Diencephalon and Cerebral Cortex: Anatomy, Functions, and Sensory Areas
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What are the major components of the diencephalon?
Epithalamus, thalamus, hypothalamus, and third ventricle
Where is the diencephalon located?
Superior to the midbrain and surrounded by the cerebrum
What structure attaches the pituitary gland to the diencephalon?
Infundibulum
What gland is located in the epithalamus?
Pineal gland
What hormone does the pineal gland produce?
Melatonin
What is the main function of melatonin?
Regulates circadian rhythm, or the 24-hour body clock
When are melatonin levels highest?
At night
When are melatonin levels lowest?
During the day
What controls the epithalamus and pineal gland?
Hypothalamus
How do teen melatonin patterns differ from adults?
Teen melatonin levels tend to spike later than adults
What is the thalamus made of?
Two oval masses of gray matter covered with white matter
What is the main function of the thalamus?
Relay and processing center for sensory impulses (except olfaction) going to the cerebrum
Which sense does NOT relay through the thalamus?
Olfaction (smell)
How does the thalamus act as a sensory information filter?
It helps filter and process sensory information before it reaches the cerebrum
What would happen to sensory interpretation without the thalamus?
The cerebrum would have difficulty properly receiving and interpreting sensory information
What is one major role of the hypothalamus?
Controls many homeostatic functions of the body
What is the hypothalamus's role in the autonomic nervous system?
It acts as an autonomic nervous system control center
What type of body activity does the ANS control?
Involuntary activity
Which ANS divisions are regulated by the hypothalamus?
Sympathetic and parasympathetic divisions
What structures are influenced by hypothalamic ANS control?
Cardiac muscle, smooth muscle, and glands
What is the hypothalamus's role in the endocrine system?
It acts as an endocrine system control center
What does the endocrine system do?
Secretes hormones into the bloodstream
What two hormones are produced by the hypothalamus and released by the posterior pituitary?
ADH and oxytocin
What does ADH stand for?
Antidiuretic hormone
What is an important function of ADH?
Helps the kidneys conserve water and reduce urine output when dehydrated
What hypothalamic hormone is associated with the reproductive system?
Oxytocin
How does the hypothalamus control the anterior pituitary?
It produces hormones that regulate anterior pituitary hormone secretion
How does the hypothalamus help regulate body temperature?
It senses the temperature of blood traveling through it and triggers responses to maintain temperature
What happens when body temperature becomes too high?
The body increases heat loss, such as through sweating
What happens when body temperature becomes too low?
The body conserves or produces heat, such as through shivering
What are electrolytes?
Ions and molecules that can carry an electric current (Sodium, potassium)
What are examples of important electrolytes?
Sodium (Na+) and potassium (K+)
What hypothalamic center helps regulate water and electrolyte balance?
The thirst center
What does the thirst center monitor?
Blood for changes related to water and electrolyte balance
What two hypothalamic centers regulate hunger and food intake?
Hunger/feeding center and satiety center
What does the hunger or feeding center do?
Promotes hunger and food intake
What does the satiety center do?
Produces the feeling of fullness and helps stop food intake
What does the hypothalamus regulate in relation to sleep?
Sleep-wake or circadian cycles
How does the hypothalamus affect melatonin secretion?
It regulates the pineal gland's secretion of melatonin
What happens when the hypothalamus is exposed to light?
Body temperature rises and the pineal gland reduces melatonin secretion
What happens when the hypothalamus responds to darkness?
Body temperature decreases and melatonin secretion increases
How can nighttime light interfere with circadian rhythm?
It can signal the hypothalamus to suppress melatonin secretion
How is the hypothalamus involved in emotional behavior?
It is connected to the limbic system and helps produce physical responses to emotions
What is an example of a physical response to emotion controlled by the hypothalamus?
Blushing
What major type of functions is the cerebrum responsible for?
Higher brain functions
What is the outer gray matter of the cerebrum called?
Cerebral cortex
What is located beneath the cerebral cortex?
Inner white matter
In general, each cerebral hemisphere controls what side of the body?
The opposite side
How many cerebral hemispheres are there?
Two
What is the longitudinal fissure?
A deep groove that separates the left and right cerebral hemispheres
What is the corpus callosum?
Axons that connect the left and right cerebral hemispheres
What type of nervous tissue primarily forms the corpus callosum?
White matter
Why is the cerebral cortex highly convoluted?
Its surface is folded into gyri and sulci
What is a gyrus?
A raised area or elevation of the cerebral cortex
What is a sulcus?
A depression or groove between gyri
How many lobes are present in each cerebral hemisphere?
Five
What are the five lobes of each cerebral hemisphere?
Frontal, parietal, temporal, occipital, and insula
What sulcus forms the posterior boundary of the frontal lobe?
Central sulcus
What general functions are associated with the frontal lobe?
Concentration, decision-making, planning, personality, voluntary movement, and motor speech
Where is Broca's area located?
Left frontal lobe
What is another name for Broca's area?
Motor speech area
What is the function of Broca's area?
Controls muscular movements needed for speech
What can occur if Broca's area is damaged?
A person may have difficulty physically producing speech
Where is the primary motor cortex located?
Precentral gyrus of each frontal lobe
What does the primary motor cortex control?
Voluntary skeletal muscle movement
Which side of the body does the left primary motor cortex control?
Right side
Which side of the body does the right primary motor cortex control?
Left side
What separates the frontal and parietal lobes?
Central sulcus
Where does the parietal lobe end anteriorly?
At the central sulcus
What forms a lateral limit of the parietal lobe?
Lateral sulcus
Where is the primary somatosensory cortex located?
Postcentral gyrus of each parietal lobe
What does the primary somatosensory cortex receive?
Sensory input from the skin, muscles, and joints
Where is sensory information from the left side of the body processed?
Right primary somatosensory cortex
Where is sensory information from the right side of the body processed?
Left primary somatosensory cortex
What is the major function of Wernicke's area?
Helps us understand written and spoken language
What is another description of Wernicke's area?
Speech comprehension area
Which lobes does Wernicke's area overlap?
Parietal and temporal lobes
What is the primary auditory cortex responsible for?
Receiving and processing incoming sounds
Which lobe contains the primary auditory cortex?
Temporal lobe
Which lobe contains part of Wernicke's area?
Temporal lobe
What is the primary olfactory cortex responsible for?
Processing smell information and providing conscious awareness of smells
Which lobe contains the primary olfactory cortex?
Temporal lobe
What major cortex is located in the occipital lobe?
Primary visual cortex
What does the primary visual cortex do?
Receives and processes incoming visual information
Where is the insula located?
Deep to the lateral sulcus
What is one function of the insula?
Involved with memory
What sensory cortex is located in the insula?
Primary gustatory cortex
What does the primary gustatory cortex process?
Taste information
Which lobe is associated with voluntary skeletal muscle movement?
Frontal lobe
Which lobe is associated with somatic sensory information?
Parietal lobe
Which lobe is associated with hearing and smell?
Temporal lobe
Which lobe is primarily associated with vision?
Occipital lobe
Which lobe is associated with taste?
Insula
Precentral gyrus = what functional area?
Primary motor cortex
Postcentral gyrus = what functional area?
Primary somatosensory cortex
Broca's area = what function?
Motor production of speech
Wernicke's area = what function?
Understanding written and spoken language
Primary auditory cortex = what function?
Hearing
Primary olfactory cortex = what function?
Smell
Primary visual cortex = what function?
Vision