A&P ch 12: Central Nervous System

surface markings of cerebrum

Fissure: deep grooves

Longitudinal fissure

– Separates two hemispheres

▪ Transverse cerebral fissure

– Separates cerebrum and cerebellum

Sulcus: shallow grooves

 Gyrus: ridges

lobe vs cortex

Lobe: physical structure that can be SEEN and

TOUCHED

Cortex:  REGION within the brain that plays a role

in neural processing

gray matter and white matter

Gray matter: short, nonmyelinated neurons and cell

bodies

• White matter: myelinated and nonmyelinated axons

In CEREBRUM, grey matter is superficial to white matter

• EVERYWHERE ELSE IN CNS, grey matter is deep to

white matter

ventricles

Fluid-filled chambers that are continuous to one another

and to central canal of spinal cord

– Filled with cerebrospinal fluid (CSF)

– Lined by ependymal cells (neuroglia cells)

• Paired lateral ventricles are large, C-shaped chambers

located deep in each hemisphere

• Each lateral ventricle is connected to the third ventricle via

interventricular foramen

• Third ventricle is connected to the fourth ventricle via

cerebral aqueduct

Frontal lobe

Handles executive functions such as planning, reasoning, problem-solving, emotional regulation, and personality

Parietal lobe

Integrates sensory information from across the body, including touch, temperature, pressure, and pain. It contains the somatosensory cortex and helps with spatial awareness and object recognition

Temporal lobe

Processes auditory signals (hearing), language comprehension (such as Wernicke's area), memory storage via the hippocampus, and aspects of smell and emotion.

Occipital

Serves as the primary visual processing center, interpreting visual data from the eyes such as shape, color, depth, distance, and object identity.

Insula lobe

integrate internal bodily states with emotional, sensory, and cognitive experiences

Cerebral cortex

makes up abt 40% of brain

1. Contains three types of functional areas:

▪ Motor areas: control voluntary movement

▪ Sensory areas: conscious awareness of sensation

▪ Association areas: integrate diverse information

2. Each hemisphere is concerned with contralateral

(opposite) side of body

3. Lateralization (specialization) of cortical function can

occur in only one hemisphere

4. Conscious behavior involves entire cortex in one way

or another

 motor cortexes (in frontal lobe) and sensory cortexes (in parietal lobe)

MOTOR: Sends commands down the spinal cord and brainstem to move muscles

prefrontal cortex: decision making, the brain's "command center" for higher-level cognitive processes

Premotor cortex: sets up output, responsible for planning, selecting, and coordinating complex movement sequences

Primary motor cortex: releases signal, executes direct, voluntary muscle movements

SENSORY:

Primary somatosensory cortex: Acts as the main "landing spot" for raw tactile, thermal, nociceptive (pain), and proprioceptive signals.

Somatosensory association cortex: association area, Performs higher-level synthesis and integration. It combines elementary touch, temperature, and shape data with memory (via connections to the hippocampus and amygdala) and visual information to interpret the meaning of an object or experience.

Homunculus

why the motor and somatosensory cortexes are so unequally broken up with regards (think homunculus)

the brain allocates cortical real estate based on functional density and evolutionary utility, rather than physical size

Limbic system

Large part of emotional or affective brain

The limbic system is a group of structures deep inside the brain that controls emotions, memories, basic drives, and the fight-or-flight response. emotional responses turn into odors

Corpus Callosum: connects left and right hemisphere

Reticular formation

– Sends impulses to cerebral cortex to keep it

conscious and alert

– Filters out repetitive, familiar, or weak stimuli (~99%

of all stimuli is not relayed to consciousness)

– Inhibited by sleep centers, alcohol, drugs

– Severe injury can result in permanent

unconsciousness (coma)

Hippocampus (shrimp shaped)

Location: deep into

temporal lobe

• Has a major role in learning and memory

– Helps to convert short term memory to long term

• Plastic and vulnerable structure that gets damaged by a variety of stimuli

• Affected in a variety of neurological and psychiatric disorders

• One of two places in the brain with active neurogenesis!

– Subgranular zone of dentate gyrus

 Amygdala (you have 1 on each side)

recognizes angry or fearful facial

expressions, assesses danger, and elicits fear

response

Cingulate gyrus

plays role in expressing emotions via gestures and resolves mental conflict

Basal Nuclei (Ganglia)

– Influence muscle movements

– Play role in cognition and emotion

– Regulate intensity of slow or stereotyped movements

– Filter out incorrect/inappropriate responses

– Inhibit antagonistic/unnecessary movements

• Parkinson’s disease and Huntington’s disease are

disorders of the basal nuclei

The Diencephalon

– Thalamus

– Hypothalamus:

– Epithalamus:

Thalamus

Gateway to the cerebral cortex, act as relay station for information coming into cortex

Hypothalamus

Major control center of autonomic nervous system and endocrine system

– Plays essential role in homeostatic regulation of all body systems

Epithalamus

Most dorsal portion of diencephalon

• Forms roof of third ventricle

• Contains pineal gland (body)

– Extends from posterior border

– Secretes melatonin that helps regulate sleep-wake cycle

Brain Stem

Consists of three regions: midbrain, pons, and medulla oblongata

contains nuclei embedded in white matter

• Controls automatic behaviors necessary for survival

• Contains fiber tracts connecting higher and lower neural centers

• Nuclei are associated with 10 of the 12 pairs of cranial nerves

Pons

Ascending sensory tracts

• Descending motor tracts

• Pathways in and out of cerebellum

• Cranial nerves V, VI, VII, and VIII

– Sensory roles: hearing, equilibrium, taste, facial sensations

– Motor roles: eye movement, facial expressions, chewing,

swallowing, urination, and secretion of saliva and tears

Medulla Oblongata

• All nerve fibers connecting the brain to the spinal cord pass through the

medulla

• Four pairs of cranial nerves begin or ending medulla—IX, X, XI, XII

•Cardiac center

•Vasomotor center

•Respiratory centers

•Reflex centers

•Reticular formation

Cerebellum

• 11% of brain mass

• Located dorsal to pons and medulla

• Processes input from cortex, brain stem, and sensory

receptors to provide precise, coordinated movements

of skeletal muscles

• Also plays a major role in balance

meninges (from external to internal): dura

mater, arachnoid mater, and pia mater

– Cover and protect CNS

– Protect blood vessels and enclose venous sinuses

– Contain cerebrospinal fluid (C SF)

– Form partitions in skull

Dura Mater

The tough, outermost layer. Its name means "hard mother" in Latin. It is made of thick, fibrous connective tissue and acts as a strong protective shield against physical trauma.

Arachnoid Mater

The middle, web-like layer. Its name comes from the spider-web-like appearance of the delicate fibers that stretch from it. Beneath it lies the subarachnoid space, which is filled with cerebrospinal fluid (CSF) to cushion the central nervous system.

Pia Mater

The delicate, innermost layer. Its name means "tender mother." It is a thin, microscopic membrane that closely hugs and contours directly to every fold, curve, and groove (sulci and gyri) of the brain and spinal cord, carrying blood vessels to nourish neural tissue.

general anatomy and structure of the spinal cord

• Spinal cord is enclosed in vertebral column

– Begins at the foramen magnum

– Ends at L1 or L2 vertebra

• Functions

– Provides two-way communication to and from brain and body

– Major reflex center: reflexes are initiated and completed at spinal cord

• Cervical: 8 pairs (C1–C8)

• Thoracic: 12 pairs (T1–T12)

• Lumbar: 5 pairs (L1–L5)

• Sacral: 5 pairs (S1–S5)

• Coccygeal: 1 pair (Co1)

closer look at spinal cord

motor (efferent) signals take out of the spinal cord vs the pathway that

sensory (afferent) signals take into the spinal cord

Sensory (afferent) signals enter the spinal cord through the dorsal (posterior) root

motor (efferent) signals exit the spinal cord through the ventral (anterior) root

Ascending Spinal Cord Tracts (sensory)

• Conduct sensory pathways upward through a chain of three neurons:

– First-order neuron

▪ Conducts impulses from cutaneous receptors and proprioceptors

– Second-order neuron

▪ Interneuron (spinal cord to brain)

– Third-order neuron

▪ Also an interneuron

▪ Axon extends to somatosensory cortex

Descending Pathways (motor)

Deliver efferent impulses from brain to spinal cord

• Motor pathways involve two neurons:

– Upper motor neurons

▪ Pyramidal cells in primary motor cortex

– Lower motor neurons

▪ Ventral horn motor neurons

▪ Innervate skeletal muscles

 ventral/dorsal roots and horns

Dorsal Horn:

Posterior (back) region of the spinal gray matter

Receives and processes incoming sensory information

Sensory interneurons and relay neurons

Dorsal Root

Afferent root extending from the dorsolateral spinal cord

Carries sensory signals into the spinal cord from the body

Afferent (sensory) nerve fibers

Dorsal Root Ganglion (DRG)	A swelling on the dorsal root just outside the cord	Houses the cell bodies of unipolar sensory neurons	Sensory neuron cell bodies
Ventral Horn	Anterior (front) region of the spinal gray matter	Sends motor commands out to control skeletal muscles	Somatic motor neurons (alpha and gamma)
Ventral Root	Efferent root emerging from the ventrolateral spinal cord	Carries motor commands away from the spinal cord	Efferent (motor and visceral) nerve fibers