1. The Nervous System

2. Neurons: specialized cells of the nervous system. 3 major regions: – 1) Dendrites: receive signals from other neurons – 2) Cell Body: contains the nucleus and organelles – 3) Axon: Carries impulse signal to other neurons/muscles – 4) Myelin sheeth – surrounds portions of the axon to protect and insulate.

3. Types of neurons: Sensory: Send impulses from receptors in the sense organs to the spinal cord and brain. Motor: Carry a signal from brain and spinal cord to glands/muscles. Interneuron: Found in the spinal cord and brain. Sends messages between sensory and motor neurons.

4. Reflex arc A reflex is an preprogrammed response to a certain stimulus. In a reflex a sensory neuron sends a message to the spinal cord which immediately relays a response to a motor neuron. The brain does not interpret the response until after it has happened!

5. Nerve Impulse – charge traveling through a neuron. 1. A stimulus is received by a sensory neuron. 2. The impulse is sent towards the spinal cord and then up to the brain to receive the message. 3. The brain sends a response to a motor neuron with reaction instructions.

6. Action-Potential Nerves: All or nothing! In order for nerves to send an impulse, they rely upon the concentration of ions to function properly. Specifically Sodium and Potassium ions control impulses. At rest: Slightly negative inside the cell, slightly positive outside. Stimulus causes pumps to activate, dumping positive sodium ions outside the cell and pulling in less potassium – reversing the charges on either side of the membrane.

7. Sodium-Potassium Pumps To allow for action potentials, a protein pump is used. The one protein dumps 3 positive charges out of the cell (Na + ) and pulls in 2 K + ions. Each time the pump makes this switch, ATP is used.

8. Impulses The impulse travels the length of the nerve cell’s axon until it reaches the end. Between 2 neurons there is a gap called a synapse. The impulse causes the axon to send neurotransmitters to the dendrites of the next neuron to continue the message.

9. Organization of the Nervous System: 2 Divisions The nervous system has 2 divisions: Central Nervous System (CNS) – Brain and spinal cord – Mostly interneurons Peripheral Nervous System (PNS) – Sensory and motor neurons that carry info to and from CNS.

10. CNS - Brain Cerebrum: Largest portion. – Involved with learning, memory, speech/language, senses and voluntary movement. Cerebellum: Found in the back. – Controls balance and coordination, smooth muscle (involuntary movement). Medulla Oblongata: Relays signals between brain and spinal cord. – Controls breathing rate, heart rate, and blood pressure.

11. CNS – Spinal Cord Extends from the brain to the lower back Protected by the spinal column or vertebrae. Reflexes are processed by the spinal cord.

12. PNS - Subdivided into Somatic and Autonomic. Somatic Nervous System relay info from sensors to CNS. – comprises voluntary actions Autonomic carries impulses from CNS to heart and other internal organs. – Comprise involuntary actions (out of your control).

13. Autonomic Divisions Sympathetic and Parasympathetic divisions. – Sympathetic Nervous System act in times of stress: High heart rate and breathing. – Parasympathetic Nervous System active when the body is relaxed. – Both relay messages to the same organs, but the over responses depends on which division is in control.

14. Drug Effects A drug is a substance that alters some function of the body. Certain drugs: – change the amount of neurotransmitters released. – Block receptors of neurotransmitters. – Imitate neurotransmitters. Types of drugs: – Stimulants: Increase activity Caffine Nicotine – Depressants: Decrease CNS, blood pressure and heart rate. Often raise levels of dopamine  creating a happy feelings. Alcohol Inhalants Illegal drugs

15. Disorders Meningitis – and inflammation of the meninges. This can be life threatening and lead to a number of other disorders if not treated. Multiple Sclerosis – Breakdown of the myelin protective coverings around neurons. Can cause paralysis, loss of function, cognitive issues and death if untreated.