Brain Structure and Function

• The major structures of the brain and their functions include the hindbrain, midbrain, and forebrain.

Areas of the Brain

• The brain is divided into three main areas: the hindbrain, the midbrain, and the forebrain.
• The forebrain contains the cerebrum, thalamus, hypothalamus, and pituitary gland.
• The midbrain connects the hindbrain and forebrain.
• The hindbrain contains the pons, medulla oblongata, and cerebellum.

Hindbrain

• The hindbrain consists of the cerebellum, pons, and medulla.
• The midbrain, pons, and medulla oblongata are referred to as the brainstem; sometimes only the pons and medulla oblongata are.
• The brainstem is where all cranial nerves are situated.

Hindbrain - Medulla Oblongata

• The medulla oblongata is the lowest part of the brain and the lowest portion of the brainstem.
• It is located between the pons and the spinal cord and is continuous with the spinal cord.
• The medulla oblongata contains the cardiac, respiratory, and vasomotor centers and the chemoreceptor trigger zone, which communicates with other structures to initiate vomiting.
• The medulla oblongata is responsible for breathing, maintaining heart rate and blood pressure, swallowing (which can incite regurgitation), urination and defecation, and coordinating lifesaving reflexes.

Hindbrain - The Pons

• The pons connects the cerebral cortex with the medulla oblongata and aids in transferring messages between various parts of the brain and the spinal cord.
• The pons is involved in motor control and sensory analysis, acting as a sensory/motor relay center.
• The pons contains several cranial nerve nuclei, including the trigeminal nerve sensory nucleus (V), abducens nucleus (VI), facial nerve nucleus (VII), and vestibulocochlear nuclei (VIII).
• The pons is involved in controlling autonomic body functions (internal organs such as the heart, stomach, and intestines).
• It regulates the respiratory system via the medulla oblongata, controlling the breathing rate.
• Raphe nuclei, the principal site of serotonin synthesis, are located in the pons.
• Chemicals made in the pons help maintain the sleep-wake cycle.
• The pons activates inhibitory centers in the medulla to inhibit movement during sleep.

Hindbrain - The Cerebellum

• The cerebellum is divided into two hemispheres and is involved in certain reflexes and sensorimotor functions.
• The cerebellum plays a role in motor movement regulation and balance control.
• It coordinates gait and maintains posture, controls muscle tone and voluntary muscle activity, but cannot initiate muscle contraction.
• Damage to the cerebellum can result in cerebral palsy, which are neurological conditions that affect movement and coordination.

Midbrain

• The brainstem includes the midbrain and the two components of the hindbrain: pons and medulla oblongata.

Major Nuclei in the Midbrain

• The midbrain nuclei consist of the substantia nigra, ventral tegmental area, periaqueductal gray, and raphe nuclei.
• Substantia nigra → Dopamine (DA) → Parkinson's disease
• Ventral tegmental area → DA → Reward and addiction
• Periaqueductal gray → Opioid; GABA → Pain
• Raphe nuclei are located in the medulla, pons, and midbrain and lead to Serotonin (5-HT), which is related to antidepressants
• The locus coeruleus is located in the pons and leads to Norepinephrine (NA), which is associated with arousal.
• The midbrain controls many important functions such as the visual and auditory systems and eye movement.
• The midbrain is crucial for hearing and sight.
• The red nucleus and substantia nigra control body movement.

Telencephalon - The Forebrain

• The forebrain, or telencephalon, is split into two sections: the telencephalon and the diencephalon.
• The telencephalon consists of the two cerebral hemispheres of the cerebrum and their interconnections.
• The diencephalon contains two important structures: the thalamus and the hypothalamus.
• The hypothalamus connects with the pituitary gland.

Telencephalon - Cerebral Cortex

• The cerebral cortex is the "gray matter" of the brain, and most information processing occurs there.
• The cortex is a sheet of tissue that makes up the outer layer of the cerebrum (brain).
• Bumps or bulges on the cortex are called gyri (singular: gyrus), and grooves called sulci (singular: sulcus).

Telencephalon - Cerebral Cortex Lobes

• The four lobes of the cerebral cortex are the frontal lobe, parietal lobe, occipital lobe, and temporal lobe.
• The frontal lobe is located in front of the central sulcus and is concerned with reasoning, planning, parts of speech and movement (motor cortex), emotions, and problem-solving.
• The parietal lobe is located behind the central sulcus and is concerned with the perception of stimuli related to touch, pressure, temperature, and pain.
• The occipital lobe is located at the back of the brain, behind the parietal and temporal lobes, and is concerned with many aspects of vision.
• The temporal lobe is located below the lateral fissure and is concerned with the perception and recognition of auditory stimuli (hearing) and memory (hippocampus).

Telencephalon - Limbic System

• The limbic system is a collective name for the parts of the brain that control emotion, motivation, emotional association with memory, and includes the hippocampus, cingulate cortex, mammillary bodies, amygdala, and medial septum and diagonal band of Broca (MS-DBB).

Telencephalon - Hippocampus

• The hippocampus is part of the forebrain, located in the medial temporal lobe, and shaped like a seahorse.
• It consists mainly of grey matter and is associated with short- and long-term memory.
• The hippocampus is one of the first regions of the brain affected in Alzheimer's Disease.

Telencephalon - Basal Forebrain Nuclei

• The basal forebrain nuclei (BFN) are parts of the forebrain situated in front of and below the striatum.
• The BFN include the nucleus basalis of Meynert, the medial septal nucleus, and the diagonal band nuclei.
• BFN neurons project cholinergic neurons to the cerebral cortex and the hippocampal formation and are linked to Alzheimer's disease.

Telencephalon - Cingulate Cortex

• The cingulate gyrus is a curved fold covering the corpus callosum, divided into anterior and posterior parts.
• The anterior cingulate gyrus is divided into dorsal and ventral parts and is involved in processing emotions and regulating behavior.
• It helps regulate autonomic motor function and has low neural activity and few neurons in Post-Traumatic Stress Disorder
• The posterior cingulate gyrus controls movement, spatial orientation, and navigation.

Telencephalon - Amygdala

• The amygdala is located anterior to the hippocampus and is responsible for emotional processing.
• It is associated with conditioned learning, especially fear/anger/rage, and is linked to anxiety, autism, depression, post-traumatic stress disorder, phobias, and binge drinking.
• The olfactory bulb transmits smell information from the nose to the brain and sends olfactory information to be processed in the amygdala, the olfactory cortex, and the hippocampus.

Diencephalon - Thalamus

• The thalamus consists of two large ovoid masses of gray matter situated in the posterior part of the forebrain.
• It is involved in relaying sensory (except smell) and motor signals to the cerebral cortex, controlling muscular movements through connections with the basal ganglia, cerebellum, and motor cortex, and in regulating consciousness, sleep, and alertness.
• Damage to the thalamus can lead to permanent coma.

Diencephalon - Hypothalamus

• The hypothalamus regulates the release of hormones from the pituitary gland and is involved in homeostatic control by exerting control on the pituitary gland.
• It regulates various sensations, such as hunger, thirst, temperature, libido, and controls motivated behavior.
• It is responsible for fighting, fleeing, feeding, and sex.

Pituitary Glands

• The pituitary gland is a small, pea-sized gland found below the hypothalamus.
• The anterior pituitary gland releases growth hormone (GH), thyroid stimulating hormone (TSH), follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin, and adrenocorticotropic hormone (ACTH).
• The posterior pituitary gland releases oxytocin and antidiuretic hormone (known as ADH or vasopressin).

Pituitary and Pineal Glands

• The pineal gland is a small endocrine gland in the vertebrate brain located in the epithalamus between the two cerebral hemispheres.
• The pineal glands produce several important hormones, including melatonin, which affects the modulation of wake/sleep patterns, seasonal functions, and influences sexual development.