The Human Brain: The Most Complex Entity in the Known Universe

1. Q: What is the most complexentity in the known universe? • A: The human brain • The human brain consists of about 100 billion nerve cells! • A given neuron may have several thousand connections; therefore, the human brain has at least 100,000,000,000,000 web-like connections. WOW! • One hundred trillion connections is larger than the total number of atomic particles that make up the known universe (Thompson, 3).

2. Biology and Behavior The Nervous System – • All living organisms have a nervous system. • The nervous system varies depending on the species. • The human nervous system is the most complex of all species. • The human nervous system is involved in thinking, dreaming, feeling, moving, and everything that makes you … wellyou! • The nervous system also regulates all our internal functions. • Division – • The nervous system is divided into two main parts: • The Central Nervous System (CNS) • The Peripheral Nervous System (PNS)

3. The Central Nervous System • The central nervous system consists of the brain and the spinal cord. • The spinal cord extends from the brain and down the back. • The spinal cord is a bundle of neurons about as thick as an adult’s thumb. • The spinal cords function is to transmit messages between the brain and the muscles, organs, and glands through the body. • The spinal cord is also involved in spinal reflexes. • A spinal reflex is a simple, automatic response to a sudden stimulus – where the sensory receptor is stimulated and the message is sent to the spinal cord only and a response is sent immediately from the spinal cord to the extremity.

4. The Peripheral Nervous System • The peripheral nervous system is made up of all the neurons that send messages to the central nervous system from all parts of the body. • The peripheral nervous system is divided into two parts: • The Somatic Nervous System • The Autonomic Nervous System

5. Nervous System Central NS Peripheral Brain Spinal Cord Somatic Autonomic Sympathetic Parasympathetic Organization of the Nervous System

6. Divisions of the Nervous System

7. The Somatic Nervous System • The somatic nervous system transmits sensory messages to/from the central nervous system. • The somatic nervous system is activated by touch, pain, change in temperature, and changes in body position, as well as muscular movement. • The somatic nervous system allows us to experience the sensations of hot and cold, and to feel pain and pressure. • The somatic nervous system sends messages to the muscles and glands and helps us maintain posture and balance.

8. The Autonomic Nervous System • The “autonomic” means “occurring involuntarily” or automatically. • The autonomic nervous system regulates the body’s vital functions, such as heartbeat, breathing, digestion, and blood pressure. • The autonomic nervous system is involved in the experience of emotion.

9. The Autonomic Nervous System (continued) • The autonomic nervous system is divided into two parts: • a) the sympathetic • b) the parasympathetic • These two parts work in opposition. • The sympathetic is activated when a person is going into action, perhaps because of some stressful situation. • The sympathetic nervous system prepares the body either to confront the situation or to run away. This is called the “flight or fight” response. • Example: Attacked by a large angry dog – The sympathetic nervous system suppresses digestion, increases the heart and respiration rates, and elevates the blood pressure, preparing the body to deal with the situation (run or fight). • The parasympathetic nervous system restores the body’s reserves of energy to normal levels, after an action has occurred.

10. Sympathetic Nervous System *Flight or Fight Response *Automatically accelerates heart rate, breathing, dilates pupils, slows down digestion.

11. Parasympathetic Nervous System Automatically slows the body down after a stressful event. Heart rate and breathing slow down, pupils constrict and digestion speeds up.

12. Will Explain Why We FEEL…… Neural and Hormonal Systems Nervous Strong Sick Pain

13. It all Starts with the Neuron

14. The Neuron = Nerve Cell • Neurons run through our entire bodies and communicate with each other. • Each person has approx. 100 billion neurons, most of which are found in the brain. • There are three basic types of neurons: • Motor neurons • Sensory neurons • Interneurons

15. Sensory Neurons(Afferent Neurons) • Take information from the senses to the brain.

16. Motor Neurons(Efferent Neurons) • Take information from brain to the rest of the body.

17. Inter Neurons • Take messages from Sensory Neurons to other parts of the brain or to Motor Neurons.

18. Neural Anatomy & Physiology • Every neuron consists of: a cell body (soma), dendrites, and an axon with axon terminals

19. Neural Anatomy & Physiology Synapse Synapse Neurotransmitters (chemicals held in terminal buttons that travel through synaptic gap)

20. Neural Anatomy & Physiology (continued) • Thecell body (soma)produces energy that fuels the activity of the cell. • Dendritesare thin fibers which branch out from the cell body. • Dendrites receive information from other neurons and pass the message through the cell body. • Theaxoncarries messages away from the cell body and towards the axon terminals. • A neuron has many dendrites but only one axon. Axons vary greatly in length.

21. Neural Communication Neurons • The building blocks are neurons (i.e., nerve cells). • Each neuron consists of a cell body (soma) and its branching fibers, called dendrites. • The information is passed from soma to the axon down to the axon terminals across the synaptic cleft to other neurons or to muscles or glands. • A layer of fatty tissue, called myelin sheath, insulates the axons of some neurons and helps speed the electrical transmission (impulse). • Evidence of myelin sheath’s importance appears in multiple sclerosis – a disease in which myelin sheath degenerates. • Depending on the type of neuron, the neural impulse (electrical impulse) travels at speeds ranging from a sluggish 2 miles per hour to 200 or more miles per hour.

22. Candy Neuron * Cell Body (Soma) – Marshmellow (1) * Dendrites – Pretzels (6) * Axon – Twizzler (1) * Terminal Branches – Mike And Ikes (6) * Terminal Buttons - M&Ms (6) Directions: Label AND Define each part of your neuron – then snap a picture of your completed neuron and upload this picture to Edmodo. *For 2 extra credit points, upload a picture of YOU with your candy neuron to Edmodo! Candy Neuron Selfie!!!

23. Neural Communication • The fluid interior of a resting axon has an excess of negatively charged ions, while the fluid outside the axon membrane has more positively charged ions. • This positive outside / negative inside polarization is called the RESTING POTENTIAL. • Neurons at rest have a slightly negative charge • Neuron firing is an electrochemical process *electrical inside the neuron *chemical outside the neuron (in the synapse in the form of neurotransmitters)

24. Neural Communication • A neuron fires an impulse when it receives signals from sense receptors stimulated by pressure, heat, light, or a chemical message from adjacent neurons. • This impulse is called the ACTION POTENTIAL – it is a brief electrical charge that travels down the interior of the axon, like a line of dominoes falling, each one tripping the next ion channel changing the polarity of the nerve cell (all the way down the axon and into the axon terminal). • A handful of neurons together produce enough power to light up a flashlight bulb. • Neurons, like batteries, generate electricity from chemical events. • This involves the exchange of electrically charged atoms, called ions.

25. Neural Communication • From hundreds, even thousands of other neurons, a single neuron receives signals on its dendrites and cell body. • Some signals are excitatory, somewhat like pushing a neuron’s accelerator. • Some signals are inhibitory, more like pushing the brakes, signaling the neuron to stop sending an electrical impulse. • The neuron’s threshold for firing an impulse is an all-or-none response, like a gun – it either fires or it doesn’t. • Neurons interweave so intricately that even with a microscope it is hard to see where one neuron ends and another begins. • The axon terminal of one neuron and the dendrite of another neuron are separated by a gap less than a millionth of an inch wide. This gap is called the SYNAPSE.

26. Let’s Do the Neuron Dance!!!

27. Neurotransmitters • Chemical messengers released by terminal buttons through the synapse • We should know at least 5 types and what they do.

28. Norepinephrine • Circuits in the brain arise from a small collection of neurons in the brain stem and project to all forebrain structures. It is thought to moderate levels of arousal and consolidate memory (interneuron).

29. Acetylcholine • Its function is motor movement and maybe memory. To much and you will…. Not enough and you will…. Lack of ACH has been linked to Alzheimer’s disease.

30. Dopamine Deals with motor movement and alertness. Lack of dopamine has been linked to Parkinson’s disease. Too much has been linked to schizophrenia.

31. Serotonin Function deals with mood control Lack of serotonin has been linked to depression This is one mildly depressed sheep!!!  I guess we should try to shear her up (get it?)

32. Endorphins • Function deals with pain control • Produces “runner’s high” • We become addicted to endorphin- causing feelings.

33. Drugs can be….. Agonists- make neuron fire / produce temporary high by amplifying sensations of arousal or pleasure Antagonists- stop neural firing / inhibit Reuptake Inhibitors- block reuptake; the sending neuron normally reabsorbs excess neurotransmitter molecules