Central and Peripheral Nervous Systems Flashcards

Flashcards for reviewing lecture notes on the central and peripheral nervous systems, brain structures, and protective mechanisms.

Axon

• A long, slender projection of a nerve cell, or neuron.
• Conducts electrical impulses known as action potentials away from the neuron's cell body (or soma).
• Transmits information to other neurons, muscles, or glands.
• Each neuron typically has only one axon that branches at its end to form multiple axon terminals, which connect to other neurons at synapses.

Nerve

• A bundle of axons located in the peripheral nervous system (PNS) that transmits signals between the central nervous system (CNS) and other parts of the body.
• Can be composed of sensory (afferent) fibers, motor (efferent) fibers, or both.
• Surrounded by connective tissue layers that provide support and protection, including the endoneurium, perineurium, and epineurium.
• Serve as the communication lines of the PNS, facilitating sensory input, motor output, and autonomic functions.

Pathway/Tract

• A collection of axons traveling together within the central nervous system (CNS).

• Facilitate communication between different areas within the CNS, allowing for the integration and processing of information.

Commissure

• specific type of pathway that crosses the midline of the brain, connecting the left and right hemispheres.

Ganglia

• Clusters of neuron cell bodies located in the peripheral nervous system (PNS).
• Serve as relay stations for nerve signals, containing the cell bodies of neurons that transmit information between the CNS and the periphery.
• Can be sensory, containing the cell bodies of afferent neurons, or autonomic, containing the cell bodies of efferent neurons.
• Play a crucial role in integrating and modulating nerve signals before they reach their target tissues or organs.

Nuclei

• Clusters of neuron cell bodies located within the central nervous system (CNS).
• Regions of gray matter where the cell bodies of neurons are concentrated.
• Involved in a wide range of functions, including sensory processing, motor control, and higher-order cognitive functions.
• Play a central role in integrating and processing information within the CNS.

Forebrain (prosencephalon)

• develops into the cerebrum and diencephalon, responsible for higher-order cognitive functions, sensory processing, and endocrine regulation.

Midbrain (mesencephalon)

• involved in motor control, visual and auditory processing, and relaying information between the forebrain and hindbrain.

Hindbrain (rhombencephalon)

• develops into the pons, medulla oblongata, and cerebellum, which control essential functions such as respiration, heart rate, and motor coordination.

Cerebrum

• largest part of the brain and is responsible for higher-order cognitive functions such as language, memory, and reasoning.

Diencephalon

• located beneath the cerebrum

• includes the thalamus, hypothalamus, and epithalamus

• involved in sensory relay, endocrine regulation, and circadian rhythms.

Pons

• located in the brainstem, above the medulla and below the midbrain

• connects the cerebrum and cerebellum

• involved in respiration, sleep, facial movement, and auditory processing

Medulla Oblongata

• located at the base of the brainstem, continuous with the spinal cord

• contains autonomic control centers for vital functions

• involved in regulating heart rate, blood pressure, and breathing

Cerebellum

• located behind the brainstem, beneath the occipital lobes

• connected to the brainstem via cerebellar peduncles

• involved in motor coordination, balance, and motor learning

Brainstem

• A heavily interconnected region of the brain composed of the pons, medulla oblongata, and midbrain.
• Serves as a vital conduit for information flow between the cerebrum, cerebellum, and spinal cord.
• Contains many important nuclei and control centers, regulating functions like heart rate, respiration, sleep, and consciousness.
• Damage can result in severe neurological deficits due to its critical role in maintaining life.

Cerebral Cortex

• The outermost layer of the cerebrum, composed of gray matter, which is primarily made up of neuron cell bodies.
• Responsible for higher-order cognitive functions such as perception, language, memory, and consciousness.
• Highly convoluted, with numerous gyri (ridges) and sulci (grooves) that increase its surface area.
• Different regions are specialized for specific functions.

White Matter

• The inner layer of the cerebrum, composed primarily of myelinated axons, which give it a whitish appearance.
• Responsible for transmitting information between different regions of the cerebral cortex and between the cerebral cortex and other parts of the brain.
• The myelin sheath that surrounds the axons acts as an insulator, increasing the speed and efficiency of signal transmission.
• Lesions can disrupt these communication pathways, leading to various neurological deficits.

Subcortical Nuclei

• Clusters of neuron cell bodies located beneath the cerebral cortex, also composed of gray matter.
• Involved in a variety of functions, including motor control, learning, and reward.
• Examples include the basal ganglia, amygdala, and hippocampus.
• Play a crucial role in integrating and modulating cortical activity.

Corpus Callosum

• A large bundle of axons connecting the left and right cerebral hemispheres, allowing for communication and coordination between the two sides of the brain.
• Plays a vital role in integrating sensory, motor, and cognitive information from both hemispheres, enabling the brain to function as a unified whole.
• Damage can result in disconnection syndromes, where the two hemispheres operate independently, leading to a variety of neurological and behavioral deficits.

Frontal Lobe

• located at the front of each cerebral hemisphere, behind the forehead

• includes the prefrontal cortex (higher thinking) and primary motor cortex (voluntary movement)

• involved in executive functions like planning, decision-making, emotional regulation, personality expression, and voluntary motor control

Parietal Lobe

• located behind the frontal lobe and above the temporal lobe

• includes the primary somatosensory cortex, which processes touch, pressure, temperature, and pain

• involved in sensory integration, spatial reasoning, body awareness, and attention to external stimuli

Occipital Lobe

• located at the back of the brain, posterior to the parietal and temporal lobes

• contains the primary visual cortex and visual association areas

• involved in processing and interpreting visual input, including light, shape, color, motion, and depth perception

Temporal Lobe

• located on the sides of the brain, beneath the lateral (Sylvian) sulcus

• includes the primary auditory cortex, parts of the limbic system, and Wernicke’s area (usually in left hemisphere)

• involved in auditory perception, language comprehension, memory encoding and retrieval, and emotion processing

Gyri

• Sinuous ridges on the surface of the cerebrum, which increase the surface area of the cerebral cortex.
• The increased surface area allows for a greater number of neurons and more complex neural connections, enhancing the brain's processing capacity.
• The pattern is relatively consistent across individuals, allowing for the identification of specific cortical regions.

Sulci

• Grooves that separate the gyri on the cerebrum, also serving to increase the surface area of the cerebral cortex.
• The sulci create infoldings that allow for more neurons to be packed into the limited space of the skull.
• Some sulci are particularly prominent and serve as landmarks for dividing the cerebral cortex into different lobes and regions.

Pyramidal Cells

• The primary output neurons of the cerebral cortex, characterized by their pyramid-shaped cell bodies.
• Excitatory neurons that use glutamate as their primary neurotransmitter.
• Organized into distinct layers within the cortex and form complex circuits that are responsible for processing information and generating behavior.

Nonpyramidal Cells

• A diverse group of neurons in the cerebral cortex that are primarily involved in receiving inputs and local processing of information.
• Mainly inhibitory neurons that use GABA as their primary neurotransmitter.
• Play a crucial role in modulating the activity of pyramidal cells and refining cortical circuits.

Basal Nuclei

• A group of subcortical nuclei, including the caudate nucleus, putamen, globus pallidus, substantia nigra, and subthalamic nucleus.
• Play an important role in controlling movement and posture, as well as in more complex aspects of behavior, such as reward and decision-making.
• Dysfunction can result in movement disorders, such as Parkinson's disease and Huntington's disease.

Limbic System

• A functional system in the brain that includes portions of the frontal-lobe cortex, temporal lobe, thalamus, and hypothalamus.
• Associated with learning, emotional experience and behavior, and a wide variety of visceral and endocrine functions.
• Plays a crucial role in regulating emotions, motivation, and memory, and is involved in many psychiatric disorders.

Diencephalon

• The posterior part of the forebrain, containing the thalamus, hypothalamus, epithalamus, and subthalamus.
• Located between the cerebral hemispheres and the midbrain.
• Structures play a critical role in sensory processing, endocrine regulation, and motor control.

Thalamus

• A collection of several large nuclei that serve as synaptic relay stations and important integrating centers for most inputs to the cortex.
• Receives sensory information from the body and relays it to the appropriate areas of the cerebral cortex for further processing.
• Plays a role in motor control, attention, and consciousness.

Hypothalamus

• A small structure below the thalamus that serves as the master command center for neural and endocrine coordination.
• Regulates a wide range of functions, including body temperature, hunger, thirst, sleep-wake cycles, and emotional responses.
• Maintains homeostasis by integrating information from the brain and the body and coordinating appropriate responses.

Epithalamus

• A small mass of tissue that includes the pineal gland, which participates in the control of circadian rhythms through the release of the hormone melatonin.
• Located in the posterior part of the diencephalon, near the third ventricle.
• Also includes the habenula, which is involved in motivation and reward.

Cerebellum

• A structure located behind the pons and medulla oblongata that plays an important role in coordinating movements and controlling posture and balance.
• Receives input from the cerebral cortex, brainstem, and spinal cord and uses this information to fine-tune movements and maintain balance.
• Damage can result in ataxia, a condition characterized by impaired coordination and balance.

Reticular Formation

• A complex network of neurons and nerve fibers located in the brainstem that is essential for life.
• Involved in a wide range of functions, including regulating sleep-wake cycles, attention, arousal, and muscle tone.
• Plays a role in controlling vital functions such as heart rate, respiration, and blood pressure.

Reticular Formation

• The one part of the brain absolutely essential for life, due to its control over vital functions such as respiration and heart rate.

Dorsal Horns

• The posterior regions of gray matter in the spinal cord, projecting toward the back of the body.
• Receive sensory information from the body via afferent neurons.
• Contain a variety of interneurons that process and relay sensory information to other parts of the spinal cord and brain.

Ventral Horns

• The anterior regions of gray matter in the spinal cord, oriented toward the front of the body.
• Contain the cell bodies of motor neurons that innervate skeletal muscles.
• Motor neurons receive input from the brain and spinal cord and send signals to the muscles to initiate movement.

Spinal Nerves

• Nerves that connect the spinal cord to the rest of the body, carrying both sensory and motor information.
• Formed by the fusion of dorsal and ventral roots, which contain afferent and efferent fibers, respectively.
• Each spinal nerve innervates a specific region of the body, called a dermatome.

Nerves (PNS)

• Bundles of axons in the peripheral nervous system (PNS) that transmit signals between the central nervous system (CNS) and other parts of the body.
• Composed of many individual axons, each of which is surrounded by a myelin sheath.
• Can be sensory (afferent), motor (efferent), or mixed, containing both sensory and motor fibers.

Spinal Nerves

• The nerves that emerge directly from the spinal cord, carrying both sensory and motor information between the spinal cord and the body.
• Each corresponding to a specific region of the body.
• Are formed by the fusion of dorsal and ventral roots, which contain afferent and efferent fibers, respectively.

Cranial Nerves

• Nerves that emerge directly from the brain, providing sensory and motor innervation to the head and neck.
• Some cranial nerves are purely sensory, others are purely motor, and some are mixed, containing both sensory and motor fibers.
• Essential for a wide range of functions, including vision, hearing, taste, smell, speech, and swallowing.

Efferent Neurons

• Neurons that carry signals away from the central nervous system (CNS) to muscles, glands, and other tissues in the peripheral nervous system (PNS).
• Also known as motor neurons because they control muscle contraction and movement.
• Essential for motor control, autonomic regulation, and endocrine function.

Afferent Neurons

• Neurons that convey information from sensory receptors at their peripheral endings to the central nervous system (CNS).
• Also known as sensory neurons because they transmit sensory information from the body to the brain and spinal cord.
• Essential for sensory perception and provide the CNS with information about the external and internal environment.

Somatic Nervous System

• The division of the peripheral nervous system (PNS) that innervates skeletal muscle, controlling voluntary movements.
• Consists of motor neurons that originate in the brain and spinal cord and travel to the skeletal muscles.
• Responsible for all voluntary movements, such as walking, talking, and writing.

Autonomic Nervous System

• The division of the peripheral nervous system (PNS) that innervates smooth and cardiac muscle, glands, and gastrointestinal (GI) neurons, but not skeletal muscle cells.
• Controls involuntary functions such as heart rate, blood pressure, digestion, and respiration.
• Divided into two main branches: the sympathetic nervous system and the parasympathetic nervous system.

Somatic motor neurons

• Motor neurons that release the neurotransmitter acetylcholine at the neuromuscular junction, causing contraction of skeletal muscle fibers.
• Responsible for voluntary movements and are under conscious control.

Enteric Nervous System

• A network of autonomic neurons located in the wall of the gastrointestinal (GI) tract, responsible for controlling digestive functions.
• Often referred to as the "second brain" because it can function independently of the central nervous system (CNS).
• Regulates a wide range of digestive processes, including motility, secretion, and absorption.

Preganglionic Neurons

• Neurons that transmit signals between the central nervous system (CNS) and the autonomic ganglia.
• Originate in the brain or spinal cord and synapse with postganglionic neurons in the ganglia.
• Part of both the sympathetic and parasympathetic divisions of the autonomic nervous system (ANS).

Postganglionic Neurons

• Neurons that transmit signals between the autonomic ganglia and the effector cells in the target tissues or organs.
• Receive input from preganglionic neurons in the ganglia and release neurotransmitters that act on the effector cells.
• The neurotransmitter released varies depending on the division of the autonomic nervous system (ANS).

Sympathetic Division

• The division of the autonomic nervous system (ANS) that prepares the body for "fight-or-flight" responses.
• Increases heart rate, blood pressure, and respiration rate, while decreasing digestive activity.
• Activated in response to stress, fear, and excitement, allowing the body to respond quickly to threats.

Parasympathetic Division

• The division of the autonomic nervous system (ANS) that promotes "rest-and-digest" functions.
• Decreases heart rate, blood pressure, and respiration rate, while increasing digestive activity.
• Activated during relaxation and promotes energy conservation.

Sympathetic Trunks

• Chains of interconnected ganglia located close to the spinal cord in the sympathetic nervous system.
• Run along both sides of the vertebral column and receive input from preganglionic neurons.
• Allow for coordinated activation of the sympathetic nervous system throughout the body.

Acetylcholine

• A neurotransmitter released by preganglionic neurons in both the sympathetic and parasympathetic divisions of the autonomic nervous system (ANS) at the synapse with postganglionic neurons.

Acetylcholine

• The neurotransmitter released by postganglionic neurons in the parasympathetic division of the autonomic nervous system (ANS) at the synapse with effector cells.

Norepinephrine

• The primary neurotransmitter released by postganglionic neurons in the sympathetic division of the autonomic nervous system (ANS) at the synapse with effector cells.

Adrenal Medulla

• An endocrine gland located on top of the kidneys that is part of the sympathetic nervous system.
• Secretes mainly epinephrine (adrenaline) into the bloodstream in response to stress.
• Plays a crucial role in the "fight-or-flight" response.

Dual Innervation

• The innervation of many effector organs by both the sympathetic and parasympathetic divisions of the autonomic nervous system (ANS).
• Allows for precise control of organ function, as the sympathetic and parasympathetic divisions have opposing effects on many target tissues.
• The balance between sympathetic and parasympathetic activity determines the overall activity of the organ.

Fight-or-flight response

• A physiological response to a perceived harmful event, attack, or threat to survival.
• Characterized by the activation of the sympathetic nervous system, leading to increased heart rate, blood pressure, and respiration rate, as well as the release of stress hormones.
• Prepares the body to either confront the threat or flee from it.

Meninges

• The three layers of protective membranes that surround the central nervous system (CNS), including the brain and spinal cord.
• Consist of the dura mater (outer layer), arachnoid mater (middle layer), and pia mater (inner layer).
• Provide physical protection to the CNS and also contain cerebrospinal fluid (CSF), which cushions the brain and spinal cord and provides nutrients.

Cerebrospinal Fluid (CSF)

• A clear, colorless fluid that surrounds the brain and spinal cord, providing cushioning and protection.
• Produced by the choroid plexus, a network of blood vessels and specialized cells located in the ventricles of the brain.
• CSF circulates within the brain ventricles and subarachnoid space, and it is eventually reabsorbed into the bloodstream.

Choroid Plexus

• A specialized structure in the brain ventricles that produces cerebrospinal fluid (CSF).
• Consists of a network of blood vessels and specialized epithelial cells that filter the blood and secrete CSF.
• Responsible for maintaining the composition and volume of CSF, which is essential for the health and function of the brain and spinal cord.

Blood-Brain Barrier

• A protective barrier formed by specialized cells lining the blood vessels of the brain, which restricts the passage of substances from the bloodstream into the brain tissue.

• Formed by tight junctions between the endothelial cells

• Supported by astrocyte end-feet and pericytes