Chapter 9 Pearson Notes
9.1
Neurons in the nervous system link together to form circuits that have specific functions
Billions of neurons are linked into intricate networks that converge and diverge, creating an infinite number of possible pathways
Signaling within these pathways creates thinking, language, feeling, learning, and memory - the complex behaviors that make us human
Most basic functions require circuits of neurons
Plasticity - the ability to change circuit connections and function in response to sensory input and past experience.
Human brain networks, which easily restructure themselves as the result of sensory input, learning, emotion, and creativity.
The brain can add new connections when neural stem cells differentiate.
Affective behaviors - related to feelings and emotions
Cognitive behaviors - related to thinking
Emergent Properties of Neural Networks
Central Idea
Emergent Properties of Neural Networks
Main Branches
Definition
Characteristics that arise from the interactions of neural network components
Examples
Patterns recognition
Learning and adaptation
Self-organization
Importance
Enhances network functionality
Enables complex problem-solving
Factors Influencing
Network architecture
Training data
Activation function
9.2
All animals have the ability to sense and respond to changes in their environment, even single cell organisms
Unicellular organisms have no obvious brain or integrating center, they use resting membrane potential that exists in living cells and many of the same ion channels are more complex animals to coordinate their daily activities
Nerve net is composed of sensory neurons, connective interneurons, and motor neurons that innervate muscles and glands
Respond to stimuli with complex behaviors, yet without input from an identifiable control center
Electrical signals in the forms of action potentials, and chemical signals passing across synapses, are the same in all animals.
Number and organization of the neurons that one species differs from another.
Flatworms distinction between CNS and PNS is not clear
Rudimentary brain consisting of a cluster of nerve cell bodies concentrated in the head, or cephalic region.
Two large nerves called nerve cords come off the primitive brain and lead to a nerve network
Clusters of cell bodies are no longer restricted to the head region, as they are in flatworms, but also occur in fused pairs called ganglia along the nerve cord.
A ganglion, simple reflexes can be integrated within a segment without input from the brain
Reflexes that do not require integration in the brain also occur in higher animals and are called spinal reflexes in humans and other vertebrates.
Complex reflexes controlled through neural networks.
Nerve cell bodies clustered into brains persist throughout the more advanced phyla and become increasingly more complex
Cephalic brains is that in most animals, the head is the part of the body that first contacts the environment as the animal moves
As brains evolve, they become associated with specialized cephalic receptors, such as eyes for vision and chemoreceptors for smell and taste.
Most dramatic change is seen in the forebrain region, which includes the cerebrum.
The cerebrum is the largest and most distinctive part of the brain, with deep groves and folds
The cerebrum is what makes us human, it is the part of the brain that allows reasoning and cognition
Cerebellum, a region of the hindbrain devoted to coordinating movement and balance.
The cerebellum, like the cerebrum, is readily identifiable in these animals by its grooves and folds.
Evolution of the Nervous System
Central Idea:
Evolutionary changes in the nervous system over time
Main Branches:
Invertebrates:
Jellyfish
Insects
Squid
Vertebrates:
Fish
Amphibians
Reptiles
Birds
Mammals
Sub-branches:
Fish:
Cartilaginous fish
Bony fish
Mammals:
Monotremes
Marsupials
Placental mammals
9.3
The CNS Develops from a Hollow tube
In early embryo, cells that will become the nervous system lie in a flattened region called the neural plate.
Neural plate - A specialized group of cells in the embryo that gives rise to the nervous system.
At about day 20 of human development the neural plate cells along the edge migrate toward the midline.
By about day 23 of human development, the neural plate cells have fused with each other, creating a neural tube.
Neural tube - forms the early brain and spine
Neural crest cells from the lateral edges of the neural plate now lie dorsal to the neural tube.
The lumen of the neural tube will remain hollow and become the central cavity of the CNS
The cells lining the neural tube will either differentiate into the epithelial ependyma or remain an undifferentiated neural stem cells. The outer cell layers of the neural tube will become the neurons and glia of the CNS. Neural crest cells will become the sensory and motor neurons of the peripheral nervous system.
By week 4 of human development, the anterior portion of the neural tube has begun to specialize into the regions of the brain.
Three divisions: forebrain, midbrain, and hindbrain
The tube posterior to the hindbrain will become the spinal cord
Portion of the forebrain that will become the cerebrum is not much larger than the other regions of the brain.
Growth of the cerebrum begins to outpace that of the other regions
By week 6 the CNS has formed the seven major divisions that are present at birth 1) the cerebrum, 2) the diencephalon, 3) the midbrain, 4) and 5) the cerebellum and pons, 6) the medulla oblongata, 7) the spinal cord
Cerebrum and the diencephalon develop from the forebrain
Cerebellum, pons, and medulla oblongata are divisions from the hindbrain
Week 6 the central cavity (lumen) of the neural tube has begun to enlarge into hollow ventricles of the brain.
Two lateral ventricles (the first and second) and two descending ventricles (the third and fourth).
Central cavity of the neural tube also becomes the central canal of the spinal cord.
Week 11 the cerebrum is enlarged
At birth the cerebrum is the largest and most obvious structure we see when looking at the brain
Fully developed cerebrum surrounds the diencephalon, midbrain, and pons, leaving only the cerebellum and medulla oblongata visible below it.
The CNS is Divided into Gray Matter and White Matter
CNS is composed of neurons and supportive glial cells.
Interneurons are those neurons completely contained within the CNS.
Sensory (afferent) and efferent neurons link interneurons to peripheral receptors and effectors.
Tissues of the CNS are divided into gray matter and white matter
Gray matter consists of unmyelinated nerve cell bodies, dendrites, and axons.
Cell bodies are assembled in an organized fashion in both the brain and the spinal cord
Form layers in some parts of the brain and in other parts cluster into groups of neurons that have similar functions.
Clusters of cell bodies in the brain and spinal cord are known as nuclei
White matter is mostly myelinated axons and contains very few neuronal cell bodies.
Pale color comes from myelin sheaths that surround the axons.
Bundles of axons that connect different regions of the CNS are known as tracts
Tracts in the CNS are equivalent to nerves in the PNS
Organized Internal ctytoskelteon that maintain cell shape and orientation, neural tissue has minimal extracellular matrix and must rely on external support for protecting from trauma
Support comes in the form of outer casing of bone, three layers of connective tissue membrane, and fluid between the membranes.
Bone and Connective Tissue Support the CNS
Brain is encased in bony skull, or cranium, the spinal cord runs through a canal in the vertebral column.
Still be seen in the bony vertebrae which are stacked on top of one another and seperated by disks of connective tissue.
Nerves of the PNS enter and leave the spinal cord by passing through notches between the stacked vertebrae.
Meninges lie between the bones and tissue of the CNS.
Help stabilize the neural tissue and protect it from bruising against the bones of the skeleton.
1) the dura matter, 2) the arachnoid, 3) the pia matter
Dura matter thickest of three membranes, veins that drain blood from the brain through vessels or cavities called sinus
Arachnoid membrane is loosely tied to the inner membrane, leaving a subarachnoid space between the two layers
Pia matter is a thin membrane that adheres to the surface of the brain and spinal cord.
Extracellular fluid, which helps cushion the delicate neural tissue
The cranium has an internal volume of 1.4L, of which about 1L is occupied by the cells.
The blood (100-150mL), the cerebrospinal fluid and interstitial fluid together form the extracellular environment for neurons.
The cerebrospinal and interstitial fluid compartments communicate with each other across the leaky junctions of the pial membrane and the ependymal cell lining the ventricles. w
The Brain Floats in Cerebrospinal Fluid
Cerebrospinal fluid (CSF) is a salty solution that is continuously secreted by the choroid plexus, a specialized region on the walls of the ventricles.
Choroid plexus is remarkably similar to the kidney tissue and consists of capillaries and a transporting epithelium.
Selectively pump sodium and other solutes from plasma into the ventricles, creating an osmotic gradient that draws water along with the solutes (osmosis)
Cerebrospinal fluid flows into the subarachnoid space between the pia matter and the arachnoid membrane, surrounding the entire brain and spinal cord in fluid.
Finally absorbed back into the blood by special villi on the arachnoid membrane in the cranium.
Sufficient to replenish the entire volume of cerebrospinal fluid about three times a day.
Physical protection and chemical protection
Brain and spinal cord float
Reduces the weight of the brain nearly fold.
Less pressure on blood vessels and nerves attached to the CNS
Protective padding
CSF must be compressed before the brain can hit the inside of the cranium
Closely regulated extracellular environment for the neurons.
The choroid plexus is selective about which substances it transports into the ventricles
Composition of cerebrospinal fluid is different from that of the plasma
Concentration of K+ is lower, concentration of H+ is higher than in plasma, Na+ in CSF is similar to that in the blood.
Cerebrospinal fluid contains very little protein and no blood cells.
Exchanges solutes with the interstitial fluid of the CNS and provides a route by which wastes can be removed.
Indicator of the chemical environment in the brain.
Spinal tap or lumbar puncture - withdrawing fluid from the subarachnoid space between vertebrae at the lower end of the spinal cord.
Presence of proteins or blood cells in cerebrospinal fluid suggests an infection
The Blood-Brain Barrier Protects the Brain
Functional barrier between the interstitial fluid and the blood.
Isolate the body’s main control center from potentially harmful substances in the blood and from blood-borne pathogens such as bacteria.
400 miles of brain capillaries shelters the brain from toxins and from fluctuations in hormones, ions, and neuroactive substances such as neurotransmitters in the blood
Endothelial cells form tight junctions with one another, junctions that prevent solute movement between the cells
Tight junction formation is induced by paracrine signals from adjacent contractile cells called pericytes and form astrocytes whose foot processes surround the capillary.
The capillary endothelium uses selected membrane carrier and channels to move nutrients and other useful materials from the blood into the brain interstitial fluid.
Any water-soluble molecule that is not transported on one of these carriers cannot cross the blood-brain barrier.
Parkinson’s disease, a neurological disorder in which brain levels of the neurotransmitter dopamine are too low because dopaminergic neurons are either damaged or dead.
The dopamine precursor L-dopa is transported across the cells of the blood-brain barrier on an amino acid transporter, neurons metabolize it to dopamine which allows the deficiency to be treated.
The blood-brain barrier effectively excludes many water-soluble substances, but smaller lipid-soluble molecules can diffuse through the cell membranes.
Older antihistamines were lipid-soluble amines that readily crossed the blood-brain barrier, and acted on brain centers controlling alertness.
A few areas of the brain lack a functional blood-brain barrier and their capillaries have leaky endothelium
Function of adjacent neurons depends in some way on direct contact with the blood
Another region that lacks the blood-brain barrier is the vomiting center in the medulla oblongata.
Neural Tissue Has Special Metabolic Requirements
Neurons require a constant supply of oxygen and glucose to make ATP for active transport of ions and neurotransmitters
About 15% of the blood pumped by the heart goes to the brain and is distributed through the extensive cerebral vascular system
Using about 1/5th of the body’s oxygen supply
Oxygen passes freely across the blood-brain barrier to reach neurons and glial cells
Only energy source for neurons is glucose
Glucose is transported from the plasma across the blood-brain barrier and into the CSF by membrane transporters
Used directly by neurons for aerobic metabolism
Glucose is also taken up by astrocytes and converted to lactate that neurons can use for ATP production
Brain is responsible for about half of the body’s glucose consumption
Progressive hypoglycemia (low blood glucose levels) leads to confusion, unconsciousness, and eventually death.
Anatomy of the Central Nervous System
Central Nervous System
Brain
Cerebrum
Cerebellum
Brainstem
Medulla oblongata
Pons
Midbrain
Spinal Cord
Cervical region
Thoracic region
Lumbar region
Sacral region
9.4
The spinal cord is the major pathway for information flowing back and forth between the brain and the skin, joints, and muscles of the body
Contains neural networks responsible for locomotion
If the spinal cord is severed, loss of sensation from the skin and muscles as well as paralysis, loss of the ability to voluntarily control muscles.
Divided into four regions: cervical, thoracic, lumbar, and sacral
Each spinal region is subdivided into segments, each segment gives rise to a bilateral pair of spinal nerves.
Before a spinal nerve joins the spinal cord, it divides into two branches called roots
Dorsal root of each spinal nerve is specialized to carry incoming sensory information
Dorsal root ganglia, swellings found on the dorsal roots just before they enter the cord, contain cell bodies of sensory neurons.
Ventral root carries information from the CNS to muscles and glands
The spinal cord has a butterfly-or H-shaped core of gray matter
Sensory fibers from the dorsal roots synapse with interneurons in the dorsal horns of the gray matter
Dorsal horn cell bodies, two distinct nuclei, one for somatic information and one for visceral information
Ventral horns of the gray matter contain cell bodies of motor neurons that carry efferent signals to muscles and glands
Efferent fibers leave the spinal cord via the ventral root
White matter can be divided into a number of columns composed of tracs of axos that transfer information up and down the cord
Ascending tracts take sensory information to the brain
Occupy the dorsal and external lateral portions
Descending tracts carry mostly efferent (motor) signals from the brain to the cord
Propriospinal tracts are those that remain within the cord
Self-contained integrating center for simple spinal reflexes, signals passing from a sensory neuron through the gray efferent neuron
Spinal interneurons may route sensory information to the brain through ascending tracts or bring commands from the brain to motor neurons
Interneurons also modify information as it passes through them
The Spinal Cord
Structure
Gray Matter
Dorsal Horn
Ventral Horn
White Matter
Ascending Tracts
Descending Tracts
Functions
Sensory Functions
Carries sensory information to the brain
Motor Functions
Controls voluntary movements
Reflex Functions
Coordinates reflex actions
Protection
Vertebrae
Bony protection
Cerebrospinal Fluid
Cushions and supports
Spinal Nerves
Cervical Nerves
Thoracic Nerves
Lumbar Nerves
Sacral Nerves
9.5
The brain
Reductionist view looks at the individual neurons and at what happens to them in response to chemical or electrical signals
Integrative study might look at groups of neurons and how they interact with one another in circuits, pathways, or networks.
Behavior or physiological response and works backward to dissect the neural circuits that create the behavior or response.
Adult human brain has mass of about 1400g and contains an estimated 85 billion neurons.
Receive as many as 200,000 synapses, those synapses are not fixed and are constantly changing.
The Brain Stem Is the Oldest Part of the Brain
Brain stem is the oldest and most primitive region of the brain and consists of structures that derive from the embryonic midbrain and hindbrain
Divided into white matter and gray matter, anatomy is similar to that of the spinal cord
Ascending tracts from the spinal cord pass through the brain stem, ascending tracts synapse there
Descending tracts from higher brain centers also travel through the brain stem on their way to the spinal cord
Pairs of peripheral nerves branch off the brain stem
Eleven of the 12 cranial nerves originate along the brain stem
Cranial nerves are described according to whether they include sensory fibers, efferent fibers, or both
Cranial nerve X, the vagus nerve is a mixed nerve that carries both sensory and motor fibers
Reticular formation, a diffuse collection of neurons that extends throughout the brain stem
Nuclei in the brainstem are involved in many basic processes, including arousal and sleep, muscle tone and stretch reflexes, coordination of breathing, blood pressure regulation, and modulation of pain.
Brain stem consists of the medulla oblongata, the pons and the midbrain
The cerebral aqueduct connects it to the third ventricle in the diencephalon at its superior end
The inferior end of the fourth ventricle tapers to become the central canal of the spinal cord
Medulla
Medulla oblongata is the transition from the spinal cord into the brain proper
White matter includes ascending somatosensory tracts, bring sensory information to the brain, descending corticospinal tracts that convey information from the cerebrum to the spinal cord
About 90% of corticospinal tracts cross the midline to the opposite side of the body in a region of the medulla known as the pyramids
Each side of the brain controls the opposite side of the body
Gray matter includes nuclei that control many involuntary functions, such as blood pressure, breathing, swallowing, and vomiting
Pons
is a bulbous protrusion on the ventral side of the brain stem above the medulla and below the midbrain
Act as a relay station for information transfer between the cerebellum, and cerebrum
Coordinates the control of breathing along with centers in the medulla
Midbrain
Mesencephalon
relatively small area that lies between the lower brain stem and the diencephalon
Control of eye movement
relays signals for auditory and visual reflexes
The Cerebellum Coordinates Movement
The second largest structure in the brain
Located inside the base of the skull
Most of the nerve cells in the brain are in the cerebellum
Process sensory information and coordinate the execution of movement
Sensory input into the cerebellum comes from somatic receptors in the periphery of the body and from receptors for the equilibrium and balance located in the inner ear
Receives motor input from neurons in the cerebrum
The Diencephalon Contains the Centers for Homeostasis
The diencephalon lies between the brainstem and the cerebrum
Composed of two main sections, the thalamus and the hypothalamus, and two endocrine structures, the pituitary and pineal glands.
Occupied by many small nuclei that make up the thalamus
The thalamus receives sensory fibers from the optic tract, ears, and spinal cord as well as motor information from the cerebellum.
Projects fibers to the cerebrum, where the information is processed.
Almost all sensory information from lower parts of the CNS passes through it.
Modify information passing through it, integrating center as well as a relay station
Hypothalamus lies beneath the thalamus
Occupies less than 1% of total brain volume, center for homeostasis and contains centers for various behavioral drives, such as hunger and thirst.
Output functions of the autonomic division of the nervous system, as well as a variety of endocrine functions
Hypothalamus receives input from multiple sources, including the cerebrum, the reticular formation, and various sensory receptors
Output from the hypothalamus goes first to the thalamus and eventually to multiple effector pathways.
Located in the diencephalon: the pituitary gland and the pineal gland
Posterior pituitary is a down-growth of the hypothalamus and secretes neurohormones that are synthesized in a hypothalamic nuclei
Anterior pituitary is a true endocrine gland
Hormones are regulated by hypothalamic neurohormones secreted into the hypothalamic-hypophyseal portal system
The Cerebrum Is the Site of Higher Brain Functions
Composed of two hemispheres connected primarily at the corpus callosum, a distinct structure formed by axons passing from one side of the brain to the other
Two hemispheres communicate and cooperate with each other
Cerebral hemisphere is divided into four lobes: frontal, parietal, temporal, and occipital
Grooves called sulci, dividing convolutions called gyri
Grows faster than the surrounding cranium
Degree of folding is directly related to the level of processing of which the brain is capable
Gray Matter and White Matter
Cerebral gray matter can be divided into three major regions: cerebral cortex, the basal ganglia, and the limbic system
Cerebral cortex is the outer layer of the cerebrum, only a few millimeters thick.
Neurons distinct vertical columns and horizontal layers
Within these layers that our higher brain functions arise
Basal ganglia controls of movement and also called the basal nuclei.
Limbic system which surrounds the brain stem
Represents probably the most primitive region of the cerebrum
Link between higher cognitive functions, such as reasoning, and more primitive emotional responses such as fear
Amygdala and cingulate gyrus which are linked to emotion and memory, and the hippocampus, which is associated with learning and memory
White matter in the cerebrum is found mostly in the interior
Bundles of fibers allow different regions of the cortex to communicate with one another and transfer information from one hemisphere to the other, primarily through the corpus callosum
Information entering and leaving the cerebrum goes along tracts that pass through the thalamus (with the exception of olfactory information, which goes directly from olfactory receptors to the cerebrum).
The Brain
Central Idea
Brain
Main Branches
Anatomy
Cerebrum
Cerebellum
Brainstem
Functions
Cognitive
Motor
Sensory
Health
Mental Health
Neurological Disorders
Sub-branches
Cerebrum
Frontal Lobe
Parietal Lobe
Temporal Lobe
Occipital Lobe
Cognitive Functions
Memory
Attention
Language
Mental Health
Depression
Anxiety
Bipolar Disorder
9.6
The brain receives sensory input from the internal and external environments, integrates and processes the information, and, if appropriate, creates a response.
Ability to generate information and output signals in the absence of external input.
Three systems that influence output by the motor systems of the body: (1) the sensory system, which monitors the internal and external environments and initiates reflex responses; (2) a cognitive system that resides in the cerebral cortex and is able to initiate voluntary responses; and (3) a behavioral state system, which also resides in the brain and governs sleep-wake cycles and other intrinsic behaviors.
Cognitive and behavioral state systems remain potential sources of influence.
The Cerebral Cortex is Organized into Functional Areas
Cerebral cortex serves as an integrating center for sensory information and a decision-making region for many types of motor output.
(1) sensory areas (also called sensory fields), which receives sensory input and translate it into perception (awareness); (2) motor areas, which direct skeletal muscle movement; and (3) association areas (association cortices), which integrate information from sensory and motor areas and can direct voluntary behaviors.
Functional specialization is not symmetrical across the cerebral cortex: each lobe has special functions not shared by the matching lobe on the opposite side.
Cerebral lateralization of function is sometimes referred to as a cerebral dominance, more popularly known as left brain-right brain dominance.
Language and verbal skills tend to be concentrated on the left side, spatial skills concentrated on the right side.
Left brain is dominant hemisphere for right-handed people, right brain is the dominant hemisphere for many left-handed people.
Neural connections in the cerebrum, exhibit a certain degree of plasticity.
The Spinal Cord and Brain Integrate Sensory Information
Sensory system monitors the internal and external environments and sends information to neural integrating centers, which in turn initiate appropriate responses.
The simplest reflexes can be integrated in the spinal cord, without input from higher brain centers.
Even simple spinal reflexes usually send sensory information to the brain, creating perception of the stimulus.
Information about muscle and joint position and movement goes to the cerebellum as well as to the cerebral cortex, allowing the cerebellum to assist with automatic subconscious coordination of movement.
Primary somatic sensory cortex (also called the somatosensory cortex) in the parietal lobe is the termination point of pathways from the skin, musculoskeletal system, and viscera.
Carry information about touch, temperature, pain, itch, and body position.
Damage to this part of the brain leads to reduced sensitivity of the skin on the opposite side of the body.
Visual cortex, located in the occipital lobe, receives information from the eyes.
Auditory cortex, located in the temporal lobe, receives information from the ear.
Olfactory cortex, a small region in the temporal lobe, receives input from chemoreceptors in the nose
Gustatory cortex, deeper in the brain near the edge of the frontal lobe, receives sensory information from the taste buds.
Sensory Information is Processed into Perception
Neural pathways extend form sensory areas to appropriate association areas, which integrate somatic, visual, auditory, and other stimuli into perception, the brain’s interpretation of sensory stimuli.
Brain translates pressure waves hitting the ear into sound and interprets chemicals binding to chemoreceptors as taste or smell.
We sometimes perceive what our brains expect to perceive
Our perceptual translation of sensory stimuli allows the information to be acted upon and used in voluntary motor control or in complex cognitive functions such as language.
The Motor System Governs Output from the CNS
Motor output component of the nervous system is associated with the efferent division of the nervous system.
(1) skeletal muscle movement, controlled by the somatic motor division; (2) neuroendocrine signals, which are neurohormones secreted into the blood by neurons located primarily in the hypothalamus and adrenal medulla; and (3) visceral responses, the actions of smooth and cardiac muscle or endocrine and exocrine glands
Governed by the autonomic divison
Knee jerk reflex, are processed either in the spinal cord or in the brain stem
Voluntary movements are initiated by the cognitive system and originate in the primary motor cortex and motor association area in the frontal lobes of the cerebrum.
Receive input from sensory areas as well as from the cerebellum and basal ganglia.
Pyramidal cells project axons from the motor areas through the brain stem to the spinal cord.
Descending motor pathways cross to the opposite side of the body, which means that damage to a motor area manifests as paralysis or loss of function on the opposite side of the body
Neuroendocrine and visceral responses are coordinated primarily in the hypothalamus and medulla.
Brain stem contains the control centers for many of the automatic life functions.
Receives sensory information from the body and relays motor commands to peripheral muscles and glands.
Hypothalamus contains centers for temperature regulation, eating, and control of body osmolarity, among others.
Stress, reproduction, and growth are also mediated by the hypothalamus by way of multiple hormones.
Behavioral state system can modulate reflex pathways, and the cognitive system exerts both voluntary and involuntary control over motor functions.
The Behavioral State System Modulates Motor Output
Diffuse modulatory systems originate in the reticular formation in the brain stem and project their axons to large areas of the brain.
Noradrenergic (norepinephrine), serotonergic (serotonin), dopaminergic (dopamine), and cholinergic (acetylcholine).
Dopaminergic pathways also have been implicated in addictive behaviors and the brain’s “reward centers”.
Consciousness is the body’s state of arousal or awareness of self and environment.
Reticular activating system, a diffuse collection of neurons in the reticular formation, plays an essential role in keeping the “conscious brain” awake.
If the connection to the RF to CC is cut then that = coma.
General anesthetics depress synaptic transmission
Blocking ascending pathways between the reticular formation and the cerebral cortex creates a state of unconsciousness.
Measurement of brain activity is recorded by a procedure known as electroencephalography. It detects depolarization of the cortical neurons in the region just under the electrode.
Why Do We Sleep?
Sleep is important for clearing wastes out of the cerebrospinal fluid, particularly some of the proteins that build up in the degenerative neurological diseases such as Alzheimer’s.
20-30 minute “power naps” have also been shown to improve memory, and they can help make up a sleep deficit.
Sleeping brain consumes as much oxygen as the awake brain, so sleep is a metabolically active state.
Electroencephalogram, or EEG, of the waking-alert (eyes open) state shows a rapid, irregular pattern with no dominant waves.
In awake-resting (eyes closed) states, sleep, or coma, electrical activity of the neurons begins to synchronize into waves with characteristic patterns.
More synchronous the firing of cortical neurons, the larger the amplitude of the waves.
Awake-resting state, called stage W, is characterized by low-amplitude, high-frequency waves.
Falls asleep, frequency of the waves decreases.
Rapid eye movement sleep, or REM sleep, and non-REM sleep.
Non-REM sleep is subdivided into stages N1, N2, and N3.
Stage N3 sleep is also called slow-wave sleep or deep sleep.
Presence of delta waves, high-amplitude, low-frequency waves of long duration that sweep across the cerebral cortex.
Adjust body position without conscious commands from the brain to do so.
Rapid eye movement (REM) sleep (stage R) is marked by an EEG pattern closer to that of an awake person, low amplitude, high-frequency waves.
During REM sleep, brain activity inhibits motor neurons to skeletal muscles, paralyzing them.
Exceptions to this pattern are the muscles that move the eyes and those that control breathing.
A typical eight-hour sleep consists of repeating cycles
First hour, the person moves from wakefulness through stages N1 and N3 and finally into a deep sleep
Cycles between deep sleep and REM sleep (stage R), with stages N1 and REM sleep, until finally awakening for the day.
Substances that enhance the immune response, such as interleukin-1, interferon, serotonin, and tumor necrosis factor.
We need to sleep to enhance our immune response.
Caffeine and its methylxanthine cousins theobromine and theophylline
Most widely consumed psychoactive drugs, known since ancient times for their stimulant effect.
Methylxanthines are receptor antagonists for adenosine, a molecule composed of the nitrogenous base adenine plus the sugar ribose.
Insomnia (the inability to go to sleep or remain asleep long enough to awake refreshed), sleep apnea, and sleepwalking.
Sleep apnea is a condition in which the sleep awakes when the airway muscles relax to the point of obstructing normal breathing.
Sleepwalking, or somnambulism is a sleep behavior disorder that for many years was thought to represent the acting out of dreams.
Dreaming occurs during REM sleep (stage 1)
Sleepwalking episodes, subjects eyes are open and registering the surroundings.
Physiological Functions Exhibit Circadian Rhythms
24-hour light-dark cycle and are known as circadian rhythms.
the primary “clock” resides in networks of neurons located in the suprachiasmatic nucleus (SCN) of the hypothalamus, with secondary clocks influencing the behavioral of different tissues.
Clock cycling results from a complex feedback loop in which specific genes turn on and direct protein synthesis.
The protein accumulate, turn off the genes, and then are themselves degraded.
Proteins disappear, the genes turn back on and the cycle begins again.
SCN clock has intrinsic activity that is synchronized with the external environment by sensory information about light cycles received through the eyes.
Body temperature and cortisol secretion both cycle on a daily basis.
Melatonin from the pineal gland also is strongly linked to light-dark cycling.
The suprachiasmatic nucleus had melatonin receptors, supporting the hypothesis that melatonin can modulate clock cycling.
Disruption of circadian rhythms, can have detrimental effects on mental and physical health.
Sleep disturbances, depression, seasonal affective, depressive disorder, diabetes and obesity have all been linked to abnormal circadian rhythms.
Emotion and Motivation Involve Complex Neural Pathways
The limbic system, particularly the region known as the amygdala, is the center of emotion in the human brain.
When the amygdala is artificially stimulated in humans, as it might be during surgery for epilepsy, patients report experiencing feelings of fear and anxiety.
Experimental lesions that destroy the amygdala in animals cause the animals to become tamer and to display hypersexuality
Amygdala is the center for basic instincts such as fear and aggression.
Sensory stimuli feeding into the cerebral cortex are constructed in the brain to create a representation (perception) of the world.
Limbic system to the cerebral cortex creates awareness of the emotion, while descending pathways to the hypothalamus and brain stem initiate voluntary behaviors and unconscious responses mediated by autonomic, endocrine, immune, and somatic motor system
Motivation is defined as internal signals that shape voluntary behaviors.
Some of these behaviors such as eating drinking and having sex are related to survival.
Some motivational states are known as drives and generally have three properties in common: (1) they create an increased state of CNS arousal or alertness, (2) they create goal-oriented behavior, and (3) they are capable of coordinating disparate behaviors to achieve that goal.
Motivated behaviors often work in parallel with autonomic and endocrine responses in the body, as you might expect with behaviors originating in the hypothalamus.
Some motivated behaviors can be activated by internal stimuli.
Eating, curiosity, and sex drive are three examples of behaviors with complex stimuli underlying their onset.
Many motivated behaviors stop when the person has reached a certain level of satisfaction, or satiety, but they may also continue despite feeling satiated.
Pleasure is a motivational state that is being intensely studied because of its relationship to addictive behaviors.
Pleasure is a physiological state is accompanied by increased activity of the neurotransmitter dopamine in certain parts of the brain.
Drugs that are addictive such as cocaine and nicotine act by enhancing the effectiveness of dopamine thereby increasing the pleasurable sensations perceived by the brain.
Not all behaviors that are addictive are pleasurable
Moods are Long-Lasting Emotional States
Moods are similar to emotions but are longer-lasting, relatively stable subjective feelings related to one’s sense of well-being.
Mood disturbances reflect changes in CNS function, such as abnormal neurotransmitter release or reception in different brain regions.
Mood disorders are estimated to be the fourth leading cause of illness in the world today.
Depression is a mood disturbance that affects nearly 10% of the United States population each year.
Sleep and appetite disturbances and alternations of mood and libido that may seriously affect the person’s ability to function at school or work or in personal relationships.
Tricyclic antidepressants, such as amitriptyline, block reuptake of norepinephrine into the presynaptic neuron, thus extending the active lide of the neurotransmitter
Selective serotonin reuptake inhibitors (SSRIs) and serotonin/norepinephrine reuptake inhibitors (SNRIs) slow down the removal of serotonin and norepinephrine from the synapse.
Uptake inhibition, the neurotransmitter lingers in the synaptic cleft longer than usual, increasing transmitter-dependent activity in the postsynaptic neuron
Norepinephrine, serotonin, and dopamine are all involved in brain pathways for mood and emotion
Delay suggests that the changes taking place in the brain are long-term modulation of pathways rather than simply enhanced fast synaptic responses.
Genetic factors, the serotonergic and noradrenergic diffuse modulatory systems, trophic factors such as brain-derived neurotrophic factor (BDNF), and stress.
Learning and Memory Change Synaptic Connections in the Brain
Underlying basis for cognitive function seems to be explainable in terms of cellular events that influence plasticity- events such as long-term potentiation.
Learning is the Acquisition of Knowledge
Associative Learning occurs when two stimuli are associated with each other.
Non-associative learning is a change in behavior that takes place after repeated exposure to a single stimulus.
Habituation and sensitization, two adaptive behaviors that allow us to filter out and ignore background stimuli while responding more sensitively to potentially disruptive stimuli.
Habituation, an animal shows a decreased response to an irrelevant stimulus that is repeated over and over.
Sensitization is the opposite of habituation, and the two behaviors combined help increase an organism’s chances for survival.
Exposure to a noxious or intense stimulus causes an enhanced response upon subsequent exposure.
Sensitization may be maladaptive if it leads to the hypervigilant state known as post-traumatic stress disorder (PTSD)
Memory is the Ability to Retain and Recall Information
Memory is the ability to retain and recall information
Short-term and long-term, reflexive and declarative.
Memories are stored throughout the cerebral cortex in pathways known as memory traces.
Some components of memories are stored in the sensory cortices where they are processed.
Learning a task or recalling a task already learned may involve multiple brain circuits that work in parallel.
Parallel processing helps provide backup in case one of the circuits is damaged.
The hippocampus seems to be an important structure in both learning and memory.
Patients who have part of the hippocampus destroyed to relieve a certain type of epilepsy also have trouble remembering new information.
This inability to remember newly acquired information is a defect known as anterograde amnesia.
Memory has multiple levels of storage, and our memory bank is constantly changing
First goes into short-term memory, a limited storage area that can hold only about 7 to 12 pieces of information at a time.
Items in short-term memory disappear unless an effort, such as repetition, is made to put them into a more permanent form.
Working memory is a special form of short-term memory processed in the prefrontal lobes.
Keeping track of bits of information long enough to put them to use in a task that takes places after the information has been acquired
Damage to the prefrontal lobes of the brain, task becomes more difficult because they are unable to recall whether the road is clear from the left once they have looked away.
Working memory allows us to collect a series of facts from short- and long-term memory and connect them in a logical order to solve problems or plan actions
Long-term memory is a storage area capable of holding vast amounts of information
The processing of information that converts short-term memory into long-term memory is known as consolidation
Process involves changes in neuronal excitability or synaptic connections in the circuits involved in learning
These changes are evidence of plasticity and show us that the brain is not “hard-wired”
Reflexive (implicit) memory, which is automatic and does not require conscious process for either creation or recall, involves the amygdala and the cerebellum
Motor skills fall into this category, as do procedures and rules.
Reflexive memory has also been called procedural memory because it generally concerns how to do things.
Declarative (explicit) memory on the other hand requires conscious attention for its recall.
Depends on the use of higher-level cognitive skills such as inference, comparison, and evaluation
Neuronal pathways involved in this type of memory are in the temporal lobes
Information can be transferred from declarative memory to reflexive memory
Athletes often refer to this automaticity of learned body movements as muscle memory.
No two people will process a given piece of information in the same way.
Strokes and progressive dementia are the main causes of memory loss.
Alzheimer’s disease is a progressive neurodegenerative disease of cognitive impairment that accounts for about half the cases of dementia in the elderly.
Over time, even the personality changes, and in the final stages, other cognitive functions fail so that patients cannot communicate with caregivers.
Diagnosis of Alzheimer’s is usually made through the patient’s declining performance on cognitive function examinations
Only definitive diagnosis of Alzheimer’s comes after death, when brain tissue can be examined for neuronal degeneration, extracellular plaques made of B-amyloid protein, and intracellular tangles of tau, a protein that is normally associated with microtubules
No proven prevention or treatment, although drugs that are acetylcholine agonists or acetylcholinesterase inhibitors slow the progression of the disease.
Language is the Most Elaborate Cognitive Behavior
Exchange of complex information takes place primarily through spoken and written language.
Language skills require the input of sensory information (primarily from hearing and vision), processing in various centers in the cerebral cortex, and the coordination of motor output for vocalization and writing.
Centers for language in the left hemisphere of the cerebrum.
Combination of different sounds to form words (vocalization) and the combination of words into grammatically correct and meaningful sentences.
Integration of spoken language in the human brain has been attributed to two regions in the cerebral cortex: Wernicke’s area at the junction of the parietal, temporal, and occipital lobes and Broca’s area in the posterior part of the frontal lobe, close the motor cortex.
Input into the language areas comes from either the visual cortex (reading) or the auditory cortex (listening).
Sensory input from either cortex goes first to Wernicke’s area, then to Broca’s area.
After integration and processing, output from Broca’s area to the motor cortex initiates a spoken or written action.
Damage to the Wernicke’s area, a person may have difficulty understanding spoken or visual information.
Own speech may be nonsense because the person is unable to retrieve words.
Receptive aphasia because the person is unable to understanding sensory input
Damage to Broca’s area causes an expressive aphasia, or Broca aphasia.
Understand simple, unambiguous spoken and written language but difficulty interpreting complicated sentences with several elements linked together.
Mechanical forms of aphasia occur as a result of damage to the motor cortex.
Personality is a Combination of Experience and Inheritance
Abstract realm of psychology into the physical circuits of neurobiology is the combination of attributes we call personality.
Combination of our experiences and the genetic constraints we inherit
What we learn or experience and what we store in memory create a unique pattern or neuronal connections in our brains.
Genetic component to many of these disorders
Schizophrenia is an example of brain disorder that has both a genetic and an environmental basis
Schizophrenia can be treated with drugs that influence neurotransmitter release and activity in the brain
Physical damage to the delicate circuits of the brain, particularly to the frontal lobe, can create a whole new personality.
Brain Function Mind Map
Central Idea: Brain Function
Main Branches:
Structure of the Brain
Cerebrum
Cerebellum
Brainstem
Brain Processes
Sensory Processing
Motor Function
Cognitive Functions
Neurotransmitters
Dopamine
Serotonin
Acetylcholine
Brain Health
Sleep
Nutrition
Exercise
Brain Disorders
Alzheimer's Disease
Parkinson's Disease
Schizophrenia