This Chapter introduces us to the biological bases of behavior. It covers: Genes and Evolution The structure and function of neurons in the brain and how they communicate The Nervous System The Structure of the Brain and its functions And the Endocrine System
The next few slides will be a basic review of the process of conception and the process involved in transmitting genes to the next generation. First is the FERTILIZATION process: The male sperm contains 23 chromosomes and the female egg contains an equal number of 23. When the sperm penetrates the egg at conception the fertilized egg is called a zygote. It contains 46 chromosomes arranged in 23 pairs that contain the basic blueprint for creating a human being.
A chromosome is a short, rod-like structure that contains the chemical DNA on tightly coiled structures.
These DNA coils are arranged in a long strand that looks like a twisted ladder with rungs.
A gene is a segment on the DNA strand that contains the instructions for making proteins that are the chemical building blocks that make build all the parts of a brain and body. Most genes have only one version, but about 1% of them are what we call “Polymorphic Genes” meaning they can carry more than one set of instructions - which helps to explain some of the variations we see in people.
A DOMINANT GENE is a polymorphic gene that determines the trait even if paired with a Recessive gene. A RECESSIVE GENE is one that will manifest a trait only if both parents have the gene. When it comes to eye color the dominant gene is for Brown Eyes. BTW…just a little side fact. Blue eyes are actually a genetic mutation of a portion of the gene that controls Melanin – it controls coloration in skin, hair, eyes etc. Only 10,000 years ago everyone had brown eyes… and then there was an anomaly that altered a small part of that gene, resulting in a fading of the iris turning it blue.
The Theory of Evolution was based on the revolutionary ideas and research of Charles Darwin in the mid 1800’s. It proposes that we as humans arose as a different species from a common ancestor millions of years ago. According to evolution theory we are the descendant s of a creature that split off from apes. We now have evidence that Darwin was not privileged to at that time…DNA testing actually shows that we are very closely related to Chimpanzees and share 98% of the same DNA. There are two forces at play in this process. 1-genetic mutations – which are accidental error in the genetic instructions (just like the mutation of the gene for eye color we just talked about). And the other is Natural Selection – which means that those organisms that are successful will continue to pass on their genes and insure the success of that species.
This is a view of the human brain from the top. It looks sort of like a walnut, with two clear halves, and it is scrunched and wrinkled in appearance. The two halves are connected by nerve fibers called the corpus collosum. It weighs about 3 lbs. and is a pinkish white color with the consistency of Jello. It is fueled by sugar (glucose) and has about one TRILLION cells that come in two forms: Glial cells and Neurons. We’ll look at those two groups individually…
The Glial cells are the most numerous – about 900 billion of the trillion cells are Glials (or astrocytes – meaning star shaped). Their main job is to support growing neurons, help insulate the neurons from electrical interference, and release chemicals needed by the neurons to grow and function. And we have recently discovered that some of them may even transmit electrical signals of their own, a function previously thought to be only carried out by Neurons.
Neurons account for the remaining 100 thousand or so brain cells. They are smaller in number put play a huge role in making your brain function. They transmit electrical signals at speeds up to 200 MPH – ZOOM! One of the main differences between Glial cells and Neurons is the fact for the most part (there may be a few exceptions) Neurons are not able to reproduce the way Glial cells do. The Neurons you are born with will pretty much have to keep you going for your life. So guard them carefully – your ability to learn and remember new things depends of having ample Neurons in good working order. The research (although highly controversial) being done with Stem Cells that can facilitate the growth of new Neuron cells holds promise for repairing damage from strokes or accidents or diseases such as Alzheimers’ and Parkinsons. This animation defines the parts and the functions of a Neuron and the process called an Action Potential explaining how they “fire”.
A REFLEX is an unlearned, involuntary reaction some stimulus. It is “pre-wired” by genetic instructions, but although the reaction is spontaneous and immediate without having to give conscious thought to it, there is still a sequence of neural connections that take place as you can see in this graphic. First comes the sensor…in this case a hot light bulb on the skin. Next the afferent neurons carry the “pain” information to the spinal cord, then it goes to a second neuron called the Interneuron that serves as a sort of relay station before sending it on to the Efferent Neuron, or motor neurons that take the information from the spinal cord to the other parts of the body and causes a response to the pain stimulus…resulting in the reflexive reaction of pulling away. Reflexes have evolved over millions of years to protect our bodies from harm and injury, and they also help regulate heart rate, breathing, and blood pressure.
The Brain and Spinal Cord are the Central Nervous System – or CNS. If the spinal cord is severed it cannot be repaired and paralysis is experienced from the point of injury down. A person with lower limb paralysis is known as a paraplegic and if the upper limbs are affected it is called quadriplegia.
The Peripheral Nervous System, or the PNS is made up of all the nerves that come out of the spinal cord. If an injury is experienced in the PNS – unlike the one in the spinal cord, it may be able to be reversed. If a severed limb is reattached in time the nerves may regrown and sensation and use of the limb can be restored.
The PNS has two subdivisions: the Somatic Nervous System and the Autonomic Nervous System. The Somatic system controls voluntary movements. The Autonomic System has two more subdivisions: The Sympathetic Division is activated by the presence of danger and the “fight or flight” response kicks in, and the Parasympathetic Division restores the body to a calm state once the threat has passed.
Modern technology has enabled researchers to view the functions of the brain in ways never before possible. MRI or Magnetic Resonance Imaging passes non-harmful radio waves through the brain, and a computer measures the signals which are transformed into detailed images showing the structure of the brain.
A newer version of the MRI is called an fMRI – the f stands for functional. It can measure the activity of specific neurons that are in use during a specific cognitive task.
A PET scan, or Positron Emission Tomography is used by injecting a radioactive solution into the blood stream and then measuring the amount that is absorbed by the brain. It shows activity by different colors, the red and yellow colors indicate strong activity and the blues and greens indicate minimum activity.
An EEG or electroencephalograph involves attaching electrodes to the scalp to provide information about brain-wave activity.stands for functional. It can measure the activity of specific neurons that are in use during a specific cognitive task.
Stem cells are cells found in an embryo at a very early stage of development. At this stage differentiation (dedication to a particular organ) has not yet occurred, and these cells if transplanted have the capacity to become any one of the 220 types of cells in the human body. The possibilities for treating diseases and injuries is extremely promising with this technique, but it is a very controversial and highly politicized topic and funding for research is very limited.
It is possible to transplant stem cells into a precise location in the brain by using a Sterotaxic Procedure. The patients head is placed in a holder to keep it stable and a small hole is drilled into to the skull so a long needle can be inserted and the stem cells injected from a syringe.
Deep Brain Stimulation - DBS – is a surgical procedure where electrodes are implanted into specific areas of the brain, the electrodes are attached to an electrical stimulator that the patient can operate with a remote control. It can be effective in alleviating symptoms in some neurological diseases such as Parkinson’s.
This graphic shows a side view of one hemisphere. The forebrain is the largest part of the brain. It is the executive of the brain in charge of many higher cognitive functions and is especially responsible for judgment and decision-making. The Midbrain houses the reward or pleasure centers. It also contains the reticular formation that arouses the forebrain to process sensory information.
The Hindbrain has three structures: the pons, medulla and cerebellum. The video gives us a closer look at their functions.
The Cortex as mentioned earlier is very wrinkled into convolutions that enable a large surface area to fit into a small container like the human skull. The video gives us a better view.
The Cortex is divided into four separate parts called LOBES. The FRONTAL lobe is involved with personality, some emotions and motor movement. If it is damaged it can result in drastic personality changes. The PARIETAL lobe is involved with sensory experiences and perceptions. The OCCIPITAL lobe is involved in processing visual information. And the TEMPORAL lobe is involved with hearing and speaking. Keep in mind that each hemisphere has these four lobes for a total of eight lobes.
The Motor Cortex is a narrow strip located in the frontal lobe. It initiates voluntary movements. The larger the body part, the larger area is assigned to it, and each body part has its own specific location.
The somatosensory Cortex is located in the Parietal lobe. It processes sensory information about touch, location of limbs, pain, and body temperature and regulates the sensitivity of all your body parts. This is why your lips are more sensitive than your elbows.
Wernicke’s area and Broca’s area are located in the Temporal lobes that you recall are responsible for hearing and speech and also for understanding verbal and written material. If there is damage to Wernecke’s area, called Aphasia it becomes difficult to understand spoken or written words and to speak in meaningful sentences. Broca’s aphasia results in the inability to speak fluently but they can still understand written and spoken words. This animation shows the differences in the two types of Aphasia.
The Visual Association Area is located in the Occipital lobe and transforms basic visual sensations into meaningful visual objects. If problems occur in the process it can result in someone not being able to recognize an object as a whole and in the case of Visual Agnosia, the person cannot recognize some object, person, or color, but can still see and even describe the pieces or parts of an object.
The Limbic system is often referred to as our primitive or reptilian brain because similar structures are seen the brains of animals that are evolutionarily very old, such as alligators. This video will outline and give us a closer view of the Limbic systems’ parts and functions.
The two hemispheres of the brain are joined together by fibers that allow both sides to communicate with each other. The right hemisphere controls the left side of the body and vice versa. Sometimes in cases of extreme Epilepsy the only way to control the violent seizures is to severe the corpus collosum but it leaves each hemisphere to operate on its own which can result in communication problems.
The endocrine system is another system the body has for sending signals to help the body operate. It is made up of numerous glands that secrete chemicals called hormones. They have a very strong influence on the body. The Hypothalamus in the brain is the control central for the activity of the glands. The pituitary gland is located just below the hypothalamus and controls the growth rate of an individual as well as activating the other glands. The Thyroid, located in the neck regulates the body’s metabolism. The Adrenal glands regulate sugar and salt balance, and are also involved in development of secondary sexual characteristic. The Gonads produce hormones that regulate the sexual development and growth of the primary sex organs. In males the testes produce testosterone, and in females the ovaries produce estrogen and progesterone.
In order to have the linked videos and animations play correctly in this presentation, you will need to have the latest version of QuickTime and Flash Player installed on your computer.> QuickTime is a free installation that can be downloaded from http://www.apple.com/quicktime/download/> Flash Player is a free installation that can be downloaded from http://get.adobe.com/flashplayer/> Playing videos: QuickTime will need to be set as the default program to run .mov files on your computer and will open the video in a new window when the play icon is clicked in “Slide Show Mode”> Playing interactive animations: Your internet browser will need to be set as the default program to run .swf files on your computer and will open in a web browser window
2.1 Introduction2.2 Genes and Evolution L02 Describe the structures and processes involved in genetic transmission L03 Articulate the forces believed to be responsible for the evolution of the human brain and describe the relevance of the theory of evolution in how psychologists conduct research today2.3 Neurons: Structure, Function, and Communication2.4 Nervous System2.5 Studying the Living Brain2.6 Brain: Structures and Functions2.7 Endocrine System
Overview of Genes: Conception Sperm Egg Zygote2.2 Genes and Evolution
Chromosomes Each cell of the human body contains 46 chromosomes arranged in 23 pairs.2.2 Genes and Evolution
DNA Each rung of the DNA ladder is made up of four chemicals. The order in which the four different chemicals combine to form rungs creates a microscopic chemical alphabet.2.2 Genes and Evolution
Genes and Proteins and Polymorphic Genes On each chromosome are specific segments that contain particular instructions. In the chromosome on the left, each segment represents the location of a gene.2.2 Genes and Evolution
Dominant and Recessive Genes Child Father D D Mother D Sperm r Egg Brown eyes Zygote D r D r Brown eyes Zygote Sperm Sperm Egg Brown eyes Egg Zygote Brown eyes Zygote r r Sperm Egg Blue eyes Zygote2.2 Genes and Evolution
Evolution of the Human Brain2.2 Genes and Evolution
2.1 Introduction2.2 Genes and Evolution2.3 Neurons: Structure, Function, and Communication L04 Identify the main functions of glial cells L05 Identify the various parts of the neuron and explain how a neuron functions2.4 Nervous System2.5 Studying the Living Brain2.6 Brain: Structures and Functions2.7 Endocrine System
Structure of the Brain Front Left Right Back2.3 Neurons: Structure, Function, and Communication
Glial Cells Dendrites Cell body2.3 Neurons: Structure, Function, and Communication
Neurons Signals travel away from the cell body, down the axon. Axon Myelin sheath Glial cell End bulbs2.3 Neurons: Structure, Function, and Communication
Reflex Responses Efferent, or 1. Sensors motor, neuron 3. Interneuron makes Afferent, or connections between sensory, neuron neurons, which carry message to the brain. 2. Afferent, or sensory, neuron 4. Efferent, or motor, neuron carries neural messages carries neural messages from hand to spinal cord. from spinal cord to hand.2.3 Neurons: Structure, Function, and Communication
2.1 Introduction2.2 Genes and Evolution2.3 Neurons: Structure, Function, and Communication2.4 Nervous System L09 Differentiate between the nerves and neurons L10 Classify the major divisions and subdivisions of the nervous system L11 Differentiate the functions of the major divisions and subdivisions of the nervous system2.5 Studying the Living Brain2.6 Brain: Structures and Functions2.7 Endocrine System
Central Nervous System The spinal cord is made up of neurons and bundles of axons and dendrites that carry information back and forth between the brain and the body.2.4 Nervous System
Peripheral Nervous System Nerves carry information from the senses, skin, muscles, and the body’s organs to and from the spinal cord.2.4 Nervous System
Subdivisions of the PNS Somatic Nervous System Autonomic Nervous System Sympathetic Parasympathetic Division Division2.4 Nervous System
2.1 Introduction2.2 Genes and Evolution2.3 Neurons: Structure, Function, and Communication2.4 Nervous System2.5 Studying the Living Brain L12 Describe the different technologies used to investigate the brain L13 Describe experimental procedures to treat the brain2.6 Brain: Structures and Functions2.7 Endocrine System
MRI: Magnetic Resonance Imaging Brain damage2.5 Studying the Living Brain
fMRI: Functional Magnetic Resonance Imaging fMRI scans can map activities of neurons that are involved in various cognitive functions.2.5 Studying the Living Brain
PET Scan: Positron Emission Tomography The red and yellow colors indicate strong activity and the blues and greens indicate minimum activity.2.5 Studying the Living Brain
EEG: ElectoencephalographElectrodes measure theactivity of specific neuronsthat are in use during aspecific cognitive task.2.5 Studying the Living Brain
Stem Cells Click on play button to launch video in QuickTime player.2.5 Studying the Living Brain
Stereotaxic Procedure2.5 Studying the Living Brain
DBS: Deep Brain Stimulation2.5 Studying the Living Brain
2.1 Introduction2.2 Genes and Evolution2.3 Neurons: Structure, Function, and Communication2.4 Nervous System2.5 Studying the Living Brain2.6 Brain: Structures and Functions L14 Identify and locate the major parts of the brain, and state their functions L15 Identify and locate the four lobes in the cerebral cortex, and state their key functions L16 Identify and locate key structures in the limbic system, and state their functions L17 Identify sex differences in the brain L18 Describe the lateralization of brain functions2.7 Endocrine System
Major Parts of the Brain: The Forebrain and Midbrain Forebrain Midbrain Cerebellum Pons Medulla2.6 Brain: Structures and Functions
Major Parts of the Brain: The Hindbrain Click on play button to launch video in QuickTime player.2.6 Brain: Structures and Functions
The Cortex Click on play button to launch video in QuickTime player.2.6 Brain: Structures and Functions
Four Lobes Frontal Parietal Occipital Temporal2.6 Brain: Structures and Functions
Motor Cortex e e n K p i H Tr k n u Sue Eo hldr lbw o Ankle W rs it Toes Han Litt le d Mid Rin d g Ind le Thu ex Bro m w Ne b Eye c lid a k Fac nd e e yeb Lips all Jaw ue ing g w Ton wallo S2.6 Brain: Structures and Functions
Somatosensory Cortex p i H g e L Tr Nk a u n e d k c Soldr hue H e Foot A o rm w Eb l Toes Ws Hnd ittle ri t a Frer oam als Genit L Mid Rin d g Ind le Thu ex Eye mb Nos e Fac Upper e lip Lips Lower lip Teeth, gums, and jaw Tongue2.6 Brain: Structures and Functions
Broca’s and Wernicke’s Aphasia Frontal lobeBroca’sFrontal Lobe (speaking) area Temporal Lobe (understanding) Wernicke’s area Broca’s Area Wernicke’s Area Temporal speech Produces Understands sentences I am working as a nurse lobe What are you doing in this hospital? at this hospital. “I have been working as a nurse in this hospital.”2.6 Brain: Structures and Functions
Visual Association Area Occipital lobe2.6 Brain: Structures and Functions
The Limbic System Click on play button to launch video in QuickTime player.2.6 Brain: Structures and Functions
Split Brain2.6 Brain: Structures and Functions
2.1 Introduction2.2 Genes and Evolution2.3 Neurons: Structure, Function, and Communication2.4 Nervous System2.5 Studying the Living Brain2.6 Brain: Structures and Functions2.7 Endocrine System L19 Locate and describe the key elements of the endocrine system L20 Discuss some ways that hormones regulate behavior
The Endocrine System Hypothalamus Thyroid Heart Adrenal glands Pancreas Ovaries Testes2.6 Brain: Structures and Functions