5.5.9 The Human Brain Flashcards
Why is the human brain important?
The brain, alongside the spinal cord, is part of our central nervous system (CNS)
The brain is made of billions of interconnected neurones and is responsible for controlling complex behaviours
Within the brain are different regions that carry out different functions
These regions include:
The cerebrum
The hypothalamus
The pituitary gland
The cerebellum
The medulla oblongata
What is the cerebrum?
Largest part of the brain in humans (accounts for about 80% of the total mass of the brain)
Carries out a large variety of functions involved with conscious activities, including:
Vision
Hearing
Speech
Thinking
Memory
Consists of five lobes
Divided into two halves, known as the cerebral hemispheres
The hemispheres are joined together by a band of nerve fibres, known as the corpus callosum
The right hemisphere controls the left side of the body and the left one controls the right side
Has a thin outer layer known as the cerebral cortex or ‘grey matter’
The cerebral cortex consists of the cell bodies of neurones
It is highly folded, which increases its surface area and allows it to contain a greater number of neurones
With more neurones in the brain, more connections between neurones can be made
This is important, as the more connections between neurones in the brain, the greater the ability of the brain to carry out more complex behaviours
Beneath the cerebral cortex or grey matter layer is the ‘white matter’
The white matter consists of the myelinated axons of neurones
What is the hypothalamus?
Area in the middle of the lower part of the brain
It is found just above the pituitary gland (which it is connected to)
Monitors the blood as it is flowing through it and in response, releases hormones (involved in homeostasis) itself or stimulates the pituitary gland to release certain hormones
Main functions include:
Regulating body temperature - by monitoring blood temperature and initiating a homeostatic response if this temperature gets too high or too low
Osmoregulation - by monitoring how concentrated the blood is and if it gets too concentrated, stimulating the posterior pituitary gland to release anti-diuretic hormone (ADH), which causes increased water retention in the kidneys. The hypothalamus also generates a feeling of thirst, causing us to increase our water intake
Regulating digestive activity - controls the secretion of enzymes in the gut and peristalsis. The hypothalamus also generates a feeling of hunger, causing us to increase our food intake if blood nutrient concentrations get too low
Controlling endocrine functions - the hypothalamus releases chemicals that cause the pituitary gland to release certain hormones that control a variety of processes (e.g. metabolism, growth and development, puberty sexual functions, sleep, mood)
What is the pituitary gland?
At the bottom of the brain, below the hypothalamus
Produces a range of hormones
Some of these directly influence and regulate processes in the body but some stimulate the release of further hormones from specific, remote locations in the body (e.g. from other glands)
Divided into two sections: the anterior pituitary and posterior pituitary
Anterior pituitary - produces and releases certain hormones
Posterior pituitary - stores and releases hormones produced by the hypothalamus (e.g. ADH and oxytocin)
What is the cerebellum?
Lies below the cerebrum
Controls motor coordination
This includes balance
Balance is a highly complex function that requires coordination between multiple parts, including the eyes, semicircular canals in the ears, and many muscles
Functions only subconsciously (i.e. all of the actions it controls are involuntary)
What is the medulla oblongata?
Also known as the medulla
Found at the very base of the brain, where it joins the spinal cord
Contains three ‘centres’ that control different functions:
The cardiac centre - controls heart rate
The vasomotor centre - controls blood pressure by controlling the contraction of smooth muscles in arteriole walls
The respiratory centre - controls breathing rate (contains an inspiratory centre and an expiratory centre)
