SCRN study guide: anatomy and physiology-Questions and Answers

What percentage of the body's oxygen supply and cardiac output does the brain use? - Answer- The brain uses 20% of the body's oxygen suppy and 15% of the body's cardiac output. *brain cells do not store oxygen or glucose. The need a constant suppy of micronutrients from arterial blood. What is the normal blood flow to cerebral tissue? When does electrical failure occur? - Answer- Normal blood flow to the brain is 50-55ml/100/min electrical failure occurs at 15-20ml/100/min temporal lobe - Answer- hearing, memory, learning, wernicke (receptive aphasia), visual and auditory memories, behavioral elements frontal lobe - Answer- personality, affect, tact, inhibition, judgement, planning, motor strip body parts, frontal eye fields- conjugate eye movements; pupil changes, extra pyramidal motor control, motor speech-articulation, speed, and rhythm of speech, creative thought,abstract thinking parietal lobe - Answer- pain, temperature, light, touch, vibration, two point discrimination, visual function, language, reading, internal stimuli, tactile sensation, and sensory comprehension occipital lobe infarcts - Answer- macular vision, broca's area (expressive aphasia), facial neurons Cerebellum - Answer- The cerebellum first receives information about an intended movement then it sends information back to the motor cortex about the required direction, force, and duration of the movement. It acts like an air traffic controller. The cerebellum can't initiate movement but is responsible for unconscious coordination of movement. can cause lack of coordination, clumsiness, shaking/tremors * It is important to diagnose cerebellum infarcts early because swelling may cause brain stem compression or hydrocephalous Cerebrum - Answer- grey matter: cognition and personality deficits white matter (deep): regions of the brain cannot communicate with each other What causes brain stem infarcts? - Answer- usually related to basilar occlusion. This type of infarct is serious or fatal. Survivors may be left in a vegatative state What is the main cause of cell death? - Answer- hypoxia or anoxia What factors influence the rate and extent of penumbral tissue and infarcted tissue - Answer- 1: rate of onset 2: Duration of ischemia 3: Degree of collateral circulation perfusing the infarcted zone 4: functionality of systemic circulation 5: hematologic factors 6: metabolic factors What is an appoptic cell death pathway? - Answer- programed cell death in the penumbral zone: normal biologic function where cells are programmed to die in an organized fashion after nearby cell death What is a necrotic cell death pathway? - Answer- loss of O2 and glucose and cellular electrolyte exchange from a loss of atrial perfusion causes energy failure and rapid cytoskeletal breakdown. What is the ischemic cascade? - Answer- lack of blood-infarct-edema-swelling-center of brain shifts from midline-increased ICP-compression of neurons, nerve tracts, and cerebral arteries-persistant edema-irreversable damage /death neuron - Answer- A: 1. Neuron consists of cell bodywith nucleus and 1 or more extensions 2. Dendrites receive nerve impulses from other neurons or sensory receptors 3. axons carry nerve impulses away from cell body to another neuron or effector organ B: 1. stimulus affects the axon by changing the permeability of the axon positive ions 2. influx of posisitve ions reduces electrical potential across a segment of the membrane 3. This triggers a change in the adjacent segment of the axon like a chain reaction 4. when it gets to the presynaptic terminal a neurotransmitter is released 5. THe neurotransmitter crosses the synapse to interact with receptors on post synaptic cell 6. This opens ion specific channels in post synaptic cell, which changes the permeability for positive ions. 7. the transient change is determined by the concentration of ions on either side of the cell membrane Maintaining these ion gradients requires a constant supply of glucose and O2 Stroke on a cellular level - Answer- 1. lack of glucose and O2 deplete the cellular energy required to maintain electrical potential. 2. This makes the brain tissue "leaky" and cells lose ATP and potassium, which is needed for energy exchange A: cell membrane failure occurs between 6-10ml/100g/min B: cell death occurs at >6ml/100g/min ischemic cascade - Answer- Normal brain function: 50-55ml/100g/min Oligemia: symptoms start 30-40ml/100g/min moderate ischemia: penumbra-damaged but viable tissue that may be viable for several hours. (TpA effective) 20-30ml/100g/min severe ischemia/cell death: necrosis of neurons and supporting cells: 0-10ml/100g/min intercerebral hemorrage: primary - Answer- results directly from pressure caused hematoma 1: several minutes to one hour after hemo