Neurons

5 Components of a Reflex Arc: 1. Sensory receptor -senses something 2. Sensory neuron -sends signal to the CNS 3. Interneuron- registers signal, it connects the sense to the motor neuron 4. Motor neuron -sends response back 5. Effector- caries out the action

Reflex Arc automatic, quick, involuntary responses to internal or external stimuli. does not immediately involve the brain. allows quicker reaction times to a potentially harmful stimulus

Anatomical Divisions of the Nervous System Central Nervous System (CNS) brain spinal cord Peripheral Nervous System (PNS) cranial nerves spinal nerves

Multipolar Neuron dendrite cell body Myelin sheath Synapse axon

Myelin Sheath & Shwann Cell Nodes of Ranvier Schwann Cells Axon

Types of Neurons multipolar Unipolar (pseudo) bipolar All the rest. Most abundant. Motor Neuron Types of Neurons Unipolar (pseudo) bipolar eye and olfactory Interneuron Dorsal root ganglion cells Sensory Neuron

Reflex Arc - A reflex is an autonomic response.

Nervous System Living cells can only survive and function within a very narrow range of conditions. Homeostasis is the body’s ability to keep normal body functions (the internal environment) in the same stable state or order despite variation in the external environment.

Human survival depends on a system of communication between the internal environment and the external environment. Both the nervous system and the endocrine system (hormones) perform this function. Responses to internal/external environments are made possible by the electrochemical messages relayed from the brain (nervous system) or by chemical messengers (hormones/blood).

The main functions of the nervous system: Receive information and carry it to the central nervous system Interpret impulses and make decisions about the response Sorts impulses and sets priorities for action i.e. walking across the street – eat a bug or get hit by a car Transmit impulses to the motor units (muscles) which carry out appropriate action