Nerves, The Brain And Spinal Cord Flashcards
What is myelin?
An insulating layer that surrounds the axons of neurons
What is myelin composed of?
Primarily composed of lipids
What type of axons conduct action potentials quicker?
Myelinated axons
What are the gaps in Myelin called?
Nodes of ranvier
What is saltatory conduction?
When action potentials jump from node to node
What forms myelin in the peripheral system?
Schwann cells
What forms myelin in the central nervous system?
Oligodendrocytes
Name the 3 main structures of neurons
Bipolar
Pseufonipolar
Multipolar
What are the two subdivisions of motor neurons?
Upper motor and lower motor neurons
What are upper motor neurones?
Neurons that transmit information from the brain to lower motor neurones in the brain stem and spinal cord
Considered part of the CNS
What are lower motor neurones?
Neurons within cell bodies in the spinal cord or brain stem whose axons directly innervated skeletal muscle
Considered part of the PNS
What does white matter contain?
The axons of the neurons
What does grey matter contain?
The cell body of the neuron
What are the percentages of grey matter and white matter in the brain?
40% = grey matter
60% = white matter
What are the 3 functions of the nervous system?
Sensory input
Integration/central processing
Motor output
What is the central nervous system?
Brain and spinal cord
What is peripheral nervous system composed of?
All the nerves that branch off from the brain and spine that allow your central nervous system to communicate with the rest of the body
What are neurones?
Nerve cells that respond to stimuli and transmit signals
What are the functions of glial cells?
Provide support, nutrition, insulation and help with transmission in the nervous system
What are the most abundant and versatile glial cells?
Astrocytes
What do Astrocytes do?
Exchange materials between neurons and capillaries
Where are Microglial cells found?
In CNS
What do Microglial cells do?
Act as main source of immune defence against invading microorganisms in the brain and spinal cord
Where are Ependymal cells found?
In cavities in your brain and spinal cord
What do Ependymal cells do?
Create, secrete and circulate cerebrospinal fluid
What do oligodendrocytes do?
Produce and insulate barrier called myelin sheath
What are the only two types of glial cells in the peripheral nervous system?
Satellite cells and Schwann cells
What do satellite cells do?
Surround and support neuron’s cell bodies
What do Schwann cells do?
produce and insulate a barrier called the myelin sheath
What are sensory neurons most commonly?
Unipolar
What are motor neurons most commonly?
Multipolar
What do interneurons do?
Transmit impulses between sensory neurons and motor neurons
What is voltage?
The measure of potential energy generated by separated changes
What do we refer to difference in charges in the body?
Membrane potential
What is current?
The flow of electricity from one point to another
What is the resting membrane potential?
-70mV
What is the overall internal charge of a resting neuron?
Overall negative charge
What do mechanically gated channels open in response to?
The physical stretching of the membrane
What do voltage gated channels open and close in response to?
Changes in membrane potential
What is a synapse?
The meeting point between two neurons
What are the two types of synapses?
Electrical and chemical synapses
How do electrical synapses work?
Send an ion current flowing directly from the cytoplasm of one nerve cell to another through small windows called gap junctions
Why are electrical synapses super fast?
Because the electrical signal is never converted from its pure electrical state to any other kind of signal, the way that it is in a chemical synapse
What is the main advantage of chemical synapses?
They convert the signal in steps from electrical to chemical and back to electrical which allows for different ways to control an impulse
What do excitatory neurotransmitters do?
Depolarise the postsynaptic neuron by making the inside more positive and bringing it closer to its action potential threshold
What do inhibitory neurotransmitters do?
Hyper-polarise the postsynaptic neurone by making the inside more negative
What does the likelihood of postsynaptic developing an action potential depend upon?
The sum of all the excitations and inhibitions in that area
What does serotonin do?
Mainly inhibitory and plays a role in regulating moods appetite, circadian rhythms and sleep
What does dopamine do?
Influences emotion and attention
What does norepinephrine do?
Triggers your fight or flight response, increases your heart rate, primes muscles
What is summation?
The process that determines if an action potential will be generated by the combined effects of excitatory and inhibitory signals
What is spatial summation?
Multiple simultaneous inputs
What is temporal summation?
Repeated inputs
What are the two systems of the nervous system?
Central nervous system and peripheral nervous system
Where is the brain?
The brain lies in the carnival cavity and its continuous with the spinal cord through the foremen magnum at the base of the skull
What are the 4 parts that the brain is divided into?
Brain stem
Cerebellum
Diencephalon
Cerebrum
What are the 3 parts of the brain stem?
Midbrain
Pons
Medulla oblongata
What is the midbrain associated with?
Vision, hearing, motor controls, sleep and wakefulness, alertness and temperature regulation
What is the pons associated with?
Breathing and respiratory rhythm
What does the pons form a bridge between?
The cerebrum and the cerebellum
What centres does the medulla oblongata contain?
Cardiac, respiratory, vomiting and vasomotor
(Deals with autonomic functions of breathing, heart rate and blood pressure as well as the sleep-wake cycle)
Where do descending neurons cross to the opposite side?
In the medulla oblongata
What is the cerebellum responsible for?
Coordination of voluntary movements
Motor-learning
Balance
Emerging evidence in role of learning and attention
Where in the brain contains more neurons than the rest of the brain combined?
Cerebellum
Where is the cerebellum located?
At the back of the brain/posteriorly
What two things does the diencephalon contain?
Thalamus and hypothalamus
What does the hypothalamus do?
Regulates homeostasis through influence on autonomic system and pituitary gland
What is the thalamus’s function?
Principle relay station for sensory input
What are the two hemispheres of the brain divided by?
The longitudinal fissure
What are sulci?
Folds/wrinkles in the brain that the surface of the brain is covered in
What are the two hemispheres of the brain connected by?
Corpus Callosum
What is the Corpus Callosum?
Large bundles in fibres connecting the right and left hemispheres
What does the Corpus Callosum allow?
It allows information to move between the hemispheres
What are the two different parts of the nervous system?
Central nervous system and peripheral nervous system
What is the purpose of myelin?
Myelin acts as insulation on the axons
This allows for quicker conduction of nerve impulses
How is myelin made in the PNS?
Made by Schwann cells
How is myelin made in the CNS?
By oligodendrocytes
What is the role of the upper motor neurons?
Upper motor neurons transmit information from the brain to the lower motor neurons and interneurons in the brain stem and spinal cord
What is the role of the lower motor neurons?
Lower motor neurons are neurons with cell bodies in the spinal cord or brain stem whose axons directly innervate skeletal muscle
What is the difference between grey and white matter?
White matter contains the axons
Grey matters contains the cell bodies
What is an action potential?
Brief depolarisation of the axon caused by a change in currents
Causes a biological change reaching transferring signal down the axon
What are the 2 lobes of the cerebrum called?
Left and right hemisphere
What structure connects the 2 halves of the cerebrum together?
Corpus Callosum
What makes up the diencephalon?
Thalamus and hypothalamus
What is the role of the thalamus?
Thalamus is the sensory relay station
All sensory information synapses here and it helps to control sensory stimulus
What is the role of the hypothalamus?
Hypothalamus is responsible for homeostasis, helps to control hormones, temperature, etc
Where are the basal ganglia located?
Deep within the brain
What are the 5 nuclei of the basal ganglia?
Caudate nucleus
Globes Pallidus
Putamen
Substantia Nigra
Subthalamic nucleus
What is inferior to the cerebrum?
Brain stem and cerebellum
What are the 3 different components of the brainstem?
Midbrain
Pons
Medulla
What vital structures are located in the brainstem?
Control centres for respiration and heart
What is the role of the cerebellum?
Coordination of voluntary movements, motor-learning, balance, emerging evidence in role in learning and attention
What is the name of the skeletal structure that protects the spinal cord?
Vertebral column
Describe the gross structure of the complete spinal cord
Spinal cord is covered in meninges and between meninges and spinal cord is cerebral spinal fluid. The cord does not extend all the way down the vertebral column, it stops at approximately T12/L1 it then becomes the peripheral nerves
Describe the key functions of the spinal cord
Connects the peripheral nerves with the CNS
Transmits sensory information towards the brain and transmits motor information towards the muscles
What is the purpose of the tracts in the spinal cord?
Transmit different information in the spinal cord
What are the main elements of the peripheral nervous system?
Motor and sensory peripheral nerves and the autonomic nervous system
Describe the function of the autonomic nervous system
Control and modulation of particular autonomic and involuntary body systems
What are the three targets that the ANS works on?
Smooth muscle
Cardiac muscle
Glands
Name three mechanisms of peripheral nerve injuries
Crush
Compression
Severed nerve
Name the ascending afferent sensory spinal tracts
Dorsal column
Spinocerebellular tract
Spinothalamic tract
Name the efferent descending motor spinal tracts
Corticospinal tract
Rubrospinal tract
Reticulo spinal tract
Tecctospinal tract
Vestibulo spinal tract
What is the dorsal column responsible for?
Fine touch
2 point discrimination
Vibration
Conscious proprioception
What is the spinothalamic tract responsible for?
Pain
Course touch/pressure
Temperature
What is the spinocerebellar tract responsible for?
Unconscious proprioception
Coordination
What is the tectospinal tract for?
Auditory and visual
Name some causes of a spinal cord injury
Road traffic accidents
Sports related injuries
Spinal stroke
Spinal canal stenosis
Tumour
Inflammation of spinal cord
Viral infection of spinal cord
Development/congenital abnormalities
What symptoms do you get from a complete spinal cord injury?
Complete loss of function below point of injury (motor, sensory, autonomic dysfunction)
