The Last Notes Hi Folks! We’re almost finished now and it looks like we won’t have time for the special senses (gustation, olfaction, vision, balance and hearing). Please read pages 575-597 in the textbook about the eye and ear. Pay special attention to structures you saw on the ear and eye models in lab. See table 15.7 (p. 474) about the cranial nerves. Know for each nerve whether it is sensory, motor, or both. Also learn each nerve’s major areas of innervation, including autonomic motor innervation.

Hypothalamus The hypothalamus is the anteroinferior region of the diencephalon. The infundibulum attaches it to the pituitary gland. Functions: Master control of autonomic nervous system functions. Master control of the endocrine system. Regulation of body temperature. Some control of emotional behavior. Control of food and water appetites.

Hypothalamus

Brainstem

Mesencephalon The mesencephalon (midbrain) is the superior portion of the brainstem. The cerebral aqueduct extends through the mesencephalon and connects the third and fourth ventricles. Somatic motor axons descend from the primary motor cortex through the cerebral peduncles, located on the anterolateral surfaces of the mesencephalon, to the spinal cord.

Mesencephalon The substantia nigra houses neurons which produce the neurotransmitter dopamine. This chemical affects brain processes that control movement and the ability to experience pleasure and pain. Degeneration of cells in the substantia nigra leads to Parkinson’s disease. The tegmentum contains the red nuclei which issue involuntary motor commands to postural muscles. The tectal plate (or corpora quadrigemina) contains the superior colliculi (visual reflex centers) and the inferior colliculi (auditory reflex centers).

Mesencephalon

Pons The middle cerebellar peduncles contain fibers that connect the pons to the cerebellum. The pons houses two autonomic respiratory centers: the pneumotaxic center and the apneustic center. These centers regulate the rate and depth of breathing.

Pons

Medulla Oblongata The medulla oblongata, the most inferior part of the brainstem, is formed from the myelencephalon. All communication between the brain and spinal cord involves tracts that ascend or descend through the medulla oblongata. The anterior surface exhibits two longitudinal ridges called the pyramids which contain motor tracts. Most of the axons in the pyramids cross to the opposite side at a point called the decussation of the pyramids, so that each cerebral hemisphere controls voluntary movement on the opposite side of the body.

Medulla Oblongata Lateral to each pyramid is an inferior olivary nucleus. These nuclei relay ascending sensory information to the cerebral cortex. The medulla oblongata contains several autonomic nuclei which include the: Cardiac center -- regulates heart rate and force of contraction. Vasomotor center -- controls blood pressure by regulating the arterial smooth muscle. Respiratory center -- regulates respiratory rate and is influenced by the apneustic and pneumotaxic centers of the pons. Other nuclei here are involved in coughing, sneezing, salivation, swallowing, gagging, and vomiting (fun, huh?).

Medulla Oblongata

Cerebellum Has a complex, highly folded gray matter cortex. Folds here are called folia. Composed of left and right cerebellar hemispheres. Along the midline is a narrow band between hemispheres called the vermis. The vermis receives and relays body (torso) position and balance information to other brain areas. Coordinates and fine-tunes all skeletal muscle movements. Stores memories of learned movement patterns. Adjusts skeletal muscle activity to maintain equilibrium and posture.

Cerebellum

Limbic System The structures of the limbic system form a ring around around the diencephalon. The limbic system is composed of multiple cerebral and diencephalic structures that collectively process and experience emotions. The limbic system affects memory formation with relevance to emotional states.

Limbic System Brain structures recognized to be part of the limbic system: Cingulate gyrus -- Receives input from the other components of the limbic system. Hippocampus -- It is essential in storing memories and forming long-term memories. Amygdaloid body (or amygdala) -- involved in several aspects of intense emotion, especially fear. Olfactory cortex -- particular odors can provoke emotions. Fornix -- thin tract of white matter that connects hippocampus with other limbic system structures. Various nuclei in the diencephalon (anterior thalamic nuclei, habenular nuclei, septal nuclei, mammillary bodies) -- interconnect other parts of the limbic system and contribute to overall function.

Limbic System

Cranial Nerves