6.1 - . Nerve centre – classification and properties. Brain circulation. Cerebro-spinal fluid (CSF)

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8 Terms

1
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sections

what is nerve centre

types of nerve centres

brain circulation

metabolic factors that affect cerebral blood flow

effects of decreased O2

effects of higher pCo2

cerebrospinal fluid

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what is nerve centre

A nerve centre is an area, commonly in either a plexus or ganglion that organise a reflex.

Receptor→ nerve centre→ effector

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types of nerve centres

  1. Respiratory centre- nerve centres in the brainstem controlling aspects of respiration

  2. Cardiovascular centre- --located in brainstem, gets input from baroreceptors and chemoreceptors, controls heart rate, blood pressure etc

  3. Feeding centre- group of cells in the hypothalamus which when stimulated cause hunger.

  4. Pontine micturition centre → brain stem → relaxes urethral sphincter → micturition

    Nerve centre can be found in the brain stem and spinal cord segments

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brain circulation

  • The normal flow of blood within the brain is 50-65 ml of blood/100g of brain tissue/minute.

  • Cerebral blood flow is related to the metabolic activity of the tissue.

  • Brain requires glucose

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metabolic factors that affect cerebral blood flow

  • Co2 concentration

  • H+ ion concentration

  • O2 concentration

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effects of decreased O2

  • Decreased O2 conc. – leads to hypoxia- causes respiratory distress

    • If blood flow becomes insufficient to supply the brain of the needed amount of oxygen

    • oxygen deficiency mechanisms cause vasodilation.

    • Increasing CBF and returning O2 levels to normal.

    • Low levels have proven to cause coma and diminished neural activity.

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effects of higher pCo2

  • increase in arterial PCo2 increases CBF.

  • CO2 combines with water in the body fluids to form carbonic acid, → dissociates to form H+ ions

  • The H+ ions are used for vasodialation of cerebral levels

  • Vasodilation is needed to remove excess CO2 due to its harmful neural effects.

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cerebrospinal fluid

  • Clear and colourless fluid

  • Produced by choroid plexus –mainly 3rd ventricle

  • Choroid plexus produces approx. 500 *-ml of CSF per day.

  • 100-160ml is present at each time

  • Cushions brain from impact and nutritive, shock absorber

  • Arachnoid granulations drain CSF

  • CSF flows throughout the in the brain ventricles and into spinal cord, clearing the metabolic waste from CNS through the blood-brain barrier.