chapter 13-15

CNS

Central Nervous System, consisting of the brain and spinal cord.

Gray Matter

The central 'butterfly-shaped' region of the spinal cord, containing cell bodies, dendrites, unmyelinated axons, and synapses.

White Matter

Surrounds gray matter in the spinal cord and contains myelinated axons.

Posterior Median Sulcus

The posterior shallow longitudinal groove in the spinal cord.

Anterior Median Fissure

The anterior deep longitudinal groove in the spinal cord.

Central Canal

Internal passageway through the spinal cord filled with cerebrospinal fluid (CSF).

Cerebrospinal Fluid (CSF)

Fluid that fills the central canal and is produced by ependymal cells.

Ependymal Cells

Glial cells that line the central canal and produce cerebrospinal fluid (CSF).

Conus Medullaris

The tapered, inferior end of the spinal cord located at the L1–L2 vertebrae.

Filum Terminale

Fibrous strand from the spinal cord tip that anchors the cord to the coccyx.

Posterior (Dorsal) Side

Where sensory information enters the spinal cord.

Anterior (Ventral) Side

Where motor information exits the spinal cord.

Anterior Roots

Carry motor axons away from the spinal cord.

Posterior Roots

Carry sensory axons into the spinal cord.

Dorsal Root Ganglion

Contains cell bodies of sensory neurons.

Spinal Nerve

A mixed nerve that is a fusion of ventral and dorsal roots.

Intervertebral Foramina

Passageways for spinal nerves.

Three Layers of Spinal Meninges

Dura mater, arachnoid mater, pia mater.

Dura Mater

Tough outer layer of the spinal meninges.

Arachnoid Mater

Web-like middle layer of the spinal meninges.

Pia Mater

Thin, inner layer of the spinal meninges that adheres to the spinal cord.

Posterior Horns

Contain sensory interneurons in the gray matter of the spinal cord.

Anterior Horns

Contain somatic motor neurons in the gray matter of the spinal cord.

Lateral Horns

Contain autonomic motor neurons, present only in thoracic/lumbar regions.

Ascending Tracts

Bundles of myelinated axons carrying sensory signals towards the brain.

Descending Tracts

Bundles of myelinated axons carrying motor signals away from the brain.

Neuron

A single nerve cell.

Nerve

A bundle of axons in the peripheral nervous system (PNS).

Epineurium

Connective tissue that surrounds the entire nerve.

Perineurium

Connective tissue that surrounds each fascicle (axon bundle) within the nerve.

Endoneurium

Connective tissue that surrounds individual axons.

Nerve Plexus

An interconnected network of spinal nerves supplying specific body regions.

Reflex Arc Steps

1. Stimulus activates receptor, 2. Sensory neuron activated, 3. Info processed in CNS, 4. Motor neuron activated, 5. Effector responds.

Stretch Reflex

A monosynaptic reflex that maintains muscle length, e.g. patellar reflex.

Withdrawal Reflex

A protective reflex that pulls a body part away from a painful stimulus.

Crossed-Extensor Reflex

Reflex that extends the opposite limb to support the body during a withdrawal reflex.

Innate Reflexes

Reflexes that are present at birth, e.g. blinking.

Acquired Reflexes

Learned reflexes, e.g. braking when driving.

Somatic Reflexes

Reflexes involving skeletal muscle, e.g. withdrawal reflex.

Visceral Reflexes

Reflexes involving smooth/cardiac muscle and glands, e.g. salivation, pupil constriction.

Spinal Reflexes

Reflexes processed in the spinal cord, e.g. stretch reflex.

Cranial Reflexes

Reflexes processed in the brainstem, e.g. pupillary light reflex.

Cerebrum

The largest and most complex brain region responsible for conscious thought, memory, and voluntary motor control.

Diencephalon

Brain region that contains thalamus, hypothalamus, and epithalamus, acting as a sensory relay and hormone regulator.

Brainstem

Comprising midbrain, pons, and medulla oblongata, it controls autonomic functions and reflexes.

Cerebellum

Brain region responsible for coordination, posture, balance, and motor memory.

Primary Brain Vesicles

Forebrain (prosencephalon), midbrain (mesencephalon), hindbrain (rhombencephalon).

Secondary Brain Vesicles

Derived from primary vesicles; ultimately develop into various brain structures.

Dura Mater (Cranial)

The tough outer layer of cranial meninges.

Arachnoid Mater (Cranial)

The middle, web-like layer of cranial meninges.

Pia Mater (Cranial)

The inner layer of cranial meninges, directly attached to the brain.

Subarachnoid Space

Space containing cerebrospinal fluid between arachnoid and pia mater.

Meningitis

Inflammation of the meninges, typically caused by infection.

Dural Sinus

Venous channels that drain blood from the brain into the internal jugular veins.

Cerebrospinal Fluid Functions

Cushions the brain/spinal cord, provides nutrients, removes waste, supports brain (buoyancy).

Sensory Pathways

Afferent tracks bringing sensory information in, often involving conscious thought, particularly concerning skeletal muscles.

Motor Pathways

Efferent tracks taking information out, especially related to somatic nervous system functions and skeletal muscle contractions.

Sensory Receptor Function

To produce a signal, create an action potential, and spread it into the central nervous system for processing.

Postcentral Gyrus

Area of the cerebral cortex where somatic sensory information is processed, mapped by the “homunculus.”

Homunculus

Mapping on the cerebral cortex corresponding to where each body part sends its sensory information; areas are proportionate to the number of receptors.

Precentral Gyrus

Area of cerebral cortex (sensorimotor) where signals from the homunculus are initiated.

Thalamus

Relay center like “Grand Central Station” that directs sensory information to specific areas on the cerebral cortex.

General senses

Temperature, pain, touch, pressure, vibration and proprioception.

Proprioception

Sense of body position; awareness of where limbs and other body parts are in space.

Special senses

Smell, taste, vision, equilibrium, and hearing. Each has its own special sensory organ.

Receptor Specificity

Sensory receptors pick up target information, such as light touch, deep touch, or pain.

Receptive Field

Area monitored by sensory receptors; smaller fields allow for more precise localization.

Transduction

Conversion of a stimulus into an action potential, often involving membrane distortion that affects ion gates.

Adaptation

Reduction in sensitivity to a constant stimulus, allowing the brain to avoid sensory overload by filtering out unnecessary information.

Tonic Receptors

Slow-adapting sensory receptors that are always active. An example of this is pain receptors.

Phasic Receptors

Fast-adapting sensory receptors that are inactive unless stimulated. They provide information about the intensity and rate of change.

Exteroreceptors

Receptors providing information about the external environment.

Proprioceptors

Receptors that detect body positions. These are found in skeletal muscles and joints.

Enteroreceptors

Receptors that monitor internal conditions, such as stretch receptors and baroreceptors.

Nociceptors

Pain receptors that are sensitive to temperature extremes, mechanical damage, and dissolved chemicals.

Thermoreceptors

Receptors specialized for temperature sensation. These are found in the dermis, skeletal muscles, liver, and hypothalamus.

Mechanoreceptors

Receptors specialized for mechanical distortion of a cell membrane. These help detect stretch.

Chemoreceptors

Receptors that detect chemical concentration changes. Such examples could be o2 or co2 detections from the carotid artery.

Tactile Receptors

Touch receptors which include pressure and vibrations.

Baroreceptors

Mechanoreceptors that detect pressure or stretch in blood vessels, the digestive system, the respiratory system, and the urinary tract.

Muscle Spindles

Proprioceptors that monitor skeletal muscle length. This is used to detect the stretch on the muscle.

Golgi Tendon Organs

Proprioceptors that detect tension in tendons.

Chemoreceptors

Detect chemical changes such as too much CO2 and not enough O2 in the brain.

First Order Neuron

Relays signal from peripheral nervous system (PNS) to central nervous system (CNS).

Second Order Neuron

Interneuron in the central nervous system (CNS) that usually decussates (crosses over).

Third Order Neuron

Carries signal from the thalamus to the cerebral cortex for conscious awareness. Routes signal to homunculus mapping.

Spinothalamic Pathways

Ascending sensory pathways includes the anterior and lateral tracts.

Posterior Column Pathways

Ascending sensory pathways in the posterior spinal cord tracts. This carries fine touch, fine vibrations, and fine proprioception.

Spinocerebellar Pathways

Ascending sensory pathways that carry proprioceptive information to the cerebellum.

Cuneate Fasciculus

Posterior column pathway, carries sensory information and proprioception from the upper body.

Gracilis Fasciculus

Posterior column pathway, carries sensory information and proprioception from the lower body.

Anterior Spinothalamic Tract

Anterior spinal cord tract, carries crude touch and pressure.

Lateral Spinothalamic Tract

Lateral spinal cord tract, carries pain and temperature.

Afferent

Bringing signals/information to an area.

Efferent

Carrying signals/information away from an area.

Upper Motor Neuron

Motor neuron with its cell body in the central nervous system (CNS).

Lower Motor Neuron

Motor neuron with its cell body in the brain stem or spinal cord and axon extending into the peripheral nervous system (PNS) to innervate a motor unit in a skeletal muscle.

The Pyramidal System

The corticospinal tract system, which carries voluntary motor signals. Decussation at the medulla is an important function.

Medulla

Important for nuclei for visceral sensory, tied to cardiovascular and respiratory centers.

Cerebellum

Responsible for the sense of muscle position. and also improves action that improves with practice.