Flashcards in Chapter 6 - The Central Nervous System Deck (53):
What makes up the Central Nervous System (CNS)?
The brain and the spinal cord.
Where are incoming messages processed and outgoing messages intimated?
The central nervous system (CNS).
What structures protect the CNS?
• membranes called meninges
• a fluid called cerebrospinal fluid (CSF)
What protects the brain?
What opening in the vertebrae does the spinal cord run thorough?
The vertebral canal.
What are meninges?
Membranes that are formed by 3 layers of connective tissues which covers the surface of the brain and the spinal cord. They cover the entire CNS.
Describe the structure of the outer meningeal layer.
It is tough and fibrous. It sticks closely to the bones of the skull but on the inside of the vertebral canal it is not so close fitting. Texture and thickness similar to a household rubber glove.
Describe the structure of the middle meningeal layer.
It is a loose mesh of fibres, while the inner layer is far more delicate. It contains many blood vessels and sticks closely to the surface of the brain and spinal cord.
What is Cerebrospinal Fluid (CSF)?
It is a clear, watery fluid containing a few cells and some glucose, protein, urea and salts.
Describe the structure of the CSF.
It is the 3rd protective structure which occupies a space between the middle and inner layers of meninges. It also circulates through cavities in both the brain and canal in the centre of the spinal cord.
What is the protective role of the CSF?
It acts as a shock absorber, cushioning any blows or shocks the CNS may sustain.
How does the CSF support the brain?
The CSF is formed from the blood and it circulates around through the CNS eventually re-entering the blood capillaries. During it's circulation it takes nutrients to the cells of the brain and spinal cord and carries away their wastes.
What's the 3 main functions if the CSF?
What are the major parts of the brain?
• Medulla Oblongata
Which is the biggest part of the brain?
Explain the structure of the Cerebrum.
It consist of:
• Outer Surface; Cerebral Cortex (grey matter)
• Deep inside; Basal Ganglia (grey matter)
Why did the cortex contain 70% of all neurons in the CNS?
Because the cerebral cortex is folded in patterns that greatly increase it's surface area.
Explain the folding structure of the cerebral cortex.
Folding produces rounded ridges called convolutions (gyri; gyrus- single). The convolutions are separated either by shallow downfolds called sulci (sulcus) or deep downfolds called fissures.
What is the deepest fissure called?
The longitudinal fissure; which almost separated the cerebrum into 2 halves- the left and right cerebral hemispheres.
What is at the base of the longitudinal fissure?
An area of white matter consisting of a large bundle of transverse fibres.
What 4 lobes do certain fissures and sulci further subdivide the cerebral hemisphere into?
• parietal lobes
What does the white matter in between the cerebral cortex and basal ganglia compose of?
Bundles of Myelinated fibres.
What are nerve fibres called within the CNS bundles?
Tracts. (Outside the CSN they are called nerves).
What 3 types of tracts occur in the white matter?
1. Connect various areas of the cortex within the same hemisphere.
2. Carry impulses between left and right hemispheres
3. Connect the cortex to other parts of the brain or to the spinal cord.
What are some ways that scientists have used to find out what various parts of the cerebral cortex do?
• studied brain waves
• electrically stimulate specific areas and observed the responses
• examined changes in cerebral blood flow during different forms of physical or mental activity.
• observed the effects on people of brain damage and/or other diseases.
• experimented on other mammals.
How do scientists study brain waves?
Changes in voltage that occur in the cerebral cortex - which are detected by electrodes attached to the scalp and recorded as an electroencephalogram (EEG).
What are the 3 types of functional area in the cortex?
1. Sensory areas - interpret impulses from receptors.
2. Motor areas - control muscular movements.
3. Association areas - intellectual and emotional processes.
What do the masses of grey matter inside each hemisphere consist of ?
Groups of nerve cell bodies associated with control of skeletal muscles.
What is one of the important functions of the cerebrum?
Memory; memories are not stored in individual memory cells in the brain: they are pathways of nerve cells.
How is memory stored?
When a memory is stored, new links are made between neurons of existing links are modified.
What is the second largest part of the brain?
Describe the structure of the Cerebellum.
Its surface is folded into a series if parallel ridges. The outer folded part of the cerebellum is grey matter. Inside is a white matter that branches to all parts of the cerebellum, rather like the branches of a tree.
What does the cerebellum control?
• fine coordination of voluntary muscle movement.
How do the cerebellum carry out its main functions?
It has to receive sensory information from the inner ear (for posture and balance) and from stretch receptors in the skeletal muscles.
Where do all the functions if the cerebellum take place?
Below the conscious level.
Can we still move without our cerebellum?
Yes because impulses do not originate in the cerebellum but our movements would be spasmodic, jerky and uncontrolled. (Writing, typing, etc will be impossible)
Where is the hypothalamus located?
It lies in the middle of the brain and cannot be seen from the outside.
What is the main function of the hypothalamus.
Homeostasis (maintaining a constant environment for the cells).
Functions of the hypothalamus include the regulation of:
• the autonomic nervous system
• body temperature
• food and water intake
• patterns of waking and sleeping
• the contraction of the urinary bladder
• emotional responses
• secretion of hormones and coordination of parts of the endocrine system
What does the autonomic nervous system include?
• heart rate
• blood pressure
• secretion of digestive juices
• movements of the alimentary canal
• diameter of the pupil of the eye
Why wouldn't we be able to Pee without our hypothalamus?
One of the functions if the hypothalamus include the regulation of the contraction if the urinary bladder.
The secretion of hormones and coordination of the endocrine system acts through:
The pituitary gland, the hypothalamus regulates metabolism, growth , reproduction and responses to stress.
Describe the structure of the medulla Oblongata.
• continuation of the spinal cord.
• about 3cm long.
• extends from just above the point where the spinal cord enters the skull.
What is the important role if the medulla?
It automatically adjusts body functions.
What does the medulla Oblongata contain?
• cardiac centre - regulated the rate and force of heartbeat.
• respiratory centre - control rate and depth of breathing.
• vasomotor centre - regulates the diameter of blood vessels.
•reflexes of swallowing, sneezing, coughing and vomiting.
Does the medulla Oblongata work alone?
No, the medulla Oblongata are influenced and controlled by higher centers in the brain, particularly the hypothalamus.
Describe the structure of the spinal cord.
It is a roughly cylindrical structure that extends from the Foramen magnum, the large opening at the base of the skull, to the second lumbar vertebra, which is about waist level. It is about 44cm in length.
What acts as a pudding around the spinal cord and also allows the cord to bend when the spine is bent?
A space which contains fat, connective tissue and blood vessels.
Where is the central canal located?
It is located in the grey matter which is roughly in the shape of a letter H; in the cross-bar of the H which is a small space.
How are the myelinated nerve fibres of the white matter arranged in?
Bundles known as ascending and descending tracts.
What is the function of the Ascending tracts?
Sensory axons that carry impulses upwards, towards the brain.
What is the function of the Descending tracts?
Contains motor axons that conduct impulses downwards, away from the brain.