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Brain and Behaviour Neurotransmitters

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1 Brain and Behaviour Neurotransmitters
Stage 1 Psychology Brain and Behaviour Neurotransmitters

2 Human Nervous System The nervous system is made up of several parts.
The Central Nervous System (CNS) is made up of the areas encased by bone-- the brain and spinal cord. The Peripheral Nervous System (PNS) includes the rest of the nervous system ("peripheral" referring to the body outside the CNS).

3 Where are they? Types of Neurons
3 major types of neurons: 1. Sensory Neurons Bring information from sensory receptors to the central nervous system. i.e., Bring information from the eyes, ears, etc., as well as from some organs within the body e.g., stomach. (PNS) 2. Interneurons Neurons in the brain and spinal cord that serve as an intermediary between sensory and motor neurons. They carry information around the brain for processing.(CNS) The majority of neurons are located in the brain - approx. 100 billion 3. Motor Neurons Carry the information from the CNS to the appropriate muscles to carry out behaviours. (PNS)

4 Neuron: 3 parts Soma (<-- Greek for “body”)
= the cell body which contains the nucleus, cytoplasm, etc. Everything needed for survival. 2. Dendrites (<-- Greek for “tree”) = specialized branch-like structures used to receive information from other neurons. The more dendrites a cell has the more neurons it can communicate with. 3. Axon (<-- Greek for “axle”) = long, thin fibre that transmits signals away from the soma to other neurons or to muscles or glands Tail-like fibre that extends from the soma to the terminal buttons.

5 Structure of neurons Differ in size and shape

6 How do they work? A. Flow of information within neurons
1. Receives input from other neurons/sense organs at the dendrites 2. Inputs are integrated and action potentials are generated in the cell body, or soma 3. Output is conveyed to other neurons on the axon and across synapses

7 What's involved in a neural impulse?
1) Ions Positively (+) and negatively (-) charged particles are called ions. Neural impulses involve Sodium (Na+) and Potassium (K+) ions. 2) Selectively permeable membrane the outer membrane of the neuron is not impermeable, but instead selectively allows some small ions to pass back and forth. 3) Charge of the neuron Inside the neuron, the ions are mostly negatively charged. Outside the neuron, the ions are mostly positively charged. In this state (with mostly negative charge inside and positive charge on the outside) the neuron is said to be Polarized.

8 4) Resting potential When the neuron is Polarized, it is in a stable, negatively charged, inactive state. The charge is approx. -70millivolts The neuron is ready to fire (receive and send information). 5) Stimulus When stimulation occurs (e.g., hand on hot iron) the information is from a sensory receptor is brought to the dendrites of a neuron.

9 6) Action potential = a very brief shift in a neuron’s electrical charge that travels along an axon. Once the stimulation (e.g., the heat) reaches a certain threshold the neural membrane opens to allow the positively charged ions to rush in and the negative ions to rush out. The charge inside the neuron then rises to approx mv.

10 7) Repolarization = the neuron quickly restores its charge by pumping out the positively charged ions and bringing back the negative ones. Can occur fast enough to allow up to 1,000 action potentials per second. (60,000 per minute, 3,600,000 per hour, 86,400,000 per day etc.) 8) Absolute refractory period = the minimum length of time after an action potential during which another action potential cannot begin. During this period the charge inside the neuron drops to about - 90 mv before being restored.

11 How do they work? Flow of information between neurons

12 Synaptic cleft the microscopic gap between the terminal button of one neuron and the cell membrane of another neuron. Neurotransmitters are the chemicals which carry the nerve impulse from one neuron to another. Excitatory Inhibitory

13 Neurotransmitters Acetylcholine
Dopamine Norepinephrine /Noradrenaline Serotonin GABA Endorphins Activates motor neurons controlling skeletal muscles Contributes to the regulation of attention, arousal, thirst and memory Has mostly excitatory effects (i.e., makes receiving cells more likely to "fire"). Some ACh receptors stimulated by Nicotine

14 Neurotoxins - disrupting acetylcholine (ACh) and the transmission of information between neurons
Some South American Indians use curare on the tips of arrows for hunting. The curare binds to the receptor cites where Ach binds, so the Ach cannot be received, this results in paralysis and death. The black widow spider uses venom that causes flood of ACh into neuromuscular synapses which results in violent, uncontrollable muscle contractions, paralysis, and death.

15 Neurotransmitters Acetylcholine
Dopamine Norepinephrine /Noradrenaline Serotonin GABA Endorphins Contributes to the control of voluntary movement, Inhibitory (i.e., decreasing action of receiving cell) or excitatory, depending on receptor on receiving cell. Affects areas related to body movement; emotional arousal, and "reward" systems, pleasurable emotions Neurotransmitter looked at most closely for drug addiction. Parkinson’s Disease is associated with decreased levels Schizophrenia associated with over-activity at dopamine synapses Cocaine and Amphetamines elevate activity at synapses

16 Parkinson’s Disease Parkinson's disease affects nerve cells in the parts of the brain called the basal ganglia (pronounced BAY-sel GANG-lee-ah). This part of the brain controls movement and balance in the body. These nerve cells produce and store the neurotransmitter dopamine. In Parkinson's disease, the cells that produce dopamine are damaged. The instructions from the brain to the body about movement are disrupted as dopamine decreases.

17 Nerve cells in the basal ganglia send messages that signal the body to move.
In Parkinson's disease, many nerve cells are damaged. They do not produce enough dopamine to carry signals properly.

18 PET scan of glucose metabolic function of the brain

19 Studying changes in motor control in Parkinson’s Disease
Aiming task. Aiming and pointing with the hand of forearm to a target in space

20 Examples of “kinematic traces” of a patient with Parkinson’s Disease (PD), while "on" and "off" medication in comparison to the performance to a healthy age-matched participant. Note that the patient's performance was clearly slowed while "off" medication. During the "on" state, her speed and ability to accelerate improved, but she could not sustain this for the whole duration of the motion.

21 Neurotransmitters Contributes to modulation of mood and arousal
Mostly excitatory effects In the brain, has effects related to emotion, drive states such as hunger, and general brain arousal. Acetylcholine Dopamine Norepinephrine /Noradrenaline Serotonin GABA Endorphins Cocaine and Amphetamines elevate activity at synapses

22 Neurotransmitters Acetylcholine Dopamine Norepinephrine /Noradrenaline
Serotonin GABA Endorphins Involved in the regulation of sleep and wakefulness, eating, aggression Abnormal levels may contribute to depression and obsessive-compulsive disorder Inhibitory or Excitatory, depending on receptor Plays some role in perception and higher-order thinking (affected by hallucinogens) Prozac and other newer antidepressants work by increasing available serotonin

23 Neurotransmitters Acetylcholine Dopamine Norepinephrine /Noradrenaline
Serotonin GABA Endorphins Inhibitory-- The brain's main inhibitory transmitter. Found throughout the brain, GABA is necessary to keep brain activity under control. Under-activity of this neurotransmitter can lead to seizures. Depressant drugs (Valium, alcohol, barbiturates) work by increasing GABA activity

24 Neurotransmitters Acetylcholine Dopamine Norepinephrine /Noradrenaline
Serotonin GABA Endorphins Resemble optiate drugs in structure and affects Contribute to pain relief and perhaps some pleasurable emotions Morphine and opium work by mimicking endorphins at synaptic receptors

25 Neurochemical basis of drug action

26 Caffeine as a psychoactive drug
Caffeine is a central nervous system stimulant. In moderate doses, caffeine can: increase alertness reduce fine motor coordination cause insomnia cause headaches, nervousness and dizziness In massive doses, caffeine is lethal (80 to 100 cups of coffee in rapid succession) About 6 hours for one half of the caffeine to be eliminated. Caffeine can cause physical dependence. Typical withdrawal symptoms = headache, fatigue and muscle pain.

27 Caffeine is psychoactive because it mimics a neurotransmitter
Caffeine belongs to the xanthine chemical group. Adenosine is a naturally occurring xanthine in the brain that is used as a neurotransmitter at some synapses. One effect of caffeine is to interfere with adenosine at multiple sites in the brain including the reticular formation.

28 Caffeine as preventative therapy for Parkinson’s Disease?
Honolulu Heart Program, 8,004 Japanese-American men over a 30 year period. Incidence of Parkinson's disease lower in those who drank coffee. Consumption of caffeine from other sources such as green tea, black tea, chocolate and soda was also associated with a lower risk of Parkinson's disease. Caffeine

29 How could it work? When adenosine receptors are blocked, levels of the neurotransmitter dopamine increase. Caffeine may protect against Parkinson's disease by blocking adenosine receptors, thus increasing the amount of dopamine in the brain.

30 Alcohol is a central nervous system depressant
In low doses, alcohol produces: * a relaxing effect (inhibits anxiety) * reduces tension * lowers inhibitions * impairs concentration * slows reflexes * impairs reaction time * reduces coordination In medium doses, alcohol produces: * slur speech * cause drowsiness * alter emotions In high doses, alcohol produces: * vomiting * breathing difficulties * unconsciousness * coma

31 Alcohol works via many neurotransmitters:
Structure of ethanol Alcohol works via many neurotransmitters: Alcohol acts at many sites, including the reticular formation, spinal cord, cerebellum and cerebral cortex, and on many neurotransmitter systems. Some of the effects of alcohol on neurotransmitters are: 1. Increased concentration of norepinephrine and dopamine (D=pleasure centres) 2. Decreased transmission in acetylcholine systems 3. Potentiates GABA receptor sites (inhibitory) (sedative) Increased production of beta-endorphin in the hypothalamus Alters serotonin transmission (behaviour inhibitor) (aggression, sexual activity)

32 Role of myelin in behaviour- Multiple Sclerosis
MS is thought to be an autoimmune disease that affects the central nervous system (CNS). In MS, myelin is lost, leaving scar tissue called sclerosis (also known as plaques or lesions). Sometimes the nerve fiber itself is damaged or broken.

33 Magnetic resonance imaging brain scan showing areas of abnormal tissue (arrows) in multiple sclerosis

34 Cognitive symptoms of MS
The MS symptoms that usually grab the spotlight are the physical ones—balance, gait, muscle control, bladder control, vision, numbness. In the last decade, evidence on how MS may affect cognition 40% to 60% of people with MS develop some degree of “cognitive dysfunction”. Most people who are affected have mild problems.   Cognitive dysfunctions arise when lesions (or areas of MS damage) occur in certain locations in the cerebral hemispheres, the “thinking” part of the brain.

35 Common cognitive symptoms of MS:
Poorer memory for recent events and information Fluency with words may be diminished.(word search <-- memory ) When a lot of information is coming all at once, processing may take longer.   Judgment and problem solving may be slower or less reliable. Some people with MS-caused cognitive problems have difficulty analyzing a situation, coming up with a solution, and carrying it out.

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