NeuralBasisofHumanbehavior.ppt
- 2. The Central Nervous System Composed of the Brain and the Spinal cord. The CNS relays messages from the brain to the Peripheral Nervous System, and vice versa. A series of neurons that connect organs and muscles to the CNS. The PNS receives messages from the brain sends messages to it from the senses. THE PERIPHERAL NERVOUS SYSTEM
- 3. SPECIALIZATION INTEGRATION Individual parts perform one or more functions for the body The brain coordinates many parts to fully accomplish a task
- 4. There are about 100 billion neurons in the brain. These neurons carry out certain functions, store information, can change functions and make connections with other neurons.
- 5. NEURONS These are the billions of cells in the CNS and PNS that relay the messages throughout the body. Sensory Neurons Send signals from the senses to the brain Motor Neurons Sent signals from the brain to parts of the body
- 6. Neuron Structure SOMA: the neuron’s cell body DENDRITES: branches from the cell body that receive incoming signals AXON: extension that carries signals from the soma (outgoing)
- 7. Classification of neurons Functional classification of neurons :Sensory and Motor Classification as per neurotransmitter release: Cholinergic, dopaminergic, serotonergic Classification on basis of axonal length
- 8. Nerves and Tracts Collection of nerves outside CNS is nerves and inside CNS is called tracts.
- 9. Each cell has a cell membrane, which surrounds the cell and protects the inner components. These internal components include a nucleus (a central structure that holds your genetic information),ribosomes (tiny structures that make proteins) and organelles (little organs that perform various functions). All cells also have cytoplasm, which is a clear, jelly-like fluid that fills the inside of the cell and surrounds all of the internal structures. Mitochondria : An organelle that break down nutrients such as glucose and provide the cell with energy to perform its functions. It produce a chemical called Adenosine Triphospate (ATP) : an energy-bearing molecule found in all living cells. Formation of nucleic acids, transmission of nerve impulses, muscle contraction, and many other energy-consuming reactions of metabolism are made possible by the energy in ATP molecules. The energy in ATP is obtained from the breakdown of foods.
- 10. The nucleus includes many important structures, and perhaps most important are the chromosomes, which are made up of strands of deoxyribonucleic acid (DNA), which are made up of genes. These genes contain "programs" or "blue prints" for the direction of protein synthesis, which is the creation of structures that carry out the cell's work.
- 11. Speed of Nerve Impulses Impulses travel very rapidly along neurons. The presence of a myelin sheath greatly increases the velocity at which impulses are conducted along the axon of a neuron. In unmyelinated fibres, the entire axon membrane is exposed and impulse conduction is slower.
- 12. Supporting Cells of the Nervous System There are several types of supporting cells that occur in both the CNS and the PNS. None of them conduct impulses, instead they “assist” neurons. As a group they are called neuroglia or “glia” cells, (means “nerve glue”) found in between neurons. Different cells do different jobs. In the CNS the cell is called the oligodendrocyte In the PNS the cell is the Schwann cell.
- 13. Blood Brain Barrier Over one hundred years ago, Paul Ehrlich discovered that if a blue dye is injected into an animal’s bloodstream, all tissues except the brain and spinal cord will be tinted blue. However, if the same dye is injected into the fluid-filled ventricles of the brain, the blue color will spread throughout the CNS (Bradbury, 1979). This experiment demonstrates that a barrier exists between the blood and the fluid that surrounds the cells of the brain: the blood–brain barrier.
- 14. selectively permeable (per, “through”;meare, “to pass”) The blood–brain barrier is not uniform throughout the nervous system. area postrema (poss tree ma) A region of the medulla where the blood–brain barrier barrier is weak; poisons can be detected there and can initiate vomiting.
- 18. Membrane Potential Cell membranes in general, and membranes of nerve cells in particular, maintain a small voltage or "potential" across the membrane in its normal or resting state. In the rest state, the inside of the nerve cell membrane is negative with respect to the outside (typically about -70 millivolts). there is an electrical potential difference between the inside of the cell and the surrounding extracellular fluid changes in their membrane potentials are used to code and transmit information When a nerve or muscle cell is at "rest", its membrane potential is called the resting membrane potential. In a typical neuron, this is about –70 millivolts (mV). The minus sign indicates that the of the cell is negative with respect to the surrounding extracellular fluid.
- 19. Properties of the Neuron Neurons contain many ions and are charged A- are large protein ions that always stay inside the cell K+ is potassium. At rest it is mostly inside the cell Cl- is chloride. It exists both inside and outside the cell Na+ is sodium. It exists primarily outside the cell
- 21. Resting Potential When a neuron is not sending a signal, it is "at rest." When a neuron is at rest, the inside of the neuron is negative relative to the outside. Although the concentrations of the different ions attempt to balance out on both sides of the membrane, they cannot because the cell membrane allows only some ions to pass through channels (ion channels). At rest, potassium ions (K+) can cross through the membrane easily. Also at rest, chloride ions (Cl-)and sodium ions (Na+) have a more difficult time crossing. The negatively charged protein molecules (A-) inside the neuron cannot cross the membrane.
- 24. The fluid within cells (intracellular fluid) and the fluid surrounding them (extracellular fluid) contain different ions. The action potential is an explosion of electrical activity that is created by a depolarizing current. This means that some event (a stimulus) causes the resting potential to move toward 0 mV. When the depolarization reaches about -55 mV a neuron will fire an action potential. This is the threshold. If the neuron does not reach this critical threshold level, then no action potential will fire. Also, when the threshold level is reached, an action potential of a fixed sized will always fire...for any given neuron, the size of the action potential is always the same
- 26. As an action potential travels down the axon, there is a change in polarity across the membrane. The Na+ and K+ gated ion channels open and close as the membrane reaches the threshold potential, in response to a signal from another neuron. At the beginning of the action potential, the Na+ channels open and Na+ moves into the axon, causing depolarization. Repolarization occurs when the K+ channels open and K+ moves out of the axon. This creates a change in polarity between the outside of the cell and the inside. The impulse travels down the axon in one direction only, to the axon terminal where it signals other neurons.
- 28. An ion is an atom or group of atoms in which the number of electron s is different from the number of proton s. If the number of electrons is less than the number of protons, the particle is a positive ion, also called a cation. Anions have negative charge There are several important ions in these fluids. Four of them here: organic anions (symbolized by A-), chloride ions (Cl-), sodium ions (Na+), and potassium ions (K+).
- 29. Nerve Conduction Within the Neuron Depolarization- An electrical process -70 mill volts When the neuron is resting, not conducting nerve impulses, it is polarized. The cell is invaded by Na ions and the expulsion of K ions. The electric charge is gone. Depolarization occurs! Between Neurons A chemical process When depolarization reaches the terminal buttons, neurotransmitters are released into the synapse. Either excite or inhibit the following neuron! Sending neuron-presynaptic neuron Receiving neuron- postsynaptic neuron.
- 30. Delivering the Message 1. Impulse is received through the dendrites from another neuron or a sense. 2. Soma fires; an impulse is sent down the axon to the next neuron.
- 31. Myelin sheaths a layer of proteins that are wrapped around the axon, protects the axon, and speeds up transmission of signal. Myelin sheaths can send several waves of impulses down longer axons at once. Breakdown of myelination connected to development of Multiple Sclerosis (an autoimmune disorder in which the myelin is destroyed - fatigue, pain, motor disorders, cognitive disorders, etc.) Axons are millimeter long up to one meter (base of spinal cord to foot) Difference between Axon and Dendrites: Axon takes information away from cell body whereas dendrites receive information from other neurons. One neuron simultaneously receive information from 10,000 neurons.
- 32. Impulse Conduction Unmyelinated fibers conduct impulses over their entire membrane surface. Without myelin, neural transmission is inefficient Myelinated fibers conduct impulses from node of Ranvier to node of Ranvier, a phenomenon called saltatory conduction. Saltatory conduction is many times faster than conduction on unmyelinated neurons. Myelination in PNS is through Schwann cells and mylienal cells in CNS is through OLigodend
- 33. All-or-None Response If a nerve fiber responds at all to a stimulus, it responds completely by conducting an impulse (all-or- none response). Greater intensity of stimulation triggers more impulses per second, not stronger impulses.
- 35. Neurons communicate in two ways Electrical signal: within a neuron Chemical signal: between neurons Electrical signal is sent from one part of the neuron to the other: The signal travels the dendrite through the cell body to the axon ◦Dendrites receive the signal from another neuron ◦Axons send the signal to other neurons Chemical signal is sent from the axon of one neuron to the dendrite of another neuron
- 36. When the sum of the potentials reaches the base of the axon, a sufficient charge may be present to cause an action potential.
- 37. Removal of Neurotransmitter After the NT is initially released, the chemical must be removed This is done in a couple of different ways ◦Biochemical breakdown of the NT ◦Reuptake: NT is pulled back into the presynaptic button and packaged to be released again
- 38. Neurotransmitters Chemicals that are produced and stored in the axon. Neurotransmitters pass from one neuron to the next to help relay messages through the body. Sending neuron Receiving neuron Neuro- transmitters
- 39. Neurotransmitters enter the synaptic gap, where most are absorbed by the receiving neuron. Excess neurotransmitters are reabsorbed by the sending neuron; this is called “reuptake.” Synaptic Gap
- 40. Excitatory and Inhibitory Messages Excitatory message—increases the likelihood that the postsynaptic neuron will activate Inhibitory message—decreases the likelihood that the postsynaptic neuron will activate
- 41. Types of Neurotransmitters Excitatory ◦ Glutamate ◦ Acetylcholine Inhibitory ◦ GABA ◦ Norepinephrine Both ◦ Dopamine ◦ Serotonin
- 42. Different neurotransmitters carry out different functions. The role and effects of malfunctioning of most common neurotransmitters are: Acetylcholine (ACh) enables muscle action, learning and memory. linked to Alzheimer’s Disease Neurons that produce ACh deteriorate later in life, reducing the levels of it in the brain and disrupting memory and retention of new skills and occurrences (learning).
- 43. D O P A M I N E LOW RANGE: Body tremors and decreased mobility NORMAL RANGE HIGH RANGE: hallucinations = Parkinson’s Disease symptoms = Schizophrenia Dopamine influences movement, emotion and learning.
- 44. Chlorpromazine used to treat schizophrenia hallucinations. Too much led to Parkinson’s like symptoms, connecting dopamine to the disease. Serotonin affects mood, sleep and arousal. low levels linked to depression Common use of Selective Serotonin Reuptake Inhibitors (SSRIs) to prevent reuptake of serotonin. This effectively increases the amount absorbed from the synaptic gap. SSRI examples: Prozac, Zoloft, Paxil
- 45. Endorphins Morphine and codeine work on endorphin receptors; involved in healing effects of acupuncture Runner’s high— feeling of pleasure after a long run is due to heavy endorphin release
- 46. Different Neurotransmitter Substances and their Effects on Behavior Neurotransmitter Effects on Behavior 1. Acetylcholine Found in neuromuscular junctions Involved in muscle movement Facilitates learning and memory Deficiency of ACH disrupts learning and memory 2. Norepinephrine Arousal, depression & stress Fight or flight response Too little may lead to depression Too much causes hyperactivity
- 47. Different Neurotransmitter Substances and their Effects on Behavior Neurotransmitter Effects on Behavior 3. Dopamine Involved in movement, attention & learning Over supply may lead to schizophrenic reaction Under supply causes Parkinson’s Diseases (a neurological disorder disrupting coordinated movement) 4. Serotonin Involved in sleep & depression Lack of serotonin produces anemia Prevents dreaming in the waking state Considered as the “worry” chemical in the brain
- 48. Different Neurotransmitter Substances and their Effects on Behavior Neurotransmitter Effects on Behavior 5. GABA (gamma aminobutyric acid) Decreases the activity of the neuron/brain activity May decrease levels of anxiety 6. Endorphins Control pain & pleasure Released in response to pain Pain relieving effect; a neuropeptide