1. The Nervous System Consists of groups of neurons and neuroglia found in two major systems 1.Central Nervous System Brain Spinal Cord 2.Peripheral Nervous System Motor Nerves Sensory Nerves Interneurons

2. Two Major Cell Types Neurons Neurons are electrically excitable cells in the nervous system that process and transmit information Neuroglia (Glial Cells) Glia are estimated to out-number neurons by about 10 to 1 in the brain The main functions of glial cells are to: –surround neurons and hold them in place (known as the « glue » of the nervous system –form myelin –participate in signal transmission –supply nutrients and oxygen to neurons, –insulate one neuron from another, –and to destroy pathogens and remove dead neurons

3. A Generalized Neuron Axon terminals Myelin sheath Nodes Cell body Axon Nucleus Dendrites

4. The Neuron Although there are several types of neurons, they all have certain features in common Cell body – contains most of the cytoplasm, nucleus, most metabolic activity occurs here. Dendrites – carry impulses from the environment or from other neurons toward the cell body Axon – carries impulses away from the cell body towards the axon terminals (axon buds) Myelin sheath – accelerates the transmission of electric signal across the axon

5. Generalized Nerve Cell - Detailed

6. Neurons in Culture

7. Schwann Cells and the Myelin Sheath Schwann cells provide myelination to axons in the peripheral nervous system (PNS). They also have phagocytotic activity and clear cellular debris that allows for regrowth of PNS neurons.

8. Myelinization of the Axon by an Oligodendrocyte Myelin Sheath Axon Oligodendrocyte

9. Myelin Sheath

10. Astrocytes (type of glial cell), Blood vessels and Neuron Blood vessels Cell body of astrocyte Astrocyte Branches Cell body of neuron Astrocyte foot

12. Microgliocyte (Macrophagic)

13. The Nervous Impulse The transmission of an electrical impulse across the axon is called an Action Potential An action potential occurs when the normally negatively charged environment within the axon becomes momentarily positively charged How does this happen?

14. Sodium-Potassium Pump at Resting Potential The electrical potential of a neuron is 70 millivolts (1/20 the voltage of a 1.5 V battery)

15. Neuron at Resting Potential

16. Resting to Action Potential The neuron moves from a resting potential (axon is –vely charged) to an action potential (axon becomes momentarily +vely charged) when a stimulus causes Sodium ion gates/channels to open and allow Na + ions to flow into the axon and thus make it positively charged

17. Nerve Impulse & Action Potential

18. Propagation of Action Potential As the Na + gates open along the axon, K + gates also open allowing K + ions to flow out of the axon and thus return the axon to resting potential The nervous impulse is self-propagating. That is that, an impulse at any point on the membrane causes an impulse at the next point along the membrane by opening the Na+ channels

19. Propagation of Action Potential

20. The All-or-Nothing Principle A nervous impulse/action potential is only caused when a stimulus from the environment is strong enough reach a neuron’s Threshold A threshold is the minimum level of stimulus need to cause an action potential The nervous impulse, however, is the same no matter how strong the stimulus is as long as it has reached the neuron’s threshold.

21. Passing on the Message When the action potential reaches the axon terminal, the neuron may pass it’s impulse on to the next cell The next cell may be another neuron, or it may be a muscle cell, if the neuron is a motor neuron

22. The Synapse A synapse is the location where a neuron can transfer an impulse to another cell The synapse is the cleft, or gap between the axon terminal of one neuron and the dendrite of another neuron or muscle cell The axon terminals contain vessicles that carry neurotransmitters They release the neurotransmitters into the synaptic cleft which bind to receptor proteins on the adjacent cell Here, the neurotransmitter either propagates another action potential in the adjacent neuron or causes a muscle to contract

23. The Synapse Vesicle Axon Axon terminal Synaptic cleft Neurotransmitter Receptor Dendrite of adjacent neuron Direction of Impulse

24. Nervous Propogation

25. Cell Body Synaptic Vessicle Axon Terminal Axon

26. Ionic Gates/Channels

27. Neural Interactions

29. The Nervous System CNS & PNS

34. The Central Nervous System

35. Central Nervous System Control centre of the body Processes, analyses information and relays messages Consists of Brain Spinal cord Very well protected by the skull, vertebrae and meninges

36. Meninges Three layers of connective tissue that surround both brain and spinal cord Between the meninges we find the cerebrospinal fluid which bathes the CNS and acts as a shock absorber Cerebrospinal fluid also allows the exchange of nutrients and waste products between blood and nervous tissue

38. Gray vs. White Matter Cerebrum consists of two surfaces: –Cerebral Cortex Gray matter (~1 inch thick) Densely packed nerve cell bodies –Inner layer White matter Axons covered by myelin sheaths which give it its white colour (cholesterol)

39. Gray vs. White Matter

40. The Brain – Parts Major parts: Cerebrum Cerebellum Brain stem (pons & medulla oblongata) Thalamus Hypothalamus Pineal gland Pituitary gland

42. Cerebrum Largest structure in human brain Voluntary activities, intelligence, learning, judgement Deep groove running from front to back separates brain into left & right hemispheres Each hemisphere is divided into four lobes named after the bones that cover them Left half controls right side of the body and right half the left side Right side is associated with creativity and artistic talent Left side is associated with analytical & math skills Folds & grooves serve to increase surface area of the brain

46. Cerebellum 2 nd largest structure Although the commands to make muscles contract comes from the cerebral cortex, the cerebellum coordinates & balances the actions of the muscles so that they move efficiently

47. Brain Stem Pons & medulla oblongata Acts as the brain’s switchboard by regulating the flow of info between the brain and the rest of the body « Primitive » brain that controls the vitals Blood pressure Heart rate Breathing Swallowing

48. Thalamus & Hypothalamus Thalamus Receives info from sensory organs and relays the proper info to the cerebrum Hypothalamus Control centre for the recognition & analysis of hungar, thirst, fatigue, anger, and body temperature

49. Pineal & Pituitary Glands Pineal gland (non-nervous tissue) Releases melatonin which controls sleep-wake cycles Pituitary gland (non-nervous tissue) Produces hormones that regulate many other endocrine glands

52. Evolution of the Vertebrate Brain

54. Penfield & Rasmussen

55. The Spinal Cord Main link between the brain and the rest of the body Reflexes (ex. sneezing, blinking) are processed directly by spinal cord instead of being first sent to the brain in order to make the movement more rapid

56. The Spine

57. The Spine – Whole

58. Peripheral Nervous System

59. The Peripheral Nervous System Divided into two major divisions: –Sensory (transmits impulses from sensory organs to CNS) –Motor (transmists impulses from CNS to muscles or glands) Consists of: –Cranial nerves –Spinal nerves –Ganglia (collections of nerve cell bodies)

61. Motor Division of the PNS Divided into: –Somatic Nervous System (voluntary movement such as the movement of skeletal muscles & arc reflexes) –Autonomic Nervous System (involuntary movement such as heartbeat, peristalsis in digestive tract) Divided into: –Sympathetic NS – like the accelerator –Parasympathetic NS - like the brakes

62. Arc Reflex – Monosynaptic vs. Polysynaptic reflexes

63. Autonomic Nervous System

68. which consists of is divided into that make up which is divided into The Nervous System Sensory nerves Motor nerves Autonomic nervous system Somatic nervous system Central nervous system Peripheral nervous system Sympathetic nervous system Parasympathetic nervous system

69. Drugs & the Nervous System

70. Pharmaceutical Drugs Used to increase alertness, relieve fatigue Used to relieve anxiety, irritability, tension Used to relieve pain Stimulants Depressants Opiates Amphetamines Barbiturates Tranquilizers Morphine Codeine Increase heart and respiratory rates; elevate blood pressure; dilate pupils; decrease appetite Slow down the actions of the central nervous system; small amounts cause calmness and relaxation; larger amounts cause slurred speech and impaired judgement Act as a depressant; cause drowsiness, restlessness, nausea Drug TypeMedical UseExamplesEffects on the body

72. Drugs & the Brain One of the reasons that drugs of abuse can exert such powerful control over our behaviour is that they act directly on the more evolutionarily primitive brain-stem and limbic system structures, which can override the cerebral cortex in controlling our behaviour.

73. Drugs Affect Neurotransmission Almost all drugs work by affecting neurotransmission in one of four ways: 1.Mimic natural neurotransmitters (ex. LSD) 2.Block receptors and thus block neurotransmission (ex; PCP) 3.Block the reabsorption of a neurotransmitter back into the axon terminal after nervous impluse (ex. cocaine) 4.Cause neurotransmitters to be released in greater than normal quantities (ex. methamphetamine)

74. Cocaine Causes the release of dopamine in the pleasure centre of the brain and then blocks its reabsorption back into the axon terminal after the nervous impulse. This causes the adjacent neurons to keep firing and produce even more pleasure Problem: dopamine stores get used up and the user feels depressed without the drug Causes addicts to commit serious crimes and abandon their families and children to get another « hit » Crack users may become addicted even after the first try

81. Opiates Mimic endorphins (natural transmitters) which are used to overcome pain Produce pleasure and a feeling of security, but then the body gets used to the higher concentrations and then can deal without this new concentration. Users who stop suffer from uncontrollable pain and sickness because the body cannot produce enough natural endorphins Include opium, heroin, codeine and morphine

82. Marijuana Active ingredient is THC (tetrahydrocannabinol) Binds to cannabinoid receptors in the brain Alters the messages that affect sensory perception and coordination Receptors are found in the parts of the brain that control memory, thought, concentration, time and depth perception and coordinated movement