Nerves System

medulla oblongata

Lower or hindmost part of the brain; continuous with spinal cord; (`bulb' is an old term for medulla oblongata); the medulla oblongata is the most vital part of the brain because it contains centers controlling breathing and heart functioning

autonomic

The autonomic nervous system has two divisions: the sympathetic nervous system, which accelerates the heart rate, constricts blood vessels, and raises blood pressure, and the parasympathetic nervous system, which slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles.

Sensory neurons

are nerve cells within the nervous system responsible for converting external stimuli from the organism's environment into internal electrical impulses.

Two part of the central nervous system

the brain and the spinal cord

myelin sheath

the insulating covering that surrounds an axon with multiple spiral layers of myelin, that is discontinuous at the nodes of Ranvier, and that increases the speed at which a nerve impulse can travel along an axon—called also medullary sheath.

brainstem

the portion of the brain that is continuous with the spinal cord and comprises the medulla oblongata, pons, midbrain, and parts of the hypothalamus, functioning in the control of reflexes and such essential internal mechanisms as respiration and heartbeat.

neurotransmitter

A chemical substance that is released at the end of a nerve fiber by the arrival of a nerve impulse and, by diffusing across the synapse or junction, causes the transfer of the impulse to another nerve fiber, a muscle fiber, or some other structure.

sympathetic

A division of the (vertebrate) autonomic nervous system that is chiefly involved in producing an immediate and effective response (e.g. fight-or-flight response) during stress or emergency situations.

Motor neurons

A nerve cell forming part of a pathway along which impulses pass from the brain or spinal cord to a muscle or gland.

structure of a neuron

Neurons contain organelles common to many other cells, such as a nucleus and mitochondria. They also have more specialized structures, including dendrites and axons. Once a signal is received by the dendrite, it then travels passively to the cell body.

pons

Region of the brain that acts as a relay station between the cerebellum and the cerebrum. The pons is part of the brain stem, and it also aids the medulla in the control of breathing

Three types of neurons

Sensory neurons , Motor neurons , Associative Neuron

cerebrum

The largest part of the vertebrate brain, filling most of the skull and consisting of two cerebral hemispheres divided by a deep groove and joined by the corpus callosum, a transverse band of nerve fibers. The cerebrum processes complex sensory information and controls voluntary muscle activity.

function of a myelin sheath

The main purpose of a myelin layer (or sheath) is to increase the speed at which impulses propagate along the myelinated fiber. Along unmyelinated fibers, impulses move continuously as waves, but, in myelinated fibers, they "hop" or propagate by saltatory conduction.

peripheral system

The nervous system outside the brain and spinal cord.

midbrain

The part of the brain above the pons and below the thalamus, it is the uppermost part of the brainstem, and is involved in basic, unconscious body function

cerebellum

a large portion of the brain, serving to coordinate voluntary movements, posture, and balance in humans, being in back of and below the cerebrum and consisting of two lateral lobes and a central lobe. Origin of cerebellum.

hypothalamus

controls the autonomic nervous system and the secretion of hormones by the pituitary gland. Through these nerve and hormone channels, the hypothalamus regulates many vital biological processes, including body temperature, blood pressure, thirst, hunger, and the sleep-wake cycle.

parasympathetic

A division of the (vertebrate) autonomic nervous system whose physiological effects are mostly in opposition to those of the sympathetic nervous system; e.g. it is involved in the slowing of the heart beat and relaxing the muscles.

Associative Neuron

A nerve cell that is within the central nervous system and that links sensory and motor neurons.

reflex arc

A sensory neuron carries the message from the receptor to the central nervous system (the spinal cord and brain). A motor neuron carries the message from the central nervous system to the effector. In a knee-jerk reflex arc the sensory neuron directly connects to the motor neuron in the spinal cord.

the parts of the brain

The brain is made of three main parts: the forebrain, midbrain, and hindbrain. The forebrain consists of the cerebrum, thalamus, and hypothalamus (part of the limbic system). The midbrain consists of the tectum and tegmentum. The hindbrain is made of the cerebellum, pons and medulla.

central nervous system

The central nervous system (CNS) is the part of the nervous system consisting of the brain and spinal cord.

somatic

The somatic nervous system is part of the peripheral nervous system, which is the entire nervous system outside of the brain and spinal cord. Specifically, the somatic nervous system is responsible for movement of voluntary muscles and the process known as a reflex arc.

spinal cord function

The spinal cord carries out two main functions: It connects a large part of the peripheral nervous system to the brain. Information (nerve impulses) reaching the spinal cord through sensory neurons are transmitted up into the brain.

thalamus

They are defined by their locations, functions, and anatomy. The thalamus is a structure in the middle of the brain. It is located between the cerebral cortex and the midbrain. It works to correlate several important processes, including consciousness, sleep, and sensory interpretation.