The Nervous System

Regulation The control and coordination of life activities All organisms use chemicals to regulate life activities Multicellular animals have NERVE CONTROL Allow for organisms to maintain HOMEOSTASIS

Stimuli are detected by RECEPTORS Stimulus: Any change in the external or internal environment that initiates a RESPONSE Response: A change in BEHAVIOR Stimuli are detected by RECEPTORS Sensitive to a particular type of stimulus Ex. EyesLight, EarsSound Effectors: Organs that produce a response to a stimulus Ex. Muscles and Glands

Neuron Specialized cells which are responsible for transmitting IMPULSES from one part of the body to another Impulse: Electrical and chemical changes that travel through neurons Causes the release of NEUROTRANSMITTERS from terminal branches **Neuron-Nerve-Ganglia-Brain Made up of 4 main parts

Dendrites (Receptors) Cell branches that receive impulses from other neurons or from receptors

Cyton The cell body Contains a nucleus

Axon The branch of the cell that transmits impulses away from the cyton

*Node of * Schwann Cell * Myelin Myelin Sheath The fatty insulation covering produced by the Schwann cells. Nodes of Ranvier – Area of no myelin *Node of Ranvier * Schwann Cell * Myelin

Terminal Branches Responsible for: transmitting impulses to the dendrites of other neurons Transmitting impulses to effectors

Synapses Junction between adjacent nerve cells Some nerve cells have junctions with muscles or glands Chemicals released stimulate contraction of the muscle, or secretion by the gland

Neurotransmitters Chemicals that are secreted by the terminal branch into the synapse between neurons Carry impulses from one cell to the next Ex. Acetylcholine and Noradrenaline

Amoeba – No true nervous system Paramecium System of FIBRILS that transmit impulses to cilia Regulates LOCOMOTION and INGESTION Some species of Protozoans have EYESPOTS Receive stimuli and generate impulses to produce a response Hydra Contain specialized cells similar to neurons, but do not have a central nervous system Cells connect to form a NERVE NET Impulses travel in any direction

Earthworm Has neurons organized into distinct structures and organs which form a TRUE NERVOUS SYSTEM Brain: Mass of ganglia located on the dorsal side of the worm, near the head Ventral Nerve Cord Main nerve Connected to the brain and runs along the length of the animal on the ventral side (Belly) Nerve Branches Series of smaller nerves that branch to all parts of organism Impulses are generated by receptors and travel through the nerves to reach muscles and glands

Grasshopper Similar nervous system to earthworm Has SENSORY ORGANS Eyes Tympanum- Detects sound Antennae- Sense and Touch

A Lateral view B Dorsal view 1 Antenna 2 Brain (cerebral ganglion) 3 Compound eye 4 Tympanum 5 Ganglion 6 Beginning of the Dorsal Nerve Cord 7 Segmental nerves 9 Ventral nerve cord

Human Nervous System Concept Map Central Nervous System Peripheral N.S. Brain Spinal Cord Communication between the brain and the P.N.S. Cerebrum Controls all conscious thought Cerebellum Balance and coordination Medulla Involuntary control Heart, Respiration, Organs

Cerebrum Medulla

Human Nervous System Concept Map (Central Nervous System) Peripheral N.S. Involuntary (Autonomic) Visceral (Organs) 2 Parts Voluntary (Somatic) Control of all skeletal muscles Fight or Flight Parasympathetic Control of the organs Designed to decrease function (Acetylcholine) Calming effect Sympathetic Control of the organs Designed to increase function (Noradrenaline, Norepinephrine)

Human Behavior Involuntary Behavior – occurs automatically without conscious control Inborn – present at birth Acquired behavior – develops after birth as the result of experience Walking, writing, speech a. Simple reflex arc b. conditioned behavior 1. automatic behavior that is acquired (habits) 2. once pathways are established, the actions are very rapid and automatic 2. Voluntary Behavior – conscious behavior that uses the Cerebrum of the brain Makes use of memory

The Reflex Arc is a real “No Brainer” Advantages 1. speed and protection from harm and injury

Malfunctions of the Nervous System Meningitis a. inflammation of the meninges (coverings of the brain and spinal cord) b. can be bacterial of viral c. first signs are severe neck stiffness and headaches 2. Cerebral Palsy a. damage to the motor centers of the brain b. you see poor coordination (scissors gait) 3. Stroke a. damage of the nerve cells of a region of the brain b. due to hemorhage or blood clot