12-5: The Brain - diencephalon and cerebrum (overview) Flashcards
diencephalon
forms the central core of the brain - consists of 2 parts (thalamus and hypothalamus)
thalamus
2 egg shaped masses of mostly gray matter (many nuclei) joined in the middle by the intermediate mass
Where is a thalamus located?
above the midbrain, forming the lateral walls of the third ventricle
What is the function of the thalamus?
relay station - all sensory input except smell passes through the thalamus which relays it to the proper area of the conscious brain for interpretation. 12 nuclei, each sending fibers to specific regions of the cortex
hypothalamus
named for its position below the thalamus - also made of many nuclei. Forms the floor of the third ventricle. Important to overall body homeostasis; no blood brain barrier here
The hypothalamus connects to the ____ gland by a thin stalk called the ___.
pituitary; infundibulum
mammillary body
bumps bulging anteriorly from the hypothalamus; relay stations for olfactory imput
What are some ways that the hypothalamus is important to homeostasis?
controls body temperature (monitors temp of blood)
hunger center (monitors BSL - when low, causes feelings of hunger)
thirst center (monitors osmotic pressure of blood - when too concentrated, causes feelings of thirst)
controls autonomic centers (regulates ANS by controlling centers in brainstem (BP, respitory rate, heart rate, etc)
controls endocrine system (detects changes in body and produces releasing hormones that stimulate the pituitary gland (“master gland”) to make its hormones)
regulates sleep cycles (has biological clock which sets timing of sleep cycle in response to light/darkness cues)
emotions (at the heart of the Limbic System, its involved in the perception of pain, fear, rate, and pleasure, and also initiates the expression of emotion)
Limbic System
network of neurons encircling upper part of brainstem in both cerebral hemispheres. Its many parts are linked together by the fornix and other fiber tracts. It is our emotional or affective brain.
cingulate gyrus
part of the limbic system that recognizes angry or fearful facial expressions, assesses danger, and elicits fear response
amygdala
part of the limbic system that plays a role in expressing emotions through gestures and resolving mental conflicts when frustrated
Most limbic output is relayed through ______; because of this, people under emotional distress often have ____ disorders (also called ____).
hypothalamus; visceral disorders (heart burn, high blood pressure); psychosomatic (or “emotion-induced” illnesses)
The cerebrum is the most ___ part of the brain, accounting for ___% of mass.
superior; 83%
cerebral cortex
surface of the cerebrum, made of gray matter and consisting of the cell bodies of neurons; the “conscious brain”
gyrus
elevated ridge in the cortex (“mountains”); form b/c gray matter grows faster than underlying white matter in the embryo
sulcus
shallow grooves (“valleys”) between the gyri
fissures
deep grooves between some gyri
What are the most prominant fissures?
longitudinal fissure - divides cerebrum into right and left halves
transverse fissure - separates cerebrum from cerebellum
frontal lobe
anterior part of cerebrum, extending back to the central sulcus
parietal lobe
behind the central sulcus, but above the parietal-occipital sulcus
occipital lobe
posterior part of the cerebrum, between the parieto-occipital sulcus and the transverse fissure, which separates it from the cerebellum
temporal lobe
below the lateral sulcus on each side of the brain
insular lobe
lies deep within the lateral sulcus, under the other lobes (not visible from surface)
white matter
bundles of myelinated axons under the cortex, responsible for communication between different parts of the brain; run in three directions
association fibers
transmit impulses between gyri in the same hemisphere
front to back on same side
commissural fibers
transmit impulses from gyri in one hemisphere to corresponding gyri on the other; ex: corpus callosum
(right to left)
projection fibers
transmit impulses between cerebrum and lower brain or spinal cord
(up and down)
gray matter
outer cortex (made of cell bodies and neuroglia), and basal nuclei (paired masses of gray matter deep within each hemisphere)
What is the function of the basal nuclei?
some control large, subconscious movements of skeletal muscles (eg. swinging arms when walking), others regulate muscle tone
What does damage to basal nuclei cause?
abnormal body movements, tremors, problems with posture, slow movement (Parkinson’s and Huntington’s disease)
functional areas of cerebral cortex
enables us to be aware of senses, to communicate, remember, understand, and initiate voluntary movements. Each hemisphere is concerned with the sensory and motor functions of the opposite side of the body
