Biology & BehaviorModule 3

• Neural Communication

• Nervous System

• Endocrine System

Why is biology important to psychology?

• Everything psychological is simultaneously biological.

• Franz Gall believed that the bumps on the skull revealed an individual’s character, traits and mental abilities. Also known as phrenology.

• Gall’s Phrenology was wrong about the bumps revealing someone’s character, but his idea that different parts of the brain control different parts of our behavior was correct.

http://www.artsci.wustl.edu/~mjstrube/psy315/phrenology.jpg

• In our body we have nerve cells that conduct electricity (a form of communication). This electrical impulse sends chemical messages (deciphered by the brain) that communicates to our body what to do (think, feel, move, react, etc.). This is how we construct our experiences and this is the connection between psychological events and biological activity.

• Biological psychologists are those who study the links between psychological events and biological activity. They are also known as neuropsychologists, physiological psychologists and behavior geneticists.

Neural Communication

• The information system of the body is made up of interconnected neurons.

• Our body is made of trillions of tiny cells. These tiny cells make up organs, which in turn make up body systems such as the digestive system.

• Because the nervous system and the brain of humans and animals are similar, scientists are able to experiment on animals to find how our neural system works.

Neurons

• Each neuron has a cell body and branching fibers.

• The neuron is a nerve cell, which is the basic foundation of the nervous system.

• Dendrites are the bushy, branchy extensions of a neuron that receive messages and conduct impulses toward the cell body.

• The axon is the extension of a neuron. The messages must travel through the axon in order to be passed on to other neurons.

www2.cedarcrest.edu/.../tetanus-neuron.gif

The myelin sheath is a layer of fatty tissue. It is due to the myelin sheath that impulses can be transmitted so quickly. (The myelin sheath bundles the fibers, allowing no gaps or stops of transmitted messages).

• Multiple sclerosis is when the myelin sheath degenerates. It leads to the loss of muscle control.

http://www.enchantedlearning.com/subjects/anatomy/brain/gifs/Neuron.GIF

• Neural impulses travel at about 2 to 200 miles per hour.

• How an impulse travels: A neuron fires an impulse when it receives signals from sensory receptors, (via chemical stimulation). Messages from neighboring neurons generate electricity from the chemical events. The exchange of electrical charge that travels down the axon is also known as ion exchange.

Show Action Potential Clip: http://www.youtube.com/watch?v=SCasruJT-DU

http://docushare.harford.edu/dsweb/GetRendition/Document-233067/html/

index199321.jpg

• The action potential is the neural impulse, the brief electrical charge that travels down the axon. It is generated by the movement of positively charged atoms in and out of channels in the axon’s membrane.

• The resting potential is the state when the fluid interior of the axon has an excess of negative ions and the fluid outside of the axon has positive ions.

• The axon’s surface is selectively permeable, it may block certain ions.

http://cwx.prenhall.com/bookbind/pubbooks/morris5/medialib/images/F02_02.gif

• The ions get through the axon through several steps.– Once a neuron fires, the axon will be open to

positively charged sodium ions.– The axon is then depolarized. The next part of the

axon will open, leading other parts of the axon to open as well. (chain reaction)

– The Refractory period is also known as the resting pause when the neuron pumps the positively charged sodium ions back outside of the membrane.

– In myelinated neurons, the action potential will speed up by hopping from one myelin to the other.

http://kvhs.nbed.nb.ca/gallant/biology/saltatory_conduction.jpg

• There are two different types of signals, the inhibitory and excitatory.

• The excitatory can be compared to pushing the accelerator, while the inhibitory could be compared as pushing the brake.

• The threshold is the required level of stimulation to trigger a neural response.

• The action potential transmits down the axon, which branches into junctions with 100’s and 1000’s of other neurons, then to the muscles and glands.

• Increasing the stimulus above the threshold will not increase the action potential’s intensity. Also known as the ‘all or none’ response.

• Strong stimulus could trigger more neurons to fire; it will not affect the action potential’s strength or speed.

How Neurons communicate

• The axon terminal of one neuron is separated from the receiving neuron by a gap, either called a synaptic gap or a cleft.

• Dendrites and axons do not touch.• Neurotransmitters are chemical messengers that

extend across the synaptic gaps between the neurons. When released by the sending neuron, neurotransmitters travel across the synapse and binds to receptor sites on the receiving neuron, showing that it may influence whether a neuron will generate a neural impulse.

• Reuptake is when the neurotransmitters are reabsorbed by the sending neuron.

• The neurotransmitter molecule across the synaptic gap binds to the receptor sites on the receiving neuron. The neurotransmitter unlocks tiny channels at the receiving site, then allows ions to enter the receiving neuron.

http://www.memorydr.com/images/alz13.jpg

Show the Schwann cell and action potential clip: http://www.youtube.com/watch?v=DJe3_3XsBOg

How neurotransmitters influence us

• A particular neural pathway in the brain may use only 1 or 2 neurotransmitters and these neurotransmitters may have an effect on our emotions and motions and behavior.

• Acetylcholine (ACh) is the messenger at every junction between a motor neuron and skeletal muscle. Enables muscle action, learning and memory. Muscle contracts when ACh is released to the muscles and it can not contract if ACh is blocked from the muscles.

• Morphine binds to receptors linked to mood and pain sensations.

• This lead to the discovery of endorphins, natural opiate like neurotransmitters linked to pain control and pleasure.

• Endorphins explains the ‘runners high’

• Show Clip: Brains Natural Morphine – Endorphins: http://www.youtube.com/watch?v=QWcfTGIU2Hs

How drugs and other chemicals alter neurotransmission

• When artificial opiates reach the brain, the brain will stop producing it’s own opiates. Once the natural opiates are suppressed, one may feel unpleasant lingering after affects.

• Agonist (excites) molecules are similar to neurotransmitters and may mimic it’s effects or it may block the neurotransmitter’s reuptake.

• The venom of a Black widow spider disperses ACh to the synapses, causing violent muscle contractions. Some opiate drugs produce a temporary high by amplifying normal sensations of arousal or pleasure.

Antagonist (inhibit) molecules block the ACh release from the sending neuron, it may cause paralysis. It could occupy the receptor site, but can not stimulate the receptor.

http://www.memorydr.com/images/alz13.jpg

• Curare (a poison used by South American Indians applied to dart tips) and Botulin (a poison formed in improperly canned food) are two poisons which are antagonists. They cause paralysis by blocking ACh.

• Neurotransmitter research is leading to drugs which decrease the effects of depression, schizophrenia and other disorders.

• Blood brain barrier allows the brain to ‘fence out’ unwanted chemicals circulating in the blood.

• L-dopa can be used to pass the blood brain barrier. The brain can convert this material to dopamine, while raw dopamine is blocked from the blood stream.

The Nervous System

• The nervous system is the electrochemical information network.

• The Central Nervous System (CNS) includes the brain and spinal cord.

• The Peripheral Nervous System (PNS) links the nervous system with the sense receptors, muscles and glands.

• Nerves are the axons which carry the PNS information.

http://www.bryanedwards.com/products/detail/images/poster-nervous.jpg

• There are three types of neurons– Sensory Neurons- send information from the body’s

tissues and sensory organs to the spinal cord of the central nervous system, which then process the information.

– Motor Neurons- carry outgoing information from the Central Nervous System (CNS) to the muscles and glands.

– Interneurons- The Central Nervous system neurons, which internally communicates and intervenes between the sensory outputs and the motor neurons.

The Peripheral Nervous System

• Includes the somatic and autonomic nervous system.

• The somatic nervous system controls the voluntary controls of the skeletal muscles. It triggers the muscles to move.

• The autonomic nervous system controls the glands and muscles of internal organs. It influences heartbeat, digestion and glandular activity.

• The autonomic system has two parts. The Sympathetic and Parasympathetic.

http://visual.merriam-webster.com/images/human-being/anatomy/nervous-system/peripheral-

nervous-system.jpg

http://universe-review.ca/I10-13-nerves2.jpg

• The sympathetic nervous system will accelerate your heartbeat and blood sugar, slow down digestion, cool with perspiration and alerts you to any action when something alarms, enrages or challenges your body. (fight or flight)

• Lie detectors measure such arousals that are caused by the autonomic system.

• The parasympathetic nervous system conserves energy, while calming down an individual by lowering the heartbeat and blood sugar.

http://abdellab.sunderland.ac.uk/Lectures/Parmacology/Pics/anatomy/PNS.GIF

The Central Nervous System

• The spinal cord connects the Peripheral Nervous System to the brain.

• Ascending neural fibers send up sensory information while descending fibers send down motor control information.

• Reflexes are a simple, automatic response to sensory stimuli. ( like the Knee Jerk Response)

http://www.faqs.org/health/images/uchr_02_img0126.jpg

Reflexes

• A simple spinal reflex pathway contains a single motor neuron and one sensory neuron.

• Reflexes work by communicating between a sensory and motor neuron. Interneurons respond by activating motor neurons.

• You will experience a reflex action before you feel pain. This is because this pathway runs directly through the spinal cord (the CNS) and out (unlike the sensory pathway – the PNS).

http://www.merck.com/media/mmhe2/figures/MMHE_06_077_01_eps.gif

http://homepage.mac.com/mehu2000/CSMU/Tortora/figures/Ant%20lat

%20pathway.jpg

Endocrine System

• The endocrine is the body’s slow chemical communication system. It consists of a set of glands that secretes hormones into the blood stream.

• Hormones are chemical messengers, manufactured by the endocrine glands. They are produced in a tissue and later affects another. They are chemically identical to neurotransmitters and are very slow. The effects however outlast the effects of the neural messages.

http://www.web-books.com/eLibrary/Medicine/Physiology/Endocrine/endocrine_system.jpg

• The autonomic nervous system stimulates the adrenal glands (i.e. in a perceived dangerous situation) which release epinephrine and nor epinephrine. It is located on the top of the kidneys and provides us with energy by increasing the heart rate, blood pressure and sugar.

• The pituitary gland is located in the brain, and is controlled by the hypothalamus. It releases hormones that influences growth and also influences the release of hormones of other endocrine glands. Also known as the ‘master gland’.

• The feedback system: Brain->Pituitary->other glands->hormones->Brain, explains the connection between the nervous system and endocrine system -> the nervous system directs the endocrine secretions, which then affect the nervous system. (The brain conducts and coordinates the entire process.)