Introduction to the nervous system Flashcards
What is the function of the nervous system?
Controls a huge number of organs and processes, both involuntary and voluntary
Abnormality leads to disorder and disease
Important factor in out evolution
Holds the essence to our personalities
Key to humanity
What are the gyrus and sulcus?
Gyrus = raised bits Sulcus = dips in the surface of the brain
What does the parietal lobe control?
Dorsal edge
- motor, sensory, cutaneous and taste
What does the occipital lobe control?
Caudal region
- vision
What does the cerebellum control?
Most caudal point
- coordination, balance, posture
What does the encephalon control?
Most ventral
- breathing, heart rate, blood pressure, swallowing
What does the temporal lobe control?
Dorso-ventral
- hearing and language
What does the frontal lobe control?
Most cephalic/cranial point
- concentration, planning, emotion, creativity
What is the nervous system made of?
NS concerned with the perception of processes that take place inside (enteroreception) or outside the body (exteroreception) and with internal and external communication
Given diversity of the interrelated tasks, the body is involved with a complex NS which can be divided into various categories
- direction and flow of information
- anatomy and morphology
- physiological activities
What is the afferent system?
Nerves that transmit impulses towards the brain and spinal cord
What is the efferent system?
Nerves that transmit impulses away from the brain and spinal cord
How does communication with the rest of the NS outside of the brain/spinal cord occur?
CNS communicates with the rest of the body through cranial nerves and spinal nerves
- BSE (bovine spongiform encephaly) - gets to the brain via the vagus nerve
- rabies - travels through the nerves
What two parts can the nervous system be divided into?
Central nervous system (CNS) - made up of brain + spinal cord the two units are interconnected and a functional unit
Peripheral nervous system
- location of a cell body determines if a cell is in the CNS or the PNS
What does the CNS consist of?
Made up of white and grey matter
- grey matter = nerve cell bodies
- white matter = nerve cell processes (axons) and the insulating myelin sheaths
What is the peripheral nervous system made up of?
Cranial nerves
Spinal nerves
Ganglia
- typical peripheral nerve carries both afferent and efferent fibres and therefore referred to as a mixed nerve , not the case for cranial nerves e.g. optic nerve is purely afferent
Afferent and efferent fibres maybe myelinated or unmyelinated
Cell bodies of PNS lie within a ganglia
What is the ventricular system?
System of cavities (ventricles) within the CNS - has ependymal cells that secrete cerebrospinal fluid (CSF) from choroid plexus
CSF made from the ultrafiltration of blood
- contains: glucose, minerals and provides nutrition to CNS - provides support and shock protection
Physiologically, what is the nervous system divided into?
- Somatic (voluntary) - coordinates voluntary activities like movement inc. reflexes
- Visceral (autonomic) - responsible for involuntary activity such as modulation of cardiac function and digestion
What is a monosynaptic reflex?
Direct communication between sensory and motor neurone
What is a poly-synaptic reflex?
Interneuron facilitates sensory-motor communication
What is a neurone?
Functional unit of the nervous system
Consists of body cell (soma) from which two fundamentally different processes arise
These processes are:
- dendrites: also called receptor segment - conduct electric impulses to the cell body
- axons or nerve fibres: axon relays electrical impulses away from the cell body, Each neurone has one axon
- axons can also be myelinated or un- myelinated
What is the basic structure of a neurone?
In the receptor segment: soma, dendrite, axon hillock and the axon
In the transmission segment: axon: +/- myelin sheath
In the terminal segment: presynaptic terminal (bouton)
What are the three basic neurone types?
Pseudounipolar - dendrites and axon not separated by cell body (e.g. cell in the dorsal root ganglion)
Bipolar neurone - dendrites aborises in the periphary (e.g. in the retina)
Multipolar neurone - multiple dendrites with short or long axons
What is the synapse?
Function connections between two neurones or between neurone and effector organ such as a muscle
Wha is the synapse made up of?
Presynaptic membrane
Synaptic cleft
Postsynaptic membrane
Vesicles in the presynaptic expansion contain neurotransmitter which is released into the synaptic cleft when an axon fires, can inhibitory or excitatory neurotransmitters released at synapase
Neurotransmitters are then taken back up at the post-synaptic membrane by receptors
What is bipolar disorder?
Neurotransmitter dysregulation
What are non-neuronal cells?
Neuroglia: different cell types, surround and provide neurones with structural and functional support e.g. astrocytes and oligodendrocytes
What is the function of neuroglia?
Absorb excess neurotransmitter e.g. astrocytes
Provide immune response e.g. microglia and astrocytes
Contribute to barriers e.g. astrocytes and ependymal cells
Constitute majority of cells in CNS
Capable of mitotic activity - hence can be a source of brain tumours
What is the role of the myelination of axons?
Myelin insulate axon electronically
Increase nerve conduction velocity due to saltatory effect
Schwann cells myelinate axons in PNS
Oligodendrocytes myelinate individual axons in CNS
- has significant clinical relevance in multiple sclerosis where the oligodendrocytes are destroyed whilst schwann cells are okay
How is the brain protected from external trauma?
Shielded from external injury by the cranium and vertebrate
External to the CNS are the meninges which provides further protection
CSF is a shock absorber and baths the brain
BBB prevents unwanted blood contents passing into the CSF
How is the BBB (blood brain barrier) formed?
Astrocytes prevent direct entry to neuron
Tight junctions
Endothelial cells and astrocytes = blood brain barrier
What is the blood CSF barrier?
Where CSF is made
Everywhere a blood vessel comes into contact with a ventricle or space containing CSF
Tight junctions - only let immune cells through
Most CSF is made in the choroid plexus
What is meningitis?
Inflammation of the meninges
