PNS/CNS

Root Words:

• Contra: Against or opposite.

• Ipsi: Same or on the same side.

• Lateral: On the side.

• Medial: On the middle or center.

Lobes of the Brain: The four main lobes are:

• Parietal lobe: Involves sensory perception and integration.

• Frontal lobe: Responsible for reasoning, motor control, and higher-level functions.

• Temporal lobe: Associated with processing auditory information and memory.

• Occipital lobe: Primarily involved in visual processing.

Internal Areas of the Brain: Key areas include:

• Cerebellum: Balance and coordination.

• Cerebrum: Largest part, responsible for higher brain functions.

• Gyri: Ridges on the brain's surface.

• Corpus callosum: Connects left and right hemispheres.

• Diencephalon: Contains thalamus and hypothalamus.

• Hypothalamus: Regulates homeostasis.

• Medulla oblongata: Controls involuntary functions.

• Midbrain: Associated with vision, hearing, and motor control.

• Pons: Relays signals in the brain.

• Spinal cord: Conducts sensory and motor information.

• Sulci: Grooves between gyri.

• Thalamus: Relay station for sensory information.

Definitions:

• Gyri: The raised folds of the brain.

• Sulci: The grooves between the gyri.

• Fissure: A deep groove in the brain, often separating lobes.

Cerebral Cortex Characteristics: The cerebral cortex has gray matter (neuronal cell bodies) on the outside and white matter (myelinated axons) on the inside, which increases surface area for cognitive functions.

Contralateral Function: The brain exhibits contralateral control, where each hemisphere controls the opposite side of the body (e.g., the right side of the brain controls the left side of the body).

Symmetrical Hemispheres: While structurally symmetrical, hemispheres can have different functions (e.g., language is typically left-sided in right-handed individuals).

Cerebral Cortex Involvement: The entire cerebral cortex is involved in various actions, reflecting the complexity of brain functions.

White vs Gray Matter: White matter consists of myelinated axons, while gray matter contains neuron cell bodies and dendrites.

Function of Ventricles: The ventricles are cavities in the brain that contain cerebrospinal fluid (CSF), and the choroid plexus produces this fluid.

Diencephalon Structures: The three primary structures are:

Meningeal Layers: The three protective layers are:

Homunculus: The homunculus is a visual representation showing the body areas corresponding to different regions of the brain, indicating motor and sensory functions.

Association Areas: These regions integrate different types of information and are essential for complex processing and higher-level cognitive functions.

Location of Language: Generally, language is located in the left hemisphere (Broca's and Wernicke's areas), while body language and non-verbal cues are often processed in the right hemisphere.

Homeostatic Imbalances: Examples include stroke (interruption of blood supply to the brain) and concussion (traumatic brain injury).

Spinal Cord Features: The spinal cord runs from the base of the skull down the vertebral column, with white matter located superficially and gray matter deeper inside.

Four Types of Sensory Receptors and Their Senses:

• Photoreceptors: detect light (vision)

• Mechanoreceptors: respond to mechanical pressure or distortion (touch, hearing)

• Chemoreceptors: detect chemicals (taste, smell)

• Thermoreceptors: respond to temperature changes (heat and cold)

• Nociceptors: respond to pain

Types of Nerves:

• Afferent Nerves: carry sensory information to the CNS (central nervous system)

• Efferent Nerves: carry motor commands from the CNS to muscles and glands

• Mixed Nerves: contain both afferent and efferent fibers

Structure of a Nerve:

• Composed of bundles of axons, each surrounded by connective tissue layers:

  • Endoneurium: surrounds each individual axon

  • Perineurium: groups of axons bundled into fascicles

  • Epineurium: the outermost layer that surrounds the entire nerve

Cranial Nerves I, II, X:

• I (Olfactory): responsible for the sense of smell

• II (Optic): responsible for vision

• X (Vagus): regulates functions of the heart, lungs, and digestive tract

Spinal Nerves:

• There are 31 pairs of spinal nerves

• Named based on the region of the spine they originate from: cervical, thoracic, lumbar, sacral, and coccygeal

Reflex Arc Steps:

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  1. Stimulus: a change in the environment

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  2. Receptor: detects the stimulus

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  3. Afferent Pathway: sensory neuron carries the signal to the CNS

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  4. Integration Center: within the CNS, the signal is processed

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  5. Efferent Pathway: motor neuron carries the command to the response target

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  6. Effector: muscle or gland that produces a response

Monosynaptic vs. Polysynaptic Reflexes:

• Monosynaptic Reflex: involves one synapse between the sensory and motor neuron (e.g., knee-jerk reflex/patellar reflex)

• Polysynaptic Reflex: involves one or more interneurons, allowing for more complex responses (e.g., withdrawal reflex)

Ipsilateral vs. Contralateral Reflexes:

• Ipsilateral Reflex: occurs on the same side of the body as the stimulus (e.g., direct knee-jerk)

• Contralateral Reflex: occurs on the opposite side of the body in response to a stimulus (e.g., stepping on a nail and pulling back the opposite leg)

Structure of the Eye:

• Parts include the cornea, pupil, lens, retina, and optic nerve. Understanding how these parts work together for vision is important for labeling a diagram.

How Hearing Works:

Basics of Taste and Smell: