Central nervous system & neurotransmitters PDF

Central nervous system & neurotransmitters Prof. Dr. Mekky Abouzied PHRM 105 General Biology  Outline Be the end of this session, students should be able to: Define the nervous system. List the parts of the nerve cells and the function of each parts. Describe the...

Central nervous system & neurotransmitters Prof. Dr. Mekky Abouzied PHRM 105 General Biology  Outline Be the end of this session, students should be able to: Define the nervous system. List the parts of the nerve cells and the function of each parts. Describe the synapse and its components List the different neurotransmitters and their functions.  1. Introduction A living organism is able to react to changes in the surrounding. The change in the environment that cause an organism to react is called a stimulus. An organism’s reaction to a stimulus is called a response. The ability to respond to a stimulus is known as sensitivity or irritability.  Why do animals need a nervous system? The nervous system in humans controls the activities of the body and how it reacts to the surroundings. The nervous system consist of a brain, spinal cord, spinal nerves and highly specialized sense organs. Sense organs: help the body to adjust to any changes in the environment Enable the various parts of the body to coordinate with one another ‫لإلطالع‬ Sense organs are used to detect stimuli, they are also called receptors. They inform the central nervous system about changes in the surroundings, by producing electrical messages called nerve impulses. These nerve impulses are transmitted through the peripheral nervous system to the central nervous system. ‫لإلطالع‬ You have about 1 trillion nerve cells in your body, and 100 chemicals that transfer messages between those nerves.! (Those chemicals are called neurotransmitters). ‫لإلطالع‬ ‫لإلطالع‬  Nervous system cells Neuron (nerve cell) signal direction dendrites cell body  Structure fits function  Many entry points for signal  One path out  Transmits signal axon signal direction myelin sheath synaptic terminal synapse dendrite cell body axon Part of a neuron with functions  Definition of synapse: A synapse is a junction between 2 neurons, or a junction between a neuron and an effector such as a muscle or a gland At a synapse, impulses are transmitted from the axon of one neuron to the dendron of another neuron ( or the cells of the effector) across the tiny space Nerve impulse are transmitted across the synapse by certain chemicals released by the neurone. These chemicals are called neurotransmitters Until the early 20th century, scientists assumed that the majority of synaptic communication in the brain was electrical. In 1921 German pharmacologist Otto Loewi confirmed that neurons can communicate by releasing chemicals Otto Loewi is credited with discovering Acetylcholine (ACh)— the first known neurotransmitter ‫لإلطالع‬  Neurotransmitter They are chemical messengers that transmit a message from a nerve cell across the synapse to a target cell. They are released from synaptic vesicles into the gap between nerve cells (synaptic cleft), where they bind to neurotransmitters receptors on the target cell. The exact number of unique neurotransmitters in humans is unknown, but more than 200 have been identified A neurotransmitter influences a neuron in one of three ways: excitatory, inhibitory or modulatory. Glutamate Acetylcholine ‫لإلطالع‬  Key facts about neurotransmitters Excitatory Glutamate (Glu) neurotransmitters Acetylcholine (ACh) Histamine Dopamine (DA) Norepinephrine Epinephrine Inhibitory gamma-Aminobutyric acid (GABA) neurotransmitters Serotonin (5-HT) Dopamine (DA) Neuromodulators Dopamine (DA) Serotonin (5-HT) Acetylcholine (ACh) Histamine Norepinephrine (NE) Neurohormones Releasing hormones from hypothalamus Oxytocin (Oxt) Vasopressin; also known as antidiuretic hormone (ADH) ‫لألطالع‬ Neurotransmitters: Classification  Identification Criteria of Neurotransmitters There are four main criteria for identifying neurotransmitters: 1. The chemical must be synthesized in the neuron or otherwise be present in it. 2. When the neuron is active, the chemical must be released and produce a response in some targets. 3. The same response must be obtained when the chemical is experimentally placed on the target. 4. A mechanism must exist for removing the chemical from its site of activation after its work is done. Acetylcholine helps send messages between nerve cells and is crucial for many functions, like muscle movement, heart rate, and memory. It works through two main types of receptors: nicotinic and muscarinic. What happens if neurotransmitter production decreased or increased? An excess or lack of certain neurotransmitters can impact our behavior Examples: Parkinson’s Disease causes the brain cells that produce dopamine to die. The lack of dopamine in the body leads to shaking, irregular movements, and loss of motion control. unusually high amounts of dopamine in our bodies is related to schizophrenia.