lecture 13 - brain: diencephalon & cerebrum

Diencephalon

Region of the brain found deep within the brain; between the brainstem and cerebrum; must cut the brain along a sagittal section to visualize its structures

Four main components of the diencephalon

Thalamus; subthalamus; epithalamus; hypothalamus

Thalamus

• largest portion of the diencephalon

• 2 oval-shaped masses of gray matter

• superior portion

Interthalamic adhesion

Gray matter connection b/w the R and L sides of the thalamus

Subthalamus

directly below the thalamus

Epithalamus

• made up of the habenula and pineal gland

• posterior to the thalamus

Habenula

More superior portion of the epithalamus

Pineal gland

• inferior portion of the epithalamus

• pine cone shaped

• size of a pea

Hypothalamus

• most inferior portion of the diencephalon

• connects to the pituitary gland

the _________ and ______ _____ act as the connection between the nervous system and endocrine system

hypothalamus, pituitary gland

Corpus callosum

• section of cerebrum that connects the R and L hemispheres

• white C-shaped structure located just above the diencephalon

Thalamus structure

Two paired oval masses of gray matter connected by the interthalamic adhesion

Thalamic nuclei

• gray matter regions containing nuclei

• different regions of nuclei have different roles

• nuclei within regions have very similar functions

Geniculate

• “bent knee”

• describes the appearance of the medial and lateral geniculate nuclei

Medial geniculate nucleus

• small projection off edge of thalamus

• involved in auditory impulses

Lateral geniculate nucleus

• small projection off edge of thalamus

• involved in visual input

Location of medial and lateral geniculate nuclei

Inferior posterior side of the thalamus

• medial geniculate nucleus → back of the thalamus

• lateral geniculate nucleus is lateral to it

Third ventricle runs around the ______; cerebrospinal fluid moves in and around the ______ and between the mounds

thalamus, thalamus

The __________ _______ is a gray matter connection between the paired thalamic masses; this is the region where cerebrospinal fluid could not be seen

interthalamic adhesion

the ________ receives all sensory information except smell; sensory information synapses at the ______ before being sent to the _______ _____

thalamus, thalamus, cerebral cortex

the ______ receives sensory information, filters much of it, and sends it to the ______ _____

thalamus, cerebral cortex

the _______ helps filter sensory information so that not all sensory information has to be integrated or interpreted at the level of the cerebral cortex

thalamus

Medial geniculate nucleus function

• auditory impulses

• takes info from inner ear to primary auditory area of the cerebral cortex in the temporal lobe

Lateral geniculate nucleus function

Involved in visual input; gathers information from the retina and takes it to the primary visual area of the cerebral cortex in the occipital lobe

Sensory information from the inner ear or eye first synapses in the _______ before being sent to the ______ _____

thalamus, cerebral cortex

Subthalamus location

• inferior to the thalamus

• b/w the thalamus and hypothalamus

Subthalamus composition

• primarily white matter

Subthalamus white matter contains

• many axons moving through the area because the thalamus receives the majority of sensory information

Subthalamic nuclei

• gray matter areas within the subthalamus

• involved in controlling motor function with other areas and the cerebrum

Epithalamus location

Posterior superior region relative to the thalamus

Two portions of the epithalamus

Habenular nuclei or habenula; pineal gland

Habenula location

Superior portion of the epithalamus

Pineal gland location

Inferior portion of the epithalamus

Habenula function

Involved in:

• emotional control of behavior

• linking behaviors involving rewards

the ______ in the epithalamus plays a critical role in regulating motivational states and decision making

habenula

the ________ in the epithalamus is involved in integrating sensory, cognitive, and emotional information

habenula

the ______ in the epithalamus encodes both rewarding and aversive aspects of stimuli, which influence behavior

habenula

the ______ in the epithalamus is linked to conditions such as depression, addiction, and schizophrenia

habenula

Pineal gland shape and size

Pine cone shaped; about the size of a pea

the _____ ____ in the epithalamus is thought to play a role as the body's biological clock; believed to be linked to timing and growth and development, such as onset of puberty

pineal gland

Researchers believe the _____ _____ may secrete chemicals that signal other cascades of events to bring on physiological changes associated with puberty and later-life changes such as menopause

pineal gland

______ is a chemical believed to be secreted by the pineal gland; promotes sleepiness

melatonin

Melatonin is linked to the ____-____ cycle; ____ amounts are produced when asleep and help keep you asleep

sleep-wake, large

Melatonin is light sensitive; when exposed to light, melatonin levels ____

drop

Sleeping in a dark room helps keep melatonin levels ____

high

Turning on lights in the middle of the night _____ melatonin levels and can make it harder to fall back asleep

reduces

Hypothalamus location

• most inferior portion of diencephalon

• located on the anterior side

Infundibulum

A stalk in the hypothalamus that connects it to the pituitary gland

Pituitary gland

• master gland of the body

• responsible for secreting hormones involved in metabolism, reproduction, response to stress, and urine production

Infundibulum composition

• white matter

• connective tissue

Infundibulum function

Creates a link between the nervous system and endocrine system

Endocrine system

System that releases hormones into the body, typically via glands

Hypothalamic nuclei

• more than 12 different nuclei

• involved in a variety of functions including those important for homeostasis

the _________ controls things such as heart rate, blood pressure, respiration, digestion, hunger, thirst, body temperature, moods, emotions, and sex drive

hypothalamus

Preoptic area

region of hypothalamus involved in thermoregulation

the hypothalamus is located close to the ____ _____; this is where visual information from the two eyes comes together in the brain

optic chiasm

Nuclei of the ________ are densely packed and closely related; stimulation of one area can affect neighboring areas

hypothalamus

Close neural connections between _________ nuclei can help explain why emotions can interfere with hunger or thirst

hypothalamic

Along with olfactory and memory regions, the ________ is thought to play a role in visceral and emotional responses to odors

hypothalamus

Visceral

Refers to anything internal or inside the body

Visceral and emotional responses to odors

Taking in a smell from the environment and producing an emotional or visceral response

Example of an emotional response to an odor

Smelling a perfume or cologne associated with a person can cause increased heartbeat, feeling flustered, and excitement

Example of a positive emotional response to an odor

Smelling a favourite meal can cause feelings of happiness, comfort, and feeling at home

Example of a visceral response to an odor

Smelling tequila after a negative past experience can cause nausea, feeling sick, or gagging

Cerebrum

Largest portion of the brain; typically the region people think of when talking about the brain

Cerebrum functions

• conscious processes and intellectual functions

• higher-level processing including planning

• reasoning

• organizing thoughts

• accessing and storing memories

• interpreting sensory information

• eliciting motor responses

Three general regions of matter in the cerebrum

1. Cerebral cortex (outer gray matter)

2. Deep clusters of nuclei (gray matter)

3. Cerebral medulla in between (white matter)

Cerebral cortex

Outer layer of gray matter in the cerebrum

Basal nuclei

• collections of gray matter deep within the cerebrum

• involved primarily in motor functions

Cerebral medulla

White matter region between the cerebral cortex and deep nuclei; consists of myelinated axon pathways

Cerebral medulla function

Myelinated axon pathways connect different gray matter regions within the cerebrum and connect the cerebrum to other regions of the brain

Lateral ventricles

Spaces within the cerebrum

Longitudinal fissure

Deep groove separating the right and left sides of the cerebrum

Gyri

Upward folds of the cerebral cortex

Gyrus

Singular form of gyri; an upward fold of the cerebral cortex

Sulci

Shallow grooves formed by folds of the cerebral cortex

Sulcus

Singular form of sulci; a shallow groove formed by folds of the cerebral cortex

Fissures

Deeper grooves in the cerebral cortex

Right and left cerebral hemispheres

Two halves of the cerebrum separated by the longitudinal fissure

Central sulcus

• groove running across the brain

• separates the frontal and parietal lobes

Frontal lobe location

Anterior to the central sulcus

Parietal lobe location

Posterior to the central sulcus

Precentral gyrus

• region just anterior to the central sulcus

• contains the primary motor cortex

Primary motor cortex

• located in the precentral gyrus

• gray matter region that initiates most motor responses

Postcentral gyrus

• region just posterior to the central sulcus

• contains the primary somatosensory cortex

Primary somatosensory cortex

• located in the postcentral gyrus

• most sensory information is sent here for interpretation

Special sensory information not interpreted in the primary somatosensory cortex (in the postcentral gyrus)

• vision

• hearing

• smell

Four main lobes of the cerebrum

Frontal lobe; parietal lobe; occipital lobe; temporal lobe

Cerebral lobes naming

Lobes are named after the bones that overlie them

Cerebral lobes arrangement

Four lobes on each cerebrum; paired in each of the two hemispheres

Frontal lobe functions

• motor functions

• aggression

• mood

Frontal lobe motor function area

Precentral gyrus or primary motor cortex

Parietal lobe roles

• majority of sensory information from the body is brought here for interpretation

Sensory information that does not go to the parietal lobe

Smell; taste; vision; hearing

Parietal lobe sensory example

Touch and pressure information coming from the skin

the ______ _____ is involved in monitoring and maintaining blood pH

parietal lobe

Parietal lobe primary sensory area

the primary somatosensory cortex (in the postcentral gyrus)

Parietoccipital sulcus

Separates the parietal lobe from the occipital lobe

Occipital lobe

involved in perception and integration of visual input

Light information turned into an electrical signal in the retina; travels on the optic nerve, goes to the ______, then moves to the _______ lobe

thalamus, occipital