Nervous System Flashcards
(83 cards)
1
Q
What is epithelial tissue?
A
Covers the surface of the body, lines body cavities and forms glands
2
Q
What is connective tissue?
A
Supports, binds and protects other tissues and organs. It also induces blood constituents
3
Q
What is muscle tissue?
A
Main function in contraction
4
Q
What is neural tissue?
A
Transmits electrical and chemical signals to coordinate body functions and responses
5
Q
What are the two types of nervous systems?
A
Central nervous system
Peripheral nervous system
6
Q
What are receptors?
A
Sensory structures that detect changes in the internal and external environment
7
Q
What are effectors?
A
Target organs whose activities change in response to neural commands
8
Q
What are somatic sensory receptors?
A
Provide position, touch, pressure, pain and temperature sensations
9
Q
What are special sensory receptors?
A
Provide sensations of smell, taste, vision, balance and hearing
10
Q
What are visceral sensory receptors?
A
Monitor internal organs
11
Q
What is the autonomic nervous system?
A
Provides automatic regulation of smooth muscle, cardiac muscle, glands and adipose tissue
12
Q
What is the somatic nervous system?
A
Controls skeletal muscle contractions?
13
Q
When is the sympathetic nervous system most active?
A
During periods of stress or physical activity
14
Q
When is the parasympathetic nervous system most active?
A
During periods of rest
15
Q
What is the peripheral nervous system?
A
All the neural tissue outside the CNS. It delivers sensory information to the CNS and carries motor commands to peripheral tissue and organs
16
Q
What is the central nervous system?
A
Responsible for integrating processing and coordinating sensory data and motor commands
17
Q
What are the types of neuron?
A
Sensory neurons
Interneurons on the CNS
Efferent neuron
18
Q
What type of transport moves synaptic vesicles to the synaptic terminal?
A
Axoplasmic transport
19
Q
What are the types of synapses?
A
Synapses with another neuron
Neuromuscular junctions
Neuroglandular synapses
20
Q
What are ependymal cells?
A
Line central canal of the spinal cord and brain ventricles
They help to circulate the cerebrospinal fluid (CSF)
In some areas of the brain they produced CSF and in some other regions they monitor the composition of the CSF
21
Q
What are oligodendrocytes?
A
They myelinate axons from the CNS and provide structural support
22
Q
What are astrocytes?
A
Maintain the blood-brain barrier
Provide structural support
Regulate ions and nutrients
Recycle neurotransmitters
Form scar tissue after injury
23
Q
What are microglia?
A
Remove cell debris, wastes and pathogens by phagocytosis
24
Q
What are ependymal cells?
A
Epithelial cells that line fluid filled passageways within the brain and spinal cord
25
What are microglial cells?
Phagocytes that move through nervous tissue removing unwanted substances
26
What are astrocyte cells?
Star shaped cells with projections that anchor to capillaries
They form the blood brain barrier which isolates the CNS from the general nervous system
27
What are satellite cells?
Surround the cell bodies of neurons
Regulate oxygen
Regulate carbon dioxide
Regulate nutrients
Regulate neurotransmitter levels around neurons
28
What are schwann cells?
Surround all axons in PNS
Responsible for myelination of peripheral axons
Participate in the repair process after injury
29
What is cerebrospinal fluid?
Clear, colourless fluid that is continuously secreted by the choroid plexus
Circulates continuously around the brain and spinal cord
Contains very little protein and no blood cells
30
What are the functions of cerebrospinal fluid?
Delivery of nutrients
Waste clearance
Hydromechanical protection
31
What is the blood-brain barrier?
Protective barrier that separates the brain's interstitial fluid from blood
Isolate the body's main control centre from potentially harmful substances in the blood, and pathogens
32
What is a nerve?
A bundle of neurons' axons, blood vessels and connective tissue
33
What are the cranial nerves?
Olfactory- sensory for smell
Optic- sensory, process visual information
Oculomotor- motor, movement of eyes and smooth muscles controlling pupil and lense
Trochlear- motor, eye movements
Trigeminal- sensory of upper and mid face, lower jaw. Motor muscles or chewing
Abducens- motor, eye movements
Facial- motor for facial expression, tears and salivary glands. Sensory for taste
Vestibulocochlear- sensory, hearing and equilibrium
Glossopharyngeal- motor for mouth and for regulation of blood pressure. Sensory for tongue and pharnyx and outer ear
Vagus- motor for swallowing, speech, cardiovascular and digestive regulation, hunger and fullness. Sensory from visceral, organs and taste. Main parasympathetic nerve
Accessory- swallowing, and head, neck and shoulder movement
Hypoglossal- tongue movements
34
What is the enteric nervous system?
Network of neurons and glia located in the gut wall that is able to control gastrointestinal function independently of the CNS
Enteric neurons receive no direct intervention from the CNS
35
What are the two major ganglionated plexuses of the enteric nervous system?
Myenteric plexuses
Submucosal plexuses
These form a network of neurons and glial cells
Mucosal layer contains delicate nerve and glial networks that dodm the mucosal plexus
36
Can neurons regenerate?
No, they do not have the capacity to divide as they lack centrioles and microtubules
37
Can nerves regenerate?
Yes
38
What is transport like in the brain?
Microtubules important in transport of cargos/vesicles
Microtubules have a plus end and minus end
Two types of motor protein, kinesin and dynein, transport cargos along microtubules
Adaptor proteins help to couple the correct cargo with the right motor protein
Kinesin and dynein move in opposite directions. Dynein moves towards minus end whereas kinesin moves towards the plus end
Orientation of microtubules helps to direct polarised transport
39
How is the motor protein kinesin regulated?
Auto inhibition
40
Where are chemically gated channels most abundant?
Dendrites and cell body of neuron
41
Where are voltage gated channels most abundant?
Axons
42
What are the two ways neurons communicate?
Graded potential
Action potential
43
What is a graded potential?
Change in membrane potential that can have several values and that does not travel far from the area of stimulation because it decreases as it goes
44
Where do graded potentials occur?
Dendrites
Cell body
45
Why in a graded potential the degree of depolarisation lessens with distance?
Cytosol offers resistance to ion movement
Some of the sodium ions entering the cell move back out across the membrane through sodium leak channels
46
How does the membrane potential depend on which ion channel is open?
Opening of Na+ or Ca2+ channels results in a graded depolarisation- excitatory postsynaptic potential (EPSP)
Opening K+ or Cl- channels results in a graded hyperpolarisation- inhibitory postsynaptic potential (IPSP)
47
What is a sub threshold graded potential?
A graded potential starts above threshold at its initial point but decreases in strength as it travels through the cell body
At the trigger zone it is below threshold and hence it cannot initiate an action potential
48
What is a supra threshold graded potential?
A stimulus on the cell body creates a graded potential that is still above threshold by the time it reaches the trigger zone, and an action potential is generated
49
What is temporal summation?
Repeated stimulation of one pre synaptic terminal
50
What are the different types of neural circuits?
Divergence- one neuron sends information to several neurons
Convergence- many neurons influence a single neuron
Parallel after-discharge- signal diverges into multiple parallel pathways and then converges onto a single neuron
Reverberation- signal creates a self sustaining loop of neural activity
51
What is spatial summation?
Simultaneous stimulation of many pre synaptic terminals
52
What are action potentials?
Electrical signals of uniform strength that travel from a neurons trigger zone to the end of its axon
Once the action potential begins it becomes self propagating and can travel long distance along the length of an axon without any decrease in strength
53
What is the all or none principle?
Either the depolarisation reaches threshold and produces an action potential or does not reach threshold and triggers no action potential
54
How is an action formed and then returned back to resting?
Depolarising stimulus
Membrane depolarizes to threshold. Voltage gated Na+ channels open quickly and Na+ enters the cell. Voltage gated K+ begin to open slowly
Rapid Na+ entry depolarises the cell
Na+ channels close and slower K+ channels open
K+ moves from cell to extracellular fluid
K+ channels remain open and additional K+ leaves cell, hyperpolarising it
Voltage gated K+ channels close, less K+ leaks out the cell
Cell returns to resting ion permeability and resting membrane potential
55
What causes the changes in permeability during action potentials?
Voltage gated Na+ and K+ channels
56
What are the two types of gates in the Na+ channels?
Activation gate- opens to allow ions to pass through
Inactivation gate- closes to block the passage of ions
57
What is the refractory period?
Occurs after an action potential, when the membrane is not as excitable
58
What is the absolute refractory period?
Takes place 1-2 msec after the initiation of an action potential
Represents the time required for the Na+ channel gates to reset to their resting positions
During this time an action potential cannot be generated
59
What is the relative refractory period?
It follows the absolute refractory period
Lasts 5-15 msec
During this time as second action potential can be generated but only if a stronger stimulus is used
60
What ensures one way travel of an action potential from the cell body to the axon terminal?
The absolute refractory period
61
What are the two ways action potentials may travel along an axon?
Continuous propagation
Saltatory propagation
62
What is the process of action potentials travelling by continuous propagation?
As an action potential develops at the initial segment, the transmembrane potential at this site depolarises to -30mV
As the sodium ions entering at the initial segment spread away from the open voltage gated channels, a graded depolarisation quickly brings the membrane in the next segment to threshold
An action potential now occurs in this segment of the axon while the previous segement repolarises
This continues along the axon
63
What is the process of action potentials travelling by saltatory propagation?
An action potential has occurred in the initial segment
A local current produces a graded depolarisation that brings the axolemma at the next node to threshold
An action potential now occurs at this node
This repeats for the rest of the nodes of ranvier
64
What is a sensory receptor?
A transducer that converts a stimulus into an intracellular signal
65
What is a simple receptor?
Neurons with free nerve endings
66
What is a complex neural receptor?
Have nerve endings enclosed in connective tissue capsules
67
What are special senses receptors?
Cells that synapse with an afferent neuron
68
What are the categories of sensory neurons based on the location of the stimulus?
Interoceptors- monitor digestive, respiratory, cardiovascular, urinary, and reproductive system. Provide sensations of distention, deep pressure and pain
Exteroceptors- provide information about the external environment in the form of touch, temperature, or pressure sensations, as well as senses of taste, smell, sight, equilibrium and hearing
Proprioceptors- monitor the position and movement of skeletal muscles and joints. Three major groups- muscle spindles, golgi tendons organs, and receptors in joint capsules
69
What are the categories of sensory neurons based on the type of stimulus in which they are most sensitive to?
Chemoreceptors- can detect small changes in the concentration of specific chemicals. They usually only respond to water soluble and lipid soluble substances that are dissolved in body fluids
Nociceptors- pain receptors, sensitive to extremes of temperature, mechanical damage and injury related chemicals. They have free nerve endings with large receptive fields
Thermoreceptors- temperature receptors that are free nerve endings located in the dermis, skeletal muscle, liver, and the hypothalamus
Photoreceptors- converts photons of light into membrane potentials
Mechanoreceptors- sensitive to stimuli that can distort their plasma membrane. They contain mechanically gated ion channels. There are 3 classes- Tactile receptors (detect touch, pressure and vibration. There are 6 types- free nerve endings, root hair plexus, tactile discs, tactile corpuscles, lamellated corpuscles, and ruffin corpuscles), Baroreceptors (detect blood pressure changes), and Proprioceptors (monitor the positions of joints and skeletal muscles)
70
What is a sensory unit?
Single afferent neuron and all receptors associated with it
71
What is an electrical synapse?
The transfer of electrical currents carries by ions through gap junctions
Ions can flow in both directions
Extremely rare in CNS and PNS
72
What is a chemical synapse?
Uses neurotransmitters to carry information from one cell to the next
73
How can neurotransmitters be classified?
Excitatory
Inhibitory
74
Where are neurotransmitters synthesised?
Cell body
Axon terminal
75
What is the most wide spread neurotransmitter and what are the synapses called that release this?
Acetylcholine
Cholinergic synapses
76
What is the process at a cholinergic synapse?
Stimulation for neurotransmitter release is the depolarisation of the synaptic terminal by the arrival of an action potential. Acetylcholine contained in synaptic vesicles
Synaptic terminal briefly opens its voltage gated calcium channels allowing calcium ions to rush in. Calcium triggers exocytosis of acetylcholine into the synaptic cleft. Acetylcholine release stops very soon because Ca2+ is rapidly removed from the cytoplasm
Acetylcholine binds receptors on the post synaptic neuron. Permeability of Na+ increases resulting in depolarisation of the post synaptic membrane. This is a graded potential, it has the ability to become an action potential
Affects of acetylcholine on post synaptic membrane are temporary as acetylcholine is then broken down by enzyme acetylcholinesterase (AChE)
77
How do non neural receptors pass the stimulus to the sensory neuron?
Ribbon synapses
78
What is a reflex?
Rapid automatic response to specific stimuli
79
What are neural reflexes?
Sensory neurons deliver information from the peripheral receptors to the CNS and motor neurons carry motor commands to peripheral effectors
80
What are endocrine reflexes?
Functional counterparts of the neural reflexes that can be triggered only by chemical signals such as hormones
81
What is a reflex arc?
Wiring of a single reflex
82
How can reflexes be classified?
Development- whether it is innate or acquired
Response- whether it is a somatic reflex or a autonomic reflex
Complexity of circuit- whether it is monosynaptic or polysynaptic
Processing site- whether it is processed at spinal cord or brain
83
What is the conectome?
Map of human brain
