The central nervous system Flashcards
what makes up CNS and PNS?
CNS :brain and spinal cord
PNS : Nerves make up the peripheral nervous system
How does bones protect CNS?
Bones provide strong, rigid structure to protect the CNS:
Cranium is the part of the skull that protects the brain
Vertebrae protects the spinal cord
How many layers does meninges have?
Three
What is meninges?
Layers of connective tissues forming membranes.
Where can meninges be found?
Found inside the bones, and covering the surface of the brain and spinal cord
What is the outer meningeal layer?
Dura mater
Describe structure of dura mater
Tough and fibrous similar to rubber glove
Where does dura mater located ?
It sticks closely to the skull, but on the inside of the vertebral canal there is a space containing fat
Function of space containing fat, connective tissues and blood vessels
serve as padding & allow the spinal cord to bend
Describe feature of arachnoid mater
Loose mesh of fibres
Where is the arachnoid located?
middle miningeal layer
Describe feature of the Pia mater
Contains many blood vessels & sticks closely to surface of brain and spinal cord
Where is Pia mater located?
the inner meningeal layer
What is cerebrospinal fluid?
Clear, watery fluid containing a few cells and some glucose, protein, urea and salts
What are the functions of cerebrospinal fluid?
Functions:
Protection - shock absorber, cushioning any blows or shocks the CNS may sustain
Supports the brain - brain is suspended inside the cranium and floats in the fluid that surrounds it
Transport - takes nutrients to the cells of the brain and spinal cord and carries away their wastes
What does the CNS consists of ?
The central nervous system consists of:
grey matter - consist of nerve cell bodies, dendrites & unmyelinated fibres.
white matter - composed of myelinated fibres
What are the parts of the brain?
Parts of the brain include: Cerebrum, cerebellum, hypothalamus, medulla oblongata and corpus callosum
Describe cerebrum
Biggest part of the brain
Consists of :
outer surface of grey matter known as the cerebral cortex
grey matter deep inside the cerebrum called basal ganglia
inner white matter
Describe cerebral cortex
The cerebral cortex is greatly folded which increase its surface area for a large number of neurons
Folding produces rounded ridges called convolutions (or gyri; singular gyrus)
How are convolutions separated by ?
shallow downfolds called sulci (singular ‘sulcus’)
deep downfolds called fissures
What is the deepest fissure ?
The longitudinal fissure (deepest fissure) almost split the cerebrum into two halves – the left and right cerebral hemispheres
What are the lobes of cerebrum ?
The lobes of the cerebrum: Frontal lobe Temporal lobe Occipital lobe Parietal lobe Insula (deep inside the brain)
What are the functions of cerebral cortex ?
Functions of the cerebral cortex:
- involved in mental activities such as thinking, reasoning, learning, memory, intelligence and sense of responsibility
- perception of the senses
- the initiation and control of voluntary muscle contraction
What are the three types of functional area in the cortex?
There are three types of functional area in the cortex:
sensory areas, which interpret impulses from receptors
motor areas, which control muscular movements
association areas, which are concerned with intellectual and emotional processes.
What is the association area involved in ?
Memory
How does the association area works?
Memories are not stored in individual memory cells in the brain: they are pathways of nerve cells.
When a memory is stored, new links are made between neurons or existing links are modified.
What is basal ganglia?
Are masses of grey matter inside each hemisphere
What does the basal ganglia consists of ?
Consist of groups of nerve cell bodies associated with control of skeletal muscles
Within the CNS, bundles of nerve fibres are called
tracts
What are the three types of tracts?
- tracts that connect various areas of the cortex within the same hemisphere
- tracts that carry impulses between the left and right hemispheres
- tracts that connect the cortex to other parts of the brain or to the spinal cord.
What are corpus callosum ?
A bundle of nerve fibres that lies underneath the cerebrum at the base of the longitudinal fissure
What is the function of corpus callosum ?
Function: allow the two cerebral hemispheres to communicate with each other
Describe the function of cerebellum
Lies under the rear part of the cerebrum
Its surface is folded into a series of parallel ridges
The outer folded part of the cerebellum is grey matter
Inside is white matter that branches to all parts of the cerebellum
What is the function of cerebellum ?
Functions: control posture, balance and
the fine coordination of voluntary muscle movement
To carry out these functions the cerebellum receives sensory information from:
the inner ear (for posture and balance)
stretch receptors in the skeletal muscles
Are impulses generated by cerebellum ?
All the functions of the cerebellum take place below the conscious level
Impulses do not originate in the cerebellum and so without it we could still move, but our movements would be spasmodic, jerky and uncontrolled.
Where does the hypothalamus located ?
Lies in the middle of the brain & cannot be seen from the outside
What is the function of hypothalamus?
It controls many body activities, but it is mostly concerned with homeostasis
The hypothalamus regulates ?
the autonomic nervous system body temperature food and water intake patterns of waking and sleeping the contraction of the urinary bladder emotional responses the secretion of hormones and coordination of parts of the endocrine system acting through the pituitary gland
Describe medulla oblongata
The medulla oblongata is a continuation of the spinal cord
About 3cm long & extends from just above the point where the spinal cord enters the skull
What does the medulla oblonganta consists of ?
The medulla oblongata contains:
the cardiac centre, which regulates the rate and force of heartbeat
respiratory centres, which control rate and depth of breathing
the vasomotor centre, which regulates the diameter of blood vessels
Who controls all the centre in the medulla oblongata ?
Hypothalamus
Medulla oblongata also regulates ?
the reflexes of swallowing, sneezing, coughing and vomiting
Describe the spinal cord
The spinal cord is a roughly cylindrical structure
It extends from the foramen magnum (opening at the base of the skull) to the second lumbar vertebra
Where does the white and grey matter located in spinal cord?
The grey matter of the spinal cord is at the centre, surrounded by the white matter
The myelinated nerve fibres of the white matter are arranged in bundles called:
Ascending tracts - sensory axons that carry impulses upwards, towards the brain
Descending tracts - motor axons that conduct impulses downwards, away from the brain
Spinal cord functions:
Carry sensory impulses up to the brain & motor impulses down from the brain
integrate certain reflexes (fast, automatic responses)
