OLA #4

Three classes of signal sending

1. Sensory neurons- responding to certain stimuli (e.g. light or pressure) -PSN, sense organs 2. Interneurons- transmit signals between CNS and PNS components (receive input from sensory neurons) -CNS, spinal cord and brain 3. Motor neurons- PNS components that receive CNS output information (carry signals from brain/spine to muscles, organs, etc.) -PNS, muscle tissues *Only about 20% of the cells in the nervous system are signal conducting neuron cells, the rest are support cells

Neurons

Cells that generate and conduct signals as a means of communication between tissues of the body -Specialized cells that utilize chemical and electrical signals to 'communicate info'

Signal transduction

For a signal to be transmitted through a neuron, a reversal of the resting potential electro chemical gradient needs to occur

Sending a signal through a neuron

The function of a neuron is to receive signals and then either transmit, or fail to transmit, to other cells -To send a signal, neurons establish an electrical charge difference across their membrane *Negative charge inside the cell/ Positive charge outside of the cell

Myelin

a mixture of proteins and lipids secreted by neuroglial cells on to the axons of neurons *Myelin benefits for neurons: -Saves energy -Speeds up signal impulses -Aids in regeneration of damaged axons

Schwann cells

are a class of neuroglial cells that enclose and protect the axons of many neurons cells in the PNS -They insulate the neuron axons with a fatty material known as myelin

Peripheral Nervous System (PNS)

consists of the input (sense organs, receptor nerves) and output (muscles, effector neurons) subdivisions that transfer signals to and from the CNS -Consists of all nerve tissue outside the brain and spinal cord -PNS is divided into 2 divisions: motor & sensory

electrochemical gradient

is an imbalance in electrical charge that results from an imbalance in chemical concentrations -The resting potential of a neuron is the result of this electrochemical gradient -A membrane with a constant charge difference on either side is considered polarized

Nervous system

is the network of cells that transmit and interpret signals to coordinate functions in many multicellular organisms -Receives info from many different sensors simultaneously -Integrates informations (i.e. sorts and interprets info.) -Can initiate specific responses (i.e. execute specific tasks, behavior) Two principle divisions: 1. Central Nervous System (CNS) 2. Peripheral Nervous System (PNS)

axon

long cell membrane tube, conducts electrical impulses

Cell body

nucleus and all organelles

Neuroglial cells

provide physical support and protect neurons but are themselves not neurons -Do not transmit signals *Functions: -Surround neurons and hold them in place -Supply nutrients and oxygen to neurons -Separate one neuron from another -Destroy pathogens and remove dead neuron

Dendrites

receives impulses from receptors or other neurons

Central Nervous System (CNS)

receives, processes, stores, and transfers information -In mammals, it consists of the brain and spinal cord

Resting potential

the difference, in charge, across the membrane of a neuron