E5 The Human Brain Flashcards
Outline the function of the medulla oblongata
Controls automatic and homeostatic activities, such as swallowing, digestion and vomiting, and breathing and heart rate
Outline the function of the cerebellum
Coordinates unconscious functions, such as movement and balance
Outline the function of the hypothalamus
Maintains homeostasis via coordination of the nervous and endocrine systems, produces hormones secreted by posterior pituitary
Outline the function of the pituitary gland
Produces and secretes hormones regulating many body functions
Outline the function of the cerebral hemispheres
Act as the integration centre for highly complex functions, such as learning, memory and emotion
Explain how animal experiments can be used in the identification of the brain part involved in specific functions
- One method of investigating the function of specific brain regions is to either stimulate the region with electrodes or remove the region (lobotomy) and assess the physical effect
- Because such procedures are highly invasive and potentially damaging, animal models are frequently used
- Such studies may be limited by the fact that animal brains may be dissimilar to human brains, so valid comparisons can be hard to make
- The best comparisons are made with primates, however ethical considerations are of greater concern with these models
- Animal experimentation using rats and mice have been used to understand and develop drug treatments for brain diseases such as MS
Explain how lesions can be used in the identification of the brain part involved in specific functions
- Lesions are abnormal areas in brain tissue (either from accidents or congenital) which can indicate the effect of the loss of an area
- Such studies may be limited by the fact that many functions involve multiple brain areas, making complex effects difficult to interpret
- The brain also has the ability to re-learn skills by re-routing the function through another part of the brain (plasticity)
- Split brain patients have been used to identify the functional roles of the left and right hemispheres
- Individuals with aphasia (impairment to use or understand language) often have damage to specific regions of the left hemisphere
Explain how fMRI scanning can be used in the identification of the brain part involved in specific functions
- fMRI records changes in blood flow and can indicate active regions of the brain via an increase in blood flow
- Oxygenated haemoglobin (oxyhaemoglobin) responds differently to a magnetic field than deoxygenated haemoglobin
- These differences in oxygenation (reflecting level of brain activity) can be represented visually by different colours
- When a subject is given a stimulus designed to stimulate specific brain activity, fMRI can be used to localise regions involved
- Temporal activities can also be recorded to allow identification of sequential collaboration between brain parts
- While this procedure is non-invasive and can be performed on healthy subjects, not all brain activity is detected by fMRI
- fMRI studies have been used to diagnose ADHD and dyslexia, in addition to being used to monitor recovery from strokes
Explain sympathetic control of the heart rate, movement of the iris and flow of blood to the gut
- Involved in processes that prepare the body for action (‘fight or flight’ responses)
- The sympathetic nervous system releases noradrenaline (adrenergic) via sympathetic nerves
- Heart rate will increase to improve blood flow (via release of adrenaline)
- Pupils will dilate to improve vision (via contraction of radial muscles)
- Blood flow to gut will decrease (due to vasoconstriction of blood vessels by smooth muscles)
Explain parasympathetic control of the heart rate, movement of the iris and flow of blood to the gut
- Involved in processes that occur when the body is relaxed (‘rest and digest’ or ‘feed and breed’ responses)
- The parasympathetic nervous system releases acetylcholine (cholinergic) via parasympathetic nerves
- Heart rate will decrease to reduce blood flow (via stimulation by vagus nerve)
- Pupils will constrict to restrict light and potential retinal damage (via contraction of circular muscles)
- Blood flow to gut will increase to facilitate digestion (due to vasodilation of blood vessels by smooth muscles)
Explain the pupil reflex
- The pupil reflex is a cranial reflex originating at the brainstem and under the control of the autonomic nervous system
- Bright light can overstimulate photoreceptors and potentially damage the retina
- In changing levels of light, the iris will automatically resize to regulate the amount of light that reaches the retina
In dim light conditions:
• Relay neurons stimulate thesympatheticnervous system, causingradial musclesto contract and the pupil todilate
In bright light conditions:
• Relay neurons stimulate theparasympatheticnervous system, causingcircular musclesto contract and the pupil toconstrict
Discuss the concept of brain death
- Whole brain death is the loss of measureable activity in the brain stem and cerebrum
- Failure of the pupil to response to light indicates brain stem death
- Without brain stem function, life cannot continue
- Cerebrum involves higher order brain function
- Non-functioning cerebrum with functioning brain stem is vegetative state
- Some would argue that this is the death of the person, although brain stem function alone may be able to maintain homeostasis
Outline how pain is perceived and how endorphins can act as painkillers
- Pain is perceived when impulses pass from pain receptors to sensory areas of the cerebral cortex
- Endorphins are released by the pituitary gland during stress, injury or exercise, and act as painkillers by blocking pain perception
- They do this by blocking the release of neurotransmitters at the synapses involved in pain signal transmission
