nervous system google gemini

What are the two main anatomical divisions of the nervous system, their physical components, and their primary overall roles?

 Central Nervous System (CNS): Consists of the brain and spinal cord. Acts as the integration and control center that integrates sensory information.

Peripheral Nervous System (PNS): Consists of all nervous tissue outside the CNS (nerves and ganglia). Sends information to and from the CNS, allowing it to communicate with the rest of the body.

What are Afferent vs. Efferent neurons in the PNS?

 Afferent (Sensory) Neurons: Transmit impulses from sensory receptors to the CNS.

Efferent (Motor) Neurons: Transmit impulses from the CNS to effectors (muscles and glands).

What are the two functional subdivisions of the PNS and how do their neuronal pathways to target tissues differ?

 Somatic Nervous System (SNS): Controls voluntary movements (e.g., contraction of skeletal muscles).

• Pathway: Somatic motor neurons run directly from the CNS to the effector without synapsing in between.

• Autonomic Nervous System (ANS): Controls involuntary movements (e.g., smooth muscle, cardiac muscle, and glandular secretions).

  • Pathway: Uses a two-neuron pathway: a preganglionic neuron (runs from CNS to a ganglion) and a postganglionic neuron (runs from ganglion to target tissue).

Compare the Sympathetic and Parasympathetic divisions of the ANS regarding function, neurotransmitters, and physiological actions.

Sympathetic Division ("Fight or Flight"): Mobilizes body during activity, stress, or emergencies.

• Neurotransmitters: Preganglionic releases ACh; Postganglionic releases Norepinephrine (NE) onto targets.

• Physiological Effects: Increases heart rate & respiration; dilates pupils & bronchial tubes; increases blood flow to skeletal muscle/heart; suppresses digestion; breaks down glycogen.

• Parasympathetic Division ("Rest & Digest"): Conserves energy & maintains body during rest.

  • Neurotransmitters: Preganglionic releases ACh; Postganglionic releases ACh onto targets.

  • Physiological Effects: Decreases heart rate & respiration; constricts pupils & bronchial tubes; directs blood to digestive tract; promotes digestion & peristalsis; synthesizes glycogen.

 List the 5 classifications of sensory receptors by STIMULUS TYPE and provide specific examples for each.

• Mechanoreceptors: Detect mechanical deformation, pressure, tension, stretch, or vibration.

• Cutaneous: Meissner's corpuscles, Merkel's disks, Pacinian corpuscles, Ruffini endings.

• Internal: Muscle spindles (stretch), hair cells in inner ear (sound/balance).

• Chemoreceptors: Detect chemicals in solution (e.g., taste buds, olfactory receptors).

• Photoreceptors: Detect light energy (e.g., rods and cones in retina).

• Thermoreceptors: Sense absolute temperature and temperature changes.

• Nociceptors: Sense pain and tissue damage.

 Classify sensory receptors by LOCATION and by MORPHOLOGY.

 * By Location:

• Exteroceptors: Near body surface; detect external environment stimuli.

• Proprioceptors: In muscles, tendons, joints, inner ear; sense body position, movement, and equilibrium.

• Interoceptors: In visceral organs and blood vessels; monitor internal stimuli.

• By Morphology:

  • Free Nerve Endings: Unencapsulated dendrites.

  • Encapsulated Nerve Endings: Dendrites enclosed in connective tissue capsules.

Define sensory adaptation and contrast Phasic vs. Tonic receptors with examples.

 Sensory Adaptation: Change in sensitivity during prolonged exposure to a constant stimulus.

• Phasic Receptors (Fast-adapting): Fire rapidly at first, then action potentials decrease and stop even if stimulus continues.

  • Examples: Tactile receptors (clothing on skin), chemoreceptors (smell).

• Tonic Receptors (Slow-adapting): Adapt slowly; fire continuous action potentials for the duration of the stimulus.

  • Examples: Proprioceptors, photoreceptors, nociceptors (pain).

Describe the structure and lobes of the Cerebrum and their exact functions.

Covered by the cerebral cortex (thin outer layer of grey matter). Divided into two hemispheres and 4 main lobes:

• Frontal Lobe: Short-term memory, working memory, information processing, decision-making, planning, judgment.

• Parietal Lobe: Sensory input processing and spatial body positioning.

• Occipital Lobe: Visual input, visual processing, and visual output (optic nerves enter directly here).

• Temporal Lobes (Left & Right): Auditory input, processing, and output.

 What are the functions of the Forebrain, Hindbrain, Cerebellum, and Brain Stem?

* Forebrain: Includes cerebrum, thalamus, and hypothalamus.

• Hindbrain: Includes medulla oblongata, cerebellum, and pons.

• Cerebellum: Stores/processes implicit memories ( formed during classical conditioning) and automatic habits.

• Brain Stem: Connects brain to spinal cord; controls vital respiratory, digestive, and circulatory functions.

 Describe the 3 specific parts of the Brain Stem and their individual functions.

1. Midbrain: Lies above pons/medulla; includes tectum, tegmentum, and ventral tegmentum. Integrates visual and auditory signals.

2. Pons: Lies between midbrain and medulla; bridges/relays signals from cerebrum to medulla and cerebellum.

3. Medulla Oblongata: Connects directly to spinal cord; works with ANS to regulate heart rate, breathing, and blood circulation.

Describe the Cranial Cavity, the 3 Meningeal layers, and the Subarachnoid Space.

 * Cranial Cavity: Formed by cranial bones; houses brain, 12 cranial nerves, and pituitary gland.

• Dura Mater: Outer vascular/innervated layer attached to cranial bones. Has two layers:

  • Endosteal Layer: Lines cranial bones.

  • Meningeal Layer: Lines vertebral cavity below endosteal layer.

• Arachnoid Mater: Middle web-like connective tissue; no nerves or blood vessels.

• Subarachnoid Space: Below arachnoid mater; contains Cerebrospinal Fluid (CSF) which cushions the dorsal cavity.

• Pia Mater: Delicate, highly vascular inner layer directly attached to brain and spinal cord tissue.

List Cranial Nerves I through XII: Name, Type (Sensory/Motor/Both), and Function.

 * CN I (Olfactory): Sensory | Smell

• CN II (Optic): Sensory | Vision

• CN III (Oculomotor): Motor | Eye movement (up, down, left, right, diagonal), pupil constriction, lens accommodation

• CN IV (Trochlear): Motor | Eye movement

• CN V (Trigeminal): Both | Facial sensation, chewing

• CN VI (Abducens): Motor | Eye movement

• * CN VII (Facial): Both | Facial expressions, taste

  • CN VIII (Vestibulocochlear): Sensory | Hearing and balance

  • CN IX (Glossopharyngeal): Both | Taste, swallowing

  • CN X (Vagus): Both | Parasympathetic control of heart, lungs, and GI tract

  • CN XI (Accessory): Motor | Swallowing, head and neck movement

  • CN XII (Hypoglossal): Motor | Speech, swallowing, tongue muscles

What are the standard memory mnemonics for the Cranial Nerve NAMES and TYPES? 

• Names: Oh, Once One Takes The Anatomy Final, Very Good Vacations Are Heavenly.

• Types (Sensory/Motor/Both): Some Say My Mother Bought My Brother Some Bad Beer, My, My.

 Describe the anatomical structure of the spinal cord (regions, white vs. grey matter, roots).

* 5 Regions: Cervical, Thoracic, Lumbar, Sacral, Coccyx.

• White Matter (Outer): Myelinated axon tracts running to/from brain; no cell bodies or dendrites.

• Grey Matter (Inner Core): Contains interneurons, motor neurons, unmyelinated axons.

  • Dorsal Root Ganglion: Outside spinal cord; holds cell bodies of sensory neurons.

  • Posterior/Dorsal Root: Where sensory (afferent) fibers enter.

  • Anterior/Ventral Root: Where motor (efferent) fibers exit.

 What is a Reflex Arc? Detail its 5 components, Monosynaptic vs. Polysynaptic types, and Supraspinal Circuits.

* Definition: Involuntary, instantaneous response bypassing conscious thought.

• 5 Components:
  Receptor→Sensory Neuron→Integration Center (Interneuron)→Motor Neuron→Effector

• Monosynaptic Reflex: Single direct synapse between sensory and motor neuron (e.g., patellar knee-jerk).

• Polysynaptic Reflex: Involves one or more interneurons.

• Supraspinal Circuits: Reflexes requiring brain/brainstem input (e.g., blinking, gagging; brain can override reflexes).

 Explain Negative vs. Positive Feedback loops with specific physiological examples.

* Negative Feedback: Reverses a deviation to restore homeostasis.

• Example (Thermoregulation): Hypothalamus senses temp change. High temp → sweating/vasodilation; Low temp → shivering/vasoconstriction.

• Positive Feedback: Amplifies a response until an endpoint is reached.

  • Example (Childbirth): Cervical stretch → signals pituitary → oxytocin release → increases contractions →stretches cervix more until birth.

Explain Neuroendocrine Integration between the Hypothalamus and Pituitary Gland

* Hypothalamic axons extend through the infundibulum into the posterior pituitary.

• Oxytocin and ADH are synthesized in the hypothalamus, then stored and secreted by the posterior pituitary.

• Hypothalamus also secretes releasing hormones regulating the anterior pituitary.

 Detail the structure of a neuron: Soma, Dendrites, Axon, Axoplasm, and Organelles present/absent.

* Soma: Nucleus, mitochondria, organelles, and Nissl bodies (rough ER/ribosomes for protein synthesis). Lacks centrioles (mature neurons cannot divide).

• Dendrites: Short, branching extensions receiving signals; contain dendritic spines. Contains soma organelles except nucleus.

• Axon: Long cable originating at axon hillock. Ends in terminals with neurotransmitter vesicles.

• Axoplasm: Cytoplasm of axon; lacks Golgi bodies, Nissl bodies, and ribosomes (proteins imported from soma).

Describe the 4 structural classifications of neurons.

1. Unipolar Neurons: Single process extending from soma.

2. Bipolar Neurons: Two processes (one axon, one dendrite); rare (found in retina and inner ear).

3. Multipolar Neurons: Multiple dendrites and one axon; most common type (interneurons & motor neurons).

4. Pseudounipolar Neurons: Functional sensory neurons with a single split process.

 Describe Myelin Sheaths, Nodes of Ranvier, Saltatory Propagation, and Conduction Speeds.

* PNS Myelination: Schwann cells wrap axons; outer layer forms neurilemma. Unmyelinated small axons supported by non-myelinating Schwann cells.

• CNS Myelination: Formed by Oligodendrocytes (one cell myelinates multiple axons).

• Nodes of Ranvier: ~1 µm gaps with high density of Na+/K+ channels where action potentials jump via saltatory propagation.

• Speeds: Large myelinated (80–120 m/s) vs. thin unmyelinated (0.5–10 m/s).

• Note: Myelinated axons have less neuroplasticity. Demyelinating diseases: Multiple sclerosis & leukodystrophies.

 List the 4 Glial Cells of the CNS and their exact functions.

: 1. Astrocytes: Most abundant anchor neurons, maintain blood-brain barrier, facilitate capillary exchange, uptake excess ions and neurotransmitters. found in neural tissue

2. Microglia: Phagocytic immune cells that digest cellular debris and pathogens.

3. Oligodendrocytes: Produce myelin sheaths around CNS axons.

4. Ependymal Cells: form epithelial lining of ventricles and central canal of the spinal cord; produce and circulate cerebrospinal fluid exchange material between CSF and interstitial fluid of brain and spinal cord

List the 2 Glial Cells of the PNS and their exact functions.

1. Schwann Cells: Form myelin sheaths around individual PNS axons; speed up impulse transmission.

2. Satellite Cells: Surround, cushion, and protect cell bodies in PNS ganglia.

Classify Synapses by Target Location and by Mode of Transmission.

• Axodendritic: Axon to dendrite.

• Axosomatic: Axon to cell body.

• Axoaxonic: Axon to another axon (rare).

• By Transmission Mode:

  • Chemical Synapses: Unidirectional; use neurotransmitters. Can be excitatory or inhibitory.

  • Electrical Synapses: Linked by gap junctions allowing direct ion flow. Faster, bidirectional, always excitatory, but rarer.

 Detail the 5 steps of Chemical Synaptic Transmission.

1. Action potential reaches axon terminal, depolarizing the membrane.

2. Voltage-gated Ca2+ (calcium) channels open, causing calcium influx.

3. Calcium influx triggers exocytosis of neurotransmitter vesicles into the synaptic cleft.

4. Neurotransmitters diffuse across cleft and bind to receptors on the postsynaptic membrane.

5. Signal is stopped as neurotransmitters are recycled back, enzymatically degraded, or diffuse away.

State the specific actions and primary functions of Acetylcholine (ACh), Norepinephrine (NE), and Dopamine.

* Acetylcholine (ACh): Stimulates skeletal muscle contraction; primary postganglionic neurotransmitter for the parasympathetic system.

• Norepinephrine (NE): Primary postganglionic neurotransmitter for the sympathetic system; influences mood and sleep patterns.

• Dopamine: Associated with mood, attention, reward system, and voluntary motor control.

State the specific actions and primary functions of Histamine, Serotonin, GABA, and Glutamate.

* Histamine: Works with the hypothalamus to promote wakefulness.

• Serotonin: Mostly inhibitory; regulates sleep, mood, hunger, and arousal.

• GABA: The major inhibitory neurotransmitter in the CNS.

• Glutamate: The major excitatory neurotransmitter in the CNS.