BIO 141 Lecture Exam 3 Study Guide: Nervous System Overview

Chapter 11 – Introduction to the Nervous System

Classification of the Nervous System

• Nervous System is divided into two major parts:

  • Central Nervous System (CNS): Consists of the brain and spinal cord. Responsible for integrating, processing, and coordinating sensory data and motor commands.

  • Peripheral Nervous System (PNS): Includes all neural tissue outside the CNS. Connects the CNS to limbs and organs.

Organs of the CNS and PNS

• CNS: Brain and spinal cord.

• PNS: Cranial nerves (arising from the brain) and spinal nerves (arising from the spinal cord).

Types of Nerves

• Cranial Nerves: 12 pairs; connect the brain to the head, neck, and trunk.

• Spinal Nerves: 31 pairs; connect the spinal cord to the rest of the body.

Characteristics of Neurons

• Excitable cells that transmit electrical signals.

• Long-lived, generally amitotic (do not divide after development), and have a high metabolic rate.

Major Parts of a Neuron and Their Functions

• Cell Body (Soma): Contains the nucleus and organelles; metabolic center.

• Dendrites: Receive incoming signals from other neurons.

• Axon: Conducts electrical impulses away from the cell body.

• Axon Terminals: Release neurotransmitters to communicate with other cells.

Major Parts of an Axon

• Axon Hillock: Initial segment where action potentials are generated.

• Axon Proper: Main conducting region.

• Axon Terminals (Synaptic Boutons): Endings that form synapses with other cells.

Function of Myelin Sheath

• Insulates axons, increasing the speed of nerve impulse conduction.

• Formed by Schwann cells in the PNS and oligodendrocytes in the CNS.

Myelinated vs. Unmyelinated Axons

• Myelinated Axons: Conduct impulses rapidly via saltatory conduction.

• Unmyelinated Axons: Conduct impulses more slowly via continuous conduction.

Gray Matter vs. White Matter in the Brain

• Gray Matter: Contains neuron cell bodies, dendrites, and unmyelinated axons; located on the surface (cortex) of the brain and in deeper nuclei.

• White Matter: Composed mainly of myelinated axons; found deeper within the brain.

Axon Diameter and Speed of Impulse Propagation

• Larger diameter axons conduct impulses faster due to lower resistance to ion flow.

Repair in CNS vs. PNS

• PNS: Some regeneration possible due to Schwann cells forming regeneration tubes.

• CNS: Limited repair; oligodendrocytes do not form regeneration tubes and inhibitory factors are present.

Chapter 12 – Central Nervous System (CNS)

Functions of the CNS

• Integrates sensory information, coordinates motor output, and is responsible for higher functions such as thought, memory, and emotion.

Major Parts of the Brain

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

• Diencephalon: Includes thalamus and hypothalamus; relays and processes sensory information, regulates autonomic functions.

• Brain Stem: Includes midbrain, pons, and medulla oblongata; controls basic life functions.

• Cerebellum: Coordinates movement and balance.

Protection of the CNS

• Bony Protection: Skull protects the brain; vertebral column protects the spinal cord.

• Meninges: Three connective tissue membranes (dura mater, arachnoid mater, pia mater) surround the CNS.

• Cerebrospinal Fluid (CSF): Cushions and nourishes the CNS.

Space Containing CSF

• Subarachnoid Space: Located between the arachnoid mater and pia mater; contains CSF.

Importance of Sufficient Blood Flow in the Brain

• Ensures delivery of oxygen and nutrients; lack of blood flow can cause irreversible brain damage.

Blood Brain Barrier

• A selective barrier formed by endothelial cells of brain capillaries; restricts passage of substances from blood to brain tissue.

Cerebrospinal Fluid (CSF)

• Definition: Clear, colorless fluid produced by the choroid plexus in the ventricles of the brain.

• Functions: Cushions the brain, removes waste, provides nutrients, and maintains chemical stability.

• Characteristics: Low protein, few cells, similar ionic composition to plasma.

Gyrus, Sulcus, and Fissure

• Gyrus (plural: Gyri): Elevated ridges on the cerebral surface.

• Sulcus (plural: Sulci): Shallow grooves between gyri.

• Fissure: Deep grooves that separate large regions of the brain.

Lobes of the Cerebrum

• Frontal, Parietal, Temporal, Occipital, and Insula (deep within the lateral sulcus).

Sensory, Motor, and Association Areas in the Cerebrum

• Sensory Areas: Receive and interpret sensory impulses.

• Motor Areas: Control voluntary movements.

• Association Areas: Integrate information for complex functions (e.g., reasoning, language).

Association Areas and Their Functions

• Prefrontal Cortex: Planning, decision-making, personality.

• Wernicke's Area: Language comprehension.

• Broca's Area: Speech production.

Major Parts of the Diencephalon and Their Functions

• Thalamus: Relay station for sensory information.

• Hypothalamus: Regulates autonomic and endocrine functions, homeostasis.

• Epithalamus: Contains the pineal gland (melatonin secretion).

Parts of the Brain Stem and Their Functions

• Midbrain: Visual and auditory reflexes.

• Pons: Relays information between cerebrum and cerebellum; regulates breathing.

• Medulla Oblongata: Controls vital functions (heart rate, blood pressure, respiration).

Functions and Major Parts of the Cerebellum

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

• Major Parts: Two hemispheres, vermis (central region), and arbor vitae (white matter).

Functions of the Spinal Cord

• Conducts sensory and motor information to and from the brain; mediates reflexes.

Sensory vs. Motor Tracts in the Spinal Cord

• Sensory (Ascending) Tracts: Carry sensory information to the brain.

• Motor (Descending) Tracts: Carry motor commands from the brain to the body.

Chapter 13 – Peripheral Nervous System (PNS)

Spinal Nerve Plexuses

• Cervical Plexus: Supplies neck and diaphragm.

• Brachial Plexus: Supplies shoulders and upper limbs.

• Lumbar Plexus: Supplies lower abdomen and anterior thigh.

• Sacral Plexus: Supplies posterior thigh, lower leg, and foot.

Reflex

• Definition: A rapid, automatic response to a stimulus.

• Example: Knee-jerk (patellar) reflex.

Cranial Nerves: Numbers, Names, Types, and Functions

Number	Name	Type	Function
I	Olfactory	Sensory	Smell
II	Optic	Sensory	Vision
III	Oculomotor	Motor	Eye movement, pupil constriction
IV	Trochlear	Motor	Eye movement
V	Trigeminal	Both	Facial sensation, chewing
VI	Abducens	Motor	Eye movement
VII	Facial	Both	Facial expression, taste
VIII	Vestibulocochlear	Sensory	Hearing, balance
IX	Glossopharyngeal	Both	Taste, swallowing
X	Vagus	Both	Viscera control, taste
XI	Accessory	Motor	Head and shoulder movement
XII	Hypoglossal	Motor	Tongue movement

Sensation vs. Perception

• Sensation: Awareness of changes in the internal or external environment.

• Perception: Interpretation of sensory information by the brain.

Touch and Pressure Receptors

• Meissner's Corpuscles: Detect light touch.

• Pacinian Corpuscles: Detect deep pressure and vibration.

• Merkel Discs: Detect sustained touch and pressure.

Referred Pain

• Definition: Pain perceived at a location other than the site of the painful stimulus, due to shared neural pathways.

• Example: Pain from a heart attack felt in the left arm.

Proprioception and Proprioceptors

• Proprioception: Sense of body position and movement.

• Proprioceptors: Located in muscles, tendons, and joints; provide information about limb position and movement.

Additional info: Academic context and definitions have been expanded for clarity and completeness. Table of cranial nerves included for reference.