Nervous System PDF

# Nervous System ## Organization of the Nervous System There are Two Anatomical Divisions: * **Central nervous system (CNS):** * Brain * Spinal cord * **Peripheral nervous system (PNS):** * All the neural tissue outside CNS * Afferent division (sensory input) * Efferent divi...

# Nervous System ## Organization of the Nervous System There are Two Anatomical Divisions: * **Central nervous system (CNS):** * Brain * Spinal cord * **Peripheral nervous system (PNS):** * All the neural tissue outside CNS * Afferent division (sensory input) * Efferent division (motor output) * **Somatic nervous system** * **Autonomic nervous system:** * Sympathetic ANS * Parasympathetic ANC ## Central Nervous System The central nervous system (CNS) is composed of the brain and spinal cord. These neurons cannot regenerate if damaged. ### Brain: * Mass of nerve tissue * Protected by membranes & the cranium or skull ### Spinal Cord: * Goes down back of body from Medulla Oblongata * Surrounded and protected by vertebrae * Responsible for reflex actions * Carries sensory and motor messages * Spinal nerves are named for the region from which they arise ## Principal Parts of the Brain 1. Cerebrum 2. Diencephalon * Thalamus * Hypothalamus 3. Cerebellum 4. Brainstem * Medulla * Pons * Midbrain ## Cerebral Hemispheres (Cerebrum) * Largest section of the brain (Include more than half of the brain mass) * Responsible for: reasoning, thought, memory, speaking, sensation, sight, hearing, voluntary body movement * Paired (left and right) superior parts of the brain divided by falx cerebri * The surface is made of ridges (gyri) and grooves (sulci) * Fissures (deep grooves) divide the cerebrum into lobes. Surface lobes of the cerebrum: 1. Frontal lobe. 2. Parietal lobe. 3. Temporal lobe. 4. Occipital lobe. ## Diencephalon: * Sits on top of the brain stem * Enclosed by the cerebral hemispheres * Made of three parts: 1. Thalamus 2. Hypothalamus 3. Epithalamus ## Cerebellum: * Responsible for: * coordination of muscles, balance, posture, & muscle tone ## Brain Stem: * Attaches to the spinal cord * Parts of the brain stem: * Midbrain * Pons * Medulla oblongata ### Midbrain: * Mostly composed of tracts of nerve fibers, responsible for: * conducting impulses between brain parts * certain eye & hearing reflexes ### Pons: * The bulging center part of the brain stem * Mostly composed of fiber tracts * Responsible for: * conducting messages to other parts of the brain * Reflex actions such as chewing, production of saliva ### Medulla Oblongata: * Lowest part of brain stem, connects to the spinal cord * Responsible for: * regulating heart beat, respirations, swallowing, coughing and blood pressure. ## Meninges * Covers and protects the brain and spinal cord * Consists of 3 membranes: 1. **Dura mater:** thick, tough outer layer 2. **Arachnoid membrane:** middle delicate weblike layer 3. **Pia mater:** inner most layer with blood vessels to nourish the nerves ## Ventricles * Four hallow spaces located in the middle of the brain. * Connected to each other * Filled with fluid called cerebrospinal fluid ## Cerebrospinal Fluid * Circulates continuously from choroid plexus in lateral ventricle * Serves as shock absorber to protect brain and spinal cord. * Carries nutrients to parts of brain and spinal cord * helps remove metabolic products & wastes * after circulation, absorbed into the blood vessels of the dura mater. ## Peripheral Nervous System * Made of all nerves outside the brain and spinal cord (PNS) is made up of peripheral nerves that connect the CNS to the rest of the body. These neurons can regenerate if damaged. * 12 pairs of cranial nerves * 31 pairs of spinal nerves ## Peripheral Nervous System * PNS can be subdivided into 2 divisions: 1. **Autonomic** * Cranial & spinal nerves connecting CNS to heart, stomach, intestines, glands * Controls unconscious activities 2. **Somatic** * Cranial & spinal nerves connecting CNS to skin & skeletal muscles * Oversees conscious activities ## Cranial Nerves: * 12 pairs & their branches * Some responsible for special senses: sight, hearing, taste, smell * Others receive sensations: touch, pressure, pain, temperature ## Cranial Nerve Summary | Location | Nerve | Function | | --- | --- | --- | | Cerebrum | Olfactory (CN I) | Sense of smell | | Cerebrum | Optic (CN II) | Sense of vision | | Midbrain | Oculomotor (CN III) | Eye movement | | Midbrain | Trochlear (CN IV) | Eye movement | | Pons | Trigeminal (CN V) | Eye, jaws sensation/movement | | Pons | Abducens (CN VI) | Eye movement | | Pons | Facial (CN VII) | Face, scalp, tongue sensation/movement | | Pons | Vestibulocochlear (CN VIII) | Hearing, balance | | Medulla Oblongata | Glossopharyngeal (CN IX) | Taste, swallowing | | Medulla Oblongata | Vagus (CN X) | Autonomic control of viscera | | Medulla Oblongata | Accessory (CN XI) | Swallowing, pectoral girdle movement | | Medulla Oblongata | Hypoglossal (CN XII) | Tongue movement | ## Spinal Nerves: * 31 pairs & their branches * carries messages to & from the spinal cord * Both sensory and motor nerves 31 spinal nerves: * 8 cervical * 12 thoracic * 5 lumbar * 5 sacral * 1 coccygeal ## Autonomic Nervous System * Helps maintain a balance in involuntary functions of the body. But allows the body to react in times of emergency. Two divisions of ANS: 1. **Sympathetic nervous system:** acts in emergency. 2. **Parasympathetic nervous system:** counter acts the sympathetic ns after the emergency