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REGULATION Two Types of Regulation Nervous: Accomplished by nervous system Sends message as impulses Messages is short-lived and happens rapidly Chemical: Accomplished by endocrine system Sends chemical messengers called hormones Message is widespread and happens slowly Nervous System Stimulus: internal or external change that occurs in an organism Response: organisms reaction to a stimulus Impulse: electrochemical message carried by nerve cell Receptor: structure that detects stimuli Effector: muscle or gland that responds or reacts to the command of nervous system Structure of the Nervous System Neurons: Specialized cells that help gather information, interpret it and react to it. Using Electrochemical messages Structure of the Nervous System Nerve: A bundle of neurons Parts of the Neuron Main Parts of the Neuron Dendrites: Receive impulses from other Neurons and conducts it to cell body Cell Body: The nucleus and other organelles are found here Axon: Carries the nerve impulse away from the cell body to other neurons and muscles Terminal Branch: End of axon; area where neurotransmitters are secreted Parts of the Neuron Main Parts of the Neuron Myelin Sheath: Insulation that increases the speed at which the impulse can travel Schwann Cells: Surrounds the axon; produces the myelin sheath Node Of Ranvier: Gap between neighboring Schwann cells Synapse Synapse: Small space between two successive Neurons Synapse and Neurotransmitters Synapse: Is the small gap between the axon and the dendrite of neighboring nerve cells. Neurotransmitter: Chemical that is released from a neurons axon and binds with receptors of another neuron’s dendrites Ex: Acetylcholine Synapse Synapse Neurotransmitter Synapse Neurotransmitters - are chemicals used to transmit an impulse from the axon of one neuron to the dendrites of the next neuron Neurotransmitters Excitatory neurotransmitters will excite a neuron, causing an action potential ( Norepinephrine, Acytylcholine) Inhibitory neurotransmitters will depress (inhibit or slow) a neuron, suppressing an action potential that might otherwise go forward (Serotonin) The Synapse 3 Types of Neurons Sensory neurons: Transmit impulses from the skin and sense organs (Receptors) to the central nervous system (Brain and Spinal Cord). Interneurons: Interpret and relay nerve impulses between sensory and motor neuron. (ONLY found In the Brain & Spinal Cord) Motor Neurons Transmit impulses from the CNS to the muscles or glands (Effectors) Reflex & Reflex Arc 1. Reflex is a quick automatic involuntary response to a stimulus. 2. Reflex arc is the pathway that an impulse travels. a. b. c. Impulse is the message carried by the neuron. The transmission of the impulse is very quick. Composed of Sensory neuron, interneuron, and motor neuron. Notice the Brain is NOT involved Sensory Neuron Stimulated by sensory receptors Interneuron Spinal cord Motor Neuron Muscle or Gland Reflex Arc 4. RECEPTOR SENSORY NEURON INTERNEURON MOTOR NEURON 5. EFFECTOR (MUSCLE OR GLAND) 1. 2. 3. Nerve Impulses Nerve Impulse: A series of electrochemical changes in a nerve cell membrane Resting Potential The distribution of Na+ and K+ inside and outside the neuron causing a negative charge for the neuron. Unequal distribution of these ions is maintained by active transport Nerve Impulses Threshold - Is the minimum level of stimulus that activates the neuron. - Any stimuli weaker than the threshold WILL NOT produce an impulse. Nerve Impulses Action Potential - Begins when a neuron is stimulated by another neuron or by its environment. - Na+ gates on the axon open up and let Na+ flow in. -The inside of the neuron gains an positive charge and the outside gains a negative charge. -This is known as action potential. Nerve Impulses Impulse Graph Action Potential Action Potential Action Potential Animation The Nervous System Consists of two major divisions: •The Central Nervous System •The Peripheral Nervous System The Central Nervous System 1. The Brain 2. The Spinal Cord Which is mostly Interneurons Brains The Brain… The Brain Is responsible for controlling and coordinating most of the activities of humans Cerebrum is the center of voluntary activities, memory and learning Cerebellum coordinates motor activities and helps in maintaining balance The Brain Medulla Oblongata controls involuntary activities such as breathing, heartbeat, blood pressure and peristalsis. The Brain Medulla Oblongata controls involuntary activities such as breathing, heartbeat, blood pressure and peristalsis. Pons: Communicates between Cerebrum and Cerebellum The Brain Medulla Oblongata controls involuntary activities such as breathing, heartbeat, blood pressure and peristalsis. Pons: Communicates between Cerebrum and Cerebellum Hypothalamus: Maintains homeostasis ( Temp. Thirst, Appetite, and water balance) Spinal Cord •Coordinates between the brain and the other body structures •Reflexes are processed in spinal cord Spinal Cord •Protected by the Spinal Column – Bony structure The Peripheral Nervous System It consists of sensory neurons and motor neurons that carry information to and from the CNS The Peripheral Nervous System Somatic nervous system: Relays information to and from the skin and skeletal muscles. Most of the time voluntary except for a “Reflex” Autonomic nervous system: Relays information to internal organs and is involuntary Sympathetic Nervous System Parasympathetic Nervous System The autonomic division of the PNS has 2 major divisions Sympathetic nerves Increases the activity of the organ Ex) accelerator nerve - speeding the heart beat Parasympathetic nerves Decreases the activity of an organ Ex) the vagus nerve slowing the heart beat Nervous System Disorders Cerebral Palsy : A congenital disease characterized by a disturbance of motor functions. Usually normal intelligence In certain cases there is no identifiable cause, other etiologies include problems in intrauterine development (e.g. exposure to radiation, infection), asphyxia before birth, hypoxia of the brain, and birth trauma during labor and delivery. Meningitis: Is swelling and irritation (inflammation) of the membranes covering the brain and spinal cord. This inflammation causes changes in the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord. Meningitis: Caused by Bacterial or Viral Infection in the Spinal Fluid Symptoms: Headache, Stiff Neck, fever Vomiting, light sensitivity Treatment: Antibiotics, anti-virals and now a vaccine to help prevent Polio Is a viral disease that can affect nerves and can lead to partial or full paralysis. Preventable by vaccine The first was developed by Jonas Salk and tested in 1952. Stroke: Is an interruption of the blood supply to any part of the brain. Caused by blood clot of brain or hemorrhage. Most symptoms are muscle weakness or paralysis depending on which part of brain was affected. One’s own immune system attacks the myelin sheath on their nerve cells. Vision problems, depression, muscle weakness and paralysis may occur How drugs work on the Brain How drugs work on the brain