The Nervous System and The Nervous System and The BrainThe Brain

Neuroscience and BehaviorNeuroscience and BehaviorModules 3 & 4Modules 3 & 4

Early Theories - PhrenologyEarly Theories - Phrenology- Bumps on the skull tell - Bumps on the skull tell us nothing us nothing about the about the brain’s underlying brain’s underlying functions functions - Some assumptions - Some assumptions were true…were true…different different parts of the brain DO parts of the brain DO control different parts of control different parts of behaviorbehavior

The Nervous SystemThe Nervous System An electrochemical communication An electrochemical communication

system that enables us to think, feel system that enables us to think, feel and actand act

How do we study the Nervous How do we study the Nervous System?System?

Clinical ObservationClinical Observation – – Direct clinical observation of Direct clinical observation of patients with brain damage or disease - Ex. Phineas patients with brain damage or disease - Ex. Phineas GageGage http://www.youtube.com/watch?v=kc213mMSsjY

Invasive TechniquesInvasive Techniques – – Since 1850, experimenters Since 1850, experimenters have opened the skull and “invaded” the brain while have opened the skull and “invaded” the brain while the patient is still alivethe patient is still alive

Brain Tissue can be stimulated with electricity, Brain Tissue can be stimulated with electricity, chemicals, heat or cold. In addition, it can be chemicals, heat or cold. In addition, it can be lesionedlesioned, or destroyed in place, or destroyed in place

Brain Tissue can also be Brain Tissue can also be ablatedablated, or removed , or removed with a vacuum or scalpel. It can also be with a vacuum or scalpel. It can also be transectedtransected, meaning isolated or cut., meaning isolated or cut.

Neuroimaging TechniquesNeuroimaging Techniques EEG –EEG – Electroencephalogram Electroencephalogram

– Detects electrical currents – Detects electrical currents in the brain making possible in the brain making possible early evaluation of issuesearly evaluation of issues

Neuroimaging Techniques Neuroimaging Techniques cont’dcont’d

PET Scan – PET Scan – Positron Emission Positron Emission Tomography – Patient is injected with Tomography – Patient is injected with a safe dose of radioactive sugar. a safe dose of radioactive sugar. Brain cells that are particularly active Brain cells that are particularly active will consume more (or perhaps none) will consume more (or perhaps none) of the substance.of the substance.

The brain activity is measured by an The brain activity is measured by an imaging computerimaging computer

Neuroimaging Techniques Neuroimaging Techniques cont’dcont’d

CAT Scan – CAT Scan – Computerized Axial Computerized Axial Tomography – A narrow X-ray beam is Tomography – A narrow X-ray beam is aimed through the patient’s head & aimed through the patient’s head & hits a detector on the other side. Brain hits a detector on the other side. Brain tissue has different densities, and tissue has different densities, and blocks the beam to different degrees. blocks the beam to different degrees. The computer then constructs a picture The computer then constructs a picture that reveals damaged or dead tissue.that reveals damaged or dead tissue.

http://en.wikipedia.org/wiki/File:64_slice_scanner.JPG

Neuroimaging Techniques Neuroimaging Techniques cont’dcont’d

MRI –MRI – Magnetic Resonance Imaging – Safer Magnetic Resonance Imaging – Safer than a CAT Scan because there are no X-Rays.than a CAT Scan because there are no X-Rays.

The nuclei at the center of atoms have their The nuclei at the center of atoms have their own resonant frequencies. If they are own resonant frequencies. If they are perturbed, the bounce around, and return to perturbed, the bounce around, and return to their normal position. their normal position.

The MRI disturbs the atoms of the brain, and The MRI disturbs the atoms of the brain, and the computer assembles a detailed picture the computer assembles a detailed picture that may reveal tumors, tissue degeneration, that may reveal tumors, tissue degeneration, clots and leaks, etc.clots and leaks, etc.

http://videos.howstuffworks.com/tlc/29321-understanding-brain-mri-video.htm

Neurons and their MessagesNeurons and their Messages

Neural Pathways – Information travels in Neural Pathways – Information travels in the Nervous System through three the Nervous System through three types of neuronstypes of neurons

Sensory or Afferent Neurons (Inward) –Sensory or Afferent Neurons (Inward) – Sends information from the body’s Sends information from the body’s tissues and sensory organs inward to tissues and sensory organs inward to the spinal cord and brain for informationthe spinal cord and brain for information

Neurons and their Messages Neurons and their Messages cont’dcont’d

Interneurons –Interneurons – This processing involves a second This processing involves a second class of neurons of the brain and spinal cord (CNS). class of neurons of the brain and spinal cord (CNS).

Motor or Efferent Neurons –Motor or Efferent Neurons – Sends instructions to Sends instructions to the body’s tissues and extremitiesthe body’s tissues and extremities

Mnemonic Device – SAMEMnemonic Device – SAME http://www.youtube.com/watch?v=wK3VUQTRIBg&NR=1&safety_mode=true&persist_safety_mode=1&safe=active

The easiest example is the simple reflex – Ex. The easiest example is the simple reflex – Ex. Touching a hot stove Touching a hot stove http://www.youtube.com/watch?http://www.youtube.com/watch?v=1OYKegnG8Lo&NR=1v=1OYKegnG8Lo&NR=1

Nervous system vid 1:00Nervous system vid 1:00 http://www.youtube.com/watch?http://www.youtube.com/watch?

v=iBnGeDzTYD4&feature=related&safety_mode=true&persist_safety_mode=v=iBnGeDzTYD4&feature=related&safety_mode=true&persist_safety_mode=1&safe=active1&safe=active

Generating a Neural Generating a Neural ImpulseImpulse

Each neuron consists of a Each neuron consists of a cell body cell body (Soma)(Soma) and one or more branching and one or more branching fibers. The fibers are of two types:fibers. The fibers are of two types:

Dendrites –Dendrites – Receive information from Receive information from sensory receptors, or other neuronssensory receptors, or other neurons

Axons –Axons – Pass information along to Pass information along to other neuronsother neurons

***Dendrites – Short; Axons – Long ***Dendrites – Short; Axons – Long ******

Neurons and their messagesNeurons and their messages

Generating a Neural Impulse – cont’dGenerating a Neural Impulse – cont’d A layer of fatty cells called the A layer of fatty cells called the Myelin Sheath Myelin Sheath

insulates and speeds up their impulsesinsulates and speeds up their impulses When does a neuron fire?When does a neuron fire? When the neuron is stimulated by pressure, When the neuron is stimulated by pressure,

heat, light or chemical messages from heat, light or chemical messages from adjacent neurons. This impulse is called the adjacent neurons. This impulse is called the action potentialaction potential..

Action Potential is a brief electrical charge that Action Potential is a brief electrical charge that travels down the neuron like a spark down a travels down the neuron like a spark down a fuse. The signals trigger an impulse if the fuse. The signals trigger an impulse if the stimulus exceeds a minimum intensity called stimulus exceeds a minimum intensity called the the ThresholdThreshold – See handout on Action – See handout on Action PotentialPotential

Generating a Neural Impulse – Generating a Neural Impulse – cont’dcont’d

Increasing the stimulus above the threshold will Increasing the stimulus above the threshold will not increase the intensity of the impulse. The not increase the intensity of the impulse. The neuron’s reaction is an neuron’s reaction is an “All or None Response”“All or None Response” – Like firing a gun – either it fires, or it doesn’t– Like firing a gun – either it fires, or it doesn’t

***Reaction Time Experiment******Reaction Time Experiment*** http://www.bbc.co.uk/science/humanbody/sleep/http://www.bbc.co.uk/science/humanbody/sleep/

sheep/sheep/ How do you know the difference between getting How do you know the difference between getting

touched with a feather, or getting hit with a touched with a feather, or getting hit with a punch?punch?

More neurons can fire, and fire more oftenMore neurons can fire, and fire more often

Generating a Neural Impulse – Generating a Neural Impulse – cont’dcont’d There are tiny gaps, less than a There are tiny gaps, less than a

millionth of an inch wide. This junction millionth of an inch wide. This junction is called the…is called the…

SynapseSynapse If the neurons don’t touch, how does If the neurons don’t touch, how does

one neuron pass information to the one neuron pass information to the next?next?

Through chemical messengers called Through chemical messengers called neurotransmittersneurotransmitters

For a second, the neurotransmitter For a second, the neurotransmitter unlocks tiny gates like a “unlocks tiny gates like a “Lock and Lock and Key” Key” system - system - http://www.youtube.com/watch?v=90cj4NX87Ykhttp://www.youtube.com/watch?v=90cj4NX87Yk

Generating a neural impulse – Generating a neural impulse – cont’dcont’d One of the best understood One of the best understood

neurotransmitters is neurotransmitters is AcetylcholineAcetylcholine (ACh)(ACh)

Acetylcholine is the neurotransmitter at Acetylcholine is the neurotransmitter at every junction between a motor neuron every junction between a motor neuron and a muscle. When ACh is released to and a muscle. When ACh is released to the muscle cells, the muscle contracts. If the muscle cells, the muscle contracts. If ACh is blocked, muscles cannot contract. ACh is blocked, muscles cannot contract.

Ex. Curare – Poison that occupies and Ex. Curare – Poison that occupies and blocks ACh receptor sites leaving the blocks ACh receptor sites leaving the neurotransmitter unable to affect the neurotransmitter unable to affect the muscles – result is paralysis.muscles – result is paralysis.

Monkey Monkey http://www.youtube.com/watch?v=0P-FuwMDq5s&feature=relatedhttp://www.youtube.com/watch?v=0P-FuwMDq5s&feature=related

Generating a neural impulse – Generating a neural impulse – cont’dcont’d Ex. Botulin – Poison that causes paralysis by Ex. Botulin – Poison that causes paralysis by

blocking the release of ACh -blocking the release of ACh - http://www.youtube.com/watch?v=OX2ECc1lNFchttp://www.youtube.com/watch?v=OX2ECc1lNFc

***Opposite – Venom of a Black Widow ***Opposite – Venom of a Black Widow Spider *** - Causes a flood of Ach which Spider *** - Causes a flood of Ach which leads to muscle contractions and leads to muscle contractions and convulsionsconvulsions

Endorphins –Endorphins – “Morphine Within” – Natural “Morphine Within” – Natural opiate-like neurotransmitter linked to pain opiate-like neurotransmitter linked to pain control and pleasure. Most commonly control and pleasure. Most commonly released during exercise (“Runner’s high”)released during exercise (“Runner’s high”)

If endorphins lessen pain, and boost mood, If endorphins lessen pain, and boost mood, why not simply take morphine? – Handout of why not simply take morphine? – Handout of common neurotransmitters – “Must Know 5”common neurotransmitters – “Must Know 5”

http://www.youtube.com/watch?v=TjrBdKXgYFYhttp://www.youtube.com/watch?v=TjrBdKXgYFY

Divisions of the Nervous Divisions of the Nervous SystemSystem

Neurons function through several sub-systems Neurons function through several sub-systems – The – The Central Nervous System (CNS)Central Nervous System (CNS) includes all the neurons in the brain and spinal includes all the neurons in the brain and spinal cordcord

The The Peripheral (On the outside) Nervous Peripheral (On the outside) Nervous System (PNS)System (PNS) – Links the CNS with the body’s – Links the CNS with the body’s sense receptors, muscles and glandssense receptors, muscles and glands

The PNS has two components: The The PNS has two components: The Somatic Somatic Nervous SystemNervous System and the and the Autonomic Autonomic Nervous SystemNervous System

Divisions of the Nervous System – Divisions of the Nervous System – cont’dcont’d

The The SomaticSomatic transmits sensory input (touch transmits sensory input (touch and taste for example) to the CNS from the and taste for example) to the CNS from the outside world and directs motor or muscle outside world and directs motor or muscle output, such as our voluntary movementsoutput, such as our voluntary movements

The The AutonomicAutonomic influences glands and the influences glands and the muscles of our internal organs. Usually muscles of our internal organs. Usually operates on its own – “Autonomously” – operates on its own – “Autonomously” – Activities such as heartbeat, digestion, Activities such as heartbeat, digestion, glandular activity, etc.glandular activity, etc.

The Autonomic Nervous System also has The Autonomic Nervous System also has subcomponentssubcomponents

The Nervous System

Peripheral Nervous System Central Nervous System

Somatic Nervous System Autonomic Nervous System Brain Spinal Cord

Sympathetic Nervous System

Parasympathetic Nervous System

Divisions of the Nervous System – Divisions of the Nervous System – cont’dcont’d

The The Sympathetic Nervous SystemSympathetic Nervous System – – Arouses us for defensive action. It accelerates Arouses us for defensive action. It accelerates your heartbeat, slows digestion, raises your your heartbeat, slows digestion, raises your blood sugar, and cools you with perspiration.blood sugar, and cools you with perspiration.

When the stress is over, your When the stress is over, your Parasympathetic Nervous SystemParasympathetic Nervous System produces the opposite effects and calms you produces the opposite effects and calms you downdown

http://www.youtube.com/watch?http://www.youtube.com/watch?v=8PWH745MMMYv=8PWH745MMMY

The BrainThe Brain