1. Chapter 48 ~ Nervous System

2. Nervous systems Effector cells: muscle or gland cells that react to stimuli Nerves: bundles of neurons wrapped in connective tissue Central nervous system (CNS): brain and spinal cord Peripheral nervous system (PNS): sensory and motor neurons

3. Overview of the Nervous System

5. Structural Unit of Nervous System Neuron: structural and functional unit Cell body: nucleus and organelles Dendrites: receive impulses from neurons Axons: carry impulse to another cell Myelin sheath: supporting, insulating layer -Oligodendrocytes (CNS) -Schwann cells (PNS) Synaptic terminals: neurotransmitter releaser Synapse: neuron junction

6. The Schwann (PNS) and Oligodendrocytes (CNS) cells help an impulse move along an axon at extremely fast speeds. The myelin that make up these cells are mostly lipids which are poor conductors of electricity.

7. The Synapse http://www.sumanasinc.com/webcontent/anisamples/ne urobiology/synaptictransmission.html

9. Simple Nerve Circuit Sensory neuron: convey information to spinal cord Interneurons: information integration Motor neurons: convey signals to effector cell (muscle or gland) Reflex: simple response; sensory to motor neurons Ganglion (ganglia): cluster of nerve cell bodies in the PNS Supporting cells/glia: nonconductiong cell that provides support, insulation, and protection http://www.sumanasinc.com/webcontent/anisamples/ neurobiology/reflexarcs.html

11. What is a nerve impulse? 1.Neurons have Membrane potential (voltage differences across the plasma membrane): All cells are slightly more negative inside than outside.  Resting potential of a neuron = -70 mV 2.A nerve impulse occurs when the neuron depolarizes. Depolarization is made possible by specialized ion channels.

12. What is a nerve impulse? 3.Types of ion channels: -Chemically-gated ion channels: open or close when stimulated by a chemical. -Voltage-gated ion channels: open or close when stimulated by a change in membrane potential. 4.Ion channels along the axon open and close, causing an “action potential” to move down along the axon. The axon becomes positive in sections.

13. How is the membrane potential maintained? 1.Sodium-Potassium Pump: By active transport, 3 sodium ions are pumped out for every 2 potassium ions. This pump maintains membraine potential. 2.Some of the ions diffuse back but never reach equilibrium. They diffuse back through Na+ and K+ ion channels (remember “facilliated diffusion”?) 3.High concentration of anions inside the cell include proteins, amino acids, sulfate, and phosphates.

14. How does an action potential send a nerve impulse?

15. How does an action potential send a nerve impulse? 1.Resting State: Na+ and K+ channels are closed. 2.Threshold: Some Na+ open up. If the neuron obtains a particular voltage (i.e. -50 mV), it will trigger depolarization. 3.Depolarization phase: Na+ channels open up very rapidly and Na+ rushes into the cell making it more positive. 4.Repolarization phase: Na+ channels close, but the K+ slowly open. K+ ions leave the cell and the cell becomes more negative again. 5.Undershoot: As the K+ ion channels slowly close, K+ ions continue to leave the neuron causing it to become hyperpolarized.  Refractory Period: when the neuron is insensitive to depolarization; due to the closing of Na+ channels during undershoot.

16. Resting Potential in Neurons: http://www.sumanasinc.com/webcontent/anisamples/ neurobiology/signaling.html Nerve Impulse; Depolarization: http://www.sumanasinc.com/webcontent/anisamples/ neurobiology/signaling.html

17. Saltatory Conduction -In between each Schwann cell is an area of axon exposed to extracellular fluid. These areas are called “Nodes of Ranvier.” -Depolarization takes place at each node. -This propagates an impulse faster as action potentials jump from node to node.

18. Synaptic communication Presynaptic cell: transmitting cell Postsynaptic cell: receiving cell Synaptic cleft: separation gap Synaptic vesicles: neurotransmitter releasers Ca+ influx: caused by action potential; vesicles fuse with presynaptic membrane and release neurotransmitters. Neurotransmitter: the chemical released that causes an impulse in the postsynaptic cell.

19. Synaptic communication The binding of the neurotransmitter to the receptor opens up Na+ channels  Depolarization The neurotransmitters are either degraded by enzymes or recycled by the presynaptic cell. Two types of responses: 1. EPSP (Excitatory postsynaptic potential): excitatory response; action potential stimulus due to Na+ influx 2. IPSP (Inhibitatory postsynaptic potential): inhibitory response; due to K+ movement out of cell and Cl- movement in.

20. Neurotransmitters 1.Acetylcholine (most common) -Both excitatory and inhibitory -Ex. skeletal muscle 2.Biogenic amines (derived from amino acids) -Epinephrine: aka adrenalin; the “fight or flight” hormone; increase the heart rate, blood pressure, and levels of sugar and fat in the blood. -Norepinephrine: excitatory and inhibitory; functions in the autonomic nervous system; low levels in the synaptic cleft is associated with depression and ADD/ADHD. -Dopamine: excitatory; functions in the “reward system” of brain; low levels is associated with depression, ADD/ADHD, and Parkinsons Disease; high levels associated with schizophrenia; associated with feelings of pleasure, and motivation (food, sex); cocaine mimics dopamine.

21. Neurotransmitters -Serotonin: Inhibitory; regulates anger, body temp, mood, sleep, sexuality, appetite; low levels associated with depression, aggressive behavior, OCD, migraines, bipolar, and anxiety disorders. 3.Amino Acids: -GABA (Gamma aminobutyric acid): main inhibitory neurotransmitter -Glycine: inhibitory action in spinal cord, brainstem, and retina -Glutamate: excitatory; associated with learning and memory -Aspartate: excitatory; could be associated with fatigue resistance. 4.Neuropeptides (short chains of amino acids): -Substance P: key excitatory transmitter that indicates pain. -Endorphins: natural pain killers; morphine and heroin mimic endorphins.

22. 5.Gaseous Signals: -NO (nitric oxide): Example – male arousal causes NO to be released from neurons into the erect tissue of penis. NO also dilates blood vessels.

23. Evolution and Diversity of the Nervous System Nerve net  Cephalization  Small brains & nerve cords

24. Vertebrate CNS 1.Brain and spinal cord 2.Spinal cord contains: -White matter: bundles of myelinated axons -Gray matter: unmyelinated axons, nuclei, and dendrites.

25. Vertebrate PNS 1.Everything outside the CNS. 2.Structure components of the PNS: -Cranial nerves -Spinal nerves -Ganglia associated with the cranial and spinal nerves

26. Vertebrate PNS

27. Vertebrate PNS: Autonomic NS Sympathetic: -Adrenal secretion -”Fight or flight” response Parasympathetic: -Returns body to normal

28. Embryonic Development of the Brain

29. The Human Brain

30. 1.The Brainstem “Lower brain” -Consists of pons, medulla oblongata, and midbrain -Functions in homeostasis, coordination of movement, conduction of impulses to higher brain centers. -Medulla oblongata controls: a. Breathing b. Heart and blood vessel activity c. Swallowing d. Vomiting e. Digestion  Relays information to and from higher brain centers -Pons controls: a. Breathing  Relays information to and from higher brain centers

31. The Human Brain -The Midbrain: a. Consists of two parts: 1. Inferior colliculi: part of auditory system 2. Superior colliculi: part of visual system b. Functions in receiving and integrating sensory information.

32. 2. The Reticular System, Arousal, and Sleep -Reticular Formation: group of 90 separate nuclei (groups of neurons) that passes through the core of the brain stem. a. Reticular activating system (RAS): regulates sleep and arousal. -Selects which info gets to the cerebral cortex; more info  more alert The Human Brain

33. Sleep and wakefulness produce different patterns of electrical activity of the brain. The patterns can be recorded in an electroencephalogram (EEG). -Less mental activity produces more synchronous waves (b). -Purpose of sleep?

34. The Human Brain 3.The Cerebellum -Functions in coordination, error-checking, learning and remembering of motor responses, hand-eye coordination. It manages multiple sensory info (visual, auditory, position of joints, muscles, etc) to provide coordinated movements and balance.

35. The Human Brain 4.The Epithalamus, Thalamus and Hypothalamus -Epithalamus: a. Produces cerebrospinal fluid b. Contains the pineal gland (melatonin secretion) -Thalamus: a. Main input center for sensory info going to the cerebrum and main output center for motor info leaving the cerebrum. b. All sensory info is sorted here and sent on to appropriate brain centers.

36. The Human Brain -Hypothalamus: Most important brain region for homeostatic regulation. a. Hunger b. Body temperature c. Thirst d. Fight or flight response e. Pleasure f. Mating behaviors g. Circadian rhythms: internal biological clock -Suprachiasmatic nuclei (SCN) – connected with the visual sensory organs; light is the major external cue for circadian rhythms.

37. The Human Brain 5.The Cerebrum: the most highly evolved structure of the brain -Divided into right and left hemispheres, each of which is responsible for the opposite half of the body. -Two hemispheres joined at the corpus callosum; communication between the two sides. -Outer gray covering called the cerebral cortex -Neocortex – extra layers of cortex unique to mammals -Internal white matter -The cerebrum allows for cognition. Cognition is the process of knowing, awareness, judgement, learning, decision making, and consciousness.

38. -Regions of the cortex are specialized for different functions. -It is divided into four lobes: 1. Frontal lobe 2. Parietal lobe 3. Occipital lobe 4. Temporal lobe

39. -The motor cortex of the frontal lobe controls motor function in response to the sensory neurons found in the somatosensory cortex.

41. Lateralization of Brain Function 1. The Left Hemisphere: - Specializes in language, math, logic operations, and the processing of serial sequences of information, and visual and auditory details. - Specializes in detailed activities required for motor control. 2.The Right Hemisphere: - Specializes in pattern and face recognition, spatial relationships, nonverbal ideation, emotional processing, the parallel processing of information, and music. What if you cut the corpus callosum and the two hemispheres could not communicate? http://faculty.washington.edu/chudler/split.html

42. Language and Speech 1.Broca’s Area: - Usually located in the left hemisphere’s frontal lobe - Responsible for speech production. - Damage to Broca's area causes Broca's aphasia, a condition in which people have trouble producing grammatical language. 2.Wernicke’s Area: - Usually located in the left hemisphere’s temporal lobe - Responsible for the comprehension of speech. -Damage to Wernicke's area causes Wernicke's aphasia, a condition in which people can hear language being spoken, but cannot understand it. 3. Language is processed by multiple areas in the cortex.

43. Broca's Area Wernicke's Area

44. Emotions 1.Limbic System: generates feelings called emotions. -Composed of the hippocampus, olfactory cortex, inner portions of the cortex’s lobes, and parts of the thalamus and hypothalamus. -Mediates basic emotions (fear, anger), involved in emotional bonding, establishes emotional memory. -Amygdala: involved in recognizing the emotional content of facial expression.

45. Learning and Memory 1.Short-term memory is stored in the frontal lobe. 2.Long-term memory is associated with the hippocampus.  The transfer of information from short-term to long-term is enhanced by: -Repetition -Emotional states influenced by the amygdala -Influenced by association with previously stored information.

46. Human Consciousness 1.Consciousness: sensing, acting, and feeling in the present moment but also thinking about the past and the future. 2.Are humans the only ones with a consciousness? 3.Human consciousness was thought to be a topic only considered in philosophy and religion classes but new research shows neural activity that is associated with conscious thought and behavior.

48. Simple Nerve Circuit: Arc Reflex

50. The Human Brain