Parts of the brain

Telencephalon

• Refers to the embryonic structure, from which the mature "cerebrum" develops.
• dorsal telencephalon, or pallium, develops into the cerebral cortex,
• ventral telencephalon, or subpallium, Becomes the basal ganglia.

5 Functions

• Movement
• Sensory processing
• Olfaction
• Learning and memory
• Language and communication

The cerebrum is composed of the following sub-regions:

1. cerebral cortex

• a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain.
• It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness.

2. Limbic system (or Paleomammalian brain)

• support a variety of functions including emotion, behavior, long term memory, and olfaction.

Part of the limbic system:

• Amygdala: Involved in signaling the cortex of motivationally significant stimuli such as those related to reward and fear in addition to social functions such as mating.
• Hippocampus:Required for the formation of long-term memories and implicated in maintenance of cognitive maps for navigation.
• Parahippocampal gyrus: Plays a role in the formation of spatial memory
• Cingulate gyrus: Autonomic functions regulating heart rate, blood pressure and cognitive and attentional processing
• Fornix: carries signals from the hippocampus to the mammillary bodies and septal nuclei.
• Hypothalamus: Regulates the autonomic nervous system via hormone production and release. Affects and regulates blood pressure, heart rate, hunger, thirst, sexual arousal, and the sleep/wake cycle
• Thalamus: The "relay station" to the cerebral cortex.

In addition, these structures are sometimes also considered to be part of the limbic system:

• Mammillary body: Important for the formation of memory
• Pituitary gland:^[4] secretes hormones regulating homeostasis
• Dentate gyrus:^[5] thought to contribute to new memories and to regulate happiness.
• Entorhinal cortex: Important memory and associative components.
• Piriform cortex:^[6] The function of which relates to the olfactory system.
• Fornicate gyrus: Region encompassing the cingulate, hippocampus, and parahippocampal gyrus
• Olfactory bulb: Olfactory sensory input
• Nucleus accumbens: Involved in reward, pleasure, and addiction
• Orbitofrontal cortex: Required for decision making.

3. Basal ganglia

• associated with a variety of functions, including motor control and learning.

Putamen

• regulate movements and influence various types of learning.
• These include controlling motor learning, motor performance and tasks, motor preparation, specifying amplitudes of movement, and movement sequences.
• It employs dopamine to perform its functions.
• Some neurologists hypothesize that the putamen also plays a role in the selection of movement (e.g. Tourette Syndrome) and the "automatic" performance of previously learned movements (e.g. Parkinson’s disease).

tectum

• (Latin: roof) is a region of the brain, specifically the dorsal part of the mesencephalon (midbrain).
• This is contrasted with the tegmentum, which refers to the region ventral to the ventricular system.
• It is responsible for auditory and visual reflexes.

Tegmentum

• located between the ventricular system and distinctive basal or ventral structures at each level.
• It forms the floor of the midbrain whereas the tectum forms the ceiling.
• It is a multisynaptic network of neurons that is involved in many unconscious homeostatic and reflexive pathways.

Reticular formation

• A part of the brain that is involved in actions such as awaking/sleeping cycle, and filtering incoming stimuli to discriminate irrelevant background stimuli.^[1]
• It is essential for governing some of the basic functions of higher organisms, and is one of the phylogenetically oldest portions of the brain.

The reticular formation consists of more than 100 small neural networks, with varied functions including the following:

1. Somatic motor control - Some motor neurons send their axons to the reticular formation nuclei, giving rise to the reticulospinal tracts of the spinal cord. These tracts function in maintaining tone, balance, and posture--especially during body movements. The reticular formation also relays eye and ear signals to the cerebellum so that the cerebellum can integrate visual, auditory, and vestibular stimuli in motor coordination. Other motor nuclei include gaze centers, which enable the eyes to track and fixate objects, and central pattern generators, which produce rhythmic signals to the muscles of breathing and swallowing.

2. Cardiovascular control - The reticular formation includes the cardiac and vasomotor centers of the medulla oblongata.

3. Pain modulation - The reticular formation is one means by which pain signals from the lower body reach the cerebral cortex. It is also the origin of the descending analgesic pathways. The nerve fibers in these pathways act in the spinal cord to block the transmission of some pain signals to the brain.

4. Sleep and consciousness - The reticular formation has projections to the thalamus and cerebral cortex that allow it to exert some control over which sensory signals reach the cerebrum and come to our conscious attention. It plays a central role in states of consciousness like alertness and sleep. Injury to the reticular formation can result in irreversible coma.

5. Habituation - This is a process in which the brain learns to ignore repetitive, meaningless stimuli while remaining sensitive to others. A good example of this is when a person can sleep through loud traffic in a large city, but is awakened promptly due to the sound of an alarm or crying baby. Reticular formation nuclei that modulate activity of the cerebral cortex are called the reticular activating system or extrathalamic control modulatory system.

Cerebellum

^· (Latin for little brain) is a region of the brain that plays an important role in motor control.

^· also involved in some cognitive functions such as attention and language,

^· and probably in some emotional functions such as regulating fear and pleasure responses, but it is its function in movement that is most clearly understood.

^· does not initiate movement, but it contributes to coordination, precision, and accurate timing.

^· receives input from sensory systems and from other parts of the brain and spinal cord, and integrates these inputs to fine tune motor activity.

^· Because of this fine-tuning function, damage to the cerebellum does not cause paralysis, but instead produces disorders in fine movement, equilibrium, posture, and motor learning.

Pons

• contains nuclei that relay signals from the cerebrum to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.
• Within the pons is the pneumotaxic center, a nucleus in the pons that regulates the change from inspiration to expiration.

medulla oblongata

• contains the cardiac, respiratory, vomiting and vasomotor centers and deals with autonomic functions, such as breathing, heart rate and blood pressure.
• controls autonomic functions, and relays nerve signals between the brain and spinal cord.
• also responsible for controlling several major points and autonomic functions of the body:

central sulcus

§ Also called the central fissure,

§ it was originally called the fissure of Rolando or the Rolandic fissure, after Luigi Rolando.

§ The central sulcus is a prominent landmark of the brain, separating the parietal lobe from the frontal lobe and the primary motor cortex from the primary somatosensory cortex.

lateral sulcus

• (also called Sylvian fissure or lateral fissure)
• It divides the frontal lobe and parietal lobe above from the temporal lobe below.
• It is in both hemispheres of the brain but is longer in the left hemisphere.

Peripheral Nervous System, or PNS,

• consists of the nerves and ganglia outside of the brain and the spinal cord.^[1]
• The main function of the PNS is to connect the central nervous system (CNS) to the limb and organ.
• Unlike the CNS, the PNS is not protected by bone or by the blood-brain barrier, leaving it exposed to toxins and mechanical injuries.
• is divided into the somatic nervous system and the autonomic nervous system; some textbooks also include sensory systems.

sensory system

• responsible for processing sensory information.
• consists of sensory receptors, neural pathways, and parts of the brain involved in sensory perception.
• Commonly recognized sensory systems are those for vision, hearing, somatic sensation (touch), taste and olfaction (smell).
• senses are transducers from the physical world to the realm of the mind.

somatic nervous system (SNS)

• voluntary control of body movements through the action of skeletal muscles, and with reception of external stimuli, which helps keep the body in touch with its surroundings (e.g., touch, hearing, and sight).
• The system includes all the neurons connected with skeletal muscles, skin, and sense organs. The somatic nervous system consists of efferent nerves responsible for sending brain signals for muscle contraction.

autonomic nervous system (ANS or visceral nervous system)

• acts as a control system functioning largely below the level of consciousness, and controls visceral functions.
• affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, micturition (urination), and sexual arousal.
• Whereas most of its actions are involuntary, some, such as breathing, work in tandem with the conscious mind.

parasympathetic nervous system (PSNS)

• ANS sends fibers to three tissues: cardiac muscle, smooth muscle, or glandular tissue. This stimulation, sympathetic or parasympathetic, is to control smooth muscle contraction, regulate cardiac muscle, or stimulate or inhibit glandular secretion.
• The actions of the parasympathetic nervous system can be summarized as "rest and digest".

sympathetic nervous system (SNS)

• Its general action is to mobilize the body's resources under stress; to induce the flight-or-fight response.
• constantly active at a basal level in order to maintain homeostasis.