Nervous System Flashcards
Contents of Central Nervous System (CNS)
Brain and spinal chord
Contents of the Peripheral Nervous System (PNS)
-Nerves
3 Functions of the Nervous System
- Receives sensory input
- Processes info
- Generates motor output
Nuerons
Cells that transmit nerve impulses between parts of the nervous system.
Neuroglia
Support and nourish neurons
Sensory Neuron
Takes nerve signals from sensory receptors to the CNS
Sensory receptors
Structures that detect change in the internal and external environments.
Effectors
Carry out the responses to internal and external environmental changes.
Structure of a Neuron
A neuron contains a cell body (contains organelles), dendrites (short extensions that receive signals from sensory receptors or other neurons), axons (the portion of a neuron that conducts nerve impulses)
Myelin Sheath
Protective covering of the axons that develops when Schawann cells PNS or oligodendrocytes (CNS) wrap their membranes around an axon many times.
Nodes of Ranvier
The gaps where there is no myelin sheath
Nerve signals
Electrochemical changes that convey information within the nervous system
Generation of an action potential
- Resting Potential: Na+ outside the axon K+ and large anions inside the axon. The separation of changes polarizes the cell and causes the resting potential.
2: Stimulus causes the axon to reach its threshold: the axon potential increases from -70 to -55. The action potential has begun.
3: Depolarization continues as Na+ gates open and Na+ moves inside the axon
4: Action potential ends: repolarization occurs when K+ gates open and K+ moves outside the axon. The sodium-potassium pump returns the ions to their resting postions.
Action potential
The process of conduction
Depolarization
Sodium gates open and Na+ rush into the cell, and the cell´s charge changes from positive to negative
Repolarization
Inside of the axon resumes a negative charge as potassium exits the axon
Axon terminal
Small swellings at the ends of axons
Synapse
Region of close proximity
Synaptic cleft
What separates the sending neuron from the receiving neuron
Neurotransmitters
Transmit signals between nerves
The events at a synapse
- Nerves signals traveling along an axon to reach an axon terminal
- Calcium ions entering the terminal and stimulating synaptic vesicles to merge with the sending membrane
- Neurotransmitter molecules released into the synaptic cleft and differing across the cleft to the receiving membrane
Acetylchonlinsterase (AChe)
Breaks down the neurotransmitter acetylcholine
Integration
The summing up of excitatory and inhibitory signals
Cerebrospinal Fluid
Cushions and protects the CNS
Ventricles of the Brain
Four interconnecting chambers produce and serve as a reservoir for cerebrospinal fluid.
Inter vertebral foramina
What the spinal nerves project through
Cerebrum
The largest portion of the brain in mammals. It communicates and coordinates the activities of other parts of the brain.
Cerebral Hemispheres
Right and left halve of the brain divided by the longitudinal fissure
Corpus Callosum
An extensive bridge of nerve tracts that allows the two hemispheres of the brain to communicate
Cerebral Cortex
Thin, highly convoluted outer layer of grey matter that converts the cerebral hemispheres
Primary Motor Area
Located in the frontal lobe. Spot where voluntary commands to skeletal muscles begin.
Primary Somatosensory Area
The spot where sensory information from the skin and skeletal muscles arrives
Wernickes Area
Allows one to comprehend speech
Bronca´s Area
Allows one to speak and write
Ganglia
Collections of nerve bodies outside the CNS
12 pairs of Cranial Nerves
- Attached to the brain
- Collection of sensory and motor nerves
- Largely concerned with the head neck, and facial regions of the body
Spinal Nerves
- Emerge from either side of the spinal cord
- 31 pairs of spinal nerves
- The roots of a spinal nerve physically separate the axons of sensory neurons from the axons of motor neurons that form a ´Y´
shape.
Divisions of the PNS
The somatic system (serves the skin, skeletal muscles, and tendons) and the autonomic system (regulates the activity of cardiac and smooth muscles, organs, and glands)
Sympathetic division
- Arrises from the middle portion of the spinal cord
- Sympathetic division is especially important during emergency situations when you might be required to take fight or flight
Parasympathetic Divison
- Includes a few cranial nerves
- Also called house keeper division
- Promotes all the internal responses we associate with a relaxed state