Nervous System Flashcards
1
Q
Describe the structure of the peripheral NS
A
- 12 pairs of cranial nerves
- 13 spinal nerves
- ganglion
2
Q
Define a ganglion
A
a knot-like swelling in a nerve where neurone cell bodies are concentrated
3
Q
What makes up the central nervous system ?
A
brain & spinal cord
4
Q
What are the 2 types of cells in the nervous system ?
A
- neurons
- supporting cells
5
Q
What makes up the autonomic division of the peripheral NS?
A
- Sympathetic & parasympathetic
6
Q
Describe a neuron
A
- functional unit of the NS
- properties = excitability, conductivity & secretions
7
Q
Describe the cell body of nervous tissue
A
- contains a nucleus surrounded by cytoplasm
- contains typical cellular organelles
8
Q
What are neurofibrils ?
A
- composed of bundles of intermediate filaments
- provides the cell shape & support
- also made up one microtubules which asset in moving material between the cell body & axon
9
Q
Describe Lipofuscin
A
a pigment that occurs as clumps of yellowish brown granules in the cytoplasm
10
Q
What are Nissl Bodies ?
A
free ribosomes and prominent closures of RER in the neuronal cell bodies
11
Q
What are the variations of neuron structure ?
A
- multipolar
- unipolar
- bipolar
- anaxonic
12
Q
What are the 3 functional classes of neurones ?
A
- sensory (PNS)
- motor (PNS)
- interneurons (CNS)
13
Q
What are the supportive cells in the nervous system ?
A
- astrocytes
- oligodendrocytes-myelin (CNS)
- Ependymal cells
- microglial cells
- Schwann & Satellite cells (only PNS)
14
Q
What are the 2 types of astrocytes ?
A
protoplasmic & fibrous
15
Q
Define protoplasmic astrocytes
A
have many short branching processes and are found in grey matter
16
Q
Describe fibrous astrocytes
A
they have many long unbranched processes and are located mainly in the white matter
17
Q
Describe astrocytes
A
- contain microfilaments that give them considerable strength, allowing them to support neurons
- regulates the extracellular space & ion conc.
- may play a role in learning and memory by influence the formation of neural synapses
18
Q
Describe microglia
A
- function as phagocytes - removes microbes & damaged nervous tissue
- they remove cellular debris formed during normal development of the NS
- 10% of total brain cell population
19
Q
Describe oligodendrocytes
A
- looks similar to astrocytes due to their projections
- involved in forming & maintain the myelin sheath around CNS axons
- a single oligodendrocyte myelinates several axons
20
Q
Describe Ependymal cells
A
- these cells line the ventricles of the brain & central canal of the spinal cord
- cuboidal to columnar cells arranged in a single layer that possess microvilli and cilia
- produce & assist in the circulation of cerebrospinal fluid
21
Q
Describe Schwann Cells
A
- they encircle the PNS axons, form the myelin sheath around the axons
- 1 Schwann cells myelinates 1 axon
- participates in axon regeneration
22
Q
Describe satellite cells
A
- flat cells that surround the cell Bodie of neurons of PNS ganglia
- provides structural support
- regulates the exchanges of materials between neuronal cells bodies and interstitial fluid
23
Q
What are the gaps in the myelin sheath called ?
A
nodes of ranvier
24
Q
Define graded potentials
A
used for short distance communication only
24
What are the steps in sensory transduction ?
- stimulus
- receptor
- change in ionic permeability or afferent nerve
- generation of action potential
- propagation of action potential
- integration of information by CNS
25
Define action potentials
allows communication over long distance within the body
26
What is the electrical potential difference termed ?
resting membrane potential
27
Describe Ion channels
- allows the diffusion of ions like K+ & Na+
- some ion channel are gated = they only allow flow following certain stimuli
- maintains the resting membrane potential of the cell
28
Describe a ligand-gated channel
Opens & closes in repose to a specific chemical stimulus, such as acetylcholine/neurotransmitters/hormones
29
Describe a mechanically gated channel
It opens/closed in response to mechanical stimulation in the form of vibration, touch, pressure or tissue stretching
- the force distorts the channel from its resting position, opening the gate
30
Describe a voltage-gated channel
Opens in response to a change in membrane potential
- voltage-gated channels participate in the generation & conduction of action potentials
31
Why does the resting membrane potential exist ?
because of a small build-up of negative ions in the cytosol along the inside of the membrane, and an equal build-up of positive ions in the extracellular fluid on the outside surface of the membrane
32
The resting membrane potential arises from what 3 major factors ?
1. unequal distribution of ions in the ECF & cytosol
2. inability of most anions to leave the cell
3. electrogenic nature of the Na/K ATPases
33
Describe the unequal distribution of ions in the ECF & cytosol
- extracellular fluid is rich in Na+ and chloride ions (Cl-)
- in cytosol the main cation is K+ and the 2 dominant anions are phosphates attached to molecules, such as 3 phosphates in ATP, and amino acids in proteins
34
Describe the inability of most anions to leave the cell
- most anions inside the cell are not free to leave
- they cannot flow the K+ out of the cell because they're attached to non-diffusible molecules such as ATP & large proteins
35
Describe the electrogenic nature of the Na/K ATPases
- small inward leak of Na+ and outward leak of K+ is offset by the Na+/K+ ATPases (sodium-potassium pumps)
- these pumps remove more positive charges from the cell than they bring it
- they are electrogenic = they contribute to the negativity of the resting membrane potential
36
Describe a graded potential
- small devotion from the membrane potential that makes the membrane either more polarised or less polarised
37
Define hyperpolarising graded potential
- when a response makes the membrane more polarised (inside is more negative)
38
Define a depolarising graded potential
when a repose makes the membrane less polarised (inside is less negative)
39
When do graded potentials occur ?
when a stimulus causes mechanically gated or ligand-gated channels to open or close in an excitable cell's plasma membrane
40
What does the amplitude of a graded potential depend on?
- stimulus strength
- the greater the stimuli strength, the larger the amplitude of the graded potential
41
Define an action potential
A sequence of rapidly occurring events that decrease and reverse the membrane potential and then eventually restored it to the resting state
42
What are the 2 main phases of an action potential ?
1. depolarising
2. depolarising
43
What occurs in the depolarising phase ?
- when the membrane potential of axon reaches threshold, the Na+ channel activation gates open
- As Na+ ions move through these changes into the neuron, a build up of positive charges form along inside surface of membrane and the membrane becomes depolarised
44
What occurs during the repolarisation phase ?
- Na+ channel inactivation gates close and the K+ channels open
- the membrane starts to become repolarised as some K+ ions leave the neuron and a few negative charges begin to build-up along the inside surface of the membrane
- K+ outflow continues, more negative charge builds along the inside surface of the membrane
- K+ outflow eventually restores the resting potential
- Na+ channel inactivation gates open
- returns to resting state when K+ gates close
45
What occurs during the resting state ?
- all voltage-gated Na+ and K+ channels are closed
- the axon plasma membrane is at resting membrane potential
- small build-up of negative charges along the inside surface of the membrane, and an equal build-up of positive charges along the outside surface of the membrane
46
Define Propagation
- conduction of action potentials across larger distances in the body
47
Describe what occurs at a chemical synapse
- nerve impulse arrives at a synaptic end build of a presynaptic axon
- depolarising phase opens voltage-gated Ca2+ channels
- Ca2+ flows inward through the opened channels
- increase in Ca2+ inside presynaptic neuron triggers exocytosis of the vesicles
- neurotransmitters diffuse across cleft & bind to receptors on postsynaptic neuron plasma membrane
- binding triggers opening of ligand-gated channels
- ions flow through opened channels chaining the voltage --> post synaptic potential
48
Describe a excitatory postsynaptic potential
- a neurotransmitter that depolarises the post synaptic membrane is excitatory as it brings the membrane closer to threshold
49
Describe an inhibitory postsynaptic potential
a neurotransmitter that causes hyper polarisation is inhibitory
- generation of action potential is more difficult as the membrane potential is more negative and thus even further from threshold
50
What are the 3 layers of the meninges ?
Dura mater, arachnoid & pia mater
51
What are the 5 lobes of the cerebellum ?
frontal, insula, parietal, occipital, temporal
52
What are the key functions of the frontal lobe ?
- abstract thought
- mood
- explicit memory
- decision making
53
What are the key features of the insular lobe ?
- taste
- pain
- visceral sensation
- consciousness
54
What are the key functions of the parietal lobe?
- somatic sensation
- sensory integration
- language processing
55
What are the key functions of the Occipital lobe ?
visual awareness & processing
56
What are the key functions of the temporal lobe ?
- hearing
- smell
- emotion
- learning
- verbal memory
57
What is the homunculus ?
a cortical homunculus is a distorted representation of the human body, based on the neurological 'map' of areas and proportions of the brain dedicated to processing motor functions and/or sensory functions
58
Left hemisphere functions
- specialised for spoken & written language
- sequential & analytical reasoning
- breaks info into fragments & analyses
59
Right hemisphere functions
- perceives information in a more integrated way
- seat of imagination & insight
- musical & artistic skill
- comparison of sights, sounds, smells and tastes
60
What are the functions of the spinal cord ?
conduction, neural integration, locomotion, reflexes
61
Describe the role of the cerebellum in motor control
- maintains muscel tone & posture
- coordinates eye & body movements
- coordinates motions of different joints with each other
- aids in learning motor skills
- lesions on the cerebellum can cause ataxia (clumsy gait)
