BIO Ch 7 Nervous System

central, peripheral

What are the two divisions of the nervous system?

peripheral nervous system

Detection of stimuli & response to stimuli happen in which division of the nervous system?

central nervous system

Integration of information happens in which division of the nervous system?

brain, spinal cord

What makes up the central nervous system?

nervous tissue

What makes up the peripheral nervous system?

afferent neurons

Neurons that send signals towards CNS (sensory)

• a. Signal Initiation

  Sensory receptors initiate signals to the brain / spinal cord.

• b. Integration

  Sensory neurons in CNS perform integration (process of assessing sensory inputs and memories to determine output response).

efferent neurons

Neurons that send signals away from CNS (motor)

• Carries motor command signals away from the Central Nervous System (CNS) to target organs and effectors in the Peripheral Nervous System (PNS)

somatic, autonomic

What are the 2 divisions of the peripheral nervous system?

somatic nervous system

Nervous system that ontrols conscious perception & voluntary movement

• Somatosensory Neurons

  • Sensory signals from skin, joints, & muscles. Transmits information about external environment, orientation, & movement.

• Somatic Motor Neurons

  • Signals to skeletal muscles. Essential for voluntary movement and maintaining body posture.

autonomic nervous system

Nervous system that controls viscera; operates automatically

• Visceral Sensory Neurons

  • Carries internal sensory signals directly from viscera and internal organs to the central nervous system.

• Visceral Motor Neurons

  • Signals to cardiac muscles, smooth muscle, & glands. Regulates organ function and maintains homeostasis.

enteric nervous system

Intricate neural network embedded directly in the walls of gastrointestinal organs

neurons

Major functional cells of the nervous system responsible for detecting, processing, and transmitting signals

detect stimuli, integrate information, relay signals, initiate response

What are the 4 functions of neurons?

detect stimuli

Neuron function where sensory receptors respond to internal and external environmental changes

integrate information

Neuron function that processes and assesses incoming sensory inputs to determine appropriate response

relay signals

Neuron function that transmits electrical impulses rapidly across nerve pathways

initiate response

Neuron function that triggers target organ, muscle, or glandular activity

dendrites, axons, axon terminal

What are the three structures that make up a neuron?

dendrites

Cell body housing the nucleus. Includes the axon hillock where signal integration occurs

axon

Where dendrites and soma receive incoming signals and transmit action potentials along the axon length

axon terminal

Terminal projections where neurotransmitters are stored and released across synapses

neuroglia

Supporting cells of neurons (glial cells)

• CNS

  • astrocytes, microglia, ependymal, oligodendrocytes

• PNS

  • satellite

  • schwann

astrocytes

Type of neuroglia in the CNS

• Blood Brain Barrier: Aid in its development

• Ion Balance: Act as a potassium buffer

• Cleanup: Remove excess neurotransmitters

microglia

Type of neuroglia in the CNS

• Immune Response: Replicate during infection or tissue inflammation

• Phagocytosis: Remove cellular debris and harmful pathogens

ependymal

Type of neuroglia in the CNS

• CSF Production: Actively produce cerebrospinal fluid

• Homeostasis: Exchange nutrients and waste to maintain CSF balance

oligodendrocytes

Type of neuroglia in the CNS

• Myelin Sheath: Form insulating covers around axons to accelerate nervous signals

• Can myelinate axons of multiple neurons simultaneously

satellite cells

Type of neuroglia in the PNS

• Nourishment & Support: Provides vital support and nutrient supply (similar to astrocytes)

• Cell Body Coverage: Encloses and protects neuron cell bodies in the PNS

schwann cells

Type of neuroglia in the PNS

• Terminology: Also known as neurolemmocytes

• Myelination: Wraps around peripheral neuron axons to form insulating myelin sheaths

• Often just myelinates a small part of a single axon

oligodendrocytes, schwann cells

What two cellular types contribute to myelination?

insulation effect

What allows neural signals to be transmitted significantly faster during myelination

nodes of ranvier

Gaps along non-continuous myelin sheaths where plasma membrane is exposed

unmyelinated axon

Glial cells may still cover parts of the axon, but lack sufficient layers for insulation

rest & activation, graded potentials, action potential

What are the three components of graded membrane potentials?

rest & activation

Baseline state of a graded membrane potential

• Resting Potential: Neurons at rest are polarized around -70mV

• Channel Opening: Ligand-gated Na+ channels in dendrites and soma are stimulated to open

• Local Effect: Membrane depolarizes near the opened gates

graded potentials

Stimulation response to a graded membrane potential

• Variable Magnitude: Depolarize a little or a lot depending on gate count & stimulation frequency

• Threshold Level: Sufficient strength depolarizes membrane beyond threshold level

action potential

Action trigger of a graded membrane potential

• Na+ Influx: Voltage-gated Na+ channels open, creating an action potential in the axon hillock

• All-or-Nothing: If one channel opens in the axon hillock, all will open across the axon

repolarization, hyperpolarization, restoration

What are the three phases of the absolute refractory period?

repolarization

Phase 1 of the absolute refractory period

• Peak Potential: Once membrane potential reaches ~+30mV

• Gate Shift: Na+ gates close & voltage-gated K+ channels open to repolarize membrane

hyperpolarization

Phase 2 of the absolute refractory period

• K+ Efflux: K+ ions diffuse out of the neuron

• Membrane Shift: Outward flow causes temporary hyperpolarization

restoration

Phase 3 of the absolute refractory period

• Pump Action: K+ gates close, resting membrane potential reestablished by Na+/K+ pumps

• Refractory State: As this occurs, the neuron cannot be restimulated (absolute refractory period)

absolute refractory period

Period in which neurons cannot be restimulated

synapse

Area where two neurons come together

presynaptic membrane

Synaptic end terminal region of the presynaptic neuron

synaptic cleft

Narrow space between presynaptic and postsynaptic neurons

postsynaptic membrane

Receiving region of the postsynaptic neuron

cerebrum, diencephalon, cerebellum, brainstem

What are the four main regions of the brain?

cranium, meninges, cerebrospinal fluid, blood brain barrier

What 4 anatomical structures protect the brain?

pia, arachnoid, dura mater

What are the three layers of cranial meninges from deep to superficial?

pia mater

Deepest layer of cranial meninges

• Composition: Made of areolar connective tissues

• Structure: Follows contours of the brain

• Function: Provides passageway for blood vessel penetration

arachnoid mater

Middle layer of cranial meninges

• Composition: Made of collagen and elastic fibers

• Subarachnoid space: Between arachnoid and pia mater; contains cerebrospinal fluid (CSF)

• CSF: Liquid cushion to brain and spinal cord

dura mater

Most superficial outer layer of cranial meninges

• Composition: Dense irregular connective tissue

• Venous sinus: Contains venous blood

• Epidural space: Between dura mater and skull; contains large arteries that nourish meninges

• Sinuses: Created by dura folds

ventricles

Fluid filled cavities in the brain

• Connected system within the brain & spinal cord

• Lined with ependymal cells (specialized neuroglia)

• Completely filled with Cerebrospinal Fluid (CSF)

1st lateral, 2nd lateral, 3rd, 4th

What are the 4 ventricles of the brain?

1st & 2nd lateral ventricle

Ventricle

• LOCATION

  • Found in each cerebral hemisphere

• KEY STRUCTURE

  • Separated by the septum pellucidum

3rd ventricle

Ventricle

• LOCATION

  • Found in the diencephalon

• CONNECTION

  • Connected to lateral ventricles by the interventricular foramen

4th ventricle

• LOCATION

  • Found between pons & cerebellum

• CONNECTIONS

  • Connected to third ventricle via cerebral aqueduct

  • Merges with central canal of spinal cord

cerebrospinal fluid

Key Functions

• Brain Weight: Reduces effective brain weight

• Cushioning: Provides shock absorption & protection

• Transport: Delivers O₂ & nutrients, removes waste

Formation

ORIGIN

Filtered from blood plasma through capillaries.

MODIFICATION

Modified by specialized ependymal cells in the choroid plexus of each ventricle

• Lack of normal flow = elevated intracranial pressure (hydrocephalus)

blood brain barrier

Acts as a physical barrier to protect neurons from circulating waste products, hormones, or drugs in the blood

• Glial Cell Support: Formed primarily by astrocytes.

• Chemical Secretion: Astrocyte extensions secrete chemicals influencing capillary endothelial cells to form tight junctions, strictly limiting movement out of the blood

• Lipid-Soluble Compounds: Able to cross Barrier efficiently

  Key Examples: Gases, alcohol, and nicotine.

cerebrum

Region of the brain:

Processes complex intellectual and cognitive functions.

• Vision, reading, understanding, learning, thinking, and application

Hemispheres:
Divided into two halves separated by the longitudinal fissure.

Corpus Callosum:
Connected by a specialized white matter tract (corpus callosum) which allows for interhemispheric communication.

frontal, parietal, occipital, temporal, insula

What are the 5 major lobes of the cerebrum?

frontal lobe

Major lobe of Cerebrum:

Motor Control: Speech, reasoning, personality, and motor function.

Prefrontal Cortex: Responsible for formulating intentions and planning how to accomplish those intentions.

parietal lobe

Major lobe of Cerebrum:

Sensory Information: Processes touch, temperature, pain, itch, and language comprehension.

Sensory Homunculus: Processing power devoted proportionally to mapped body regions.

occipital lobe

Major lobe of Cerebrum:

Visual Processing: Dedicated to receiving and processing visual stimuli and information.

temporal lobe

Major lobe of Cerebrum:

Auditory & Olfactory: Processes sound information, facial recognition, and serves as a receptive area for smell.

insula

Major lobe of cerebrum:

Multimodal Integration: Processes taste, smell, sound, visceral/body surface sensations, and emotions.

gyri

Folds & Ridges: Elevated convolutions on the cerebral cortex surface.

• Precentral gyrus

• Postcentral gyrus

sulci

Grooves & Fissures: Shallow grooves separating adjacent gyri.

• Central sulcus

• Parieto-occipital sulcus

• Lateral sulcus

primary, association area, multimodal integration area

What are the three cortical areas of the Cerebrum?

broca’s area

Brain matter & forebrain:

Location: Left hemisphere of frontal lobe

Primary Function:

• Motor speech production

• Controls muscles required for vocalization

wernicke’s area

Brain matter & forebrain:

Location: Left hemisphere near lateral sulcus and auditory cortex

Primary Function:

• Comprehension of spoken language

• Interpretation of written language

limbic system

Brain matter & forebrain:

Core Function: Processes emotions (pleasure, anger, rage, hunger)

Key Components:

• Hippocampus: Forming new long-term memories

• Amygdala: Connects to hippocampus; regulates emotional states (e.g. fear)

diencephalon

Region of the brain:

Connects cerebrum to other areas of CNS

• Deep in the center of the brain

• Thalamus, hypothalamus, epithalamus

thalamus

Part of diencephalon:

• Paired masses of gray matter on sides of third ventricle

• Sorts and relays sensory information (except olfactory)

• Mediates motor activity

hypothalamus

Part of diencephalon:

Location: Anterior-inferior to thalamus

Infundibulum: Inferior to hypothalamus, attaches to pituitary gland

Homeostatic Functions:

• Controls ANS & endocrine system

• Regulates emotional states & sleep/wake cycles

• Regulates body temp, hunger, satiety, thirst & water balance

epithalamus

Part of diencephalon:

Location: Covers third ventricle; forms roof of diencephalon

Key Component:

• Pineal Gland: Secretes melatonin to regulate day/night sleep cycles

cerebellum

Region of the brain:

Contains half the brain’s neurons

Key Features:

• Vermis: runs along midline of cerebellar hemispheres

• Lobes (anterior, posterior, flocculonodular) separated by fissures

• Connected to brainstem via cerebellar peduncles (white matter)

Primary Roles:

• Coordinating & optimizing movements

• Maintaining posture and balance

• Fine motor adjustments

Cognitive & Other Roles:

• Learning and information processing

• Sleep-related functions

brainstem

Region of the brain:

• Located between the diencephalon and spinal cord

• Primary site of origin for many cranial nerves

• Autonomic Controls: Regulates vital functions including breathing, heart rate, and blood vessel diameter

• Reflex Coordination: Coordinates critical visceral reflexes such as swallowing, coughing, and sneezing

superior colliculi

In brainstem:

Signals body movement (upper body, head, and eyes) in response to visual stimuli

inferior colliculi

In brain stem:

Coordinates reflex movement of head toward auditory stimuli and loud noises

cranial nerves

Part of peripheral nervous system; connected directly to brain (vs. spinal cord)

• Consists of 12 pairs emerging from the brainstem and brain

• Numbered sequentially from most anterior (CN I) to most posterior/inferior (CN XII)

• Each nerve possesses specialized sensory functions, motor functions, or both

olfactory nerve

CN I (sense of smell)

optic nerve

CN II (sense of sight)

CN III, IV, VI

Nerves that innervate the extraocular muscles that allow us to move our eyes

trigeminal nerve

The major sensory nerve of the face

• CN V

It has three large branches, each of which supplies an area of the face:

• ophthalmic

• maxillary

• mandibular

facial nerve

CN VII innervates the muscles of facial expression

• It also carries some taste sensations (anterior 2/3 of tongue).

• Paralysis of  CN VII is called Bell’s Palsy and leads to loss of ability to close  the eyes and impairment of taste and salivation

vestibulocochlear nerve

CN VIII

From the inner ear

• vestibular component carries information on balance

• cochlear component enables hearing

• Damage of CN VIII causes vertigo, ringing in the ears, and/or deafness.

glossopharyngeal nerve

CN IX

Nerve carries some taste sensations as well as ANS impulses to salivary glands and the mechanoreceptors of the carotid body and carotid sinus (senses changes in BP)

vagus nerve

CN X “the wanderer”

Carries most of the parasympathetic motor efferents to the organs of the thorax and abdomen

spinal accessory nerve

CN XI

Supplies somatic motor innervation to the Trapezius and Sternocleidomastoid muscles

hypoglossal nerve

CN XII

This is a very large nerve (a lot of resources) to be devoted solely to the tongue – it takes a lot more coordination than you might guess to chew, talk, and swallow without injuring our tongue

aorta

Main artery originating directly from the heart's left ventricle

common carotid arteries

Major blood vessels passing up through the neck

internal, external carotid arteries

Branches supplying the brain (internal) and neck/face (external)

jugular veins

Carries venus (deoxygenated) blood from brain back to the heart

spinal cord

Begins as a continuation of the medulla oblongata (the most inferior portion of the 

brain stem) extending  from the foramen  magnum of the occipital bone to its 

termination as the conus medullaris between L₁ - L_2.

• Meninges

• Cerebrospinal fluid

• Epidural space

• Vertebrae

cerebrospinal fluid

A clear and colorless fluid; produced by the choroid plexus of the brain

• cushion to help prevent injury

• found in the subarachnoid space (between the arachnoid and pia mater) and central canal

epidural space

Located outside of dura mater; filled with fat and large blood vessels

• helps protect the spinal cord

sensory tracts

Afferent; ascending tracts

From the spinal cord: 

• Dorsal root

• Ventral root 

Dorsal & ventral roots form the spinal nerve

motor tracts

Efferent; descending tracts

From the spinal cord: 

• Dorsal root

• Ventral root 

Dorsal & ventral roots form the spinal nerv

spinal nerves

Paths of communication between the spinal cord and specific regions of the body

• Arranged in fascicles surrounded by a perineurium, with the entire nerve sheathed by a CT epineurium