The Nervous System

1. The Nervous System

2. Functions • The nervous system controls the musculoskeletal system and regulates all the body systems • It is responsible for thought processing, emotions, reasoning/ judgment, memory storage, etc.. • It helps us make sense of what we see, hear, taste, and feel (outer world)

3. Functions • The nervous system is the body’s decision and communication center • Together they control every part of your daily life from breathing to blinking, to memorizing facts for a test, emotions, coordination, thought processing, and much more!

4. Cells in the nervous system are called neurons • The nervous system contains two types of cells- neurons and neuroglia • Neurons are the cells that transmit nerve impulses between parts of the nervous system- make up 10% of brain cells • Neuroglia are the cells that support and nourish neurons- they make up 90% of brain cells

5. Neurons- cells of the nervous system (also called nerve cells) • Nerve cells are excitable when stimulated, they undergo chemical changes that produce tiny travelling waves of electricity- nerve signals that carry messages through the nervous system.

6. A Neuron

7. Parts of a Neuron • Dendrites- receive the message from the axon of another neuron • Cell body- contains all the organelles found in eukaryotic cells • Nucleus- the cell organelle which contains DNA (the “brain” of the cell) • Axon-sends the message to the dendrites of another neuron • Myelin sheath- fatty insulator which protects the axon of a neuron

8. Types of Neurons • Although the nervous system is extremely complex, the principles of its operation are simple. There are three classes of neurons. There functions are best described in relation to the CNS: • Sensory neurons • Interneurons • Motor neuron

9. Sensory Neurons • Takes messages to the CNS • Has specialized endings called sensory receptors that detect changes in the environment • Gather information from the environment, send information to the spinal cord, which then sends information to the brain for interpretation

10. Interneurons • These neurons lie entirely within the CNS • The receive input from sensory neurons as well as other interneurons in the CNS • Next, they sum up all the messages received from these neurons before they communicate with the motor neurons

11. Motor Neurons • Takes messages away from the CNS to an an organ, muscle fiber, or gland • The organ or gland will then carry out our responses to environmental changes

13. The axon and dendrite do not actually touch each other. There is a space called a synapse where neurotransmitters relay messages from the axon to the dendrite of another neuron

14. Neurons “talk” to each other by sending chemicals to each other across a very tiny space called a synapse. Learning happens when neurons “talk” to each other. As the brain makes connections, it actually grows dendrites and makes stronger synapses.

15. Important Neurotransmitters in the Brain

16. The Nervous System has two parts: • Central Nervous system Brain Spinal cord • Peripheral Nervous system All the nerves in the body

17. BRAIN FACTS • The brain accounts for 2% of total body weight • Yet is requires 20% of the body’s blood • Both oxygen and glucose are transported by blood • Without these essential nutrients, brain function quickly deteriorates and dizziness, confusion, and loss of consciousness occur. In only eight minutes of oxygen deprivation, brain damage or death results

18. MORE BRAIN FACTS • Did you know that neurons are the longest cells in your body? You have neurons in your lower back that have axons that reach your toes! Pretty cool, huh? • Your brain is about the size of your two fists put together and weighs about 3lbs. • It is protected by three layers of membranes called the meninges, as well as a special fluid called cerebral spinal fluid • The right side of your brain controls the left side of your body and the left side of your brain controls your right side

19. The Brain The brain can be divided into several parts: cerebrum, cerebellum, and the brainstem. The cerebrum has four parts: Frontal lobe, parietal lobe, occipital lobe, and temporal lobe

20. Cerebrum • It is the largest portion of the brain • It is the last center to receive sensory input and carry out integration before commanding voluntary motor response • Carries out higher thought processes required for learning and memory, and for language and speech

21. Cerebellum • It receives sensory input from the joints, muscles, and other sensory pathways about the present position of body parts • The cerebellum helps us to maintain our balance and posture, and ensures that muscles work together to produce smooth and controlled voluntary movements, and assists in learning new motor skills

22. Brain Stem • Contains the pons, mid-brain, and the medulla oblangota • Responsible for mostly automatic processes such as breathing, heart rate, blood pressure, vomiting, swallowing, and hiccuping

23. Brain Stem Functions!!! • The midbrain acts as a relay station for tracts passing between the cerebrum and spinal cord or cerebellum • It also has reflex centers for visual, auditory, and tactile responses • The pons functions with the medulla oblongota to regulate breathing rate, and has reflex centers concerned with head movements in response to stimuli • The medulla oblongota contains reflex centers for regulating breathing, heartbeat, blood pressure, as well as vomiting, sneezing, hiccupping, and swallowing

24. Spinal Spinal Cord = • The spinal cord is a bundle of nerves that extends from the base of the brain to the lower back • It is protected by individual vertebrae • The spinal nerves that project from the cord between the vertebrae make up the vertebral column • Fluid-filled vertebral discs cushion and separate the vertebrae • If a disc ruptures, the vertebrae press on the spinal cord and nerves. Pain and loss of motor function result spinal nerve compression

25. The spinal cord provides a means of communication between the brain and the peripheral nerves that leave the cord • If the spinal cord is severed at the neck region, a loss of sensation and voluntary control occurs in all four limbs (quadriplegic) • If it is cut at the thoracic region, the lower body and leg are affected (paraplegic) • The spinal cord is also a center for reflex action

26. SPINAL REFLEX • A reflex is a rapid, involuntary, predictable response to a stimulus. • Most reflexes are concerned with survival and defending the body from harm • A reflex occurs in a neural circuit that does not involve the higher regions of the brain where consciousness and awareness occur

27. In a reflex, the sensory neurons send nerve impulses that travel to the spinal cord,then to motor neurons that quickly send message to the effector muscle

28. Stroke- a serious condition in which there is a reduced or blocked blood flow to the brain

29. Test to see if one is having a stroke: • S-Ask the person to SMILE • T- Ask the person to TALK- say a simple sentence • R- Ask the person to RAISE BOTH ARMS Sometimes symptoms of a stroke are difficult to identify. The lack of awareness can spell disaster. The longer the person goes without medical attention, the more likely permanent brain damage will set in. Call 911 immediately if the person can not do one of the following tasks above.

30. Multiple sclerosis is a degenerative disease in which the myelin sheath is damaged. This results in loss of the nerve impulse which causes the patient to begin to experience muscle fatigue, weakness, and eventually loss of muscle control.

31. The Peripheral Nervous System • The autonomic system of the PNS can be divided into two parts: the sympathetic nervous system and the parasympathetic nervous system • Our muscles, as well as the organs of our body such as the heart, lungs, and intestines are regulated by the autonomic system

32. The peripheral nervous system is made up of all the nerves in the body

33. Autonomic Nervous System Sympathetic Nervous System Parasympathetic Nervous system Neurotransmitter is nor epinephrine Important during emergency situations when you must fight back or run away (“fight or flight” response) Accelerates heartbeat, dilates the bronchi, activates muscles with added glucose and O2 (because of adrenaline), inhibits digestive tract, constricts blood vessels, raises blood pressure Responsible for all the responses we associate with in a stressful state Neurotransmitter is acetylcholine Promotes all the internal responses we associate with “rest and digestion” Opposite to the sympathetic system, it causes the pupil of the eye to contract, promotes digestion of food, and slows heartbeat Responsible for the responses we associate with in a relaxed state

34. The sympathetic nervous system prepares us for a response in emergency situations (flight or fight response) It signals the release of the hormone adrenaline from your adrenal glands to put extra glucose into your blood.

35. The parasympathetic nervous system is in control when we are resting or digesting.

36. Careers for those who think the brain is pretty neat… • Physical therapists- may work with rehabilitation of patients involved in a brain injury, sports injury, or accident victims. Avg. Salary: $75,000 yearly • Speech therapists-works with patients who need to improve their speech $60, 000 • Occupational therapists- work with patients who have suffered brain damage or patients involved in an accident, or recovering from surgery; teach them how to perform daily living tasks. $65,000 • Nurse $60,000 • Neurologist- a doctor who specializes in treating disorders of the nervous system $150,000 • Neurosurgeon- doctor who performs brain or spinal cord surgery +$200,000

37. Caring for the Nervous System • Avoid the use of alcohol and drugs (they can cause permanent changes in your brain!)  • Wear a helmet when involved in certain physical activities and a seatbelt when in a car. • Get 8 to 10 hours of sleep a night • Eat nutritious meals with plenty of vitamin rich foods • Learn new things- it helps build stronger synapses between the neurons in your brain …that’s right, so study for your upcoming test…

38. The Nerve Impulse • The nervous system uses the nerve impulse to convey information. • The axon is more negatively charged inside than it is outside when it is not conducting an impulse. This is called a resting potential. • The existence of the polarity (charge difference) correlates with the difference in ion distribution • The concentration of sodium ions (Na+) is greater on the outside of the axon and the concentration of potassium (K+) is greater on the inside

39. The Sodium Potassium Pump • The sodium potassium pump is a membrane protein that actively transports Na+ ions outside and K+ ions across the membrane. The work of the pump maintains the unequal distribution of these ions • The unequal distribution of ions causes the inside of the axon to be negative compared to the outside • picture

40. An Action Potential (nerve impulse) • An action potential is a nerve impulse, and consists of an electrochemical change that occurs across an axomembrane • It is an all or none phenomenon. If a stimulus causes the axomembrane to depolarize to a certain level, called threshold, an action potential occurs • The action potential requires two types of gated channel proteins in the membrane, one allows Na+ to enter the inside, and the other allows K+ to exit

41. During depolarization, Na+ moves into axon, and during repolarization, K+ moves to the outside of the axon • pic

42. The Limbic System and Higher Mental Functions

43. . • When nerve impulses traveling along an axon reach an axon terminal, gated channels for calcium ions (Ca2+) open. The sudden rise in Ca2+ stimulates synaptic vesicles to merge with the presynaptic membrane, and neurotransmitters are released into the synaptic cleft. They diffuse across the cleft to the presynaptic membrane, where they bind with specific membrane proteins

44. Drug Actions at a Synapse

45. Heroin • Once injected into the vein, a feeling of euphoria, along with relief from any pain, occurs within 3-6 minutes • Side effects include: nausea, vomiting, restlessness, anxiety, mood disorders, and respiratory and circulatory depression • Heroin binds to receptors meant for endorphins, the special neurotransmitter that kills pain and produce feelings of tranquility. With time, the body makes less endorphins • Tolerance develops so that the user needs more just to prevent the withdrawal symptoms (tremors, abdominal cramps, vomiting, increase in systolic pressure, and restlessness) • Use can lead to respiratory failure and death

46. Cocaine A powerfully addictive type of stimulant drug It can be smoked, injected, or snorted Because it increases heart rate- even first time users run the risk of a fatal heart attack!

47. Cocaine and The Brain • Sold in powder form, and as crack, a more concentrated extract • Cocaine prevents the synaptic uptake of dopamine, a brain chemical that is responsible for pleasure and movement, and causes the user to experience a euphoric feeling • The high feeling can last for several minutes • A cocaine binge can go on for days, followed by a crash, where the user is fatigued, depressed, irritable, and has trouble concentrating

48. Cocaine abusers tend to have psychotic behavior, such as hallucinations, mood disturbances, repetitive behaviors, feelings of paranoia…Trained mental health professionals can confuse a schizophrenic from a cocaine addict because they behave so much alike.

49. Cocaine Effects on the Body • Cocaine causes extreme physical dependence • With continued use, the body begins to make less dopamine to compensate for the seemingly excess supply • The user then experiences tolerance, withdrawals, and an increased need for the drug • Overdosing on cocaine can cause seizures, and cardiac and respiratory arrest • Long- term use can cause brain damage • Babies born to addicts suffer withdrawal symptoms and may have neurological and developmental problems

50. A PET scan shows how a brain on cocaine uses less glucose, and thus is less active than a normal brain- red areas indicate utilizing a lot of glucose, yellow area-using less glucose, and blue is the least