The brain is the neurological center of an organism.
Neural development is the process by which the brain develops from a primitive structure into the complex organ in the developed organism.
Understanding the brain is of vital importance to psychologists because of its influence over behavior and mental states.
Sleep disorders cause sleep disturbances that affect the amount, quality, or timing of sleep or that induce abnormal events during sleep.
The cerebral cortex of the brain is divided into four lobes responsible for distinct functions: frontal, parietal, temporal, and occipital.
The meninges refer to the several membrane layers that encase the brain.
Tight junctions present in the blood-brain barrier separate circulating blood from cerebrospinal fluid, regulating diffusion into the brain.
Cerebrospinal fluid is a clear fluid that acts as a cushion for the brain and maintains overall central nervous system homeostasis.
The ventricular system is a set of hollow cavities in the brain filled with cerebrospinal fluid.
The brainstem regulates vital cardiac and respiratory functions and acts as a vehicle for sensory information.
The medulla oblongata controls autonomic functions and connects the higher levels of the brain to the spinal cord.
The pons is a relay station between the forebrain and cerebellum that passes sensory information from the periphery to the thalamus.
The midbrain plays a major role in both wakefulness and regulation of homeostasis.
The reticular formation assists in regulation of the sleep cycle and detecting sensory salience.
The cerebellum, which looks like a separate structure attached to the bottom of the brain, plays an important role in motor control.
Cerebellar function was once believed to be motor-specific, but newer findings suggest the cerebellum is also involved in higher-level brain processing.
Distinct parts of diencephalon perform numerous vital functions, from regulating wakefulness to controlling the autonomic nervous system.
The thalamus is a small structure in the center of the brain that acts as a relay center for sensory and motor information.
The hypothalamus serves as a gateway between the nervous system and endocrine system.
The epithalamus connects the limbic system to other parts of the brain.
Circumventricular organs are situated adjacent to the brain ventricles and sense concentrations of various compounds in the blood.
With the assistance of the cerebellum, the cerebrum controls all voluntary actions in the body.
The cortex is divided into four main lobes: frontal, parietal, occipital, temporal.
White matter is composed of myelinated axons and glia and connects distinct areas of the cortex.
The basal ganglia is important for the control of movement and forming habits, and each of its components has a complex internal
anatomical and neurochemical organization.
The limbic system makes up the inner border of the cortex and is vital for emotion, motivation, and memory.
Sensory areas of the brain receive
and process sensory information, including sight, touch, taste, smell, and hearing.
The motor areas, arranged like a pair of headphones across both cortex hemispheres, are involved in the control of voluntary movements.
Associative areas of the cortex integrate current states with past states to predict proper responses based on sets of stimuli.
The human brain is composed of a right and a left hemisphere, and each participates in different aspects of brain function.
The central nervous system (CNS) develops from a longitudinal groove on the neural plate that forms the rudimentary nervous system.
Traumatic brain injury (TBI) occurs when an external force injures the brain and can be caused by a direct impact or by acceleration alone.
A cerebrovascular accident results from loss of oxygenated blood to a region of the brain and is typically accompanied by neuronal loss.
A transient ischemic attack is similar to a stroke; though without permanent damage, it can serve as an important risk factor for stroke.
Alzheimer's disease is an age-linked neurodegenerative disorder characterized by marked dementia.
A brain tumor is a pathological abnormal growth of cells in the brain.
ADHD is a developmental disorder characterized by problems with focus and self-control.
Medulla injury results in a wide variety of deficits including numbness, difficulty swallowing, slurred speech, and poor coordination.
Ataxia refers to potentially debilitating motor dysfunction, which can be caused by both hereditary and environmental factors.
Aphasia refers to an impaired language ability, and is often caused from brain damage; there are several subforms.
'Phantom limb sensation' is characterized by feeling as if a missing limb were still attached to the body.
Basal ganglia disease refers to physical dysfunctions that occur when basal ganglia fail to suppress unwanted movements.
Amnesia refers to any form of memory loss; there are many causes and types.
Neurological examinations verify proper sensory and motor neurological functions.
The spinal cord runs along the inside of the vertebral column and serves as the signaling conduit between the brain and the periphery.
The spinal cord derives from the neural tube in two processes: primary and secondary neurulation.
The spine encases the spinal cord for protection and support.
The grey matter of the spinal cord contains neuronal cell bodies, dendrites, axons, and nerve synapses.
The white matter of the spinal cord is composed of bundles of myelinated axons.
A spinal cord injury (SCI) refers to any injury to the spinal cord that is caused by trauma and not disease.
Amyotrophic lateral sclerosis (ALS) is caused by degeneration of upper and lower motor neurons, resulting in muscle weakness and atrophy.
An analgesic is a drug used to relieve pain (to achieve analgesia).
Syphilis is a sexually transmitted infection (STI) caused by the bacterium Treponema pallidum.
Paralysis describes the loss of function in a muscle or muscle groups, typically caused by damage to the spinal cord.
Spinal cord compression occurs when the spinal cord is compressed by bone fragments.
A lumbar puncture, or spinal tap, is a procedure used to collect a sample of cerebrospinal fluid (CSF), typically for diagnostic purposes.
Sensation refers to our ability to detect or sense the physical qualities of our environment.
The goal of sensation is detection, while the goal of perception is to create useful information about our environment.
A sensory modality (also called a stimulus modality) is an aspect of a stimulus or what is perceived after a stimulus.
Sensory receptors are primarily classified as chemoreceptors, thermoreceptors, mechanoreceptors, or photoreceptors.
Some sensory receptors can be classified by the physical location of the receptor.
The somatosensory system is composed of the neurons that make sensing touch, temperature, and position in space possible.
Touch is sensed by mechanoreceptive neurons that respond to pressure in various ways.
Proprioception refers to the sense of knowing how one's body is positioned in three-dimensional space.
The somatosensory pathway is composed of three neurons located in the dorsal root ganglion, the spinal cord, and the thalamus.
The cortical sensory homunculus is located in the postcentral gyrus and provides a representation of the body to the brain.
The ventral and dorsal spinocerebellar tracts convey proprioceptive information from the body to the cerebellum.
A nerve is the primary structure of the peripheral nervous system and is composed of bundles of axons.
Nerves are primarily classified based on their direction of travel to or from the CNS, but they are also subclassified by other nerve characteristics.
The peripheral nervous system has 12 pairs of cranial nerves that control much of the motor and sensory functions of the head and neck.
The olfactory nerve, or cranial nerve I, is the first of 12 cranial nerves and is responsible for the sense of smell.
The optic nerve (cranial nerve II) receives visual information from photoreceptors in the retina and transmits it to the brain.
The oculomoter nerve (cranial nerve III) controls eye movement, such as constriction of the pupil and open eyelids.
The trochlear nerve (cranial nerve IV) is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.
The trigeminal nerve is the fifth cranial nerve and it is responsible for sensation and motor function in the face and mouth.
The abducens nerve (cranial nerve VI) controls the lateral movement of the eye through innervation of the lateral rectus muscle.
The facial nerve (cranial nerve VII) determines facial expressions and the taste sensations of the tongue.
The vestibulocochlear nerve (cranial nerve VIII) carries information about hearing and balance.
The glossopharyngeal nerve (cranial nerve IX) serves many distinct functions, including providing sensory innervation to various head and neck structures.
The vagus nerve (cranial nerve X) is responsible for parasympathetic output to the heart and visceral organs.
The accessory nerve (cranial nerve XI) controls the muscles of the shoulder and neck.
The hypoglossal nerve (cranial nerve XII) controls the muscles of the tongue.
Spinal nerves, a part of the peripheral nervous system (PNS), are mixed nerves that send motor, sensory, and autonomic signals between the CNS and the body.
The spinal nerves branch into the dorsal ramus, ventral ramus, the meningeal branches, and the rami communicantes.
A nerve plexus is a network of intersecting nerves that serve the same part of the body.
The anterior divisions of the thoracic spinal nerves (T1–T11) are called the intercostal nerves.
A dermatome is an area of skin that is supplied by a single spinal nerve, and a myotome is a group of muscles that a single spinal nerve root innervates.
Spinal nerves connect the brain and spinal cord to the limbs and organs of the body.
The cervical plexus is the plexus of the ventral rami of the first four cervical spinal nerves.
The brachial plexus is formed by the four lower cervical spinal nerves and the first thoracic spinal nerve.
The lumbar plexus is formed by the subcostal nerve and divisions of the first four lumbar nerves that arise from the middle to lower back.
The sacral plexus is the plexus of the three sacral spinal nerves (S2–S4) that arise from the lower back just above the sacrum.
The spinothalamic tract is a somatosensory tract and the corticospinal tract is a motor tract.
A neuromuscular junction exists between the axon terminal and the motor end plate of a muscle fiber where neurotransmitters are released.
A motor unit is comprised of a single alpha-motor neuron and all the muscle fibers it innervates.
The motor system is the part of the central nervous system that is involved with movement.
The basal ganglia are responsible for voluntary motor control, procedural learning, and eye movement, as well as cognitive and emotional functions.
The cerebellum is important for motor control—specifically coordination, precision, and timing—as well as some forms of motor learning.
The cerebellum uses feedforward processing and modularity to process information.
A reflex arc defines the pathway by which a reflex travels—from the stimulus to sensory neuron to motor neuron to reflex muscle movement.
Spinal reflexes include the stretch reflex, the Golgi tendon reflex, the crossed extensor reflex, and the withdrawal reflex.
Pain is an unpleasant sensation caused by the activation of nociceptors by thermal, mechanical, chemical, or other stimuli.
Localization of pain is determined by whether the pain is superficial somatic, visceral, or deep somatic.
The peripheral nervous system develops from two strips of tissue called the neural crest, running lengthwise above the neural tube.
The peripheral nervous system (PNS) is able to repair and regenerate itself, but the central nervous system is incapable of doing so.
One of the effects of aging on the nervous system is the loss of neurons in the cerebral cortex.
Lidocaine, a local anesthetic that is commonly used in dentistry, is injected directly into the nerve to block pain sensation in the mouth.
Shingles, the common name for herpes zoster, is caused by latent varicella zoster virus, the same virus which causes chickenpox in children.
Poliomyelitis is an infection by the polio virus that affects the motor neurons of the central nervous system.
The phrenic nerve provides motor innervation and receives sensory information from the diaphragm.
Lesions in nerves of the brachial plexus are classified as obstetric or traumatic as a result of shoulder trauma, inflammation, or tumors.
Sciatica pain may be felt in the lower back, buttocks, or along the leg and foot.
Assessment of reflex activity is useful in determining the health of the central nervous system.
The peripheral nervous system includes both a voluntary, somatic branch and an involuntary branch that regulates visceral functions.
The autonomic nervous system (ANS) contains two subdivisions: the parasympathetic (PSNS) and sympathetic (SNS) nervous systems.
In the autonomic nervous system (ANS), nerve fibers that connect the central nervous system to ganglia are known as preganglionic fibers.
Autonomic ganglia are clusters of neuron cell bodies that transmit sensory signals from the periphery to the integration centers in the CNS.
In the autonomic nervous system, fibers from the ganglion to the effector organ are called postganglionic fibers.
Autonomic plexuses are formed from sympathetic and parasympathetic fibers that innervate and regulate the overall activity of visceral organs.
Parasympathetic ganglia are the autonomic ganglia of the parasympathetic nervous system that lie near or within the organs they innervate.
Sympathetic ganglia are the ganglia of the sympathetic nervous system that initiate fight-or-flight, stress-mediated responses.
Autonomic reflexes are unconscious motor reflexes relayed from the organs and glands to the CNS through visceral afferent signaling.
The sympathetic division of the autonomic nervous system maintains internal organ homeostasis and initiates the stress response.
The parasympathetic nervous system regulates organ and gland functions during rest and is considered a slowly activated, dampening system.
The sympathetic and parasympathetic autonomic nervous systems cooperatively modulate internal physiology to maintain homeostasis.
The medulla oblongata, in the lower half of the brainstem, is the control center of the autonomic nervous system.
Acetylcholine is a neurotransmitter in the central and peripheral nervous systems that affects plasticity, arousal, and reward.
Adrenergic receptors are molecules that bind catecholamines. Their activation leads to overall stimulatory and sympathomimetic responses.
Drugs effecting cholinergic neurotransmission may block, hinder, or mimic the action of acetylcholine and alter post-synaptic transmission.
Horner's syndrome presents with drooping eyelids and pupil constriction, and is indicative of a problem in the sympathetic nervous system.
Raynaud's phenomenon is a vasospastic disorder that causes discoloration of the fingers and toes in response to cold or stress.
Autonomic dysreflexia is an acute reaction of the autonomic nervous system to overstimulation in patients with previous spinal cord injury.
The nervous system is a network of cells called neurons that coordinate actions and transmit signals between different parts of the body.
The primary function of the nervous system is to coordinate and control the various body functions.
The CNS includes the brain and spinal cord, while the PNS is a network of nerves linking the body to the brain and spinal cord.
Glia, named from the Greek word for "glue," support and scaffold neurons while performing other unique functions.
The two kinds of glia cells in the PNS, schwann cells and satellite cells; each have unique functions.
A number of anatomically neuron types have evolved to participate in different organismal functions.
Neurons can be classified by direction of travel, neurotransmitter utilized, or electrophysiological properties.
Clusters of cell bodies in the central nervous system are called nuclei, while the cell bodies lining the nerves in the peripheral nervous system are called ganglia.
A bundle of axons is called a nerve in the peripheral nervous system and a tract in the central nervous system.
The central nervous system consists of a central cavity surrounded by gray matter made of neuronal cell bodies and white matter made of myelinated axons.
When a neuron is stimulated, an electrical impulse is generated and conducted along the length of its axon. This process, called action potential, underlies many nervous system functions.
Ion channels are membrane proteins that allow ions to travel into or out of a cell.
The potential difference in a resting neuron is called the resting membrane potential.
The membrane potential allows a cell to function as a battery, providing electrical power to activities within the cell and between cells.
Neurons typically send signals over long distances by generating and propagating action potentials over excitable axonal membrane.
A synapse is a structural junction that mediates information transfer from one neuron to the next or from one neuron to an effector cell as in muscle or gland.
Postsynaptic potentials are excitatory or inhibitory changes in the graded membrane potential in the postsynaptic terminal of a chemical synapse.
Synaptic transmission is a chemical event which is involved in the transmission of the impulse via release, diffusion, receptor binding of neurotransmitter molecules and unidirectional communication between neurons.
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse.
Although both ionotropic and metabotropic receptors are activated by neurotransmitters, ionotropic receptors are channel-linked while metabotropic receptors initiate a cascade of molecules via G-proteins.
Serial memory processing compares a memory to a target stimulus, while parallel processing carries out multiple operations simultaneously.
Embryonic neural development includes the birth and differentiation of neurons from stem cell precursors.