A&P 1 Exam 4

What are the four main regions of the spinal cord, and what key anatomical features do they include?

What are the four main regions of the spinal cord, and what key anatomical features do they include?

• Cervical (C1-C8): Cervical spinal nerves, cervical enlargement. (neck)

• Thoracic (T1-T12): Thoracic spinal nerves, posterior median sulcus. (chest)

• Lumbar (L1-L5): Lumbar spinal nerves, lumbar enlargement. (lower back)

• Sacral (S1-S5): Sacral spinal nerves, conus medullaris, cauda equina, coccygeal nerve. (sacrum/tail bone)

do not need to know numbers*

What are dermatomes, and how are they organized along the spinal cord?

Dermatomes are areas of skin innervated by specific spinal nerves. *

• Cervical (C1-C8): Innervates arms, neck, and back of the head.

• Thoracic (T1-T12): Covers the chest and abdomen.

• Lumbar (L1-L5): Provides sensation to the lower back and front of the legs.

• Sacral (S1-S5): Innervates the back of the legs, buttocks, and groin area.

  Spinal cord talks to entire body. Chicken pox virus sleeps in spinal cord, thoracic mostly, wakes up shingles in T3, wraps around dermatome

What are the major nerves of the cervical and brachial plexuses, and what areas do they innervate?

• Cervical Plexus (C1-C5): Innervates muscles of the neck, head, and diaphragm. Major nerves: Lesser occipital, Great auricular, Transverse cervical, Supraclavicular, Phrenic.

• Brachial Plexus (C5-T1): Innervates pectoral girdles and upper limbs, talks to arm. Major nerves: Axillary, Musculocutaneous, Radial, Ulnar, Median.

These nerves are crucial for controlling movements and sensation in the neck, diaphragm, and upper limbs. Plexus is a region of nerves that go to same area.

What are the major nerves of the lumbar and sacral plexuses, and what areas do they innervate?

• Lumbar Plexus (T12-L4): Innervates pelvic girdle and lower limbs. Major nerves: Iliohypogastric, Ilio-inguinal, Genitofemoral, Femoral, Obturator, Lateral femoral cutaneous, and Saphenous.

• Sacral Plexus (L4-S4): Innervates the gluteal region and lower limbs. Major nerves: Superior/Inferior Gluteal, Pudendal, Sciatic (longest)

These nerves control movement and sensation in the pelvic area and legs.

What are the three meningeal layers of the spinal cord, and what are their functions?

• Dura Mater: The outermost layer providing strong protection for the spinal cord.

• Arachnoid Mater: The middle layer, filled with cerebrospinal fluid to cushion the spinal cord.

• Pia Mater: The innermost layer, closely adhering to the spinal cord and nourishing it.

Additionally, the image shows gray and white matter, along with the dorsal and ventral roots, which are essential for nerve signal transmission.

What are the key structures in a spinal cord cross-section?

• Vertebral Body - Provides structural support for the spine.

• Spinal Cord - Contains nerve fibers that transmit signals between the brain and the body.

• Meninges - Protective layers around the spinal cord, epidural, including:

  • Dura Mater

  • Arachnoid Mater (spinal tap)

  • Pia Mater (closest to neurons and nerves)

• Subarachnoid Space - Contains cerebrospinal fluid (CSF) that cushions the spinal cord.

• Epidural Space - Contains adipose tissue, providing additional cushioning.

• Dorsal Root Ganglion - Contains sensory neuron cell bodies.

• Ventral Root of Spinal Nerve - Carries motor signals from the spinal cord to the body.

• Dorsal Ramus - Supplies nerves to the back muscles and skin.

• Ventral Ramus - Supplies nerves to the front and side of the body and limbs.

• Rami Communicantes - Connect the spinal nerves to the autonomic nervous system.

• Autonomic (Sympathetic) Ganglion - Part of the sympathetic nervous system, involved in "fight or flight" responses.

• Dentate Ligament - Stabilizes the spinal cord within the vertebral column.

• What are the main regions and functional groups in the cross-sectional anatomy of the spinal cord?

• Regions of Gray Matter:

  • Posterior Gray Horn: Contains sensory nuclei (receives somatic and visceral sensory input).

  • Lateral Gray Horn: Present only in thoracic and lumbar segments; contains visceral motor nuclei.

  • Anterior Gray Horn: Contains motor nuclei for somatic motor control.

• Regions of White Matter:

  • Posterior White Column: Carries ascending sensory information to the brain.

  • Lateral White Column: Contains both ascending sensory and descending motor tracts.

  • Anterior White Column: Carries both motor and sensory tracts, including those that control posture.

• Additional Structures:

  • Dorsal Root Ganglion: Contains cell bodies of sensory neurons.

  • Ventral Root: Contains axons of motor neurons.

  • Anterior and Posterior Gray Commissures: Connects the two sides of the gray matter.

  • Anterior Median Fissure: A groove along the anterior (front) side of the spinal cord.

  • Posterior Median Sulcus: A groove along the posterior (back) side of the spinal cord.

• How does a spinal nerve collect and deliver sensory information to the spinal cord?

• Sensory Pathways:

  • 1. Sympathetic Nerve: Carries sensory information from visceral organs.

  • 2. Anterior Ramus: Carries sensory information from the ventrolateral body surface, body wall structures, and limbs.

  • 3. Posterior Ramus: Carries sensory information from the skin and skeletal muscles of the back.

  • 4. Posterior Root of Each Spinal Nerve: Transmits sensory information directly to the spinal cord's sensory nuclei.

• Types of Sensations:

  • Somatic Sensations (Orange): From exteroceptors and proprioceptors, related to body surface and limbs.

  • Visceral Sensations (Purple): From interoceptors within visceral organs and the body wall.

• How does a spinal nerve distribute motor commands to different parts of the body?

• Motor Pathways:

  • 1. Anterior Root: Contains axons of somatic and visceral motor neurons originating from motor nuclei in the spinal cord.

  • 2. Spinal Nerve Formation: Spinal nerves form just lateral to the intervertebral foramen, where the anterior and posterior roots unite.

  • 3. Posterior Ramus: Carries somatic and visceral motor fibers to the skin and skeletal muscles of the back.

  • 4. Anterior Ramus: Supplies the ventrolateral body surface, structures in the body wall, and the limbs with motor commands.

  • 5. Sympathetic Ganglion: Contains preganglionic and postganglionic fibers involved in the autonomic (sympathetic) nervous system.

• Rami Communicantes:

  • White Ramus Communicans: Carries preganglionic visceral motor fibers to sympathetic ganglia (only present in T1-L2 regions).

  • Gray Ramus Communicans: Carries postganglionic fibers to glands, smooth muscles, and adipose tissue, associated with each spinal nerve.

• Types of Motor Commands:

  • Somatic Motor Commands (Pink): Control skeletal muscles.

  • Visceral Motor Commands (Blue): Control smooth muscles, glands, and internal organs.

• What are the five processing patterns of interneurons in neural circuits?

• Divergence: A single neuron sends information to multiple neurons, amplifying the signal.

• Convergence: Multiple neurons send information to a single neuron, allowing for summation of inputs.

• Serial Processing: Information is relayed in a sequential, step-by-step manner from one neuron to another.

• Parallel Processing: Information is processed simultaneously along multiple pathways.

• Reverberation: Neurons form a feedback loop, which can maintain a signal within the circuit for extended processing or rhythmic activity.

• What are divergence and convergence in neural processing, and can you provide an example of each?

• Divergence:

  • Definition: A neural circuit that spreads stimulation to multiple neurons or neuronal pools in the CNS.

  • Function: Amplifies the signal, allowing a single neuron to influence multiple neurons.

  • Example: When sensory information from the eyes is transmitted to various brain regions, such as those for visual processing, attention, and coordination, enabling multiple areas to process visual input simultaneously.

• Convergence:

  • Definition: A neural circuit that provides input to a single neuron from multiple sources.

  • Function: Allows for summation of inputs, enabling the neuron to integrate information from various sources.

  • Example: Motor neurons receive converging inputs from multiple sources, such as different parts of the brain and spinal cord, which helps coordinate complex movements by integrating signals from various regions.

• What are serial processing, parallel processing, and reverberation in neural circuits? Provide an example of each.

• Serial Processing:

  • Definition: A neural circuit where neurons or pools work sequentially, processing information step-by-step.

  • Example: Reflex arcs, like the knee-jerk reflex, where a sensory neuron activates a motor neuron in a straightforward sequence.

• Parallel Processing:

  • Definition: A neural circuit in which neurons or pools process the same information simultaneously along multiple pathways.

  • Example: When you step on something sharp, your brain processes the sensation of pain, initiates a withdrawal reflex, and activates a vocal response (“ouch!”) simultaneously in different pathways.

• Reverberation:

  • Definition: A positive feedback loop in a neural circuit that re-stimulates the circuit, maintaining activity.

  • Example: Breathing rhythm is maintained by reverberating circuits in the brainstem, which help keep the respiratory cycle ongoing without conscious effort.

Review Questions:

1. Which root receives sensory information?

   • a) Dorsal/Posterior

   • b) Ventral/Anterior

2. Which root sends out motor information?

   • a) Dorsal/Posterior

   • b) Ventral/Anterior

3. Shingles is a viral disease in which the chickenpox virus remains dormant in one region of the spinal cord. When activated, it causes painful rashes. Where would you expect to find the rashes?

4. Why would grasping my ring and pinky finger help after striking my "funny bone" on a table?

5. What are the four regions of the brain?

• a) Dorsal/Posterior – The dorsal (posterior) root receives sensory information.

• b) Ventral/Anterior – The ventral (anterior) root sends out motor information.

• Rashes would appear in the dermatomes corresponding to the affected spinal nerve region, as shingles typically follows the path of the infected sensory nerves in the skin. (usually T3-T5)

• Grasping the ring and pinky finger can help relieve "funny bone" pain because striking the "funny bone" compresses the ulnar nerve, which supplies sensation to these fingers. Holding them can stimulate the nerve and counteract the tingling or pain sensation by providing competing sensory input, helping to reduce discomfort.

• Frontal, Parietal, Occipital, Temporal

Identify the function of each brain region: Cerebrum, Diencephalon (Thalamus and Hypothalamus), Midbrain, Pons, Medulla Oblongata, and Cerebellum.

• Cerebrum: Conscious thought processes, intellectual functions, memory storage and processing, regulation of skeletal muscle contractions. Complex motion and sensory

• Diencephalon:

  • Thalamus: Relay and processing center for sensory information.

  • Hypothalamus: Controls emotions, autonomic functions, and hormone production.

• Midbrain: Processes visual and auditory data, generates reflexive somatic motor responses, maintains consciousness.

• Pons: Relays sensory information to cerebellum and thalamus, regulates subconscious somatic and visceral motor centers.

• Medulla Oblongata: Relays sensory information to the thalamus, contains autonomic centers for regulating visceral functions.

• Cerebellum: Coordinates complex motor coordination, adjusts somatic motor centers in the brain and spinal cord.

• Brain stem: most primitive region, works to keep us alive.

What are the primary and secondary brain vesicles, their corresponding brain regions at birth, and associated ventricles?

Primary Brain Vesicles (3 weeks):

• Prosencephalon

  • Secondary Vesicles (6 weeks): Telencephalon and Diencephalon

  • Brain Regions at Birth: Cerebrum (Telencephalon), Diencephalon

  • Ventricles: Lateral ventricle (Telencephalon), Third ventricle (Diencephalon)

• Mesencephalon

  • Secondary Vesicle: Mesencephalon

  • Brain Region at Birth: Midbrain

  • Ventricle: Cerebral aqueduct

• Rhombencephalon

  • Secondary Vesicles: Metencephalon and Myelencephalon

  • Brain Regions at Birth: Cerebellum and Pons (Metencephalon), Medulla oblongata (Myelencephalon)

  • Ventricle: Fourth ventricle

What are the main functions of cerebrospinal fluid (CSF), its composition, and what cells produce it?

• Main Functions of CSF:

  • Supporting the brain

  • Cushioning delicate neural structures

  • Transporting nutrients, chemical messengers, and wastes

• Composition: Perfect for neurons

• Produced by: Ependymal cells

What are the key characteristics of the Blood Brain Barrier (BBB) and the Blood-CSF Barrier?

• Blood Brain Barrier (BBB):

  • Prevents large molecules from passing into brain tissue

  • Allows only small molecules to pass through

  • Comprised of tightly connected endothelial cells

  • Astrocytes in tight capillaries

• Blood-CSF Barrier:

  • Formed by choroid cells with tight junctions

  • Has fenestrations in endothelium for selective transport

  • Separates blood from cerebrospinal fluid (CSF), maintaining the environment for neural activity

What factors are considered when developing a drug to cross the Blood Brain Barrier (BBB)?

Factors to Consider:

• Size of the Molecule: Smaller molecules are more likely to pass through the BBB.

• Hydrophobicity: Molecules with higher hydrophobicity are more likely to penetrate the BBB.

• Molecular Similarity: The drug should resemble molecules that naturally cross the BBB to increase its chances of passing through.

What are the steps involved in a reflex arc?

• Arrival of Stimulus and Activation of Receptor – A stimulus activates a receptor.

• Activation of a Sensory Neuron – The receptor stimulates a sensory neuron, sending a signal through the dorsal root.

• Information Processing in the CNS – The CNS processes the sensory information.

• Activation of a Motor Neuron – A motor neuron is activated in response.

• Response by Effector – The effector (e.g., muscle) responds, completing the reflex action.

most reflexes are in spinal cord, some in brain stem. knee jerk response goes straight to the spinal cord

How can reflexes be classified based on development, response, complexity of circuit, and processing site?

• Development:

  • Innate Reflexes: Genetically determined

  • Acquired Reflexes: Learned

• Response:

  • Somatic Reflexes: Control skeletal muscle contractions, include superficial and stretch reflexes

  • Visceral (Autonomic) Reflexes: Control actions of smooth and cardiac muscles, glands, and adipose tissue

• Complexity of Circuit:

  • Monosynaptic: One synapse

  • Polysynaptic: Multiple synapses (two to several hundred)

• Processing Site:

  • Spinal Reflexes: Processed in the spinal cord

  • Cranial Reflexes: Processed in the brain