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The Human Brain
• Contains 10,000 different types of neurons
• Contains 100 billion neurons
• Each neuron communicates with 5,000-200,000 other neurons to make one trillion neuronal connections
BRAIN STRUCTUREThe brain can be divided into three major
regions:• Hindbrain – includes the cerebellum
and two structures found in the lower part of the brainstem: the medulla and the pons
• Midbrain – is the segment of the brainstem that lies between the hindbrain and the forebrain
• Forebrain – is the largest and most complex region of the brain, encompassing a variety of structures, including the thalamus, hypothalamus, limbic system and cerebrum
HINDBRAIN
• Brainstem – the oldest part and central core of the brain, beginning where the spinal cord swells as it enters the skull -
responsible for automatic survival functions• Medulla - base of the brainstem – controls
unconscious but vital functions such as circulating blood, breathing, maintaining muscle tone, and regulating reflexes
HINDBRAIN• Pons – a bridge of fibers that connects the
brainstem with the cerebellum – it also contains several clusters of cell bodies involved with sleep and arousal.
• Cerebellum – (little brain) – critical to the coordination of movement and to the sense of equilibrium or physical balance. There is some evidence that it plays a role in emotional development and modulates sensations of anger and pleasure.
MIDBRAIN
• Contains an area that is concerned with integrating sensory processes, such as vision and hearing
• An important system of dopamine-releasing neurons that projects into various higher brain centers originates here
CORPUS CALLOSUM
Corpus callosumCorpus callosum
Corpus Callous large band of
neural fibers connects the
two brain hemispheres
carries messages between the hemispheres
Plasticitythe 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
Limbic SystemIs the center for our emotions
Responsible for emotion production and storing of emotional memory
Controls appetite and sleep patterns
Plays an important part in motivation
Limbic SystemOlfactory cortex is
responsible for the sense of smell
Amygdala is responsible for our feelings of fear
Hippocampus is responsible for declarative memory (things we know, like facts and figures, names)
The Diencephalon
• Consists of the thalamus and hypothalamus
Thalamus: has a role in emotion and memoryThe thalamus is an interpretation center for pain,
temperature, light touch and pressure.
Hypothalamus’: main function is homeostasis, or maintaining the body’s equilibrium.
THALAMUS• Thalamus – the structure in
the forebrain through which all sensory information (except smell) must pass to get to the cerebral cortex
• The thalamus also appears to play an active role in integrating information from various senses
HYPOTHALAMUS 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
The Four Lobes of the Cerebral Cortex
The Cerebral Cortex
• Your cerebral cortex is an intricate covering of interconnected neural cells that, like bark on a tree, forms a thin surface layer on your cerebral hemispheres.
• It is your body’s information processing center.
Lobes of the Brain
Frontal Lobes involved in speaking and muscle movements and in
making plans and judgments
Parietal Lobes include the sensory cortex
Occipital Lobes include the visual areas, which receive visual
information from the opposite visual field
Temporal Lobes include the auditory areas
Frontal Lobe
• Responsible for: reasoning some aspects of speech
planning organization movement problem solving attention creative thought personality impulse control
emotions physical reaction memory libido (sexual urges)
Occipital Lobe
Helps see light and objectsAllows us to recognize and identify things Aids color recognitionOccipital lobe on the right interprets visual
signals from the left visual spaceDamage to one occipital lobe will result in loss
of vision in the opposite visual field
Parietal Lobe
Concerned with cognition (thinking)Information processingPain and touch sensationSpatial orientationSpeechLanguage and visual perceptionReceives sensory information from other
areas of the brainUses memory to attach meaning to objects
Temporal Lobe
Assists us to tell one smell from another and one sound from another
Has a role in auditory and visual memoryThe right temporal lobe is involved in visual
memory (for pictures and faces)The left temporal lobe is involved with verbal
memory (words and names)
Brain Damage
• Damage to occipital lobe may result in cortical blindness.
• Parietal Lobe damage can result in disorders of perception such as:– Apraxia – inability to identify objects– Hemisomatognosia – unawareness of the
opposite side of the body to the damage– Phantom limb – sensations still present from an
amputated limb
Brain Damage
• Damage to the Temporal Lobe such as Wernicke’s Aphasia– People with this disorder loss their ability to
understand language– They may be able to speak clearly, but the words
make no sense – “word salad”– However, people with Wenicke’s aphasia are able
to comprehend non-verbal sounds and respond appropriately
Absolute Threshold• In neuroscience and psychophysics, an
absolute threshold is the smallest detectable level of a stimulus.
• The absolute threshold can be influenced by several different factors such as the subject's motivations and expectations, cognitive processes, and whether the subject is adapted to the stimulus
Vision
• The absolute threshold for vision was assessed in a landmark experiment by Hecht, Shlaer and Pirenne in 1942.
• Vision The amount of light present if someone held up a single candle 30 mi (48 km) away from us, if our eyes were used to the dark. If a person in front of you held up a candle and began backing up at the rate of one foot (30 cm) per second, that person would have to back up for 44 hours before the flame became invisible.
Hearing
• The absolute threshold of hearing is the minimum sound level of a pure tone that an average ear with normal hearing can hear with no other sound present. The absolute threshold relates to the sound that can just be heard by the organism.
• Hearing The ticking of a watch in a quiet environment at 20 ft (6 m).
Sense of Taste
• The absolute threshold for taste would be the minimum amount of the flavor that can be detected. For example: sweet, sour, and bitterness.
• Some people have more sensitivity to various flavors and this determines in some cases their likes and dislikes of certain foods.
Taste• Factors that influence taste: • Temperature• Description or presentation• Smell
• Five Basic Sensations of Taste
• Sweet • Sour • Salty • Bitter• Umami
Sense of Touch• One test that has been done with the
absolute threshold for touch is to allow very small items to fall on a person’s cheek.
• For most the lowest sense of touch that was observed was a bee’s wing dropped from the height of ½ inch.
• This value will vary considerably depending on the part of the body involved.
Sense of Smell
• Absolute threshold studies using sense of smell usually involve a scent, such as perfume per the size of the room.
• The smallest detectable scent is usually one drop of perfume for a six room apartment.
Broca’s Area
• This area of the brain controls language expression- an area of the frontal lobe, usually in the left hemisphere, that directs the muscle movements in speech.
Wernicke’s Area
• This area controls language reception.• A brain area involved in language
comprehension and expression, usually in the left temporal lobe.
How We Use Language
When you read aloud the words:1.Register the visual area.2.Are relayed to the angular gyrus, which
tranforms the words into auditory code.3.It is received and understood in Wernicke’s
area.4.Sent to Broca’s area5.Motor cortex produces the sound.
Aphasia• Aphasia is impairment of language, usually
caused by damage to the left hemisphere, either to Broca’s area or to Wernicke’s area.
• The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral.
• The central nervous system of vertebrates (such as humans) contains the brain, spinal cord, and retina.
• The peripheral nervous system consists of sensory neurons, clusters of neurons called ganglia, and nerves connecting them to each other and to the central nervous system. These regions are all interconnected by means of complex neural pathways.
Nervous Systems• Peripheral Nervous System (PNS) – is
made up of all those nerves that lie outside the brain and spinal cord
• Nerves – bundles of neuron fibers that are routed together in the PNS
• Somatic Nervous system (SNS) – is made up of nerves that connect to voluntary skeletal muscles and to sensory receptors.
Autonomic Nervous System
• Autonomic Nervous System (ANS) – is made up of nerves that connect to the heart, blood vessels, smooth muscles, and glands
• Sympathetic Division – is the branch of the ANS that mobilizes the body’s resources for emergencies.
• Parasympathetic Division – is the branch of the ANS that generally conserves bodily resources.
Neurons • Neurons send signals to other cells as electrochemical waves travelling along thin fibers called axons, which cause chemicals called neurotransmitters to be released at junctions called synapses.
• A cell that receives a synaptic signal may be excited, inhibited, or otherwise modulated.
• Motor neurons, situated either in the central nervous system or in peripheral ganglia, connect the nervous system to muscles or other effector organs.
• The interactions of all these types of neurons form neural circuits that generate an organism's perception of the world and determine its behavior.
Mirror Neurons
• A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another. Thus, the neuron "mirrors" the behavior of the other, as though the observer were itself acting.
• It is argued that mirror neurons may be important for understanding the actions of other people, and for learning new skills by imitation.
How the Nervous System and Endrocrine Systems Interact
• Hormones provide feedback to the brain to affect neural processing.
• Reproductive hormones affect the development of the nervous system.
• The hypothalamus controls the pituitary gland and other endocrine glands.
•The endocrine system is the system of glands, each of which secretes different types of hormone directly into the bloodstream (some of which are transported along nerve tracts to regulate the body
•Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct.
Principal functions of the endocrine system
• Maintenance of the internal environment in the body (maintaining the optimum biochemical environment)
• Integration and regulation of growth and development
• Control, maintenance and instigation of sexual reproduction, including fertilization, fetal growth and development and nourishment of the newborn
Endocrine System
Hormones• Like neurotransmitters,
they activate cells in the body.
• They affect both internal processes and visible behavior.
• Are secreted directly into the bloodstream or lymph system.
Behavioral EndocrinologyBehavioral Endocrinology
The study of the relationship between hormones and behavior
Hormones affect behavior and behavior feeds back to affect hormones
Hormones↔Behavior
Hormones DO NOT act like “faucets” in which behavior spews forth if the hormone spigot is open.
Hormone-behavior relationships are complex.
It is NOT appropriate to say that hormones “cause” behavior.
Rather, hormones change the probability that a particular behavior will be displayed in the appropriate social context – hormones simply influence behavior.
Hormones and Behavior
First endocrinology experiment
Berthold’s Experiment
1) Background: Naturalistic observations of changes in behavior and appearance of roosters with age and season.
2) Castrated 6 roosters.3) Re-implanted a testis in 2 roosters.4) Transplanted a testis from another bird in 2
roosters.5) Left 2 castrated roosters to develop into capons.
The Pituitary Gland
• A sort of master gland
• It is a cherry-sized endocrine gland
• The hormones it secretes affect the growth and secretion of other endocrine glands
• The real boss is the hypothalamus
ADRENAL GLANDSThe adrenal glands are the part of the body
responsible for releasing three different classes of hormones. These hormones control many important functions in the body, such as:
• Maintaining metabolic processes, such as managing blood sugar levels and regulating inflammation
• Regulating the balance of salt and water • Controlling the "fight or flight" response to
stress • Maintaining pregnancy • Initiating and controlling sexual maturation
during childhood and puberty
Fight or Flight Response
Psychological Correlates of Physiological processes
• Fight or Flight Response – believed to have evolved to help our ancestors prepare for sudden physical threats
• It prepares our bodies to either confront a threat or run away from it
Fight or Flight Behavior• In the human fight or flight response in prehistoric
times, fight was manifested in aggressive, combative behavior and flight was manifested by fleeing potentially threatening situations, such as being confronted by a predator.
• In current times, these responses persist, but fight and flight responses have assumed a wider range of behaviors.
• For example, the fight response may be manifested in angry, argumentative behavior, and the flight response may be manifested through social withdrawal, substance abuse, and even television viewing
Fight or Flight• More alert as circulatory
system diverts blood (full of oxygen) away from stomach and intestines towards the brain and skeletal muscles
• The liver releases sugar to make more energy available
• The body releases adrenaline which makes the heart beat faster and stronger
Epinephrine and Cortisol• Also known as adrenalin, epinephrine is a naturally
occurring hormone. • During the fight-or-flight response response, the
adrenal gland releases epinephrine into the blood stream, along with other hormones like cortisol,
-signaling the heart to pump harder, -increasing blood pressure, -opening airways in the lungs, -narrowing blood vessels in the skin and intestine to
increase blood flow to major muscle groups
Fight or Flight
• Bronchioles in the lungs dilate to bring in more oxygen
• Pupils of the eyes dilate to make vision sharper
• Mouths become dry as we produce less saliva• We perspire more as a means of cooling off
body as the increased arousal produces more heat in the body
Men versus Women• Males and females tend to deal with
stressful situations differently. Males are more likely to respond to an emergency situation with aggression (fight), while females are more likely to flee (flight), turn to others for help, or attempt to defuse the situation.
• During stressful times, a mother is especially likely to show protective responses toward her offspring and affiliate with others for shared social responses to threat.
