Key Words
autonomic nervous system
The autonomic nervous system is an important part of the peripheral nervous system. It helps maintain a balance in the involuntary functions of the body and allows the body to react in times of emergency. It contains the sympathetic and parasympathetic nervous systems.
cerebrum
The cerebrum is the largest and highest section of the brain. It is responsible for reasoning, thought, memory, judgment, speech, sensation, sight, smell, hearing, and voluntary body movement.
midbrain
The midbrain is the section below the cerebrum at the top of the brainstem. It conducts impulses between brain parts and for certain eye and auditory reflexes.
peripheral nervous system
The peripheral nervous system (PNS) consists of the nerves outside the brain and spinal cord. It has the somatic and autonomic divisions.
thalamus
The thalamus acts as a relay center and directs sensory impulses to the cerebrum; it allows conscious recognition of pain and temperature.
brain
The brain is a mass of nerve tissue well protected by membranes and the cranium. It contains different lobes and sections, each with different functions for reasoning, memory, speech, sensation, voluntary movement, coordination, and vital reflex actions.
diencephalon
The diencephalon is located between the cerebrum and midbrain. It contains the thalamus and hypothalamus.
nerves
Nerves are a combination of many nerve fibers located outside the brain and spinal cord. They carry sensory (afferent) messages to the brain and motor (efferent) messages from the brain.
pons
The pons is located below the midbrain and in the brainstem. It conducts messages to other parts of the brain and controls certain reflex actions including chewing, tasting, and saliva production; it assists with respiration.
ventricles
The ventricles are four hollow spaces in the brain that produce and store cerebrospinal fluid and allow it to circulate
central nervous system
The central nervous system (CNS) consists of the brain and spinal cord.
hypothalamus
The hypothalamus regulates and controls the autonomic nervous system, temperature, appetite, water balance, sleep, and blood vessel constriction and dilation. It is also involved in emotions such as anger, fear, pleasure, pain, and affection.
nervous system
The nervous system is a complex, highly organized system that coordinates all body activities and enables the body to respond and adapt to changes inside and outside the body.
somatic nervous system
The somatic nervous system carries messages between the CNS and the body. It includes 12 pairs of cranial nerves and 31 pairs of spinal nerves.
cerebellum
The cerebellum is the section below the back of the cerebrum. It is responsible for muscle coordination, balance, posture, and muscle tone.
medulla oblongata
The medulla oblongata is the lowest part of the brainstem. It connects with the spinal cord and controls heartbeat, respiration, swallowing, coughing, and blood pressure.
neuron
A neuron is the basic structural unit of the nervous system. It consists of a cell body, dendrites (carry impulses toward the cell body), and an axon (carries impulses away).
spinal cord
The spinal cord continues down from the medulla oblongata and ends at the first or second lumbar vertebra. It carries sensory (afferent) and motor (efferent) messages and is surrounded and protected by vertebrae.
cerebrospinal fluid
Cerebrospinal fluid is a clear, colorless fluid that circulates in the ventricles and through the subarachnoid space. It acts as a shock absorber, carries nutrients, and removes metabolic waste.
meninges
The meninges are three membranes that cover and protect the brain and spinal cord:
• dura mater (outer layer)
• arachnoid membrane (middle, web-like layer)
• pia mater (innermost layer attached to brain and spinal cord)
parasympathetic
The parasympathetic nervous system counteracts the sympathetic nervous system by slowing heart rate, decreasing respiration and blood pressure, and increasing activity in the digestive tract.
sympathetic
The sympathetic nervous system prepares the body for emergency by increasing heart rate, respiration, and blood pressure, and slowing digestion — the “fight or flight” response.