Chapters 31 and 34 Nervous and Endocrine Systems The HUMAN BODY Chapters 31 and 34 Nervous and Endocrine Systems

Chapter 31.1 The Neuron Objectives Identify the functions of the nervous system Describe the function of neurons Describe how a nerve impulse is transmitted

NERVOUS SYSTEM Function: Send and receive messages within the body Respond to stimuli Systems: -Central Nervous System -Peripheral Nervous System Central nervous system – brain and spinal cord (relays messages, processes information, analyzes information) Peripheral nervous system – receives information from environment and relays commands from CNS to organs and glands

Nerve Cells AKA Neurons Neuron- basic unit of structure and function of the nervous system Bundles of neurons form nerves Neuron – cells that transmit electrical signals (impulses) Nerves – bundles of neurons; may have only a few neurons or hundreds/thousands of neurons

Parts of a Neuron: -Dendrite -Cell Body -Axon -Myelin sheath (speeds up impulses) -Axon Terminals Cell body – largest part of neuron contains nucleus and much of cytoplasm most of metabolic activity of cell takes place in cell body Dendrite – short, branched extensions spreading out from cell body carry impulses from environment or other neurons TO cell body (like a vein carries blood TO heart) Axon – long fiber that carries impulses AWAY from cell body Axon terminals – small swellings at end of axon Myelin sheath – insulating membrane; impulses jump from node to node, which increases the speed at which impulse travels Neurons may have dozens of dendrites but usually only axon SHOW students how impulse travels along neuron; show previous slide to show how neurons connect and impulse travels from neuron to neuron

Types of Neurons Sensory Neurons: Impulse from sense organ to spinal cord/brain Motor Neurons: Impulse from brain/spinal cord to muscles and glands Interneurons: Connect sensory and motor neurons Three types of neurons depending on the direction impulse travels

Nerve Transmission Messages are electrical and chemical signals An electric charge is conducted down a neuron (Dendrite to axon) Axon is covered in an insulating layer called a myelin sheath to speed up impulses As it reaches the end of the axon, chemicals (neurotransmitters) are released across the synapse (gap between neurons) to the next neuron The message continues neuron to neuron Nerve impulse is similar to flow of electrical current through a metal wire Nerve transmission begins when neuron is stimulated by another neuron or environment Impulse travels along the neuron like a row of dominos falling. Synapse – location at which neuron can transfer an impulse to another cell at synapse, neurotransmitters are released into the gap b/w neurons; these chemicals transmit the impulse across the gap

Nerve Impulse Videos Neurons: Nerve Cells Describe the path of nerve transmission that allows the batter to hit a ball. Reflexes How is a reflex different from the example of the batter hitting a ball in the previous video clip? Path of nerve transmission that allows batter to hit ball: Batter senses the ball with eyes (sense organ) that transmits this through sensory neuron to brain Brain sends message to muscle via motor neuron to allow batter to hit ball Sensory neurons connect with motor neurons in brain with interneurons Review also how message transmits from one neuron to another: dendrite picks up impulse electrical impulse travels through cell body and down axon at axon terminal, electrical impulse causes release of neurotransmitters (chemical) that travel across synapse neurotransmitters picked up by dendrite of next neuron and impulse continues Reflex different from batter hitting ball: with reflex the sensory impulse is picked up by sensory neuron and travels to spinal cord spinal cord immediately sends impulse back to muscle through motor neuron for immediate response impulse does not go to brain! brain receives the information AFTER you have responded (by moving) reflexes protect us by allowing us to respond faster in emergency situations

Check-in What is the function of the nervous system? Send and receive messages and respond to stimuli Basic unit of structure and function of nervous system Neuron (nerve cell) Part of neuron that receives the impulse Dendrite

Check-in Type of neuron that sends message from sense organ to spinal cord/brain Sensory neuron Type of neuron that connects sensory and motor neurons Interneuron

Chapter 31.2 Central Nervous System Objectives Discuss the functions of the brain and spinal cord Discuss the effects of drugs on the brain

Central Nervous System Brain- control center; transmits and receives messages Cerebrum Cerebellum Brain Stem (midbrain, pons, medulla oblongata.) Spinal Cord- connects brain with rest of the nervous system CNS like the CPU of a computer CNS is protected by body: - skull and vertebrae protect brain and spinal cord - brain and spinal cord wrapped in 3 layers of connective tissue called meninges - b/w meninges and CNS tissue is space that is filled with cerebrospinal fluid (shock absorber as well as allowing for xchng of nutrients/wastes Brain: contains about 100 billion neurons (many of which are interneurons); mass of about 1.4 kg Cerebrum – largest part; responsible for voluntary or conscious activities of body; intelligence, learning, judgement right and left sides separated by band of tissue called corpus callosum right side controls left side of body and vice versa right side – creativity and artistic ability left side – analytical and mathematical ability Cerebellum – second largest part of brain; located at back of skull; responsible for coordination and balance Brain stem – connects brain and spinal cord; controls important functions like blood pressure, heart rate, breathing, swallowing - keeps body functioning even when you are asleep or unconscious - midbrain (uppermost part) - pons (little lobe) - medulla oblongata (thicker bump at top of spinal cord) Spinal cord – 31 pairs of spinal nerves branch off from spinal cord, connecting brain to other parts of body - certain kinds of information, including many reflexes, are processed directly in spinal cord - reflex is a quick automatic response to a stimulus

Brain function fun! The Brain 7 1/2 minute video clip – have students complete video guide while watching (review the questions at end) introduction to brain and its power Brain stem Cerebellum Cerebrum and hypothalamus Cerebral cortex Parts of cerebral cortex Hemispheres of brain

Addiction and the Brain Dopamine – neurotransmitter released with pleasurable activities Addictive drugs cause large release of dopamine (resulting in “high”) Brain reacts by reducing number of receptors for dopamine  normal activities no longer produce the pleasure they once did

Check-in Part of brain that controls balance Cerebellum Part of brain that controls heart rate Brain stem (medulla oblongata) Part of brain that controls thinking Cerebrum (frontal lobe) Part of brain that controls body temperature Hypothalamus

Check-in Neurotransmitter associated with pleasure Dopamine Why do addictive drugs create a cycle in which more and more is needed to get the “high”? Because brain responds to excess dopamine released when they are taken by decreasing the number of dopamine receptors

Chapters 31.3 and 31.4 Peripheral Nervous System & Senses Objectives Discuss the functions of the sensory division of the peripheral nervous system Identify the five sense organs and the sensory receptors associated with each Discuss the functions of the motor division of the peripheral nervous system

Peripheral Nervous System Link between the central nervous system and the rest of the body Network of nerves throughout the body *Made of many neurons Consists of all nerves that are not part of brain and spinal cord Cranial nerves in the head and neck Spinal nerves in rest of body

Sensory Division Transmits impulses from sense organs to central nervous system Uses sensory receptors Chemoreceptors Photoreceptors Mechanoreceptors Thermoreceptors Pain receptors Sensory division: transmits impulses from sense organs to CNS Sensory receptors (neurons that react directly to stimuli from environment) react to a specific stimulus by sending impulses to other neurons and eventually to CNS - located throughout body, but concentrated in sense organs (eyes, inner ears, nose, mouth, skin) Type of receptor Responds to Found in Chemoreceptors: chemicals nose and taste buds Photoreceptors: light eyes Mechanoreceptors: touch, pressure, vibrations, stretch skin, skeletal muscles/ligaments/tendons, inner ears, hair follicles Thermoreceptors: temperature change skin, hypothalamus Pain receptors: tissue injury throughout body (except brain)

SENSES Vision- eyes Hearing and Balance- ears Smell and taste- nose and mouth Touch- skin Vision – photoreceptors in retina of eye rods – light but no color; cones – less sensitive, but see color blind spot – no photoreceptors where optic nerve passes through the back of the eye Hearing / Balance hearing: sound vibrations cause eardrum to vibrate; vibrations picked up by ear bones; vibrations of bones cause pressure waves in fluid filled inner ear which cause hair cells in ear to pick up signals which are transmitted to neurons balance: semicircular canals monitor position of body in relation to gravity Smell and Taste Sense of smell – ability to detect chemicals; contributes greatly to sense of taste (try eating while holding nose – much of taste disappears when you cannot smell) Sense of taste – also chemical detection (by taste buds); taste buds detect salty, bitter, sweet, sour Touch – all regions of body (amt dependent on # receptors) – most receptors in fingers, toes, face skin is largest sense organ

Motor Division Transmits impulses from central nervous system to muscles or glands Somatic nervous system: regulates activities under conscious control Autonomic nervous system: regulates activities that are automatic or involuntary Motor division: transmits impulses from CNS to muscles or glands - somatic nervous system – regulates activities under conscious control (eg., movement of skeletal muscles) some also involved with reflexes (eg., reflex arc that bypasses brain – spinal cord is interneuron used to connect sensory and motor nerves) and can act with or w/o conscious control - autonomic nervous system – regulates activities that are automatic or involuntary

Check-in Peripheral Nervous System Sensory Division Motor Division Impulses from sense organs to CNS Impulses from CNS to muscles/glands Somatic Autonomic Conscious control Involuntary control

Check-in Hearing/balance Smell Taste Touch Vision Chemoreceptor Mechanoreceptor Pain receptor Photoreceptor Thermoreceptor

Chapter 34.1 and 34.2 Endocrine System Objectives Describe the structure and function of the endocrine system Identify the functions of the major endocrine glands

ENDOCRINE SYSTEM Function- produce chemical messengers (hormones) from glands to regulate certain body activities Think about a time when you were startled or frightened. How did you feel? - rapid heart rate - shortness of breath - sweaty palms These physical reactions are due to nerve and hormone action We will learn about hormones in this section on the endocrine system, in particular what the major glands do for the human body

What are hormones? Glands? Hormone: chemical messenger Gland: organ that produces and releases a substance Exocrine: release substances out of body or into digestive tract Endocrine: release hormones directly into blood Endocrine system involves glands that produce hormones hormones are chemicals released in one part of the body that travel in the bloodstream and affect other parts of the body hormones bind to chemical receptors on cells – cells that have receptors for a particular hormone are called target cells Hormones are regulated by feedback mechanisms that function to maintain homeostasis in general terms, an increase in a substance (hormone) “feeds back” to inhibit the process that produced the hormone in the first place Glands – an organ that produces and releases a substance exocrine glands: exo=outside release substances directly to organs that use them (include those that release sweat, tears, digestive juices) sweat gland – release sweat to surface of skin sebaceous gland – release oil (sebum) to surface of skin salivary gland – release saliva to inside of mouth endocrine glands: endo=within release their secretions directly into the bloodstream We will focus on endocrine glands in this section

Glands of Endocrine System Head Region: -Pituitary: controls other glands -Pineal Gland: regulates sleep and wake cycle, along with other basic functions -Hypothalamus: controls secretions of the pituitary gland (link between endocrine and nervous system) Pituitary – bean sized structure that dangles on a slender stalk of tissue at the base of the skull (located below the hypothalamus in the brain) divided into an anterior and posterior part produces a great many hormones that control other glands produces growth hormone that affects how tall you will grow Pineal gland Hypothalamus – part of the brain above and attached to the posterior pituitary gland controls the secretions of the pituitary gland

Glands of the Endocrine System Neck Region: -Thyroid: regulates metabolism (rate at which food is turned into energy) -Parathyroids: maintains homeostasis in blood calcium levels Thyroid gland – located at base of neck and wrapped around the upper part of the trachea produces a hormone (thyroxine) that regulates metabolic rate (rate at which food is turned into energy) Parathyroids – four glands found on back surface of thyroid gland work with the thyroid gland to regulate the amount of calcium in the blood Thymus gland – located in front of chest; large in childhood and shrinks in adulthood helps certain WBC develop and play their part in body’s defenses

Glands of the Endocrine System Abdominal Region: -Adrenals: helps body prepare for and deal with stress (fight or flight) -Pancreas: Releases insulin and glucagon to regulate level of glucose in blood Adrenal glands – located on top of the kidneys produce the “fight or flight” response to stress by releasing epinephrine and norepinephrine increase heart rate, blood pressure, and blood flow to muscles cause air passages to open wider (allow for increase flow of oxygen) stimulate release of extra glucose into blood stream Pancreas – located behind the stomach produces insulin (stimulates cells in the liver and muscles to remove sugar from blood and store as glycogen or fat) and glucagon (stimulates the liver to break down glycogen and release glucose back into the blood) insulin is released after eating as blood glucose levels rise (to bring it down) after 1-2 hours, blood glucose levels drop and glucagon is released to bring blood glucose level back up Diabetes mellitus – when pancreas fails to produce or use insulin properly Type 1: autoimmune disorder; usually begins in childhood (before age 15) little or no secretion of insulin must follow strict diet and take daily injections of insulin Type 2: most commonly begins after age 40 low or normal amounts of insulin produced, but cells not able to use it properly (interaction b/w insulin and insulin receptors inefficient) early stages – controlled by diet and exercise

Glands of the Endocrine System Reproductive Region: -Ovaries (females): produce eggs and estrogen to create female characteristics -Testes (males): produce sperm and testosterone to create male characteristics Gonads – body’s reproductive glands produce gametes (egg or sperm) and sex hormones Female – ovaries produce eggs (gametes) produce estrogen: required for egg development and female physical characteristics (development of reproductive system, widening of hips, development of breasts) produce progesterone: prepares uterus for arrival of developing embryo Males – testes produce sperm produce testosterone: required for normal sperm production and development of male physical characteristics (growth of facial hair, increase in body size, deepening of voice)

Check-in Controls the pituitary gland Regulates metabolism Hypothalamus Regulates metabolism Thyroid Regulates sleep/wake cycle Pineal Controls other glands Pituitary

Check-in Produces eggs and estrogen Ovary Helps deal with stress (fight or flight) Adrenal Maintain blood calcium levels Parathyroid Regulates blood glucose/sugar levels Pancreas