A.2 The human brain Flashcards
Development of the brain
In a mammalian embryo, the neural tube is initially a straight, linear structure running the length of the rear-side.
Most of the neural tube eventually becomes the spinal cord, but as early as the fourth week the anterior end develops into three distinct bulges known as the primary vesicles. The vesicles continue to develop and form the fore, mid and hind sections of the brain.
Metabolism of the brain
The energy demands of the brain are high: they account for at least 20% of a human adult’s energy consumption.
Studies indicate have linked higher cognitive functions to increased glucose demand.
Cell respiration produces
the ATP that is constantly required by neurons to:
Synthesise neurotransmitters
carry out the active transport needed to maintain resting potential.
Hypothalamus
Maintains homeostasis via coordination of the nervous and endocrine systems, produces hormones secreted by posterior pituitary
Pituitary gland
Produces and secretes hormones regulating many body functions, e.g. such as ADH
Medulla oblongata
Controls automatic and homeostatic activities, such as swallowing, digestion and vomiting, and breathing and heart rate.
Cerebellum
Coordinates unconscious functions, such as movement and balance.
Cerebral Hemisphere
Act as the integration centre for highly complex functions, such as learning, memory and emotion.
Identifying brain function – autopsy and animal experiments
Animal experiments can take different approaches to investigating brain function. Commons approaches are:
Autopsy, dissection of the brain
Stimulating regions of the brain with electrodes and then observing behaviour and movement – e.g. Ferrier work with dogs and monkeys
Lobotomy - removing regions of the brain and observing impairment of brain function, e.g. Flourens’ experiments on pigeons
Identifying brain function - lesions
Presence of a lesion is usually associated with damaged and loss of function in the affected area.
Lesions are
abnormal areas in brain tissue caused by accidents or present from birth
Identifying brain function - fMRI
fMRI is the primary tool used in modern research. It measures changes in blood flow through the brain. This can indicate which regions of the brain are most active.
Measurements can be made in real-time so regional brain activity can be correlated with a stimulus. Also the sequencing of brain activity, e.g. language comprehension followed by production can be observed.
The procedure is non-invasive and can be performed without injury, but it is an indirect measure and not all brain activity is detected.
fMRI works because
oxyhaemoglobin responds differently to a magnetic field than (deoxygenated) haemoglobin. Computers interpret the results to produce coloured brain activity images (different colours often represent different levels of activity).
The autonomic nervous system
The autonomic nervous system controls unconscious processes using the medulla oblongata.
The autonomic nervous system is part of the peripheral nervous system, which consists of all the nerves outside the central nervous system.
There are two distinct parts to the autonomic nervous system:
sympathetic and parasympathetic. These two parts have contrary effects, e.g. parasympathetic nerves cause an increase in blood flow to the gut, during digestion and absorption of food, whereas the sympathetic nerves cause a decrease in blood flow.