Describe how organisms respond to changes in their environment
Describe a nerve impulse
Design and experiment to determine the instinctive behavior of a planarian
The Regulatory Process
Explain the functions of a nervous system.
Describe the structure and the function of a neuron.
Name the different types of nerves and describe their functions.
Functions of Regulation
Environment always changing
Organism changes, adjustments
Inside and outside the body
Irritability ability of a cell to respond to its environment
Nervous and endocrine systems
Controls regulation and coordination
Mechanisms of Nervous Regulation
Network of cells nerve cells
Carry messages impulses
Receptors sense organs
Sensitive to changes
Physical force, chemicals
Inside or outside of body
Structure respond to commands of nervous system
Anything that causes a receptor to start impulses in a nerve pathway.
Cause electrical and chemical changes in receptors.
3 events in nervous regulation:
1. Stimulus activates a receptor
2. Impulses are started in associated pathways.
3. Effectors responds to the impulse.
Specialized group of nerve cells that controls and coordinates the activities of the nervous system.
More complex the organism, the more complex are the function and structure of the brain.
Structure of Neurons
A way to remember the relationship between: dendrites, cell body, and axon.
Another look at a Neuron
Does it work ?
Many branches at ends
Almost touch each other
Place between the terminal branch of a neuron and the membrane of another cell
One of more synapses
As many as 1000 other neurons
Synaptic junction between neurons
Stored in synaptic vesicles
Trigger an action potential
Types of Nerves and Neurons
Interneurons or associated neurons
Section Review Quiz
1. What are the three types of structures found in a true nervous system?
2. What happens when a receptor is stimulated?
3. List the three parts of a nerve cell.
4. What is a synapse?
5. What would happen if the motor neurons in one of your legs stopped functioning?
The Nerve Impulse
Describe the electrical state of a resting neuron and the function of the sodium-potassium pump.
List the changes that occur as an impulse travels along an axon.
Explain how the nervous system distinguishes between stimuli of different types and strengths.
Identify the structures of a synapse and describe the transmission of an impulse across a synapse and at a neuromuscular junction.
The Resting Neuron
No impulse transmission occurs
Outside has a net positive charge
Inside has a net negative charge
Cell membrane electrically polarized
Difference in charge on inside and outside
Caused by concentration of ions
Na + ion and K + ion
Sodium potassium pump
Sodium ions out
Potassium ions in
The Nerve Impulse
Membrane changes in the area of the impulse.
Permeability of the membrane to sodium ions increase.
Higher amount of sodium ions causes them to diffuse rapidly inside of membrane.
Thus reverses polarization
becomes positive charge.
Outside becomes negative charge
Continues throughout nerve cell
Like a relay race
Returns to normal in milliseconds
Brief period during which nerve cell membrane cannot be stimulated to carry impulses.
Rate of Impulse Conduction
1. Size of nerve fiber
2. Whether or not it has a myelin covering.
Small fibers without myelin
2 m / s
Large myelinated fibers
More than 100 m /s
Impulse jumps from one node of Ranvier
Axon is bare
Faster and uses less energy
Nerve Cell Thresholds
Stimulus must have a certain minimum strength
Threshold - Cells minimum level of sensitivity
Below threshold stimulus cannot start impulses
Above will start impulse
All or none basis
Distinguishing Strength and Type of Stimulus
Measurement by two effects:
1. Stronger impulses causes more impulses to be transmitted each second.
2. Different neurons have different thresholds.
Recognition of type
Transmission at the Synapse
Serotonin, epinephrine, an amino acid called glycine
Impulses pass from motor neurons to muscles at these special points.
Motor end plates
Drugs and the Synapse
Poisons and drugs
Botulin toxin ( bacteria poison )
Interfere with function of acetylcholine at neuromuscular junctions
Cause muscle paralysis
Effect mind and emotions
Alter activity of body systems
Stimulants speed up body activity
Amphetamines - bind to certain receptors
Uppers short lived feelings of well being and excitement followed by depression
Caffeine found in tea, coffee, cola increases synaptic transmission
Sleeplessness and nervousness
Depressants slow down body activities
Downers produce a depressant effect, blocks formation of norepinephrine
Hallucinatory drugs interfere with the effect of serotonin, an inhibitory transmitter.
Section Review Quiz
1. What name is given to a neuron that is not sending a nerve impulse?
2. What is the sodium-potassium pump?
3. What crosses the synapse when a nerve impulse is traveling over a pathway of nerve cells?
4. What are neuromuscular junctions?
Adaptations for Nervous Regulation
Describe the response of protists to stimuli.
Compare and contrast the nervous systems of the hydra, earthworm, and grasshopper.
Regulation in Protists
Do not have true nervous system
Able to respond to stimuli
No specialized receptors
Can tell difference between food and nonfood
Filaments are like
Paramecium cilia and beating control
Respond to stimuli food, strong acids away from solid matter
Some have organelles
Regulation in Hydra
Form of a nerve net
Irregular network between the two layers of the body wall
Connect receptor cells to muscles and gland cells
Impulses spread slowly through nerve net
Response show coordination
Regulation in the Earthworm
More complex nervous system
Central nervous system
Really a pair of ganglia joined together
Ventral nerve cords
Enlarge into ganglia in each segment
Ganglion group of cell bodies and interneurons that switch, relay, coordinate nerve impulses
Peripheral nervous system
Nerves branching from CNS to all parts of body
Contain sensory and motor neurons
Receptors sensitive to light, vibrations, chemicals and heat
Travel in one direction
Regulation in the Grasshopper
Similar to earthworms
Brain in head region
Pair of solid ventral nerve cords
Run length of body
Nerve branches to all parts of body
Sense organs more highly developed than earthworm.
Antennae or " feelers "
Taste organs that respond to a variety of stimuli
Sensitive to sound
Section Review Quiz
1. Name the types of stimuli to which some protists respond?
2. What type of nervous system does the hydra have?
3. Name the two parts of the nervous system of the earthworm.
4. What specialized sense organs does the grasshopper possess?
5. Based on their capacity for nervous regulation, place each of the following organisms in order from most complex to least complex: ameba, earthworm, grasshopper, human, hydra, and paramecium
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