Central and Peripheral Nervous System: Study Guide (Chapters 12-15)

Chapter 12: The Central Nervous System

Overview of the Central Nervous System (CNS)

The central nervous system (CNS) consists of the brain and spinal cord. It is responsible for integrating sensory information, coordinating motor output, and higher cognitive functions.

• Motor Function: Controls voluntary and involuntary movements.

• Sensory Function: Receives and processes sensory input from the body.

• Integrative Function: Analyzes and interprets sensory data, making decisions and generating responses.

Additional info: The CNS is protected by the skull and vertebral column, and surrounded by meninges and cerebrospinal fluid.

Divisions and Structures of the Brain

The brain is divided into several regions, each with specialized functions. The cerebrum is the largest part, divided into right and left hemispheres, and further into five lobes.

• Cerebrum: Responsible for higher brain functions such as thought, memory, and voluntary movement.

• Lobes of the Cerebrum: Frontal, parietal, temporal, occipital, and insula.

• Diencephalon: Includes the thalamus and hypothalamus; involved in sensory relay and homeostasis.

• Cerebellum: Coordinates movement and balance.

• Brainstem: Connects the brain to the spinal cord; controls vital functions.

Gray Matter vs. White Matter

The brain and spinal cord contain two types of tissue: gray matter and white matter.

• Gray Matter: Contains neuron cell bodies, dendrites, and synapses.

• White Matter: Composed of myelinated axons that transmit signals.

Major Brain Areas and Functions

• Cerebral Cortex: Responsible for conscious thought, perception, and voluntary movement.

• Special Sensory Areas: Include regions for vision, hearing, taste, smell, and touch.

• Multimodal Association Areas: Integrate information from multiple senses.

• Broca's Area: Involved in speech production (frontal lobe).

• Wernicke's Area: Involved in language comprehension (temporal lobe).

White Matter Tracts

• Commissural Fibers: Connect the two hemispheres (e.g., corpus callosum).

• Projection Fibers: Connect the cortex with lower brain regions and spinal cord.

• Association Fibers: Connect regions within the same hemisphere.

Limbic System

The limbic system is involved in emotion, motivation, and memory. Major components include the hippocampus, amygdala, and cingulate gyrus.

Thalamus and Hypothalamus

• Thalamus: Relay station for sensory information.

• Hypothalamus: Regulates homeostasis, including temperature, hunger, and autonomic functions.

Chapter 13: The Peripheral Nervous System

Overview of the Peripheral Nervous System (PNS)

The PNS connects the CNS to limbs and organs. It is divided into sensory (afferent) and motor (efferent) divisions.

• Sensory Division: Transmits sensory information to the CNS.

• Motor Division: Transmits motor commands from the CNS to muscles and glands.

Peripheral Nerves and Ganglia

• Spinal Nerves: Originate from the spinal cord; 31 pairs in total.

• Cranial Nerves: Originate from the brain; 12 pairs.

• Ganglia: Clusters of neuron cell bodies outside the CNS.

Connective Tissue Layers of Nerves

• Epineurium: Outermost layer surrounding the entire nerve.

• Perineurium: Surrounds bundles (fascicles) of axons.

• Endoneurium: Surrounds individual axons.

Sensory Receptors and Reflexes

• Mechanoreceptors: Detect mechanical stimuli (touch, pressure).

• Thermoreceptors: Detect temperature changes.

• Photoreceptors: Detect light (vision).

• Nociceptors: Detect pain.

• Proprioceptors: Detect body position and movement.

Reflex Arc: A neural pathway that controls a reflex action.

• Components: Receptor, sensory neuron, integration center, motor neuron, effector.

Chapter 14: The Autonomic Nervous System and Homeostasis

Overview of the Autonomic Nervous System (ANS)

The ANS regulates involuntary functions such as heart rate, digestion, and respiratory rate. It is divided into sympathetic and parasympathetic divisions.

• Sympathetic Division: Prepares the body for 'fight or flight' responses.

• Parasympathetic Division: Promotes 'rest and digest' activities.

ANS Pathways and Effects

• Visceral Reflex Arcs: Control involuntary organ functions.

• Sympathetic Effects: Increase heart rate, dilate pupils, inhibit digestion.

• Parasympathetic Effects: Decrease heart rate, constrict pupils, stimulate digestion.

Sympathetic vs. Parasympathetic Tone

• Sympathetic Tone: Dominates during stress or activity.

• Parasympathetic Tone: Dominates during rest.

Chapter 15: The General and Special Senses

Overview of Sensory Systems

The body has five special senses: vision, hearing, taste, smell, and equilibrium. Each sense has specialized receptors and pathways.

• Olfaction (Smell): Detected by chemoreceptors in the nasal cavity.

• Gustation (Taste): Detected by taste buds on the tongue.

• Vision: Detected by photoreceptors in the retina.

• Hearing: Detected by mechanoreceptors in the cochlea.

• Equilibrium: Detected by mechanoreceptors in the vestibular system.

Transduction and Receptor Types

• Transduction: The process by which sensory receptors convert stimuli into electrical signals.

• Receptor Types: Chemoreceptors, mechanoreceptors, photoreceptors, thermoreceptors, nociceptors.

Olfactory and Gustatory Pathways

• Olfactory Pathway: Olfactory nerve transmits signals to the olfactory bulb and then to the brain.

• Gustatory Pathway: Taste signals are transmitted via cranial nerves to the gustatory cortex.

Eye Anatomy

• Cornea: Transparent front part of the eye.

• Iris: Colored part of the eye; controls pupil size.

• Lens: Focuses light onto the retina.

• Retina: Contains photoreceptors for vision.

Key Tables

Table: Comparison of Nervous System Divisions

Division	Main Function	Key Structures
Central Nervous System (CNS)	Integration, processing, and response	Brain, spinal cord
Peripheral Nervous System (PNS)	Connects CNS to body	Cranial nerves, spinal nerves, ganglia
Autonomic Nervous System (ANS)	Involuntary control of organs	Sympathetic and parasympathetic nerves

Table: Types of Sensory Receptors

Receptor Type	Stimulus Detected	Example Location
Mechanoreceptor	Touch, pressure, vibration	Skin, ear
Thermoreceptor	Temperature	Skin
Photoreceptor	Light	Retina
Chemoreceptor	Chemicals (taste, smell)	Tongue, nose
Nociceptor	Pain	Throughout body

Key Equations

• Resting Membrane Potential: $V_m = V_{inside} - V_{outside}$

• Ohm's Law (for neural conduction): $I = V / R$

• Nernst Equation (for ion equilibrium): $E_{ion} = \frac{RT}{zF} \ln \frac{[ion]_{outside}}{[ion]_{inside}}$

Additional info: These notes expand on the study guide by providing definitions, examples, and context for each major topic. Refer to your textbook and lecture slides for diagrams and further details.