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.