19: The Nervous System

1. 19:The Nervous System Section Objectives: Analyze how nerve impulses travel within the nervous system. Interpret the functions of the major parts of the nervous system. Compare voluntary responses and involuntary responses.

2. The Nervous System • Controls and coordinates the body’s responses to changes in the environment • HOW: • Stimulus: a change in the external or internal environment which initiates an impulse • Impulse~ an electro-chemical charge generated along a neuron • Receptors~ structures specialized to detect certain stimuli • Response~ a reaction to a stimulus • Effectors~ what responds to a stimulus such as muscles or glands

3. Neurons: Basic Units of the Nervous System • Neurons conduct impulses throughout the nervous system. • A neuron is a long cell that consists of three regions: a cell body, dendrites, and an axon.

4. Neurons: Basic Units of the Nervous System • Dendrites~ receive impulses and carry them toward the cell body • Axon~ carries impulses away from the cell body and toward other neurons, muscles, or glands. • Cell body~ contains the nucleus

5. Myelin coating signal direction • Axon coated with insulation made of myelin cells • speeds signal • signal hops from node to node • 330 mph vs. 11 mph myelincoating • Multiple Sclerosis • immune system (T cells) attacks myelin coating • loss of signal

6. Fun facts about neurons • Most specialized cell in animals • Longest cell • blue whale neuron • 10-30 meters • giraffe axon • 5 meters • human neuron • 1-2 meters Nervous system allows for 1 millisecond response time

7. Neurons: Basic Units of the Nervous System 3 Types of neurons. • 1. Sensory neurons: carry impulses from the body to the spinal cord and brain (sense receptors) • 2. Motor neurons carry the response impulses away from the brain and spinal cord to a muscle or gland. (effectors) • 3.Interneurons: connect sensory &motor neurons within the brain and spinal cord

8. Types of neurons sensory neuron (from senses) interneuron (brain & spinal chord) motor neuron (to muscle)

9. How an impulse is transmitted • 1. Resting: no impulse, cell is polarized( + on outside & - on inside) • Sodium/Potassium pump in axon using ATP maintains this polarity

10. How an impulse is transmitted • 2.Impulse: stimulus excites neuron • Na+ gates open • Na+ goes inside, therefore inside becomes more + • Depolarization occurs ~ a nerve impulse • Impulse moves in one direction

11. Synapse ~ connection between neurons & effector cells Junction between nerve cells • 1st cell releases chemical (neurotransmitter) to trigger next cell • where drugs affect nervous system synapse

12. cerebrum cerebellum spinal cord cervical nerves thoracic nerves lumbar nerves femoral nerve sciatic nerve tibial nerve Nervous System • Central nervous system (CNS) • brain & spinal cord • Peripheral nervous system (PNS) • nerves from senses • nerves to muscles 2 systems work together

13. Anatomy of the brain • Cerebrum: • Conscious activities • Intelligence • Memory • Language • Voluntary activity • Cerebellum: -Coordinates motor activity -balance Medulla Oblongata: involuntary activities such as breathing,&heart rate

14. Nervous System Peripheral Nervous System (PNS) Central Nervous System (CNS) Somatic Nervous System(voluntary) Relays information to and from skin and skeletal muscles. Autonomic Nervous System(involuntary) Relays information to internal organs. Parasympathetic Nervous System Controls organs when body is at rest Sympathetic Nervous System Controls organs in times of stress.