Nervous System 1 Flashcards
What does the nervous system do?
Coordinates all body systems and activities, detects and responds to stimuli, brain and spinal cord act as switching centres and nerves and tracts carry messages to and from centres.
What are functional (transmitting) cells called?
Nuerons and are 20%
What are supporting cells called?
Nueroglia and are 80%
What makes up the Central nervous system?
Brain and spinal cord
What makes up the peripheral nervous system?
Cranial nerves (carry impulses to and from brain) and spinal nerves (carry messages to and from spinal cord)
What are the characteristics of nueroglia?
Known as glial cells, support and protection roles, can derive from ectoderm of foetus,out number nuerons 5-10x and non excitable
What are the 4 types of nueroglia in the CNS with function?
Astrocytes (brace and anchor nuerons and capillaries, guide new nerves, mop up nuerotransmitters, influence information processing), Microglial (monitor nerve health and when nerve is sick migrate there and phagocytise them), Ependymal (line the fluid filled cavities of CNA, permeable to CSF pushing it around with cillia) and Oligodendrocytes (form myelin sheaths around nerve fibres in CNS)
What are the 2 types of nueroglia in PNS?
Satellies (surround cell bodies through true task) and Schwann cellls (myelinating cells that also wrap around to insulate signal)
What are the characteristics of nuerons?
Conduct nerve impulses from 1 unit of body to another, highly excitable, long living (100 years), cannot divide, high metabolic rate, basic information processing units of nervous system
What is the structure of a nueron?
Have a cell body with nucleus, axon, dendrites, myelin sheath, nodes of ranvier
What are neurites and where are they?
Ones that carry impulses away from cell body are called axons and ones that recieve impulses are dendrites. They are projections extending from the cell body
What is a sensory nueron?
An afferent nueron and conduct impulses to spinal cord/brain
What is a motor nueron?
An efferent nueron and conducts impulses to muscles/glands
What is an internueron?
Central nuerons that conduct information within CNS
What is the structure of a nerve(4 layers)?
Epineurium (protective sheath, surrounds nerve), Ganglion (cluster of nueron cell bodies), Fascicle (bundle of axons) and Perineurium (CT sheath surrounds each fascicle of nerve fibres in a peripheral nerve)
What is myelin?
Whitish fatty material that has a waxy appearance and covers most long nerve fibres. It protects and insulates fibres and increases the transmission rate of nerve impulses. No myelin=slower signal.
What are axons in the PNS myelinated by?
Schwann cells that wrap themselves tightly around axon which then encloses axon.
What are nodes of ranvier?
The gaps or indentations along the axon due to the Schwann cells.
What forms myelin sheath in CNS?
Oligodendrocytes which lack a neurilemma
What is nuerilemma?
Part of a Schwann cell external to myelin sheath which is nucleus and cytoplasm
Can CNS or PNS regenerate due to nuerilemma?
The PNS can regenerate as the nuerilemma stays intact when nerve is damaged. CNS can not regenerate
What are small collections of cell bodies called?
Ganglia which are found in the PNS
What does white and grey matter refer to?
White is dense collections of myelinated fibres and grey is mostly unmyelinated fibres
What is a synapse?
The axons branch at their terminal end. These axons transmit impulses which reach the axonal terminals and release nuerotransmitters into the space. The tiny gap that seperates the nuerons is called a synaptic cleft and this function works by diffusion and is called synapse
What occurs when there is a disruption of synaptic communication?
Diseases of the brain and psychiatric disorders
Where are nuerotransmitters found and what do they do?
It is stored in the end bulbs in small membranes enclosed sacs called synaptic vesicles. When the vesicle arrives the impulse causes an influx of calcium allowing the nuerotransmitter to diffuse across cleft and bind. The enzymes can then break down transmitter or its reused into the presynaptic terminal. Only one was conduction
What are the 5 types of chemical nuerotransmitters?
Class 1, Class 2, Class 3, Class 4 and Class 5
What are the chemical nuerotransmitters in class 1 and where are they found?
Acetylcholine and found in Cns and PNS in muscles
What are the chemical nuerotransmitters in class 2 and where are they found?
Norepinephrine (NE)- feel good and in CNS(limbic), and PNS; SNS excite
Dopamine- fine motor/feel good and in CNS and PNS
Seratonin- sleep wake and other parasympathic functions and in CNS
Histamine- vasodilation and acute inflammatory and in CNS
What are the chemical nuerotransmitters in class 3(purines) and where are they found?
ATP and Adenosine and in the CNS and PNS
What are the chemical nuerotransmitters in class 4 (aminos) and where are they found?
GABA- main inhibitory nuerotransmitter and in CNS
Glutamate-learning and in CNS
Glycine- spinal cord inhibitory and in CNS
What are the chemical nuerotransmitters in class 5 (peptides) and where are they found?
Endorphins- opiate and in CNS
Substance P-pain mediator and in CNS and PNS
Somastatin-growth hormone inhibitor and in CNS
What are the 4 major regions of the brain?
Cerebral Hemispheres, Diencephalon, Brain stem and Cerebellum
What are the ridges and the grooves of the brain called?
Ridges are gyri and grooves are called sulci
What are the deeper grooves of the brain called and what do they do?
They are called fissures and separate large regions of the brain
What are the cerebral hemispheres separated by>
A single deep fissure called the longitudinal fissure
What is the function of the cerebral cortex?
Head injury but more specifically speech, memory, logical and emotional response, consciouness, interpretation of sensation and voluntary movement
What are the major structures of the diencephalon and where is it located?
It sits atop brain stem and includes the thalamus, hypothalamus and epithalamus
What is the function of the thalamus?
Encloses third ventricle of brain and relay station for sensory impulses passing upwards to sensory cortex. Tells you if sensation will be pleasant or unpleasant by the nuerons of sensory cortex
What is the function of the hypothalamus?
An autonomic nervous system centre and regulates body temperature, water balance and metabolism. Also centre for many drives/emotions ie thirst, appetite, sex, pain and pleasure
Where is the pituitary gland located?
Hangs from anterior floor of hypothalamus by slender stalk and can be accessed via nose
What is the choroid plexus and what does it do?
It is knots of capillaries within each ventricle and forms the cerebrospinal fluid
What are the structures of the brain stem?
The midbrain, pons and medulla oblongata
What is the function of the brain stem?
Forms cranial nerves and controls vital activities ie breathing and blood pressure
What is the function of the midbrain?
Contains reflexes including eyes and ears. The bulging nuclei are reflex centres with vision and hearing but also area of pain supression
What is the function of the pons?
Involved in control of breathing
What is the function of the medulla oblongata and where is it attached to?
Attached to the spinal cord. Contains respiratory, cardiac and vasomotor centres aswells as contralateral control. Controls heart rate, blood pressure, breathing, swallowing, sneezing and vomiting.
What is the function of the cerebellum?
Provides precises timing of skeletal muscle activity and controls balance and equilibrium
What occurs if cerebellum is damaged?
Movements become clumsy and disorganised which is called ataxia. Victims cannot keep balance and appear to be drunk due to loss of muscle coordination and can no longer touch finger to nose with eyes closed
What is the limbic system and what is it involved with?
A functional brain system between cerebrum and diencephalon and is involved in emotional states, behaviour, learning and long term memory
What is the function of the reticular formation(functional brain system) ?
Involved in motor control of visceral organs and special group of nuerons (reticular activating system) deal with consciouness and awake/sleep cycles. Damage to area can result in permanent unconsciouness (coma)
What are the 3 layers of the meninges?
Outer- Dura Mater (strong mother)
Middle- Arachnoid (spider like), CSP weblike
Inner- Pia Mater (gentle mother), delicate CT and small arteries
What is cerebro Spinal fluid?
Is a ‘watery broth’ that is around brain and spinal cord forming a watery cushion that protects the fragile nervous tissues from blows/trauma
Where is the cerebro Spinal fluid formed?
It is formed continuously from blood by choroid plexus
What are choroid plexus?
Clusters of capillaries hanging from roof in each of brains ventricles
What is the blood brain barrier?
The brain needs a constant environment and is selctive for glucose, certain amino acids and electrolytes and blocks everything else but o2, co2, fat, alcohol, nicotine, and anaesthetic
Where is the spinal cord developed from?
The nueral tube
What is the purpose of the spinal cord?
Provides a 2 way conduction pathway to and from brains and is a major reflex centre
Where is the spinal cord extending from and what protects it?
It extends from the foramen magnum of skull to the first/second lumbar vertebrata. It is enclosed within the vertebral column and cushioned and protected by meninges and cerebro spinal fluid
Where can cerebro spinal fluid be removed and why?
Beyond L3, there is no possibility of damaging cord and therefore and ideal spot to remove CSF
How man spinal nerves are there and what are there?
There are 31 pairs Cervical- C1-C8 Thoracic- T1 to T12 Lumbar is L1-L5 Sacral is S1-S5 Coccyx is Co1
What does the grey matter in the spinal cord look like?
It looks like a butterfly or letter H in transverse section
What do the names of white matter tract reflect?
The origin and destination.
