The Brain CH 8- BIO 160

Cerebrospinal Fluid (CSF)

formed by the filtartion of blood plasma by the choroid plexus; clear, colorless fluid circulates through the ventricles into the central canal and around the brain and spinal cord and flows through the subarachnoid space. It cushions the brain and spinal cord from shock, transports nurtrients, and removes metabolic waste; Sample can be taken of CSF at subarachnoid space by lumbar puncture (spinal tap).

Gray matter of cerebrum

found in the superficial layer of the neural cortex and in deeper basal nuclei (center).

Functional areas of Cerebrum

1. Motor sensory 2. Association areas 3. Central processing centers

Cranial nerves

12 pairs of nerves (part of PNS) that connect to the brain and provide motor, sensory, and/or autonomic (parasympathetic) function.

Abducens Nerve (VI)

Abducts the eyeball causing it to rotate laterally, away from the midline of the body; Motor to one eye muscle.

Vestibulocochlear Nerve (VIII)

Acoustic nerves that monitor sensory receptors of inner ear. *Each vestibulocochlear nerve has 2 components: 1) a vestibular nerve- equilibrium, balance 2) the cochlear nerve- sense of heraing.

Temporal lobe (motor & sensory)

Auditory cortex & olfactory cortex- receive info about hearing & smell, respectively.

Cerebellum

Automatic processing center referred to as the "little brain" attached to the rear of the brainstem via cerebral peduncles; separated from cerebrum by transverse fissure. *2 Important functions- maintain balance & programming & fine tuning movements controlled at conscious and subconscious levels. *Gray matter folia surrounds white matter arbor vitae.

Principal divisions of the brain

Brainstem, medulla oblongata, pons, midbrain, diencephalon, thalamus, hypothalamus, epithalamus (pineal gland), cerebrum, & cerebellum.

Parietal lobe (motor & sensory)

Contains: -Post central gryrus- forms the posterior margin of central sulcus & its surface contains primary sensory cortex. -Primary sensory cortex- neurons here receive somatic sensory info from touch, pressure, pain, and temperature receptors. *Brain stem nuclei sends sensory info to primary sensory cortex.

Prefrontal cortex

Coordinates info from association areas of entire cortex, interprets ongoing events, & predicts future situations or consequences. *Frustration, tension, anxiety- generated here.

White matter of cerebrum

Deep to cortex; Consists of 3 types of fibers (pathways for communication) : Projection Fibers, Association Fibers, Commissural Fibers.

Occulomotor Nerve (III)

Eyeball movement; ANS for accomodation of lens & pupil constriction; Control the amount of light entering the and the shape of the lens.

Limbic System

Group of nuclei and centers in cerebrum and diencephalon that are involved with emotional states, memories (long term), & behavioral drives. Functionally related areas in cerebrum, thalamus, & hypothalamus -linking conscious areas of cerebrum with unconscious areas of brainstem.

Diencephalon

Includes: thalamus, epithalamus (pineal gland), and hypothalamus.

Association Areas

Interpret incoming data or coordinate a motor response (movement); These areas of the cerebral cortex are not involved in the processing of sensory or motor information. Somatic motor association- (premotor cortex) monitors activity in and relays info/instructions to the primary sensory cortex. Visual association area.

Trigeminal Nerve (V)

Largest of cranial nerves. Sensory: orbital structures, nasal cavity, skin of forehead, eyelids, eyebrows, nose, lips, gums and teeth; cheeck, palate, pharynx, and tongue. Motor: chewing muscles (temporalis, masseter, pteryoids) 3 branches: opthalmic, maxillary, mandibular.

Components of Brainstem

Medulla oblongata, pons, & midbrain

Accessory Nerve (XI)

Motor Nerve that innervate structures in the neck & back. Motor to swallowing muscles- trapezius & sternocleidomastoid and muscle of pharynx; Voluntary muscles of palate, pharynx, & larynx (w/vagus nerve)

Olfactory bulb (cranial nerve I)

Only cranial nerves attached to cerebrum; carry special sensory info responsible for smell.

Hypoglossal Nerve (XII)

Provides voluntary control over the skeletal muscles of the tongue; Motor to tongue muscles; tongue movement

Wernicke's area (general interpretive area)

Receives info from all sensory association areas. *Plays essential role in personality by integrating sensory info & coordinating access to complex visual & auditory memories. *Controls language reception-a brain area involved in language comprehension and expression. *Present in only one hemisphere-usually in the left

Broca's area

Regulates the patters of breathing and vocalization required for normal speech.

Epithalamus (Pineal gland)

Secretes melatonin to regulate circadian rhythms (day/night cycles)

Medulla oblongata

Segment of the brain that connects w/spinal cord; continuation of the spinal cord above the foramen magnum. Origin or termination of cranial nerves IX-XII (cochlear). FUNCTION- relays sensory info to the thalamus and other brainstem centers; it also contains major centers that regulate autonomic function, such as heart rate, blood pressure, respiration, & digestive activities.

Facial Nerve (VII)

Sensory: taste receptors on the anterior 2/3 of the tongue. Motor: muscles of facial expression, lacrimal (tear) gland, and submandibular & sublingual salivary glands.

Optic Nerve (II)

Sight; Carries visual info; Passes through foramina - intersects at optic chiasm, continues as optic tracts to nuclei of left & right thalamus.

Trochlear Nerve (IV)

Smallest of cranial nerves; Eye movement; Motor to one eye muscle.

Thalamus

The brain's sensory switchboard, located on the top of the brainstem that surrounds the 3rd ventricle; 2 halves connected by intermediate mass; comprised of sensory nuclei. FUNCTION- it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla.

Hypothalamus

The floor of the diencephalon; Connects to pituitary gland via infundibulum. Region of the brain containing centers involved with the unconscious regulation of visceral functions, emotions, drives, and coordination of neural and endocrine function. Also functions in maintaining homeostasis and regulates hunger, thirst, and body temperature. Associated with rage, pleasure, pain, & sexual arousal.

Occipital lobe

Visual cortex- receives visual info and interprets visual information.

Vagus Nerve (X)

Wandering- It is the only cranial nerve to pass into the body cavities below the neck. It is primarily parasympathetic in nature and is the major nerve affecting the heart and most of the gastrointestinal tract. It slows the heart down and speeds up the activity of the gastrointestinal tract. *sensation from viscera; ANS visceral muscle movement (respiratory, digestive, cardiovascular systems)

Pons

a brain structure "bridge" located at the top of the brain stem that connects the cerebellum to the brain stem and is involved in respiration, movement, and sleep. Cranial nerve VII-vestibulocochlear

Frontal lobe (motor & sensory)

associated with reasoning, planning, parts of speech, movement, emotions, and problem solving. Primary motor cortex- neurons here direct voluntary movement by controlling somatic motor neurons in the brainstem & spinal cord. Gustatory cortex- receives taste sensations. Precentral gyrus- forms the anterior margin of the central sulcus & its surface is the primary motor cortex.

Projection fibers (white matter of cerebrum)

connect the cerebrum to other parts of the brain and the spinal cord.

Association fibers (white matter of cerebrum)

connect the gyri within the same hemisphere -short fibers connect adjacent gyri -long fibers connect lobes in the same hemispheres.

Midbrain (mesencephalon)

contains various nuclei and bundles of ascending & descending nerve fibers. Includes 2 pair of colliculi (sensory nuclei)in the corpora quadrigemina. - Superior colliculi (visual reflex centers) control the reflex movement of the eyes, head, neck, and response to visual stimuli. -Inferior colliculi (auditory reflex centers) control the reflex movement of the head, neck, and trunk in response to auditory stimuli. -Cerebral peduncles- location of descending (motor) tracts. * Reticular Formation- one of the most important brainstem components that is a network of interconnected nuclei thru brainstem responsible for maintaining stae of conciousness. Contains motor nuclei for cranial nerves IV & III

Cerebrum

largest portion of the brain; divided into right and left halves, know as cerebral hemispheres, that are connected by a bridge of nerve fibers called the corpus callosum. Includes the cerebral cortex, the cerebral nuclei, and the white matter.

Glossopharyngeal Nerve (IX)

sensory nerve to the pharynx and back of the tongue; swallowing, taste, ANS to salivary glands, sensory reception from monitoring of blood pressure in large arteries.

Commisural fibers (white matter of cerebrum)

transmit impulses horizontally from the gyri in one cerebral hemisphere to the corresponding gyri in the opposite cerebral hemisphere ( e.g. corpus callosum, anterior commissure)

Cerebral processing centers

∗"High order" integrative centers receive info from many different association areas. - control extremely complicated activities & performs complicated analytical functions. ∗ May be unilateral, but many are lateralized- restricted to either the left or right hemisphere.