Nervous System

1. Nervous System AP Biology Ch. 48 Ms. Haut

2. Function of Nervous System • Sensory Input • Conduction of signals from sensory receptors • Integration • Carried out by Central Nervous System (CNS) • Brain and spinal cord • Motor Output • Carried out by Peripheral Nervous System (PNS) • Conduction of signals to muscle or gland cells • Carry out body’s responses to stimuli

3. Animal Nerve Cells • Nerves: rope-like bundles of extensions of neurons, tightly wrapped in connective tissue • Neurons: functional unit of the nervous system

4. Functional Organization of Neurons • Sensory Neurons: relay information (stimuli) from the external and internal environments to CNS • Interneurons: integrate sensory input and motor output (carry stimuli in the brain and spinal cord) • Motor Neurons: convey impulses from CNS to effector cells in muscles or glands • Glial cells: support, protect, and nourish neurons

5. Structural Diversity of Neurons

6. Overview of Vertebrate Nervous System

7. Neuron Circuitry • Simplest neural circuit involves synapses between 2 neurons, a sensory neuron and a motor neuron • Result is often an automatic response called a reflex

8. The Knee-jerk Reflex http://bio.rutgers.edu/~gb102/lab_5/103ar.html

9. Neural Signals • Nerve impulse is an electrical signal that depends on the flow of ions across the plasma membrane of a neuron

10. Membrane Resting Potential Cell is said to be polarized

11. Action Potential • A nerve impulse is generated when the difference in electrical charge disappears • Occurs when a stimulus contacts the tip of a dendrite and increases the permeability of the cell membrane to Na+ ions • Cell is said to be depolarized

12. Graded Potentials “All-or-none event”

13. Regulation of Action Potential

14. Propagation of the Action Potential • After the wave of depolarization has passed, the neuron reestablishes the difference in charges by pumping K+ out of the cytoplasm

15. Saltatory Conduction

16. Synapses • Nerve impulses pass down the dendrite, through the cell body, and down the axon. • At the end of the axon, the signal reaches a fluid-filled space (synapse) separating the end of the axon from the dendrite of the next neuron. • Neuromuscular junction: synapse located at the junction of a neuron and muscle fiber

17. Chemical Synapse

18. MAJOR NEUROTRANSMITTERS AND THEIR EFFECTS Acetylcholine (ACh) Generally excitatory Affects arousal, attention, memory, motivation, movement. Too much: spasms, tremors. Too little: paralysis, torpor. Dopamine Inhibitory Inhibits wide range of behavior and emotions, including pleasure. Implicated in schizophrenia and Parkinson's disease. Serotonin Inhibitory Inhibits virtually all activities. Important for sleep onset, mood, eating behavior. Norepinephrine Generally excitatory Affects arousal, wakefulness, learning, memory, mood. Endorphins Inhibitory Inhibit transmission of pain messages.

19. CNS CNS Organizations of Invertebrates Without CNS (PNS)

20. Vertebrate Nervous System

21. Autonomic Nervous System • Works on an involuntary basis • 2 subdivisions

22. Roles of Parasympathetic and Sympathetic Divisions of the Autonomic Nervous System

23. Structure of Brain

24. Brainstem • Medulla oblongata • Contains centers that control visceral (autonomic, homeostatic) functions • Breathing, heart and blood vessel activity, swallowing, vomiting, and digestion • Pons • Have nuclei in the medulla that regulate breathing centers • Midbrain • Centers for receipt and integration of sensory information • Coordinates large-scale body movements such as walking

25. Cerebellum • Primary function is coordination of movement • Receives information about position from joints and length of muscles, as well as auditory and visual systems • Plays role in learning and remembering motor responses (hand-eye coordination)

26. Thalamus and Hypothalamus • Thalamus • Main input center for sensory information going to cerebrum • Receives input from cerebrum to regulate emotion and arousal • Hypothalamus • Source of posterior pituitary hormones and releasing hormones that act on anterior pituitary • Regulates body temp, thirst, hunger, other basic survival mechanisms • Plays role in sexual response and mating behaviors, fight-or-flight response, and pleasure

27. Structure and Function of Cerebrum

29. Sleep and Arousal • Controlled by several centers in the cerebrum and brainstem • Reticular formation: neurons that pass through the brainstem • Reticular activating system--regulates sleep and arousal • Increased input to cortex, increases alertness • Medulla and pons • Nuclei stimulated induces sleep • Serotonin may activate sleep centers

30. Lateralization, Language, and Speech • Association areas of cerebral cortex are lateralized (specialized functions) • Left hemisphere • Speech, language, calculation, and rapid serial processing of details • Right hemisphere • Overall context, spatial perception, and creative abilities

31. Emotions • Limbic system-functional group of nuclei and interconnecting axon tracts in the CNS • Includes parts of the thalamus and hypothalamus, and portions of the cerebral cortex • Linked to areas of cerebral cortex involved with complex learning, reasoning, and personality • Amygdala-prominent component of limbic system • Major organizer of emotional information • Plays role in memory association