(c) Fundamentals of the Nervous System & Nervous Tissue (Q2,P6) Flashcards
Nervous System Functions
Master control and communication system
1) Gathers information – sensory input
2) Processes and interprets sensory input
3) Dictates a response - motor output
Basic Divisions of the Nervous System
Central Nervous System
Peripheral Nervous System
Central Nervous System (CNS)
Integrating and command center
2 Divisions: Brain, Spinal Cord
Peripheral Nervous System (PNS)
Consists of nerves extending from brain and spinal cord
Cranial nerves – 12 pairs
Spinal nerves – 31 pairs
- Peripheral nerves link all regions of the body to the CNS; responsible for getting info to cns and putting out info to the body
Sensory (afferent) signals
- signals that come from outside stimuli and tell your brain what they are sensing, such as temperature
- Picked up by sensor receptors
- signals directed TOWARD the CNS
Motor (efferent) signals
innervate muscles and glands
Signals travel AWAY from the CNS
Main Cell Types of Nervous Tissue
1) Supporting cells (neuroglial cells) – nonexcitable; Surround and wrap neurons
2) Neurons – transmit electrical signals (excitable); Body has billions of neurons
Special Characteristics of the Neuron
1) Longevity – can live and function for a lifetime; usually can’t be restored
2) Do not divide – fetal neurons lose their ability to undergo mitosis; neural stem cells are an exception
3) High metabolic rate – require abundant oxygen and glucose
Three Main Parts of a Neuron
1) Cell Body
2) Dendrites
3) Axons
Cell Body of a Neuron
Contains usual organelles plus other structures
Dendrites
- Extensively branching from the cell body
- Function as receptive sites (carry electric signals to the cell body)
Axons
- Neuron has only one
- portion of a nerve cell (neuron) that carries nerve impulses away from the cell body.
Ganglia
Clusters of cell bodies
Synapses
- Site at which neurons communicate
- Signals pass across synapse in one direction
Nerves
- cordlike organs in the PNS
- Consists of numerous axons wrapped in connective tissue
Myelin Sheaths
- Axons is surrounded by myelin sheaths
- Surround thicker axons
- Form an insulating layer; Prevent leakage of electrical current to ensure it goes in the proper direction
- Increase the speed of impulse conduction
Types of Nerve Coverings
1) Endoneurium: layer of delicate connective tissue surrounding the axon
2) Nerve Fascicles: groups of axons bound into bundles
3) Perineurium: connective tissue wrapping surrounding a nerve fascicle
4) Epineurium: whole nerve is surrounded by tough fibrous sheath
Directional Terms Unique to the CNS
1) Rostral: toward the nose
2) Caudal: toward the tail
4 Regions of the Brain
- Cerebral hemispheres
- 3 parts of Diencephalon
- 3 parts of Brain stem
- Cerebellum
3 parts of Diencephalon
thalamus, hypothalamus, epithalamus
3 parts of the Brain stem
midbrain, pons, and medulla oblongata
What are the Ventricles of the Brain?
Expansions of the brain’s central cavity
Filled with cerebrospinal fluid produced by vessels called the CHOROID PLEXUSES
Ventricles are Continuous with each other
Ventricles are Continuous with the central canal of the spinal cord
4 Ventricles of the Brain
1)Lateral ventricles
2) Third ventricle
3) Cerebral aqueduct
4) Fourth ventricle
Lateral ventricles
located in cerebral hemispheres, anterior in the brain
Third ventricle
- lies in diencephalon
- Connected with lateral ventricles by interventricular foramen – also called the “Foramen of Monro”
Cerebral aqueduct/“Aqueduct of Sylvius”
connects 3rd and 4th ventricles