fibers (corpus callosum) between them.
Split Brain Sperry & Gazzaniga “What word did you see? ” or “Look at the dot. ” Two words separated by a dot are momentarily projected. “Point with your left hand to the word you saw. ”
Split Brain • Only 10 split-brain studies • Perceptual asymmetries- right and left imbalances btwn the cerebral hemispheres in the speed of visual or auditory processing -This corresponds with split-brain studies and shows the specialization of the hemispheres
Test yourself for Split Brain • Perform the following task simultaneously. You should be able to do both tasks with ease if you are split-brain • Draw a picture of a house; include windows, door, chimney with either hand • With the other hand, write your first and last name in cursive writing. • You can’t stop one task to work the other!
Neural and Hormonal Systems
Neural Communication Biological Psychology § branch of psychology concerned with the links between biology and behavior § some biological psychologists call themselves behavioral neuroscientists, neuropsychologists, § behavior geneticists, physiological psychologists, or biopsychologists
Neuron Neural Communication § a nerve cell § the basic building block of the nervous system cell body contains the nucleus, mitochondria and other organelles typical of eukaryotic cells. Dendrite § the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body Axon § the extension of a neuron, ending in branching terminal fibers, through which messages are sent to other neurons or to muscles or glands, sends info away from cell body
Neural Communication § Myelin [MY-uh-lin] Sheath § a layer of fatty cells segmentally encasing the fibers of many neurons § enables vastly greater transmission speed of neutral impulses
Neural Communication
Neural Communication Action Potential § a neural impulse; a brief electrical charge that travels down an axon § generated by depolarization (the movement of positively charged atoms in and out of channels in the axon’s membrane) Threshold § the level of stimulation required to trigger a neural impulse
Neural Communication Synapse [SIN-aps] § 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 travel the synaptic gaps between neurons § when released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether it will generate a neural impulse
Neural Communication Cell body end of axon Direction of neural impulse: toward axon terminals
Neural Communication
FILM Chapter 2: Embryonic and Fetal Brain Development (13 min 28 sec) Safari Montage http: //videoservicesondemand. volusia. k 12. fl. us/SAFARI/montage/schoolnews. html
FLUSHING TOILET • All or None Principle: once the handle is pushed and the toilet begins flushing, there is no stopping it. • Once a neuron is fired, it cannot be stopped or it’s message taken back • Like a gun, either a neuron fires or it doesn’t. • The strength of the stimulus does not affect the action potential speed.
Direction of Impulse • A toilet only flows one way-out into the sewage system. The direction never changes. A toilet that is working properly never flows up. • A neuron always fires the impulse in a specific direction- towards the target
Refractory Period • Brief period of time after you flush the toilet during which the handle is useless and the toilet cannot be flushed again. • Same for a neuron, which limits the number of times a neuron can be fired per second. • When positively charged ions are pumped back outside the neural membrane • A camera flash that pauses to recharge
THRESHOLD: • There is a specific level of intensity and a limit to the volume that it is possible to flush down a toilet • The amount of pressure required to push the trigger to flush the toilet • When a toilet is being flushed, a minimum intensity of water pressure is needed in order for the toilet to function properly. • The level of stimulation required to trigger a neural impulse.
Resting Potential • When the toilet is not being flushed, no water moves in or out and is stable. Ready to be flushed immediately • When a neuron is at rest it too is stable; • It is at a polarized state • A resting axon has an excess of neg. charged ions inside and the fluid outside of an axon membrane has an excess of pos. charged ions.
Action Potential • A neural impulse • When a neuron is at a depolarized state • Brief electrical charge that travels down an axon • When a neuron’s receptor is stimulated, ions rush in and energy flows down the axon • The toilet handle is pushed to initiate water rushing into and flowing down the toilet
Depolarization • Pushing the handle stimulates the toilet into action. New water coming into the bowl. the flow of positively charged ions into the axon leads the axon to become positively charged relative to the outside. • Causes the next channel to open. • Domino effect
Depolarization
Neural Communication
Neural Communication Serotonin Pathways Dopamine Pathways
Neural Communication Acetylcholine [ah-seat-el-KO-leen] § a neurotransmitter that, among its functions, triggers muscle contraction…& thus, movement § Linked to Alzheimer's disease Endorphins [en-DOR-fins] § “morphine within” § natural, opiate-like neurotransmitters § linked to pain control and to pleasure
Neural Communication Neurotransmitter molecule Receptor site on receiving neuron Receiving cell membrane Agonist mimics neurotransmitter Antagonist blocks neurotransmitter
Agonist –vs- Antagonist • • Excitatory Can mimic the nt Can block nt’s reuptake Opiates enhance normal arousal or sensation of pleasure • Ecstacy enhances sexual arousal • Inhibitory • Prevents the nt’s release • Or occupy its receptor site and block its effect • Is similar but not enough to stimulate the receptor • Foreign money in a snack machine
Ecstasy Agonist • MDMA (3, 4 -methylenedioxymethamphetamine), most commonly known by the street names ecstasy or XTC primary effect is believed to be the stimulation of secretion as well as inhibition of re-uptake of large amounts of serotonin as well as dopamine and norepinephrine in the brain, inducing a general sense of openness, empathy, energy, euphoria, and wellbeing. Tactile sensations are enhanced for some users, making general physical contact with others more pleasurable;
BOTOX Antagonist • botox is toxic compound. It is an enzyme that breaks down one of the fusion proteins that allow neurons to release acetylcholine. Small doses block the release of acetylcholine by nerve cells that signal muscle contraction. • Botox originally produced for the intended relief of uncontrollable muscle spasms. First approved in 1989 to treat two eye muscle disorders--uncontrollable blinking (blepharospasm) and misaligned eyes (strabismus • Increasingly being used for cosmetic purposes, to paralyse facial muscles as a means of concealing wrinkles.
NICOTINE Agonist • an increase in acetylcholine causes a increased heart rate and increased production of saliva. • Nicotine acts by increasing the activity of certain acetylcholine receptors Nicotine is a potent nerve poison and is included in many insecticides. • In lower concentrations, is a stimulant and one of the main factors leading to the pleasure and habit-forming qualities of tobacco smoking.
NEUROTRANSMITTER ANTAGONIST • Curare is a potent neurotoxin. Used as an arrow poison by some Indian peoples of South America • Death from curare is caused by loss of the ability to breathe as a result of paralysis. The alkaloid curare molecule mimics the neurotransmitter acetylcholine by binding to its receptor at muscle synapses. This prevents nerves from stimulating muscle contraction.
NEUROTRANSMITTER Agonist • The venom of a black widow spider causes a synaptic flood of ACH. • Results in violent muscle contractions, convulsions, and possible death.
Bipolar Disorder • occurs with equal frequency in men and women. The peak age of onset is during late teens. • Neurotransmitter abnormalities in a number of pathways including serotonin, norepinephrine, dopamine, acetylcholine • thalamus, hypothalamus, amygdala, prefrontal cortex, and cerebellum.
The Nervous System § the body’s speedy, electrochemical communication system § consists of all the nerve cells of the peripheral and central nervous systems Central Nervous System (CNS) § the brain and spinal cord Peripheral Nervous System (PNS) § the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body
The Nervous System Nervous system Central (brain and spinal cord) Peripheral Autonomic (controls self-regulated action of internal organs and glands) Somatic Skeletal (controls voluntary movements of skeletal muscles) Sympathetic (arousing) Parasympathetic (calming)
The Nervous System Nerves § neural “cables” containing many axons § part of the peripheral nervous system § connect the central nervous system with muscles, glands, and sense organs Sensory Neurons § neurons that carry incoming information from the sense receptors to the central nervous system
The Nervous System Interneurons § CNS neurons that internally communicate and intervene between the sensory inputs and motor outputs Motor Neurons § Longest portion is the axon § carry outgoing information from the CNS to muscles and glands Peripheral Nervous System 1. Somatic Nervous System – voluntary (skeletal) 2. Autonomic nervous system- involuntary (glands/muscles)
Peripheral Nervous System Somatic Nervous System § the division of the peripheral nervous system that controls the body’s skeletal muscles § Afferent neurons- carry information inward to the central nervous system from the periphery of the body § Efferent neurons- carry information outward from the central nervous system to the periphery of the body
The Nervous System Autonomic Nervous System § the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart) A. Sympathetic Nervous System § division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations § Fight or Flight B. Parasympathetic Nervous System § division of the autonomic nervous system that calms the body, conserving its energy
The Autonomic Nervous System chart on p. 91
The Autonomic Nervous System chart on p. 91
Reflex The Nervous System § a simple, automatic, inborn response to a sensory stimulus Brain Sensory neuron (incoming information) Muscle Skin receptors Motor neuron (outgoing information) Interneuron Spinal cord
The Nervous System Neurons in the brain connect with one another to form networks Inputs Neural Networks § interconnected neural cells § with experience, networks can learn, as feedback strengthens or inhibits connections that produce certain results Outputs The brain learns by modifying certain connections in response to feedback
The Endocrine System § the body’s “slow” chemical communication system § a set of glands that secrete hormones into the bloodstream
Neural and Hormonal Systems Hormones § chemical messengers, mostly those manufactured by the endocrine glands, that are produced in one tissue and affect another Adrenal [ah-DREEN-el] 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 Pituitary Gland § under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands
• The adrenal glands are orange-colored endocrine glands which are located on the top of both kidneys
Pituitary Gland The Master Gland • Prolactin - Prolactin stimulates milk production from the breasts after childbirth • Growth hormone or GH - GH stimulates growth in childhood • In adults it is important for maintaining muscle mass as well as bone mass. It also affects fat distribution in the body. • Adrenocorticotropin or ACTH - ACTH stimulates production of cortisol by the adrenal glands. Cortisol, a so-called "stress hormone" is vital to survival • Luteinizing hormone or LH - LH regulates testosterone in men and estrogen in women. • Follicle-stimulating hormone or FSH - FSH promotes sperm production in men and stimulates the ovaries to enable ovulation in women • Thyroid-stimulating hormone or TSH - TSH stimulates the thyroid gland, which regulates the body's metabolism, energy, growth and development • Follicle-stimulating hormone or FSH - FSH promotes sperm production in men and stimulates the ovaries to enable ovulation in women
• • "Gene Therapy": production of transgenic mice Mice homozygous for a dwarfism gene (lit / lit) grow at a slow rate. An artificial plasmid (top left) is constructed that combines a rat growth-hormone (RGH) gene fused to a mouse metallothionein promoter (MP) gene. A large number of these plasmids are then injected into fertilized eggs of mice; in a small fraction of cases the plasmid is stabily integrated into the mouse's chromosomes. Production of RGH can then be induced by exposure of the embryo to heavy-metals, which activates the MP promoter. The resulting transgenic offspring (left) weighs 44 g (its control sibling weighs 29 g). The recombinant chromosome is subsequently inherited in a Mendelian dominant pattern.
Gigantism • Gigantism is an excessive secretion of growth hormone during childhood before the closure of the bone growth plates, which causes overgrowth of the long bones and very tall stature. he vertical growth in height that marks this condition is also accompanied by growth in muscles and organs, which makes the child extremely large for his or her age. The disorder can also delay puberty.
The Doughnut Assignment • • Select a doughnut that best represents your limbic system Place skittles in the sequential order for the following: Hypothalamus: green skittle Pituitary gland: yellow skittle Amygdala: 2 peanut M&Ms Hippocampus: orange skittle “Bon Appetite”
Practice Test 1. A neural impulse is initiated when a neuron’s charge momentarily becomes less negative, or even positive. This event is called: a. b. c. d. An action potential A resting potential Impulse facilitation Inhibitory
Practice Test 2. Neurons convey information about the strength of stimuli by varying: a. b. c. d. The size of their action potentials The velocity of their action potentials The rate at which they fire action potentials All of the above
Practice Test 3. Alterations in activity at dopamine synapse have been implicated in the development of: a. b. c. d. Anxiety Schizophrenia Alzheimer's disease Nicotine addiction
Practice Test 4. Tania just barely avoided a head-on collision on a narrow road. With heart pounding, hands shaking, and body perspiring. Tania recognizes that these are signs of the body’s fight or flight response, which is controlled by the: a. b. c. d. Empatheic division of the peripheral nervous system Parasympathetic division of the autonomic nervous system Somatic division of the peripheral nervous system Sympathetic division of the autonomic, nervous system
Practice Test 5. The hindbrain consists of the: a. Endocrine system and the limbic system b. Reticular formation c. Thalamus, hypothalamus, and cerebrum d. cerebellum, medulla, and pons
Practice Test 6. Juan is watching a basketball game. The neural impulses from his eyes will ultimately travel to his primary visual cortex, but first they must pass through the: a. b. c. d. Amygdala Hypthalamus Thalamus pons
Practice Test 7. The ______ lobe is to hearing as the occipital lobe is to vision. a. b. c. d. Frontal Temporal Parietal cerebellar
Practice Test 8. Paul has profound difficulty producing spoken language. If his problem is attributable to brain damage, the damage would probably be found in: a. b. c. d. The cerebellum Sperry’s areas Broca’s area Wernicke’s area
Practice Test 9. Sounds presented to the right ear are registered: a. b. c. d. Only in the right hemisphere Only in the left hemisphere More quickly in the right hemisphere More quickly in the left hemisphere
Practice Test 10. In people whose corpus callosums have not been severed, verbal stimuli are identified more quickly and more accurately: a. b. c. d. When sent to the right hemisphere first When sent to the left hemisphere first When presented to the left visual field When presented auditorally rather than visually
Practice Test 11. Hormones are to the endocrine system as _____ are to the nervous system. a. b. c. d. Nerves Synapses Neurotransmitters Action potentials
Homework Review
1. Which of the following parts of the brain is most active in decision-making? (a) Reticular formation (b) Corpus Callosum (c) Hypothalamus (d) Cerebral cortex (e) Pituitary gland 2. An individual experiencing a low blood- glucose level would be best advised to do which of the following? (a) take a nap (b) eat a snack (c) drink a glass of water (d) drink a diet soda (e) get some exercise
3. One suspected cause of schizophrenia is the abnormal increase of which of the following neurotransmitters in the brain? (a) Acetylcholine (b) Somatotropin (c) Dopamine (d) Norepinephrine (e) serotonin 4. For most people, speech functions are primarily localized in the (a) right Cerebral hemisphere (b) left cerebral hemisphere (c) Occipital lobe (d) Corpus Callosum (e) Cerebellum
5. People who have experienced severe damage to the frontal lobe of the brain seldom regain their ability to (a) make and carry out plans (b) recognize visual patterns (c) process auditory information (d) process olfactory information (e) integrate their multiple personalities 6. Which of the following is a brain-imaging technique that produces the most detailed picture of brain structure? • (a) Electroencephalography (EEG) • (b) Magnetic Resonance Imaging (MRI) • (c) Positron Emission Tomography (PET) • (d) Computerized Axial Tomography (CAT) • (e) Electromyography (EMG)
7. Stimulations of portions of the left temporal lobe of the brain during surgery will cause the patient to (a) see lights (b) lose the sense of smell (c) jerk the left arm (d) extend the tongue (e) hear sounds 8. The role of the parasympathetic division of autonomic nervous system is to (a) facilitate the body’s fight-or-flight response (b) prepare the body to cope with stress (c) promote rapid cognitive processing (d) prompt the body to use its resources in responding to environmental stimuli (e) establish homeostasis after a fight-or-flight response
9. Which of the following occurs when a neuron is stimulated to its threshold? (a) the movement of sodium and potassium ions across the membrane creates an action potential (b) the neuron hyperpolarizes. (c) neurotransmitters are released from the dendrites (d) the absolute refractory period of the neuron prevents it from responding. (e) the neuron’s equilibrium potential is reached 10. The thalamus processes information for all of the following senses EXCEPT (a) smell (b) hearing (c) taste (d) vision (e) touch
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