CH 4 NERVOUS SYSTEM IS HIGHLY ORGANISED Flashcards
(39 cards)
2 divisions of NS
CNS - brain, spinal cord
PNS - nerves that connect CNS with receptors, muscles and glands
which structures protect the CNS?
- bone
- membranes called meninges
- cerebrospinal fluid
describe structure/location of cranium and vertebrae
- brain protected by cranium, part of skull that houses brain
- spinal cord runs through vertebral canal, an opening in the vertebrae
- these bones provide a strong, rigid structure to protect structures underneath
describe the 3 meningeal layers
connective tissue forming membranes called meninges
- outer; dura mater; tough and fibrous - layer of protection. sticks closely to bones of the skull, but on inside of vertebral canal it is not close to fitting. texture and thickness similar to a household rubber glove
- middle; arachnoid mater; loose mesh of fibres
- inner; pia mater; far more delicate. contains many blood vessels, sticks closely to surface of brain and spinal cord.
what is cerebrospinal fluid? name its 3 functions.
clear, watery fluid containing a few cells and some glucose, protein, urea, salts. occupies a space between middle and inner meningeal layers, circulates through cavities in brain & through a canal in spinal cord.
- protection: shock absorber cushions blows
- support: brain suspended in cranium
- transport: CSF formed in blood and circulates around through CNS before re-entering blood capillaries. during circulation, it takes nutrients to the cells of the brain and carries away their waste
name 5 main structures of the brain
- corpus callosum
- cerebrum
- hypothalamus
- medulla oblongata
- cerebellum
describe the main features of the cerebrum
biggest part of the brain consists of;
- cerebral cortex
- a deeper layer of white matter
- additional grey matter centre, the basal ganglia.
describe the structure of the cerebral cortex
- outer grey matter layer consists of neuron cell bodies, dendrites, unmyelinated axons.
- folded in patterns, greatly increasing surface area (contains 70% of all neurons in CNS).
- folding produces convolutions (gyri) which are separated by either shallow downfolds (sulci) or deep downfolds (fissures)
what does the longitudinal fissure do?
almost separates the cerebrum into two halves - left and right cerebral hemispheres
- joining the two at the base of the fissure is an area of white matter consisting of a large bundle of traverse fibres; corpus callosum
why is grey matter grey and white matter white?
the fatty nature of myelin gives the white matter its colour and texture. because grey matter contains unmyelinated axons, it doesn’t posses the same pigment, and is therefore grey
name the 5 lobes of the brain and briefly state their functions
frontal lobe: thinking problem solving, emotions, personality, language, control of movement
parietal lobe: processing temperature, touch, taste, pain and movement
temporal lobe: processing memories and linking them with senses; receives auditory information
occipital lobe: vision
insula: recognition of different senses and emotions, addiction and psychiatric disorders (deep inside the brain)
identify the functions of the cerebral cortex
involved with thinking, reasoning, learning, memory, intelligence, sense of responsibility.
perception of the senses and initiation and control of voluntary muscle contraction
name the three main functional areas in which the cerebra cortex can be divided
sensory areas: interpret impulses from receptors
motor areas: send impulses to muscles for control muscular movements
association areas: concerned with intellectual and emotional processes
what physically happens when a memory is stored
memories are not stores in single cells. they are pathways of nerve cells. new links are made between neurons or existing links are modified.
usually, what sorts of specialised functions are controlled by the right and left hemispheres?
left: language ability, voluntary movement on right side of the body
right: musical and artistic abilities, voluntary movement on left side of the body
what are tracts and where do they occur
within the CNS bundles of nerve fibres are called tracts. outside the CNS bundles of nerve fibres are called nerves
3 types occur in the white matter;
- 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 the other parts of the brain or to the spinal cord
briefly explain the structure and function of the basal ganglia
- consists of groups of nerve cell bodies associated with control of skeletal muscles
- which play a role in initiating desired movements and inhibiting unwanted movements
what is the function of the corpus callosum?
- wide band of nerve fibres lies underneath cerebrum at base of longitudinal fissures
- nerve fibres in the corpus callosum cross from one cerebral hemisphere to the other and allow the two halves to communicate with each other
physically describe the cerebrum
- second largest part of the brain
- surface folded into a series of parallel ridges
- lies under the rear part of the cerebrum
- outer folded part is grey matter
- inside is white matter that branches to all parts of the cerebellum
what is the function of the cerebellum?
- control over posture, balance, fine coordination of voluntary muscle movement. to carry out these functions, the cerebellum must receive sensory info from:
- the inner ear for info about posture and balance
- stretch receptors in skeletal muscles for info about the length of muscles
- all functions are under unconscious control
- we can move without it but movements would be jerky and uncontrolled
what are the functions of the hypothalamus?
- maintaining constant internal environment - homeostasis
functions include regulation of: - autonomic nervous system (including regulation of heart rate, blood pressure, secretion of digestive juices, movements of alimentary canal, diameter of pupil in the eye)
- body temp
- food and water intake
- patterns of waking and sleeping
- contraction of urinary bladder
- emotional responses, e.g. fear, anger, aggression, pleasure, contentment
- secretion of hormones and coordination of parts of the endocrine system; acting through pituitary gland, hypothalamus regulates metabolism, growth, reproduction, responses to stress
what is the medulla oblongata and what are its functions?
- continuation of the spinal cord
- extends from point where spinal cord enters the skull
- many nerve fibres pass through medulla going to or from other parts of the brain
- important role in automatically adjusting body functions
what are the 3 ‘centres’ contained in the medulla oblongata?
cardiac centre: regulates rate and force of the heartbeat
respiratory centres: control rate and depth of breathing
vasomotor centre: regulates diameter of blood vessels
- in addition, other centres regulate sneezing, coughing and vomiting. all these centres are controlled by higher centres in the brain, particularly the hypothalamus
how is the spinal cord protected?
- enclosed in vertebral canal (3 meningeal layers)
- dura mater not joined to the bone; instead, a space containing fat connective tissue and blood vessels serves as padding and allows cord to bend when spine is bent
