Unit 3, Part 2

1. Unit 3, Part 2 The Nervous and Endocrine Systems

2. The Nervous System Rapid Response System

3. The Neuron • Basic functional unit of nervous system • Nerves – bundles of neurons • 3 basic parts: • Dendrites – receptors that receive stimuli; one neuron may have many dendrites and branches of dendrites • Cell body – contain nucleus and organelles • Axon – long fiber that transmits impulse away from cell body; only one per neuron • Trillions of neurons in body transmit information in the form of electrical and chemical impulses

5. The Resting Neuron • Not transmitting an impulse • Outside of the cell - a net positive charge • Inside of the cell - a net negative charge • Electrical charge across the cell membrane of a resting neuron is called the resting potential • These charges come from the Sodium Potassium Pump in cell membrane • Na+ ions pumped out of cell; K- ions pumped into cell by active transport

6. The Moving Impulse • A neuron remains in its resting state until it receives an impulse • An impulse begins when a neuron is stimulated by another neuron or the environment • Na+ ions flow into the neuron and the inside of the cell temporarily becomes more positive than the outside • The change from negative to positive is called a nerve impulse or an action potential

7. The Moving Impulse • The impulse travels down the axon away from the cell body • As impulse passes Na+flows out of the neuron and the resting impulse is restored • The neuron has a negative charge on the inside and a positive charge on the outside • Threshold – minimum amount of stimulus needed to trigger impulse

8. The Moving Impulse • Synapse - the location at which a neuron can transfer an impulse to another cell • Neurotransmitters – chemical messengers that transmit impulse across synapse

9. Classification of Neurons • Sensory neurons – detect stimuli and transmit info from: • Skin • Muscles • Joints • Sensory organs • Internal organs • Sensory stimuli include: • Taste • Touch • Smell • Hearing • Vision • Sensory impulses go to the spinal cord and brain

10. Classification of Neurons • Motor Neurons – send impulses from spinal cord and brain to the muscles or glands • Interneurons – found in the spinal cord; connect sensory and motor neurons in reflex arc • Myelin – lipid-based substance that surrounds axon and acts as an insulator • Increases speed of impulse • Not found on neurons in the brain

12. The Reflex Arc • Reflex arc – specialized nerve pathway that does not require conscious thought • Examples: • Pupil constriction/expansion response to light • Pulling back hand from hot surface • Kicking foot out when certain tendon is hit • Pathway: Sensory neuron Interneuron Motor Neuron

13. Anatomy of the Nervous System • Functions: • Control and coordinate functions throughout the body • Respond to internal and external stimuli • 2 Subsystems: • Central Nervous System (CNS) • Brain • Spinal Cord • Peripheral Nervous System (PNS) • Attach rest of body to CNS

14. Anatomy of the Nervous System • Parts of Central Nervous System: • Brain: • Cerebrum - responsible for voluntary activities of the body • Cerebellum - responsible for coordination and balance of the actions of the muscles • Helps the body to move gracefully and efficiently • Brain Stem - regulates information flow between the brain and the rest of the body • Controls basic life process – breathing and heartbeat • Spinal Cord: major communication link between brain ad rest of body

15. Anatomy of the Nervous System • Parts of the Peripheral Nervous System: • Somatic Nervous System • regulates activities under conscious control • Autonomic Nervous System • controls automatic or involuntary responses • contributes to homeostasis by managing other body systems • Sympathetic nervous system – responds to internal and external demands; “fight or flight” • Parasympathetic nervous system – returns the body to a balanced state; “rest and digest”

16. The Endocrine System Not So Rapid Response System

17. Hormones • Hormones - chemicals that travel the circulatory system to specific organs or cells • Steroid Hormones • Lipid-based (cholesterol) • Able to diffuse across the cell membrane of target cell • Inside cell, hormone attaches to receptor protein and is taken to the nucleus • Influences DNA to produce specific proteins • Non-steroid Hormones • Amino acid-based • Attach to receptor on cell membrane • Inside cell, hormone triggers chemical reactions in cell

18. Endocrine Glands • Gland – an organ that produces and secretes chemicals • Major glands: • Pituitary – master gland; controls other glands • Thyroid – controls metabolism • Parathyroid – maintains calcium levels in blood/bone • Adrenal – “fight or flight”; regulates sodium/potassium levels; anti-inflammatory • Pancreas – controls blood glucose • Ovaries – produces eggs; hormones estrogen and progesterone • Testes – produces sperm; hormone testosterone

19. Hypothalamus Center of brain; Communication between nervous and endocrine Systems Pineal Gland Regulates body clock

20. Feedback Mechanisms • All of your body systems work together to maintain homeostasis • The nervous and endocrine systems have the most control over this process • These systems use feedback loops to accomplish this • Feedback loop: • Hypothalamus & pituitary monitor hormone levels in blood • Level drops: message sent to increase production of hormone • Level rises: message sent to cancel first message

21. Feedback Mechanisms • Feedback inhibition (negative feedback) is the process in which a stimulus produces a response that opposes the original stimulus

22. Feedback Mechanisms • Examples: • Shivering and sweating are responses triggered by the nervous system to try to bring the body back to a “set point” • Eating when you are hungry/stopping when you are full

23. Feedback Mechanisms • Most feedback mechanisms are negative; childbirth is an example of positive feedback • Oxytocin and the prostaglandins cause uterine contractions that, in turn, stimulate the release of more oxytocin and prostaglandins. • This is partially due to pressure of the baby’s head against the cervix that both dilates the cervix and acts on cervical nerve endings to stimulate the production of oxytocin

24. Diabetes • Sometimes the negative feedback loop does not work properly • Too much or not enough hormone is made • Diabetes-disease in which production of insulin by pancreas is inadequate for homeostasis • Functions of insulin: • Allow glucose to diffuse across membrane into cell where it is converted to ATP • Stores excess ATP made by the cell as glycogen in skeletal muscle & liver cells • Also stores excess ATP as triglycerides in fat tissue

25. Diabetes • Function of Pancreas: • Secrete insulin to reduce total blood sugar level • Secrete glucagon to increase total blood sugar level from stored supplies of glycogen and triglycerides

26. Diabetes • Types of Diabetes: • Type 1- usually diagnosed in people under 30, including children; hereditary; • Cannot produce insulin • Must take insulin multiple times/day • Cannot be prevented/reversed • Type 2 – Typically occurs in adults; seeing more in younger people; result of diet • Produce insulin but body has developed a resistance to its effect • Must take more insulin to get same effect • Can be prevented/reversed

27. Effects of Uncontrolled Diabetes • Body cells cannot access and adequate supply of cellular energy to carry out normal function • Blindness • Kidney failure • Heart attacks • Circulatory issues • Tissue death