Nervous System

Nervous System : 

Nervous System Module # 5

Nervous System : 

Nervous System As the most complex system, the nervous system serves as the body control center and communications electrical-chemical wiring network The nervous system integrates countless bits of information and generates appropriate reactions by sending electrochemical impulses through nerves to effectors organs such as muscles and glands

Parts : 

Parts Consists of: Central Nervous System The Brain The Spinal Cord Peripheral Nervous System Cranial Nerves Spinal Nerves

Parts : 

Parts

Brain : 

Brain The brain has billions of neurons that receive, analyze, and store information about internal and external conditions. It is also the source of conscious and unconscious thoughts, moods, and emotions.

Parts of Brain : 

Parts of Brain Four major brain divisions govern its main functions: The cerebrum The diencephalons The cerebellum The brain stem

Old Classification : 

Old Classification Fore-Brain Cerebrum Thalamus Hypothalamus Mid- Brain Cerebral Puduncles Aquiduct Peri Aquiductal Area Hind-Brain Cerebellum Pons Medulla

Cerebrum : 

Cerebrum The cerebrum is the large rounded area that divides into left and right hemispheres (halves) at a fissure (deep groove). The hemispheres communicate with each other through the corpus callosum (bundle of fibers between the hemispheres) Surprisingly, each hemisphere controls muscles and glands on the opposite side of the body. Comprising 85 percent of total brain weight, The cerebrum controls language, conscious thought, hearing, somatosensory functions (sense of touch), memory, personality development, and vision.

Cerebrum : 

Cerebrum

Cerebrum : 

Cerebrum Gray matter (unmylinated nerve cell bodies) composes the cerebral cortex (outer portion of the cerebrum). Beneath the cortex lies White matter (mylinated axons). During embryonic development, The cortex folds upon itself to form gyri (folds) and sulci (shallow grooves) so that more gray matter can reside within the skull cavity.

Diencephalon : 

Diencephalon The diencephalon forms the central part of the brain. It consists of three bilaterally symmetrical structures: hypothalamus thalamus epithalamus.

The hypothalamus : 

The hypothalamus The hypothalamus 'master switchboard' resides in the brain stem upper end. It controls many body activities that affect homeostasis (maintenance of a stable internal environment in the body).  The hypothalamus is the main neural control center (brain part that controls endocrine glands).  The pituitary gland lies just below the hypothalamus. The pituitary gland is a small endocrine gland that secretes a variety of hormones (organic chemicals that regulate the body's physiological processes). Together hypothalamus and pituitary gland they are called the neuroendocrine system.

The hypothalamus : 

The hypothalamus

The thalamus : 

The thalamus The thalamus is a relay and preprocessing station for the many nerve impulses that pass through it. Impulses carrying similar messages are grouped in the thalamus, then relayed to the appropriate brain areas. It is the sensory center of the body

The epithalamus : 

The epithalamus The epithalamus is the most dorsal (posterior) portion of the diencephalon. It contains a vascular network involved in cerebrospinal fluid production. Extending from the epithalamus posteriorly is the pineal body, or pineal gland. Its function is not yet fully understood; it is thought to control body rhythms.

Cerebellum : 

Cerebellum At the rear of the brain is the cerebellum. The cerebellum is similar to the cerebrum: each has hemispheres that control the opposite side of the body and are covered by gray matter and surface folds. In the cerebellum, the folds are called folia; in the cerebrum, sulci.   The vermis (central constricted area) connects the hemispheres. The cerebellum controls balance, posture, and coordination.

Brain Stem : 

Brain Stem The brain stem connects the cerebrum and cerebellum to the spinal cord. Its superior portion, the midbrain, is the center for visual and auditory reflexes The middle section, the pons, bridges the cerebellum hemispheres and higher brain centers with the spinal cord. Below the pons lies the medulla oblongata; it contains the control centers for swallowing, breathing, digestion, and heartbeat.

Brain : 

Brain

Spinal Cord : 

Spinal Cord The spinal cord is a continuation of the brain stem. It is long, cylindrical, and passes through a tunnel in the vertebrae called the vertebral canal. The spinal cord has many spinal segments, which are spinal cord regions from which pairs (one per segment) of spinal nerves arise. Like the cerebrum and cerebellum, the spinal cord has gray and white matter, although here the white matter is on the outside. The spinal cord carries messages between the CNS and the rest of the body, and mediates numerous spinal reflexes such as the knee-jerk reflex.

Meninges : 

Meninges three connective tissue layers, protect the brain and spinal cord. The outermost dura The arachnoid middle layer The Pia in contact with brain or spinal cord.

Cerebrospinal fluid : 

Cerebrospinal fluid Cerebrospinal fluid, surrounds the brain and spinal cord. The brain floats within the cerebrospinal fluid, which prevents against crushing under its own weight and cushions against shocks from walking, jumping, and running.

Peripheral Nervous System : 

Peripheral Nervous System The Peripheral Nervous System has two parts: The somatic nervous system (voluntary) The autonomic nervous system (involuntary)

Somatic nervous system : 

Somatic nervous system The somatic nervous system, or voluntary nervous system, enables humans to react consciously to environmental changes. It includes 31 pairs of spinal nerves and 12 pairs of cranial nerves. This system controls movements of skeletal (voluntary) muscles.

Cranial Nerves : 

Cranial Nerves

Spinal Nerves : 

Spinal Nerves

Reflexes : 

Reflexes Reflexes are quick because they involve few neurons. Reflexes are either somatic (resulting in contraction of skeletal muscle) or autonomic (activation of smooth and cardiac muscle).  All reflex arcs have five basic elements: A receptor Sensory neuron Integration center (CNS) Motor neuron Effector.

Nucleus in CNS : 

Nucleus in CNS In neuroanatomy, a nucleus is a central nervous system structure that is composed mainly of gray matter, and that acts as a hub or transit point for electrical signals in a single neural subsystem. The lateral geniculate nucleus mediates signals in the vertebrate visual system. The vestibular nucleus stores head motion information and guides eye movements via the vestibule-ocular reflex. The raphe nuclei, which are involved in sleep, and The suprachiasmatic nucleus, which controls the circadian rhythm. All the nerve cell axons terminating on a nucleus tend to employ the same neurotransmitter at their synapses

Neural Pathway : 

Neural Pathway A neural pathway is a neural tract connecting one part of the nervous system with another, usually consisting of bundles of elongated, myelin-insulated neurons, known collectively as white matter. Neural pathways serve to connect relatively distant areas of the brain or nervous system, compared to the local communication of grey matter

Spinothalamic tract : 

Spinothalamic tract The spinothalamic tract is a sensory pathway originating in the spinal cord. It transmits information to the thalamus about pain, temperature, itch and crude touch. The pathway decussates at the level of the spinal cord, rather than in the brainstem like the posterior column-medial lemniscus pathway and corticospinal tract.

Spinothalamic tractContd. : 

Spinothalamic tractContd.

End… : 

End… Module # 5