PNB CNS & PNS

Exam 3

Diencephalon

Responsible for homeostatic controls, hormone control, smooth muscle control (dig. sys), and temp regulation.

Brainstem

Acts as a reflex center and controls vitals.

Cerebellum

Responsible for the coordination of movement.

Cerebral Cortex

The outermost layer of gray matter that forms the wrinkled outer surface of the cerebrum, responsible for higher level cognitive functions.

Gyri

The ridges (folds) on the surface of the cerebrum

Sulci

The depressions (grooves) on the surface of the cerebrum.

Longitudinal Fissure

Divides the cerebral hemispheres into left and right sides.

Transverse fissure

Separates the cerebrum from the cerebellum.

Central Sulcus

Separates the frontal lobe from the parietal lobe.

Lateral Fissure

Separates the temporal lobe from the frontal and parietal lobes.

Contralateral Control

The principle where each cerebral hemisphere controls the opposite side of the body.

Frontal Lobe

Lobe responsible for Motor function, speech formation, personality, and emotion.

Parietal Lobe

Lobe containing the Somatosensory Cortex where sensations (skin, muscles, joints) become conscious.

Occipital Lobe

Lobe responsible for visual processing and storing visual memories.

Temporal Lobe

Lobe responsible for hearing, speech, language, and smell.

Gray Matter

Composed mainly of cell bodies (and dendrites/unmyelinated axons); the area where processing occurs.

White Matter

Composed of myelinated axons in the nervous system.

Nuclei

Clusters of gray matter (cell bodies) located inside the CNS (e.g., Basal Ganglia).

Basal Ganglia

A collection of nuclei (gray matter) deep inside the brain.

Commissural Fibers

Fiber tracts that connect the two cerebral hemispheres (e.g., corpus callosum).

Projection Fibers

Fiber tracts that connect the cerebrum to other regions (e.g., spinal cord or lower brain centers).

Association Fibers

Fiber tracts that connect regions within the same cerebral hemisphere.

Blood-Brain Barrier (BBB)

A highly selective membrane that protects the brain from substances circulating in the blood.

Cerebrospinal Fluid (CSF)

Fluid that protects and cushions the brain and spinal cord.

Choroid Plexus

Specialized clusters of capillaries found in the ventricles of the brain that produce Cerebrospinal Fluid (CSF).

CSF Composition vs. Plasma

CSF is similar to blood plasma but has less protein and different ion concentrations, making it a very selective, filtered fluid.

Astrocyte Feet

Components of glial cells (astrocytes) that wrap around capillaries, forming the tight junctions of the Blood-Brain Barrier (BBB).

Substances that cross the BBB

Lipid-soluble substances like gases, alcohol, nicotine, and anesthetics can easily cross the barrier.

Ventricles

Fluid-filled chambers deep within the brain where CSF is produced and circulated.

Thalamus

The largest part of the Diencephalon; acts as the major relay station for all sensory information (except smell) going to the cortex.

Hypothalamus

 part of the diencephalon that controls the pituitary gland and regulates, major homeostatic controls such as thirst and hunger

Epithalamus

part of the diencephalon that contains the penal gland, which secretes the hormone melatonin for sleep – wake cycles

Midbrain

The middle region of the Brainstem; acts as a bridge of tracts connecting the cerebrum with the cerebellum and spinal cord.

Medulla Oblongata

The lowest region of the Brainstem; contains vital centers that control heart rate, blood pressure, and breathing (respiratory rhythm).

Decussation of Pyramids

The point in the Medulla Oblongata where motor fiber tracts cross over to the opposite side of the body, establishing Contralateral Control.

Primary Motor Cortex

Located in the Frontal Lobe (precentral gyrus); controls voluntary movements of specific body parts.

brocas area

specialized area in the frontal lobe, usually in the left hemisphere, that controls the speech muscles for speech formation

Wernicke’s area

 specialized area, typically in the temporal lobe, essential for language comprehension

Homunculus (Motor or Sensory)

A distorted graphical map of the body showing the amount of cortex dedicated to control or sensation for each body part.

Limbic System

A group of deep brain structures (e.g., amygdala, hippocampus) integrated to form the "emotional brain"; also plays a role in memory.

Amygdala

A key limbic structure involved in processing emotions, especially fear and anxiety.

Hippocampus

A key limbic structure critical for forming and storing new memories.

Prediction: Brainstem Damage

Damage is often fatal because the Brainstem (Medulla Oblongata) controls the necessary vital centers for heart rate, blood pressure, and breathing.

Central Nervous System (CNS)

Consists of the Brain and Spinal Cord; the command center that integrates and processes information.

Dorsal Horns (Spinal Cord)

The posterior gray matter regions of the spinal cord where sensory neurons enter and synapse.

Ventral Horns (Spinal Cord)

The anterior gray matter regions of the spinal cord that contain the cell bodies of motor neurons (sending signals out to muscles).

Ascending Tracts

Fiber tracts in the spinal cord that carry sensory information up to the brain.

Descending Tracts

Fiber tracts that carry motor commands down from the brain to the spinal cord and body.

Sensation

Sensation

Perception

The conscious interpretation of the sensation, which occurs in the cerebral cortex (e.g., recognizing that the light is a red car).

Transduction

The process by which a sensory receptor converts the energy of a stimulus (e.g., light energy) into an electrical signal (a graded potential).

Receptor Potential (Generator Potential)

The graded potential produced by a sensory receptor in response to a stimulus; if strong enough, it triggers an action potential in the afferent neuron.

Adequate Stimulus

The specific type of energy (e.g., light, heat, pressure) to which a particular type of sensory receptor is most sensitive.

Receptor Modality

The type of sensation a receptor detects (e.g., pain, light, touch).

Receptor Threshold

The minimum intensity of a stimulus required to activate a specific sensory receptor.

Receptor Field

The area of the body that, when stimulated, changes the activity of a single afferent neuron.

Sensory Discrimination

The ability to distinguish between two separate stimuli applied simultaneously near each other.

Receptor Field Size & Discrimination

Smaller receptor fields (e.g., fingertips) lead to greater sensory discrimination (two-point). Larger fields (e.g., back) lead to poorer discrimination.

Frequency Coding (Intensity)

How afferent neurons signal varying stimulus intensity; a stronger stimulus causes the neuron to fire more frequently (more action potentials per second).

Population Coding (Intensity)

How afferent neurons signal varying stimulus intensity; a stronger stimulus activates a larger number of afferent neurons.

Lateral Inhibition

A process where a strongly stimulated receptor inhibits the activity of its less-stimulated neighbors; this sharpens the contrast and allows for the perception of discrete objects.

Functional Receptor Category

Based on the stimulus they detect (e.g., mechanoreceptors, chemoreceptors, photoreceptors).

Structural Receptor Category

Based on the complexity of their structure (e.g., free nerve endings, encapsulated nerve endings).

Location-Based Receptor Category

Based on where they are located (e.g., exteroceptors, interoceptors, proprioceptors).

Exteroceptors

Receptors located near the body surface that detect stimuli originating outside the body (e.g., touch, vision).

Interoceptors

Receptors located internal to the body that monitor internal conditions (e.g., blood pressure, oxygen levels).

Proprioceptors

Receptors found in muscles, tendons, and joints that sense body position and movement.

Mechanoreceptors

Receptors that respond to mechanical forces such as touch, pressure, vibration, stretch, and hearing.

Chemoreceptors

Receptors that respond to chemicals in an aqueous solution (e.g., smell, taste, blood chemistry).

Nociceptors

Receptors that respond to painful (potentially damaging) stimuli.