Mia Alvarez, Period:3 Nervous system
Major functions of the nervous system
Classification of neurons
Connective Tissue Coverings
Major parts and functions of the brain
Action potential & the Nerve Impulse
Cranial nerves
Spinal nerves
Neurotransmitters
Compare & contrast the autonomic nervous system
thinking, movement, internal
processes of physiology.
Major aspects of nervous system: sensory input, integration and
processing (decision-making), and motor output (response).
Provided by sensory receptors, which detect internal or external
changes
A neuron contains a cell body, tubular cytoplasm-filled dendrites, and a
tubular, cytoplasm-filled axon
Dendrites conduct impulses toward the cell body; they are short and
branching, and they provide the receptive surface for communication with other neurons
The axon conducts impulses away from the cell body; it arises from a
thickening extending from the cell body, called the axon hillock
There is only 1 axon in each neuron
Multipolar neurons- have many dendrites and one axon arising from their cell bodies; most neurons with cell bodies in CNS (interneurons and motor neurons) are multipolar.
Bipolar neurons have 2 processes extending from the cell body, a dendrite and an axon; found in some of the special senses, such as the eyes, nose, and ears
Unipolar neurons have only 1 process extending from the cell body; outside the cell body, it soon splits into 2 parts that function as 1 axon; the peripheral process has dendrites near a peripheral body part, and the central process runs into the CNS; the cell bodies are found in ganglia outside the CNS; these are sensory neurons.
Neurotransmitters are the chemical messengers in a synapse, that convey an electrical impulse from a neuron to another cell.
Autonomic nervous system: controls involuntary effectors (smooth and
cardiac muscles and glands).
Action potential either occurs or does not.
It occurs when the charge reaches -55 mV
Action potentials of a neuron are all of the same strength
When action potential is reached, cell responds by returning to resting
potential (-70 mV) by process of repolarization
At end of repolarization, a slight overshoot called hyperpolarization
occurs, in which potential dips below -70 mV
Finally, the Na+/K+ pump moves Na+ ions back out of cell, and K+ back into cell
Upon reaching threshold potential, voltage-gated Na+ channels open, changing charge to about +30 mV; this is called an action potential
There are more than 100 neurotransmitters
Neurotransmitters include acetylcholine, amino acids,
neuropeptides
Action of neurotransmitter depends on type of receptors in a
specific synapse
Some neurons produce one type of neurotransmitter, while others produce two or three
Epineurium: outer covering of a nerve
Perineurium: covering around fascicles (bundles) of nerve fibers
Endoneurium: covering around individual nerve fibers (axons)
reflex arc
A sensory receptor that detects changes
A sensory neuron, that carries the information from a receptor toward the CNS
An interneuron in the CNS (reflex center)
An effector (muscle or gland that carries out the reflex) that responds to the initial change.
Reflexes: automatic responses to changes (stimuli) inside or outside of the body, that help maintain homeostasis
The patellar (knee-jerk) reflex is an example of a simple reflex; it has only 2 neurons, sensory & motor, and lacks an interneuron
The brain and spinal cord are surrounded by 3 membranes called meninges that lie between the skull bones & vertebrae and the soft CNS tissues
The meninges consist of the dura mater, arachnoid mater, and pia mater
Begins at the base of the brain.
Cervical enlargement- A thickened area near top of spinal cord, Provides nerves to upper limbs
Lumbar enlargement- A thickened region near the bottom of the spinal cord. Gives rise to nerves that serve the lower limbs.
Cauda equina (horse’s tail)- Structure formed where spinal cord tapers to a point inferiorly. Consists of spinal nerves in the lumbar & sacral areas.
Twelve pairs of cranial nerves arise from the underside of the brain
Most are mixed nerves, containing sensory & motor nerve fibers,
but some are only sensory, and others are primarily motor
The first pair arises from the cerebrum, and the second pair from the thalamus, but most arise from the brainstem
The 12 pairs are designated by number and name; the numbers are in order, from superior to inferior.