PET Scans. External Appearance. The Brain: Anatomy & Functions. Cerebral Hemispheres

Transcription

1 PET Scans The Brain: Anatomy & Functions Click for PET Scan video Cerebral Hemispheres External Appearance a pattern of ridges and shallow grooves ridges - gyri (sing. gyrus) grooves - sulci (sing. sulcus) deep grooves are called fissures longitudinal fissure - divides brain into a right and left side postcentral gyrus central sulcus precentral gyrus parieto-occipital sulcus lateral sulcus longitudinal fissure Internal Appearance transverse cerebral fissure brainstem Cerebral Cortex white matter - myelinated fibers more abundant than grey matter grey matter - cell bodies, dendrites, and neuroglia referred to as cerebral cortex somatosensory association cortex gustatory cortex

2 Cerebral Cortex referred to as our conscious mind billions of neurons arranged in 6 layers all neurons of the cortex are interneurons enables us to be aware of ourselves and our sensations, to communicate, remember, understand, and initiate voluntary movements 3 functional areas: motor, sensory, association right hemisphere - controls left side of the body left hemisphere - controls right side of body hemispheres have specialized functions no functional area acts alone Sensory Areas conscious awareness of sensation primary somatosensory cortex collects sensory data from skin, skeletal muscles, joints, and tendons somatosensory association cortex integrates sensory input to determine what is being felt visual areas - sight auditory areas - hearing olfactory cortex - smell gustatory cortex - taste visceral sensory area - visceral senstations upset stomach, full bladder, etc. vestibular cortex - balance Motor Areas controls voluntary movements primary motor cortex conscious controls of skilled or precise voluntary movements premotor cortex controls learned motor skills of a repetitious or patterned nature (playing an instrument, typing) Broca's area present in only one hemisphere (usually left) directs the muscles involved in speech production Association Areas gives meaning to info we receive, store it in memory, connect it to prior experiences and knowledge, decide what to do with info prefrontal cortex most complicated cortical area intellect, cognition, recall, personality, working memory, producing abstract ideas, judgment, reasoning, persistence, planning slow to develop responds to positive & negative social feedback posterior association area recognizing patterns & faces, orientation in space, combining sensory data to make a coherent whole Wernicke's area - understanding written and spoken language limbic association area - emotions Curious Case of Phineas Gage Link to Smithsonian.com Video of Phineas' story Diencephalon thalamus hypothalamus epithalamus

3 Diencephalon thalamus - "inner room" relay station for sensory info hypothalamus autonomic control center (blood pressure, pulse rate, pupil size, etc.) emotional responses (pleasure, fear, rage, sex drive) body temperature regulation regulation of food intake (full or hungry) regulation of water balance and thirst regulation of sleep-wake cycles control of endocrine system epithalamus pineal gland - secretes melatonin (sleep-inducing hormone) and helps regulate sleep-wake cycle anatomy Cerebellum midbrain Brain Stem pain suppression visual reflex centers (head and eyes following moving objects) reflexive responses to sound pons relay station between cerebrum and other parts of the brain helps control rate and depth of breathing medulla oblongata sensory relay to cerebellum pathway between brain and spinal cord regulates heart rate, blood vessel diameter, respiratory rate, vomiting, coughing, etc. Sheep Brain Dissection arbor vitae ("tree or life") - white matter functions integrates sensory info to produce coordinated skeletal muscle movements and maintenance of equilibrium word association puzzle solving Sheep Vs Human Brain Protecting the Brain & The Spinal Cord

4 Protection Meninges 3 connective tissue membranes surrounding the brain neurons are easily damaged layers of protection dura mater ("tough mother") - outermost meninx (sing.) dural septa - subdivide the cranial cavity and limit excessive brain movement arachnoid mater - middle meninx, loose covering pia mater ("gentle mother") - innermost meninx, clings tightly to the brain, lots of blood vessels bones of the skull meninges (membranes) cerebrospinal fluid (watery cushion) blood-brain barrier functions protect and cover brain protect blood vessels contain cerebrospinal fluid form partitions in the skull imbalances meningitis - inflammation of the meninges; may spread to CNS Cerebrospinal Fluid formed in the choroid plexuses of the brain watery, nutrient-rich "broth" surrounding brain and spinal cord acts as a liquid cushion and gives buoyancy to brain and spinal cord reduces brain weight by 97% average adult has 150 ml of CSF which is completely replaced every 8 hours about 500 ml produced daily imbalances hydrocephalus - CSF accumulates and puts pressure on the brain CSF H2 O Blood-Brain Barrier junction between capillaries and neurons selective nutrients (glucose, essential amino acids, some electrolytes) move passively bloodborne metabolic waste, proteins, certain toxins denied access nonessential amino acids and potassium actively pumped out of brain ineffective against fats, fatty acids, oxygen, carbon dioxide ex. alcohol, nicotine, anesthetics

5 1 All of the following protect the brain EXCEPT 2 Which of the following is the correct order of meninges from outside to inside? A choroid matter B blood-brain barrier A dura, arachnoid, pia C dura matter B dura, pia, arachnoid D cerebrospinal fluid C pia, arachnoid, dura E skull bones D pia, dura, arachnoid Imbalances of the Brain traumatic brain injury concussion - alteration in brain function following a blow to the head contusion - bruising of the brain and permanent neurological damage subdural or subarachnoid hemorrhage - bleeding from ruptured vessels cerebral edema - swelling of the brain strokes (cerebrovascular accidents) - blood circulation to a brain area is blocked (ischemia)and brain tissue dies degenerative brain disorders Alzheimer's Disease - progressive, results in dementia Parkinson's Disease - degeneration of dopamine releasing neurons Huntington's Disease - hereditary disorder that causes protein to build up in brain cells and destroy tissue structure Spinal Cord extends from foramen magnum to 1st or 2nd lumbar vertebrae divided into 31 segments each with a pair of spinal nerves mostly composed of interneurons gray matter inside, white matter outside (butterfly) cauda equina functions conducts info to and from the brain center for spinal reflexes Click for Michael J Fox video

6 1 Which of the following statements is TRUE? A The spinal cord runs from the foramen magnum to the end of the coccyx. B The spinal cord has 32 segments. C The spinal cord has gray matter on the interior, as opposed to on the exterior like the brain. D Its main functions are sensory input and motor output. Imbalances of the Spinal Cord spinal cord trauma paralysis - loss of motor function paresthesias - sensory loss poliomyelitis - inflammation of gray matter poliovirus enters body through feces-contaminated water amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease) - progressive destruction of spinal cord cerebral palsy - voluntary muscles are poorly controlled or paralyzed as a result of brain damage (typically caused by a lack of oxygen during birth) Poliomyelitis Click for ALS video