Chapter 14 The Brain and Cranial Nerves

Neural tube

an embryonic structure that gives rise to the central nervous system with subdivisions that correspond to the future forebrain, midbrain, and hindbrain

Primary Brain Vesicles

Prosencephalon (forebrain)
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)

Prosencephalon/ forebrain

Forms the Telencephalon (becomes cerebrum) and Diencephalon.

Mesencephalon/ Midbrain

The Mesencephalon (midbrain) is the smallest and most superior region of the brainstem and is located between the diencephalon and the pons.

Rhombencephalon/ Hindbrain

Forms the Metencephalon (becomes cerebellum and pons) and Myelencephalon (becomes the medulla oblongata).

Secondary Brain Vesicles

1. Telencephalon
2. Diencephalon
3. Mesencephalon
4. Metencephalon
5. Myelencephalon

Telencephalon (end brain)

Becomes the Cerebral Hemispheres; includes cerebral cortex, basal ganglia, limbic system

Diencephalon (interbrain)

thalamus, hypothalamus, epithalamus

Metencephalon (afterbrain)

pons and cerebellum

myelencephalon

becomes medulla oblongata

Cerebrum

Largest part of the brain; responsible for voluntary muscular activity, vision, speech, taste, hearing, thought, and memory.

Brain stem

midbrain, pons, medulla oblongata; connects brain to spinal cord. Filters information flow between peripheral nervous system and the rest of the brain.

Gray matter

Brain and spinal cord tissue that appears gray with the naked eye; consists mainly of neuronal cell bodies (nuclei) and lacks myelinated axons.

White matter

an accumulation of axons within the CNS that is white because it is fatty, myelin sheath

Ventricles

Four hollow chambers (plus aqueducts) in brain that produce the cerebrospinal fluid that nourishes and cushions brain

Lateral ventricles

A set of paired ventricles lying within the cerebral hemispheres.

Septum pellucidum

thin membrane that separates lateral ventricles

Third ventricles

located in the diencephalon

Interventricular foramen

connects lateral ventricles to third ventricle

Fourth ventricle

small triangular chamber between pons and cerebellum

Cerebral aqueduct

a narrow tube interconnecting the third and fourth ventricles of the brain, located in the center of the mesencephalon

Lateral Apertures

Two openings in the side walls of the fourth ventricle that connect to the subarachnoid space.

Median aperture

An opening in the roof of the fourth ventricle that connects to the subarachnoid space

Cerebral hemispheres

two halves of the cerebral cortex, each of which serve distinct yet highly integrated functions

Gyri

ridges of the brain

Sulci

shallow grooves that separate gyri

Fissures

deep grooves in the brain

Longitudinal fissure

separates left and right cerebral hemispheres

Transverse cerebral fissure

separates cerebrum from cerebellum

Central sulcus

separates the frontal and parietal lobes of the cerebrum

Frontal lobe

The frontal (anterior) region of the cerebral cortex that has specialized areas for movement, abstract thinking, planning, memory, and judgement; associated with reasoning, planning, parts of speech, emotions, personality, and problem solving

Parietal lobe

portion of the cerebral cortex lying at the top of the head and toward the rear; receives sensory input for touch and body position; involved in processing various sensory and perceptual information; contains the primary somatosensory cortex;

Postcentral gyrus

primary somatosensory cortex; receives sensations from touch receptors, muscle-stretch receptors, and joint receptors

Parieto-occipital sulcus

separates the parietal lobe from the occipital lobe

Occipital lobe

A region of the cerebral cortex that processes visual information

Lateral sulcus

Separates temporal lobe from parietal and frontal lobes

Temporal lobe

A region of the cerebral cortex responsible for hearing and language.

Insula

a portion of the cerebral cortex folded deep within the lateral sulcus; plays an important role in the perception of bodily sensations, emotional states, empathy, and addictive behavior; contains gustatory cortex

Cerebral cortex

The outer region of the cerebrum, containing sheets of nerve cells; gray matter of the brain. The intricate fabric of interconnected neural cells covering the cerebral hemispheres; the body's ultimate control and information-processing center.

Contralateral

on the opposite side of the body from another structure

Ipsilateral

on the same side of the body as another structure

Motor areas

control the execution of voluntary movements

Primary (somatic) motor cortex

located in the precentral gyrus of the frontal lobe

Pyramidal cells

large neurons that allow conscious control of precise, skilled, skeletal muscle movements; found in the cerebral cortex, have a triangular cell body and a single, long dendrite among many smaller dendrites

Somatotopy

all muscles of body can be mapped to area on primary motor cortex; point-for-point correspondence between an area of the body and an area of the CNS

Motor homunculus

map showing portion of motor cortex devoted to each body region

Premotor cortex

area of the frontal cortex, active during the planning of a movement; controls learned motor skills

Broca area

specific area of the Cerebral Cortex responsible for the motor speech

Frontal eye field

involved in scanning eye movements; controls voluntary eye movements

Sensory areas

functional areas of the cerebral cortex that provide for conscious awareness of sensation

Primary somatosensory cortex

the region of the anterior parietal lobe whose primary input is from the somatosensory system; receives sensations from touch receptors, muscle-stretch receptors, and joint receptors

Proprioceptors

Sensory receptors, located in the muscles and joints, that provide information about body position and movement.

Spatial discrimination

identifying site or pattern of stimulus (studied by two-point discrimination test)

Somatosensory homunculus

the somatotopic map that corresponds to the primary somatosensory cortex

Somatosensory association cortex

-Integrates sensory input from primary somatosensory cortex for understanding of object
-Determines size, texture, and relationship of parts of objects being felt

Visual Areas

primary visual cortex and visual association area

Primary visual (striate) cortex

receives visual information from retinas

Visual association area

interprets information acquired through the primary visual cortex; uses past visual experiences to interpret visual stimuli

Primary auditory cortex

the region of the superior temporal lobe whose primary input is from the auditory system; each hemisphere receives auditory information from both ears

Auditory association area

stores memories of sounds and permits perception and interpreration of sounds

Vestibular (Equilibrium) cortex

responsible for conscious awareness of balance (position of head in space)

Olfactory cortex

Location: temporal lobe
Function: recieves information from smell receptors in the nasal cavities allowing us to become aware of odors

Primary olfactory (smell) cortex

involved in conscious awareness of odors

rhinencephalon

the part of the forebrain involved in receiving and integrating olfactory impulses; connected to the limbic brain

Gustatory cortex (taste)

insula

Visceral sensory area

Posterior to gustatory cortex
Conscious perception of visceral sensations, such as upset stomach or full bladder

Prefrontal cortex

the frontmost portion of the frontal lobes, especially prominent in humans; important for attention, working memory, decision making, appropriate social behavior, and personality

Posterior association area

Large region in temporal, parietal, and occipital lobes
Plays role in recognizing patterns and faces and localizing us in space
Involved in understanding written and spoken language (Wernicke's area)

Limbic association area

provides emotional impact that helps establish memories

Lateralization

cognitive function that relies more on one side of the brain than the other

Cerebral dominance

The tendency of each brain hemisphere to exert control over different functions, such as language or perception of spatial relationships.

Cerebral white matter

composed of fiber tracts carrying impulses to, from, or within the cortex

Association fibers

connect different parts of the same hemisphere

Commissures

Connections of nerve fibers which allow the two hemispheres of the brain to communicate with one another

Corpus callosum

A thick band of axons that connects the two cerebral hemispheres and acts as a communication link between them.

Projection fibers

vertical fibers that connect hemispheres with lower brain or spinal cord

Basal nuclei

Internal gray matter within the cerebral hemispheres. Controls muscle activity and posture; largely inhibits unintentional movement when at rest

Hypothalamus

A neural structure lying below the thalamus; it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion and reward.

Mammillary bodies

part of the limbic system; involved in memory

Infundibulum

A stalk that attaches the pituitary gland to the hypothalamus.

Pituitary gland

The endocrine system's most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands.

Epithalamus

Contains pineal body. Involved in the sleep/wake cycle

Pineal gland

secretes melatonin

Hormone melatonin

the hormone in the brain that regulates sleep

Midbrain

A small part of the brain above the pons that integrates sensory information and relays it upward. Reflex center for hearing and sight

Cerebral peduncles

two bulging structures that contain descending pyramidal motor tracts

Oculomotor

Cranial nerve III, Motor, Eye movement

Corpora quadrigemina

Comprised of the superior and inferior colliculi; coordinates visual and auditory reflexes

Superior colliculi

visual reflex center

Inferior colliculi

auditory reflex center

Substantia nigra

midbrain structure where dopamine is produced; involved in control of movement

Pons

the part of the brainstem that links the medulla oblongata and the thalamus. Contains the reticular formation and part of the respiratory center

Abducens

Cranial Nerve VI; lateral eye movement

Facial nerves

Cranial nerve VII; Motor and sensory nerves and helps with facial expression, salivary glands, and taste

Medulla oblongata

Contains centers that control several visceral functions, including breathing, heart and blood vessel activity, swallowing, vomiting, and digestion.

Hypoglossal nerves

Cranial Nerve XII innervate extrinsic and intrinsic muscles of tongue that contribute to swallowing and speech

Vagus nerves

Cranial nerve pair X. The vagus nerves are very large mixed nerves (They carry both sensory input and motor input) that innervate virtually every visceral organ. They are especially important in transmitting parasympathetic input to the heart and digestive smooth muscle.

Cochlear nuclei

Brainstem nuclei that receive auditory input from auditory hair cells and send output to the superior olivary complex

Vestibular nuclei

Brainstem nuclei that receive balance/equilibrium information from the vestibular organs through cranial nerve VIII (the vestibulocochlear nerve).

Folia

folds of the cerebellum