The Brain. Brain. Spinal Cord. Cauda Equina

Transcription

1 The Brain Brain Spinal Cord Cauda Equina

2 The Brain Ventricles- cavities in the brain filled with cerebrospinal fluid connected to the subarachnoid space- fluid filled space surrounding the brain Brain Regions cerebral hemispheres or cerebrum diencephalon brain stem cerebellum

3 Brain Regions cerebral hemispheres diencephalon brain stem cerebellum

4 Brain Regions

5 The Ventricles

6 Cerebral Hemispheres superior part of the brain gyri- characteristic elevated ridges separated by sulci (shallow grooves) fissures- deeper grooves + longitudinal- separates cerebral hemispheres + transverse- separates cerebral hemispheres from the cerebellum + lateral sulcus- separates the temporal, frontal, and parietal lobes + parieto-occipital sulcus- separates the occipital & parietal lobes + central sulcus- separates parietal & frontal lobes

7 Cerebral Hemispheres

8 Cerebral Hemispheres

9 Cerebral Hemispheres each hemisphere has five lobes: frontal, parietal, occipital, temporal, insula 3 regions of the cerebral hemisphere basal nuclei- areas of gray matter within the white matter gray matter areas located deep within the white matter of the cerebral hemispheres important in starting, stopping and monitoring movements executed by the cortex help with our ability to perform several tasks at once

10 Cerebral Hemispheres occipital parietal temporal frontal

11 Cerebral Hemispheres

12 Cerebral Hemispheres white matter, internal responsible for communication between cerebral areas and between the cerebral cortex and lower CNS centers consists of myelinated fibers classified by the direction they run commissural fibers connect corresponding gray areas of the two hemispheres Ex: Corpus callosum association fibers connect different parts of the same hemi projection fibers fibers entering the cerebral hemispheres from the lower brain and spinal cord centers; fibers leaving the cortex to the lower areas

13 Cerebral Hemispheres cortex- gray matter (cell bodies, dendrites, unmyelinated axons), superficial conscious mind- communication, memory, understanding, voluntary movement 3 functional areas: motor, sensory, association

14 Cerebral Hemispheres Motor primary motor cortex (precentral gyrus)- skeletal muscle control premotor cortex- learned motor skills (repetitive) Broca's area- left hemisphere- motor speech area frontal eye field- controls voluntary eye movement Sensory primary somatosensory cortex (post central gyrus)- sensation somatosensory association cortex- integrates sensory input (touch, temp, pressure) visual areas- visual stimuli occipital lobe primaryassociationauditory areas- auditory stimuli temporal lobe primaryassociationolfactory cortex- smell frontal lobe gustatory cortex- taste stimuli parietal lobe vestibular cortex- position of the head in space & balance - insula

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19 Cerebral Hemispheres Association Areas that communicate with the motor cortex and sensory association areas to analyze, recognize and act on sensory inputs Pre-frontal cortex: involved in intellect, personality, learning ability, conscience, planning, reasoning, judgment, etc. Language areas: LEFT Hemisphere Wernicke s area- sound out unfamiliar words Broca s area- speech production Lateral prefrontal cortex- language comprehension and word analysis Lateral and ventral parts of the temporal lobe- reading and naming Body language & Tone of Voice: RIGHT Hemisphere General interpretation area- takes all information and coordinates it with a single thought (one hemisphere only usually left) Visceral association area- body organ perceptions (insula)

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21 Diencephalon central core of the forebrain and is surrounded by the cerebral hemispheres consists of three paired structures» thalamus integrates sensory information and project it to a specific association cortex; the gateway» hypothalamus visceral control center; important in body homeostasis Ex: ANS, emotional response, body temperature, hunger, water balance, thirst, endocrine system, pituitary gland» epithalamus regulates sleep and mood; pineal gland secretes melatonin to induce sleep; the choroid plexus is also part of the epithalamus- it produces cerebrospinal fluid (CSF)

22 Brain Stem Three Regions: midbrain, pons, medulla oblongata Midbrain visual and auditory reflex centers Contains 4 bulges called the corpora quadrigemina superior colliculi visual attention, blinking, focusing, pupil size, and turning the head from visual stimuli inferior colliculi relays inner ear signals to other parts of the brain; reflexive movements due to sound cues

23 Brain Stem Pons controls respiratory rate and depth; connects motor cortex with cerebellum Posterior surface contains 2 pairs of cerebellar peduncles to communicate with the cerebellum. Contains parts of the Reticular Formation which is involved in sleep, respiration and posture.

24 Brain Stem Medulla Oblongata controls touch, pressure, temperature, taste, pain, chewing, salivation, swallowing, gagging, vomiting, respiration, speech, coughing, sneezing, sweating, cardiovascular events, gastrointestinal control, head, neck and shoulder movements Contains the Reticular Formation with special centers Cardiac Center rate and force of heartbeat Vasomotor Center regulates blood pressure and blood flow Respiratory Center rhythm and depth of breathing

25 Cerebellum Ipsilateral- to and from the same side of the body Separated from the cerebral hemispheres by the transverse fissure Uses sensory input & information from the motor cortex to perform precise timing and appropriate patterns of skeletal muscle contraction for smooth coordinated movements Outer surface is gray matter, while inside lies branching white matter called the arbor vitae Bilaterally symmetrical with two hemispheres that are connected by the vermis Pleatlike gyri, folia, cover its surface 3 lobes: posterior, anterior & flocculonodular

26 Cerebellar Functions There are 3 pairs of cerebellar peduncles that contain connections running to and from the brainstem. Exploration of the textures of objects Spatial perception & 3D images Time keeping & prediction of the location of moving objects Pitch differences in sound & language function Planning & scheduling Impulse control

27 Cerebellum

28 Brain Systems The Limbic System-" the emotional brain Main structures: hypothalamus and anterior nucleus of the thalamus; the fornix links the limbic system together Psychosomatic illnesses Three parts important in emotion & memory Amygdala recognizes angry or fearful faces, assesses danger and gives a fear response; may also help with long term memory along with the hippocampal structures Cingulate gyrus expresses our emotion through gestures and plays a role to resolve our mental conflicts Hippocampus functions in memory Interacts with prefrontal lobes to React emotionally to events Be aware of emotion in our lives

29 The Limbic System

30 The Reticular Formation (RAS) Extends through the brain stem & connects with the cerebrum aides in the arousal of the brain through extensive axonal connections acts as a filter for sensory input Ability to block some pain stimuli Other Functions: posture, muscle tone, balance, track objects, central pattern generators, transmit visual and auditory stimuli to the cerebellum Brain Systems

31 Brain Protection Skull Meninges: dura mater, arachnoid, pia mater Function to cover & protect the CNS, protects the blood vessels & enclose venous sinuses, contain cerebrospinal fluid, form compartments within the skull Dura mater the strongest of the 3 layers A number of dural septa exist Epidural space space between the bone and the dura mater Two layers of fibrous connective tissue that are connected together in most places Periosteal layer - attached to skull Meningeal layer covering of the brain & is continuous with the spinal cord Arachnoid mater Loose brain covering, above the subarachnoid space (contains CSF) Arachnoid villi lead to the superior sagittal sinus to return CSF to the venous system Pia mater Clings tightly to the brain and richly invested with blood vessels

32 Brain Protection

33 Brain Protection

34 Brain Protection Cerebrospinal fluid Protects the CNS, nourishment and chemical signal transportation Similar in composition to blood plasma Choroid plexuses produce and clean CSF; returns to blood circulation by arachnoid villi in the dural sinus 150 ml in an adult; replaced every 8 hours Blood-brain barrier Layer of endothelial cells joined by tight junctions Astrocytes regulate what comes into the brain tissue Regulates the chemicals that can enter the brain tissue Ineffective against fat soluble materials Incomplete in certain areas allowing harmful chemicals to pass

35 Cerebrospinal Fluid Circulation

36 Spinal Cord Extends from the foramen magnum to the L1 and L2 vertebrae Protected by bone, meninges, and cerebrospinal fluid 31 pairs of spinal nerves Cauda equina collection of nerve roots at the inferior end of the vertebral canal Cross Section Anterior median fissure & posterior sulcus divide the spinal cord to right and left halves Gray matter looks like an "H (inner part of cord) Posterior (dorsal) horns sensory interneurons Anterior (ventral) horns somatic motor neurons to skeletal muscles White matter myelinated & unmyelinated nerve fibers allowing communication (outer part of cord) Ascending, Transversely, and Descending Tracts

37 Spinal Cord

38 Spinal Cord

39 Spinal Cord Dorsal Root sensory neurons entering the back area of the spinal cord Ventral Root motor neurons exiting the front area of the spinal cord Dorsal Root Ganglion a bump on the dorsal root containing a collection/cluster of sensory neuron cell bodies just outside the spinal cord Spinal Nerve has sensory and motor neurons that connect (enter/exit) directly from the spinal cord 31 pairs

40 Spinal Cord Two Main Functions 1. Provide a highway for information traveling to and from the brain 2. Reflexes the spinal cord is a major reflex center Reflexes are fast, predictable responses. Reflex Arcs go through the spinal cord 1. monosynaptic reflex arc sensory neuron into the spinal cord synapses directly with a motor neuron carrying the information back out of the spinal cord 2. polysnaptic reflex arc at least one association neuron is located between the sensory and motor neurons

41 Spinal Cord Ascending Tracts bundles of association neurons that carry sensory information to the brain 1. Spinothalmic Tracts carry sensory information about pain, temperature, touch 2. Posterior Column Tracts carry information about movement, pressure, and two-point discrimination (two points in the body next to each other)

42 Spinal Cord Neuronal Circuits routes in the brain that transfer information 1. simple series circuit- information is passed to only 1 association neuron, the neuron analyzes the information and sends the response back to the spinal cord 2. diverging circuit- one association neuron passes its information to many neurons to elicit many different responses

43 Spinal Cord Neuronal Circuits routes in the brain that transfer information 3. converging circuit- opposite of diverging many presynaptic neurons pass information to a single neuron used to intensify the information 4. reverberating circuit- short term memory repeated actions

44 Spinal Cord Descending Tracts bundles of association neurons that carry motor information from the brain 1. Pyramidal Tract carries motor response information that allows voluntary skeletal movement 2. Extra Pyramidal Tract carries motor response information that allows automatic (not voluntary) movements maintains posture

45 Cranial nerves Cranial Nerves any sensory neurons connected directly to the brain 12 cranial nerves Olfactory Nerve smell Optic Nerve vision Occulomotor Nerve eye movement Trochelar Nerve eye movement Abducens Nerve eye movement Trigeminal Nerve chewing Facial Nerve smile/facial movement Vestibulocochlear hearing and balance/equilibrium