Nervous System 1 Flashcards
Nervous System is made up of…
- Brain
- Brainstem
- Spinal Cord
- Nerves
- Ganglia
- Parts of the receptor organs
That receives & interprets stimuli from:
-the environment &/or the body
Transmits impulses to the environment/body
-muscles, glands, organs, and other nerves
Organization of the Nervous System
- Central Nervous System
- Brain
- Brainstem
- Spinal Cord
- Peripheral Nervous System
- Peripheral Nerves
- Somatic (body)
* cranial nerves
* spinal nerves
- Somatic (body)
- Autonomic
Every component of the CNS & PNS is composed of primarily one type of cell:
The Neuron
Nerve
Group of multiple neurons
Neuron
- Single nerve cell that acts as a conduct
- To conduct a signal or impulse in ONLY one direction
Composed of:
- cell body
- dendrites
- axon
Dendrites
Receive stimuli or impulse
Axons
Conduct impulses
Structure of Nervous System
Classification
- Physiological (Functional)
- Anatomical (Structural)
Classification
Physiological
- Afferent Neuron
- Conducts an impulse toward the CNS
- Also called Sensory neurons
- Conducts an impulse toward the CNS
- Efferent Neuron
- Conducts an impulse away from CNS
- Also called Motor neurons
- Conducts an impulse away from CNS
- Interneurons
- Conducts impulses between other neurons
- Found only in the brain & spinal cord
- Conducts impulses between other neurons
Classification
Anatomical
- Bipolar
- Two extensions from the cell body
- One from each end (1) Axon (2) Dendrites
- Found: eyes, nose, ears (Afferent, Sensory)
-
Unipolar
- One extension from the cell body
- Extension divides into 2 branches
- One of the branches is associated with dendrites
- Found: Sensory Neurons (General sense) Temp, touch, pain
- Multipolar
- Many extensions from the cell body
- Only one is an axon
- Found: everywhere
Nervous System
Function
- Gather information
- Transport information
- Interpret information
The information must be in a form the body can transport & then read
- Like TV/Satellite signals
The form of the signal the Nervous System uses is called an Action Potential
Action Potential
General
Also called a nerve impulses or nerve signal
It is described as:
wave of electrochemical activity that allows a neuron to carry a signal over a distance
- Generated by;
- the diffusion of specific ions
- in & out of neurons
- the diffusion of specific ions
Background Information
Function
- Most subtances in nature are neutral
- They are not positive or negative
- If something is positive or negative
- They are said to have a “charge”
- We refer to something with a charge as having Polarity
- Examples: The ends of a battery
- One end is positive, the other is negative
- One end has a positive polarity
- The other end has a negative polarity
- One end is positive, the other is negative
Action Potential
Polarity
- The inside of all cells in the body are Negative
- when compared to the outside of the cell
- So the inside of our cells have a Negative polarity
- the outside then has a positive polarity
- Internal Negative Polarity
- Maintained by protein pumps in the cell membrane that uses ATP i.e. Na/K+ ATPase Pumps (Active Transport)
- When a stimulus comes in contact with a Neuron’s dendrites/cell body, allows the diffusion of these specific ions to occur thru protein channels
- This changes the “charge” inside the cell or polarity
Action Potential
Stimulus
When a stimulus comes in contact with a neuron’s dendrites/cell body
- This causes protein channels (gates) to open
- Allows the diffusion of these specific ions to occur
- From high concentration to low concentration
- This changes the “charge” (polarity) of the inside cell
Stimulus
Can be anything that we respond to from the environment or from inside ourselves
Ex. Temp, sound, pain, cramps, etc
Stimulus can be from…
- Can be from external environment
- Hot/cold, light, movement, etc
- Can be from the internal environment (body)
- Brain generating an impulse
- Stretching of an organ, muscle, etc
Whatever the stimulus;
Causes certain ion channels (gates) to open
The ions diffuse based on their concentration
- High to low
This diffusion changes the ion concentrations
Results;
- The neuron’s internal charge (polarity) changes
- A change in charge (polarity) = Electrochemical Activity (Action Potential, Nerve Impulse)
Action Potential
Ion Movement
Na+/K+
Moves the K+ ions back inside the neuron and the Na+ ions out of the neuron
Na+/K+ Pump uses Active Transport
That means it uses ATP
So much ATP that;
- 20% of your body’s Total ATP is used by just these pumps
- A single axon can have up to 1 Million Na+/K+ pumps
Action Potential’s proper definition
- Wave of electrochemical activity that allows a neuron to carry a signal over a distance
- The axon of the neuron
- Allows this electrochemical activity to move like a wave
- Down the Axon to the next structure
- Like throwing a rock in a pond
- Where the waves move out from where the rock hit
Structure Effecting Function
- Action Potentials occur ONLY in the AXONS of Neurons
- Axons
- Extension of the cell body
- Only one (1) per neuron
- Surrounded by
- Multiple layers of phospholipid membrane
- Cell membrane of another cell
- Called Myelin Sheath
- Produced by specialized Non-Neuron cells
- Multiple layers of phospholipid membrane
Structure Effecting Function 2
Action Potentials
- moves to the next area of the axon that is un-myelinated (area of no myelin sheath)
- called a Node of Ranvier
- The area of the axon where the Action Potentional moved FROM- now Refractory
- Means it cannot generate another Action Potential for a specific time
- This means the AP can only move in one direction
Function/Structure of AP
To Connect
- All the parts of the body to CNS
In the CNS
- Processing the incoming data
To Send
- Signals back to the rest of the body to direct their activities
During each step of these functions
- There will be connections b/w neurons
- Usually: multiple neurons
Ex: To feel something cold
3 neurons are used b/w/ your finger & brain
Neuronal Arrangement
- 1st Neuron is before the synapse
- called the Pre-synaptic Neuron
- 2nd Neuron is after the synapse
- called the Post-synaptic Neuron
- Post-synaptic neuron will then connect with one of a number of structures
- Ex:
- Muscle
- Organs
- Gland
- Other nerves
- Ex:
Neuronal Arrangment
General
In general, each time there is a neuronal connection, there is a synapse, which means that a neurotransmitter is being used
A post-synaptic neuron
- may have multiple pre-synaptic neurons connected to it
- Each causing a different response
- Some may cause an excitatory affect-positive
- Some may cause an inhibitory affect-negative
Signal Transmission (1)
An impulse reaches the end of the pre-synaptic neuron (neuron #1)
- Neurotransmitter is released into the synapse
- Release is from vesicles (packages)
- formed & stored at the end of the Pre-Synaptic neuron
- Rate of the impulses that reach the end of the axon
- Strength of the impulse that reaches the end of the axon
- Determines the amount of neurotransmitters released
- Stronger/Faster impulses cause more vesicles to be emptied
- Determines the amount of neurotransmitters released
Signal Transmission (2)
The Greater the concentration of neurotransmittter released into the synpase means:
- The faster it DIFFUSES across the synapse (speed)
- The Greater the responses of the Post-Synaptic neuron (intensity)
- This means, whatever the Post-synaptic neuron is connected to, will respond more
- Faster, stronger muscle contractions
- More secretions from a gland (adrenal)
- Increased intestinal movement
Neurotransmitters
Nervous system produces 30 different types
Certain ones are used more than others
Neurotransmitters
types are based on substance they are synthesis from
- Products of metabolism
- Modified amino acids
- Unmodified amino acids
- Peptides
Neurotransmitters
A. Products of Metabolism
Acetylcholine
- Actyl group from metabolism of glucose in glycolysis
- Choline is part of the vitamin B complex
Neurotransmitters
B. Modified amino acids
Modification to a single amino acid: Monoamines
- L-Tryptophan
- Serotonin
- CNS: Regulates anxiety, emotions, appetite
- Serotonin
- Tyrosine
- Catecholamines
- Epinephrine/Norepinephrine
- CNS-Conscience arousal
- PSN- Muscle activity
- Epinephrine/Norepinephrine
- Dopamine
- CNS- Behavior & reward systems
- PNS- Skeletal muscle coordination
- Catecholamines
Neurotransmitters
Unmodified amino acids
Glycine
- CNS- Spinal cord
- Aids in skeletal muscle control, sequencing
GABA (Gamma Amino Butyric Acid)
- CNS- Brain
- Coordination of muscle sequence/order
Neurotransmitters
Peptides
Short chain of amino acids
- Multiple examples
- Usually involved in sensory perception
