The Central Nervous System (CNS) – The Brain and Spinal Cord Anatomy Ch. 7 Part 2 The Central Nervous System (CNS) – The Brain and Spinal Cord

Cerebrum Contains 2 divisions called the cerebral hemispheres. Largest part of the brain Contains 4 lobes: frontal, parietal, temporal, occipital Surface features: Gyri ridges Sulci shallow grooves divide the lobes of the brain Fissures deep grooves divide the right and left hemispheres

Cerebral Cortex Outer region of the cerebrum Composed of gray matter Functions: Speech Memory logical and emotional responses Consciousness interpretation of sensations voluntary movement.

Functional Regions of the Cerebral Cortex Primary Somatic Sensory Area Located in the parietal lobe Interprets information from sensory receptors All sensory pathways are crossed Specialized cortex areas Occipital lobe: vision Temporal lobe: smell and hearing

Primary Motor Area Broca’s Area Located in the frontal lobe Movements of skeletal muscles All motor pathways are crossed Broca’s Area Specialized area that is involved in ability to speak Left side of the frontal lobe

Anterior Association Area Frontal lobe: reasoning and behavior Frontal and temporal lobes: complex memories Posterior Association Area Combination of lobes: faces and patterns

Gray matter makes up the cortex of the cerebrum and white matter makes up the deeper regions. The 2 hemispheres of the cerebrum are connected by a large nerve tract called the corpus callosum.

Diencephalon Sits on top of the brain stem Enclosed by the cerebral hemispheres Divided into 3 regions: Thalamus Relay station for sensory impulses passing to the sensory cortex Provides a crude recognition of whether a sensation will be pleasant or unpleasant.

Hypothalamus Epithalamus Plays a role in body temperature, water balance, and metabolism Center for many drives and emotions Regulates the pituitary gland Epithalamus Contains the pineal gland and capillaries that form CSF.

Limbic System Plays a role in emotions and memory Found between the temporal lobes on both sides of the thalamus. Closely associated with the diencephalon. Consists of the amygdala and hippocampus Amygdala: the emotion center of the brain Hippocampus: formation of memories

Brain Stem Produces behaviors necessary for survival Controls activities such as breathing and blood pressure. Composed of 3 regions

Midbrain Pons Medulla Oblongata connects ventricles in the brain which contain CSF conducts impulses contains reflex centers for vision and hearing Pons Controls breathing Medulla Oblongata Merges into the spinal cord Contains centers that control heart rate, blood pressure, breathing, and swallowing.

Reticular Formation entire length of the brain stem Motor control of organs Consciousness Wake/sleep cycles

Cerebellum Below the occipital lobe Similar structure to cerebrum Hemispheres are connected by the vermis Assists with skeletal muscle activity Controls balance

Protection Meninges 3 membranes that cover and protect the CNS Dura Mater Outermost layer Means tough mother Double layered

Arachnoid Mater Pia mater Subarachnoid space Middle layer Weblike Means gentle mother Inner layers that clings tightly to the brain and spinal cord Subarachnoid space Found between the arachnoid and pia mater Contains CSF

Cerebrospinal Fluid (CSF) Watery substance similar to blood plasma Continually formed from blood Forms a watery cushion that protects nervous tissue from trauma Continually circulates inside the brain in the ventricles and in the subarachnoid space

Blood-Brain Barrier Composed of the least permeable capillaries in the whole body Only water, glucose, and essential amino acids pass through easily Metabolic wastes such as urea, toxins, proteins, and most drugs are prevented from entering

Nonessential amino acids and potassium are not only prevented from entering but are also actively pumped from the brain. However this barrier is useless against fats, respiratory gases, and fat soluble molecules. This explains why alcohol, nicotine, and anesthetics can affect the brain.

The Spinal Cord Provides a 2 way conduction pathway to and from the brain Major reflex center Enclosed within the vertebral column Protected by the same 3 layers of meninges as the brain.

Spinal Nerves Humans have 31 pairs of spinal nerves The spinal cord is enlarged in the cervical and lumbar regions. Cervical: upper limbs Lumbar: lower limbs

Anatomy of the Spinal Cord The gray matter is found on the inside of the spinal cord and is shaped like a butterfly. The gray matter has 2 dorsal horns and 2 ventral horns Dorsal horns: Sensory input Ventral horns: Motor output The gray matter surrounds a central canal which contains CSF.

White matter surrounds the gray matter of the spinal cord The white matter contains myelinated fiber tracts Dorsal tracts sensory (afferent) information ascending Lateral and ventral tracts Sensory (afferent) and motor (efferent) information Ascending and descending

Cranial Nerves 12 pairs primarily serve the head and neck Only the vagus nerve extends to the thoracic and abdominal cavities. Cranial nerves are numbered and the name reveals the most important structures they control. All cranial nerves have sensory and motor functions but 3. The 3 that are only sensory are the optic, olfactory, and vestibulocochlear

General Description of the Cranial Nerves I – Olfactory: smell II – Optic: vision III – Occulomotor: movement of the eye IV – Trochlear: movement of the eye V – Trigeminal: face, nose, mouth, chewing VI – Abducens: movement of the eye VII – Facial: face, glands, taste buds VIII – Vestibulocochlear: balance, hearing IX – Glossopharyngeal: throat, taste buds, artery pressure X – Vagus: throat, larynx, abdominal and thoracic organs XI – Accessory: sternocleidomastoid and trapezius XII – Hypoglossal: tongue

Spinal Nerves 31 pairs Named for the region of the spinal cord from which they arise. Groups of spinal nerves that service the same area are called plexuses.

Spinal Nerve Plexuses Cervical Plexus Brachial Plexus Lumbar Plexus C1 – C5 Serves the head and neck Brachial Plexus C5 – C8 and T1 Shoulders and arms Lumbar Plexus L1 – L4 Abdominal and pelvic area Sacral Plexus L5 and S1 – S4 legs

T2 – T12 Do not form plexuses Intercostal nerves Organs of the thorax and abdomen

Autonomic Nervous System