BIO 163 Exam 3 Study Guide: Nervous System and Special Senses

Chapter 7: The Nervous System

Three Overlapping Functions of the Nervous System

The nervous system is responsible for integrating and coordinating the body's activities through three main functions:

• Sensory Input: Gathering information from internal and external environments via sensory receptors.

• Integration: Processing and interpreting sensory input to determine an appropriate response.

• Motor Output: Activating effector organs (muscles or glands) to produce a response.

Organization of the Nervous System

The nervous system is divided into structural and functional subdivisions:

• Central Nervous System (CNS): Consists of the brain and spinal cord; responsible for integration and command.

• Peripheral Nervous System (PNS): Composed of nerves and ganglia outside the CNS; connects the CNS to the rest of the body.

Functional Classification of the PNS

• Sensory (Afferent) Division: Transmits impulses from sensory receptors to the CNS.

• Motor (Efferent) Division: Transmits impulses from the CNS to effector organs.

  • Somatic Nervous System: Controls voluntary movements of skeletal muscles.

  • Autonomic Nervous System: Regulates involuntary functions (e.g., heart rate, digestion).

Neuroglia Cells and Their Functions

Neuroglia (glial cells) support and protect neurons. Their functions vary by location:

• CNS Neuroglia:

  • Astrocytes: Maintain blood-brain barrier, regulate nutrients, and support neurons.

  • Microglial Cells: Act as phagocytes, removing debris and pathogens.

  • Ependymal Cells: Line ventricles, produce and circulate cerebrospinal fluid (CSF).

  • Oligodendrocytes: Form myelin sheath around CNS axons.

• PNS Neuroglia:

  • Satellite Cells: Surround neuron cell bodies in ganglia, regulate environment.

  • Schwann Cells: Form myelin sheath around PNS axons.

Myelin Sheath

• Function: Insulates axons, increases speed of impulse conduction.

• Cells Forming Myelin: Schwann cells (PNS), oligodendrocytes (CNS).

• Nodes of Ranvier: Gaps in myelin sheath; facilitate rapid impulse transmission via saltatory conduction.

• Impulse Speed: Myelinated axons conduct impulses faster than unmyelinated axons.

Structure and Function of Neurons

• Dendrites: Receive signals from other neurons.

• Axon: Transmits electrical impulses away from cell body.

• Axon Hillock: Region where action potentials are initiated.

• Axon Terminal: Releases neurotransmitters into synaptic cleft.

• Synaptic Cleft: Gap between neurons where neurotransmitters act.

• Neurotransmitters: Chemical messengers facilitating communication between neurons.

Multiple Sclerosis

• Cause: Autoimmune destruction of myelin sheath in CNS.

• Effect: Impaired nerve conduction, leading to muscle weakness and other symptoms.

Key Terms

• Ganglia: Clusters of neuron cell bodies in the PNS.

• Nuclei: Clusters of neuron cell bodies in the CNS.

• Tracts: Bundles of axons in the CNS.

• Nerves: Bundles of axons in the PNS.

• White Matter: Myelinated axons.

• Gray Matter: Neuron cell bodies and unmyelinated fibers.

Classification of Neurons

• Functional: Sensory (afferent), motor (efferent), interneurons (association).

• Structural: Multipolar (many processes), bipolar (two processes), unipolar (one process).

Functional Properties of Nerve Cells

• Irritability: Ability to respond to stimuli.

• Conductivity: Ability to transmit impulses.

Action Potential Generation

Neurons generate electrical impulses through changes in membrane potential:

• Resting Membrane Potential: Polarized state; inside of neuron is negative relative to outside.

• Depolarization: Sodium ions ($\mathrm{Na^+}$) enter cell, making inside more positive.

• Action Potential: Rapid change in membrane potential; all-or-none response.

• Repolarization: Potassium ions ($\mathrm{K^+}$) exit cell, restoring negative charge inside.

• Neurotransmitter Release: Triggers graded potentials in postsynaptic neuron.

Order of Events:

1. Resting state (polarized)

2. Depolarization (influx of $\mathrm{Na^+}$)

3. Action potential generation

4. Repolarization (efflux of $\mathrm{K^+}$)

5. Return to resting state

All-or-None Response: An action potential either occurs fully or not at all.

Reflexes and Reflex Arcs

• Reflexes: Rapid, predictable, involuntary responses to stimuli.

• Somatic Reflexes: Involve skeletal muscles.

• Autonomic Reflexes: Involve smooth muscle, cardiac muscle, or glands.

Five Elements of Reflex Arc (in order):

1. Receptor

2. Sensory neuron

3. Integration center

4. Motor neuron

5. Effector

Adult Brain Structures

• Cerebral Hemisphere: Largest part; controls higher functions.

• Diencephalon: Contains thalamus, hypothalamus, epithalamus.

• Brain Stem: Includes midbrain, pons, medulla oblongata.

• Cerebellum: Coordinates movement and balance.

Lobes, Sulci, and Fissures of Cerebral Cortex

• Lobes: Frontal, parietal, temporal, occipital.

• Sulci: Shallow grooves.

• Fissures: Deep grooves separating major regions.

Functional Areas of Cerebral Cortex

• Motor Areas: Control voluntary movement; located in frontal lobe.

• Sensory Areas: Receive sensory input; located in parietal, occipital, temporal lobes.

• Association Areas: Integrate information; found throughout cortex.

• Damage Effects: Loss of function corresponding to area (e.g., motor, sensory, association).

Diencephalon Structures and Hypothalamus

• Thalamus: Relay station for sensory information.

• Hypothalamus: Maintains homeostasis; regulates temperature, hunger, thirst, endocrine functions.

• Epithalamus: Contains pineal gland; regulates sleep-wake cycles.

Brain Stem Structures and Functions

• Midbrain: Contains corpora quadrigemina (visual/auditory relay), cerebral peduncles (fiber tracts).

• Pons: Regulates respiratory rate.

• Medulla Oblongata: Controls cardiovascular, respiratory, vomiting centers.

• Reticular Activating System: Maintains alertness of cerebral cortex.

Cerebellum

• Function: Coordinates voluntary movements, balance, and posture.

• Location: Posterior to brain stem.

Meningeal Layers

• Dura Mater: Outermost, tough layer.

• Arachnoid Mater: Middle, web-like layer.

• Pia Mater: Innermost, delicate layer.

• Function: Protect CNS.

Cerebrospinal Fluid (CSF)

• Function: Cushions brain and spinal cord, removes waste.

• Flow: Produced by choroid plexus, circulates through ventricles (diencephalon, brain stem), subarachnoid space.

Blood Brain Barrier

• Function: Protects brain from harmful substances in blood.

Traumatic Brain Injuries

• Types: Concussion, contusion, cerebral edema.

Cerebrovascular Accidents (CVAs) and Transient Ischemic Attacks (TIAs)

• Causes: Blocked or ruptured blood vessels.

• Symptoms: Sudden loss of function, weakness, speech difficulties.

Spinal Cord Anatomy

• Gray Matter: Dorsal horn (sensory), ventral horn (motor).

• Dorsal Root Ganglion: Contains sensory neuron cell bodies.

• Connective Tissue Wrappings: Protect and organize nerve fibers.

• Damage Effects: Loss of motor or sensory function depending on area affected.

Cranial and Spinal Nerves

• Cranial Nerves: 12 pairs; functions include sensory, motor, and mixed.

• Spinal Nerves: 31 pairs; composed of dorsal (sensory) and ventral (motor) roots.

Spinal Nerve Plexuses

• Cervical: Phrenic nerve (serves diaphragm).

• Brachial: Axillary, ulnar, radial nerves (serves upper limb).

• Lumbar: Femoral nerve (serves thigh).

• Sacral: Sciatic nerve (serves lower limb).

• Thoracic: No plexus; intercostal nerves serve anterior trunk.

Somatic vs Autonomic Nervous Systems

• Somatic: Voluntary control of skeletal muscles.

• Autonomic: Involuntary control of smooth muscle, cardiac muscle, glands.

Parasympathetic vs Sympathetic Divisions

• Parasympathetic: "Rest and digest"; conserves energy.

• Sympathetic: "Fight or flight"; mobilizes body for action.

Developmental Disorders

• Cerebral Palsy: Motor impairment due to brain damage.

• Anencephaly: Absence of major brain parts.

• Spina Bifida: Incomplete closure of spinal cord.

Chapter 8: Special Senses

External Eye Anatomy

• Accessory Structures: Extrinsic eye muscles, eyelids, conjunctiva, lacrimal apparatus.

• Tarsal and Ciliary Glands: Lubricate eye and eyelids.

• Conjunctiva: Mucous membrane covering eye and inner eyelid.

• Lacrimal Apparatus: Produces tears; cleans and protects eye.

• Flow of Tears: From lacrimal gland to eye surface, drains via nasolacrimal duct.

Internal Eye Anatomy

• Three Layers:

  • Fibrous Layer: Sclera (white), cornea (transparent).

  • Vascular Layer: Choroid, ciliary body (ciliary zonule), iris (pupil).

  • Sensory Layer: Retina (pigmented and neural layers).

• Photoreceptors: Rods (dim light, peripheral vision), cones (color, sharp vision).

• Signal Pathway: Photoreceptors → bipolar cells → ganglion cells → optic nerve → visual cortex.

• Flow of Light: Cornea → aqueous humor → lens → vitreous humor → retina.

Optic Disc and Fovea Centralis

• Optic Disc: Blind spot; no photoreceptors.

• Fovea Centralis: Area of sharpest vision; high concentration of cones.

Lens and Eye Segments

• Lens: Focuses light on retina.

• Anterior Segment: Contains aqueous humor; nourishes lens and cornea.

• Posterior Segment: Contains vitreous humor; maintains eye shape.

Accommodation and Real Image

• Accommodation: Adjustment of lens shape for near/far vision.

• Real Image: Inverted image formed on retina.

Pupillary Reflexes

• Photopupillary Reflex: Pupil constricts in response to bright light.

• Accommodation Pupillary Reflex: Pupil constricts for near vision.

Pathway of Visual Information

• Light enters eye → photoreceptors → bipolar cells → ganglion cells → optic nerve → visual cortex.

Homeostatic Imbalances of Vision

• Night Blindness: Impaired rod function.

• Colorblindness: Deficiency in cone cells.

• Myopia: Nearsightedness; image focused in front of retina.

• Hyperopia: Farsightedness; image focused behind retina.

• Presbyopia: Age-related loss of accommodation.

• Cataracts: Clouding of lens.

• Glaucoma: Increased intraocular pressure; can damage optic nerve.

Ear Anatomy and Functions

• Outer Ear: Auricle, external auditory canal.

• Middle Ear: Tympanic membrane (separates outer/middle ear), ossicles (malleus, incus, stapes).

• Inner Ear: Vestibule, semicircular canals, cochlea.

• Ossicles: Transmit sound vibrations to inner ear.

Equilibrium and Hearing

• Maculae: Receptors for static equilibrium; otoliths help maintain position.

• Crista Ampullaris: Receptors for dynamic equilibrium; endolymph movement during rotation.

• Cochlea: Contains spiral organ; responsible for hearing.

Types of Deafness

• Conduction Deafness: Impaired transmission of sound to inner ear.

• Sensorineural Deafness: Damage to inner ear or auditory nerve.

• Meniere’s Disease: Inner ear disorder causing vertigo and hearing loss.

Olfactory and Gustatory Receptors

• Olfactory Receptors: Detect smell; located in nasal epithelium.

• Gustatory Cells: Taste receptors; found in taste buds on tongue papillae.

Types of Papillae

• Filiform: No taste buds; provide texture.

• Vallate: Large, contain taste buds.

• Fungiform: Mushroom-shaped, contain taste buds.

• Foliate: Lateral edges, contain taste buds.

Five Basic Taste Sensations

• Sweet

• Sour

• Salty

• Bitter

• Umami

Special Sense Development

• Vision: Only special sense not fully functional at birth.

Table: Cranial Nerves (Main Purpose)

Number	Name	Main Function
1	Olfactory	Smell
2	Optic	Vision
3	Oculomotor	Eye movement
4	Trochlear	Eye movement
5	Trigeminal	Facial sensation, chewing
6	Abducens	Eye movement
7	Facial	Facial expression, taste
8	Vestibulocochlear	Hearing, balance
9	Glossopharyngeal	Taste, swallowing
10	Vagus	Visceral sensation, parasympathetic control
11	Accessory	Neck muscles
12	Hypoglossal	Tongue movement

Additional info: Academic context and definitions were added to expand brief review points into a comprehensive study guide. Table of cranial nerves was inferred from standard content.