BIOLOGICAL BASES OF BEHAVIOR

THE HUMAN BRAIN

The influence of biology (sometimes called the neuroscience or biopsychological perspective) is growing.  Some researchers predict that someday psychology will be a specialty within the field of biology.  An understanding of the biological principles relevant to psychology is needed to understand current psychological thinking.

The human brain consists of three major divisions; hindbrain, midbrain, and forebrain

Brain Structure

Hindbrain- structures in the top part of the spinal cord, controls basic biological functions that keep us alive. Medulla- controls blood pressure, heart rate, and breathing Pons- connects the hindbrain with the mid and forebrain, also involved in the control of facial expressions Cerebellum- portion of the lower brain that coordinates and organizes bodily movements for balance and accuracy. 2    Midbrain-between the hind and forebrain, coordinates simple movements with sensory information. Forebrain- controls what we think of as thought and reason. Thalamus- portion of the lower brain that functions primarily as a central relay station for incoming and outgoing messages from the body to the brain and the brain to the body Hypothalamus- portion of the lower brain that regulates basic needs (hunger, thirst) and emotions such as pleasure, fear, rage, and sexuality Amygdala and Hippocampus- two arms surrounding the thalamus, important in how we process and perceive memory and emotion

NOTE: The three parts above are grouped together and called the limbic system because they all deal with aspects of emotion and memory.
What is a Neuron?
A neuron is a nerve cell. The brain is made up of about 100 billion neurons.
Neurons are similar to other cells in the body in some ways such as:

1. Neurons are surrounded by a membrane.
2. Neurons have a nucleus that contains genes.
3. Neurons contain cytoplasm, mitochondria and other "organelles".

However, neurons differ from other cells in the body in some ways such as:

1. Neurons have specialized projections called dendrites and axons. Dendrites bring information to the cell body and axons take information away from the cell body.
2. Neurons communicate with each other through an electrochemical process.
3. Neurons form specialized connections called "synapses" and produce special chemicals called "neurotransmitters" that are released at the synapse.

It has been estimated that there are 1 quadrillion synapses in the human brain. That's 1015 or 1,000,000,000,000,000 synapses! This is equal to about a half-billion synapses per cubic millimeter. (Statistic from Changeux, J-P. and Ricoeur, P., What Makes Us Think?, Princeton: Princeton University Press, 2000, p. 78)
How big is the brain? How much does the brain weigh?
The adult human brain weighs between 1300 g and 1400 g (about 3 lbs). A newborn human brain weighs between 350 and 400 g. For comparison:
elephant brain = 6,000 g
chimpanzee brain = 420 g
rhesus monkey brain = 95 g
beagle dog brain = 72 g
cat brain = 30 g
rat brain = 2 g
The picture to the right is a human brain.

 

 

 

 

 

 

 

 

(Image provided by Dr. Wally Welker, Univ. of Wisconsin Brain Collection)
Ways of studying the brain: Accidents, Lesions, Electroencephalogram, Computerized axial tomography, Magnetic resonance imaging (MRI), Positron emission tomography, Functional MRI, Neuroanatomy

 

Neuron – a nerve cell, which transmits electrical and chemical information throughout the body
dendrite- part of the neuron that receives information from the axons of other nerve cells
Axon- part of the neuron that carries messages away from one neuron to the dendrites of another Cell body, or soma- contains the nucleus and other parts of the cell needed to sustain its life
Myelin sheath- a fatty covering around the axon that speeds neural impulses
Terminal buttons- the branched end of the axon that contains neurotransmitters
Vesicles – bubblelike containers of neurotransmitters, located at the end of an axon
Neurotransmitters-– chemicals in the endings of nerve cells that send information across the synapse
Acetylcholine – neurotransmitter that regulates basic bodily processes such as movement
Dopamine – a neurotransmitter involved in the control of bodily movements ( involved in  Parkinson’s disease, and Alzheimer’s)
Endorphins – neurotransmitters that relieve pain and increase our sense of wellbeing
Serotonin- mood control
Synapse- the junction point of two or more neurons; a connection is made by neurotransmitters.

Action potential
All-or-none principle
Afferent neurons, or sensory neurons
Interneurons
Efferent neurons, or motor neurons

Central nervous system- brain and spinal cord
Peripheral nervous system- - all other nerves
Somatic nervous system- controls voluntary movements
Autonomic nervous system- controls involuntary movements
Sympathetic nervous system- speeds things up- prepares body for fight or flight
Parasympathetic nervous system-- brings the body back to normal
Cerebral cortex- covers the lower brain and controls mental processes such as thought
Frontal lobes-– contains the motor strip and frontal association area
Frontal association area – plays an important part in integrating personality and in forming complex thoughts
Motor strip- band running down the side of the frontal lobe that controls all bodily movements
Parietal lobes -– area that contains the sensory strip
Sensory strip- band running down the side of he parietal lobe that registers and provides all sensation
Occipital lobes- area that interprets visual information
Temporal lobes- area responsible for hearing and some speech functions
Lobe- major division of the brain  
Hemispheres- one-half of the two halves of the brain; controls the opposite side of the body

Brain lateralization 
Corpus callosum - bundle of nerve fibers that transfers info. From one hemisphere to the other
Fissure- a lengthy depression marking off an area of the brain
Reticular activating system- the alertness control center of the brain that regulates the activity level of the body
Split-brain
Brain plasticity
Endocrine system – system of all the glands and their chemical messages taken together
Hormones – chemical regulators that control bodily processes such as emotional responses, growth, and sexuality

Pituitary gland – the master gland of the body that activates other glands and controls the growth hormone
Growth hormone – hormone that regulates the growth process
Thyroid gland – controls and regulates the speed of bodily processes called metabolism
Metabolism – the speed at which the body operates of the speed at which it uses up energy
Adrenal glands – glands that release the hormone that causes excitement in order to prepare the body for an emergency
Adrenaline – chemical that prepares the body for emergency activity by increasing blood pressure, breathing rate, and energy level

 

BIOLOGICAL BASIS OF BEHAVIOR QUIZ

1.   Blindness could result from damage to which cortex and lobe of the brain?

1. visual cortex in the frontal lobe
2. visual cortex in the temporal lobe
3. sensory cortex in the parietal lobe
4. visual cortex in the occipital lobe
5. cerebral cortex in the occipital lobe

2.   Paralysis of the left arm might be explained by a problem in the

1. motor cortex in the frontal lobe in the left hemisphere.
2. Motor cortex in the frontal lobe in the right hemisphere.
3. Sensorimotor cortex in the temporal lobe in the left hemisphere.
4. Motor cortex in the parietal lobe in the left hemisphere.
5. Motor cortex in the occipital lobe in the right hemisphere.

3.   Deafness can result from damage to the inner ear or damage to what area of the brain?

1. Connections between the auditory nerve and the auditory cortex in the frontal lobe.
2. Connections between the auditory nerve and the auditory cortex in the temporal lobe.
3. Connections between the areas of the sensory cortex that receive messages from the ears and the auditory cortex.
4. Connections between the hypothalamus and the auditory cortex in the temporal lobe.
5. Connections between the left and right sensory areas of the cerebellum.

4.   According to the theory of evolution, why might we call some parts of the brain the old brain and some parts of the new brain?

1. Old brain parts are what exist in very young children, and the new brain develops later
2. The old brain developed first according to evolution.
3. The old brain becomes more active as we grow older.
4. The new brain deals with new information, while the old brain deals with information gathered when we were children.
5. The old brain is most affected by age deterioration (dementias) while the new brain remains unaffected.

5.   Which chemicals pass across the synaptic gap and increase the possibility the next neuron in the chain will fire?

1. synaptic peptides                               D.        excitatory neurotransmitters
2. inhibitory neurotransmitters              E.        potassium and sodium
3. adrenaline-type exciters

6.   You eat some bad sushi and feel that you are slowly losing control over your muscles.  The bacteria you ingested from the bad sushi most likely interferes with the use of

1. Serotonin                                D. thorazine   
2.  Dopamine                              E. adrenaline
3. acetylcholine

7.         The three major categories researchers use to organize the entire brain are the

1. old brain, new brain, and cerebral cortex
2. lower, middle, and upper brain.
3. Hindbrain, midbrain, and forebrain.
4. Brain stem, limbic system, and cerebral cortex
5. Neurons, synapses, and cerebral cortex.

8.   A spinal reflex differs from a normal sensory and motor reaction in that

1. a spinal reflex occurs only in response to extremely stressful stimuli.
2. In a spinal reflex, the spine moves the muscles in response as soon as the sensory information reaches the spine while usually the impulse must reach the brain before a response.
3. In a normal sensory/motor reaction, the spine transmits the information through afferent nerve fibers, while reflex reactions are transmitted along special efferent nerves.
4. Spinal reflexes are part of the central nervous system response, while normal sensory/motor reactions are part of the peripheral nervous system.
5. Spinal reflexes occur only in animals because humans are born without instinctual responses.

9.   Antidepressant drugs like Prozac are often used to treat mood disorders.  According to what you know about their function, which neurotransmitter system do these types of drugs try to affect?

1. serotonin
2. adrenaline
3. acetylcholine
4. endorphins
5. morphine

10. Which sentence most closely describes neural transmission?

1. An electric charge is created in the neuron, the charge travels down the cell, and chemicals are released that cross the synapse to the next cell.
2. A chemical change occurs within the cell, the change causes an electric charge to be produced, and the charge jumps the gap between the nerve cells.
3. The electric charge produced chemically inside a group of neurons causes chemical changes in surrounding cells.
4. Neurotransmitters produced in the hindbrain are transmitted to the forebrain, causing electric changes in the cerebral cortex.
5. Neural transmission is an electrochemical process both inside and outside the cell.

11. Dr. Dahab, a brain researcher, is investigating the connection between certain environmental stimuli and brain processes. Which types of brain scans is he most likely to use?

1. MRI and CAT
2. CAT and EKG
3. PET and EEG
4. EKG and CAT
5. Lesioning and MRI

12. Split-brain patients are unable to

1. coordinate movements between their major and minor muscle groups.
2. Speak about information received exclusively in their right hemisphere.
3. Speak about information received exclusively in their left hemisphere.
4. Solve abstract problems involving integrating logical (left-hemisphere) and spatial (right hemisphere) information.
5. Speak about information received exclusively through their left ear, left eye, or left side of their bodies.

13. When brain researchers refer to brain plasticity , they are talking about

1. the brain’s ability to regrow damaged neurons.
2. The surface texture and appearance caused by the layer known as the cerebral cortex.
3. The brain’s versatility caused by the millions of different neural connections.
4. Our adaptability to different problems ranging from survival needs to abstract reasoning.
5. New connections forming in the brain to take over for damaged sections.

14. Mr. Spam is a 39-year-old male who has been brought into your neurology clinic by his wife.  She has become increasingly alarmed by her husband’s behavior over the last four months.  You recommend a CAT scan to look for tumors in the brain.  Which two parts of the brain would you predict are being affected by the tumors?  List of symptoms: vastly increased appetite, body temperature fluctuations, decreased sexual desire, jerky movements, poor balance when walking and standing, inability to throw objects, and exaggerated efforts to coordinate movements in a task
A.  motor cortex and emotion cortex
B.  motor cortex and hypothalamus
C.  hypothalamus and cerebellum
D.  cerebellum and medulla
E.  thalamus and motor cortex

15. In most people, which one of the following is a specific function of the left hemisphere that is typically not controlled by the right hemisphere?

1. producing speech
2. control of the left hand
3. spatial reasoning
4. hypothesis testing
5. abstract reasoning