The Nervous and Endocrine Systems Unit 3, Part 2 1

The Nervous System Rapid Response System 2

The Neuron Basic functional unit of nervous system Nerves – bundles of neurons 3 basic parts: 1. Dendrites – receptors that receive stimuli; one neuron may have many dendrites and branches of dendrites 2. Cell body – contain nucleus and organelles 3. 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 3

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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 5

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 6

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 7

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 8

Classification of Neurons Sensory neurons – detect stimuli and transmit info from: 1. Skin 2. Muscles 3. Joints 4. Sensory organs 5. Internal organs Sensory stimuli include: 1. Taste 2. Touch 3. Smell 4. Hearing 5. Vision Sensory impulses go to the spinal cord and brain 9

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 10

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The Reflex Arc Reflex arc – specialized nerve pathway that does not require conscious thought Examples: 1. Pupil constriction/expansion response to light 2. Pulling back hand from hot surface 3. Kicking foot out when certain tendon is hit Pathway: Sensory neuron Interneuron Motor Neuron 12

Anatomy of the Nervous System Functions: 1. Control and coordinate functions throughout the body 2. Respond to internal and external stimuli 2 Subsystems: 1. Central Nervous System (CNS) Brain Spinal Cord 2. Peripheral Nervous System (PNS) Attach rest of body to CNS 13

Anatomy of the Nervous System 14 Parts of Central Nervous System: 1. 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 2. Spinal Cord: major communication link between brain ad rest of body

Anatomy of the Nervous System 15 Parts of the Peripheral Nervous System: 1. Somatic Nervous System regulates activities under conscious control 2. Autonomic Nervous System controls automatic or involuntary responses contributes to homeostasis by managing other body systems A. Sympathetic nervous system – responds to internal and external demands; “fight or flight” B. Parasympathetic nervous system – returns the body to a balanced state; “rest and digest”

The Endocrine System Not So Rapid Response System 16

Hormones 17 Hormones - chemicals that travel the circulatory system to specific organs or cells 1. 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 2. Non-steroid Hormones Amino acid-based Attach to receptor on cell membrane Inside cell, hormone triggers chemical reactions in cell

Endocrine Glands 18 Gland – an organ that produces and secretes chemicals Major glands: 1. Pituitary – master gland; controls other glands 2. Thyroid – controls metabolism 3. Parathyroid – maintains calcium levels in blood/bone 4. Adrenal – “fight or flight”; regulates sodium/potassium levels; anti-inflammatory 5. Pancreas – controls blood glucose 6. Ovaries – produces eggs; hormones estrogen and progesterone 7. Testes – produces sperm; hormone testosterone

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

Feedback Mechanisms 20 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: 1. Hypothalamus & pituitary monitor hormone levels in blood 2. Level drops: message sent to increase production of hormone 3. Level rises: message sent to cancel first message

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

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

Feedback Mechanisms 23 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

Diabetes 24 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: 1. Allow glucose to diffuse across membrane into cell where it is converted to ATP 2. Stores excess ATP made by the cell as glycogen in skeletal muscle & liver cells 3. Also stores excess ATP as triglycerides in fat tissue

Diabetes 25 Function of Pancreas: 1. Secrete insulin to reduce total blood sugar level 2. Secrete glucagon to increase total blood sugar level from stored supplies of glycogen and triglycerides

Diabetes 26 Types of Diabetes: 1. Type 1- usually diagnosed in people under 30, including children; hereditary; Cannot produce insulin Must take insulin multiple times/day Cannot be prevented/reversed 2. 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

Effects of Uncontrolled Diabetes 27 Body cells cannot access and adequate supply of cellular energy to carry out normal function 1. Blindness 2. Kidney failure 3. Heart attacks 4. Circulatory issues 5. Tissue death