THE NERVOUS SYSTEM
Introduction
B. The nervous system is divided into two parts:
1. Central Nervous System (CNS) - brain and spinal cord
2. Peripheral Nervous System (PNS) - peripheral nerves through the body
- includes ______pairs of spinal nerves
- includes ______pairs of cranial nerves
Three Basic Functions
1. Sensory Function -
2. Integrative Function -
3. Motor Function –
- Somatic Nervous System-
- Autonomic Nervous System-
Neurons: Nerve cells. - cell body with many extensions or processes (nerve "fibers") which conduct impulses
1. Dendrites -
2. Axons -
Neuroglial Cells (neuroglia)
- supportive tissue of the nervous system (more numerous than neurons). Five types
- Microglial Cells
- Oligodendrocytes
- Astrocytes
- Schwann cells
*Myelin Sheaths
Neurons
A. Neurons = masses of nerve cells that transmit information to other nerves, tissues or cells (nerve impulses)
1. ______- contains the nucleus and two extensions
2. ______- shorter, more numerous, receive information
3. ______- single, long fiber which conducts impulses away from the cell
Myelin
Nodes of Ranvier
Myelinated (______) vsUnmyelinated (______)
Classification of Neurons
1. ______(sensory neurons, motor neurons, interneurons)
2. ______(multipolar, bipolar, unipolar)
Interesting Info:
Cell Membrane Potential
Resting Potential / Threshold Potential / Action Potential
1. Neuron membrane maintains ______
2. Threshold stimulus is received
3. ______channels open
4. Sodium ions diffuse inward, depolarizing the membrane
5. ______channels open
6. Potassium ions diffuse outward, repolarizing the membrane
7. The resulting action potential causes a local ______current that stimulates adjacent portions of the membrane.
8. Wave of a______travel the length of the axon as a nerve impulse
Nerve Impulse
*Propagation of action potentials along a nerve axon
Impulse Conduction – speed of an impulse proportionate to ______of axon (greater diameter = faster impulse)
Myelinated axons conduct ______than unmyelinated axons
The Synapse
Synapse =
Nerve pathway – nerve impulse travels from neuron to neuron
Dendrite > cell body > along axon > synapse (gap)
To complete the signal, a ______is released at the gap to signal the next neuron
______– increase membrane permeability, increases chance for threshold to be achieved
Inhibitory – decrease membrane permeability, decrease chance for threshold to be achieved
Types of Neurotransmitters
Acetylcholine – stimulates ______
Monoamines – Norepinephrine & Dopamine (sense of feeling good,
low levels = depression)
Serotonin = ______
Endorphins = ______
Synapses are highly susceptible to drugs and fatigue
Impulse Processing
Neuronal pool – groups of neurons that make hundreds of synaptic connections and work together to perform a common function
Types of Nerves
Sensory Nerves – conduct impulses into ______
Motor Nerves – carry impulses to ______
Mixed Nerves - contain both sensory and motor nerve
Nerve Pathways
Reflex arc – simple pathway, includes only a few neurons (______)
Reflex Behavior – automatic, subconscious responses to stimuli
Knee-jerk reflex =
Withdrawal reflex =