The Brain Flashcards
(43 cards)
What is the brain and how much does it weigh?
- Co-ordinating centre of sensation and intellectual activity.
-Adult brain weighs 1.5kg and contains 8.6 x 10^6 neurones, each making more than 1000 connections. - In addition there are about 10^12 gilal cells supporting the functions of the neurones.
What is the meninges?
- Brain is continuous with spinal cord and both are surrounded by three membranes, or meninges.
-The delicate pia mater is on the brain surface.
-The thick dura matter is attached to the skull.
-The arachnoid mater is between.
What is meningitis?
- An inflammation of the meninges.
- Viral meningitis is more common than bacterial meningitis which can be fatal.
What are the ventricles of the brain?
- Four connected cavities in the brain into which cerebro-spinal fluid is secreted.
- Cells lining the ventricles produce cerebro-spinal fluid, which circulates between the ventricles and is passed into the spinal canal.
Why does cerebro-spinal fluid resemble plasma in its components?
- Supplies nutrients eg glucose.
- Supplies oxygen, carried in solution. Cerebro-spinal fluid does not contain red blood cells and is pale yellow in colour.
- Contains antibodies and white blood cells, giving it a role in resisting infection.
What are the three regions of the brain?
- The forebrain
- The midbrain
- The hindbrain
What is the hindbrain?
- The most primitive part of the human brain. It sustains basic homeostatic functions. Contains the cerebellum and medulla oblongata.
What is the cerebellum?
- Has a convoluted surface, providing space for the cell bodies of a large number of neurones.
- Co-ordinates voluntary tasks requiring fine muscle control, eg writing and playing scales rapidly, and controls the muscles to maintain posture.
What is the medulla oblongata?
Connects to the spinal cord, controls basic functions including ventilation, maintaining blood pressure and balance and regulation of heart beat.
What is the midbrain?
Contains nerve fibres linking the hindbrain and the forebrain, that relay information for vision and hearing.
What is the forebrain?
Contains the limbic system and the cerebrum.
What is the limbic system and what does it contain?
- Associated with emotion, learning and memory.
- Contains the hippocampus, thalamus and hypothalamus.
What is the hippocampus?
Interacts with the cerebral cortex, contributing to learning, reasoning, personality and consolidating memory into a permanent store.
What is the thalamus?
A relay centre, sending and receiving impulses to and from the cerebrum.
What is the hypothalamus?
- Controls general functions eg body temperature, blood solute concentration, hunger, thirst and sleep.
- Main controlling region of the autonomic nervous system and links the brain to the endocrine system through the pituitary gland.
What is the cerebrum?
Two hemispheres responsible for integrating sensory functions and initiating voluntary motor functions eg learning, reasoning, personality and memory. Most of it’s functioning is subconscious. It is more developed than other animals.
What is the autonomic nervous system?
It is a part of the peripheral nervous system and controls the continuous functioning of internal organs without conscious intervention by the antagonistic activity of the sympathetic and parasympathetic nervous systems.
The processes it controls are sometimes described as being automatic and include reflex actions such as swallowing, coughing, vomiting and sneezing.
What is the autonomic nervous system regulated by?
It is regulated by the hypothalamus and there are two antagonistic components.
What is the sympathetic nervous system?
It uses the neurotransmitter noradrenalin. This acts in a similar fashion to adrenalin, and so the sympathetic nervous system is excitatory. Its nervous impulses increases heart rate, blood pressure and ventilation rate. The cell bodies of the sympathetic neurones are in the grey matter of the spinal cord and the ganglions lying outside of the spinal cord.
What is the parasympathetic nervous system?
It uses the neurotransmitter acetylcholine. It generally has an inhibitory effect, decreasing the heart rate, blood pressure and ventilation rate. The cell bodies of the parasympathetic neurones are in the brain and spinal cord and others lie close to the target organs.
What happens when blood pressure increases?
An increase in blood pH or blood pressure increases the heart rate. These responses are under automatic control by the cardiovascular centre in the medulla oblongata.
What happens to the heart rate during exercise?
- The cardio-acceleratory centre is stimulated.
- Nervous impulses travel along the sympathetic nerve fibres to the sino-atrial node (SAN).
- The neurotransmitter noradrenalin is released.
- Noradrenalin binds to the cell membrane receptros on SAN cells.
- The SAN’s electrical discharge increases in frequency.
- The heart rate increases.
What happens to the heart rate during sleep?
- The cardio-inhibitory centre is stimulated.
- Nervous impulses travel along the parasympathetic nerve fibres to the SAN.
- The neurotransmitter acetylcholine is released.
- Acetylcholine binds to cell membrane receptors on SAN cells.
- The SAN’s electrical discharge decreases in frequency.
- The heart rate decreases.
What are the two cerebrum hemispheres connected by?
They are connected by fibres which run through the corpus callosum which is the largest white matter structure in the brain.
The structure of the corpus callosum may explain why some parts of the brain are lateralised, which means that they appear to function somewhat differently in the two hemispheres.
