Human A and P Unit 3 Vocabulary

decussation

the crossing over of nerve tracts from one side of the body to the other, allowing each side of the brain to control the opposite side of the body (occurs in both sensory and motor pathways)

contralateral

anatomical direction term about the opposite side of the body

ipsilateral

anatomical direction term about the same side of the body

first order neuron

specialized nerve cells that transmit sensory information from the body’s periphery to the central nervous system (CNS)

second order neuron

interneurons that transmit sensory information from the spinal cord of brainstem to the thalamus

third order neurons

sensory neurons that relay information from the thalamus to the primary somatosensory cortex in the brain

gracile fasciculus

a sensory pathway within the spinal cord responsible for transmitting sensations of fine touch, vibration, and proprioception (awareness of body position) from the lower body and trunk (below the level of T6)

cuneate fasciculus

a sensory pathway in the spinal cord that transmits information about fine touch, vibration, and conscious proprioception from the upper body, specifically from the arms, hands, and part of the trunk

spinothalamic tract

a vital sensory pathway in the human nervous system, primarily responsible for carrying sensations of pain, temperature, and crude touch from the body to the brain

spinoreticular tract

an ascending sensory pathway in the central nervous system that carries pain and temperature information from the spinal cord to the reticular formation in the brainstem

spinocerebellar tract

a group of sensory pathways that relay unconscious proprioceptive information from the body to the cerebellum

upper motor neurons

nerve cells, within the central nervous system that originate in the brain and send signals to lower motor neurons in the brainstem and spinal cordlow

lower motor neurons

nerve cells that transmit signals from the spinal cord or brainstem (cranial nerve nuclei) to muscles, ultimately causing movement

corticospinal tracts

the primary descending motor pathways in the human nervous system, responsible for voluntary movement

tectospinal tract

a descending nerve pathway that connects the midbrain tectum (specifically the superior colliculus) to the spinal cord, primarily the cervical region

reticulospinal tract

a motor pathway in the human nervous system that originates in the reticular formation of the brainstem and descends to influence spinal motor neurons

vestibulospinal tracts

descending neural pathways in the spinal cord that originate from the vestibular nuclei in the brainstem

dermatome

a specific area of skin that is innervated by sensory nerve fibers originating from a single spinal nerve

muscle spindle

specialized sensory receptors within skeletal muscles that detect changes in muscle length and the rate of that change, providing the CNS with information about body position and movement

somatic reflex

an involuntary, automatic, and quick response to a stimulus, mediated by the somatic nervous system involving skeletal muscle movement

proprioceptor

sensory receptors that provide the brain with information about body position and movement

intrafusal fibers

specialized muscle fibers located within muscle spindles, which are sensory organs within skeletal muscles

extrafusal fibers

the regular skeletal muscle fibers that are responsible for generating the force needed for movement

gamma motor neuron

a type of lower motor neuron that regulates the sensitivity of muscle spindles to stretch by controlling the contraction of intrafusal muscle fibers

primary afferent fiber

sensory neurons that transmit sensory information from the periphery to the central nervous system, specifically the spinal cord and brain

secondary afferent fiber

sensory neurons that transmit information about static muscle length and other sensory information to the central nervous system

monosynaptic reflex

a rapid, automatic response where a sensory neuron directly synapses with a motor neuron in the spinal cord, resulting in a quick muscle contraction

reciprocal inhibition

a neuromuscular process where contraction of an agonist muscle (the muscle causing movement) is accompanied by the relaxation of its antagonistic muscle (the muscle that opposes the movement)

stretch reflex

a rapid, involuntary contraction of a muscle in response to its own stretching

flexor reflex

a rapid, automatic withdrawal of a body part from a painful stimulus

polysynaptic reflex

involves multiple synapses and at least one interneuron between the sensory neuron and the motor neuron

crossed-extension reflex

a spinal reflex that occurs in response to a painful stimulus, often on one side of the body, and involves the opposite limb to maintain balance and stability

tendon reflex

an involuntary muscle contraction elicited by a quick, sharp tap on a muscle tendon, typically using a reflex hammer

ventricles (brain)

a network of interconnected, fluid-filled cavities within the brain parenchyma

pia mater

the innermost, delicate connective tissue layer of the meninges that directly covers the brain and spinal cord

arachnoid mater

one of the three meningeal layers surrounding the brain and spinal cord, lies between the pia mater and dura mater

dura mater

the outermost and toughest layer of the meninges, which protect the brain and spinal cord

choroid plexus

a network of blood vessels and cells located within the ventricles of the brain, responsible for producing cerebrospinal fluid

cerebrospinal fluid

a clear, watery fluid surrounds and protects the brain and spinal cord

blood-brain barrier

a protective, filtering layer that separates the brain from the blood, acting as a selective gatekeeper for substances entering the brain tissue

medulla oblongata

the lowest part of the brainstem, located at the base of the brain where it connects to the spinal cord

gracile nucleus

a sensory relay nucleus located in the dorsal medulla oblongata of the brainstem

cuneate nucleus

a gray matter nucleus in the dorsal medulla oblongata, specifically located lateral to th gracile nucleus

solitary nucleus

a key structure in the brainstem, specifically within the medulla oblongata

medullary cardiac centers

a group of neuronal clusters within the medulla oblongata of the brainstem that are responsible for regulating the autonomic nervous system’s control of the heart and blood vessels

medullary respiratory

located in the medulla oblongata of the brainstem and are crucial for regulating breathing

medullary vasomotor centers

a region within the medulla oblongata responsible for regulating blood pressure by controlling the tone of blood vessels and influencing heart rate

pons

a region of the brainstem, a “bridge” of nerve fibers that connect the cerebrum and cerebellum

pontine respiratory centers

a respiratory center that modulates the intensity and frequency of respiratory signals originating from the medulla oblongata

reticular formation

a complex network of interconnected neurons and nuclei located in the brainstem, specifically in the tegmentum, from the medulla oblongata to the midbrain

cerebellum

a structure in the back of the brain, often called the “little brain”, that plays a crucial role in coordinating voluntary movements, maintaining balance, and posture

superior colliculi

paired, midbrain structures involved in visual and auditory processing, particularly in orienting responses and controlling eye movements

inferior colliculi

paired structures located in the midbrain, specifically within the corpora quadrigemina, a larger group of structures forming the roof of the midbrain

red nucleus

a midbrain structure involved in coordinating limb movements and playing a role in both motor and non-motor functions

substantia nigra

a midbrain structure, specifically a part of the basal ganglia, that plays a crucial role in movement, reward, and cognition

reticular activating system

a network of neurons in the brainstem responsible for regulating arousal, consciousness, and the transition between wakefulness and sleep

thalamus

a paired, oval-shaped structure within the brain, located deep in the diencephalon, that acts as a central relay station for sensory and motor information

medial geniculate nucleus

a thalamus structure crucial for processing auditory information and primary relay station for auditory signals between the inferior colliculus and the auditory cortex

lateral geniculate nucleus

a major relay station in the visual pathway, located within the thalamus of the brain and receives visual information from the retina and relays it to the primary visual cortex

hypothalamus

a crucial brain region involved in maintaining the body’s internal balance (homeostasis)

cerebral cortex

the outermost layer of the brain and is responsible for higher-order cognitive functions like awareness, language, memory, and voluntary movement

basal nuclei

interconnected subcortical brain structures crucial for regulating voluntary motor control, procedural learning, and cognitive and emotional functions

limbic system

a group of interconnected brain structures primarily involved in emotion, memory, and motivation, forming the “emotional brain”

amygdaloid body

a paired, almond-shaped structure within the brain’s medial temporal lobe, playing a crucial role in emotional processing, particularly fear and aggression, and memory consolidation

hippocampus

a part of the brain’s limbic system, a small, curved structure located deep within the temporal lobe

corpus callosum

a large bundle of nerve fibers connecting the left and right cerebral hemispheres, facilitating communication and coordination between them

lateralization

the specialization of the brain’s two hemispheres for different functions

preganglionic fiber

a nerve fiber in the autonomic nervous system that originates from the central nervous system and projects to a ganglion

autonomic ganglion

clusters of nerve cell bodies within the autonomic nervous system, acting as a bridge between the central nervous system and peripheral tissues

postganglionic fibers

nerve fibers in the autonomic nervous system (ANS) that extend from a ganglion, where they synapse with preganglionic neurons, to their target effector organs

sympathetic chain ganglia

a paired chain of nerve cell bodies (ganglia) along the vertebral column, forming part of the sympathetic nervous system

collateral ganglia

clusters of nerve cell bodies in the sympathetic nervous system that are located in the abdomen and pelvis, anterior to the vertebral column

adrenal medulla

the inner portion of the adrenal gland, a small, triangular gland located on top of each kidney

varicosity

enlarged, twisted veins, most commonly found in the legs

muscarinic receptors

a type of G protein-coupled receptor that are activated by the neurotransmitter acetylcholine, and are primarily associated with the parasympathetic nervous system

nicotinic receptors

a family of ligand-gated ion channels that are activated by the neurotransmitter acetylcholine

norepinephrine

a chemical messenger that acts as both a hormone and a neurotransmitter

a1 receptors

involved in regulating various physiological processes, including neuronal excitability, neurotransmitter release, and sleep induction

a2 receptors

a type of adrenergic receptor, a G-protein-coupled receptor that binds to the neurotransmitter norepinephrine

b1 receptors

a type of protein receptor found on the surfaces of cells that respond to the neurotransmitters norepinephrine and epinephrine

b2 receptors

a cell surface protein, a type of G protein-coupled receptor, that plays a crucial role in mediating the effects of epinephrine (adrenaline) and norepinephrine on various tissues

b3 receptors

a subtype of adrenergic receptors primarily found in adipose tissue and urinary bladder, playing a role in regulating thermogenesis, lipolysis, and bladder muscle relaxation

monoamine oxidase (MOA)

a family of enzymes that breaks down monoamine neurotransmitters like serotonin, dopamine, and norepinephrine, as well as dietary monoamines

catechol-O-methyltransferase (COMT)

an enzyme that metabolizes catecholamines like dopamine, norepinephrine, and epinephrine

dual innervation

the situation where a single organ or tissue receives nerve impulses from both the sympathetic and parasympathetic branches of the autonomic nervous system

autonomic tone

the balance between sympathetic and parasympathetic nervous system activity, which governs involuntary functions like heart rate, blood pressure, and digestion

transduction

the process of converting a stimulus (like light, sound, or touch) into an electrical signal that can be understood by the nervous system

receptor potential

a graded potential, or localized change in membrane potential, that occurs in sensory receptor cells in response to a stimulus

sensation

the process where sensory receptors detect environmental stimuli and convert them into neural signals, which are then transmitted to the brain for processing

labeled line

a dedicated neural pathway, starting from a sensory receptor and ending in the brain, that transmits information about a specific type of sensory stimulus

receptive field

the specific area or region of stimulus space where a change in the stimulus will affect the firing rate of a neuron

phasic receptors

sensory receptors that responds quickly to a stimulus, initially producing a strong response, but then rapidly adapting and reducing their response to constant stimulus

tonic receptors

sensory receptors that maintain their level of activity, or signal, as long as a stimulus is present, meaning they adapt slowly to a constant stimulus

nociceptors

sensory neurons that detect potentially harmful stimuli, triggering the sensation of pain

somatosensory receptors

specialized nerve endings throughout the body that detect various sensations like touch, temperature, pain, and proprioception

mechanoreceptors

sensory receptors that respond to mechanical stimuli, such as touch, pressure, vibration, and sound

osmoreceptors

sensory cells, primarily found in the hypothalamus, that detect changes in osmotic pressure (solute concentration) of body fluids

exteroceptors

sensory receptors that detect stimuli originating from outside the body

interoceptors

sensory receptors that detect and respond to changes within the body, like those occurring in internal organs and tissues

amplitude

the extent or magnitude of a physical phenomenon, such as a wave or vibration, measured from a resting or equilibrium position