12-5: The Brain - diencephalon and cerebrum (overview)

Question 1

diencephalon

Answer 1

forms the central core of the brain - consists of 2 parts (thalamus and hypothalamus)

Question 2

thalamus

Answer 2

2 egg shaped masses of mostly gray matter (many nuclei) joined in the middle by the intermediate mass

Question 3

Where is a thalamus located?

Answer 3

above the midbrain, forming the lateral walls of the third ventricle

Question 4

What is the function of the thalamus?

Answer 4

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

Question 5

hypothalamus

Answer 5

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

Question 6

The hypothalamus connects to the ____ gland by a thin stalk called the ___.

Answer 6

pituitary; infundibulum

Question 7

mammillary body

Answer 7

bumps bulging anteriorly from the hypothalamus; relay stations for olfactory imput

Question 8

What are some ways that the hypothalamus is important to homeostasis?

Answer 8

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)

Question 9

Limbic System

Answer 9

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.

Question 10

cingulate gyrus

Answer 10

part of the limbic system that recognizes angry or fearful facial expressions, assesses danger, and elicits fear response

Question 11

amygdala

Answer 11

part of the limbic system that plays a role in expressing emotions through gestures and resolving mental conflicts when frustrated

Question 12

Most limbic output is relayed through ______; because of this, people under emotional distress often have ____ disorders (also called ____).

Answer 12

hypothalamus; visceral disorders (heart burn, high blood pressure); psychosomatic (or “emotion-induced” illnesses)

Question 13

The cerebrum is the most ___ part of the brain, accounting for ___% of mass.

Answer 13

superior; 83%

Question 14

cerebral cortex

Answer 14

surface of the cerebrum, made of gray matter and consisting of the cell bodies of neurons; the “conscious brain”

Question 15

gyrus

Answer 15

elevated ridge in the cortex (“mountains”); form b/c gray matter grows faster than underlying white matter in the embryo

Question 16

sulcus

Answer 16

shallow grooves (“valleys”) between the gyri

Question 17

fissures

Answer 17

deep grooves between some gyri

Question 18

What are the most prominant fissures?

Answer 18

longitudinal fissure - divides cerebrum into right and left halves

transverse fissure - separates cerebrum from cerebellum

Question 19

frontal lobe

Answer 19

anterior part of cerebrum, extending back to the central sulcus

Question 20

parietal lobe

Answer 20

behind the central sulcus, but above the parietal-occipital sulcus

Question 21

occipital lobe

Answer 21

posterior part of the cerebrum, between the parieto-occipital sulcus and the transverse fissure, which separates it from the cerebellum

Question 22

temporal lobe

Answer 22

below the lateral sulcus on each side of the brain

Question 23

insular lobe

Answer 23

lies deep within the lateral sulcus, under the other lobes (not visible from surface)

Question 24

white matter

Answer 24

bundles of myelinated axons under the cortex, responsible for communication between different parts of the brain; run in three directions

Question 25

association fibers

Answer 25

transmit impulses between gyri in the same hemisphere

front to back on same side

Question 26

commissural fibers

Answer 26

transmit impulses from gyri in one hemisphere to corresponding gyri on the other; ex: corpus callosum

(right to left)

Question 27

projection fibers

Answer 27

transmit impulses between cerebrum and lower brain or spinal cord

(up and down)

Question 28

gray matter

Answer 28

outer cortex (made of cell bodies and neuroglia), and basal nuclei (paired masses of gray matter deep within each hemisphere)

Question 29

What is the function of the basal nuclei?

Answer 29

some control large, subconscious movements of skeletal muscles (eg. swinging arms when walking), others regulate muscle tone

Question 30

What does damage to basal nuclei cause?

Answer 30

abnormal body movements, tremors, problems with posture, slow movement (Parkinson’s and Huntington’s disease)

Question 31

functional areas of cerebral cortex

Answer 31

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