Nervous System AP Biology Ch. 48 Ms. Haut

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

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

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

Structural Diversity of Neurons

Overview of Vertebrate Nervous System

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

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

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

Membrane Resting Potential Cell is said to be polarized

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

Graded Potentials “All-or-none event”

Regulation of Action Potential

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

Saltatory Conduction

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

Chemical Synapse

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 Inhibits virtually all activities. Important for sleep onset, mood, eating behavior. Norepinephrine Affects arousal, wakefulness, learning, memory, mood. Endorphins Inhibit transmission of pain messages.

Organizations of Invertebrates Without CNS CNS (PNS) CNS

Vertebrate Nervous System

Autonomic Nervous System Works on an involuntary basis 2 subdivisions Parasympathetic Sympathetic Return body to normal after an emergency Prepare body for emergency Heart rate slows, pupils constrict, blood vessels dilate Increase heart rate, constricted blood vessels, pupils dilate

Roles of Parasympathetic and Sympathetic Divisions of the Autonomic Nervous System

Structure of Brain

Brainstem Medulla oblongata Pons Midbrain 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

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)

Thalamus and Hypothalamus 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

Structure and Function of Cerebrum

Primary Somatosensory cortex Primary Motor cortex

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

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

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