Neurons Chapter 3 Dendrites Extensions from the neuron

Neurons Chapter 3

Dendrites Extensions from the neuron cell body that take information TO the cell body.

Cell Body Also called the soma; the part of the cell that contains the nucleus.

Nucleus Part of the neuron that contains chromosomes (genetic material)

Axon The part of the neuron that takes information AWAY from the cell body.

Myelin Fatty substance that surrounds some axons. Speeds up conduction velocity of action potentials.

Node of Ranvier Gaps in the myelination of axons.

Synaptic Terminal The end of the axon containing vesicles with neurotransmitters.

INFORMATION PROCESS DUH, the SAT D=dendrites S=soma A=axon T=terminals

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

Neurotransmitters (p. 58)

Nervous System Central Nervous System (CNS) Peripheral Nervous System (PNS)

Nervous System of nerves involved in thought processes, heartbeat, visual-motor coordination, etc… Central and Peripheral systems

Central Nervous System Consists of the brain and spinal cord

Spinal Cord A column of nerves within the spine that transmits messages from sensory receptors to the brain and from the brain to muscles and glands throughout the body.

Spinal Cord Spinal Reflexes: an unlearned response to a stimulus that may involve only two neurons a) Sensory (afferent) neuron-to cortex b) Motor (efferent) neuron-away SAME You are *affected* by a situation, you *effect* change on someone else. Blink, swallow, knee-jerk, sexual responses, urinating, etc…

Brain Hindbrain(lower part of brain): Medulla-heart rate, blood pressure, respiration Pons-respiration, attention, sleep, dreaming Cerebellum-muscle coordination and balance

Brain Reticular Activating System (RAS): Vital in the functions of attention, sleep, and arousal Injury to RAS can cause comatose Filtering (awakened by infant)

Brain Forebrain (front most part): 1). Thalamus-center of brain Relay station for sensory stimulation Relays sensory input from the eyes to the visual areas of the cerebral cortex Functions of sleep and attention

Brain Forebrain (front most part): 2). Hypothalamus-beneath thalamus and above pituitary gland Body temperature, motivation, emotion Involved in hunger, thirst, sexual behavior, caring for offspring, aggression 4 F’s=feeding, fighting, fleeting, fornicating (pleasure/reward center)

Brain Forebrain (front most part): 3). Limbic system-inner edge of cerebrum and in mammals only Memory, emotion, drives of hunger, sex, aggression Amygdala-facilitates aggressive responses, fear AHH=hypothalamus, amygdala, hippocampus

Brain Forebrain (front most part): 4). Basil ganglia-between thalamus and cerebrum Control of movements and coordination Dopamine produced-degeneration cause Parkinson’s disease

Brain Forebrain (front most part): 5). Cerebrum-crowning glory of brain Cerebral cortex-the wrinkled and convoluted surface Consists of two hemispheres Corpus Callosum-connects the two hemispheres

Peripheral Nervous System Consists of sensory and motor neurons that transmit messages to and from the central nervous system Without the PNS, our brains would be isolated from the world Somatic and Autonomic NS

Somatic Nervous System Connects the central nervous system with sensory receptors, skeletal muscles, and the surface of the body Ex: raising hand, winking, running, posture, balance

Autonomic Nervous System Regulates the glands and the muscles of internal organs Heartbeat, respiration, digestion, dilation of the pupils of the eyes Can occur automatically Sympathetic & Parasympathetic

Autonomic Nervous System Sympathetic- most active during processes that involve the spending of body energy from stored reserves “Fight-or-Flight”

Autonomic Nervous System Parasympathetic- most active during processes that replenish reserves of energy (eating) Calms “parachute)

Autonomic Nervous System Sympathetic-accelerates the heart rate -inhibits digestion Parasympathetic- -decelerates the heart rate -stimulates digestive processes

Lobes of the Brain

Frontal Lobe Located in front of the central sulcus Concerned with reasoning, planning, parts of speech, movement (motor cortex), emotions, and problem-solving

Parietal Lobe Located behind the central sulcus Concerned with perception of stimuli related to touch, pressure, temperature, pain

Temporal Lobe Located below the lateral fissure Concerned with perception and recognition of auditory stimuli (hearing) and memory (hippocampus)

Occipital Lobe Located at the back of the brain, behind the parietal lobe and temporal lobe Concerned with many aspects of vision

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 head) and temporal lobe (side of head).

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Brain Structures

Cerebral Cortex Thought Voluntary movement Language Reasoning Perception

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.

Cerebellum Movement Balance Posture

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

Brain Stem Breathing Heart Rate Blood Pressure

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.

Brain Stem The Medulla [muh. DUL-uh] is the base of the brainstem that controls heartbeat and breathing. Reticular Formation is a nerve network in the brainstem that plays an important role in controlling arousal.

Hypothalamus Body temperature Emotions Hunger Thirst Circadian rhythms 4 F’s

Hypothalamus The Hypothalamus lies below (hypo) the thalamus. It directs several maintenance activities like eating, drinking, body temperature, and control of emotions. It helps govern the endocrine system via the pituitary gland.

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).

Thalamus Sensory processing Movement

Brain Stem The Thalamus [THALuh-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.

Limbic System Emotions Memory

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-dahla] consists of two almondshaped neural clusters linked to the emotions of fear and anger.

Hippocampus Learning Memory

Basal Ganglia Movement

Midbrain Vision Audition Eye movement Body Movement

The Brain A brain lesion experimentally destroys brain tissue to study animal behaviors after such destruction. Techniques to Study the Brain Hubel (1990)

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.

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 computergenerated 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

Auditory Function The 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.

The Brain’s Plasticity The brain is sculpted by our genes but also by our experiences. Plasticity refers to the brain’s ability to modify itself after some type of injury or illness.

Our Divided Brain Our brain is divided into two hemispheres. The left hemisphere processes reading, writing, speaking, mathematics, and comprehension skills. In the 1960 s, it was termed as the dominant brain.

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) between them. 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

Non-Split Brains People with intact brains also show left-right hemispheric differences in mental abilities. A number of brain scan studies show normal individuals engage their right brain when completing a perceptual task and their left brain when carrying out a linguistic task.

Brain Organization & Handedness Is handedness inherited? Yes. Archival and historic studies, as well as modern medical studies, show that the right hand is preferred. This suggests genes and/or prenatal factors influence handedness.

Is it Alright to be Left Handed? Being left handed is difficult in a righthanded world.

Is it Alright to be Left Handed? The percentage of left-handed individuals decreases sharply in samples of older people (Coren, 1993).

Language Functions

Aphasia Damage to the left part of the brain in the cerebral cortex Definition: impaired ability to comprehend or express oneself through language

Broca’s Area Prevents a person from producing speech Person can understand language Words are not properly formed Speech is slow and slurred

Wernicke’s Area Loss of ability to understand language Person can speak clearly, but the words that are put together make no sense. “Word salad” because it appears that the words are all mixed up like the vegetables in a salad

Language Aphasia is an impairment of language, usually caused by left hemisphere damage either to Broca’s area (impaired speaking) or to Wernicke’s area (impaired understanding).

Specialization & Integration Brain activity when hearing, seeing, and speaking words

Journal Would you rather have Broca’s aphasia or Wernicke’s aphasia? Why?

Alzheimer’s Disease

Alzheimer’s Disease A progressive form of mental deterioration that may affect as many as 4 million Americans Connected with aging but it is a disease and NOT part of a normal aging process

Alzheimer’s Disease Characterized by progressive deterioration in mental processes such as memory, language, and problem solving Seriously impairs vocational and social functioning

Alzheimer’s Disease Memory loss: difficult to recall basic info (zip codes, telephone #s, names of grandchildren, addresses) Large gaps in memory for recent events May fail to recognize familiar people or forget their names

Alzheimer’s Disease Continue. . May not recognize themselves in the mirror Unable to recall names of their school, birthplace, parents No longer able to speak in full sentences and limit their verbal responses to a few words

Alzheimer’s Disease Subtle personality changes: signs of withdrawal or irritability May need assistance to manage everyday tasks (selecting clothes to wear) Difficulties in personal functioning (using bathroom and washing themselves)

Alzheimer’s Disease May pace or fidget or display aggressive behavior (yelling, hitting, throwing) May wander off and not be able to find their way back 1 in 3 show signs of hallucinations or delusions

Alzheimer’s Disease Severe cases: People become helplessunable to communicate or walk and require help in toileting and feeding.

Alzheimer’s Disease Discovered by German physician Alois Alzheimer Found brain abnormalities in a 56 -year old woman with dementia

Brain Abnormalities 1) Plaques: destroy brain tissues which leads to loss of memory function, confusion, and other symptoms 2) Tangles: twisted bundles of nerve cells

Biochemical Reduced levels of acetylcholine (ACh): reflect loss of brain cells and can lead to brain trauma, aluminum poisoning Reduced metabolic rates Negative correlation between cognitive performance and metabolic rate

Genetic Transmission 90% of people who inherit a key gene from both parents contract Alzheimer’s disease by the age of 75 Chemotherapy is used to heighten ACh levels Researchers are hopeful that genetic studies may lead to effective medications