The Brain And Cranial Nerves

Spinal Nerve

Functions: processes reflexes Integrates excitatory and inhibitory nerve impulses Provides a "highway" for carrying sensory impulses to the brain and motor impulses from the brain to spinal nerves

Cerebellum

Smooths and coordinates contractions of skeletal muscles. Regulates posture and balance. May have role in cognition and language processing.

The Nervous system

shares with the endocrine system the greates responsibility for maintaining homeostasis. It regulates the body's activities through sensory nerve impulses from receptors that detect changes in both internal and external environments; by interpreting, storing, and integrating the info sent by these impulses; and then responding to the changes via motor nerve output, causing contractions or grandular secretion

Accessory Nerve (XI)

swallowing, head, neck, and shoulder movements If the accessory (XI) nerve is damaged due to conditions such as trauma, lesions, or stroke, the result is paralysis of the sternocleidomastoid and trapezius muscles so that the person is unable to raise the shoulders and has difficulty in turning the head.

Oculomotor Nerve (III)

Sensory function: proprioreception Motor function: movement of eyeball and eyelid; accomadataion of lens; pupillary constriction

Olfactory Nerve (I)

Sensory functions: smell Motor functions: none

Optic Nerve (II)

Sensory functions: visions

Cranial Nerves

12 pairs of nerves that carry messages to and from the brain Functions: the sensory component of a cranial nerve actions potentials from receptors in the head and thorax The motor component cranial nerve carries action potentials that stimulate effectors Cranial nerves originate in the brain and are useful providing info that helps to localize brain injuries

Spinal Nerves

31 pairs of nerves arising from the spinal cord Functions:connects the central nervous system to sensory receptors, muscles, and glands contain both sensory and motor neurons

Pons

Contains sensory and motor tracts. Contains vestibular nuclei (along with medulla) that are part of equilibrium pathway to brain. Pontine respiratory group (together with the medulla) helps control breathing. Contains nuclei of origin for trigeminal (V), abducens (VI), facial (VII), and vestibulocochlear (VIII) nerves.

Midbrain

Contains sensory and motor tracts. Superior colliculi coordinate movements of head, eyes, and trunk in response to visual stimuli.

Hypothalamus

Controls and integrates activities of autonomic nervous system. Produces hormones, including releasing hormones, inhibiting hormones, oxytocin, and antidiuretic hormone (ADH). Regulates emotional and behavioral patterns (together with limbic system). Contains feeding and satiety centers (regulate eating), thirst center (regulates drinking), and suprachiasmatic nucleus (regulates circadian rhythms). Controls body temperature by serving as body's thermostat.

Vestibulocochlear nerve VIII

It is a sensory cranial nerve and has two branches, the vestibular branch and the cochlear branch. The vestibular branch carries impulses for equilibrium and the cochlear branch carries impulses for hearing. Injury to the vestibular branch of the vestibulocochlear (VIII) nerve may cause vertigo (a subjective feeling that one's own body or the environment is rotating),

Facial Nerve (VII)

Its sensory axons extend from the taste buds of the anterior two-thirds of the tongue, which enter the temporal bone to join the facial nerve The sensory portion of the facial nerve also contains axons from skin in the ear canal that relay touch, pain, and thermal sensations.

Spinal Nerves are

Medulla oblongota Cervical nerves dermatomes thoracic nerves lumbar nerves sacral nerves coccygeal nerves

Medulla oblongata

Part of the brainstem that controls vital life-sustaining functions such as heartbeat, breathing, blood pressure, and digestion.

Thalamus

Relays almost all sensory input to cerebral cortex. Contributes to motor functions by transmitting information from cerebellum and basal nuclei to primary motor area of cerebral cortex. Plays role in maintenance of consciousness.

Cerebrum

Sensory areas of cerebral cortex are involved in perception of sensory information; motor areas control execution of voluntary movements; association areas deal with more complex integrative functions such as memory, personality traits, and intelligence. Basal nuclei help initiate and terminate movements, suppress unwanted movements, and regulate muscle tone. Limbic system promotes range of emotions, including pleasure, pain, docility, affection, fear, and anger.

Glossopharyngeal nerve IX

Sensory axons of the glossopharyngeal nerve arise from (1) taste buds on the posterior one-third of the tongue, (2) proprioceptors from some swallowing muscles supplied by the motor portion, (3) baroreceptors (pressure-monitoring receptors) in the carotid sinus that monitor blood pressure, (4) chemoreceptors (receptors that monitor blood levels of oxygen and carbon dioxide) in the carotid bodies near the carotid arteries and aortic bodies near the arch of the aorta and (5) the external ear to convey touch, pain, and thermal (heat and cold) sensations.

Hypoglossal Nerve (XII)

These axons conduct nerve impulses for speech and swallowing. The sensory axons do not return to the brain in the hypoglossal nerve. Instead, sensory axons that originate from proprioceptors in the tongue muscles begin their course toward the brain in the hypoglossal nerve but leave the nerve to join cervical spinal nerves and end in the medulla oblongata, again entering the central nervous system via posterior roots of cervical spinal nerves.

Nerves

are bundles containing hundreds of thousands of axons, part of the basic neural cell, the neuron Functions: cell bodies and dendrites receive input info the axon conducts nerve impulses toward another neuron, a muscle cell or a gland cell synaptic vesicles contained an synaptic end bulbs contain neurotransmitters which, when released, promote communication from one to another cell

Abducens Nerve (VI)

eye movement The abducens nerve is so named because nerve impulses cause abduction (lateral rotation) of the eyeball.

Trochlear Nerve (IV)

eye movement s the smallest of the 12 cranial nerves and is the only one that arises from the posterior aspect of the brainstem.

Vagus Nerve X

is a mixed cranial nerve that is distributed from the head and neck into the thorax and abdomen, Sensory axons in the vagus nerve arise from the skin of the external ear for touch, pain, and thermal sensations; a few taste buds in the epiglottis and pharynx; and proprioceptors in muscles of the neck and throat. he majority of sensory neurons come from visceral sensory receptors in most organs of the thoracic and abdominal cavities that convey sensations (such as hunger, fullness, and discomfort) from these organs.